Tonight’s Sky – October

The Greater Hazleton Area Astronomical Society

Moon, Mars rendezvous in early October

Posted by Bruce McClure in TONIGHT | October 2, 2020

A telescopic view of the moon's cratered limb, with the red disk of Mars disappearing behind it.

Above photo: Close encounter between the moon and Mars on July 17, 2003, captured by Andrew Chaikin in central Florida. Image via Andrew

In early October 2020, the waning gibbous moon meets with the dazzling red planet Mars. On October 2, look for the glorious evening couple – the moon and Mars – to rise in tandem in your eastern sky around nightfall or early evening. After the brilliant twosome rises, they’ll be out for the rest of the night, traveling westward across the nighttime sky. The moon and Mars climb highest up for the night after midnight, and then sit low in the west as dawn starts to color the October 3.Moon and Mars at early evening.

The moon will move away from Mars to pass to the south of the planet Uranus, and then to the south of the Pleiades star cluster. Most people need binoculars and a moon-free night to see Uranus. Use Mars and a sky chart to help you find Uranus when the moon has left the evening sky. Note: The moon looks larger on the chart than in the real sky.

By the way, if you’re at just the right place worldwide, you can watch the moon occult (cover over) Mars on the night of October 2-3, 2020. We provide more details on this occultation later on in this post.

Mars beams more brilliantly in October 2020 than it will for nearly another 15 years, as the red planet won’t showcase a brighter version of itself until September 2035. The brilliant moon won’t be able to subdue this planet’s luster, as Mars (in October 2020) ranks as the 4th-brightest heavenly body in all the heavens, after the sun, moon and the planet Venus, respectively. In November 2020, however, the king planet Jupiter will reclaim its

There’s no way to mistake Venus for Mars, as Venus is only visible as a morning “star” in the eastern predawn/dawn sky. If you’re an early riser, up before daybreak, note where Mars sits low in the October morning sky. Then turn about-face, and you can’t miss Venus, by far the most brilliant starlike object in the sky. If you’re up before dawn on October 2 or 3, you might even catch Venus’ furtive meeting with Regulus, the brightest star in the constellation Leo the Lion.Conjunction of Venus and Regulus in early October 2020.

From North America, Venus appears about 1/2 degree to the west of (or above) Regulus on October 2, and about 1/2 degree east of (or below) Regulus on October 3. Conjunction comes on October 3, at 0 hours UTC, at which time Venus passes 0.1 degree south of Regulus. Read more.

As the moon makes its monthly rounds in front of the constellations of the zodiac, it sweeps 0.7 degrees south of Mars on October 3, at 3:21 Universal Time. (At U.S. time zones, that converts to October 2, at 11:21 p.m. EDT, 10:21 p.m. CDT, 9:21 p.m. MDT and 8:21 p.m. PDT.

For reference, the moon’s angular diameter spans about 1/2 degree (0.5 degrees). But when an astronomical almanac gives the angular distance between the moon and a planet, it really means the angular distance between the center of the moon and that planet as viewed from the center of the Earth. For the Earth’s surface, the angular separation of the moon will be greater at some places yet less at others.

The farther north you live on the Earth’s surface, the farther south the moon swings from Mars; and the farther south you live, the closer the moon comes to Mars. In fact, if you live in southern South America, you can actually watch the moon occult (cover over) Mars for a portion of the night of October 2-3, 2020. For example from Santa Cruz, Argentina, Mars will disappear behind the moon on October 2, 2020, at 11:18 p.m. local Argentina Time, and Mars will reappear from behind the moon on October 3, 2020, at 12:18 a.m.Worldwide occultation map of the lunar occultation of Mars on October 2-3, 2020.

The swath of the world to the south (below) the white curve (southern South America, Falkland Islands) can see the lunar occultation of Mars on the night of October 2-3, 2020. Click here for occultation times in Universal Time (UTC). You must convert UTC to local time. Here’s how. Worldwide map via IOTA.

Orange Arcturus sparkles after sunset

Posted by Deborah Byrd in TONIGHT | October 4, 2020

Tonight, look for Arcturus, one of three stars noticeable for flashing in colors in the evening sky at this time of year. You should be able to see it in the west at dusk or nightfall. Once it gets good and dark, and you live at mid-to-far latitudes in the Northern Hemisphere, you can verify that this star is Arcturus by using the Big Dipper asterism.

The arc of the Big Dipper handle extended outward always points to Arcturus.

Notice that Arcturus is an orange-colored star.

Every year at this time, we get questions about three different stars that are flashing different colors. One is Arcturus in the constellation Boötes the Herdsman, shining in the west to northwest after sunset. Another is Capella in the constellation Auriga the Charioteer, which is now in the northeast in mid-evening. And the third is Sirius in the constellation Canis Major the Greater Dog, which is now in the south before dawn.

All three appear to be flashing colors for the same reason … all three of these stars are bright and, at this time of year, noticeably low in the sky as seen from Northern Hemisphere locations. When you see an object low in the sky, you’re seeing it through a greater thickness of atmosphere than when it’s overhead. The atmosphere refracts or splits the stars’ light to cause these stars to flash in the colors of the rainbow.

At mid-northern latitudes, scintillating Arcturus adorns the western evening sky all through October.

Giant roiling orange star next to small yellow dot labeled sun.

If they were located at the same distance from us, you’d see that Arcturus is a much, much larger star than our sun. Image via Windows to the Universe

Bottom line: On October evenings, look for the brilliant star Arcturus in the western sky, flashing in colors. You can be sure you’ve identified this yellow-orange star if the handle of the Big Dipper points to it.

Mars closest to Earth October 6

Posted by Bruce McClure in TONIGHT | October 5, 2020

Above photo: Jim Powell caught this image of Mars on the morning of July 15, 2018.

On October 6, 2020, Earth sweeps closer to the red planet Mars than it will again for another 15 years, or until September 2035. At its closest, Mars is about 38.57 million miles (62.07 million km) away on October 6 at 14 hours UTC. For the West Coast of the U.S. and Canada, Mars’ closest approach happens before sunrise October 6, 2020, at 7 a.m. PDT, 6 a.m. Alaskan Time and at 4 a.m. Hawaiian Time.

At their historically close approach in 2003. Mars was closer than it had been in some 60,000 years, and it’s now only slightly farther from Earth now than then. On August 27, 2003, Mars was 34.65 million miles (55.76 million km) distant. Mars won’t beat its 2003 performance until until August 28, 2287, when the red planet will be 34.60 miles (55.69 million km) away

Have you seen Mars yet? You can see it easily with the eye alone as the resplendent red “star” in the east every evening, and in the west before dawn. In fact, dazzling Mars is easily the brightest starlike object to light up the evening sky. Only the planet Venus – the 3rd-brightest celestial object, after the sun and moon – beams brighter than Mars. Yet Mars lords over the nighttime from evening until dawn, whereas Venus is relegated to the eastern morning sky.

Read more: The cycle of close and far Mars oppositions

Red Mars, red moon. Yadi Suryadi in West Java, Indonesia, wrote: “The moon became red when it began to reach the peak of the total lunar eclipse (right), and the red planet Mars around its opposition (left).” Early morning of July 28, 2018.

Mars is closest in spite of the fact that Earth will swing between Mars and the sun, at its opposition on October 13, 2020.

Why aren’t we closest to Mars on the day we pass between it and the sun? If both the Earth and Mars circled the sun in perfect circles, and on the same exact plane, the distance between Earth and Mars would always be least on the day of Mars’ opposition. But we don’t live in such a symmetrical universe. All planets have elliptical orbits and a perihelion (closest point) and aphelion (farthest point) from the sun.

Mars’ orbit around the sun takes 687 days in contrast to 365 days for Earth. It has a year nearly twice as long as ours. Earth’s farthest point from the sun comes yearly, in early July. Mars was at its closest to the sun on March 3, 2020. Ever since July 4, 2020, Earth has been moving closer to the sun; and ever since March 3, 2020, Mars has been edging away from the sun.

At its opposition on October 13 – when Earth will be directly between Mars and the sun – Mars will be farther from than sun than on October 6, 2020. On the other hand, Earth will be closer to the sun (and therefore farther from Mars) on October 13 than on October 6. That all adds up to Earth being slightly closer to Mars on October 6 than October 13.

The time interval between a Mars opposition and its least distance from Earth can be as long as 8.5 days (1969), or as little as 10 minutes (2208 and 2232).

Generally speaking, Mars is at its brightest in 2020 throughout the month of October 2020. It is now shining more brilliantly than the planet Jupiter, and it’s not very often that Mars outshines the king planet!

View larger. | To the eye alone, Mars looks like a bright “star.” On July 24, 2018, in Kalispell, Montana, John Ashley captured the images to make this composite. The bright object here is the moon, and the 2nd-brightest is Mars. You can see Jupiter in the top right, and Saturn just below the moon. Notice Mars is brighter than both Jupiter and Saturn! Read more about this image.

Is Mars brightest when it’s closest? Not necessarily.

You might think Mars should be brighter when closest to Earth on October 6 than at opposition on October 13. But it’s not (although it’s still plenty bright).

Mars is a tiny bit fainter now than it will at its October 13 opposition. That’s because of something known as opposition surge. Mars reflects sunlight most directly back to Earth at opposition. This directness accentuates Mars’ brilliance. Before and after opposition, sunlight is reflected at a slightly slanted angle relative to Earth, thereby reducing Mars’ brightness.

Artist’s concept of the orbits of Earth and Mars, via NASA.

Earth swings between Mars and the sun every other year, at progressively later dates. Earth will next lap Mars on December 8, 2022. Its closest approach to Earth that year will be December 1, 2022. After that, Earth will next lap Mars on January 16, 2025, but its closest approach will come on January 12, 2025. At both of those oppositions of Mars – and at every opposition for some years to come – Mars will appear fainter, and fainter, in our sky. That’s because those oppositions will happen closer and closer to Mars’ aphelion date.

In the year 2027, Mars’ opposition comes on February 19, 2027, and Mars sweeps closest to Earth on February 20, 2929. At a distance of 63.02 million miles (101.42 million km), this will present Mars’s most distant opposition in the 21st century (2001 to 2100). Mars reaches aphelion – it farthest distance from the sun – on March 2, 2027.

So enjoy Mars in October 2020! You won’t see it this bright again until September 2035.

Mars is out almost all night long now. It looks like a bright reddish “star,” shining with a steadier light than the true stars. In mid-October 2020, look for Mars in the east at nightfall – highest in the sky near midnight – and in the west as morning dawn starts to light the sky.

Clouded out tonight? Look tomorrow or the next night! Mars will remain dazzlingly bright in our sky for all of October.

Read more: The cycle of close and far Martian oppositions

Mars will still be visible after July and August, 2018, but each month it will shrink in apparent size as Earth rushes ahead of Mars in our smaller, faster orbit around the sun. As telescopes show Mars smaller in apparent sky, our unaided eyes will see Mars fade in brightness. Image via NASA Tumblr.

Bottom line: The Mars opposition – when Earth flew between the sun and Mars – comes on October 13, 2020. But the distance between Mars and Earth is least on October 6, 2020. You can see Mars easily with the eye alone. It looks like a bright red “star,” in the east every evening, in the west before dawn.

Watch for Draconid meteors in 2020

Posted by Deborah Byrd in TONIGHT | October 7, 2020

Image at top: Draconid meteor seen in 2011 by Frank Martin Ingilæ. Used with permission.

Draco the Dragon is now spitting out meteors, also known as shooting stars. This is one shower that’s best to watch at nightfall or early evening, not after midnight. No matter where you are on Earth, watch as close to nightfall as possible. The shower is active between October 6 and 10. The best evening to watch is likely October 7. This shower favors the Northern Hemisphere, but Southern Hemisphere observers might catch some Draconids, too. Fortunately, the waning gibbous moon won’t rise until mid-to-late evening. Look for these meteors for a few hours, starting at nightfall.

Even at northerly latitudes, the Draconids are typically a very modest shower, offering only a handful of slow-moving meteors per hour. But exceptional displays have taken place over the years. The Draconid meteor shower produced awesome meteor displays in 1933 and 1946, with thousands of meteors per hour seen in those years. European observers saw over 600 meteors per hour in 2011.

Two years ago, in 2018, was also a favorable year because the new moon closely aligned with the peak date of the Draconids. But that’s not all. The Draconids’ parent comet – 21P/Giacobini-Zinner – reached perihelion, its closest point to the sun, in 2018, coming closer to Earth than it had in 72 years.

Those two factors added up to an outburst of Draconids for Europe in 2018. No outburst is expected this year. But meteor showers are notorious for defying the most carefully crafted forecasts. So you never know for sure what’s up in a meteor shower unless you look.

Last quarter moon in Gemini, waning moon in Cancer

Posted by Bruce McClure in TONIGHT | October 9, 2020

Moon travels through the constellation Gemini and Cancer.

Wake up before dawn on the mornings of October 10 and 11, 2020, and let the waning moon show you the zodiacal constellations Gemini and Cancer.

Before midnight October 9, 2020 – or after midnight October 10 – the moon will be rising over your eastern horizon at or near its half-illuminated last quarter phase. It’ll be shining in front of the constellation Gemini the Twins. If you’re more of an early bird than a night owl, get up before dawn to view the moon and Gemini much higher up in the sky. To the north of the moon will be Gemini’s two brightest stars, Castor and Pollux. The other bright star beaming to the south of the moon will be Procyon, the Little Dog Star.

The moon’s exact last quarter phase comes on October 10, 2020, at 0:39 UTC. Although the last quarter moon occurs at the same instant worldwide, the local clock time – and possibly the date – differ by time zone. Depending on where you live worldwide, the last quarter moon falls on October 9 or 10.A star map of the constellation Gemini issued by the International Astronomical Union.

The constellation Gemini via the IAU. Every year, the sun passes in front of this constellation from about June 21 to July 20.

Although the sky chart at the top of this page is designed for temperate latitudes in North America, you’ll see the moon passing through the same region of the starry sky from all parts of Earth. The moon moves in front of the constellations of the zodiac at the rate of about 1/2 degree (the moon’s own angular diameter) eastward per hour. So – for example – if you’re in the world’s Eastern Hemisphere at dawn on October 10 and 11, you’ll see the moon offset a bit, with respect to our chart, toward the previous date.

The lit side of a waning moon always points eastward – the moon’s direction of travel – in front of the backdrop stars of the zodiac. On the morning of October 10, from around the world, the moon’s daytime side will be pointing at the hidden treasure at the heart of the constellation Cancer the Crab: a star cluster known as Messier 44, or M44, aka the famous Beehive. Then, on October 11, the moon will sweep 2.1 degrees north of the Beehive at 12:27 UTC.

Click here to know the moon’s present position in front the constellations of the zodiac.

The constellation Cancer via the IAU. On a dark night, look for the Beehive star cluster (M44) to make a triangle with the Gemini stars, Castor and Pollux, and the bright star Procyon.

As seen from North America on the morning of October 11, the moon will meet up with the Beehive at 8:27 a.m. EDT, 7:27 a.m. CDT, 6:27 a.m. MDT and 5:27 a.m. PDT. Cancer makes up for its lackluster stars by sporting one of the most magnificent star clusters in all the heavens. On a dark night – with no moon – this cluster appears as a tiny faint cloud to the unaided eye. Through binoculars, this bit of haze explodes into a sparkling array of stars.

Bottom line: Last quarter moon comes on October 10, 2020. That morning, the moon will be in front of Gemini the Twins. The next morning – October 11 – the moon will be in front of Cancer the Crab.

Moon, Venus, Regulus October 12 to 15

Posted by Bruce McClure in TONIGHT | October 11, 2020

Moon, Venus and Regulus adorn the eastern predawn/dawn sky.

What better way to start out the day than to enjoy the waning crescent moon and dazzling planet Venus before sunrise? You might also spot Regulus, the brightest star in the constellation Leo the Lion, up before the sun. Although Regulus is a 1st-magnitude star, or one of the brightest stars in our sky, Leo’s brightest star pales next to Venus. Brilliant Venus outshines Regulus by well over 100 times. Watch these three objects – the moon, dazzling Venus and bright Regulus – adoring the morning dawn on October 12, 13, 14 and 15, 2020. Simply get up before daybreak, and look eastward.

The moon and Venus are nearby objects in our own solar system, shining by reflecting the light of our local star, the sun. Meanwhile, Regulus shines with its own light and is, in truth, a vastly more powerful object than either the moon or Venus, shining across some 79 light-years of space. It just doesn’t look as bright in our sky because it’s so far away. This mighty star is considerably larger and hotter than our sun. If it were located at the sun’s distance from us, Regulus would appear some 150 times brighter than our sun in the visible spectrum.

The moon will pass 4 degrees north of Venus on October 13 at 23:57 Universal Time (UTC). We won’t see the moon and Venus at this instant from the United States, because they’ll be either beneath the horizon or lost in a daytime sky. For us, the moon will be to the west of Venus on the morning of October 13 and to the east of Venus on the morning of October 14.

Did you know that Venus goes through the whole range of phases like our moon? However, you need a telescope to see the phases of Venus. You might think that the moon and Venus should show a similar phase when the moon swings to the north of Venus. After all, these two worlds will nearly reside on the same line of sight. But no, their phases aren’t even close. Venus now exhibits a waxing gibbous phase (over 75 percent illuminated), while the moon will display a waning crescent phase (about 11.5 percent illuminated on the morning of October 13).

The reason for this disparity is that the moon orbits Earth while Venus orbits the sun. When Galileo first looked at Venus through the telescope in the early 1600s, he noted Venus’ changing phases. Venus’ phases revealed to Galileo that Venus orbits the sun, not Earth (as was commonly believed in Galileo’s day). This revelation gave impetus to the possibility of a sun-centered solar system.

Bottom line: Watch for the moon, Venus and the bright star Regulus in the constellation Leo the Lion, as they beautify the eastern sky before sunup on October 12, 13, 14 and 15, 2020!

Mars to reach opposition October 13

Posted by Bruce McClure in TONIGHT | October 12, 2020

Mars at opposition (Earth between Mars and the sun).

Image at top: When Mars reaches opposition, Earth is between Mars and the sun. Mars and the sun shine on opposite sides of our sky. Visualization via Kel ElkinsNASA.

On October 13, 2020, Mars comes to opposition in Earth’s sky for the first time since July 27, 2018. In mid-October, our planet Earth – in its smaller orbit around the sun – will pass more or less between the sun and Mars. As seen from Earth, Mars will appear opposite the sun: in the east at sunset, at its highest at midnight, setting in the west at sunrise. At this year’s opposition, in particular, Mars will be a fiery red and very wonderful sight all night long. Mars will be brighter at this year’s opposition than it will be again until the year 2035.

Mars’ 2020 opposition will come at around 23:00 UTC (7 p.m. EDT, 6 p.m. CDT, 5 p.m. MDT and 4 p.m. PDT) on October 13. Translate UTC to your time.

Opposition is a special time for any superior planet. Around the time of opposition, as Earth sweeps between the planet and the sun, that planet shines at its brightest in Earth’s sky for that earthly year.

Not all Mars’ oppositions are equal, however. This one is a very good one.

Sky photo with bright reddish dot to left and Milky Way streaming upward.

Planet Mars (left) and the Milky Way at Mars’ last opposition – July 2018 – via Mike Killian. See photos from this year.

Oppositions of Mars happen about every 26 months. That makes sense because Earth takes a year to orbit the sun, and Mars takes about two years. Every 26 months, we gain a lap on Mars, passing between it and the sun.

Because it’s now closest to us, throughout October 2020, Mars outshines all the stars. It outshines even the king planet Jupiter, which is generally the fourth-brightest sky object after the sun, moon and planet Venus (and Venus is now up before sunrise).

You can’t miss Mars right now!

Extra-close oppositions of Mars (less than 37 million miles or 60 million km) recur in periods of 15 to 17 years. The last extra-close Martian opposition happened on July 27, 2018, and the next one will occur on September 15, 2035. Thus 2020 brings Mars’ brightest appearance in our sky until the opposition of 2035. This October 2020 opposition Mars just misses being extra-close. At opposition this year, Mars is 38.57 million miles (62.07 million km) from Earth.

Extra-close oppositions happen when we go between Mars and the sun around the time Mars is near perihelion, its closest point to the sun. That makes sense, too, right? See the chart below:

Diagram of orbits of Earth and Mars.

Diagram by Roy L. Bishop. Copyright Royal Astronomical Society of Canada. Used with permission. Visit the RASC estore to purchase the Observer’s Handbook, a necessary tool for all skywatchers.

An extra-far opposition of Mars – over 62 million miles or 100 million km – last took place on March 3, 2012, when Mars was near aphelion, its farthest point from the sun. As a basis of comparison, the 2018 opposition found Mars some 28 million miles (45 million km) closer than at the extra-far opposition of 2012.

Extra-far oppositions also recur in periods of 15 to 17 years, and the next one will happen on February 19, 2027.

So enjoy Mars this year!

Diagram showing distances between Earth and Mars at opposition.

Extra-close oppositions of Mars happen every 15 to 17 years, when Earth passes between the sun and Mars around the time Mars is closest to the sun in its orbit. Illustration via Used with permission.

By the way, Mars’ exact closest point to Earth doesn’t typically coincide with the date of opposition. The time interval between opposition and Mars’ nearest point to Earth is no greater than 8.5 days, and can be as little as 10 minutes.

In 2020, we go between Mars and the sun on October 13, but Mars comes closest to Earth about a week before, on October 6. Why? It’s because planets in our solar system don’t orbit the sun in perfect circles (although their orbits are very nearly circular). The orbits of both Earth and Mars are ellipses, like circles someone sat down on.

What’s more, the planets in our solar system don’t all orbit the sun on the same plane (although their orbital planes are very similar).

The little differences bring Mars closer to Earth in 2020 on October 6 than on October 13, the day we pass between Mars and the sun.

Bright circle with two dim dots near it.

At the opposition of Mars in 2014, Anthony Wesley caught both of Mars’ moons. Here you see brighter and closer Phobos and fainter, more distant Deimos.

Bottom line: October 2020 presents Mars at its brightest in our sky until September 2035. Earth passes between Mars and the sun, at opposition, on October 13, 2020, yet Earth and Mars actually come closest together on October 6, 2020.

Autumn’s false dawn

Posted by Bruce McClure in TONIGHT | October 14, 2020

False dawn in the east before morning twilight

Photo of false dawn taken by Ken Christison in October October 2019.

The next few weeks offer a wonderful opportunity to catch the mysterious zodiacal light – aka the false dawn – of autumn. The moon is out of the morning sky for the next two weeks, leaving it dark to see this elusive phenomenon. The zodiacal light can be seen in the east, preceding dawn’s first light. Look over the sunrise point on the horizon about 120 to 80 minutes before sunrise.

Photo by Earthsky facebook friend Randall Kayfes, looking eastward in the predawn/dawn sky. Thank you Randall! The star Regulus, the brightest in the constellation Leo the Lion, shines very close to the horizon, almost dead center, dotting the backwards question mark of stars known as The Sickle. The bright star-like object to the upper right is actually the planet Jupiter.

If you’re in the Southern Hemisphere, where it’s the spring equinox (rather than the autumn equinox) that happened a few weeks ago, the zodiacal light appears in your western sky, beginning about an hour after the sun goes down. Watch for the zodiacal light about 80 to 120 minutes after sunset.

This light can be noticeable and easy to see from latitudes relatively close to Earth’s equator, for example, like those in the southern U.S. To those in rural locations, it’s often visible at this time of year while driving a lonely highway far from city lights, in the hour or so before true dawn begins to light the sky. In that case, the zodiacal light can resemble the lights of a city or town just over the horizon.

Meanwhile, skywatchers in the northern U.S. or Canada sometimes say, wistfully, that they’ve never seen it, although in recent years we’ve seen many photographs of the zodiacal light taken from northerly latitudes.

Here’s the zodiacal light as captured on film in Canada. This wonderful capture is from Robert Ede in Invermere, British Columbia.zodiacal light

You need a dark sky location to see the zodiacal light, someplace where city lights aren’t obscuring the natural lights in the sky. The zodiacal light is a pyramid-shaped glow in the east before dawn (or after twilight ends in the evening, if you’re in the Southern Hemisphere now). It’s even “milkier” in appearance than the starlit trail of the summer Milky Way. It’s most visible before dawn at this time of year because, as seen from the Northern Hemisphere, the ecliptic – or path of the sun, moon and planets – stands nearly straight up with respect to the eastern horizon before dawn now. As seen from the Southern Hemisphere, the same is true of the western horizon after true darkness falls.

The zodiacal light can be seen for up to an hour or so before true dawn begins to break. Once again, look for it about 120 to 80 minutes before sunrise. Unlike true dawn, though, there’s no rosy color to the zodiacal light. The reddish skies at dawn and dusk are caused by Earth’s atmosphere, and the zodiacal light originates far outside our atmosphere. When you see the zodiacal light, you are looking edgewise into our own solar system. The zodiacal light is actually sunlight reflecting off dust particles that move in the same plane as Earth and the other planets orbiting our sun.

Bottom line: No matter where you are on Earth, your local autumn is the best time to see the zodiacal light before dawn. Spring is the best time to see it in the evening.

Summer Triangle and galactic equator

Posted by Bruce McClure in TONIGHT | October 15, 2020

Tonight, use the Summer Triangle and the constellation Cygnus the Swan to locate the galactic equator – the great circle on the celestial sphere that bisects the glowing band of stars that we call the Milky Way. Sure, it’s autumn here in the Northern Hemisphere, but the three brilliant stars that make up the Summer Triangle still shine in our sky. You’ll find them way up high on October evenings.

View the scene from the comfort of a reclining lawn chair, with your feet pointing southward. Although every star that we see with the unaided eye is a member of our Milky Way galaxy, sometimes the term “Milky Way” refers to the edgewise view of the galactic disk, where the combined glow of myriads of far-off suns congregates into a beautiful archway lighting up the great vault of the sky.

As seen from mid-northern latitudes, the stars Deneb and Vega hang high overhead at nightfall and early evening. Vega, the brightest Summer Triangle star, shines to the west (or right) of Deneb, and Altair, the second brightest, is found roughly halfway between your southern horizon and straight overhead.

Dense star field with cloudy Milky Way running horizontally across it, and three bright stars.

The Summer Triangle (left side of image) and Milky Way. Altair shines a bit below center, while fainter Deneb is found at left center and the brightest star of the Summer Triangle, Vega, at upper left of center. Image via NASA/ESA.

As evening deepens, look for a modestly-bright star to pop out between Altair and Vega. That’s Albireo, which depicts the Swan’s eye or beak. The line from Albireo to Deneb shows you the underside of the Swan’s body from head to tail. Three stars cross the body near Deneb to form what is known as the Northern Cross. Go one star farther out on each side of the Northern Cross to finish off the Swan’s wings.Star chart with stars in black on white.

Sky chart of the constellation Cygnus the Swan via IAU.

Extend the Albireo-to-Deneb line in either direction to soar along the galactic equator (plane). Through binoculars, you’ll see that star clouds, star clusters and nebulae abound on this great galactic boulevard! Locate the Summer Triangle first, then the star Albireo, and you’ve got what it takes to find the glowing band of stars that we call the Milky Way.

Bottom line: You can use the Summer Triangle – and the constellation Cygnus the Swan – to locate the edgewise disk of our Milky Way galaxy.

Year’s closest new moon October 16

Posted by Bruce McClure in TONIGHT | October 16, 2020

A smaller full moon superimposed on a larger crescent moon.

Above photo by Peter Lowenstein: The mini-moon (full moon at apogee) superimposed on the young crescent moon (covered over in earthshine) near perigee. In October 2020, we have the year’s closest and largest new moon on October 16, and the year’s farthest and smallest full moon on Halloween (October 31).

Today – October 16, 2020 – brings us the closest new moon of the year. Although you can’t see today’s new moon, because it’s lost in the sun’s glare all day, you may see the impact of this extra-close new moon along the ocean shorelines over the next several days. Twice a month – at new moon and full moon- the gravitational pull of the moon teams up with that of the sun to usher forth spring tides. At spring tide, the difference in high tide and low tide is especially profound.

Looking for a tide almanac? EarthSky recommends …

Moon phases via Holt Physical Science class At new moon, the moon’s nighttime side faces Earth while the illuminated side faces the sun. At the vicinity of new moon, the moon rises and sets with the sun and is lost in the sun’s glare.

Moon’s orbit around Earth, seen from above. The moon’s dark side faces Earth at new moon, and its illuminated side faces Earth at full moon. At the quarter moons, we see one-half of the moon’s daytime side and one-half of its nighttime side. Read more: Understanding moon phases

There are a total of 12 new moons in 2020, but this October new moon is the one that most closely aligns with lunar perigee – the moon’s closest point to Earth in its monthly orbit. This month’s new moon only comes about 4 hours before the moon sweeps to lunar perigee. Some people will call this perigean new moon a supermoon.

New moon: October 16 at 19:31 UTC (221,797 miles or 356,948 km)
Lunar perigee: October 16 at 23:46 UTC (221,775 miles or 356,912 km)

A perigean new moon (or perigean full moon) accentuates the spring tide all the more. If you live along the coast, watch for the perigean spring tide to give more loft to high tide, and more depth to low tide.

Sun, moons at opposite sides of earth, straight line between objects with stretched ocean.

Around each new moon and full moon – when the sun, Earth, and moon are located more or less on a line in space – the range between high and low tides is greatest. These are the spring tides. Image via

One fortnight – one-half lunar month – after this perigean new moon, it’ll be the most distant and smallest full moon of the year on Halloween (October 31, 2020). That’s because of this year’s 13 full moons, the October 31 full moon comes the closest to aligning with lunar apogee – the moon’s farthest point in its monthly orbit around Earth. At a distance of 252,380 miles (406,166 km), this Halloween full moon is better than 30 thousand miles (49 thousand km) farther than the October 16th new moon.

Sometimes the year’s smallest full moon (apogean full moon) is called a micro-moon. This year, however, this micro-moon will also be called a Blue Moon, because it’ll be the second of two October 2020 full moons.

Read more: Blue Moon and Mars on Halloween!

Birth of young moon at day’s end

Posted by Bruce McClure in TONIGHT | October 17, 2020

Young moon in twilight sky after sunset.

The closest new moon of the year came to pass on October 16, 2020, at which time the moon was transitioning out of the morning sky and into the evening sky. One day later, on October 17, some people might spot the rebirth of the young moon at the day’s end, low in the western sky and in the afterglow of sunset. But this young, pale, fragile crescent will be nothing but skin and bones after sundown October 17. The young, skinny crescent will be even hard to spot with binoculars, much less the eye alone.

Read more: Year’s closest new moon October 16

October 16, 2012 young moon as seen from Smith Point County Park on Long Island, New York by EarthSky Facebook friend Annette DeGiovine. Thank you, Annette. Mercury is in the upper left of the photo. Click here to expand image

From everywhere worldwide, it’ll be easier to spot the young crescent after sunset on October 18 than on October 17. Day by day, a wider lunar crescent will appear higher up at sunset and will stay out longer after sundown. It’s hard to spot a young moon that’s less than one day old (less than 24 hours after new moon). If you want to try your luck on October 17, be sure to find an unobstructed horizon in the direction of sunset, find a hilltop if you can, and bring along binoculars!

Want to know when the moon sets in your sky? Click here and remember to check the moonrise and moonset box.Worldwide map of day and night sides of Earth one day after new moon.

The day and night sides of Earth one day after new moon (October 17 at 19:31 UTC. The line of sunset crosses the Atlantic Ocean. Everyplace east of this shadow line (Europe, Africa, Asia, Australia and New Zealand), the moon is less than one day (24 hours) old at sunset October 17, and everyplace west of it has sunset coming more than one day (24 hours) after new moon on October 17. Map via Earth View.

Because the new moon on October 16th was closely aligned with perigee – the moon’s closest point to Earth in its monthly orbit – the moon is now orbiting Earth at a maximum speed. On the average, the moon travels eastward in front of the backdrop stars of the zodiac at 13 degrees per day, and the young moon travels eastward of the sun at 12 degrees per day. (For reference, the moon’s angular diameter spans about 1/2 degree.)

Right now, however, the moon is traveling faster than average! It is moving 15 degrees per day relative to the backdrop stars, and 14 degrees per day relative to the sun.

Click on Heavens-Above to know the moon’s present position in front of the constellations of the zodiac.

Click on Heavens-Above to know the sun’s present position in front of the constellations of the zodiac

This faster moving moon benefits the world as a whole in the hunt for the young moon. Unfortunately for northerly latitudes, however, the ecliptic – the moon’s monthly pathway – crosses the horizon at a narrow angle at sunset and early evening. That buries the young moon in the glare of evening twilight. Although the moon will be over one day old at sunset October 17 in North America, it’ll still be hard to catch the lunar crescent on this date because of the shallow angle of the ecliptic.

In the Southern Hemisphere, however, the ecliptic – the monthly pathway of the moon – intersects the horizon at a steep angle at sunset and early evening. Therefore, in South America, the moon is higher up in the sky at sunset and stays out longer after sundown than it does in North America. We expect South American countries with clear skies and unobstructed western horizons to have a good chance of catching the young moon after sunset on October 17.Young moon from Southern Hemisphere.

Because the ecliptic – the monthly pathway of the moon – hits the horizon at a steep angle as the October sun sets in the Southern Hemisphere, the young moon stays out longer after sunset than in the Northern Hemisphere. Contrast this chart for mid-southern latitudes in the Southern hemisphere with the chart at top for mid-northern latitudes in the Northern Hemisphere.

See the chart immediately above for Valdivia, Chile. Valdivia, Chile (40 degrees south latitude) and Philadelphia, Pennsylvania (40 degrees north latitude) and pretty much reside on the same longitude (75 degrees west). On early spring evenings, the ecliptic – pathway of the sun, moon and planets – hits the evening horizon at a steep angle; and on early autumn evenings, the ecliptic intersects the evening horizon at a narrow angle. Since it’s now early spring in the Southern Hemisphere and early autumn in the Northern Hemisphere, the steeper angle of the ecliptic in Valdivia keeps the moon (and the planet Mercury) out longer after sundown than in Philadelphia.

For October 17, 2020

Valdivia (40 degrees south latitude):
Moon sets 75 minutes after the sun (October 17)
Mercury sets 84 minutes after the sun (October 17)

Philadelphia (40 degrees north latitude):
Moon sets 55 minutes after the sun (October 17)
Mercury sets 27 minutes after the sun (October 17)

You might or might not catch the young moon after sunset October 17. Even if you do, expect the young moon to become more picturesque in the following days, as a brighter, wider crescent better defines its once vague presence in the evening twilight. In days ahead, be sure to get an eyeful of the earthshine softly illuminating the dark (nighttime) side of the moon. Earthshine is twice-reflected sunlight, first reflected from the Earth to the moon, and then from the moon back to Earth.

Orionid meteors late night until dawn

Posted by Bruce McClure in TONIGHT | October 19, 2020

The Orionid meteor shower will peak around mid-week, with the best morning likely being Wednesday, October 21. Try watching on the mornings of October 20 and 22, too. In 2020, the moon will be a waxing crescent at the shower’s peak. That means the moon will set in the evening hours, or before the constellation Orion – the radiant of the Orionid shower – rises in the east at late evening. The Orionids start producing meteors at late evening but the number of meteors increases after midnight. Typically, the greatest number of Orionid meteors streak the sky during the few hours before dawn. In a moonless sky, you can see as many as 10 to 15 meteors per hour at the Orionids’ peak.

These meteors – vaporizing bits of comet debris from Halley’s Comet – look like streaks of light in the night sky. Many people call them shooting stars.

Thin, bright, colorful streak above an adobe house, saguaros and mountains in distance.

View larger to see the colors. | Orionid fireball captured at 11:14 p.m. local time in Tucson, Arizona, on October 22, 2017. Eliot Herman described this image as “my fav Orionid photo” and wrote: “Note giant red star Betelgeuse near the radiant and the Belt of Orion further to the right rising above the foothills. The remnant trail persisted for about 50 seconds with the first 14 seconds being quite visible and then remaining faintly visible for the rest of the minute following the fireball.” See Eliot’s all-sky movie of this entire night of meteor-watching in 2017.

Remember, you don’t need any special equipment to enjoy the show. Find an open sky away from pesky artificial lights, enjoy the comfort of a reclining lawn chair and look upward. Find dark locations at EarthSky’s stargazing page.

Just be sure to give yourself at least 20 minutes for your eyes to adapt to the darkness. And you’ll want at least an hour of viewing time. That’s because meteors often come in spurts, followed by lulls.

Outlined constellation Orion visible behind high, thin clouds.

Orionid meteors radiate from the constellation Orion, shown in this photo from October 2016 by Zefri Besar in Brunei Darussalam.

Where is the radiant point for the Orionid meteor shower? The radiant point for the Orionids is in the northern part of Orion, near Orion’s Club. Many see the Hunter as a large rectangle. You’ll surely notice its distinctive row of three medium-bright stars in the middle: those stars represent Orion’s Belt. The brightest star in the sky, Sirius, is to the southeast of Orion on the sky’s dome, and the Belt stars always point to Sirius. This constellation is up in the southeast in the hours after midnight and it’s high in the south before dawn. We will have much more to say about Orion in the months to come, because it’s one of winter’s most prominent constellations.

Do you need to know Orion to see the meteors? Nah. The meteors appear in all parts of the sky. But if you trace the paths of the meteors backward, you’ll see they all seem to come from this constellation.

How many meteors can you expect to see? The number of meteors you’ll see in any meteor shower always varies greatly depending on when and where you watch. Meteor showers are not entirely predictable. That’s the fun of them! In a dark sky, you might see about 15 meteors per hour, or one meteor every few minutes, during the Orionid peak.

Star chart of constellation Orion with arrow pointing from three stars in a short line to a bright star.

While looking for the Orionid’s radiant point, know that you can extend Orion’s Belt to locate Sirius, the sky’s brightest star.

When should you watch for Orionid meteors? Meteor showers aren’t just one-night events. The Orionid shower lasts from early October to early November, as Earth passes through a stream of debris left behind by a comet, in this case, the famous Comet Halley. According to the International Meteor Organization (IMO), the Orionids often exhibit several lesser maxima, so meteor activity may remain more or less constant for several nights in a row, centered on a peak night.

So, before dawn on October 20 or 22, the Orionids might match – or nearly match – the numbers before dawn on October 21. The Orionid meteors generally start at late night, or around midnight, and display maximum numbers in the predawn hours. That’s true no matter where you live on Earth, or what time zone you’re in. If you peer in a dark sky between midnight and dawn on October 20, 21 or 22, you’ll likely see some meteors flying.

Want to know when morning dawn (astronomical twilight) first begins? Visit Sunrise Sunset Calendars and remember to check the astronomical twilight box.

What should you watch for during the Orionid shower? If you’d like to make a new friend, or revisit an old one, enjoy the company of the constellation Orion – the radiant of the Orionid meteor shower – on this dark night. Orion rises in the east at late evening, fairly close to midnight. Surrounding Orion are the bright stars typically associated with winter evenings in the Northern Hemisphere. There are many bright stars in this part of the sky, and they are beautiful and colorful. Want to try to identify some? Your best bet is a planisphere.

Want more about 2020’s Orionid meteor shower? Click here

Thin, very bright streak on left in dark sky, constellation Orion on right with Sirius near horizon.

Possible Orionid meteor moving by the Gemini stars Castor and Pollux. The constellation Orion the Hunter is found at the upper right and the star Sirius below Orion’s Belt. Image via Mike Lewinski.

Bottom line: The waxing crescent moon sets in the evening, providing dark skies for the 2020 Orionid meteor shower. Watch in the dark hours before dawn. Try watching on the mornings of October 20, 21 and 22. A dark sky is always best.

Orionid meteor shower peak tonight!

Posted by Bruce McClure in TONIGHT | October 20, 2020

Above: Photo from Goldpaint Photography of the October 2011 Orionid meteor shower at Middle Falls, located just outside the city of McCloud near Mount Shasta, CA. It’s a composite consisting of every meteor captured during the night and includes the Milky Way crashing into the illuminated falls. The image was Grand Prize Winner of Outdoor Photographer Magazine’s 3rd Annual Great Outdoors Photography Contest and published in their July 2012 issue. Notice there is more than one shower happening here. More from Goldpaint Photography here.

Tonight – the night of October 20-21, 2020 – may well present the Orionid meteor shower’s peak night. They’ll probably be most prolific in the few hours before dawn on October 21, but try watching before dawn on October 22, too.

From a dark site, you might see a maximum of about 10 to 15 meteors per hour.

Fortunately, the waxing crescent moon will set in the evening, so there’ll be no moonlight to ruin this year’s Orionid meteor shower. Click here to find out the moon’s setting time in your sky, remembering to check the moonrise and moonset box.

As is the case for many meteor showers, the best time to watch is between midnight and dawn – regardless of your time zone.

The meteors – vaporizing bits of comet ice and dust – will look like streaks of light in the night sky. They’re sometimes called shooting stars.

An hour or two before dawn’s first light, watch for the planet Venus to rise into your eastern predawn sky. Click here for a recommended sky almanac; an almanac can help you determine rising time for Venus in your sky.

The predawn and dawn sky also offers a great view of Sirius, the sky’s brightest star. Watch for it in the south (or overhead if you’re in the Southern Hemisphere) before dawn.

Halley's Comet at its 1910 visit.  The famous astronomer Edward Emerson Barnard at Yerkes Observatory in Wisconsin took this photo.  Via Wikimedia Commons.

Halley’s Comet at its 1910 visit. The famous astronomer Edward Emerson Barnard at Yerkes Observatory in Wisconsin took this photo. Image via Wikimedia Commons.

The Orionids stem from debris from the most famous of all comets, Comet Halley, pictured above. The picture shows Comet Halley itself at its 1910 visit. The comet last visited Earth in 1986 and will return next in 2061.

As Comet Halley moves through space, it leaves debris in its wake that strikes Earth’s atmosphere most fully around October 20-22, every year. The comet is nowhere near, but, around this time every year, Earth is intersecting the comet’s orbit.

If the meteors originate from Comet Halley, why are they called the Orionids? The answer is that meteors in annual showers are named for the point in our sky from which they appear to radiate. The radiant point for the Orionids is in the direction of the constellation Orion the Hunter. Hence the name.

Orionid meteors radiate from the constellation Orion, which was captured a few days ago - October 16, 2016 - by Zefri Besar in Brunei Darussalam. He wrote:

Orionid meteors radiate from the constellation Orion, shown in this photo from October, 2016 by Zefri Besar in Brunei Darussalam.

Remember … even one meteor can be a thrill. Just be sure you have a dark sky.

Bring along a blanket or lawn chair – after midnight or before dawn – and lie back comfortably while gazing upward. Although a somewhat modest shower, these swift-moving meteors are sometimes bright, occasionally leaving a persistent train – a glowing streak that lingers momentarily after the meteor has gone!

Photo from Goldpaint Photography of the 2011 Orionid meteor shower near Mount Shasta, California. It’s a composite of every meteor captured during the night. The image was Grand Prize Winner of Outdoor Photographer Magazine’s 3rd Annual Great Outdoors Photography Contest.

Bottom line: Best night for the Orionid meteor shower in 2020 is probably October 20-21, especially between midnight and dawn October 21. You might see as many as 10 to 15 meteors per hour from a dark site. Fortunately, no moon will ruin this year’s Orionid meteor shower.

Moon sweeps by Jupiter and Saturn

Posted by Bruce McClure in TONIGHT | October 21, 2020

Moon sweeps by the planets Jupiter and Saturn.

These next several evenings – October 21, 22 and 23, 2020 – watch for the waxing moon to sweep by the gas giant planets, Jupiter and Saturn. Jupiter, which is the brighter of the two, beams some 13 times brighter than Saturn. The only starlike object to outshine Jupiter in the evening sky right now is the red planet Mars, but Mars sits low in the eastern sky at evening dusk and nightfall. So there’s no way to mistake Jupiter for Mars.Sponsored by Advertising PartnerSponsored VideoWatch to learn more

Read more: Moon, Mars meet in late October

Saturn, the sixth planet outward from the sun, is the farthest world that you can easily see with the unaided eye. The farther away that a planet resides from the sun, the more slowly it travels and the longer its orbit. Saturn takes nearly 30 Earth-years to orbit the sun.

Sizes of sun and planets to scale, but distances are not. Uranus is hard to see with the eye alone, and Neptune requires an optical aid. Bill Nye demonstrates distances between planets

Jupiter, the 5th planet outward, is a touch more than half Saturn’s distance from the sun. Nonetheless, Jupiter is the second farthest world that we can easily see from Earth. Jupiter in its faster and smaller orbit takes about 12 Earth-years to go around the sun full circle.

Because Jupiter and Saturn take so long to pass through all the constellations of the zodiac, a Jupiter-Saturn conjunction is the rarest of planet-planet conjunctions involving two bright planets. Incidentally, the bright planets are Mercury, Venus, (Earth), Mars, Jupiter and Saturn. Conjunctions of Jupiter-Saturn recur in periods of 20 years.Antique etching of zodiac circle with triangles inside marked with year dates.

Johannes Kepler (1571-1630) maps out 10 heliocentric (sun-centered) Jupiter/Saturn conjunctions during the 180-year period from 1583 to 1763. After 60 years, the planets meet up at nearly the same place on the zodiac, with a displacement of about 8 degrees eastward relative to the background stars. Drawing taken from Kepler’s De Stella Nova (Prague, 1606).

The next Jupiter-Saturn conjunction will come in two months, on December 21, 2020. The last Jupiter-Saturn conjunction took place on May 28, 2000, and the next one after the upcoming Jupiter-Saturn conjunction December 21, 2020, will come on October 31, 2040.

However, this upcoming conjunction on December 21, 2020, counts as super special, because it’ll showcase the closest Jupiter-Saturn conjunction since July 16, 1623. Jupiter and Saturn will only be 0.1 degree (1/5th the moon’s apparent diameter) apart on December 21, 2020, at 14 hours UTC.

Artist’s concept of Jupiter and Saturn in December of 2020, as viewed from a space-based perspective. Their conjunction will be December 21. See the moon in this drawing? It’ll be along our line of sight to the planets on December 16, 2020. Chart via Jay Ryan at

Use the moon to find Jupiter and Saturn these next few nights and then watch for Jupiter to close the gap between itself and Saturn over the next two months. Jupiter and Saturn ended their retrograde motion (westward movement in front of the backdrop stars) on September 13 and 29, 2020, respectively. These two worlds are now moving eastward in front the constellation Sagittarius the Archer. At their December 21st conjunction, these two worlds will meet up in front of the constellation Capricornus the Seagoat.

Presently – on October 21, 2020 – Jupiter and Saturn reside about 6 degrees apart on the sky’s dome. (For reference, the moon’s angular diameter equals about 1/2 degree.) This next month – from October 21 to November 21, 2020 – Jupiter will move about 5 degrees while Saturn will go about 2 degrees. So Jupiter will gain 3 degrees on Saturn, and the two gas giant planets will be some 3 degrees apart as of November 21, 2020.Jupiter and Saturn, annotated. Jupiter is 13 times brighter than Saturn.

View at EarthSky Community Photos. | Here’s a closeup of Jupiter and Saturn, caught by Dr Ski in Valencia, Philippines on April 30, 2020. Jupiter is the brighter object. Thank you, Dr Ski!

The following month – November 21 to December 21, 2020 – Jupiter will travel about 6 degrees and Saturn 3 degrees. That means Jupiter will have bridged the 3-degree gap that had existed between the king planet and Saturn on November 21, 2020!

Overall – from October 21 to December 21, 2020 – Jupiter will have traveled 11 degrees and Saturn 5 degrees. Bingo! That’ll completely close the 6-degree gap that separated Jupiter and Saturn on October 21, 2020! December 21 will not only present the first Jupiter-Saturn conjunction since the year 2000, but it’ll give us the closest Jupiter-Saturn conjunction since the year 1623. The extra-close Jupiter-Saturn conjunction in 2020 won’t be matched again until the Jupiter-Saturn conjunction of March 15, 2080!

These next several evenings- October 21, 22 and 23, 2020 – let the moon serve as your tour guide to the gas giant planets, Jupiter and Saturn. Then watch for Jupiter to slowly but surely close the 6-degree gap between itself and Saturn. When Jupiter finally catches up with Saturn on December 21, 2020, Jupiter will pass a scant 0.1 degrees to the south of Saturn, to stage the closest Jupiter-Saturn conjunction in 397 years!

Read more: Before 2020 ends, a great conjunction of Jupiter and Saturn

Bright star Deneb transits at nightfall

Posted by Bruce McClure in TONIGHT | October 24, 2020

Each year – around October 24 – the northernmost star of the Summer Triangle, Deneb, transits or climbs to its highest point in the sky at or near 6:30 p.m. local time (7:30 p.m. local daylight saving time). What does that mean for skywatchers? Only that this noteworthy star – this beloved member of the Summer Triangle – is shifting ever-westward each day in our sky as Earth travels around the sun. Its transit at dusk/nightfall is a hallmark of the year, marking a shift toward winter – or summer – on your half of the globe.

When the sun or a star transits, it resides at one of three places: at zenith (straight overhead), north of zenith or south of zenith.

At 45 degrees north latitude (St. Paul, Minnesota, and Turin, Italy), Deneb shines straight overhead when it transits.

At 40 degrees north latitude (Denver, Colorado, and Beijing, China), Deneb soars to its highest point (about 5 degrees north of zenith) as evening dusk is giveing way to nightfall.

The meridian is the imaginary semicircle that arcs across the sky from due north to due south. The sun or any star climbs to its highest point for the day when it crosses your meridian.

At temperate latitudes in the Southern Hemisphere, where it’s now springtime, Deneb transits at or near the same hour by the clock (near 6:30 p.m. local time). Yet, the sun sets later by the clock at more southerly latitudes, so in the Southern Hemisphere, Deneb at this time of year actually transits when the sun is still up, instead of dusk/nightfall.

At more northerly or southerly latitudes, Deneb either transits to the north or to the south of the zenith point. Appreciably south of 45 degrees north latitude, Deneb lies to the north of the zenith point when it transits; conversely, when Deneb transits at latitudes appreciably north of 45 degrees north latitude, Deneb is viewed in the southern sky.

Two brilliant stars – Vega and Altair – team up with Deneb to complete the humongous Summer Triangle. The luminous Summer Triangle asterism, or star formation, can often be seen in a twilight sky or even from a light-polluted city.

Star field with constellation Cassiopeia and Summer Triangle with stars labeled.

The Great Rift of the Milky Way passes through the constellation Cassiopeia and the Summer Triangle. Click here for a larger photo.

From mid-northern latitudes, the far-northern stars Deneb and Vega are seen at the “top” of the Summer Triangle whereas the southernmost star Altair is seen at the “bottom.” From the Southern Hemisphere, it’s the other way around: Altair reigns at top and Deneb at bottom. It’s a matter of perspective.

Vega, the Summer Triangle’s westernmost star, is seen to the right of Deneb from mid-northern latitudes. From the Southern Hemisphere, on the other hand, Vega lies to the left of Deneb.

Around the world, the stars of the Summer Triangle transit some four minutes earlier with each following day (or two hours earlier with each following month). So, from northerly latitudes, the Summer Triangle is destined to shift over into the western sky at nightfall as autumn ebbs toward winter … or, for those in the Southern Hemisphere, as spring blooms into summer.

Bottom line: As darkness falls in mid-October, the star Deneb shines at the apex of the sky at mid-northern latitudes.

Watch Capella flashing red and green

Posted by Deborah Byrd in TONIGHT | October 25, 2020

This evening, check out one of the flashiest stars in the sky. It’s so bright that every year in northern autumn, we get questions from people in the Northern Hemisphere who see a bright star twinkling with red and green flashes. It’s found low in the northeastern sky at nightfall or early evening as seen from mid-northern locations. That star is likely Capella, which is actually a golden star.

In fact, if you could travel to it in space, you’d find that Capella is really two golden stars, both with roughly the same surface temperature as our local star, the sun … but both larger and brighter than our sun.

Capella is in the constellation Auriga the Charioteer, but since antiquity it has carried the name Goat Star. You might pick it out just by gazing northeastward from a Northern Hemisphere latitude during the evening hours in October. Capella climbs upward through the night, and, this month, soars high overhead in the wee hours before dawn.

Bright star with colors in four diffraction spikes coming out from it like rays.

Scott MacNeill at Frosty Drew Observatory in Rhode Island wrote in October 2016: “I noticed how fabulous Capella looked just hanging in the northeast sky. So I directed my telescope to Capella and captured this shot.” Thanks, Scott!

So here is a golden point of light that flashes red and green when it’s low in the sky. Why does it do that?

The reality is that every star in the sky undergoes the same process as Capella, to produce its colorful twinkling. That is, every star’s light must shine through Earth’s atmosphere before reaching our eyes. But not every star flashes as noticeably as Capella. The flashes are happening because Capella is low in the sky in the evening at this time of year. And, when you look at an object low in the sky, you’re looking through more atmosphere than when the same object is overhead.

The atmosphere splits or “refracts” the star’s light, just as a prism splits sunlight.

So that’s where Capella’s red and green flashes are coming from … not from the star itself … but from the refraction of its light by our atmosphere. When you see Capella higher in the sky, you’ll find that these glints of red and green will disappear.

By the way, why are these flashes of color so noticeable with Capella? The reason is simply that it’s a bright star. It’s the sixth brightest star in Earth’s sky, not including our sun.

Star chart with single star near horizon.

Capella is a bright star, what astronomers call a 1st magnitude star. It’s one of the brightest stars in our sky. If you’re in the Northern Hemisphere, and you happen to look in the northeast one evening, you might notice Capella as a bright, flashy star near the northeastern horizon.

Bottom line: If you’re in Earth’s Northern Hemisphere, a bright star twinkling with red and green flashes, low in the northeastern sky on October evenings, is probably Capella.

Watch for Sirius, sky’s brightest star

Posted by Deborah Byrd in TONIGHT | October 26, 2020

If you’re up before daybreak, take a moment to see the sky’s brightest star, Sirius, on these October mornings. This star is so brilliant that you can even see it from a light-polluted city. Visit the U.S. Naval Observatory to find out when Sirius will rise tonight from your part of the world.

Andy wrote:

Early this morning, looking southeast, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Sirius is now rising in the southeast in the hours after midnight and can be found in the south at dawn. Notice that a line from Orion’s Belt points to Sirius.

Constellation Orion standing high in sky with bright star to its lower left.

View larger. | Brightest star Sirius on left, with constellation Orion. See how three stars of Orion’s Belt point to Sirius? This photo from EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan!

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius, which is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

More about Sirius: Dog Star and brightest star

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the star Sirius in the constellation Canis Major, brightest star in the sky. The bright planet Venus is also up before dawn now. But you’ll know Sirius, because Orion’s Belt always points to it.

Watch for Earth’s shadow and the Belt of Venus

Posted by Deborah Byrd in TONIGHT | October 27, 2020

In both the evening and morning sky, try watching for Earth’s shadow, a blue-gray darkness in the direction opposite the sun, darker than the twilight sky.

The pink band above the shadow – in the east after sunset, or west before dawn – is called the Belt of Venus.

Nearly full moon in sky with bands of deep mauve, pin, and dark sky blue over ocean.

Nancy Ricigliano from Massapegua, New York, caught the moon rising ahead of Earth’s shadow on October 21, 2018. She wrote: “I went out to see where the moon will be rising for the full Hunter’s Moon on Wednesday. I was able to capture the Earth’s shadow and the Belt of Venus!”

The moon phase shifts throughout the month, and sometimes you won’t find the moon in the night sky. Earth’s shadow, on the other hand, is more reliable. It can be seen any clear evening, ascending in the eastern sky at the same rate that the sun sets below the western horizon.

The shadow of the Earth is big. You might have to turn your head to see the whole thing. And the shadow is curved, just as the shadow of any round object is curved. Earth’s shadow extends hundreds of thousands of miles into space, so far that it can touch the moon. Whenever that happens, we see an eclipse of the moon.

Read more and see more photos: When can you see Earth’s shadow?

Tall saguaro cactus and full moon against sky with dark pink and blue bands.

Full moon and Earth’s shadow on the morning of March 2, 2018, via Eliot Herman in Tucson, Arizona.

Tiny full moon in deep blue sky with dark band above horizon.

Sucheta Wipat caught the Earth’s shadow and Belt of Venus on a cloudy evening in London, August 5, 2017. Yes, you can see it from cities!

Purplish pink sky over blue band above horizon, reflected in calm sea.

Earth’s shadow is the dark blue area above the line of the horizon, in this photo taken in January 2018 by Jörgen Andersson in Sweden.

Bottom line: Check out Earth’s shadow – in the east after sunset or in the west before sunrise – next time you have a clear sky. I often see it while out on the streets of my town as the sun is setting. The pink coloration above the shadow is called the Belt of Venus.

Moon, Mars meet in late October

Posted by Bruce McClure in TONIGHT | October 28, 2020

Monn meets up with Mars in late October 2020.

These next several nights – October 28, 29 and 30, 2020 – watch for the bright waxing gibbous moon to sweep by the red planet Mars. This month, Mars came closest to Mars for the year, and, in turn, Mars shone most brilliantly in Earth’s sky for the year. However, Mars won’t outdo this month’s production until September 2015. Enjoy Mars right now while ti’s still bright and beautiful!

This is the second time that the moon pairs up with Mars in October, having dons o previously on the night of October 2-3, 2020. But that’s not all. The upcoming full moon on Halloween (October 31) counts as the second full moon of October 2020. The first full moon, the Northern Hemisphere’s Harvest Moon, fell on October 1, 2020.

Read more: Blue Moon and Mars on Halloween

This month, in October 2020, Mars actually supplanted the king planet Jupiter as the fourth brightest celestial body to light up the heavens (after the sun, moon and the planet Venus, respectively). In November 2020, however, Jupiter will reclaim its accustomed spot in the heavenly hierarchy. Earth, in its faster and smaller orbit around the sun, is now traveling away from Mars. Therefore, the red planet is slowly bur surely dim in Earth’s sky. Nonetheless, Mars will continue to shine more brilliantly than a 1st-magnitude star for the rest of the year.

The moon will pass 3 degrees to the south of Mars on October 29, 2020, at 16:13 UTC. That’s during the daylight hours October 29 at North American time zones, when the moon and Mars will still be below our horizon. From North America, we’ll see the moon to the southwest of Mars as darkness falls on October 28, and then to the southeast of Mars at nightfall October 29.

Our planet Earth, in our faster and smaller orbit around the sun, laps Mars in periods of about 2 years and 2 months. Whenever Earth passes in between Mars and the sun, Mars is said to be at opposition. It’s at opposition that Mars is opposite the sun in Earth’s sky the sun in Earth’s sky. It’s at or around opposition that Earth comes closest to Mars for the year, and Mars, in turn, shines most brilliantly in Earth’s sky. Mars’ most recent opposition took place on October 13, 2020, and Mars’ next opposition will happen on December 28, 2022.A top-down image of the orbits of Earth and Mars, via NASA. Earth's orbit is nearly circular. Mars' orbit is more elliptical.

Because Mars has such an eccentric (oblong) orbit around the sun, Martian oppositions are far from equal. Especially close oppositions happen in late August/early September, and especially far oppositions in late February/early March.

Yet, the next 6 oppositions of Mars will be farther away than this year’s, and Mars won’t showcase a brighter production until the opposition of September 15, 2035. We give the distances for Mars for the oppositions from 2020 to 2035, inclusive, in terms of the astronomical unit (AU). The astronomical unit is the sun-Earth distance of about 93 million miles or 150 million km.

Martian oppositions 2020 to 2035

2020 October 13: 0.41 AU
2022 December 28: 0.54 AU
2025 January 16: 0.64 AU
2027 February 19: 0.68 AU
2029 March 25: 0.65 AU
2031 May 4: 0.55 AU
2033 June 28: 0.42 AU
2035 September 15: 0.39 AU

Read more: The cycle of close and far Martian oppositions

Blue Moon and red Mars on Halloween!

Posted by Bruce McClure in TONIGHT | October 30, 2020

Blue Moon and red Mars in late October 2020

The second of two October 2020 full moons falls right on Halloween (October 31, 2020)! By popular acclaim, the second of two full moons in one calendar month is called a Blue Moon. Most often, a calendar month only has one full moon. By the way, that bright red “star” near the moon is no star at all but the planet Mars.

Read more: Full Harvest Moon on October 1, 2020

Around the world, the moon will appear full to the eye for the next couple of nights (October 30 and 31, 2020). Astronomically speaking, however, full moon happens at the instant that it’s directly opposite the sun (180 degrees from the sun in celestial longitude). This full moon moment comes on October 31, at 14:49 UTC (9:49 a.m. EST, 8:49 a.m. CST, 7:49 a.m MDT, 6:49 a.m. PDT, 5:49 a.m. Alaskan Time and 4:49 a.m. Hawaiian Time).

People will also call this full moon a micro-moon because it’s the most distant (and smallest) full moon in 2020 (252,380 miles or 406,166 km). Exactly seven lunar months (seven full moons) previous to this Halloween Blue Moon, we had the closest and biggest full moon of the year on April 8, 2020 (221,851 miles or 357,035 km). And exactly 7 lunar months (7 full moons) after this Halloween Blue Moon, next year’s closest and largest full moon will occur on May 26, 2021 (222,116 miles or 357,461 km).

Full moons at apogee (left) and perigee (right) in 2011. Composite image by EarthSky community member C.B. Devgun in India. Thanks, C.B.!

The next monthly Blue Moon (second full moon in one calendar month) will come on August 31, 2023. This time around, however, it’ll be a Blue Moon supermoon (closest and largest full moon of 2023). This Blue Moon supermoon will be 222,043 miles or 357,344 km distant.

Every 19 years, the phases of the moon recur on (or near) the same calendar dates. Sure enough, looking 19 years into the future, we find the second full moon in October 2039 falling right on Halloween (October 31, 2039).

In this 19-year lunar cycle, there are 235 lunar months (235 returns to full moon) yet only 228 calendar months. Because the number of full moons outnumber the number of calendar months, that means at least seven of these 228 calendar months must harbor two full moons (235 – 228 = 7 extra full moons).

However, if a February within this 19-year period has no full moon at all – as is the case in February 2037 – that means this extra 8th full moon must fall into the lap of another calendar month, as well. Therefore, the year 2037 actually sports two Blue Moons, in January and March of 2037, giving us a total of 8 Blue-Moon months in the upcoming 19-year Metonic cycle:

1. August 31, 2023
2. May 31, 2026
3. December 31, 2028
4. September 30, 2031
5. July 31, 2034
6. January 31, 2037
7. March 31, 2037
8. October 31, 2039

Because calendar months and lunar months are not equal, the discordance between the two creates a calendar oddity known as the Blue Moon. Enjoy the spooky dissonance of this Halloween Blue Moon, as it’ll be the last full moon to fall on Halloween until October 31, 2039!