Moon and Antares in early July
These next few evenings – July 1 and 2, 2020 – let the moon introduce you to Antares. It’s a red star and the brightest star in the constellation Scorpius the Scorpion. Look first for the moon, and the nearby bright star will be Antares.
Any red-looking star that you can see with the unaided eye is either a red giant or red supergiant star. Antares is a red supergiant. This star, which is in the autumn of its years, is expected to explode as a supernova one of these days. No telling when that will be, however. It could happen tomorrow or a million years from now.
Although Antares lies way out there, at some 600 light-years distant, this star easily shines at 1st-magnitude brightness. In order to beam so brightly in our sky, this star must be extremely luminous, that is, intrinsically very brilliant as opposed to merely appearing bright because of a nearer distance.
Antares’ red color indicates a relatively cool surface temperature, and cool stars shine less brilliantly than hot stars of the same size. But Antares is just so big! Its sheer size makes this star more luminous than many stars with higher surface temperatures.
If Antares replaced the sun in our solar system, its circumference would extend beyond the orbit of the fourth planet, Mars. In this illustration, Antares is shown in contrast to another star, Arcturus, and our sun. Image via Wikimedia Commons.
Just how large is this incredible star? It’s not known with absolute certainty, but its radius is thought to be about three times the Earth’s distance from the sun (3 astronomical units). That’s about 3/5 the way from the sun to the orbit of Jupiter, the fifth planet outward from the sun. The radius of Antares is the equivalent of approximately 650 solar radii.
Presuming a radius of 650 solar radii and therefore a diameter of 650 solar diameters, that means the surface area of Antares exceeds that of our sun by some 122,500 times (Antares’ surface area = 650 x 650 = 122,500 solar). But Antares’ volume is actually a few hundred million times greater than the sun’s (Antares’ volume = 650 x 650 x 650 = 271,630,000 solar). And just to think that the sun has the volume of 1,300,000 Earths!
This artist’s concept shows the red supergiant star Antares in the constellation Scorpius. Image via ESO/ M. Kornmesser.
Bottom line: This evening – July 2, 2020 – let the moon be your guide to Antares, a red supergiant star whose humongous size is truly difficult to fathom!
Earth farthest from the sun on July 4
Posted by Deborah Byrd in TONIGHT | July 3, 2020
Image at top via Sara Zimmerman at Unearthed Comics. Thanks, Sara!
Planet Earth reaches a milestone on July 4, 2020, as it swings out to aphelion, its most distant point from the sun. It happens at 11:35 UTC. That’s 6:35 a.m. Central Daylight Time in the U.S. Translate UTC to your time. Is it hot outside for you on your part of Earth right now? Or cold out? Earth’s aphelion comes in the midst of Northern Hemisphere summer and Southern Hemisphere winter. That should tell you that our distance from the sun doesn’t cause the seasons. More about that below.
Image credit: NASA
The fact is, Earth’s orbit is almost, but not quite, circular. So our distance from the sun doesn’t change much. Today, we’re about 3 million miles (5 million km) farther from the sun than we will be six months from now. That’s in contrast to our average distance from the sun of about 93 million miles (150 million km).
The word aphelion, by the way, comes from the Greek words apo meaning away, off, apart and helios, for the Greek god of the sun. Apart from the sun. That’s us, today.
Looking for Earth’s exact distance from the sun at aphelion? It’s 94,507,635 miles (152,095,295 km) . Last year, on July 4, 2019, the Earth at aphelion was a tiny bit farther, at 94,513,221 miles (152,104,285 km).
The sun at aphelion appears smaller in our sky, as shown in this composite image. This image consists of 2 photos, taken just days away from a perihelion (Earth’s closest point to sun) in January, 2016, and an aphelion (Earth’s farthest point from sun) in July, 2017. The gray rim around the sun (actually the perihelion photo) illustrates that, as seen in our sky, the sun is about 3.6% bigger at perihelion than aphelion. This difference is, of course, too small to detect with the eye. Peter Lowenstein in Mutare, Zimbabwe – who captured the photos and created the composite – wrote: “Although taken 18 months apart, and a few days from the events due to adverse weather conditions, they show that there is an unmistakable size difference of the sun as viewed from Earth when it is closest at perihelion and furthest away at aphelion.”
This animation shows what’s also in the image above … the size difference of the sun between Earth’s perihelion (closest point) and aphelion (farthest point).
Here’s what does cause the seasons. The seasons aren’t due to Earth’s changing distance from the sun. We’re always farthest from the sun in early July during northern summer and closest in January during northern winter.
Instead, the seasons result from Earth’s tilt on its axis. Right now, it’s summer in the Northern Hemisphere because the northern part of Earth is tilted most toward the sun.
Meanwhile, it’s winter in the Southern Hemisphere because the southern part of Earth is tilted most away from the sun.
Earth’s varying distance from the sun does affect the length of the seasons. That’s because, at our farthest from the sun, like now, Earth is traveling most slowly in its orbit. That makes summer the longest season in the Northern Hemisphere and winter the longest season on the southern half of the globe.
Conversely, winter is the shortest season in the Northern Hemisphere, and summer is the shortest in the Southern Hemisphere, in each instance by nearly five days.
Bottom line: Planet Earth reaches its most distant point from the sun for 2020 on July 4. Astronomers call this yearly point in Earth’s orbit our aphelion.
Full moon, faint eclipse, on July 4-5
Posted by Bruce McClure in TONIGHT | July 4, 2020
For us in the Americas, the moon will turn precisely full during the nighttime hours on July 4-5, 2020, to present a partial penumbral eclipse of the moon. It’ll be such a faint eclipse – so nearly imperceptible – that some of you will swear nothing is happening even while staring straight at it. Then again … very observant people might notice something strange happening on the moon, even without knowing an eclipse is taking place. Who will see it (or not) in this post. But first …
On the night of July 4-5, there’s another astronomical event taking place that we all can see. This July full moon will shine near on the sky’s dome to the very bright king planet Jupiter, and also to the ringed planet Saturn. You need a telescope to see Saturn’s rings. But you’ll enjoy seeing Jupiter and Saturn close together. If you’re in the U.S., look up after or during any 4th of July fireworks display you might be attending. Jupiter, Saturn and the moon will be putting on a show, too.
Jupiter and Saturn are now at their best. Later this month, Earth will pass between each of these worlds and the sun, so that both Jupiter and Saturn reach their oppositions, Jupiter on July 13-14 and Saturn on July 20.
Now about that penumbral lunar eclipse on the night of July 4-5 … The eclipse happens for everyone at the same time worldwide. The time on your clock will depend on your location.
Day and night sides of Earth at the instant of full moon (July 5, 2020 at 04:44 UTC). The shadow line at left – crossing the Pacific Ocean and northern North America – depicts sunset July 4. The shadow line at right – running through Spain and Africa – depicts sunrise July 5. So, for example, Spain and Portugal won’t have a good view of the eclipse.This faint partial penumbral eclipse – difficult to view at best, even in a dark sky – must compete with the glare of morning twilight in that part of the world. Now notice North America. This faint eclipse will occur in our night sky on July 4-5. How well you see it will depend on your sky conditions, eyesight and ability to see. Worldwide map via Fourmilab.
We in the Americas are well situated to view this extremely faint, partial penumbral eclipse of the moon on the night of July 4-5.
The chance is there … but will you notice anything even if you catch the eclipse? That depends in part on your eyesight, in part on your experience watching eclipses, and in part on your powers of observation.
So of course many will watch it! Just don’t be disappointed if it’s, shall we say, lacking in drama? At best, it’ll be a subtle shading on the moon.
This eclipse wins some distinction because it’s the third of three eclipses in one eclipse season. More often than not, an eclipse season only harbors two eclipses.
Use Big Dipper to find Polaris
Posted by Deborah Byrd in TONIGHT | July 7, 2020
Tonight, use the Big Dipper in the constellation Ursa Major the Great Bear to find the sky’s northern pole star, Polaris. This is the star around which the whole northern celestial sphere appears to turn throughout the night. That’s because this star is located nearly above Earth’s northern axis. In times past, wanderers on the northern face of Earth used Polaris to stay on course.
Once you find it, you can also look for Thuban, a famous former pole star in the constellation Draco the Dragon. More about finding Thuban below.
So how can you find Polaris? Look at the chart at the top of this post. You’ll simply draw a line through the Big Dipper’s pointer stars – Dubhe and Merak. That line will point to Polaris, the North Star. You can use this trick to find Polaris any evening – no matter how the Dipper is oriented with respect to your northern horizon.
EarthSky community member Ken Christison captured these glorious star trails around Polaris, the North Star. This is the star around which the entire northern sky appears to turn.
The chart below shows the Big Dipper, Little Dipper and the star Polaris as you’ll see them in the north on July evenings. Polaris marks the end of the handle on the Little Dipper asterism, which is in the constellation Ursa Minor.
In other words, the Little Dipper is not the whole constellation, but just a noticeable pattern within the constellation Ursa Minor the Smaller Bear.
Vega and its constellation Lyra
Posted by Deborah Byrd in TONIGHT | July 8, 2020
Tonight, look eastward during the evening hours, and it’s hard to miss the season’s signature star formation, called the Summer Triangle. Its stars – Vega, Deneb and Altair – are the first three to light up the eastern half of sky after sunset, and their bright and sparkling radiance is even visible from light-polluted cities or on a moonlit night.
Try looking first for the most prominent star in the eastern sky, which is Vega in the constellation Lyra the Harp. Vega is blue-white in color. It’s sometimes called the Harp Star. And many people recognize its constellation, Lyra, as a triangle of stars connected to a parallelogram.
The constellation Lyra the Harp.
It’s hard to gauge the humongous size of the Summer Triangle by looking at our little chart. A 12-inch ruler, when placed at an arm’s length from your eye, spans the approximate distance from Vega to the star Altair. And an outstretched hand more or less fills the gap between Vega and Deneb.
More than any other month, July is the month of the Summer Triangle. At mid-northern latitudes, the Summer Triangle’s stars – as if a trio of school kids on vacation – stay out from dusk till dawn, dancing amid the stars of our Milky Way galaxy. As our Earth turns tonight, Vega, Deneb and Altair travel westward across the sky. The Summer Triangle shines high overhead in the middle of the night, and sparkles in the west as the rose-colored dawn begins to color the sky.
The Summer Triangle, photographed by Susan Jensen in Odessa, Washington.
Venus brightest, near Aldebaran, around July 10
Posted by Bruce McClure in TONIGHT | July 9, 2020
On July 10, 2020, the dazzling planet Venus reaches a big milestone in the morning sky, as this world displays its greatest illuminated extent. It’s around this time that Venus beams most brilliantly in our sky. What’s more, Venus is very near a bright star now, Aldebaran, the fiery Eye of the Bull in the constellation Taurus. So right now is a great time to look for Venus in the east before sunrise!
What is greatest illuminated extent for Venus? As you might know, Venus orbits the sun one step inward from Earth. Thus this inferior planet shows phases, much like the phases of the moon. Sometimes, as now, Venus’ day side is facing mostly away from Earth, and we see a crescent Venus. Venus’ great illuminated extent happens when the day side of Venus covers more square area on the sky’s dome than at any other time during a particular (morning or evening) apparition. More square area visible equals more brightness for Venus in our sky. Thus Venus is brightest around now.
And that is very bright indeed! Venus is always the 3rd-brightest celestial body to light up the heavens, after the sun and moon. At its brightest, as now, Venus shines about 2 1/2 times more brightly than at its faintest.
Venus is so bright that some people can see this world in a daytime sky with the unaided eye. Before dawn, Venus shines exceedingly brightly ahead of the coming sunrise. It’s accompanied by Aldebaran, the brightest star in Taurus. If, when you look, the dawn light has washed Aldebaran from view, aim binoculars at Venus; Aldebaran might pop into view nearby. Although Aldebaran ranks as a first-magnitude star – one of the sky’s brightest stars – it pales next to Venus, with Venus more than 100 times brighter than Aldebaran.
Click here for recommended almanacs; they can tell you when Venus rises into the morning sky.
You might think Venus appears most brilliant in our sky when its disk is most fully illuminated. Not so. If you were to observe Venus with the telescope at its greatest illuminated extent, you’d see that Venus’ disk is only a touch more than one-quarter illuminated by sunshine now. A full Venus is always on the far side of the sun from us, so its disk size at or near full phase always appears small to us on Earth. It’s only when we see Venus as a crescent – when Earth and Venus are on the same side of the sun – that this world is close enough to us to exhibit its greatest illuminated extent. At that juncture, Venus’ daytime side covers the greatest area of Earth’s sky.
Thus Venus’ greatest brilliancy in our sky depends on just the right combination of distance from Earth and phase visible from Earth.
As Venus comes closer to Earth in the evening sky, its phase shrinks but its disk size enlarges. The converse is also true. When Venus gets farther away from Earth in the morning sky, its phase increases but its disk size diminishes. Image via Statis Kalyvis
We refer you to the diagram below. Venus passed between the Earth and sun (at inferior conjunction) on June 3, 2020 and so entered Earth’s morning sky. Venus will shine in our morning sky for the rest of 2020 and finally transition back to the evening sky (at superior conjunction) on March 26, 2021.
The illustration below provides a bird’s-eye view of Earth and Venus in orbit, helping you see how and why Venus can transition from evening to morning sky. Because Venus orbits the sun inside Earth’s orbit, we can’t see Venus opposite (180 degrees) the sun in our sky (like the full moon). We can’t even see Venus 90 degrees from the sun (like the half-lit quarter moon). At most, Venus strays no farther than 47 degrees from the sun in our sky.
Earth and Venus orbit the sun counterclockwise as seen from the north of the solar system. Venus always reaches its greatest eastern (evening) elongation about 72 days before inferior conjunction and its greatest western (morning) elongation about 72 days after inferior conjunction. Venus exhibits its greatest illuminated extent – greatest brilliancy as seen from Earth – midway between a greatest elongation and inferior conjunction.
Venus reaches its greatest elongation in the evening sky about 72 days before inferior conjunction, and then reaches its greatest elongation in the morning sky some 72 days after inferior conjunction. If you look at Venus through a telescope at these times, you’ll see that its disk is about 50% illuminated by sunshine.
Venus exhibits its greatest illuminated extent about 36 days before – and after – inferior conjunction. Through the telescope, Venus appears about one quarter illuminated in sunshine at these times. Thirty-six days before inferior conjunction, it’s Venus’ brightest appearance in the evening sky; thirty-six days after inferior conjunction, it’s Venus brightest appearance in the morning sky.
Let the golden triangle help you to remember these Venus’ milestones. The two base angles equal 72o and the apex angle equals 36o. Quite by coincidence, Venus’ greatest elongations happen 72 days before and after inferior conjunction, and Venus’ greatest illuminated extent happens 36 days before and after inferior conjunction. See the diagram above of Venus’ and Earth’s orbits.
Venus, which is well-known for its 8-year cycles, returns to its greatest illuminated extent in the morning sky 5 times in 8 years. Eight years from now – July 10, 2020 – expect to see Venus at its brightest as the morning “star” and near the star Aldebaran on the sky’s dome.
The Golden Triangle, with the apex angle = 36o and base angles = 72o
Bottom line: Even though – as seen from Earth – Venus appears only slightly more than one-quarter illuminated on July 10, 2020, it is nonetheless shining at its brightest in our morning sky! Look east before sunup for Venus. The bright star nearby is Aldebaran.
Moon, Mars from midnight till dawn
Posted by Bruce McClure in TONIGHT | July 10, 2020
The bright planets Jupiter and Saturn light up your southeast sky at nightfall/early evening; but you have to stay up till around midnight, or later, to view the moon and the red planet Mars rising into your eastern sky on the night of July 10-11, 2020. Not a night owl? Then get up early instead, to see the moon and Mars much higher up in the July predawn/dawn sky. Seek first for the moon, and that brilliant nearby “star” on the mornings of July 11 and 12 will be the red planet Mars.
Although the moon will move away from Mars’ vicinity after a few more days, you should have little trouble finding Mars in the morning sky for months to come. Brilliant Mars rules over this realm of starry heavens, with no nearby bright stars to distract you from this fiery-red planet.
In the wee hours, just before dawn, you can actually see two worlds that are brighter than Mars: Venus, the brightest planet in the east, and Jupiter, the 2nd-brightest planet, in the southwest. Note that Mars is nowhere close to Venus or Jupiter on the sky’s dome, but is found roughly midway between these two brilliant orbs.
Venus lights up the eastern predawn/dawn sky in July 2020. If you’re up early enough, when the sky is still dark, look for the star Aldebaran pairing up with Venus on the sky’s dome.
Venus and Jupiter rank as the second and third brightest celestial objects to light up the heavens, respectively, after the sun and moon. Yet, Mars is getting brighter in our sky day and day, and will supplant Jupiter as the 4th-brightest celestial body in October 2020. But, for now, Jupiter is enjoying its moment of glory, as the king planet is shining at its brightest best for the year.
The moon travels in front of the constellations of the zodiac in an eastward direction, at the rate of about 13 degrees per day. To know which way is eastward, simply look at the waning moon in your morning sky. The lit side of the waning moon always points eastward (in the direction of sunrise). So as the moon leaves Mars’ section of the zodiac, it’ll be heading for Venus, to rendezvous with the queen planet in about a week.
Watch for the waning crescent moon to sink downward day by day during the third week of July 2020. Read more.
Jupiter predominates over the July evening sky, staying out from dusk till dawn. Venus, the sky’s brightest planet, lords over the eastern predawn/dawn sky. But on the mornings of July 11 and 12, the moon joins up with the 3rd-brightest planet, Mars, to showcase the red planet roughly midway between Venus and Jupiter.
Deneb and Cygnus the Swan
Posted by Deborah Byrd in TONIGHT | July 12, 2020
Tonight’s chart has you looking eastward at the famous Summer Triangle. Today, notice the star Deneb, the northernmost star in the Summer Triangle. Its constellation is Cygnus the Swan. In a dark country sky, you can see that Cygnus is flying along the starlit trail of the summer Milky Way.
The photo below is from Annie Lewis in Spain. She solved the problem of picking out the Summer Triangle from among many stars in the night sky by looking for the Triangle in the east soon after sunset. These three stars are, after all, among the brightest in the sky.
EarthSky Facebook friend Annie Lewis in Madrid, Spain, captured this photo of the Summer Triangle shortly after nightfall on a summer night. In fact, she said, the only stars visible to the unaided eye when she took the photo were the three in the Triangle. But her camera knew better. Thanks, Annie.
If it’s darker out, you might recognize the Summer Triangle by noticing that there is a cross within the Triangle. The constellation Cygnus is that cross. In fact, the constellation Cygnus is sometimes called the Northern Cross.
Okay, I’ve given you a lot of names here: Summer Triangle, Cygnus, Northern Cross.
Just remember, the constellation Cygnus the Swan contains the Northern Cross. The Cross is – more or less – just another way to see the Swan. The Northern Cross is what’s called an asterism, or recognizable pattern within a constellation. In this case, the pattern is the whole constellation, pretty much. At least, I never see them any differently.
Except for one thing. Deneb is at the top of the Cross, but at the tail of the Swan (the star name “deneb” always means “tail”). The little star Albireo is at the head of the Swan, but at the base of the Cross. Whew!
Jupiter at opposition on July 13-14
Posted by Deborah Byrd in TONIGHT | July 13, 2020
On the night of July 13-14, 2020, our planet Earth flies between the sun and the outer planet Jupiter. Our faster motion places Jupiter – largest world in our solar system, and an exceedingly bright planet in our sky – opposite the sun about once each year. In other words, Jupiter is now rising in the east as the sun is setting below the western horizon. Astronomers call this event an opposition of Jupiter.
Jupiter reaches opposition on July 14, at 8:00 UTC. At United States’ time zones, that’s 4 a.m. Eastern Time, 3 a.m. Central Time, 2 a.m. Mountain Time, 1 a.m. Pacific Time, 12 midnight July 13-14 Alaskan Time, and on July 13, at 10 p.m. Hawaiian time.
Opposition marks the middle of the best time of year to see a planet. That’s because it’s when the planet is up all night and generally closest for the year (the exact date of Jupiter at its closest this year is June 15).
View at EarthSky Community Photos. | Eli Frisbie created this composite image from photos gathered on June 6, in Eagle Mountain, Utah. He wrote: “The Milky Way shines over a country road with light pollution in the distance. The bright ‘star’ to the right of the Milky Way is the planet Jupiter. The slightly less-bright star to the upper left is the planet Saturn.” Thank you, Eli!
Jupiter is now in the east around sunset. It climbs highest in the sky at midnight (that is, midway between sunset and sunrise). It sets in the west around sunrise.
Jupiter is always bright; it’s the largest planet in our solar system. It shines more brightly than any star in the evening sky. At this 2020 opposition, Jupiter shines close to the planet Saturn, in front of the constellation Sagittarius. There’s no way to mistake Saturn for Jupiter, though, because dazzling Jupiter outshines this 1st-magnitude star by some 14 times. With the exception of the sun and moon, only Venus – the brightest planet, now low in the east before sunrise – outshines Jupiter.
Up before daybreak? The illuminated side of the waning moon points at Venus, the sky’s brightest planet.
Try catching both Venus and Jupiter at morning dawn. Venus will be blazing low in the east while Jupiter is sitting low in the west. You’ll need an unobstructed horizon in both directions to see both Venus and Jupiter before sunrise.
Jupiter (red) completes one orbit of the sun (center) for every 11.86 orbits of the Earth (blue). Our orbit is smaller, and we move faster! Animation via Wikimedia Commons.
Jupiter, as it reaches its 2020 opposition, shines in front of the constellation Sagittarius the Archer and will remain in that constellation till late December 2020. Next year, in 2021, Jupiter will be in front of the constellation when it comes to opposition.
Ophiuchus isn’t the world’s brightest constellation. Maybe you’ve never taken the time to pick out its stars. If you want to do so, be sure to look in a dark sky. The chart below might help:
Let Jupiter be your guide to the constellation Ophiuchus in 2019. Next year, in 2020, Jupiter will serve as your guide to the constellation Sagittarius. Sky chart via the IAU.
Jupiter comes to opposition roughly every 13 months. That’s how long Earth takes to travel once around the sun relative to Jupiter. As a result – according to our earthly calendars – Jupiter’s opposition comes about a month later each year.
Last year – in 2019 – Jupiter’s opposition date was June 10.
Next year – in 2021 – it’ll be August 19.
Jupiter isn’t a rocky planet like Earth. It’s more like a failed star, not massive enough or hot enough inside to spark thermonuclear fusion reactions, but some 2.5 times more massive than all the other planets in our solar system combined. Jupiter shows us nature magnified!
There’s a NASA spacecraft orbiting Jupiter now. The Juno spacecraft’s orbit carries it low over Jupiter’s poles, providing never-before-seen glimpses of the giant planet’s polar regions. NASA has asked citizen scientists to help process Juno’s images. NASA explained at its JunoCam image processing gallery:
We invite you to download [the raw images], do your own image processing, and we encourage you to upload your creations for us to enjoy and share. The types of image processing we’d love to see range from simply cropping an image to highlighting a particular atmospheric feature, as well as adding your own color enhancements, creating collages and adding advanced color reconstruction.
Here’s a recent image, processed by a citizen scientist:
Bottom line: Look for Jupiter on the night of July 13-14, 2020, as this world comes to opposition, the point opposite the sun in our sky. You’d need some 80 Jupiters – rolled into a ball – to be hot enough inside for thermonuclear reactions … for Jupiter to shine as stars do. Yet on this May night – as Jupiter rises opposite the sun – you can imagine it beaming down on us as a tiny sun all night long.
Moon, Venus beautiful before sunrise
Posted by Bruce McClure in TONIGHT | July 15, 2020
Before daybreak these next several mornings – July 16, 17, 18 and 19, 2020 – look eastward to enjoy an eyeful of the waning crescent moon and the dazzling planet Venus. These two brilliant worlds will be hard to miss, as the moon and Venus rank as the 2nd-brightest and 3rd-brightest celestial bodies, respectively, after the sun. Some people might even see Venus after sunrise.
If you’re up before dawn, you can actually catch three more bright planets. The second brightest planet – Jupiter – is out from dusk till dawn, and sits low in the southwest sky before daybreak. Saturn is found a short hop above Jupiter in the morning sky. Mars, on the other hand, is much higher up, roughly midway between Venus and Jupiter.
For brilliant brilliant planets light up the July morning sky. Venus, the brightest, shines in your eastern sky, whereas Jupiter, the 2nd-brightest, lords over the southeast sky. Look for Saturn close to Jupiter, and for Mars roughly midway between Venus and Jupiter.
Far and away, Mercury poses the biggest challenge, and you may need binoculars to spot the solar system’s innermost planet in the glow of dawn. But if you’re game, let the lit side of the lunar crescent these next few mornings serves as your arrow in the sky, pointing to Mercury’s approximate rising spot on the horizon. On July 19, the old whisker-thin lunar crescent passes to the north of Mercury.
Another thing to look for is the soft glow of earthshine illuminating the dark or night side of the moon. Earthshine is twice-reflected sunlight with the Earth reflecting sunlight to the moon, and the moon, in turn, reflecting sunlight back to Earth.
These next several mornings – July 16, 17 and 18, 2020 – enjoy the beautiful presence of the waning crescent moon, the queen of the night, with Venus, the queen planet.
Altair and Aquila the Eagle
Posted by Deborah Byrd in TONIGHT | July 18, 2020
In the east after dark on these July evenings, look near the horizon for Altair, the brightest star in the constellation Aquila the Eagle. This is the bottom star of the Summer Triangle; that is, it’s the last of these three bright stars to ascend over the horizon. This star is 16.7 light-years from our sun and is one of the closest stars visible to the unaided eye.
You will recognize Altair by the two fainter stars on either side of it. In her classic book “The Friendly Stars” (1907), Martha Evans Martin described the three this way:
Then there comes a soft June evening, with its lovely twilight that begins with the last song of the woodthrush and ends with the first strenuous admonitions of the whippoorwill; and, almost as if it were an impulse of nature, one walks to the eastern end of the porch and looks for Altair. It is sure to be there smiling at one just over the tree-tops, with a bright companion on either side, the three gently advancing in a straight line as if they were walking the Milky Way hand in hand and three abreast.
And indeed the Great Rift of the summer Milky Way passes through the Summer Triangle, between the stars Vega and Altair. In dark skies in June, July and August, you can see rich star fields with your binoculars on both sides of the Great Rift.
In modern western culture, Altair is probably best known for being the home star system of the aliens in the 1956 science fiction film “Forbidden Planet”. But in Asian cultures, Altair and the star Vega figure in one of the most beautiful of all stories of the night sky. In Japan, for example, Vega is sometimes called Tanabata (or Orihime), a celestial princess or goddess. She falls in love with a mortal, Kengyu (or Hikoboshi), represented by the star Altair. Read the rest of the story here.
The whole Summer Triangle area is great to observe with binoculars or in dark skies with just your eyes. If you like finding hidden pictures, get set to find a Coathanger, the North American Nebula (NGC7000) and the Ring Nebula (M57).
Great Rift of Milky Way passes through the constellation Cassiopeia and the Summer Triangle.
Summer Triangle and smallest constellations
Posted by Deborah Byrd in TONIGHT | July 19, 2020
The Summer Triangle is not a constellation but a large asterism consisting of three bright stars in three separate constellations. These stars are Vega, Deneb and Altair. If you can find the Summer Triangle, you can use it to locate three of the sky’s smallest constellations: Vulpecula the Fox, Delphinus the Dolphin and Sagitta the Arrow. All three would be impossible to see from the city, but they’re lots of fun to see in a dark sky.
How can you find them? Look at the detailed chart below, and try picking out Vega, Deneb and Altair. Notice the large triangle they make if you draw lines between them. This triangle pattern – which is easily found in the sky on Northern Hemisphere summer evenings – is the Summer Triangle.
Now – still using the chart at the bottom of this post – or maybe after purchasing this awesome constellation chart from the store at Skyandtelescope.org – look within and around the Summer Triangle for Delphinus, Sagitta and Vulpecula.
Delphinus is a truly delightful little constellation that really resembles a dolphin leaping among the waves. Delphinus is one of the earliest constellations, first catalogued by the Greek astronomer Ptolemy in the second century. Sometimes, Delphinus is said to be the Dolphin that carried a Greek poet – Arion – safely away from his enemies. Other times, this sky Dolphin is said to represent the dolphin sent by the sea god Poseidon to find Amphitrite, the Nereid he wanted to marry.
Sagitta – the third smallest constellation in our sky – is near Vulpecula on the sky’s dome. Its name means “the arrow” in Latin. If you look for Sagitta, you’ll see why. This little star pattern does have a shape reminiscent of an arrow. Sagitta is also one of the earliest constellations, named by Ptolemy in the second century. Sagitta is sometimes said to be an arrow shot from the bow of Hercules, a mythological hero and god.
Vulpecula means “the little fox” in Latin, and it’s the hardest to find of these three small constellations because it lacks a distinctive shape. Vulpecula is a relatively new constellation, introduced by the Polish astronomer Johannes Hevelius in the late 17th century. If you’re up for a binocular challenge, also try finding the Coathanger asterism in Vulpecula.
View larger. | Once you’re familiar with the Summer Triangle, star-hop from there to the nearby small constellations. Chart via IAU and Sky & Telescope (Roger Sinnott & Rick Fienberg)/Wikimedia Commons.
We go between Saturn and the sun July 20
Our planet Earth flies this week between Saturn and the sun, bringing Saturn to what astronomers call opposition. Opposition is a big milestone each year for observing the ringed planet Saturn, or any superior planet (planet orbiting the sun outside Earth’s orbit). When we fly between a superior planet and the sun, the planet is generally closest to Earth and brightest for that year. Saturn’s opposition comes on July 20, 2020, at 22 hours UTC.
That is 7 p.m. ADT, 6 p.m. EDT, 5 p.m CDT, 4 p.m. MDT, 3 p.m. PDT, 2 p.m. Alaskan Time and 12 noon Hawaiian Time; click here to translate UTC to your time.
Jupiter reaches opposition on July 14, 2020, and about a week later, Saturn sweeps to opposition on July 20, 2020. Look first for dazzling Jupiter, and that nearby golden “star” a short hop to the east of Jupiter is actually Saturn. In July 2020, these two worlds climb highest up for the night around midnight (middle of the night). A month from now, the dynamic twosome will be highest up for the night around mid-evening.
And don’t worry about exact times too much. Just know that – around now – Saturn is more or less opposite the sun in Earth’s sky, rising in the east around sunset, climbing highest up for the night around midnight and setting in the west around sunrise. When opposite the sun, Saturn is visible all night and at its best! What’s more, the moon turns new on Saturn’s opposition date (July 20, 2020), guaranteeing moon-free skies on Saturn’s special day.
The brightness of Saturn at opposition is partly determined by the orientation of its rings with respect to Earth. Image via Hubble Heritage.
You need a telescope to see Saturn’s rings. But Saturn is always visible to the eye as a golden “star.”
Although Saturn comes closest to Earth for the year about 5 hours after it reaches opposition, the ringed planet comes nowhere as close to Earth as the NASA illustration at the very top of this post might lead you to believe. At present, Saturn lies some 10 times the Earth’s distance from the sun, and nine times the Earth-sun distance from Earth. Astronomers refer to one Earth-sun distance as an astronomical unit, or AU. Saturn is now 10 AU from the sun, and 9 AU from us. Heavens Above gives information about the present distances of the planets from the sun and Earth.
Contrasting the size of Saturn and its rings with our planet Earth.
Also, don’t assume Saturn’s presence in the nighttime sky is a one-night-only event. The ringed planet will be in good view in the evening sky throughout August, September and October 2020. You can recognize Saturn because it’s in your southeast sky at dusk and nightfall, a short hop to the east of the dazzling king planet Jupiter. Saturn and Jupiter will stay close together on the sky’s dome and remain fixtures of the evening sky for the rest of this year. All the while, golden Saturn shines in front of the constellation Sagittarius, to the east of Jupiter and the Teapot asterism.
Our fast movement in orbit brings Earth between Saturn and the sun every year – or, more precisely, about two weeks later every year. Five years ago, for instance, Saturn’s opposition happened on May 23, 2015. In 2016, it was June 3. In 2017, it was June 15. In 2018, June 27, and in 2019, it was July 9. If you recognize this golden world tonight or later this month, you’ll also enjoy it throughout the Northern Hemisphere summer, or Southern Hemisphere winter.
If you had a bird’s-eye view of the solar system today, you’d see our planet Earth passing in between the sun and Saturn. You’d see the sun, Earth, and Saturn lining up in space. But not for long. Earth moves in orbit at 18 miles (29 km) per second in contrast to about 6 miles (9 km) per second for Saturn. Soon, we’ll be pulling ahead of Saturn in the race of the planets.
The planets that orbit the sun inside of Earth’s orbit – Mercury and Venus – can never be at opposition. Only the planets that orbit the sun beyond Earth’s orbit – Mars, Jupiter, Saturn, Uranus, Neptune, and the dwarf planet Pluto – can ever reach opposition, that is, appear opposite the sun in Earth’s sky.
All the planets farther from the sun reach opposition every time our swifter-moving planet sweeps between the sun and these superior planets – planets that orbit the sun outside of Earth’s orbit. Mars returns to opposition every other year. Jupiter’s opposition happens about one month later each year, whereas Saturn’s opposition occurs about two weeks later yearly. The farther that a planet resides from the sun, the shorter the period of time between successive oppositions.
Saturn, the sixth planet outward from the sun, is the most distant world that’s easily visible to the unaided eye. Telescopes revealed its rings in the 17th century. Spacecraft in the 20th century revealed that what we thought of as three rings around Saturn to be thousands of thin, finely detailed rings – made of tiny chunks of ice. Saturn also has 62 moons with confirmed orbits. Only 53 of Saturn’s moons have names, and only 13 have diameters larger than 50 kilometers (about 30 miles).
Watch the moon shed its shadow
Posted by Bruce McClure in TONIGHT | July 21, 2020
The mythologist Joseph Campbell poetically stated, “The power of life causes the snake to shed its skin, just as the moon sheds its shadow.” When the moon turned new on July 20, 2020, the moon’s shadowed side totally faced Earth, while its illuminated side totally faced the sun. The moon is said to be reborn whenever the new moon transitions out of the eastern morning sky and into the western evening sky.
Watch for the young moon to shed its shadow and to grow in radiance over the days ahead. When the newly-born moon makes its initial appearance in the west after sunset July 21, 2020, the lunar disk will be almost totally covered over in shadow. Only the slightest sliver of sunlight lighting up the far edge of the moon will visible to the watchful eye. Day by day, as the moon grows in age, the moon’s shedding shadow will give way to increasing luminosity.
Multazam Yazid captured the extremely young waxing moon on July 24, 2017 from Telok Kemang Observatory, Port Dickson, Malaysia. He was using a Takahashi TOA-150 telescope and a DSLR Canon 550D.
It’ll be easy to miss the moon after sunset July 21. For most of the world, the pale, whisker-thin lunar crescent will follow the sun beneath the horizon before nightfall (or before the end of astronomical twilight). If you’re up for the challenge, try catching the young moon with either the unaided eye or binoculars. Day by the day, a wider and brighter crescent will appear higher up at sunset, and will stay out longer after dark.
While you’re at it, enjoy the entrancing beauty of earthshine softly illuminating the nighttime side of the moon. Earthshine, which is most readily visible at the moon’s crescent phase, counts as twice-reflected sunlight, with sunlight bouncing from Earth to the moon, and then from the moon back to Earth.
Ken Christison caught a very young moon, with its dark side all aglow in earthshine, on March 31, 2014, the day after a new moon.
In space, the moon is actually half-illuminated in sunshine and half-covered over in (its own) shadow. Like our planet Earth, the moon has a day side and a night side. The portion of the moon’s day side or night side that is visible from Earth, however, depends on the ever-changing position of the moon relative to the sun and Earth. At new moon – when the moon swings in between the Earth and sun – the moon’s nighttime side totally faces Earth; at full moon – when the moon is opposite the sun in Earth’s sky – the moon’s daytime side totally faces Earth.
A bird’s-eye view of the north side of the moon’s orbital plane find the moon circling Earth in a counterclockwise direction. At new moon, when the moon is between the Earth and sun, the moon’s nighttime totally side faces Earth. At full moon, when the moon is opposite the sun in our sky, the moon’s daytime side totally faces Earth.
When the moon, Earth and sun make a 90 degree or right angle in space – with Earth at the vertex of this angle – then it’s either a first quarter or last quarter moon. At quarter moon, the eye perceives the moon as half-illuminated in sunshine and half-covered in the moon’s own shadow.
As the moon orbits Earth, its changing geometry with respect to the sun produces the characteristic phases. This composite image is a mosaic made from 25 individual photos of the moon and illustrates its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. Photo copyright Fred Espenak.
Because the moon moves eastward (away from the setting sun) at the rate of about 12 degrees per day, watch for the young moon to shed its shadow as it waxes from new moon to full moon during the new couple of weeks.
Go someplace dark and watch meteors!
Posted by Bruce McClure in TONIGHT | July 24, 2020
Tonight – July 24, 2020 – and in the coming nights, treat yourself to one of nature’s spectacles. Every year, people look forward to the August Perseid meteor shower. And it’s wonderful, with regular rates of about 60 meteors per hour at its peak. The Perseids are gearing up even now, so if you go outside between midnight and dawn tonight or this weekend, you might see a few. But there’s another meteor shower happening now, too. It’s the Delta Aquarid meteor shower.
The Delta Aquarids don’t have as definite a peak as the Perseids. Instead, the shower produces a steady supply of meteors for some weeks in late July and early August. Tonight – or this weekend – may present a good time to watch because the moon is in a waxing crescent phase. That means the moon now sets in early evening. In other words, we have deliciously dark skies for watching the Delta Aquarids, which are at their best in dark hours before dawn.
These meteors are beautiful! See the photo above? Kelly Dreller in Lake Havasu City, Arizona caught this meteor in late July of 2016.
Tonight, or this weekend – under a dark sky, between midnight and dawn – you might see as many as 10 meteors per hour. Most will be somewhat faint, so be sure to find a dark sky! Although the forecast calls for the peak to come during the predawn hours on July 28, you might see just as many meteors in the predawn sky on Saturday, July 25, and Sunday, July 26. In late July and the first week of August 2020, moonlight will become more of a factor.
Radiant point of Delta Aquarid meteor shower. Click here for a post on how to find it in your sky. The Delta Aquarid radiant point is close to the ecliptic, or sun’s path across our sky. If you trace the paths of a Delta Aquarid meteor backwards, you’d find the star Delta Aquarii – also called Skat – nearly coinciding with the radiant.
Radiant point of Perseid meteor shower. You can tell a Perseid meteor from a Delta Aquarid, because the showers have 2 different radiant points; in other words, the meteors radiate from 2 different directions in the sky. Here’s the Perseid radiant, rising in the northeast around midnight.
The Perseid shower is expected to produce the greatest number of meteors on the night of August 11-12 or 12-13, 2020. However, the rather wide waning crescent moon may somewhat obtrude on this year’s Perseids.
You can try watching the Perseids in moonlight. You’ll definitely see a few of the brighter ones, if you do. But righ tnow might be a better time to watch meteors in 2020, before moonlight becomes too overpowering. The Perseids are known to rise to a peak gradually, so they’ll be increasing in numbers every night over the coming weeks – although, at the same time, the moon will be increasing in brilliance and edging into the post-midnight sky.
Meanwhile, the Delta Aquarids will be raining down steadily, night after night.
Yes, you can watch from the South Hemisphere, too! The Delta Aquarids, especially, are a good shower for you. The Delta Aquarids fall more abundantly in the Southern Hemisphere, featuring perhaps 15 Delta Aquarid meteors per hour in an inky dark sky. All around the world, the radiant of the shower climbs highest up for the night around 2 to 3 a.m. local time (3 to 4 a.m. local Daylight Time), but the radiant soars way higher in the Southern Hemisphere than at comparable latitudes in the Northern Hemisphere.
Outside on the evening of July 27, and notice a bright “star” near the moon? It’s not a star. It’s the planet Jupiter. The moon and Jupiter will be even closer on July 28. The nearby bright star is Spica in the constellation Virgo the Maiden.
Bottom line: Given dark skies, you might see as many as 10 to 15 meteors per hour this weekend, as you’ll have more moon-free time for viewing meteors than in late July and the first week of August 2020.
Moon and Spica on July 25 and 26
Posted by Bruce McClure in TONIGHT | July 25, 2020
On July 25 and 26, 2020 – as the setting sun closes the curtains on the day, and the darkening skies bring out a myriad of far-off suns – let the moon introduce you to a special star. The bright star close to the moon on these dates is none other than Spica, the sole 1st-magnitude star in the constellation Virgo the Maiden.
The much brighter starlike object in the southeast sky (outside the sky chart at the top of this post) is the giant planet Jupiter. Jupiter, the fifth planet outward from the sun, shines rather close to the ringed planet Saturn.
The sky chart at the top of this post is set for North America. If you live in the Earth’s Eastern Hemisphere, the moon will appear a little farther west of where it does on this chart. If you live in Hawaii, the moon will be offset somewhat in the opposite direction. Also, the moon on the sky chart appears larger than it does in the real sky.
SKY CHART OF ANTARES?
SKY CHART OF JUPITER & SATURN (NEEDS TO BE MADE)
No matter where you live, the moon continually moves eastward in front of the backdrop stars of the zodiac at the rate of about one-half degree per hour. For a convenient measuring stick, the moon’s angular diameter approximates one-half degree of sky. So the moon moves its own diameter eastward per hour or about 13 degrees (26 moon diameters) eastward per day. Look for the moon to snuggle up more closely with Spica as darkness falls on July 9.
When the moon is no longer close to Spica, you might find it helpful to “star-hop” to Spica instead, as shown on the sky chart below:
If you live in the Northern Hemisphere, and you’re familiar with the Big Dipper, you can count on this famous pattern of stars to guide you to Spica. Simply extend the Big Dipper handle to arc to the brilliant yellow-orange star Arcturus and then to spike Spica, a blue-white gem of a star. If you have difficulty discerning stellar color with the eye alone, try your luck with binoculars.
Bottom line: Let the moon guide you to Spica on July 25 and 26, 2020, and then use the Big Dipper to locate Virgo’s brightest star, after the moon’s flirtation with Spica ends.
Moon’s near side is its dark side
Posted by Bruce McClure in TONIGHT | July 27, 2020
Tonight, while the moon is a few days shy of meeting up with the red supergiant star Antares, let’s see if we can make out the dark areas on tonight’s moon, which is at or somewhat past its half-illuminated first quarter phase at nightfall July 27, 2020. These smooth, low-lying lunar plains are called maria, the plural for the word mare, the Latin word for sea. You should be able to see the darkened portions on the moon with the eye alone. The dark maria on the moon’s near side – the solidified remnants of ancient lunar seas of molten magma – make the near side of the moon reflect less light than the far side, which has fewer maria.
So, in terms of albedo or reflectivity, the moon’s dark side is its near side.
Find out the moon’s present phase via Heavens-Above
If you’d like to scrutinize the maria more closely, use binoculars or a telescope. Remember, the view will be better around the time of sunset or early dusk – before the dark of night accentuates the moon’s harsh glare.
In times past, astronomers really thought the dark areas contrasting with the light-colored, heavily-crated highlands were lunar seas. In some ways they were correct, except that these were seas of molten magma instead of water. Now solidified, this molten rock came from volcanic eruptions that flooded the lunar lowlands. However, volcanic activity – at least from basaltic volcanoes – is now a thing of the moon’s past.
For the most part, lunar maria are found on the near side of the moon. In this respect, that makes the near side – not the far side – the dark side of the moon.
Near side of the moon.
Far side of the moon via Wikimedia Commons.
Maria cover about 30 percent of the near side but only 2 percent of the far side. The reason for this is not well understood, but it has been suggested that the crust on the moon’s far side is thicker, making it more difficult for magma to reach the surface.
The lighter-colored highland regions of the moon are composed of anorthosite, a certain kind of igneous rock. On Earth, anorthosite is uncommon, except for in the Adirondack Mountains and the Canadian Shield. For this reason, people in this part of the world like to fancy that the moon originated from their home turf.
The prevailing theory states that the moon was formed when a Mars-sized object crashed into the Earth, creating a ring of debris that eventually condensed into the moon. I suppose time will tell whether this explanation for the moon’s origin is true or false.
Bottom line: Strange as it may seem, the moon’s dark side is its near side. By that we mean the near side of the moon reflects less light – due to a collection of dark, low-lying lunar plains that are the solidified remnants of ancient seas of molten magma.
Orion the Hunter returns before dawn
Posted by Deborah Byrd in TONIGHT | July 30, 2020
Around late July or early August, if you’re up early and have an unobstructed view to the east, be sure to look in that direction in the hour before dawn. You might find a familiar figure – a constellation that always returns to the sky around this time of year. It’s the beautiful constellation Orion the Hunter – recently behind the sun as seen from our earthly vantage point – now ascending once more in the east before sunrise.
The Hunter appears each northern winter as a mighty constellation arcing across the south during the evening hours. Many people see it then, and notice it, because the pattern of Orion’s stars is so distinctive.
But, at the crack of dawn in late summer, you can spot Orion in the east. Thus Orion has been called the ghost of the shimmering summer dawn.
The Hunter rises on his side, with his three Belt stars – Mintaka, Alnitak and Alnilam – pointing straight up.
The constellation Orion as viewed at morning dawn in early August. Image via Flickr user Michael C. Rael.
Also, notice the star Aldebaran in the constellation Taurus the Bull. Aldebaran is the brightest star in Taurus the Bull. It’s said to be the Bull’s fiery red eye. See the V-shaped pattern of stars around Aldebaran? This pattern represents the Bull’s face. In skylore, Orion is said to be holding up a great shield … fending off the charging Bull. Can you imagine this by looking at the chart at top? It’s easy to imagine when you look at the real sky before dawn at this time of year.
Bottom line: The return of Orion and Taurus to your predawn sky happens around late July or early August every year. In the Northern Hemisphere, Orion is sometimes called the ghost of the summer dawn.
Moon, 2 bright planets at nightfall
Posted by Bruce McClure in TONIGHT | July 31, 2020
As darkness falls in late July/early August 2020, let the bright moon introduce you to the king planet Jupiter and the ringed planet Saturn. From around the word on July 31, look for these two worlds beneath the moon, starting at nightfall. Although the glare of the almost-full waxing gibbous moon will wash many stars from the blackboard of night, Jupiter and Saturn should be bright enough to withstand the drenching moonlight.
Far and away, Jupiter is the brighter of these two worlds, beaming some 14 times more brilliantly than Saturn does. Even so, Saturn is respectably bright, shining on par with the sky’s brightest stars.
Because the Earth spins from west-to-east on its rotational axis, the moon, you can expect the moon, Jupiter and Saturn to travel across the night sky from east to west – just like the sun does during the day. These next few days, these three worlds – the moon, Jupiter and Saturn – climb up high around midnight, and then set beneath the southwest horizon before the onset of dawn.
Relative to the backdrop stars and planets of the zodiac, the moon moves eastward at the rate of about 1/2 degree (the moon’s own angular diameter) per hour, or around 13 degrees eastward per day. On July 31, you’ll see the moon to the west of Jupiter and Saturn. But the moon, always moving eastward in its orbit, will go past Jupiter and then Saturn in early August 2020.
More precisely, the moon will swing 1.5 degrees south of Jupiter on August 1, 2020, at 23:30 Universal Time (UTC) and then 2.3 degrees south of Saturn on August 2, 2020, at 13:17 UTC. Depending on where you live worldwide, the moon may or may not have its conjunction with either planet during the nighttime hours.
No mater where you live, look for the moon to pass by Jupiter and Saturn over the next several days. If you wish to check out the moon’s present position in front of the constellations of the zodiac, click on Heavens-Above.
Although the moon sweeps close to Jupiter and Saturn on the sky’s dome, the moon and these planets don’t come close together in actual space. The moon, our nearest celestial neighbor, resides about 238,000 miles (483,000 km) away from Earth. Jupiter lies way beyond the moon, somewhere around 16,000 times the moon’s distance from Earth; and Saturn, the farthest world that’s easily visible to the unaided eye, is well over twice Jupiter’s distance from Earth.
Find out the moon’s present distance from Earth (in miles, kilometers or astronomical units) via The Moon Tonight
Because the moon appears full for two to three nights in a row, it is hard to tell when the moon turns exactly full just by looking at it. But the upcoming full moon won’t turn full until after its encounter with Jupiter and Saturn:
August 1, 2020 at 23:30 UTC: Moon 1.5 degrees south of Jupiter
August 2, 2020 at 13:17 UTC: Moon 2.3 degrees south of Saturn
August 3, 2020 at 15:59 UTC: Full moon
The oppositions of Jupiter and Saturn both happened in July 2020, on July 14 and July 20, respectively. Therefore, the August full moon will occur after it meets up meets up Jupiter and Saturn.
On the other hand, the previous full moon on July 5, 2020, took place before the oppositions of Jupiter and Saturn. Therefore in July 2020, the moon turned full before its monthly rendezvous with Jupiter and Saturn.
In late July/early August 2020, let the moon show you the king planet Jupiter and the ringed planet Saturn on the sky’s dome. Jupiter and Saturn will adorn the eve