Some L-O-V-E on the Moon, which will Dance with Prominent Planets, Venus and Mars are Bright at Night, and Late Summer Stars are Colourful!

This amazing photograph by Sergio Scauso of Cordoba, Argentina shows the moon occulting Mars on August 9, 2020. NASA APOD for August 15, 2020. Since the moon travels within the same band of sky surrounding the ecliptic that the planets do, its large angular size allows it to pass in front of the planets from time to time.

Hello, late-August Stargazers!

Here are your Astronomy Skylights for the week of August 23rd, 2020 by Chris Vaughan. Feel free to pass this along to your friends and send me your comments, questions, and suggested topics. You can also follow me on Twitter as @astrogeoguy! Unless otherwise noted, all times are expressed in Eastern Time. To subscribe to these emails please click this MailChimp link.

I can bring my Digital Starlab portable inflatable planetarium to your school or other daytime or evening event, or teach a session online. Contact me through AstroGeo.ca, and we’ll tour the Universe, or the Earth’s interior, together!

This is the best week of the month to look our beautiful natural satellite after dinner – and it will dance with gas giant planets at week’s end. Mars is brightening, Mercury returns to view after sunset – barely, and Venus blazes away before dawn. Here are your Skylights!

The Moon – Now with an X and L-O-V-E!

This will be a fantastic week to enjoy views of the moon all around the world. Our beautiful natural satellite will be filling up with light each night as it draws away from the sun – first in the western sky during early evening, and then in the south, where it will dance with the two bright planets there nearly all night long on the coming weekend. Practicing on the moon is the best way to learn how to aim and focus your telescope, and to see how the different eyepieces work.

The curved, pole-to-pole terminator boundary that divides the moon’s lit and dark hemispheres shows where the sun is rising on the moon. The near-horizontal sunlight arriving there bathes peaks and crater rims in bright light and casts long shadows west of them. Every little bump is enhanced by that lighting – and with no atmosphere to scatter light, the contrast is dramatic. Even better – new regions are highlighted each night, or even hour-by-hour. Watching dark craters fill up with light is particularly interesting – and kids can reproduce the effect at home using bowls or pots and a flashlight in a dark room.

Tonight (Sunday) and tomorrow night, the crescent moon will sit among the moderate-brightness stars of Libra (the Scales). The moon will officially reach its first quarter phase just before 2 pm EDT on Tuesday. Because the moon has completed the first quarter of its orbit around Earth, the relative positions of the Earth, sun, and moon cause us to see it half-illuminated – on its eastern side. At first quarter, the moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. Look for it! On Tuesday night, the moon will shine a palm’s width above the bright red star Antares and the three little white stars that mark the scorpion’s claws, Acrab, Dschubba, and Fang (otherwise known as Beta, Delta, and Pi Scorpii).

Several times a year, for a few hours near its first quarter phase, a feature on the moon called the Lunar X becomes visible in strong binoculars and backyard telescopes – and this month it will occur on Tuesday night! When the rims of the craters Parbach, la Caille, and Blanchinus are illuminated from a particular angle of sunlight, they form a small, but very obvious X-shape. The phenomenon called is pareidolia – the tendency of the human mind to see familiar objects when looking at random patterns. The Lunar X is located near the terminator, about one third of the way up from the southern pole of the Moon (at lunar coordinates 2° East, 24° South). The prominent round crater Werner sits to its lower right.

On Tuesday evening, August 25, the Lunar X is predicted to peak in intensity at about 10 pm EDT (or 02:00 Greenwich Mean Time on Wednesday) – but the phenomenon will be visible for approximately two hours on either side of that time. This event should be visible anywhere on Earth where the moon is shining in a dark sky during that time window. Simply adjust for your difference from the Eastern Time zone. For the Great Lakes Region, the Moon will be positioned low in the southwestern sky.

At the same time, you can look for the Lunar V and the Lunar L. The “V” is produced by the small crater Ukert when combined with some ridges to the east and west of it. It is located a short distance above the moon’s equator at lunar coordinates 1.5° East, 8° North. For a further challenge, see if you can see the letter “L” down near the moon’s southern pole. Its position is to the southwest of three prominent and adjoining craters named Licetus, Cuvier, and Heraclitus, which combine to form a Mickey Mouse’s head shape. Some people claim they can see a letter-E on the moon during the Lunar X period, too. Then, by picking a round crater along the terminator to serve as the “O”, you can spell L-O-V-E! Let me know if you see them.

On Wednesday and Thursday night, the now gibbous moon (i.e., more than half-illuminated) will pass through Ophiuchus (the Serpent-Bearer) and land above the Teapot-shaped asterism of Sagittarius (the Archer).

The moon’s monthly visit with the gas giant planets will begin on Friday night. In the southern sky on Friday evening, the waxing gibbous moon will take up a position just two finger widths below (or 2 degrees to the celestial south of) the bright planet Jupiter – with Saturn off to their left (east). The moon and Jupiter will both fit within the field of view of binoculars – allowing you to add Jupiter’s four moons to your view (two on either side of Jupiter). During the rest of the night, the diurnal rotation of the sky will lift the moon to Jupiter’s left by the time they set at about 2:30 am local time. By midnight, the grouping will make a fantastic wide field photograph when composed with some interesting scenery.

On Saturday night, the moon will hop east to sit a palm’s width (or 5.5 degrees to the celestial southeast) of Saturn. They, too will fit within the field of view of binoculars. Before they set at about 3:12 am local time, the diurnal rotation of the sky will lift the moon higher than Saturn. Remember to look for the large Teapot-shape of stars sitting off to the right (west) of the two planets, especially when the bright moon has moved away.

The nearly full moon will end the week in modest Capricornus (the Sea-Goat). On Sunday night, the terminator on the waxing gibbous moon will fall just to the left (or west) of Sinus Iridum, the Bay of Rainbows. The circular 155 mile (249 km) diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger, dark Mare Imbrium to its east – forming a rounded handle-shape on the western edge of that mare. The “Golden Handle” is produced by way the slanted sunlight brightly illuminates the eastern side of the prominent Montes Jura mountain range surrounding the bay on the north and west, and by a pair of protruding promontories named Heraclides and Laplace to the south and north, respectively. Sinus Iridum is almost craterless, but hosts a set of northeast-oriented dorsae or “wrinkle ridges” that are revealed at this phase. Try your telescope on it!

The Planets

Speedy little Mercury reached superior solar conjunction, when it slides past the sun on the far side of the solar system, last Monday. It will become visible again in the west-northwestern post-sunset sky this week – but the low angle of the evening ecliptic will keep Mercury very close to the horizon for everyone living at mid-northern latitudes. If you view it from near the equator, or in the Southern Hemisphere, Mercury will put on a great show for you in September! If you’re game to look for it, the best time window falls around 8:15 pm local time.

The other inner planet, extremely bright Venus, will rise in the east-northeast at about 2:50 am local time this week, and then remain visible until sunrise as it is carried higher in the eastern sky by the rotation of the Earth. Viewed in a backyard telescope, Venus will show a half-illuminated shape. This week, Venus will be traveling east through the stars of Pollux, Gemini’s eastern twin. Venus is now shifting towards the sun – but the later sunrises at this time of year will let it shine in a dark, pre-dawn sky until early December! And while you’re up, enjoy a view of Orion (the Hunter) sitting well off to Venus’ right.

For evening planet-gazers, it’s all about the gas giants! As the sky darkens after sunset, very bright, white Jupiter will pop into view first, low in the southeastern sky – with dimmer, yellowish Saturn positioned almost a fist’s diameter to its left (east). Good binoculars will reveal Jupiter’s four large Galilean moons named Io, Europa, Ganymede, and Callisto as they dance around the planet from night to night. Even a modest-sized telescope will show Jupiter’s brown equatorial belts and the famous Great Red Spot (or GRS, for short) if the air is steady. Due to Jupiter’s 10-hour period of rotation, the GRS appears every second or third night from a given location on Earth. In the Eastern Time zone, the Great Red Spot will be crossing the planet’s disk after dusk on Monday, Thursday, and Saturday. It will also appear starting in late evening on Wednesday and Friday, and before it sets during the wee hours on Monday and Saturday morning.

From time to time, the round, black shadows cast onto Jupiter by its Galilean moons are visible in amateur telescopes as they cross (or transit) the planet’s disk for a few hours. Commencing at 8:32 pm EDT on Sunday evening, August 23, Io’s shadow will travel across Jupiter until 10:49 pm EDT. Starting at 12:57 am on Tuesday morning, Europa’s shadow will cross Jupiter. People in the Eastern Time zone won’t see the shadow complete its crossing – but observers farther west will see the entire event. From 10:27 pm EDT on Sunday evening, August 30 to 12:45 am EDT on Monday, Io’s shadow will again travel across Jupiter.

Saturn is a spectacular sight in backyard telescopes. With your unaided eyes, you should be able to spot it sitting to Jupiter’s left by about 9 pm local time. Even in a small backyard telescope, you can see Saturn’s rings. They’ll be narrowing every year – until they vanish for a few weeks during the spring of 2025. The rings are almost as almost as wide as Jupiter’s disk. See if you can see the Cassini Division. It’s the narrow, dark gap that separates Saturn’s main inner ring from its outer one.

A small telescope will also show several of Saturn’s moons – especially its largest, brightest moon, Titan! Because Saturn’s axis of rotation is tipped about 27° from vertical (a bit more than Earth’s axis), we are seeing the top surface of its rings – and its moons can arrange themselves above, below, or to either side of the planet. During evening this week, Titan will migrate counter-clockwise around Saturn, moving from below Saturn tonight (Sunday) to the upper right of the planet next Sunday. (Remember that your telescope might flip the view around.)

Reddish Mars is steadily increasing in disk size and brightness recently because Earth is travelling towards it – until October. Mars will put on a great sky show this autumn – but we don’t have to wait until then for good views of it! I’ve already seen its southern polar cap quite clearly in my small telescope. This week, the Red Planet will be rising in the east soon after 10 pm in your local time zone. Then it will cross the sky until dawn, when it will be positioned about five fist diameters above the southwestern horizon. Nothing near Mars is as bright, nor as red! Due to its orbital motion combined with ours, Mars has been speeding along the ecliptic. But now it’s slowing. This week, it will cross the narrow “V” of modest stars at the bottom of the constellation of Pisces (the Fishes).

This week blue-green Uranus will rise at about 10:30 pm local time. Despite its distance, it’s visible with unaided eyes and in binoculars under a dark sky. Look for the magnitude 5.7 planet sitting in southern Aries (the Ram) – about a fist’s diameter below (or 10° to the celestial south of) the ram’s brightest stars, Hamal and Sheratan.  As an additional aid, note that Mars is located only a generous fist’s diameter to the upper right (or 14° to the celestial west) of Uranus.

Dim and distant Neptune is located among the stars of eastern Aquarius (the Water-Bearer) – almost four fist diameters to the right (or 37° to the celestial west) of Mars. This week, Neptune will be rising soon after 8:30 pm local time. Then it will climb higher until about 2:15 am local time, when you’ll get your clearest view of it when it will sit almost halfway up the southern sky. Neptune is harder to find without a computerized telescope – but you can do it by “star-hopping”. Look for the medium-brightness stars that make a vertical line that spans a few finger widths: Phi (φ) Aquarii at top, Chi (X) Aquarii in the middle, and a group of three stars all named Psi (ψ) Aquarii at the bottom. Neptune sits just two finger widths to the left (2.75° east) of the top star. This week’s moon-filled sky is a not good time to search for it – so keep the instructions ready for when the moon leaves the scene.

On Friday, the dwarf planet (formerly asteroid) Ceres will reach opposition, its closest approach to Earth for the year. On the nights around opposition, Ceres will shine with a peak visual magnitude of 7.2, well within reach of binoculars and backyard telescopes. As a bonus, Ceres will be situated only a palm’s width above (or 6 degrees to the north of) the bright naked-eye star Fomalhaut, which hugs the southern horizon for observers at mid-northern latitudes. Both objects will easily fit within the field of view of binoculars. Ceres will already be climbing the southeastern sky after dusk. It will reach its highest elevation, and peak visibility, over the southern horizon after 1 am local time.

Bright Stars Roundup

The first stars to appear on late August evenings are the bright, white stars of the Summer Triangle asterism. Vega is at the top, dimmer Deneb sits to Vega’s lower left, and Altair sits to Vega’s lower right. At dusk, those three stars are high in the eastern sky, just below the zenith. This annual triangle in the summer sky will remain visible until the end of December! At magnitude 0.03, Vega is the brightest star in the summer sky, mainly due to its relative proximity to the sun of only 25 light-years. Altair is only 17 light-years from the sun, but Deneb is a staggering 2,600 light-years away; so bright despite its greater distance because of its far greater inherent luminosity.

Stars shine with a colouration that indicates their surface temperatures, and this is captured in their spectral classification. Our sun is a yellowish G-class star with a surface temperature of 5,800 K. The three bright stars of the Summer Triangle are A-class stars that appear blue-white to the eye and have high surface temperatures in the range of 7,500 to 10,000 K.

Over in the western sky in kite-shaped Boötes (the Herdsman) you’ll see orange Arcturus – a K-class giant star with a temperature of only 4,300 K. The bright reddish star sitting low in the southwestern sky is Antares, the heart of Scorpius (the Scorpion), is an old M-class star with a surface temperature of 3,500 K. Finally, in late evening, you’ll see yellowish Capella peeking over the northeastern horizon. It’s another G-class star located only 42 light-years away from us. By comparing these stars colours’ to other stars, you can estimate those stars’ temperatures.

Here’s another trick. Aim your telescope at a star and unfocus it – so that the point-like star swells into a disk. You should be able to see that star’s colour better when it’s out of focus.

Lyra the Harp

If you missed last week’s tour of the constellation Lyra (the Harp), I posted it with sky charts here.

Public Astro-Themed Events

Every Monday evening, York University’s Allan I. Carswell Observatory runs an online star party – broadcasting views from four telescopes/cameras, answering viewer questions, and taking requests! Details are here. Their in-person Wednesday night viewing has been converted to online via the observatory Youtube channel, where they offer free online viewing through their rooftop telescopes, including their new 1-metre telescope! Details are here.

My Insider’s Guide to the Galaxy webcasts with Jenna Hinds of RASC National will continue on Tuesday, August 25 from 3:30 to 5 pm EDT. We’ll review how to see the planets over the next several months, and especially the big Mars Opposition this October. Details and the schedule are here. Beyond that, join Jenna and John Reid on alternate Thursdays at 3:30 pm EDT as they run through the RASC’s Explore the Universe certificate.

On Thursday evening, August 27 at 7 pm EDT, the Ontario Science Centre will host Scenic Science on the Waterfront, at Ontario Place. Following a panel discussion the film Picture a Scientist will be shown. It explores how sexism and racism shape the experiences of women, including women of colour, in science.  Tickets and details are here.

Our David Dunlap Observatory Saturday night events may be cancelled, but we’re still pleased to offer the next best thing – a free online talk by Dr. John Moores, York Research Chair in Space Exploration at York University. Tune in to the RASC Toronto Centre’s YouTube channel at 7:30 pm EDT on Saturday, August 29 to see his talk entitled Methane on Mars: Fact, Folly, or Figment? More information can be found here.

The Canadian organization Discover the Universe is offering astronomy broadcasts via their website here, and their YouTube channel here.

On many evenings, the University of Toronto’s Dunlap Institute is delivering live broadcasts. The streams can be watched live, or later on their YouTube channel here.

The Perimeter Institute in Waterloo, Ontario has a library of videos from their past public lectures. Their Lectures on Demand page is here.

Space Station Flyovers

There are no ISS (International Space Station) flyovers for the GTA this week.

Keep looking up, and enjoy the sky when you do. I love questions and requests. Send me some!