Catch Peak Pons-Brooks Comet and Early Lyrids before Luna Leaps in Brightness, and Jupiter Passes Uranus Under Spring’s Arch!

My friend Denise Chilton took this terrific image of the completely eclipsed sun from southeastern Quebec on April 8, 2024. The shape of the white corona will be replicated in all the totality photos from that day. Her image also captured the large pink prominence that extended beyond the southern pole of the moon.

Hello, mid-April Stargazers!

Here are your Astronomy Skylights for the week of April 14th, 2024 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.

If you’d like me to bring my Digital Starlab portable inflatable planetarium to your school or other daytime or evening event in Bruce, Grey and Simcoe Counties, or deliver a virtual session anywhere, contact me through AstroGeo.ca, and we’ll tour the Universe, or the Earth’s interior, together! My book with John A. Read entitled 110 Things to See With a Telescope is a guide to viewing the deep sky objects in the Messier List – for both beginners and seasoned astronomers. DM me to order a signed copy!

The moon will become increasingly bright in the evening sky this week and offer some lovely sights to see under magnification. Comet 12P/Pons-Brooks will reach peak brightness and visibility after dusk while it passes below bright Jupiter, and much fainter Uranus will move close to Jupiter on Saturday. Mars will shine near Saturn in the morning sky, and some early Lyrids meteors might streak overhead.  Read on for your Skylights!

Success!

After a scramble to fly home to southern Ontario on Sunday night, April 7, I woke up on Monday morning in a Hamilton hotel room within the oncoming shadow of the moon. But it was raining and I wasn’t that deep into the zone of totality! Fortunately, I was able to connect with a dear friend with whom I had watched the August 21, 2017 solar eclipse, and join her troupe of eclipse chasers on a Lake Erie beach in Port Burwell, Ontario. There, with thousands of eager viewers we watched as the clouds drained away and revealed sunny, cerulean blue skies. I had set up an 80mm refractor telescope with a solar filter on a small, motorized mount and watched close-up the first nibble of the moon on the spotted sun. Passers-by stopped for a look as the moon moved over the sun.

As totality approached we felt the temperature drop and saw our shadows sharpen. Then the horizon darkened to the west as Luna’s shadow approached. The spectacle of the last diamond of light along the edge of the moon and then its black circle covering the sun was enhanced with the glorious white corona extending fingers farther in several directions. Binoculars showed my bright Venus and Jupiter flanking our eclipsed star. My now unfiltered telescope showed the many deep pink prominences extending from the sun beyond the moon’s limb. Gorgeous! The roar of the crowd complimented the experience. After 2m56s of totality we toasted with mimosas and shared some tears and hugs.

When is the next chance to experience a total solar eclipse? The moon’s shadow will briefly sweep over western Iceland before dinnertime and then northern Spain shortly before sunset on August 12, 2026. Then an extremely long eclipse will occur across Gibraltar, northern Africa, and the Red Sea on August 2, 2027. Get ready!

The Moon

The moon will shine ever brightly in the evening and late-night sky worldwide this week while it waxes toward next week’s full moon. These nights will be the best time to view our natural satellite under magnification through any decent pair of binoculars or a backyard telescope.

The pole-to-pole terminator that divides the lit and dark hemispheres of the moon will steadily march westward across the moon. Since the sun will be rising for locations along the terminator, its near-horizontal rays will cast stark shadows to the west of every bump, hill, mountain, and crater rim. Without any atmosphere to scatter light, crater floors near the terminator on its lit side can remain black pools while their rims are brightly lit. The shape of the shadow cast upon the partially lit crater floors tell us the form of the crater – bowl, plate, pie-pan, or a mix of them – and reveal the heights of the peaks that surround that crater. Meanwhile, the taller peaks on the dark side of the terminator catch the light first – producing islands of light in a sea of darkness. Those islands are taller. Selenographers also used the length of shadows to measure how high various features are.

The spectacular show evolves hour-by-hour and night-after night. This happens because the orbit of the moon around Earth is increasing the moon’s angle from the light source – the sun. So keep your optics handy and take a look at the moon from time to time.

At this time of the lunar month, the moon rises in the middle part of the day and then sets in the middle part of the night. It is perfectly safe to view the moon in daytime as long as you avoid pointing any optical device towards the sun. Parental guidance is a must for junior astronomers.

Once the stars appear tonight (Sunday), the nearly half-illuminated moon will shine below Gemini’s brightest stars, with Pollux on the upper left (or celestial east) and Castor on the right (celestial northeast). As the night wears on, the moon’s eastward orbital motion will shift it closer to Pollux. The trio will set around 2:45 am local time.

The moon will spend Monday and Tuesday crossing the faint stars of Cancer (the Crab). It will complete the first quarter of its orbit around Earth on Monday at 3:13 pm EDT or 12:13 pm PDT and 19:13 Greenwich Mean Time. At first quarter, the relative positions of the Earth, sun, and moon cause us to see our natural satellite half-illuminated – on its eastern side. The terminator will temporarily straighten on Monday. After that, it will bend the other way and the moon’s phase will switch from waxing crescent to waxing gibbous. The altering form of the terminator told the ancient astronomers that the moon was a sphere lit by the sun. By the way, everyone on Earth sees the same phase of the moon. But we need to wait until our part of the world turns to put it above our horizon. Moon phases are not connected to the Earth’s rotation.

On Monday night, observers in the Americas should be able to see that the floor of the large crater Albategnius, which is close to the centre of the moon, is shrouded in darkness while that crater’s central mountain peak is catching the light and its western (left-hand) rim is lit up. The high Caucasus and Alpine mountains that form the eastern border of Mare Imbrium, in the moon’s north, will be emphasized, too. More and more of Mare Imbrium’s big circle will become illuminated from Tuesday through Thursday. Meanwhile, the moon will visit Leo (the Lion) from Wednesday through Friday.

On Thursday the lunar terminator will fall across the western edge of Sinus Iridum, the Bay of Rainbows. The circular, 249 km-wide feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its right (lunar east) – forming a rounded “handle” on the western edge of that mare. A claire-obscure effect called the “Golden Handle” effect is produced when the rising sun lights up the peaks of the prominent curving Montes Jura mountain range surrounding Sinus Iridum on the north and west, while the floor of the bay at their feet remains unlit. Watch for the promontories named Heraclides and Laplace that poke into Mare Imbrium to the south and north of the bay, respectively. Any telescope will show you that Sinus Iridum is almost craterless – so we know that it is geologically young. But it does host a set of northeast-oriented dorsae or “wrinkle ridges” that are nicely revealed at this lunar phase. I’ll post a photo of the area here. Don’t fret if you miss seeing the Golden Handle. The effect returns every few months a few days before full moon.

For the coming weekend the moon will be very bright when it rises in late afternoon and shines all night long among the stars of Virgo (the Maiden).

The Arch of Spring

A prominent winter asterism persists into April. During early evening, the tipped-over Winter Hexagon is sinking toward the western horizon. Also known as the Winter Circle and Winter Football, it is composed of (moving anti-clockwise from the bottom left) bright white Sirius (Alpha Canis Majoris), blue-white Rigel (Beta Orionis), orange Aldebaran (Alpha Tauri), yellow Capella (Alpha Aurigae), white Castor and golden Pollux (Alpha and Beta Geminorum respectively), and white Procyon (Alpha Canis Minoris).

Some people use the top stars of the Winter Hexagon to make another pattern called the Arch of Spring. Eliminate Rigel and Aldebaran, add the fainter star Menkalinan near Capella, and continue the curve past Capella to the bright star Mirfak in Perseus (the Hero). This year, the arch is playing host to Jupiter and Uranus! Tonight (sunday) the moon will shine at the top of the arch!

Comet Pons-Brooks

Here’s your weekly update on periodic comet 12P/Pons-Brooks. It is visible in the northwestern sky in early evening, though it will become harder to see from mid-northern latitudes from here on out. The comet has brightened to about magnitude 4.5, which is within reach of a small backyard telescope or good binoculars under dark skies – and possibly unaided eyes. Unfortunately, the brightening moon later this week will hamper our views. The comet should reach its maximum brightness for Earthlings when it passes closest to the sun at perihelion on April 21.

You may have heard this comet referred to as the “Devil Comet”, a silly clickbait name that is a leftover from last fall when the comet sprouted two jets of gas that made it resemble a horned head or the Millennium Falcon. It no longer looks that way.

For observers in mid-northern latitudes, the comet will be located low in the western sky after dusk every night. The best combination of sky darkness and the comet’s height will be around 9 pm in your local time zone. The comet will drop below the treetops around then, so stand where you have an unobstructed view to the west-northwest and start looking as soon as the sky darkens. Visually, expect to see a faint, fuzzy smudge that may look greenish in photographs and larger telescopes. Its faint tail, best seen in binoculars and long exposure photos, will extend upwards.

Tonight (Sunday) the comet will be positioned several finger widths below and slightly to the left of Jupiter – more than close enough for them to share the view in binoculars. It will shift to the left by about a finger’s width per night, but the comet and Jupiter will continue to be binoculars-close to Jupiter until Wednesday. On the coming weekend the comet will be passing closely above the medium-bright stars Xi and Omicron Tauri (or ξ Tau and o Tau). Let me know if you see it!

Lyrids Meteor Shower

Keep an eye out for “early birds” from the annual Lyrids meteor shower, which is derived from particles dropped by comet C/1861 G1 (Thatcher), and runs from April 16 to 29. The shower will peak in intensity next Monday morning, April 22. A full moon will spoil the shower on the peak night this year, so you might have better luck looking for a few of them earlier this week.

The Planets

Going… going…soon to be gone. Bright Jupiter is getting lower in the western sky every night as the motion of Earth around the sun shifts things sunward. The planet is bright enough that you will be able to spot it shortly after sunset, when it will appear a good distance above the rooftops to the west. The planet will get easier to see as the sky darkens, but lower, too. It will set just before 10 pm local time.  As I mentioned above, periodic comet 12P/Pons-Brooks will be sliding under and to the lower left of Jupiter this week.

Binoculars will show you Jupiter’s four largest Galilean moons lined up beside the planet. Named Io, Europa, Ganymede, and Callisto in order of their orbital distance from Jupiter, those moons complete orbits of the planet every 1.7, 3.6, 7.2, and 16.7 days, respectively. If you see fewer than four moons, then one or more of them is crossing in front of or behind Jupiter, or hiding in Jupiter’s dark shadow – or two of the moons are very close together or occulting one another.

On the invisible racetrack of the ecliptic, Jupiter has been gaining ground (sky?) on Uranus for some time. On Saturday evening, Jupiter will pass half a finger’s width to the lower left (or 0.45 degrees to the celestial south) of Uranus’ magnitude 5.8 blue-green spot. Before Saturday, Uranus will be positioned to Jupiter’s upper right (or celestial northeast). At closest approach on Saturday, the duo will easily share the eyepiece in a backyard telescope. (Note that your telescope will likely flip and/or mirror their arrangement.) After Saturday, Jupiter will climb higher than Uranus – but the pair will be settling into the western twilight, making fainter Uranus hard to see.

After Uranus and Jupiter set, the night sky will be completely devoid of planets until Pluto rises with the stars of Capricornus (the Sea-Goat) around 3:30 am. Since that dwarf planet is so hard to see, we’ll have to wait for the medium-bright duo of Mars and Saturn to rise after 5 am local time and clear the rooftops in the east-southeast about half an hour later. The two planets will shine at the same magnitude 1.15 intensity. Reddish Mars will be located to the lower left of yellowish Saturn, but its faster orbital motion will nearly triple its separation from Saturn this week. Turn all optics away from the eastern horizon before the sun rises. The severely tilted morning ecliptic will keep the planets low in a brightening sky, but observers living closer to the tropics, where the ecliptic will stand upright, will have a much easier view of them.

The inner planets Mercury and Venus are rising shortly before the sun every morning, making them a challenge to see unless you live near the equator. Venus will meet the sun at solar conjunction in early June.

Public Astronomy-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. They host in-person viewing on the first clear Wednesday night each month. Other Wednesdays they stream views online via the observatory YouTube channel. Details are here.

At 7:30 pm on Wednesday, April 17, the RASC Toronto Centre will livestream their free monthly Speaker’s Night Meeting. The speaker will be Prof. Paul Scholz, York University. His topic will be Fast Radio Bursts: What are they and where do they come from? Check here for details and watch the presentation at https://www.youtube.com/rasctoronto/live.

On Friday, April 19 from 9 pm to 11 pm, RASC Toronto Centre will host Family Night at the David Dunlap Observatory for visitors aged 7 and up. You will tour the sky, visit the giant 74” telescope, and view celestial sights through telescopes if the sky is clear. This program runs rain or shine. Details are here, and the link for tickets is here.

Spend some time in the other dome at the David Dunlap Observatory! On Saturday, April 20, you can join me in my Starlab Digital Planetarium for an interactive journey through the Universe at DDO. We’ll tour the night sky and see close-up views of galaxies, nebulas, and star clusters, view our Solar System’s planets and alien exo-planets, land on the moon, Mars – or the Sun, travel home to Earth from the edge of the Universe, hear indigenous starlore, and watch immersive fulldome movies! Ask me your burning questions, and see the answers in a planetarium setting – or sit back and soak it all in. Please note that all guests will sit on a clean floor. A registered adult must accompany all registered participants under the age of 16. We run sessions geared to junior astronomers in the morning and family sessions at 1 pm and another at 2:45 pm. Registration is required. More information and the registration links are here.

If the stars come out on Saturday evening, April 20 from 8 to 11 pm, the RASC astronomers will set up their telescopes on the Unilever Science Plaza in front of the Ontario Science Centre for a free public star party. Registration is not required, but parking fees may apply. Find more information here.

Space Station Flyovers

There are no good opportunities to see the ISS (the International Space Station) gliding silently over the Greater Toronto Area this week.

Keep your eyes on the skies! I love getting questions and requests. Send me some!