Mars and Jupiter and the Moon Invite Evening Sightings while Pre-dawn Venus Gleams in the East!
My friend Dave Chapman from Dartmouth, Nova Scotia captured this terrific image of Saturday morning’s partial solar eclipse shortly after sunrise from Seaforth, NS.
Hello, April Stargazers!
Here are your Astronomy Skylights for the week of March 30th, 2025 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 FaceBook, Instagram, Threads, and Bluesky 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 Simcoe, Grey, and Bruce 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 shine in the evening sky worldwide this week, inviting us to view its spectacular terrain as it the terminator slides across it. It will pass through or pose near the Pleiades Cluster and set up some nice photo ops near Jupiter and Mars. Venus will gleam above three other planets in the east before sunrise. Read on for your Skylights!
The Moon
This will be the best week of the moon’s 29.5 day cycle to enjoy views of our natural satellite in the evening worldwide. The moon will start the week shining low in the western sky for a short time after sunset, allowing us to continue exploring the bonanza of spring galaxies under dark sky conditions after it sets. The moon’s steadily increasing angle from the sun will cause it to linger deeper into the night every day, wax fuller, and brighten. As we get deeper in the week, you might notice the moon in the afternoon daylight sky, too.
While the moon is swinging away from the sun on the evenings after new moon, the bright, sun-facing half of the moon’s globe rotates more and more around onto the moon’s Earth-facing hemisphere. That’s what makes the moon wax in phase. The boundary separating the dark and lit hemispheres runs from the north pole to the south pole of the moon and wraps around the far side of the moon that we don’t see. That terminator line shows where the sun is just rising over the lunar surface. Everything near that line is being bathed by nearly horizontal rays of sunlight and casting long, inky-black shadows to the west.
Even the smallest humps and bumps can cast shadows and become visible while the terminator is near them. Larger features, such as crater rims, boulders, cliffs, and mountain peaks, become brightly lit on the sunward side, while the outlines of their long shadows allow us to discern their topographic profile very accurately. Depressions, especially crater floors, are engulfed in darkness – either fully or partially.
The lunar terrain looks spectacular under these conditions whether you are just looking up with your eyes, using any size of binoculars, or viewing the moon through a telescope. Even better, just as sunrises sweep past us on Earth and deliver the same spectacle to folks living west of us after we see it, the lunar terminator slowly creeps west across the moon, highlighting new vistas hour by hour and night over night. Because the moon is tidally locked with one side facing Earth, it rotates once, from the sun’s perspective, every 29.5 days, whereas Earth rotates once per day. That means that the sun’s disk takes about an hour to fully climb clear of the moon’s horizon, instead of the mere two minutes that takes on Earth. On the moon, you’d have time to dine while you watch the sun rise, literally – though I hear that the moon’s restaurants have good food, but no atmosphere.
As we look at what the moon will get up to this week, I’ll highlight some of the sights to see on it.
Tonight (Sunday) the slender, 3%-illuminated crescent moon will appear above the western horizon after sunset. By the time it sets around 9:45 pm local time, bright Jupiter and the stars will appear above it. On Monday, its thicker crescent will resemble the Cheshire Cat’s smile when it shines below bright Jupiter and the Pleiades Star Cluster – setting up a wonderful widefield photo opportunity. Uranus will be positioned between the moon and the Pleiades, but it’s not easily seen without a telescope. Watch for Earthshine on the moon. Sometimes called the Ashen Glow or the Old Moon in the New Moon’s Arms, the phenomenon is visible every lunar month within a day or two of new moon, when sunlight reflected off Earth and back toward the moon slightly brightens the unlit portion of the moon’s Earth-facing hemisphere.
Also on Monday, watch for the dark oval of Mare Crisium “the Sea of Crises” within the right-hand horn of the crescent. In the central span of the crescent, a line of large craters collectively known as the “Gang of Four” will be easily visible with sharp eyes or optical aids. From left to right (or lunar south to north) they are: Furnerius, Petavius, Vendelinus, and Langrenus. All four craters are about 130 km in diameter – a mere 90 minutes of driving in your solar-powered, electric moon buggy! Mare Crisium and those craters appear to be oval because features near the lunar limb are fore-shortened by the spherical shape of the moon.
Furnerius is ancient and battered, with a heavily eroded and smoothed rim and younger craters on its floor. Under magnification, Petavius has a ringed appearance due to terraces generated as its rim slumped since formation. It has been flooded by lava, almost burying its central mountain peak. One large, and several smaller rilles, or lava channels, cross its almost craterless floor. The edge of ancient Vendelinus has been worn and overprinted by many later impacts. It has been filled with dark lava, leaving a smooth floor that hosts several flat-floored craters, evidence that the lava arrived after they formed. The rim of Langrenus is highly terraced and quite wide and free from overprinting. A split central peak emerges from a smooth floor that has rubble on its upper (or lunar western) half.
The moon will shine just above the Pleiades Star cluster (aka The Seven Sisters, Subaru, and Messier 45) in Taurus (the Bull) on Tuesday evening. Observers living in the UK and Europe and western Africa can watch the crescent moon cross directly through the Pleiades. Wherever you live, try binoculars or a telescope, as the moonlight will largely hide the “Seven Sisters”. Bright Jupiter will gleam above the moon. Mare Crisium will now be fully exposed.
On Wednesday evening, another 24 hours of eastward orbital motion will place the slightly fuller crescent moon less than a palm’s width to the upper right (or 5 degrees to the celestial north) of the brilliant planet Jupiter in Taurus (the Bull). The duo will share the view in binoculars and make a nice photo opportunity until they set in the west after midnight local time.
On Thursday evening, the bright, crescent moon will be surrounded by Taurus and Jupiter, Auriga (the Charioteer), Orion (the hunter), and Gemini (the Twins) and Mars. The terminator will fall just to the left of a trio of large craters named Theophilus, Cyrillus, and Catharina that curve along the western edge of gray Mare Nectaris “the Sea of Nectar” in the crescent’s centre. You can tell what order the craters were formed in by observing how sharp and fresh Theophilus’ rim appears, and by the way it has partially overprinted neighboring Cyrillus to its lower left (or lunar southwest). Under magnification, Theophilus’ terraced rim and craggy central mountain peak are evident. Cyrillus hosts a trio of degraded central peaks inside a hexagonal rim, while much older Catharina’s peak has been submerged, her edges blurred and her floor overprinted by smaller, more recent craters.
On Friday night, the half-full moon will shine a fist’s diameter below (or 10 degrees to the celestial west of) the red planet Mars and Gemini’s two brightest stars, yellowish Pollux and whitish Castor. Observers in more westerly time zones will see the moon closer to the line formed by the trio. The moon will officially complete the first quarter of its orbit around Earth at 10:15 pm EDT or 7:15 pm PDT, which converts to 02:15 Greenwich Mean Time on Saturday, April 5.
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. First quarter moons always rise around noon and set around midnight, allowing them to be seen in the afternoon daytime sky, too. At the first (and third) quarter phases, the terminator becomes a straight line, clear evidence that the moon is a sphere. The upper right (northerly) parts of the moon are now dominated by the dark and smooth ovals of Mare Serenitatis “the Sea of Serenity” and Mare Tranquillitatis “the Sea of Tranquility”. Apollo 11 was sent to the more southerly Mare Tranquillitatis because its equatorial location made the orbital mechanics easier and because its less rugged lava surface was safer to land on. See if you can tell that its dark basalts are bluer in colour than any other mare. That’s due to enrichment in the valuable element titanium, another plus for the landing location.
On Saturday night the bright, gibbous moon will shine a short distance above (or celestial east of) the Mars-Pollux-Castor line, but it will actually be across the border and into Cancer (the Crab). The upper portion of the moon will host the spectacular arc of the mountains around dark Mare Imbrium “the Sea of Rains” will be highlighted. They are the ancient rim of Imbrium’s basin. The rest of the region along the terminator will be littered with craters forming the bright, lunar highlands. Watch for two sets of three larger craters close to the terminator – namely Ptolemaeus, Alphonsus, and Arzachel (in descending size) and then Purbach, Regiomontanus, and Walther, which are all of similar size.
The crustacean’s stars aren’t very bright. The moon will spend next Sunday night to their left (or celestial east). Watch for the dark smooth oval of Plato along the northern rim of Mare Imbrium and the smaller crater Eratosthenes along the south. Try seeing them with eyes only, first. My favorite crater Clavius, with a curved set of craters that diminish in diameter inside it, will hug the terminator at the moon’s bottom.
By the way, two weeks later in the moon’s cycle, it approaches the sun in the morning sky. The terminator, now representing sunset on the moon, still migrates west across the moon’s face and highlights its terrain in a similar way – just lit from the opposite direction.
The Planets
This week, three planets are shining in the western evening sky, but only two of them are easy to see. The rest of the planets are gathered above the eastern horizon before sunrise, but Venus is the only morning planet that you’re likely to be able to spot unless you live in the tropics.
For those of us living at mid-northern latitudes, the plane of our solar system, which is more or less the same line across the sky as the ecliptic, makes a very shallow angle with the eastern horizon before sunrise during the weeks surrounding the March and September equinox’. Since all the planets remain within a zone close to the ecliptic, they are being kept very low above the eastern horizon while the morning sky is still dark enough to see them. (Those planets climb plenty high in the daytime, but the sun’s glare hides them.)
Mid-Northern latitudes encompass the Great Lakes region, the northern US states, Europe from France across to Romania and then east through southern Kazakhstan, Mongolia, and over to the northern tip of Japan, since they all straddle the 45th N parallel. The ecliptic and/or plane of the solar system is nearly vertical year-round for anyone closer to the tropics, so those residents can see the planets while they are closer to the sun. A similar limitation applies if you live at mid-Southern latitudes.
The longer it rises before the sun, the easier it is to see a morning planet (or star, for that matter). Morning planets steadily increase their rise time ahead of the sun every morning because the sun is moving eastward along the ecliptic faster than the planets can follow it. The distant outer planets gain up to four minutes of head start on the sun with each passing day. The swift orbital motions of the inner planets Venus and Mercury can increase or decrease that lead time – reducing it if they are swinging east and sunward or increasing it if they are traveling retrograde westward. Both Venus and Mercury are in retrograde at the moment.
This week at mid-northern latitudes, the sun is rising at about 7 am local time. Brilliant Venus will be rising more than an hour ahead of that, so you can catch sight of it between the trees or buildings until almost sunrise. In good binoculars or a telescope, the planet will show an extremely thin, waxing crescent phase and a large disk size – but turn those aids away from the eastern horizon before the sun starts to rise.
Mercury will clear the horizon around 6:15 am local time. The speedy planet will become higher and more visible every morning until late April. Saturn will be located near Mercury, nearly a fist’s diameter to Venus’ lower right (or celestial south). That planet’s rings are currently nearly edge-on to Earth, but only tropical observers can hope to see that. Lastly, Neptune will clear the horizon below Venus and Mercury just half an hour before sunrise. We’ll be able to obtain blurry views of Saturn and Neptune in May.
Turning to evening, the very bright planet Jupiter will become visible halfway up the western sky as it darkens after sunset. You’ll get nice views of the big planet through binoculars and telescopes until about 11 pm local time. It will set around 1 am local time. The brightest stars of winter surround Jupiter, including Taurus’ brightest star, reddish Aldebaran just below Jupiter, reddish Betelgeuse to the planet’s left, and yellowish Capella in Auriga (the Charioteer) to its upper right. Over the next month, Jupiter’s easterly prograde motion will carry it higher above Aldebaran and between the Bull’s horns. At the same time, Earth’s orbital motion will carry the planet and all of those stars lower and sunward.
When viewed in any size of telescope, Jupiter will display a large disk striped with several dark brown belts and beige light zones, all aligned parallel to its equator, which will be tilted. With a better grade of telescope, Jupiter’s Great Red Spot, a cyclonic storm that has raged for hundreds of years, will be visible for several hours when it crosses the planet every 2nd or 3rd night. For observers in the Americas, the GRS will cross Jupiter’s disk during early evening tonight (Sunday), Tuesday, Friday, and next Sunday, and also around 11 pm Eastern time on Tuesday, Thursday, and next Sunday night. If you have any coloured filters or nebula filters for your telescope, try enhancing the spot with them.
Any size of binoculars will show you Jupiter’s four Galilean moons named Io, Europa, Ganymede, and Callisto lined up beside the planet. 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 one moon is eclipsing or occulting another one.
From time to time, observers with good quality telescopes can watch the black shadows of the Galilean moons travel across Jupiter’s disk. In the Americas, Io’s small shadow will chase the great red spot across Jupiter on Friday evening, April 4 between 7:43 pm (in twilight) and 9:53 pm EDT (or 23:43 Friday to 01:53 GMT on Saturday). Europa’s small shadow will cross Jupiter on Saturday evening, April 5 between 7:16 pm (in daylight) and 9:51 pm EDT (or 23:16 Friday to 01:51 GMT on Saturday). Additional shadow crossings will be visible in other time zones.
From Aldebaran, search a generous fist’s width to its right, and down a little, for the bright little Pleiades Star Cluster (aka Messier 45, the Seven Sisters, and Subaru). Then sweep a palm’s width below that to find Uranus. If you use your binoculars to find the up-down pair of medium-bright stars named Botein and Al Butain IV (aka Epsilon Arietis), Uranus will be the dull-looking blue-green “star” located several finger widths to their left (or southeast). In a backyard telescope, Uranus will appear as a fairly prominent, non-twinkling blue-green dot. Before the moon gets too bright later this week, Uranus will be readily observable from the end of evening twilight until about 9:30 pm, when it will be hitting the treetops in the west.
Now greatly faded from its brilliance in January due to Earth’s growing distance from it, red-tinted Mars will need the sky to darken quite a bit before you can find it shining very high in the southwestern sky to the lower left (or celestial south) of the two bright stars Pollux and Castor in Gemini (the Twins). The trio will form a line next week. The little star named Kappa Geminorum just above Mars marks the eastern hand of Pollux. You can view Mars until the wee hours of the night.
Leo Leads to Galaxies
If you missed last week’s dive into spring galaxies and the constellations of Leo (the Lion), I posted it with sky charts and photos of its treats here.
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.
Taking advantage of the crescent moon in the sky this week, the RASC Toronto Centre astronomers will hold their monthly City Sky Star Party in Bayview Village Park (a short walk from the Bayview TTC subway station), starting after dusk on the first clear weeknight this week (Mon, Tue or Thu only). Check here for details, and check the banner on their website home page or Facebook page for the GO or NO-GO decision around 5 pm each day.
Eastern GTA sky watchers are invited to join the RASC Toronto Centre and Durham Skies for solar observing and stargazing at the edge of Lake Ontario in Millennium Square in Pickering on Friday evening, April 4, starting at 6 pm. Details are here. Before heading out, check the RASCTC home page for a Go/No-Go call – in case it’s too cloudy to observe. The back-up date is Saturday, April 5.
On Wednesday evening, April 2 at 7:30 pm EDT, the RASC Toronto Centre will host their free, public Recreational Astronomy Night Meeting at the Petrie Science building at York University and also live streamed at https://www.youtube.com/rasctoronto/live. Talks will include The Sky This Month, astronomy in Morocco, and preserving the night sky. Details are here.
Space Station Flyovers
The ISS (or International Space Station) will not be visible gliding silently over the Greater Toronto Area this week.
Keep your eye on the skies! I love getting questions and requests. Send me some!