Sky This Week is brought to you in part by Celestron.
Friday, April 4
This evening, the roughly half-illuminated face of the Moon hangs in Gemini, high in the south an hour after sunset. First Quarter Moon occurs at 10:15 P.M. EDT.
The two brightest stars in Gemini are Castor (magnitude 1.6) and Pollux (magnitude 1.2). They are outshined tonight by Mars, which is magnitude 0.5. The Red Planet is located to the lower left of Pollux in the early-evening sky, with the Moon to its lower right, more directly below Castor.
Once the sky grows dark enough, you’ll spot another star — magnitude 3.6 Kappa (κ) Geminorum — just to the right of Mars. The Red Planet recently passed close to this star and now stands just 1° away. Like only a few other stars in the sky, Kappa Gem is so close to Earth — and so large — that astronomers have been able to measure its angular size. This giant is roughly 12 times the size of our Sun and more than 70 times as bright. It lies at a distance of 141 light-years.
Mars, meanwhile, is now nearly 110 million miles (176.5 million kilometers) from Earth and spans some 8” on the sky. Features on its surface are getting harder to view even for those with larger scopes, but high-speed planetary photography may help more experienced observers capture glimpses of its lighter and darker regions as the planet rotates. Around 9 P.M. CDT this evening, the dark splotch of Sinus Meridiani should be roughly central on the martian disk.
Sunrise: 6:38 A.M.
Sunset: 9:28 P.M.
Moonrise: 11:06 A.M.
Moonset: 2:18 A.M.
Moon Phase: Waxing crescent (46%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
Saturday, April 5
Standing 45° high in the west an hour after sunset, magnitude –2.1 Jupiter dominates the constellation Taurus, far outshining its brightest star, Aldebaran (magnitude 0.9). The gas giant is easy to find, now forming and upside-down triangle with the tips of the Bull’s two horns.
Train your telescope on this distant world; observers on the East Coast will spy a small, dark spot crossing the planet’s southern hemisphere — that’s the shadow of the icy moon Europa, now off to Jupiter’s west after recently completing a transit. Callisto lies much farther west, while Io sits alone to the planet’s east. Ganymede is nowhere to be seen, currently passing behind the planet’s disk.
An hour after sunset in the Midwest, Europa’s shadow is approaching the planet’s southwestern limb, finishing its transit around 9:55 P.M. EDT. Then, turn your gaze to Jupiter’s northeastern limb, where the huge moon Ganymede reappears beginning at 10:22 P.M. EDT. It then begins moving away from Jupiter to the east — and fades out again two hours later, at 11:30 P.M. CDT, as it passes into the planet’s long, dark shadow. (Note the time change, as Jupiter has set in the Eastern time zone and is getting low for the central U.S. Those in the western half of the country will have the best view.)
Ganymede won’t reappear until shortly after midnight PDT, as the planet is setting for those on the West Coast. Some lucky viewers, particularly farther west and at higher elevation, may get to see the reappearance.
Sunrise: 6:37 A.M.
Sunset: 9:29 P.M.
Moonrise: 12:14 P.M.
Moonset: 3:09 A.M.
Moon Phase: Waxing gibbous (57%)
Sunday, April 6
Mercury stands stationary against the stars of Pisces at 2 A.M. EDT. The planet rises shortly before the Sun, reaching an altitude of 4.5° above the eastern horizon 20 minutes before sunrise. Now at magnitude 1.6, Mercury is quite faint and will be hard to pick up in the brightening dawn. You can try to spot it with binoculars or a small telescope, but take care to put these away several minutes before sunrise from your location, which may differ from the time listed below.
Saturn lies just under 3° south of Mercury this morning; you may be able to briefly spot it in binoculars, shining at magnitude 1.2. It will be a similarly challenging sight and again, remember to put away your optics well before sunrise.
Venus can stand as a signpost: The magnitude –4.5 planet is a beacon even in the bright pre-dawn sky, some 10.5° high shortly before sunrise. Mercury hangs 6° below it and slightly to the right. Through a telescope, Venus is gorgeous in the twilit sky, showing off a slender 7-percent-lit crescent and a disk that spans a hefty 54”. Mercury, by comparison, is 10” wide and 18 percent lit.
Sunrise: 6:35 A.M.
Sunset: 9:30 P.M.
Moonrise: 1:23 P.M.
Moonset: 3:49 A.M.
Moon Phase: Waxing gibbous (68%)
Monday, April 7
Now is the time to catch your last views of Uranus before the planet drops out of sight, too close to the Sun for observation by the end of the month.
The ice giant is now located in far western Taurus, visible for about three hours after sunset. As soon as the sky grows dark, look west to find bright Jupiter, blazing between the horns of the Bull. Drop to the planet’s lower right and look for the Pleiades (M45), a young open cluster of stars often called the Seven Sisters, with six to seven bright stars visible to most observers’ naked eye. Through binoculars or a telescope finder, this cluster bursts forth with many more stars as well, with more than a thousand stars ultimately calling this grouping their home.
Using your binoculars or finder, drop about 4.5° south of the Pleiades to look for a pair of 6th-magnitude stars: 13 and 14 Tauri. From these stars, skim 3° southwest and you’ll land on another pair, consisting of a 6th- and 7th-magnitude star. The dimmer star lies to the west, and Uranus — a brighter magnitude 5.8 — is 0.9° northwest of this star.
The planet’s span is just 3”, appearing as a tiny disk on the sky. You may be able to pick up on its bluish-gray hue. The planet is slowly inching east; in about a week, it will sit due north of the same faint star.
Sunrise: 6:34 A.M.
Sunset: 9:31 P.M.
Moonrise: 2:30 P.M.
Moonset: 4:21 A.M.
Moon Phase: Waxing gibbous (76%)
Tuesday, April 8
Holding steady at magnitude 12.5, Comet 29P/Schwassmann-Wachmann (also called Schwassmann-Wachmann 1) is making its way through southwestern Leo, high in the southern sky around 9:30 P.M. local daylight time. The comet is 1.5° northwest of magnitude 3.5 Subra (Omicron [ο] Leonis) tonight, and passing just 2’ southeast of an 8th-magnitude background star, aiding in its identification.
That identification may still be challenging, however, as the waxing Moon lies not far away this evening in central southern Leo. If you’re unable to spot the comet, consider returning once the Moon has moved on — Schwassmann-Wachmann 1 stays close to this star for the rest of the month, making a tight turnaround in direction on the 20th.
Don’t give up observing within the Lion altogether if you can’t find the comet, though — instead, try focusing on some of the Lion’s stars.
Subra is a binary system, but its components are too close to resolve with a telescope. However, some 7° to Subra’s northeast is blazing Regulus, the Lion’s 1st-magnitude heart. This star is a quadruple system that includes a white dwarf. That dwarf, along with a second component, are not visible through binoculars or small telescopes. But the primary and its fourth companion, and 8th-magnitude star some 3’ to Regulus’ northwest, are both visible. Because the companion is so faint, try moving Regulus just out of your field of view to see it.
Sunrise: 6:32 A.M.
Sunset: 9:32 P.M.
Moonrise: 3:35 P.M.
Moonset: 4:46 A.M.
Moon Phase: Waxing gibbous (84%)
Wednesday, April 9
We’re back in Leo this evening, where the Moon has moved toward the Lion’s back foot and asteroid 8 Flora passes near the galaxy NGC 3628.
Tenth-magnitude Flora is now traveling through a region relatively free of distracting stars but rich with galaxies. The asteroid lies roughly half a degree northeast of M65 and M66, the brighter two of the three galaxies in the Leo Triplet. (M66 is magnitude 8.9, while M65 is magnitude 9.3.) Further, Flora is a mere 9’ east of the third galaxy in this trio, magnitude 9.5 NGC 3628.
The Moon’s light may again try to interfere with observation, so use the largest telescope you have and try coming back tomorrow night or the next, when our satellite has moved farther away into Virgo. Flora is floating in this region all month, not moving more than a degree from the Leo Triplet, so you’ve got the luxury of time to come back under better conditions if needed.
Sunrise: 6:31 A.M.
Sunset: 9:33 P.M.
Moonrise: 4:36 P.M.
Moonset: 5:09 A.M.
Moon Phase: Waxing gibbous (90%)
Thursday, April 10
Venus is now stationary in the constellation Pisces at 11 A.M. EDT. You can catch the bright planet in the early-morning sky, rising 90 minutes before the Sun. An hour before sunrise, Venus is 4° above the eastern horizon and gaining altitude by the minute. It lies roughly equidistant between the 4th-magnitude stars Lambda (λ) and Gamma (γ) Piscium, both of which are part of Pisces’ Circlet asterism. These will fade out much faster in the brightening sky than the blazing planet, which will remain visible until shortly before sunrise.
Mercury now hangs directly below Venus as the planets rise; the smaller world clears the horizon around 5:40 A.M. local daylight time and has brightened slightly from earlier this week, now magnitude 1. Look for it in binoculars or a small telescope some 6.5° below Venus in the half hour before sunrise, but as always, make sure to put away your optics at least several minutes before the Sun will breach the horizon from your location.
Sunrise: 6:29 A.M.
Sunset: 9:34 P.M.
Moonrise: 5:37 P.M.
Moonset: 5:29 A.M.
Moon Phase: Waxing gibbous (95%)
Friday, April 11
There’s more action at Jupiter this week as Io and its shadow are crossing the disk of the gas giant as night falls across the mid-U.S.
Jupiter remains standing high within the bounds of Taurus in the west after sunset. Lock your telescope on the bright planet and settle in for a series of events. As the Sun is sinking below the horizon in the Midwest, Io is slipping in front of the disk, beginning a transit from east to west starting around 8:30 P.M. EDT. An hour later, when it’s fully dark in the Midwest, Io is nearly central on the disk. Its shadow appears moments later, just before 9:40 P.M. EDT.
Note that Jupiter’s Great Red Spot, a constant, Earth-sized storm in the gas giant’s atmosphere, is also crossing the disk at this time as the planet rotates. It’s a chance to see just how dynamic and detail-rich the Jupiter system really is.
The volcanic moon and its shadow then trek across the disk together for another hour. Io finally ends its transit around 10:46 P.M. EDT, with its shadow now halfway across Jupiter’s face. That shadow continues across for just over an hour, finally disappearing at 11:52 P.M. EDT.
Throughout the event, Europa lies to Jupiter’s east, with Callisto farther east beyond it. Ganymede is alone to Jupiter’s west until Io’s transit ends and its fellow moon joins it, balancing out the view.
Sunrise: 6:27 A.M.
Sunset: 9:35 P.M.
Moonrise: 6:36 P.M.
Moonset: 5:48 A.M.
Moon Phase: Waxing gibbous (98%)
