Sky This Week

What to look for in the Night Sky this week with a quick Survey at the bottom.

Supernova in NGC 3621 in Hydra. Supernova 2024ggi, discovered a month ago, quickly reached visual magnitude 12.0, stayed there for a couple weeks, and is now beginning to drift down slightly (12.3 as of May 2nd). NGC 3621, glowing at 10th magnitude, is rather far south at declination –33°. But it crosses the meridian soon after dark.


■ When the stars come out for North America tonight, you'll find the Moon shining nearly midway between Spica to its lower left and fainter Gamma Virginis (Porrima) to its upper right; see below. Gamma Vir is a lovely, equal-brightness double star for telescopes, separation 3.4 arcseconds this year; they're slowly widening. The pair is oriented almost north-south.

Waxing gibbous Moon passing Spica, June 15-16, 2024

When the Moon steps past Spica in early or mid-June, it's always waxing gibbous. Do you know why? 1


■ In these warm late twilights, look very low in the north-northwest for wintry Capella very out of season. The farther north you are, the less low it will appear. You may need binoculars, and for the South it's just gone. But if you're as far north as Montreal or either of the Portlands (Oregon or Maine), Capella is actually circumpolar.

■ Looking higher, the Big Dipper hangs way up in the northwest as the stars come out. The Dipper's Pointers, currently its bottom two stars, point to the right toward Polaris. Above Polaris, and looking very similar to it, is Kochab, the lip of the Little Dipper's bowl; the rest of the Little Dipper is dim. Kochab stands precisely above Polaris around the end of twilight.


■ Have you ever knowingly seen even a bit of the constellation Centaurus? Famous Alpha Centauri never gets above the horizon unless you’re as far south as San Antonio or Orlando (latitude 29° N). But fairly easy from much farther north is Theta Centauri, magnitude 2.0.

This evening the Moon makes it simple to find. Right after nightfall, look 19° (nearly two fists) straight down from the Moon. No other star in that area is quite as bright. Theta Cen is pale orange, as binoculars will confirm. It's at declination –36.5°, hardly farther south than the bottom of the Sagittarius Teapot. It's even 1° less far south than the familiar Cat's Eyes in the tail of Scorpius.

Theta Cen marks the top of the stick-figure Centaur's head. Add another constellation to your life list, at least of those where you've identified some fragment.


■ After nightfall is complete, Vega is the brightest star very high in the east. Barely lower left of it is 4th-magnitude Epsilon Lyrae, the Double-Double. Epsilon forms one corner of a roughly equilateral triangle with Vega and Zeta Lyrae. The triangle is less than 2° on a side, hardly the width of your thumb at arm's length.

Binoculars easily resolve Epsilon. And a 4-inch telescope at 100× or more should resolve each of Epsilon's wide components into a tight pair.

Zeta Lyrae is also a double star for binoculars; much tougher, but plainly resolved in a telescope.

Delta Lyrae, below Zeta, is a much wider and easier pair, reddish orange and pale blue.


■ The waxing gibbous Moon tonight shines among the stars of upper Scorpius as shown below. Orange Antares is about 3° or 4° to the Moon's left or lower left, and Delta Scorpii, the next brightest star in the area, is a somewhat similar distance above the Moon or to its upper right. Delta is the middle star of the upper row of three in the graphic. Cover the bright Moon with your finger to get a better look at the stars around it.

Moon crossing Scorpius, June 18-20, 2024

The nearly full Moon Wednesday night hangs with Antares and Delta Scorpii, among other stars of upper Scorpius. Delta Sco, a long-term variable, is currently much the brightest of the row of three stars above the Moon that marks Scorpius's head. (Its brightness on this map is decades old.)


■ Happy solstice! At 4:45 p.m. EDT this afternoon, the Sun reaches its farthest north position in Earth's sky and begins its six-month return southward. Astronomical summer begins in the Northern Hemisphere, winter in the Southern Hemisphere.

For us northerners, this is the year's longest day and shortest night.

It's also the day when (in the north temperate latitudes) the midday Sun passes the closest it ever can to being straight overhead, and thus when your shadow becomes the shortest it can ever be at your location. This happens at your local apparent [solar] noon, which is probably rather far removed from noon in your civil (clock) time.

And if you have a good west-northwest horizon (in mid-northern latitudes), mark carefully where the Sun sets. In a few days you should be able to detect that the Sun is once again starting to set a just little south (left) of that point.


■ Full Moon (exactly full at 9:09 p.m. EDT). After dark, cover the Moon with your finger to get a better look at the stars around it. You'll see that the Moon sits barely above the spout of the Sagittarius Teapot.

Jupiter is getting a little higher in bright dawn every morning. Even so, bring binoculars.


■ Now the Moon shines barely below the Teapot's handle through the evening hours.


■ Leo the Lion is mostly a constellation of late winter and spring. But he's not gone yet. As twilight ends look due west, somewhat low, for Regulus, his brightest and now lowest star: the forefoot of the lion stick figure.

The Sickle of Leo extends upper right from Regulus. The rest of the Lion's constellation figure runs for almost three fist-widths to the upper left from the Sickle, to his tail tip Denebola, the highest of his stick-figure's stars. Leo will soon be treading offstage into the sunset.



Mars and Saturn are in nice view just before and during early dawn. The highest and easiest is Saturn in the southeast, magnitude 1.1. Its background is dim Aquarius. Find the Great Square of Pegasus two fists upper left of it, and Fomalhaut sparkling two fists to Saturn's lower right.

Saturn with rings nearly edge-on, June 1, 2024

Saturn's rings this season are nearly edge-on! Note the stark black shadow they cast southward onto the planet. South here is up. Christopher Go, in the low-latitude Philippines, took this image shortly before sunrise on June 1st.

The rings will turn exactly edge-on March 23, 2025 — when Saturn will be too close to the Sun to observe.

Look for Mars far lower left of Saturn, by a good four or five fists at arm's length. It's almost due east. Mars is magnitude 1.9. About a fist above Mars is Alpha Arietis (Hamal), magnitude 2.0.

And Jupiter is emerging into view almost three fists lower left of Mars, shining through the horizon murk at magnitude –2.0 as dawn brightens.

Mercury, Venus, and Uranus remain hidden in the Sun's glare.

Neptune, 8th magnitude in Pisces, is about 10° lower left of Saturn before dawn begins  for the pre-dawn adventurer with large binoculars or a telescope, a detailed enough finder chart showing Neptune's current location among the many similarly faint stars, and skill in using sky charts with binocs or a scope.

Courtesy of Sky & Telescope senior editor Alan MacRobert
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