This Week's Sky at a Glance, April 26 – May 5

Supernova in NGC 3621 in Hydra. Supernova 2024ggi, discovered on April 11th while still faint, quickly reached visual magnitude 12.0 and has stayed close to that so far (12.2 as of as of April 30th). Check the AAVSO's table of recent observations for the latest.

The 10th-magnitude galaxy with its new pinpoint is in the evening sky rather far south at declination –33°. Conveniently, NGC 3621 now crosses the meridian about an hour after dark. For more info and finder charts see Bob King's Jupiter meets Uranus in twilight; Supernova erupts in nearby galaxy. "Near" is relative; it's 22 million light-years away.

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FRIDAY, APRIL 26

■ Saturn and Mars continue to widen in the dawn this week, as they rise into slightly better view low in the east-southeast as shown below.

SATURDAY, APRIL 27

■ Vega, the Summer Star — the zero-magnitude equal of the Spring Star Arcturus high in the east — is on its way up low in the northeast after nightfall. Depending on your latitude. The farther north you are the higher it will be. If you're in the latitudes of the southern U.S., you'll have to wait until a bit later after dark for it to appear.

SUNDAY, APRIL 28

■ The long, dim sea serpent Hydra snakes almost level far across the southern sky. Find his head in the southwest. It's almost halfway from Procyon to Regulus, a rather dim asterism about the width of your thumb at arm's length.

Left or lower left of Hydra's head, by about a fist and a half, is orange, 2nd-magnitude Alphard, his lonely heart.

Hydra's dim, irregular body and tail stretch all the way to Libra just risen in the southeast. He carries Crater and Corvus on his back.

Below Crater, in Hydra's most southerly part, is the new 12th-magnitude supernova in the 10th-magnitude galaxy NGC 3621. For finder charts, see the top of this page.

MONDAY, APRIL 29

■ Face north just after nightfall, look very high, and you'll find the Pointers, the end stars of the Big Dipper's bowl, on the north meridian pointing toward Polaris straight down below. From the Pointers to Polaris is about three fists at arm's length.

TUESDAY, APRIL 30

■ The last-quarter Moon rises around 2 or 3 a.m. tonight, depending on your location. Before Wednesday's dawn it shines low in the southeast, in southern Capricornus. It turns exactly first quarter at 7:27 a.m. Wednesday EDT; 4:27 a.m. PDT.

WEDNESDAY, MAY 1

■ Although it's May now, wintry Sirius still twinkles very low in the west-southwest at the end of twilight. It sets soon after. Hint: Find Sirius far below Procyon and a bit left. Procyon is the bright star lower left of Pollux and Castor.

How much longer into the spring can you keep Sirius in view? In other words, what will be its date of "heliacal setting" as seen by you?

THURSDAY, MAY 2

■ Summer is still seven weeks away, but the Summer Triangle is beginning to make its appearance in the east, one star after another. The first in view is bright Vega. It's already visible low in the northeast as twilight fades.

Next up is Deneb, lower left of Vega by about two fists at arm's length. Deneb takes an hour or so to appear after Vega does.

The third is Altair, which shows up far to their lower right by midnight.

FRIDAY, MAY 3

■ After sunset, use binoculars or a wide-field telescope to try for a last look at Jupiter. It's just above the west-northwest horizon in moderately bright twilight, as shown below. If you succeed, you will be among the last few people on Earth to see the giant planet so close to the end of its 2023-24 apparition.

■ On the opposite side of the Sun, low in dawn Saturday morning, the waning crescent Moon hangs between Saturn to its upper right and Mars to its left or lower left.

SATURDAY, MAY 4

■ The Eta Aquariid meteor shower, bits of the rubble stream shed by Halley's Comet, often presents the best meteor display of the year for the Southern Hemisphere. But for us northerners the shower's radiant point is still quite low even as dawn begins. Nevertheless, meteor watchers in the southern U.S. may catch the brief death streaks of a few Halley bits before dawn on May 5th and 6th. See the May Sky & Telescope, page 48.

SUNDAY, MAY 5

■ A gigantic spring asterism you may not know is the Great Diamond, some 50° tall and extending over five constellations. It now stands upright in the southeast to south after dusk.

Start with Spica, its bottom. Upper left from Spica is bright Arcturus. Almost as far upper right from Arcturus is fainter Cor Caroli, 3rd magnitude. The same distance lower right from there is Denebola, the 2nd-magnitude tailtip of Leo. And then back to Spica. Robert H. Baker may have been the first to name the Great Diamond, in his 1954 book When the Stars Come Out.

The bottom three of these stars, the brightest, form a nearly perfect equilateral triangle. We can call this the "Spring Triangle" to parallel to those of summer and winter. The first to name it such was probably the late Sky & Telescope columnist George Lovi, writing in the March 1974 issue and again in May 1977. It didn't really catch on. Let's try again.

Haze on the Diamond's edge: If you have a dark sky, or binoculars, look halfway from Cor Caroli to Denebola for the very large, sparse Coma Berenices star cluster. It spans some 4°, about the size of a ping-pong ball held at arm's length.

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This Week's Planet Roundup

All seven planets other than Earth are currently crowding near our line of sight to the Sun. Not one of them is easy!

Mercury, Venus, and Neptune are completely hidden in the glare of sunrise.

Mars and Saturn, both about magnitude +1.2, rise at the beginning of dawn. Try for them low above the east-southeast horizon about 60 to 50 minutes before sunrise, as shown near the top of this page. Saturn is the less difficult one, on the upper right. They widen from 11° apart on the morning of April 27th to 16° on May 4th.

Jupiter, magnitude –2.1, is very low above the west-southwest horizon in mid-twilight. Bring binoculars. It sets well before twilight ends.

Uranus, magnitude 5.8, is lost in twilight near Jupiter.

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All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions and graphics that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time minus 4 hours. UT is also known as UTC, GMT, or Z time.

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Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For a more detailed constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.

Once you get a telescope, to put it to good use you'll need a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows all stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to mag 9.75). And read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.

You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.

Can computerized telescopes replace charts? Not for beginners I don't think, especially not on mounts and tripods that are less than top-quality mechanically. Unless, that is, you prefer spending your time getting finicky technology to work rather than learning the sky. And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

If you do get a computerized scope, make sure the drives can be disengaged so you can swing it around and point it readily by hand when you want to, rather than only slowly by the electric motors (which eat batteries).

However, finding faint telescopic objects the old-fashioned way with charts isn't simple either. Learn the tricks at How to Use a Star Chart with a Telescope. 

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Audio sky tour. Out under the evening sky with your
earbuds in place, listen to Kelly Beatty's monthly
podcast tour of the naked-eye heavens above. It's free.

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"The dangers of not thinking clearly are much greater now than ever before. It's not that there's something new in our way of thinking, it's that credulous and confused thinking can be much more lethal in ways it was never before."
            — Carl Sagan, 1996

"Facts are stubborn things."
            — John Adams, 1770

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