This Week's Sky at a Glance, June 4 – 12

Nova Cassiopeiae, continued: It's been 11 weeks since Nova Cas 2021 erupted to magnitude 7.7. Surprisingly, it has stayed about that bright ever since — except for swelling to 5.3, faint naked-eye visibility, for a week in early-mid May. As of June 7th it was holding at 7.0.

The nova is low-ish in the north-northeast after dark, depending on your latitude. It climbs higher through the night and is very high before dawn. Charts and comparison stars.

---

FRIDAY, JUNE 4

■ For much of the spring at our mid-northern latitudes, the Milky Way lies right down out of sight all around the horizon. But watch the east now. The rich Cepheus-Cygnus-Aquila stretch of the Milky Way looms up horizontally across the eastern sky as night advances, earlier and higher each week. A hint for the light-polluted: The Milky Way runs horizontally under Vega, right along the bottom of the Summer Triangle.

■ Make your plans for the eclipse of the Sun Thursday morning June 10th! The eclipse will be annular from sparsely populated northern Ontario through parts of the arctic. But a partial eclipse will occur during and after sunrise if you're northeast of a line from North Carolina through North Dakota. In the US Northeast and eastern Canada, the rising crescent Sun will be spectacular! You will need to scout a spot with a view to the east-northeast horizon. For details, maps, and local timetables, see Joe Rao's article in the June Sky & Telescope, page 34, or the smaller version online.

Europe and most of Russia will see the partially eclipsed Sun high in the middle of the day.

SATURDAY, JUNE 5

■ Have you ever seen Alpha Centauri? At declination –61° , our brilliant, magnitude-zero neighbor is permanently out of sight if you're north of latitude 29°. But if you're at the latitude of San Antonio, Orlando, or points south, Alpha Cen skims just above your southern true horizon for a little while late these evenings.

When does this happen? When should you look? Just about when Alpha Librae, the lower-right of Libra's two brightest stars, is due south over your landscape. At that time, drop your gaze down from there!

SUNDAY, JUNE 6

■ The early dawns and bright early mornings of the warm-weather season are a gorgeous time to enjoy the outdoors uncrowded. Habitual slugabeds don't know what they're missing. If you're one of those adventurous few — or if you have a crack-of-dawn commute — take note: Jupiter and Saturn in early dawn now form a right triangle with Fomalhaut, the out-of-season Autumn Star, way down below. Jupiter is the right angle.

MONDAY, JUNE 7

■ Mars, Pollux, and Castor form a straight line this evening. Look fairly low in the west-northwest right after dusk. Mars is the one on the left. By tomorrow, Mars will be very slightly above the line.

TUESDAY, JUNE 8

■ Here it is just 12 days to summer. But as twilight fades, look very low in the north-northwest for wintry Capella very out of season. The farther north you are, the higher it will appear. You may need binoculars. If you're as far north as Montreal or a Portland (either the one in Oregon or Maine), Capella is actually circumpolar.

WEDNESDAY, JUNE 9

■ New Moon and an annular eclipse of the Sun tomorrow morning June 10th! The eclipse will be annular only along a path from northern Ontario across parts of the arctic. But during and after sunrise, a partial eclipse will occur if you're northeast of a line from North Carolina through North Dakota.

In the US Northeast and eastern Canada, the rising crescent Sun will be spectacular! For full details, maps, and local timetables, see Joe Rao's article in the June Sky & Telescope, page 34, or the shorter version online.

Europe and most of Russia will see the partially eclipsed Sun high in the middle of the day Thursday.

Live feed from Gianluca Masi starts at 9:30 UT June 10 (5:30 a.m. EDT).

THURSDAY, JUNE 10

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

Start with Spica, its bottom. High above Spica is bright Arcturus. Almost as far upper right from Arcturus is fainter Cor Caroli, 3rd magnitude. The same distance down 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. The first to name it the "Spring Triangle" was probably Sky & Telescope columnist George Lovi, writing in the March 1974 issue. The name didn't catch on at the time, so let's try again!

■ Can you see the big Coma Berenices star cluster? Does your light pollution really hide it, or do you just not know exactly where to look? It's halfway from Cor Caroli to Denebola.

The cluster's brightest members form an inverted Y. The entire cluster is about 4° wide — a big, dim glow in a fairly dark sky, the size of a ping-pong ball at arm's length. It nearly fills a binocular view.

FRIDAY, JUNE 11

■ Bright Venus and the thin crescent Moon form a mystic pair low in the west-northwest in twilight, as shown below. They'll be 3° or 4° apart for skywatchers near the US East Coast, and only 2° by the time of twilight for the West Coast. Your best view might be about 40 or 50 minutes after sunset, before they get too low.

SATURDAY, JUNE 12

■ The Big Dipper hangs high in the northwest right after dark. The Dipper's Pointers, currently its bottom two stars, point lower right toward Polaris. Above Polaris, and looking very similar to it, is Kochab, the lip of the Little Dipper's bowl.

Kochab stands precisely above Polaris around the end of twilight or a little after. How precisely can you time this event for your location, perhaps using the vertical edge of a building?

■ After dark, look south-southeast for orange Antares, "the Betelgeuse of summer." (Both are 1st-magnitude "red" supergiants). Around and upper right of Antares are the other, whiter stars of upper Scorpius, forming their distinctive pattern. The rest of the Scorpion extends down toward the horizon.

The row of three stars upper right of Antares traditionally marks the Scorpion's head. Notice the middle one, Delta Scorpii. It's obviously brighter than the other two, right? For many years, perhaps ages, it was only a slight trace brighter than the one above it, Beta Scorpii. Then in July 2000 Delta nearly doubled in brightness, changing the whole look of upper Scorpius. And it has stayed bright for most of the years ever since, with fluctuations.

---

This Week's Planet Roundup

Mercury is out of sight in inferior conjunction with the Sun.

Venus (magnitude –3.8, in lower Gemini) shines low in the west-northwest during twilight. Catch it while you can; it sets before twilight ends.

Mars (magnitude +1.7, in upper Gemini) glows modestly low in the west-northwest right after dark, upper left of Venus and left of Pollux and Castor.

Mars starts the week below the Pollux-Castor line as shown at the top of this page. It crosses the line on June 7th.

Mars is almost as far away as it gets on the far side of its orbit from us. So it's no brighter than even Castor, the fainter of the Pollux-and-Castor "twins." And in a telescope, Mars is just tiny blob 4 arcseconds wide.

Jupiter and Saturn (in dim Aquarius and Capricornus, respectively) rise around 1 a.m. and midnight, respectively (daylight-saving time). By the first glimmer of dawn they're fairly high in the southeast, nearly as high as they will get. Jupiter dominates at magnitude –2.5. Saturn, 18° to Jupiter's right, is a more modest mag +0.5.

Uranus remains out of sight in the glow of dawn.

Neptune, in Aquarius 21° east of Jupiter, lurks at 8th magnitude low in the east-southeast just before dawn.

---

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 that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time, EDT, is Universal Time minus 4 hours. Universal Time is also known as UT, UTC, GMT, or Z time. To become more expert about time systems than 99% of the people you'll ever meet, see our compact article Time and the Amateur Astronomer.

---

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 an easy-to-use 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 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 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 magnitude 9.75). And be sure to read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger (and illustrated) Night Sky Observer's Guide by Kepple and Sanner.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically, meaning heavy and expensive. 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."

---

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

---

"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

 

---