This Week's Sky at a Glance, May 27 – June 4

FRIDAY, MAY 27

■ Bright Capella sets low in the northwest fairly soon after dark these evenings; how soon depends on your latitude. That leaves Vega and Arcturus as the brightest stars in the evening sky. Vega shines in the east-northeast. Arcturus is now very high toward the south.

A third of the way from Arcturus down to Vega, look for semicircular Corona Borealis, with 2nd-magnitude Alphecca as its one moderately bright star.

Two thirds of the way from Arcturus to Vega is the dim Keystone of Hercules, now lying almost level.

Use binoculars or a telescope to examine the Keystone's top edge. A third of the way from its left end to the right is 6th-magnitude M13, one of Hercules's two great globular star clusters. In binoculars it's a tiny glowing cotton ball. A 4- or 6-inch scope begins to resolve some of its speckliness. Located 22,000 light-years away high above the plane of the Milky Way, it consists of several hundred thousand stars in a swarm only about 140 light-years wide.

SATURDAY, MAY 28

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

When to look for it? Just about when Alpha Librae, the lower-right of the two brightest stars of Libra, is due south over your landscape. At that time, drop your gaze down from there!

■ Bright Jupiter and fainter Mars are in conjunction, 0.6° apart, in early dawn Sunday morning May 29th as shown below. Look east-southeast. Binoculars help as dawn brightens.

SUNDAY, MAY 29

■ For much of the spring at 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 starts rising up all across the east late these nights, earlier and higher every week.

A hint for the light-polluted: It runs horizontally under Vega, right through the lower part of the Summer Triangle.

MONDAY, MAY 30

■ Strong new meteor shower tonight?? A stream of meteoroids from the broken-up periodic comet Schwassman-Wachmann 3 may produce many slow meteors in the sky tonight. They'll trace back to a radiant (perspective point of origin) near Arcturus — not Tau Herculis as originally assumed. Meteor researchers predict that any activity should last for just a few hours centered on 5:00 UT May 31st (1 a.m. May 31st EDT; 10 p.m. May 30th PDT). The event will be either "all or nothing," suggests Bill Cooke of NASA’s Meteoroid Environment Office. There will be no Moon.

See Joe Rao's article on page 34 of the May Sky & Telescope and his New Update on a Possible Outburst of Meteors online. His original research paper: Will Comet 73P/Schwassman-Wachmann 3 produce a meteor outburst in 2022?

The International Meteor Organization has a page set up that will display the shower's activity profile coming together as the group's meteor counters (who use the same standard observing methods so their counts will be inter-comparable) submit their post-observing reports.

■ New Moon (exact at 7:30 a.m. EDT on this date).

TUESDAY, MAY 31

■ Constellations seem to twist around fast when they pass your zenith — if you compare them to the direction "down." Just a week and a half ago, the Big Dipper floated horizontally in late twilight an hour after sunset (as seen from 40° north latitude). Now it's angled diagonally at that time. In just another week and a half it will be hanging straight down by its handle!

WEDNESDAY, JUNE 1

■ As twilight fades, look low in the west for the thin crescent Moon. It's in lower Gemini down under Pollux and Castor, as shown below.

Look left of the Moon by 25° (roughly 2½ fists at arm's length) for Procyon. Shown below is how they'll appear from latitude 40° in North America, for instance New York and Denver. From the southern U.S., Procyon will appear higher than it does here. From higher latitudes, Procyon will appear lower than shown here.

THURSDAY, JUNE 2

■ Spot the crescent Moon in the west after sunset, as shown above. How soon, as twilight fades, can you first make out Pollux above the Moon, then Castor to the right of Pollux? Pollux is the brighter one at magnitude 1.15, while Castor is magnitude 1.58 (the combined magnitude of Castor A and B; it's a telescopic double). In other words, Castor is only 67% as bright as Pollux: one third dimmer.

So, for how many minutes does twilight have to fade from when you first detect Pollux until you first detect Castor?

FRIDAY, JUNE 3

■ Now the growing Moon shines upper left of Pollux and Castor (by about one fist) as shown above.

■ After dark, Vega shines as 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 any telescope.

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

SATURDAY, JUNE 4

■ After dark, the crescent Moon forms a long isosceles (two sides equal) triangle with Regulus and Gamma Leonis (a little fainter) to the Moon's upper left. The Moon is at the long end of the triangle.

Tomorrow evening the triangle will be much shorter and flatter, but still isosceles.

 

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This Week's Planet Roundup

Mercury is hidden deep in the glow of sunrise.

Venus (magnitude –4.0) rises soon after the beginning of dawn. Look for it just left of due east. It's roughly three fists at arm's length lower left of Jupiter.

Venus will continue to rise around the beginning of dawn from now all the way through August.

Mars and Jupiter, very different at magnitudes +0.7 and –2.2 respectively, shine close together before and during dawn in the east-southeast. They start the week in conjunction — exactly so on May 29th, when they'll be 0.6° apart as shown near the top of this page. Thereafter, little orange Mars slowly pulls away from brilliant Jupiter. You'll find it 3½° lower left of Jupiter by the morning of June 3rd.

Saturn, magnitude +0.7, glows in eastern Capricornus a good 40° (about four fists) right or upper right of Jupiter before dawn. The little star 2° to Saturn's lower right is Delta Capricorni, magnitude 2.8.

Uranus is buried in the eastern dawn.

Neptune, magnitude 7.9, is some 9° west (right) of Jupiter before dawn begins.

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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. (Universal Time is also called UT, 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 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 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 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."

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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 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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