Sky at a Glance | May 27th, 2011

By: Alan MacRobert May 27, 2011 0

Friday, May 27

With summer less than a month away, the big Summer Triangle is making its appearance in the east. Its topmost and brightest star is Vega, plain to see. Look lower left of Vega, by two or three fist-widths at arm's length, for Deneb, the brightest star in that area. Farther to the lower right of Vega is Altair, the last of the three Summer Triangle stars to rise (around 10 or 11 p.m. daylight saving time, depending on your location).

Watch the Moon pass over the dawn planet lineup in the closing days of May. (The visibility of the fainter objects in bright twilight is exaggerated here. These scenes are always drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date.)

Sky & Telescope diagram

Saturday, May 28

Before sunrise tomorrow morning, look for the waning crescent Moon hanging above Jupiter. Use binoculars to check out the changing planetary array to their lower left, as shown here.

Late tonight a 7th-magnitude star in Ophiuchus should be occulted for up to 11 seconds by the faint asteroid 217 Eudora as seen from a track running from Florida through Oklahoma and Colorado to Oregon. See map, finder charts, and full information.

Sunday, May 29

We're still almost a month from summer, but summery Scorpius is already rearing up in the southeast these evenings. Its brightest star is fiery Antares. Look for the other, whiter stars of upper Scorpius on either side of Antares and farther to its upper right.

Libra, the next constellation west of Scorpius, reaches the meridian in the south not long after dark. Libra's lower portion contains the big dark asteroid Hygiea, magnitude 9.3, just waiting for you to hunt it out. See the article and finder chart in the May Sky & Telescope, page 56.

Early Monday morning an unusually bright star, 4.9-magnitude Nu Pegasi, will be occulted for up to 1.2 seconds by the small asteroid 4569 Baerbel along a thin track (only 9 miles wide!) running from southernmost California through Arizona, Colorado, and the Dakotas. The star will be low in the southeast. Maps and details.

Monday, May 30

Saturn's biggest and brightest satellite, Titan, is about four ring-lengths east of the planet tonight.

Tuesday, May 31

The brightest star in the east these nights is Vega. You can't miss it. Look for the little triangle-and-parallelogram pattern of the constellation Lyra dangling to its lower right.

The galaxies of the great Virgo Cluster are numerous but not that bright as Messier objects go. Nevertheless, if you have a dark sky, even binoculars are enough for you to hunt for ten of them as very faint smudges west of Epsilon Virginis. Use Gary Seronik's Binocular Highlight column and finder chart in the May Sky & Telescope, page 45.

The four-planet lineup before sunrise continues to lengthen, with Jupiter moving farther to the upper right and Mercury to the lower left. The 10° scale is about the width of your fist at arm's length.

Sky & Telescope diagram

Meanwhile, the dawn planet lineup continues to lengthen in the east, with Jupiter now very plain and easy.

Wednesday, June 1

Saturn (with Porrima next to it) and Spica draw the eye in the south after dusk. But don't forget Corvus, the Crow, below them. Corvus's uppermost bright star, Delta Corvi, is a wide telescopic double: magnitudes 3.0 and 9.2, separation 25 arcseconds.

New Moon (exact at 5:03 p.m. EDT). A partial eclipse of the Sun will be visible from much of the arctic. Parts of Japan, Alaska, and the Canadian Maritimes will also experience a very slight partial eclipse. Maps and details.

Thursday, June 2

Saturn and Porrima have now closed to 17 arcminutes of each other, practically as close as they will get. Although they look like neighbors, Saturn is only 76 light-minutes from Earth, while Porrima is 39 light-years in the background. That's more than a quarter million times farther away!

The waxing Moon adorns the western twilight.

Sky & Telescope diagram

Friday, June 3

Look west in twilight for thin waxing crescent Moon far below Pollux and Castor, as shown here.

Are you light-polluted where you live? Most of us are. But don't be discouraged by the astronomy you can't do, concentrate on what you can. For instance, see Hugh Bartlett's "Binocular Sights for City Nights," with finder photos, in the June Sky & Telescope, page 52.

Saturday, June 4

In twilight, look for Pollux and Castor to the upper right of the Moon, and look for Procyon disappearing about equally far to the Moon's lower left, as shown here.

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

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. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.

Sky & Telescope

Once you get a telescope, to put it to good use you must have a detailed, large-scale sky atlas (set of charts). The standards are the Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger Sky Atlas 2000.0 (stars to magnitude 8.5); and the even larger and deeper Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts effectively.

You'll also want a good deep-sky guidebook, such as Sky Atlas 2000.0 Companion by Strong and Sinnott, or the more detailed and descriptive Night Sky Observer's Guide by Kepple and Sanner, or the classic if dated Burnham's Celestial Handbook.

Can a computerized telescope take their place? I don't think so — not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. 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."

This Week's Planet Roundup

Jupiter is climbing higher now at the beginning of dawn for better telescopic viewing, but it's still far from its best. Christopher Go obtained this fine stacked-video image anyway on June 1st. It shows that Jupiter's dark South Equatorial Belt (above center) has fully returned and is very wide and turbulent. The North Equatorial Belt remains darker red-brown. The Great Red Spot is at left, with the SEB practically emcompassing it. The normally white Red Spot Hollow around it is now dark. South is up.

Alan MacRobert

Low in the dawn, Mercury, Venus, Mars, and Jupiter continue drawing farther apart in a long diagonal line. Jupiter is the highest and easiest. Far to its lower left are faint Mars, then bright Venus, and then very-low Mercury, as shown in the scenes above. Bring binoculars for Mars and Mercury. (See our daily animation, which runs through June 1st. Pause the animation at the date of your choice.)

Saturn (magnitude +0.6, in Virgo) is in excellent evening view high in the south. And just 1/3° to its right or upper right is fainter Porrima (Gamma Virginis), turning Saturn into a striking naked-eye "double star"! Meanwhile, Spica shines 14° to Saturn's lower left or left.

Saturn's white activity continues in the planet's northern hemisphere, as seen in this image taken by Christopher Go on May 30th. South is up. This image was created from stacked, selected video frames (taken with an 11-inch scope); don't expect to see this much detail visually!

Christopher Go

In a telescope Saturn's rings are 7.3° from edge on, their minimum tilt for more than a decade to come. The rings are casting a relatively wide, prominent black shadow southward onto the globe, and the globe's shadow on the rings is visible just off the globe's celestial east (following) side. Saturn's six-months-old white outbreak is still active, as shown here. Read more about this storm as studied from the Cassini Saturn orbiter and the Very Large Telescope in Chile.

See how many of Saturn's satellites you can identify in your scope using our Saturn's Moons tracker.

And don't skip over Porrima, which is now in the same low- or medium-power telescopic field! It's it's a fine, close telescopic binary star with equal components and a current separation of 1.7 arcseconds. Use high power and hope for good seeing. Saturn and Porrima will appear closest together (¼° apart) from June 6th through 12th. See the article in the April Sky & Telescope, page 56.

Uranus (magnitude 5.9, in western Pisces) is low in the east before the first light of dawn.

Neptune (magnitude 7.9, in Aquarius) is in the southeast before dawn.

Pluto (magnitude 14 in Sagittarius, and back here by popular request) is highest in the south before dawn. A finder chart for it will appear in the July Sky & Telescope, page 64.

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) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

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About Alan MacRobert

Alan M. MacRobert became an avid Sky & Telescope subscriber in 1966 at age 14, joined the editorial staff in 1982, and is now a senior contributing editor, semi-retired. He played a role in practically every part of the magazine and the company's other products for more than a generation, both on the amateur-observing side and the science-reporting side. In 1994 a book collection of his observing how-tos and telescopic sky tours was published as Star Hopping for Backyard Astronomers. He has produced This Week's Sky at a Glance online every week since 1989.