Sky at a Glance | August 26th, 2011

By: Alan MacRobert August 26, 2011 0

Supernova 2011fe brightens from nothing in these early images taken with the 48-inch (1.2-m) Schmidt telescope at Palomar Observatory on the evenings of August 22, 23, and 24, 2011. Click here for larger views. As of August 29th, the supernova had become brighter than the galaxy's nucleus in amateur telescopes.

Supernova in M101. A supernova for backyard telescopes continues brightening in M101, the Pinwheel Galaxy off the Big Dipper's handle. Supernova 2011fe was discovered at magnitude 17.2 on August 24th, reached 13.8 on the 25th, and 12.5 on the 27th. On the American evening of the 29th (August 30.1 UT) I estimated it at magnitude 11.5 using a 12.5-inch scope at 75× and an AAVSO comparison-star chart. It was more readily visible than the galaxy itself in my moderately light-polluted suburban sky. Then on the evening of the 30th Tony Flanders put it at 11.2. On the evening of the 31st it was about 10.8. No sign of stopping yet!

The supernova should top out at about magnitude 10.6 if it's a standard Type Ia, as seems to be the case. See our article, Supernova Erupts in Pinwheel Galaxy. Plan to observe soon after dark while the Dipper's handle is still high.

Friday, Aug. 26

Jupiter's Great Red Spot (currently pale orange) should be crossing the planet's central meridian around 3:09 a.m. Saturday morning EDT.

Saturday, Aug. 27

The two brightest stars of summer are icy white Vega, now high overhead at dusk (if you live in the mid-northern latitudes), and Arcturus, pale yellow-orange, shining lower in the west. One-third of the way down from Vega to Arcturus is the Keystone of Hercules. Two-thirds of the way is the semicircle of Corona Borealis, the Northern Crown.

Sunday, Aug. 28

Vega, the "Summer Star," crosses closest to your zenith around 9 p.m. depending on how far east or west you live in your time zone. How accurately can you time this event? Vega passes right through your zenith if you're at north latitude 39° (Washington DC, Cincinnati, St. Louis, Topeka, south of Denver).

New Moon (exact at 11:04 p.m. EDT).

Monday, Aug. 29

Cygnus has a reputation for being poor in deep-sky objects despite its Milky Way richness. Maybe that's because you've never tried teasing out the Berkeley clusters at the center of the Northern Cross. See Sue French's Deep-Sky Wonders article, charts, and photos in the September Sky & Telescope, page 56.

Tuesday, Aug. 30

As soon as the stars come out, the Great Square of Pegasus is up in the east. It's balancing on one corner, a little larger than your fist at arm's length.

Michael Romo of Los Angeles writes in, "Did you know that the western stars of the Great Square of Pegasus are almost directly opposite the Pointers of the Big Dipper? Find the Great Square low in east, and follow a line from its left star through its top star. The line passes through Polaris and on to the Pointers of the Big Dipper low in the northwest."

A temporary "Southwest Triangle." The visibility of objects in bright twilight is exaggerated here. This arrangement is exact for an observer in the middle of North America.

Sky & Telescope diagram

Wednesday, Aug. 31

Low in twilight, look for Spica to the upper left of the thin crescent Moon, and Saturn to the Moon's upper right. Binoculars will help.

Thursday, Sept. 1

As early as nightfall now, Cassiopeia has risen as high in the northeast as the Big Dipper has sunk in the northwest.

Friday, Sept. 2

Wait up till midnight, and you'll find Jupiter blazing in the east and Capella, one of the brightest stars in the sky, shining in the northeast. Find the midpoint between them. A little lower-right from that point is the Pleiades star cluster.

The waxing Moon marches above Scorpius and Sagittarius as they decline at dusk. For clarity, the Moon is shown three times its actual apparent size.

Sky & Telescope diagram

Saturday, Sept. 3

Look for orange-red Antares — a summer star on its way out for the year — well to the left of the Moon low in the southwest as twilight fades, as shown above.

Right next to the Moon, binoculars and telescopes help show 2nd-magnitude Delta Scorpii in Scorpius's head. The Moon occults (covers) Delta Sco as seen from parts of the southern and eastern U.S. — though in the eastern part of this zone, the event will happen very low in the sky. Details.

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).

Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.

Alan MacRobert

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

If you have any doubt that stacked-video imaging can do black magic on planets, compared to what you can see by eye in the same telescope, look at this. Mars was a mere 4.5 arcseconds wide on August 13th when John Boudreau of Saugus, Massachusetts, took this image with an 11-inch scope. Visually, Mars at that size is a tiny, featureless fuzzblob.

Click for animation of two images showing 7 minutes of the planet's rotation. This makes it easy to see what features here are real rather than noise. Hint: Most of them are.

Boudreau used a C-11 telescope at f/38 with a PGR Flea 3 camera and Astrodon RGB color filters. He rated the seeing only 6 or 7 on a scale of 10. And the planet was only 32° high. (South is up.)

John Boudreau

Mercury is emerging into view low in the dawn, brightening day by day. Look for it low in the east about an hour before sunrise; the later in the week the better. It's far down below Mars, Castor, and Pollux.

Venus is hidden in the glare of the Sun.

Mars (magnitude +1.4, crossing Gemini) rises around 2 a.m. daylight-saving time. By the beginning of dawn it's in good view well up in the east, to the right of Castor and Pollux. In a telescope, Mars is just a tiny blob only 4.7 arcseconds in diameter.

Jupiter (magnitude –2.6, in southern Aries) rises in the east-northeast around 10 p.m. daylight saving time. Look above it for the little star pattern of Aries and (once Jupiter is well up) closer below it for the head of Cetus, rather dim. Jupiter shines highest in the south just before dawn, making this the best time to examine it with a telescope. It's 44 arcseconds wide.

Saturn (magnitude +0.9, in Virgo) sinks down to the western horizon during twilight. Look for it far below high, bright Arcturus. Binoculars help. Left of Saturn by 10° twinkles Spica.

Another amazing stacked-video shot, taken by Christopher Go on August 29th. Jupiter's dark-rimmed Great Red Spot is upper left of center. Lower right of center, note the very dark red oval in the North Equatorial Belt. South is up.

Christopher Go

Uranus (magnitude 5.8, in western Pisces) and Neptune (magnitude 7.8, in western Aquarius) are well up in the south and southeast before midnight. Use our printable finder chart for both.

Pluto (magnitude 14.0, in northern Sagittarius) is still in the south-southwest right after dark; don't delay. A big finder chart for it is 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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