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Send us your astronomy questions

Liz Kruesi — Wed, 15 Jul 2009 21:05:00 GMT

Perplexed by planets? Confused by cosmology? Baffled by black holes? Then send in your questions to Astronomy magazine at askastro@astronomy.com.

If you have an astronomy question about observing, the planets, stars, cosmology, or astronomy history, send it in! Five are selected each month for publication in the Ask Astro section of Astronomy magazine. If your question is selected, we will forward it to an expert for his or her response. Then, the question and answer will appear together in a future issue. We may edit or revise your question for clarity.

We aren’t always able to respond to questions individually. But please keep the questions coming — they help us to learn what our readers are interested in, and what topics we should consider for future coverage in the magazine.

New videos: Springtime observing targets

Rich Talcott — Tue, 10 Mar 2009 21:10:00 GMT

In this video, I discuss the objects you can see with your naked eyes and binoculars in this spring’s sky. The season offers several bright planets, notable constellations, and bright deep-sky objects. You can locate all the night-sky sights I talk about with Astronomy.com's interactive star chart StarDome.

Watch the video, "Observe easy-to-find objects in the spring sky."

Venus

As darkness falls during the first half of March, your eyes will be drawn to the western sky. In the deepening twilight, Venus gleams like nothing else. You won’t have any trouble identifying the brilliant planet, which glows brighter than any other point of light in the sky. Venus passes between the Sun and Earth in late March, and will reappear in the east before dawn by mid-April.

Saturn

Beautiful Saturn also lies in the evening sky, although it doesn’t stand out like Venus. Look for Saturn among the background stars of Leo the Lion, where it glows as bright as that constellation’s brightest star, Regulus. Saturn will remain in the evening sky until late summer.

Mercury

Elusive Mercury puts on its best evening show of the year in the last 10 days of April. Watch for a bright point of light low in the west-northwest 30 to 45 minutes after the Sun sets. The easiest evening to spot it will be April 26, when it lies directly below a crescent Moon.

Jupiter

Meanwhile, Jupiter appears conspicuous in the morning sky during April and May. Look for it in the southeast around the time twilight starts to paint the sky. Only the planet Venus shines brighter than Jupiter.

The Big Dipper

Spring’s starry background has its own charm. Those of us in the Northern Hemisphere have a signpost in the spring sky: the bright asterism of the Big Dipper. Seven bright stars in the constellation Ursa Major the Great Bear create the Dipper’s shape. On spring evenings, the Dipper stands nearly overhead, at the center of this star chart.

Use the two stars at the end of the Dipper’s bowl, called the Pointers, to lead you to the North Star, Polaris. Extend the line between the Pointers (which lie at the bottom left of this photo), and extend it about five times that distance. Polaris is the brightest star in the Little Dipper and forms the tip of its handle.

Head back to the Big Dipper and take a close look at the middle star in the handle, called Mizar. If you have decent eyesight, you should see a fainter companion star just to its east. If you can’t see it, turn your binoculars on this star and its double nature will stand out.

Now, let’s use the Big Dipper to find some of spring’s other celestial delights.

If you follow the arc of the Dipper’s handle away from the bowl, you’ll soon arrive at Arcturus — the brightest star in the spring sky. Continue the arc about an equal distance and you’ll find Spica, the brightest star in the constellation Virgo. Spica dominates this sprawling constellation, and has the distinction of being the bluest of all 1st-magnitude stars. When it comes to stars, blue means hot, and Spica’s surface blazes at a temperature nearly four times hotter than the Sun.

Next, head back to the Big Dipper, and imagine poking a hole in the bottom of its bowl. The water would flow out and fall on the back of Leo the Lion. Leo consists of two distinctive sections: A group of six stars on the right that looks like a backward question mark, and three stars on the left that form a right triangle. Remember that Saturn augments the Lion’s shape this year, just below the pattern seen here.

Our final stop in the spring sky lies one constellation west of Leo, in the faint group known as Cancer the Crab. Smack in the middle of this constellation lies perhaps the spring sky’s finest binocular target: the Beehive star cluster (M44). On exceptionally clear nights from a dark site, you might spot the Beehive with your naked eyes. Binoculars reveal the cluster’s true nature. Through 10x50 binoculars, you should be able to see at least two dozen stars packed into a circle some three times wider than the Full Moon. It’s a sight you won’t soon forget.

We’ve created two more videos like this one to help you enjoy everything the springtime sky has to offer.

Astronomy magazine Senior Editor Michael Bakich’s video “Springtime observing for small telescopes” highlights this year’s best springtime targets you can see with a 4-inch or smaller telescope.

Astronomy magazine Editor Dave Eicher’s video “Springtime observing for large telescopes, 2009” highlights this year’s best springtime deep-sky objects you can see with an 8-inch or larger telescope. Both of these videos are available for Astronomy magazine subscribers at Astronomy.com/videos.

I’ll be back again this summer to talk about what’s on view during the warmest nights of the year.

February 27-March 6, 2009: constellation Columba, globular cluster NGC 1851, and spiral galaxy NGC 1808

Michael Bakich — Thu, 26 Feb 2009 20:46:00 GMT

Here is the transcript for my podcast about how to see constellation Columba, globular cluster NGC 1851, and spiral galaxy NGC 1808 this week.

Check out the Astronomy.com's interactive star chart to see an accurate map of your sky. It'll help you locate some of this week's key targets. Astronomy magazine subscribers have access to a slew of cool functions with StarDome PLUS.

Each week, I highlight three different night-sky targets for you to see:

One object you can find with your naked eyes or through binoculars
One object to find with a small telescope
One deep-sky object to find with an 8-inch or larger telescope for you avid astronomers

--Start transcript--

Biblical astronomy
This week’s naked-eye object is the constellation Columba the Dove. Specifically, it represents the dove that Noah sent out to test whether the waters from the great biblical flood had receded. It’s the only surviving constellation named after an object in the Bible. Columba first appeared in 1592, on a celestial map designed by Dutch astronomer and cartographer Petrus Plancius.

Columba is a constellation most amateur astronomers haven’t identified. Well, here’s your chance. Find Orion. That’s easy enough. Now look south of Orion, and find Lepus. I showed you how to locate this constellation 5 weeks ago. Finally, continue south from Lepus, and you’ll end up in Columba.

You’ll first notice the constellation’s two brightest stars. Phact (Alpha [α] Columbae) shines at magnitude 2.6, and Wasn (Beta [β] Columbae) isn’t far behind at magnitude 3.1. From there, use a star chart to find just three other stars brighter than 4th magnitude. Then all you have to do is make a dove out of those stars. Good luck.

When you look at Columba, you might want to wave goodbye. This constellation contains the point in the sky away from which our solar system is heading, relative to stars in our neighborhood. Astronomers call this point the solar antapex.

For those of you with large telescopes, there’s something at the approximate coordinates of the solar antapex. It’s the magnitude 13.2 galaxy IC 2153. Warning: Unless you can set up a large telescope at a dark site, you won’t have much luck observing this small faint object.

Alone in the dark
This week’s small telescope target is globular cluster NGC 1851 in Columba. It sits nearly 8° southwest of Phact, but you’ll see it easily from a dark site through binoculars. This magnitude 7.0 globular is the brightest deep-sky object for more than 20° in any direction.

Through a 4-inch telescope, you’ll see a concentrated core that you can’t resolve surrounded by many stars you can.

NGC 1851’s core is difficult to resolve through large telescopes as well because of its distance. It lies 40,000 light-years from the Sun and 55,000 light-years from the Milky Way’s center.

Bright, but few details
This week’s deep-sky object completes my trio of “Columba” objects. It’s spiral galaxy NGC 1808. This galaxy shines relatively brightly at magnitude 9.9.

NGC 1808 is easy to see and accepts high magnifications well because it has a high surface brightness. The galaxy’s oval shape — twice as long as it is wide — is apparent, but you’ll only see the initial stubs of the faint spiral arms that long-exposure images show stretching around NGC 1808’s entire length.

Through a 16-inch or larger telescope, crank up the power, and try to see the dark lanes near the galaxy’s outer edge. Astronomers recently discovered this galaxy has a high amount of star-formation occurring within it.

For those of you with the largest amateur scopes, three challenging galaxies lie roughly 10' southeast of NGC 1808. The brightest, PGC 620467, glows weakly at magnitude 15.6. The other two, PGC 131395 and PGC 16804, are really faint. Both of these galaxies have magnitudes of 15.9.

---End transcript--

Previous episode: Beehive Cluster, open cluster M50, and the Rosette Nebula
Previous transcript

February 13-20, 2009: Open cluster M41, the Tau Canis Majoris Cluster, and Thor’s Helmet

Michael Bakich — Thu, 12 Feb 2009 19:45:00 GMT

Here is the transcript for my podcast about how to see open cluster M41, the Tau Canis Majoris Cluster, and Thor’s Helmet this week.

Each week, I highlight three different night-sky targets for you to see:

One object you can find with your naked eyes or through binoculars
One object to find with a small telescope
One deep-sky object to find with an 8-inch or larger telescope for you avid astronomers

--Start transcript--

Follow the brilliant guide
This week’s naked-eye object is open cluster M41, which lies in Canis Major the Great Dog. It’s easy to find M41 on any clear winter night. First, find Sirius (Alpha [α] Canis Majoris), the night sky’s brightest star. Then look 4° due south.

Because it glows at magnitude 4.5, most observers should be able to pick out M41 easily with their naked eyes under a dark sky. This cluster lies 2,000 light-years away and measures about 20 light-years across.

Now just because you can see M41 without optical aid doesn’t mean you shouldn’t point your binoculars or telescope at it. Even a low-power view reveals dozens of stars with a 7th-magnitude orange gem at the cluster’s center.

Train your telescope on Tau
This week’s small telescope target is the Tau (τ) Canis Majoris Cluster, also known as NGC 2362. From M41, move 8.6° east-southeast. With unaided eyes, you’ll notice a glow around the 4th-magnitude star Tau CMa. When you point your telescope at this object, however, you’ll have a whole new perspective.

Tau CMa forms the centerpiece of this terrific star cluster. A 4-inch scope will show stars in three tiers of brightness. First, there’s brilliant Tau. Then, 3 magnitudes fainter, a half-dozen other stars catch your gaze. Finally, you’ll spot the faintest stars, which glow at 10th magnitude. Look closely for the tight group of these stars spanning 6' that surrounds Tau. Don’t let the brilliance of the principal luminary deter you.

For Asgard!
This week’s deep-sky object is my choice for “best-named” celestial target — Thor’s Helmet. Some historical illustrations (and the entire 600-issue run of the Marvel Comics’ superhero epic) picture the Norse thunder god Thor wearing a winged helmet. Well, through a large scope, this nebula, also known as NGC 2359, looks like a helmet with wings.

Thor’s Helmet completes this week’s trio of objects that lie in Canis Major. It sits 8.8° east-northeast of Sirius. This celestial treat is a cosmic bubble sculpted by radiation from a type of luminous, massive star called a Wolf-Rayet star.

Editor's note: Al Kelly submitted the image of Thor's Helmet above to Astronomy.com's Online Reader Gallery.

French astronomers Charles Joseph Étienne Wolf and Georges Antoine Pons Rayet discovered this stellar type spectroscopically in 1867. These short-lived supergiant stars are rare; astronomers have discovered fewer than 250 of them within the Milky Way.

To enhance NGC 2359’s visual appearance, use a nebula filter such as an OIII. Through a 12-inch telescope, you’ll see the circular central area and the helmet’s two “wings.” The brightest part measures 1' wide and extends to the south approximately 4'.

Recently, I observed Thor’s Helmet through a 30-inch telescope. The intricate details I thought visible only in photographs amazed me. If you have the opportunity to observe NGC 2359 through a large scope, take it. You won’t be disappointed.

--End transcript--

Previous episode: Canis Minor, M78, and the Witch Head Nebula
Previous transcript