Astronomy.com blog : comets

Comets provide ideal conditions for bacteria, life

Bill Andrews — Tue, 18 Aug 2009 21:49:00 GMT

Aliens and science don’t usually go together. Maybe it’s the, let’s say, “disheveled” look of the overly eager UFO enthusiasts and abductees. Both professional and amateur astronomers alike are quick to distance themselves from talk of UFOs. But that is a far cry from saying there is no alien life. While there remains no solid proof of extraterrestrial life, more and more discoveries do seem to hint that it exists.

A July paper in the International Journal of Astrobiology claims that liquid water in comets, once thought virtually impossible, is in fact almost a certainty. The authors used the latest discoveries of comets’ interiors to calculate that many comets would give off radioactive heat, causing the frozen ice commonly found in comets to melt into liquid water.

More significantly, the authors argue these potential lakes and oceans, together with the organic materials we already knew existed in comets, would have provided ideal conditions for primitive bacteria to thrive. Bam! Likely extraterrestrial life, right there in a respected journal. And that’s not all.

NASA announced just this week it found the amino acid glycine, one of the essential building blocks of life, in samples of a comet. The Stardust spacecraft, built specifically to help scientists analyze comets and their makeup, brought samples of Comet Wild 2 back to Earth. The Stardust principal investigator himself called the glycine discovery an exciting and profound result, and I have to agree. While it’s still a far cry from proof of extraterrestrial life, it’s one more bit of evidence supporting the idea.

We might be quick to pick apart any notion of potential alien life, and that’s fine — it’s the role of science to doubt and question, after all. But we should also remember that extraterrestrial life remains a distinct possibility, with no evidence against it. Just because scientists and aliens don’t normally mix, doesn’t mean it always will be so.

Do you think aliens are a big joke? Or do you think that if it is just us, it seems like an awful waste of space?

Photo credit: NASA/JPL

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.

Comet Lulin in motion

Michael Bakich — Tue, 28 Apr 2009 14:12:00 GMT

Here’s another great example of material I receive as Photo Editor of Astronomy. Astroimager Robert Lockwood from San Diego created an animation he did of Comet C/2007 N3 (Lulin).

For the final animation, Robert combined 75 exposures — 25 each through red, green, and blue filters. Each exposure lasted 45 seconds. He also allowed an additional 30 seconds to elapse between sets of three.

The telescope Robert used was a 7.2-inch Takahashi Epsilon-180 hyperbolic astrograph at f/2.8. His camera was a Santa Barbara Instrument Group ST-10XME, and he used Astrodon E-Series filters.

The final result shows the comet traveling against the background stars for 2 hours, 35 minutes. Nice going, Robert!

See more Comet Lulin images in our Online Reader Gallery.

Watch Comet Lulin fly

Michael Bakich — Wed, 11 Mar 2009 15:58:00 GMT

As Photo Editor of Astronomy, I see some great stuff. I just received an e-mail from astroimager Tom Carrico. He shared with us an animation he did of Comet C/2007 N3 (Lulin). You’ll find Carrico’s creation in our videos section, “Watch Comet Lulin fly.”

Tom operates ARGO Observatory, which is located in central Oregon about 25 miles east of Bend. He imaged Comet Lulin from his observatory at New Mexico Skies February 21 through a 4-inch Takahashi FSQ-106 apochromatic refractor with an SBIG STL-11000 CCD camera. He took 61 one-minute images over a 2-hour period and combined them into an animated .gif file.

Along with the comet, you’ll also notice many streaks throughout the animation. Those are geosynchronous satellites whose movement Tom’s 1-minute exposures captured.

Although he downsized the original images to one-quarter their original sizes, the animation still weighed in at 29 megabytes!

More Comet Lulin coverage:

Comet Lulin images
News article: Have you seen Comet Lulin?
News article: Swift spies Comet Lulin
News article: Green comet approaches Earth

You, too, can photograph Comet Lulin

Michael Bakich — Fri, 27 Feb 2009 19:30:00 GMT

I just received an e-mail from Ohio amateur astronomer and longtime contributor to the magazine John Chumack. In it, he included a tutorial on how to photograph Comet Lulin. I wanted to share it with you all. And remember, if you have success, be sure to submit your photo to our Online Reader Gallery.

“How to Capture Comet Lulin”
by John Chumack
You can capture the comet with either a film single-lens reflex (SLR) camera or a digital SLR camera and camera lens, too, but if you just want to see the comet visually, skip to the link below. For a recent image, I used a Canon Rebel XSi digital SLR with a Canon 75–300mm lens set to 280mm. I set the focal length at f/5.6 and the ISO at 400. I took four 4-minute exposures and combined (stacked) them to make, essentially, a 16-minute image.

If you don’t have a 280mm lens, don’t worry. I captured Comet Lulin with 50mm and 70mm lenses as well. The comet is large, so it even looks good through a “normal” lens.
For my images, I use a tracking (motor-driven) telescope mount. Again, if you don’t have a tracking mount, use the basic “camera on a tripod” method. Shoot the comet from a dark site away from city lights for best results. Make sure your camera is mounted solidly on the tripod.

Set your camera to “bulb” or “manual,” and set the film or DSLR speed to ISO 800 or ISO 1600. Set the lens’ f-stop to f/4 or lower. Focus the lens to infinity, or simply focus on a bright star. If you are using an autofocus lens, turn the “Auto Focus” setting off. Auto focus will not work properly with night sky shots anyway. That’s why it’s best to focus manually on a bright star. Once you have focused, don’t touch the lens. Carefully point the camera toward the comet.

Don’t know where the comet is? You’ll find an interactive chart at Astronomy.com's StarDome.

Use a cable release or a self-timer to start the exposure. Avoid touching the camera. Vibrations will blur the image. Now take ten 30-second exposures of the comet. If you get star trails (stars that look like lines), lower each exposure time to 20 seconds and take 15 shots instead.

Film users develop and scan your negatives. DSLR users can just transfer the images to your computer. Next, find and use free image-stacking software like Deep Sky Stacker, Nebulosity, or Registax (Google them) to create your own 5-minute exposure.

Stack all of the images using the stars as your reference point. If the stars appear too faint, use the comet’s nucleus instead. Once you combine the exposures into one image, you can do the final level and color adjustments in your favorite image-processing program.

Congratulations! You have just captured a piece of astronomical history — a once-in-a-lifetime view of Comet Lulin that you can share with friends and family members.

More Comet Lulin coverage:

Read Astronomy magazine Senior Editor Rich Talcott's blog, Spot and follow the year's brightest comet with Astronomy.com, to find out how you can locate Comet Lulin in your sky tonight with Astronomy.com's StarDome.

Read about longtime astroimager John Chumack's observations of Comet Lulin and watch the Comet Lulin video he captured.

News article: Have you seen Comet Lulin?

News article: Swift spies Comet Lulin

News article: Green comet approaches Earth

Submit your images of Comet Lulin to Astronomy.com's Online Reader Gallery

John Chumack captures Lulin

Karri Ferron — Wed, 25 Feb 2009 17:51:00 GMT

Astronomy magazine contributor and longtime imager John Chumack had some luck spotting Comet Lulin February 20/21, and he was nice enough to share his account with us:

I took a chance last Friday night and went out to my observatories in Yellow Springs, Ohio, even though there were some high cirrus clouds floating around. It finally cleared enough around 11:30 p.m., just about the time for Comet Lulin to clear the trees east of the compound.

I was worried because the seeing/transparency really was poor, and with the threat of snow storms on the way, I needed to try to capture the comet during this New Moon time frame.

The sky remained fairly clear, with occasional light cirrus clouds floating around. Comet Lulin is just barely visible to the naked eye from a suburban location. It looks a lot better through binoculars, and the dust tail is visible. Easy in a 4-inch diameter telescope!

The comet is moving rapidly, so movement is easily detectable after only 1 minute.

I captured a shot of Comet Lulin with my 5-inch diameter reflector and Canon Rebel Xsi, ISO 400, for 93 minutes, 33 subs, 20 at 4 minutes, and 13 at 1 minute, to help prevent over-exposure of the nucleus.

I tracked Comet Lulin’s nucleus, to show the finer details in the dust tail(left) and anti-tail. The comet is traveling from left to right(east to west) in this image.

I also shot a short movie following the comet’s movement over 90 minutes. The video shows what Lulin looks like through binoculars. Hopefully other readers will get clear skies to view this bright comet.

Watch John’s video of Comet Lulin.

More Comet Lulin coverage:

News article: Have you seen Comet Lulin?

News article: Swift spies Comet Lulin

News article: Green comet approaches Earth

Submit your images of Comet Lulin to Astronomy.com's Online Reader Gallery

Spot and follow the year’s brightest comet with Astronomy.com

Rich Talcott — Wed, 11 Feb 2009 19:09:00 GMT

Comet C/2007 N3 (Lulin) remains on track to be the brightest comet of the year. It should peak around 5th magnitude during the second half of February, when it will slide past Spica, Saturn, and Regulus. To track the comet from your location as it crosses the night sky, check out Astronomy.com's interactive star chart — StarDome.

To find and track Comet Lulin with StarDome:

On the lower right of the dome display, under "Options," click the Display... pull-down menu.
Select Comets from the Display... pull-down menu and make sure a check mark appears next to Comets
Click the Show names... pull-down menu
Select Comets from the Show names... pull-down menu
Under "Date and Time Settings," highlight the hour, and click the UP arrow repeatedly. Depending on your location, you should see "C/2007 N3 (Lulin)" written in a teal-colored font, enter the dome display at about 23:00 local time.
Adjust the dates to watch Lulin's path across the sky throughout the month.
To see Lulin in relation to Spica, Saturn, and Regulus, be sure Planets and Bright Stars are selected under the Show names... pull-down menu.

David H. Levy to join Astronomy magazine as Contributing Editor

David Eicher — Mon, 29 Dec 2008 19:47:00 GMT

In January 2009 world-renowned amateur astronomer and comet discoverer David H. Levy joins Astronomy magazine as a Contributing Editor. Levy will write a monthly column for the world’s most popular magazine on astronomy, which has a circulation of more than 125,000 monthly issues. Levy’s first column will appear in the June 2009 issue.

Levy is most famous for discovering 22 comets over his long career, including the co-discovery of Comet Shoemaker-Levy 9, which broke apart and slammed into Jupiter in 1994. He is the author or editor of 35 books and products, has served as Science Editor for Parade magazine, and has written for most of the popular astronomy magazines in existence, including Sky & Telescope and Deep Sky.

Levy also won an Emmy for his 1998 participation on the writing team for the Discovery Channel documentary Three Minutes to Impact.

Anyone who has been around for a long time as an amateur astronomer knows how entertaining Levy is as a speaker. He has given more than 1,000 lectures and popular astronomy talks and has appeared on a wide variety of television programs to promote astronomy, including The Today Show, ABC’s World News Tonight, Good Morning America, and other shows. Levy is the recipient of five honorary degrees from various institutions.

He lives with his wife Wendee in Vail, Arizona, where they operate the Jarnac Observatory, surveying the sky for comets and promoting astronomical education.

Astronomy magazine editors are especially proud to add Levy to a distinguished group of popular columnists that includes Bob Berman, Glenn Chaple, Phil Harrington, and Stephen James O’Meara.

(photo) David H. Levy with Obadiah, his largest automated telescope (credit: Wendee Levy)

Ho, ho, ho for Halley’s Comet

Daniel Pendick — Thu, 25 Dec 2008 01:00:00 GMT

On Christmas Day, 1758, a German amateur astronomer and farmer named Johann Georg Palitzsch did something that would have made a great Christmas gift for English astronomer Edmond Halley. Johann “recovered” Halley’s Comet, meaning he was the first to observe this previously observed “dirty snowball” as it returned to the inner solar system.

Edmond Halley (1656-1742) calculated the orbit of the comet that now bears his name based on previous sightings. He determined that the same comet was responsible for several sightings spaced about 75 years apart.

By Halley’s reckoning, the comet would reappear in 1758 — that’s 250 years ago this Christmas. Unfortunately, he didn’t live to see his prediction proved correct.

For the complete and detailed scoop on the recovery of Halley’s Comet, read this treasure-trove of information and images by master comet observer Gary W. Kronk, author of the Cometography book series.