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Astronomy Picture of the Day 10-06-04
NASA ^ | 10-06-04 | Robert Nemiroff and Jerry Bonnell

Posted on 10/06/2004 3:38:43 AM PDT by petuniasevan

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2004 October 6
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

N11: A Giant Ring of Emission Nebulas
Credit & Copyright: C. Smith & S. Points, CTIO, AURA, NOAO, NSF

Explanation: How did this unusually large nebula form? One of the largest nebulas yet detected is actually a complex ring of emission nebulas connected by glowing filaments. The unusual network, known as N11, spans over 1000 light years and is a prominent structure of the Large Magellanic Cloud, the largest satellite galaxy of our Milky Way Galaxy. In the center of the above image is open star cluster LH9, also known as NGC 1760, composed of about 50 bright blue stars that emit radiation that has eroded a whole in their surroundings. A leading hypothesis for the formation of N11 is shells of successive generations of stars being formed further out from the center. The bright region just above center is N11B, an explosive domain where stars are being formed even today.


TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: nebula
Frequent starbursts sterilize center of Milky Way
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
Posted: October 5, 2004

Life near the center of our galaxy never had a chance. Every 20 million years on average, gas pours into the galactic center and slams together, creating millions of new stars. The more massive stars soon go supernova, exploding violently and blasting the surrounding space with enough energy to sterilize it completely. This scenario is detailed by astronomer Antony Stark (Harvard-Smithsonian Center for Astrophysics) and colleagues in the October 10, 2004, issue of The Astrophysical Journal Letters.


Say goodbye to the neighborhood! On this hypothetical world near the center of the Milky Way, the planet's sun paints the sky purple as descends toward the horizon at left. However, the bright supernova exploding at upper right lends an ominous feeling because its radiation is about to wipe out the alien life on this world. The galactic center is so dense with bright, hot stars that several can be seen through the cloudy twilight sky. Credit: David A. Aguilar, CfA
 
The team's discovery was made possible using the unique capabilities of the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). It is the only observatory in the world able to make large-scale maps of the sky at submillimeter wavelengths.

The gas for each starburst comes from a ring of material located about 500 light-years from the center of our galaxy. Gas collects there under the influence of the galactic bar-a stretched oval of stars 6,000 light-years long rotating in the middle of the Milky Way. Tidal forces and interactions with this bar cause the ring of gas to build up to higher and higher densities until it reaches a critical density or "tipping point." At that point, the gas collapses down into the galactic center and smashes together, fueling a huge burst of star formation.

"A starburst is star formation gone wild," says Stark.

Astronomers see starbursts in many galaxies, most often colliding galaxies where lots of gas crashes together. But starbursts can happen in isolated galaxies too, including our own galaxy, the Milky Way.

The next starburst in the Milky Way is coming relatively soon, predicts Stark. "It likely will happen within the next 10 million years."

That assessment is based on the team's measurements showing that the gas density in the ring is nearing the critical density. Once that threshold is crossed, the ring will collapse and a starburst will blaze forth on an unimaginably huge scale.

Some 30 million solar masses of matter will flood inward, overwhelming the 3 million solar mass black hole at the galactic center. The black hole, massive as it is, will be unable to consume most of the gas.

"It would be like trying to fill a dog dish with a firehose," says Stark. Instead, most of the gas will form millions of new stars.

The more massive stars will burn their fuel quickly, exhausting it in only a few million years. Then, they will explode as supernovae and irradiate the surrounding space. With so many stars packed so close together as a result of the starburst, the entire galactic center will be impacted dramatically enough to kill any life on an Earth-like planet. Fortunately, the Earth itself lies about 25,000 light-years away, far enough that we are not in danger.

The facility used to make this discovery, AST/RO, is a 1.7-meter-diameter telescope that operates in one of the most challenging environments on the planet-the frigid desert of Antarctica. It is located at the National Science Foundation's Amundsen-Scott Station at the South Pole. The air at the South Pole is very dry and cold, so radiation that would be absorbed by water vapor at other sites can reach the ground and be detected.

"These observations have helped advance our understanding of star formation in the Milky Way," says Stark. "We hope to continue those advancements by collaborating with researchers who are working on the Spitzer Space Telescope's Legacy Science Program. AST/RO's complementary observations would uniquely contribute to that effort."

Stark's co-authors on the paper announcing this finding are Christopher L. Martin, Wilfred M. Walsh, Kecheng Xiao and Adair P. Lane (Harvard-Smithsonian Center for Astrophysics), and Christopher K. Walker (Steward Observatory).

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

1 posted on 10/06/2004 3:38:43 AM PDT by petuniasevan
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To: MozartLover; Joan912; NovemberCharlie; snowfox; Dawgsquat; Vigilantcitizen; theDentist; ...

YES! You too can be added to the APOD PING list! Just ask!

2 posted on 10/06/2004 3:40:35 AM PDT by petuniasevan (Keyboard: Device for entering mistakes into a computer.)
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To: petuniasevan

Thank you for posting this thread every day. I find it fascinating.


3 posted on 10/06/2004 3:43:15 AM PDT by Jemian (Annoy the French. Vote for Bush!)
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To: petuniasevan

Great nebula - thanks.


4 posted on 10/06/2004 3:48:40 AM PDT by Colosis (Just when you think you've won the rat race along come faster rats.)
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To: petuniasevan
I remember hearing comments when Star Trek first came out – people saying it could not look that pretty out there in empty space.
5 posted on 10/06/2004 3:49:41 AM PDT by R. Scott (Humanity i love you because when you're hard up you pawn your Intelligence to buy a drink.)
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To: petuniasevan
composed of about 50 bright blue stars that emit radiation that has eroded a whole in their surroundings.

Eroded a whole what?
6 posted on 10/06/2004 4:18:02 AM PDT by aruanan
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To: petuniasevan

BTTT


7 posted on 10/06/2004 4:44:09 AM PDT by GodBlessRonaldReagan (Count Petofi will not be denied!)
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To: petuniasevan

That's beautiful!


8 posted on 10/06/2004 6:34:30 AM PDT by foolish-one
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To: petuniasevan

Beautiful! Thank you for the ping.


9 posted on 10/06/2004 8:32:57 AM PDT by tuliptree76 ("A word aptly spoken is like apples of gold in settings of silver." - Proverbs 25:11)
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To: petuniasevan

Beautiful and amazing.


10 posted on 10/06/2004 11:56:02 AM PDT by Ernest_at_the_Beach (A Proud member of Free Republic ~~The New Face of the Fourth Estate since 1996.)
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To: petuniasevan

Thanks for the ping.


11 posted on 10/06/2004 12:57:50 PM PDT by sistergoldenhair
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To: All

My computer decided to wait until poorman was off visiting his parents 2 states away to malfunction. Grrrrr....

I will be trying to reload Windows and see if that solves the problem; if not, there will be no APOD for a few days.

And of course my APOD Ping List is on that computer. Hopefully I will be able to retrieve all my files.


12 posted on 10/06/2004 5:46:26 PM PDT by petuniasevan (Keyboard: Device for entering mistakes into a computer.)
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To: petuniasevan

Thank you. Absolutely gorgeous!


13 posted on 10/11/2004 9:47:54 PM PDT by Soaring Feather (~Poetry is my forte.~)
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