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| Mira! (click to enlarge) |
NASA got a new view of a (supposedly) well-known star, "Mira", and found that it has a tail - and I mean a mindblowingly massive tail with almost magical properties about which someone will surely write a children's book.
"Mira appears as a small white dot in the bulb-shaped structure at right, and is moving from left to right in this view. The shed material can be seen in light blue. The dots in the picture are stars and distant galaxies. The large blue dot at left is a star that is closer to us than Mira.
I'm going to let NASA explain it, as it would only lose in translation through me...
From NASA Science News for August 15, 2007:
A Star with a Comet's Tail
"Astronomers have discovered something they've never seen before: a star with a tail like a comet. Even more amazing is the fact that the new-found tail is attached to one of the most popular stars in the sky, a red giant named Mira. Amateur and professional astronomers have been watching Mira for 400 years and only recently has a NASA space telescope spotted its massive tail."
FULL STORY: August 15, 2007:
"Astronomers using a NASA space telescope, the Galaxy Evolution Explorer, have spotted an amazingly long comet-like tail behind a star streaking through space. The star, named Mira after the Latin word for "wonderful," has been a favorite of astronomers for about 400 years, yet this is the first time the tail has been seen.
"Galaxy Evolution Explorer--"GALEX" for short--scanned the popular star during its ongoing survey of the entire sky in ultraviolet light. Astronomers then noticed what looked like a comet with a gargantuan tail. In fact, material blowing off Mira is forming a wake 13 light-years long, or about 20,000 times the average distance of Pluto from the sun. Nothing like this has ever been seen before around a star.
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| Click to see NASA's animated version |
"'I was shocked when I first saw this completely unexpected, humongous tail trailing behind a well-known star,' says Christopher Martin of the California Institute of Technology. 'It was amazing how Mira's tail echoed on vast, interstellar scales the familiar phenomena of a jet's contrail or a speedboat's turbulent wake.' Martin is the principal investigator for the Galaxy Evolution Explorer, and lead author of a Nature paper appearing today to announce the discovery.
"Astronomers say Mira's tail offers a unique opportunity to study how stars like our sun die and ultimately seed new solar systems. Mira is an older star called a red giant that is losing massive amounts of surface material. As Mira hurtles along, its tail sheds carbon, oxygen and other important elements needed for new stars, planets, and possibly even life to form. This tail material, visible now for the first time, has been released over the past 30,000 years.
"'This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved,' says co-author Mark Seibert of the Observatories of the Carnegie Institution of Washington in Pasadena. 'We hope to be able to read Mira's tail like a ticker tape to learn about the star's life.'
"Billions of years ago, Mira was similar to our sun. Over time, it began to swell into what's called a variable red giant - a pulsating, puffed-up star that periodically grows bright enough to see with the naked eye. Mira will eventually eject all of its remaining gas into space, forming a colorful shell called a planetary nebula. The nebula will fade with time, leaving only the burnt-out core of the original star, which will then be called a white dwarf.
"Compared to other red giants, Mira is traveling unusually fast, possibly due to gravitational boosts from other passing stars over time. It now plows along at 130 kilometers per second, or 291,000 miles per hour. Racing along with Mira is a small, distant companion thought to be a white dwarf. The pair, also known as Mira A (the red giant) and Mira B (the white dwarf), orbit slowly around each other as they travel together through the constellation Cetus, 350 light-years from Earth.
"In addition to Mira's tail, GALEX also discovered a bow shock, a type of buildup of hot gas, in front of the star, and two sinuous streams of material coming out of the star's front and back.
Astronomers think hot gas in the bow shock is heating up the gas blowing off the star, causing it to fluoresce with ultraviolet light. This glowing material then swirls around behind the star, creating a turbulent, tail-like wake. The process is similar to a speeding boat leaving a choppy wake, or a steam train producing a trail of smoke.
"The fact that Mira's tail only glows with ultraviolet light might explain why other telescopes have missed it. GALEX is very sensitive to ultraviolet light and also has an extremely wide field of view, allowing it to scan the sky for unusual ultraviolet activity.
"'It's amazing to discover such a startlingly large and important feature of an object that has been known and studied for over 400 years,' says James D. Neill of Caltech. 'This is exactly the kind of surprise that comes from a survey mission like the Galaxy Evolution Explorer.'
More on Mira:
"A new ultraviolet mosaic* from NASA's Galaxy Evolution Explorer shows a speeding star that is leaving an enormous trail of "seeds" for new solar systems. The star, "Mira" (pronounced "my-rah"), after the Latin word for "wonderful," is shedding material that will be recycled into new stars, planets and possibly even life as it hurls through our galaxy.
"The Galaxy Evolution Explorer discovered Mira's strange comet-like tail during part of its routine survey of the entire sky at ultraviolet wavelengths.
"When astronomers first saw the picture, they were shocked because Mira has been studied for over 400 years yet nothing like this has ever been documented before.
"Mira's comet-like tail stretches a startling 13 light-years across the sky. For comparison, the nearest star to our sun, Proxima Centauri, is only about 4 light-years away.
"Mira's tail also tells a tale of its history – the material making it up has been slowly blown off over time, with the oldest material at the end of the tail having been released about 30,000 years ago.
"Mira is a highly evolved, "red giant" star near the end of its life. Technically, it is called an "asymptotic giant branch star". It is red in color and bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars.
"Our sun will mature into a red giant in about 5 billion years.
"Like other red giants, Mira will lose a large fraction of its mass in the form of gas and dust. In fact, Mira ejects the equivalent of the Earth's mass every 10 years. It has released enough material over the past 30,000 years to seed at least 3,000 Earth-sized planets or 9 Jupiter-sized ones.
"While most stars travel along together around the disk of our Milky Way, Mira is charging through it. Because Mira is not moving with the "pack," it is moving much faster relative to the ambient gas in our section of the Milky Way.
"Mira's breakneck speed together with its outflow of material are responsible for its unique glowing tail.
"Images from the Galaxy Evolution Explorer show a large build-up of gas, or bow shock, in front of the star, similar to water piling up in front of a speeding boat. Scientists now know that hot gas in this bow shock mixes with the cooler, hydrogen gas being shed from Mira, causing it to heat up as it swirls back into a turbulent wake. As the hydrogen gas loses energy, it fluoresces with ultraviolet light, which the Galaxy Evolution Explorer can detect.
"Mira, also known as Mira A, is not alone in its travels through space. It has a distant companion star called Mira B that is thought to be the burnt-out, dead core of a star, called a white dwarf. Mira A and B circle around each other slowly, making one orbit about every 500 years. Astronomers believe that Mira B has no effect on Mira's tail.
"Mira is also what's called a pulsating variable star; it dims and brightens by a factor of 1,500 every 332 days, and will become bright enough to see with the naked eye in mid-November 2007. Because it was the first variable star with a regular period ever discovered, other stars of this type are often referred to as "Miras."
"Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its "whale of a tail" can be found in the tail of the whale constellation.
"*This mosaic is made up of individual images taken by the far-ultraviolet detector on the Galaxy Evolution Explorer between November 18 and December 15, 2006."
Production Editor: Dr. Tony Phillips Credit: Science@NASA
Sources:
http://www.nasa.gov/mission_pages/galex/20070815/v.html
http://science.nasa.gov/headlines/y2007/15aug_mira.htm?list1031480
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