A Red Giant Named Mira
NASA’s Galaxy Evolution Explorer has observed a red giant star named Mira, Latin for “wonderful”, hurtling through space at 291,000 miles per hour, and shedding material which forms a tail 13 light-years long, or 20,000 times the distance from Pluto to the sun. The material being shed has been released over the past 30,000 years, but has never been seen before. The tail has been likened to the contrail of a jet or the wake of a speeding boat, and is made up of carbon, oxygen, and other building blocks of new stars, planets, and, perhaps, life as well.
Although the red giant has been popular with astronomers for about four centuries, it was only with the help of the Galaxy Evolution Explorer that the phenomenal tail has been discovered. The space telescope was scanning the entire sky in ultraviolet light during an ongoing survey when what appeared to be a comet with an enormous tail was noticed by surprised astronomers. The discovery of Mira’s tail offers an unprecedented opportunity to study the death of stars like our own sun, and how they can initiate the development of new solar systems.
Mira was once, billions of years ago, a star like our sun. Eventually it began to increase in size, becoming a variable red giant, expanding and contracting, and occasionally becoming bright enough to see with the unaided eye. In time the star will rid itself of all remaining gas, creating a planetary nebula, and, after the nebula fades, the burned out core of the star will become a white dwarf.
The speed at which Mira is traveling through space is greater than other stars of the same type, perhaps due to the gravitational effects of passing stars. A distant companion, Mira B, is keeping pace with Mira, (also known as Mira A), and is thought to be a white dwarf. Mira A and Mira B are located in the Cetus constellation, 350 light-years from Earth, slowly orbiting around each other.
Also observed by the Galaxy Evolution Explorer was a build-up of hot gas, known as a bow shock, ahead of Mira, along with two streams of gas blowing out of the front and back of the star. It is thought that hot gas from the bow shock is heating the gas blowing off the star, making it fluoresce with ultraviolet light. Since the star’s tail only shines in ultraviolet light, the Galaxy Evolution Explorer, being very sensitive to ultraviolet light, was able to observe it while other telescopes could not, possibly explaining why the tail has not been seen before.
This entry was posted on Monday, August 13th, 2007 at 9:12 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
