The comet like tail of the star Mira A is 13 light-years long, or about 20,000 times the average distance of Pluto from the Sun. The tail was discovered by NASA’s Galaxy Evolution Explorer (Galex), and the researchers say they’ve never come across anything like it before, according to BBC News.
It’s the ultraviolet imaging used by Galex which has revealed Mira’s unusual characteristics. As the tail only emits light in the ultraviolet part of the spectrum, this might explain why other telescopes have thus far been unable to see it, says Barry Madore, a co-author of the paper and senior research astronomer at the Carnegie Observatories. The phenomenon is described in a paper for in the journal Nature.
This is a new discovery for us, and we’re still in the middle of just understanding the physics involved in the processes we’re observing, says another of the scientists authoring the paper, Mark Seibert.
According those scientists, Mira’s tail consists of materials expelled from Mira over a period of 30,000 years. We’re hoping to be able to "read" the tail almost like a ticker-tape to learn more about the life of the star.
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. […]
In addition to Mira’s tail, the Galaxy Evolution Explorer 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.