LONDON, Aug. 16 (Xinhua) -- Astronomers have discovered a glowing, comet-like tail trailing behind a double star called Mira,a phenomenon never seen before.

    US astronomers have discovered the long tail, which is visible only in far ultraviolet light, according to a report on the science magazine Nature on Thursday.

    The astronomers led by Christopher Martin of Caltech in Pasadena, California, US happened upon it using NASA's Galaxy Evolution Explorer satellite, which was surveying the sky at ultraviolet wavelengths, the report said.

    The tail extends 13 light years from Mira, which meaning "wonderful" in Latin is one of the best-studied star systems in the sky and lies 350 light years from Earth. It appears to trace the path of Mira's motion across the sky over the past 30,000 years, based on its size and Mira's speed, which has been previously measured.

    One star in the pair, called Mira A, is a bloated, aging red giant that sheds large amounts of gas and dust into space, while the other, Mira B, is a dense stellar corpse called a white dwarf.

    The team believes the tail is created as a result of Mira A's stellar wind, an outflow of gas and dust from the star, which hits ambient gas as it moves through space.

    Fast-moving electrons generated by the collision then strike hydrogen molecules in surrounding gas, producing ultraviolet light, thus creating a glowing trail behind Mira as it travels through the galaxy at 130 kilometers per second.

    "This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved. We never would have predicted a turbulent wake behind a star that glows only with ultraviolet light," team member Mark Seibert from the Carnegie Observatories in Pasadena, US was quoted as saying.

    According to the team, the trail could provide a "fossil history" of how Mira shed mass over thousands of years.

    Previous studies had shown that some of the material from Mira A's wind has collected into a disc -- which could potentially form planets -- around Mira B.

    As they age, the cores of some massive stars eventually become unstable, triggering runaway nuclear reactions that tear them apart in supernovae.

    But stars such as Mira A, which start out with a few times the mass of the Sun, avoid this fate by shedding most of their mass in stellar winds to become placid white dwarfs.