A disc of planet-forming dust around a distant star has disappeared unexpectedly, leaving astronomers scratching their heads and questioning current theories of how planets are formed. "It's like the classic magician's trick: Now you see it, now you don't," said astronomer Carl Melis of UC San Diego, who led the team that discovered the phenomenon. "Only in this case, we're talking about enough dust to fill an inner solar system and it is really gone." The team has proposed several possible explanations for the disappearance, but "none are really compelling," Melis said.
The star in question is a called TYC 8241 2652. It is a younger version of our own sun, only about 10 million years old (our own solar system is 4.5 billion years old), and lies 450 million light-years away in the constellation Centaurus. It was first seen in 1983 by NASA's Infrared Astronomical Satellite (IRAS). The dust disc heats up from absorbed light from its star and re-emits the energy in the infrared, giving the system a characteristic appearance. IRAS has discovered hundreds of such stars.
The team reported Thursday in the journal Nature that they reexamined the star in 2008 using the Gemini South Observatory in Chile and found the same infrared signature observed in 1983. But when they looked at it again in 2009 with NASA's orbiting Wide-field Infrared Survey Explorer, about two-thirds of the dust had disappeared. Observations with other telescopes the following year showed that virtually all of the dust was gone. "It's as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared," said co-author Ben Zuckerman of UCLA.