A comparison of Kepler's latest planetary finds. (Graphic Credit: NASA).
The Kepler space telescope may have bagged an unexpected prize during its hunt for exo-planets. Along with five published exoplanets illustrated above, Kepler snared two potentially bizarre objects. Dubbed KOI (Kepler Objects of Interest) -81 and 74, these companions actually appear dimmer passing behind the parent star rather than in front of it. This suggests a bright luminous object(s) with an Earth-like diameter but much more massive… a white dwarf? Possibly, but the objects seem to be physically too large to fit this class of objects. White dwarfs have an upper limit of about 1.4 solar masses, also known famously as the Chandrasekhar limit. Recently, scientist Jason Rowe of NASA Ames research center has been able to directly measure the masses of these companions by measuring the way the companions physically warp, or distort the bodies of their primary companions. The result; these stars are in the realm of 0.1 solar masses, which would make them some the lightest white dwarfs known. Obviously, this also becomes a problem because although small and luminous, KOI-81 and -74 probably aren’t supported solely by electron degeneracy pressure that characterizes standard classical white dwarfs. The situation just got stranger and stranger… were these objects large super-heated planets or light white dwarfs?
Enter an international team of astronomers meeting at Kavli Institute in Peking (Beijing) China. Using an innovative technique known as Doppler boosting, they were able to pinpoint the mystery objects mass at 0.2 solar masses, on the low end but still in the realm of a white dwarf. This makes even more sense if one considers a white dwarf accreting mass from a primary companion, ala a Type 1A supernovae candidate…(hey, didn’t we write in this space last week about the lack of these beasties?) Doppler boosting works in terms of catching subtle fluctuations in the brightening of an approaching object as measured by photons received over a given unit of time and dimming as it recedes…altogether a complicated affair, considering this must be untangled from a flurry of other signals. This unexpected find illustrates that surreptitious discoveries are often the norm in astronomy, if only someone is willing to look for them!
20.06.10: The Low Down on WASP-12b.
An Artist's Impression...NOT a Hubble photograph! (Credit: NASA/ESA/G. Bacon).
A bizarre exo-world just got stranger in the past month, but not in the way many news outlets would have you believe. WASP-12b is destined for a short life, one that we many have been fortunate enough to catch it in the middle of. The story starts in 2008, with the transiting exoplanet’s discovery by the UKs Wide Area Search for Planets (WASP) array. The primary star, WASP-12, is a yellow dwarf located 600 light years distant in the constellation Auriga. Even at that time, it was known that WASP-12b was strange; it whizzed around its star in only 26 hours and had to be sizzling. Now, follow-up measurements with the Hubble Space Telescope and its newly installed Cosmic Origins Spectrograph have indeed revealed a world in peril; at 2800° degrees Fahrenheit, WASP-12b is bloated up to three times the radius of Jupiter, although it only contains 1.4 times its mass. COS was able to identify manganese, tin, and aluminum in the spectra of the atmosphere as the planet transited its host star, using its sensitivity in the ultraviolet to pin down key measurements such as its diameter. This would put the Roche Limit of the planet well beyond what its own gravity can retain. WASP-12b is more than likely feeding material to its stellar host, an act it can’t maintain forever. Calculations show that WASP-12b will cease to exist in about 10 million years or so. It does, however, give astronomers an opportunity to gather a spectrum for study of a hot Jupiter in action… The WASP-12b story also fueled an avalanche of bad science stories, along the lines of “Cannibal Star 600 Million Light Years Distant Consumes Planet!” as if such a star bent on evil were inbound or headed our way. Never let the facts get in the way of a good story, guys… you keep us science news bloggers employed!