The problem with exoplanets is that they are very difficult to spot. They’re small, distant and often obscured by their star’s light. It’s little wonder that few direct observations of exoplanets exist — they’re nothing more than tiny smudges in astronomical photographs. And that’s after all kinds of complex image processing tricks are applied to tease out the faint signal.
But now, the existence of the first exoplanet to be directly observed by the Hubble space telescope has come under close scrutiny.
The media explosion started in Nov. 2008 when Hubble and the Hawaiian Keck and Gemini telescopes jointly announced the direct observation of worlds orbiting other stars. The Hubble team produced the dazzling visible light “Eye of Sauron” Fomalhaut picture (above) — a spitting image of the “Lord of the Rings” baddie — and the Keck/Gemini infrared telescopes imaged an entire star system of exoplanets orbiting HR 8799. Awe and wonder ensued; we were looking directly at those fabled extra-solar planets for the first time!
But according to University of Toronto astronomer Ray Jayawardhana and his team, the Hubble discovery might not be all it seems.
Speaking at the Extreme Solar Systems II conference in Jackson Hole, Wyoming, earlier this month, Jayawardhana pointed to an oddity in Fomalhaut b’s orbit: it seems to haven take a misstep. For any exoplanet to deviate from its expected orbit is a big red flag, after all.
But according to astronomer Paul Kalas, of the University of California, Berkeley, and lead author of the 2008 Hubble study, it’s not Fomalhaut b that’s taken the misstep.
So, why the controversy? Well, before 2008, Kalas tracked an object in Fomalhaut’s dusty disk. Using a high-resolution channel on the Hubble’s Advanced Camera for Surveys, Kalas snapped the motion of the suspected exoplanet in 2004 and 2006. In 2008, his team’s work was published.
Unfortunately, that high-resolution channel failed when the camera was brought online in 2009 and so he used another instrument, the Space Telescope Imaging Spectrograph, to take the picture. The 2009 image showed a slight deviation from the predicted orbital path of Fomalhaut b.
According to Jayawardhana, this deviation may be the final proof that kicks Fomalhaut b’s existence into touch.
Fomalhaut b is considered an oddball in the exoplanet world due to its high reflectivity and non-detection by ground-based infrared observatories. At approximately the same size as Jupiter (but weighing in at 3-times that of Jupiter’s mass), Fomalhaut b may be surrounded by a dust cloud, or a system of rings (like Saturn) amplifying its brightness, according to Kalas. But why can’t infrared observatories see it if Hubble can image it in optical light? Well, it could be that the Fomalhaut system is cooler and older than predicted — therefore less infrared radiation is being generated than predicted.
And what of this new oddity; the misstep in its orbital trajectory? Kalas thinks that might have something to do with the change in instrument used to image Fomalhaut — it’s some observational artifact that will be corrected when he images the system again using Hubble’s Advanced Camera for Surveys (an instrument he has been granted time to use next summer).
These explanations have done little to sway Jayawardhana and is pushing to have Fomalhaut b removed from the Exoplanet.eu database.
So, does Fomalhaut b exist or not? We’ll have to wait for more Hubble observations before this exoplanet controversy is resolved. Such is life on the raggedy edge of science…
Images: Hubble image of Fomalhaut b (NASA/ESA). Artist’s impression of the dusty dusk surrounding Fomalhaut (ESA, NASA, and L. Calcada (ESO for STScI)).