Samstag, 21. Februar 2015 - 11:13 Uhr
The photo at the bottom is the most detailed picture to date of a large, edge-on, gas-and-dust disk encircling the 20-million-year-old star Beta Pictoris. The new visible-light Hubble image traces the disk in closer to the star to within about 650 million miles of the star (which is inside the radius of Saturn's orbit about the sun).
Owed to its long-duration mission, Hubble can spot short-duration changes in celestial objects, revealing unprecedented detail in an otherwise ‘unchanging’ sky. Take Beta Pictoris for example. This 20 million year-old star sports an extensive edge-on protoplanetary disk and Hubble has been watching motion in this dust, stirred up by the presence of a massive exoplanet.
This is yet another cosmic first for the veteran space telescope; astronomers have been able to compare Hubble observations of Beta Pictoris 1997 and 2012 and would therefore be able to track any morphological changes in its protoplanetary disk.
As the exoplanet’s orbit is predicted to have an orbital period of between 18-20 years, over the 15 years between observations, the exoplanet would have shifted considerably, but Hubble has noticed little change in the distribution of dust in the protoplanetary disk, confirming some models about how protoplanetary disks mingling with exoplanets work.
“Some computer simulations predicted a complicated structure for the inner disk due to the gravitational pull by the short-period giant planet,” said Daniel Apai of the University of Arizona. “The new images reveal the inner disk and confirm the predicted structures. This finding validates models, which will help us to deduce the presence of other exoplanets in other disks.”
From these observations, astronomers can see that the circumstellar dust is orbiting in unison with the exoplanet “like a carousel,” according to a Hubble news release. This suggests that the inner dusty disk is “smooth and continuous” as it orbits the star.
Beta Pictoris, however, isn’t believed to be a ‘typical’ young star with a protoplanetary disk.
“The Beta Pictoris disk is the prototype for circumstellar debris systems, but it may not be a good archetype,” said co-author Glenn Schneider of the University of Arizona.
Beta Pictoris was the first star to be discovered to have a bright circumstellar disk. It’s believed that asteroids and comets in the system are continuously colliding, populating the disk with copious quantities of dust. Also, a lobe-like feature in the disk is thought to be the dusty remains of a pulverized Mars-sized body.
Located only 63 light-years from Earth, Beta Pictoris is the closest circumstellar disk system, so it is a protoplanetary Petri-dish of sorts, providing astronomers with a smorgasbord of planetary phenomena.
Interestingly, the researchers suggest that by studying star systems with circumstellar disks known also to contain exoplanets, we may begin to fathom the ‘fingerprint’ in these disks so previously hidden exoplanets may be revealed around other stars.