Dust and Planets around Nearby Stars
Over the past couple of decades it has become apparent that the circumstellar environments of many nearby stars are not empty, but actually contain matter ranging from micron-sized dust grains to gas giant planets, some more massive than Jupiter. The Planetary Systems Group (PSG) at the UKATC uses the dusty debris disks found around nearby main sequence stars to study how extrasolar planetary systems form and evolve. These dust disks are called debris disks because it is collisions between asteroids and comets in these systems which replenishes the dust we observe. The solar system has an analogous debris disk with two main components: the Asteroid Belt, located between Mars and Jupiter; and the Kuiper Belt, located outside the orbit of Neptune.
Some 300 stars are known to have such debris disks. The disks have been discovered by looking at the spectrum of far-infrared emission from the star, which includes an infrared excess component corresponding to the thermal re-radiation of starlight by the dust. Only a handful of these disks are close enough and bright enough for their thermal emission to be resolved and so far just six disks have been imaged. However, the rewards of mapping the dust emission are great, since this gives us direct evidence of the location of the asteroid/comet belts in these systems and these images have also shown that the disks are far from smooth and symmetrical. These disk structures are particularly exciting as they provide evidence that planetary systems are orbiting within the disks. These planets would otherwise be impossible to detect with current technology.
The work of the PSG covers all aspects of the identification, observation and theoretical interpretation of debris disks. The following links show you some highlights from our recent work:
Artists impression of the Fomalhaut system based on our 450 µm image of its dust disk (Holland et al. 2003)
Picture credit PPARC and David Hardy
- Identification: database of stars with disks
- Imaging: pictures obtained with sub-millimetre and mid-infrared cameras
- Statistics: e.g., disk decay timescale, incidence with spectral type
- Interpretation: e.g., models showing evidence of unseen planets
- Publications: publications available for downloading
The UK ATC was invited to exhibit some of this research at the Royal Society's prostigious Summer Exhibition 2004.