News from Japanese Astronomy
Validating the Planetary Formation Model
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, Japanese astronomers have spotted strong evidence of a massive planet-forming disk around a young star known as HD 142527. HD 142527 lies in the constellation Lupus at a distance of about 457 light-years from Earth. The astronomers have used ALMA to detect the submillimeter emission from the emission from the dust ring around this baby star. The emission has a non-uniform distribution and the northern side is 30 times brighter than the faint southern side, according to the team.
Recent near-infrared observations with the NAOJ Subaru Telescope revealed that protoplanetary disks have structures that are far more complex than astronomers expected. Spiral or gap structures are thought to be associated with hidden planets in the disk.
However, it is impossible to measure the amount of dust and gas in the densest part of the disk by near-infrared observations. Since near-infrared light is easily absorbed or scattered by a large amount of dust, it isn’t suitable for observing the innermost part of the dense region of the disk. Then, the key to the solution will be millimeter and submillimeter wave.
The new image of HD 142527, which was taken with ALMA, shows that cosmic dust is circling around the star in a form of asymmetric ring.
By measuring the density of dust in the densest part of the ring, the astronomers found that it is highly possible that Jupiter-like giant gaseous exoplanets or Earth-like rocky planets are now being formed in that region. This region is far from the central star, about 5 times larger than the distance between the Sun and the Neptune.
“We are very surprised at the brightness of the northern side,” said Dr Misato Fukagawa of Osaka University, who is the lead author of the paper appearing in the Publications of the Astronomical Society of Japan (full paper in .pdf / arXiv.org version).
“The brightest part in submillimeter wave is located far from the central star, and the distance is comparable to five times the distance between the Sun and the Neptune. I have never seen such a bright knot in such a distant position.”