ESO ALMA discovers a formation site of a giant planetary system

Dust and gas disk around HD142527. 

The dust and gas distributions observed by ALMA are shown in red and green, respectively. 

Near-infrared image taken by the NAOJ Subaru Telescope is shown in blue. 

The image clearly shows that the dust is concentrated in the northern (upper) part of the disk. 

The circle in the image show the position of the dust concentration, in which planets are thought to be formed.

A team of Japanese astronomers has obtained a firm evidence of formatino of a giant planetary system around a young star by the observations with the Atacama Large Millimeter/submillimeter Array (ALMA).

This result has a transformative impact on the theories of planet formation and gives us a clue to the origin of a wide variety of planetary systems.

The research team, led by astronomers at Osaka University and Ibaraki University, observed a young star named HD142527 in the constellation Lupus (the Wolf) with ALMA.

The ALMA image shows that cosmic dust, which is component material of planets, 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 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.

This is the first firm evidence of planet formation found so far from the central star in a protoplanetary disk. The research team plans further observations of HD142527 with ALMA for closer investigation, as well as other protoplanetary disks to have a comprehensive understanding of the planet formation in general.

Research Background
More than 1000 extrasolar planets have been discovered until now, and it is widely recognized that the Sun is not the only star which has planets.

In the research of extrasolar planets, astronomers have found a wide variety of planets such as Jupiter-like gaseous giant planets circling around central stars in a much smaller orbit than that of the Mercury, and planets that have a very large orbit far beyond the Neptune's orbit.

While such a diverse range of extrasolar planets have been discovered, the formation process of planets is yet to be well understood.

This is one of the top priority issues in modern astronomy and an increasing number of observations have been conducted to explore the planet forming region around young stars.

A baby star is surrounded by a ring of dust and gas, which would be the component material of planets.

Recent near-infrared observations with the NAOJ Subaru Telescope revealed that protoplanetary disks have structures that are far more complex than we 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 of the solution will be millimeter and submillimeter wave, which can be observed with ALMA.

Millimeter/submillimeter wave has longer wavelength than near-infrared light and is poorly absorbed by dust, which enables astronomers to peer into the inner part of the disk.

Low spatial resolution was a weak point in millimeter/submillimeter observatins, but it is now greatly improved by ALMA.

More information: The research findings are presented in the article Fukagawa et al. "Local Enhancement of Surface Density in the Protoplanetary Ring Surrounding HD 142527" published in the Publications of the Astronomical Society of Japan, on December 25th, 2013.