Recent observations of the young star DG Tauri found that it has a smooth protoplanetary disk but has not yet formed planets, suggesting that it is on the verge of the planet formation process. The observations reveal unexpected dust grain growth patterns and provide new insights into the early stages of planet formation.

Astronomers have become very good at spotting signs of planet formation around stars. However, to fully grasp planet formation, the key is to study situations before the process has even begun.

But new detailed observations of the young star DG Tauri show that it has a smooth protoplanetary disk with no signs of planet formation. This successful failure to detect planet formation may indicate that DG Tauri is on the eve of planet formation.

Image of radio wave emission intensity from the disk surrounding DG Tauri as observed with ALMA. Rings have not yet formed in the disk, suggesting that it is in the pre-planar period. Source: ALMA (ESO/NAOJ/NRAO), S. Ohashi et al.

Protoplanetary disks and planetary growth

Planets form in a disk of gas and dust called a protoplanetary disk around a protostar (a young star still in the process of forming). Planets grow so slowly that their evolution cannot be observed, so astronomers need to observe many protostars at various stages of planet formation to build a theoretical understanding.

This time, an international research team led by Satoshi Ohashi of the National Astronomical Observatory of Japan (NAOJ) used the Atacama Large Millimeter/submillimeter Array (ALMA) to conduct high-resolution observations of the protoplanetary disk around DG Tauri, a relatively young protostar located 410 light-years away in the direction of Taurus. The team found that DG Tauri's protoplanetary disk is very smooth and lacks any rings that would indicate planet formation. This leads the team to believe that the DG Taurus system will begin to form planets in the future.

Unexpected findings and future research

The research team found that at this stage before planet formation, the dust particles within 40 AU of the central protostar (about twice the size of the orbit of Uranus in the solar system) were still small, while outside this radius, the size of the dust particles had begun to increase, which is the first step in planet formation. This is contrary to theoretical expectations that planet formation begins within the astrolabe.

The results provide surprising new information about the distribution of dust and other conditions when planets began to form. Future studies of more examples will further our understanding of planet formation.

Reference: "Dust enrichment and grain growth in the smooth disk around DGTau protostar revealed by ALMA three-band frequency observations", author: Satoshi Ohashi, MunetakeMomose, Akimasa Kataoka, AyaE Higuchi, Takashi Tsukagoshi, Taka Hiro Ueda, Claudio Codella, Linda Podio, Tomoyuki Hanawa, Nami Sakai, Hiroshi Kobayashi, Satoshi Okuzumi, and Hidekazu Tanaka, August 28, 2023, The Astrophysical Journal.

DOI:10.3847/1538-4357/ace9b9

Compiled source: ScitechDaily