ring on the northern side (where the streamer is) than the southern side. Finally, although there is not much gas falling into the inner disks, the accretion rate of gas has been measured to be ~ yr−1 which is at least the rate of accretion from the inner disks to the stars themselves. Therefore, the outer disk provides enough mass to replenish the inner disks. Possible protoplanets At the edge of the outer disk, there is a "hot spot" with additional gas, and at a higher temperature of about 40 K. There are also spiral-shaped formations within the disk. At the center of this "hot spot" may be a protoplanet termed GG Tauri Ac, which is still accreting mass. This would explain the higher gas density and temperature, as well as the spiral formations. If it exists, it would likely be about the mass of Neptune or smaller, given that it has not cleared out a gap at its location. Other planets could explain other spiral features within the disk. Chemistry The chemistry of circumstellar disks is important for understanding planetary formation. The inner disk, like other protoplanetary disks, is rich in simple molecules containing elements such as carbon and sulfur. In 2018, hydrogen sulfide () was reported, and in 2021, thioxoethenylidene (CCS) was reported to exist within the disk. Both are the first instances of those species known in a protoplanetary disk. The chemical mechanisms related to their formation are not very well understood. See also HL Tauri, a T Tauri star with a protoplanetary disk BD−22 5866, a quadruple star system with relatively low mass Taurus (Chinese astronomy) References Tauri, GG Taurus (constellation) T Tauri stars K-type main-sequence stars M-type main-sequence stars Circumstellar disks 5