Scientists using ALMA have discovered a very large hot molecular cloud around a very young star.
This hot cloud is about ten times larger than those found around typical solar-mass baby stars, which indicates that the star formation process has more diversity than ever thought.
Stars are formed in very cold (-260 degrees Celsius) gas and dust clouds.
Infrared dark clouds (IRDCs) are dense regions of such clouds, and thought that in which clusters of stars are formed. Since most of stars are born as members of star clusters, investigating IRDCs has a crucial role in a comprehensive understanding of the star formation process.
A baby star is surrounded by the natal gas and dust cloud, and the cloud is warmed up from its center. Temperature of the central part of some, but not all, of such clouds reaches as high as -160 degrees Celsius.
Inside hot cores, various molecules, originally trapped in the ice mantle around dust particles, are sublimated. Organic molecules such as methanol (CH3OH), ethyl cyanide (CH3CH2CN), and methyl formate (HCOOCH3) are abundant in hot cores.
International research team, led by Takeshi Sakai at the University of Electro-Communication, Japan, used ALMA to observe an IRDC named G34.43+00.24 MM3 (hereafter MM3) in the constellation Aquila (the Eagle).
They discovered a young object from which the methanol molecular line is strongly emitted. A detailed investigation tells them that the temperature of the methanol gas is -140 degrees Celsius.
This shows that MM3 harbours a baby star surrounded by a hot core.
The size of the hot core is as large as 800 by 300 astronomical units (1 au equals the mean distance from the Sun to the Earth, about 150 million km). Typical size of hot cores around low-mass young stars is several tens to a hundred AU, therefore the hot core in MM3 is exceptionally large.
This result has been published in Astrophysical Journal Letters.