05 October 2013

Astronomers Find Huge ‘Hot Core’ Enveloping Baby Star


Astronomers have discovered an infant star while looking at an infrared dark cloud that is about ten times larger than those found around typical solar-mass baby stars.

A team using the ALMA Observatory was looking at infrared dark cloud G34.43+00.24 MM3 when it discovered the baby star. Hot molecular clouds around new-born stars are known as “Hot Cores” and have temperatures that are 100 degrees hotter than normal molecular clouds.

The large size of the hot core discovered by ALMA shows that much more energy is emitted from the central baby star than typical solar-mass young stars. This could be due to the higher mass infall rate, or multiplicity of the central baby star, which indicates a large diversity in the star formation process.

Most stars are born as members of star clusters, so investigating infrared dark clouds is a crucial to understanding star formation because these clouds are where clusters of stars form. Inside hot cores, scientists find that various molecules. originally trapped in the ice mantle around dust particles, are sublimated. Organic molecules like methanol, ethyl cyanide, and methyl formate are abundant in these hot cores.

A detailed investigation shows that the hot core surrounding the baby star is as large as 240,000 astronomical units, or about 100 million miles across; for the sake of comparison, one astronomical unit equals the distance between the Sun and the Earth. Hot cores around low-mass young stars are typically several tens to a hundreds of astronomical units, so the hot core in MM3 is exceptionally large.

“Thanks to the high sensitivity and spatial resolution, we need only a few hours to discover a previously unknown baby star. This is an important step to understand the star formation process in a cluster forming region,” Takeshi Sakai of the University of Electro-Communications and leader of the study published in the Astrophysical Journal, said in a statement.

Sakai and colleagues also observed radio emission from the carbon sulfide and silicon monoxide in the hot core to reveal the detailed structure of the molecular outflow from the baby star. The speed of the emanated gas is about 17 miles per second and the extent is 4,400 astronomical units. The team determined that the age of the outflow is only about 740 years, making this star quite young and a very rare find.

“ALMA’s spatial resolution improves much more in the near future”, Sakai said. “Then much detail of the infalling material toward the protostar can be revealed, and it helps us answer to the mystery behind the diversity in star formation.”

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Takeshi Sakai, Nami Sakai, Jonathan B. Foster, Patricio Sanhueza, James M. Jackson, Marc Kassis, Kenji Furuya, Yuri Aikawa, Tomoya Hirota, Satoshi Yamamoto. ALMA OBSERVATIONS OF THE IRDC CLUMP G34.43 00.24 MM3: HOT CORE AND MOLECULAR OUTFLOWS. The Astrophysical Journal, 2013; 775 (1): L31 DOI: 10.1088/2041-8205/775/1/L31


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