Why some stars are bigger than others

Washington – Astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to survey the cores of some of the darkest, coldest, and densest clouds in Milky Way galaxy to search for the telltale signs of star formation.

These objects, known as infrared dark clouds, were observed approximately 10,000 light-years away in the direction of the constellations of Aquila and Scutum.

Jonathan Tan, an astrophysicist at the University of Florida, Gainesville, said that a starless core would indicate that some force was balancing out the pull of gravity, regulating star formation, and allowing vast amounts of material to accumulate in a scaled-up version of the way our own Sun formed.

The astronomers from the US, the UK, and Italy used ALMA to look inside these cores for a unique chemical signature involving the isotope deuterium to essentially take the temperatures of these clouds to see if stars had formed.

Deuterium is important because it tends to bond with certain molecules in cold conditions. Once stars turn on and heat the surrounding gas, the deuterium is quickly lost and replaced with the more common isotope of hydrogen.

The ALMA observations detected copious amounts of deuterium, suggesting that the cloud is cold and starless. This would indicate that some counter force is forestalling core collapse and buying enough time to form a massive star.

The researchers speculate that strong magnetic fields may be propping up the cloud, preventing it from collapsing quickly.

The study has been published in the Astrophysical Journal.