The ALMA (Atacama Large Millimeter / submillimeter Array) observatory has revealed a Pair of massive baby stars growing in a salty cosmic soup 9,500 light-years away.
Each star is enveloped by a gaseous disk that includes sodium chloride molecules, commonly known as table salt, and hot water vapor. By analyzing radio emissions from salt and water, the team found that the discs rotate in opposite directions. This is the second detection of salt around massive young stars, and it confirms that salt is an excellent marker for exploring the immediate surroundings of giant baby stars.
There are stars of different masses in the Universe. The smallest are only one-tenth the mass of the Sun, while the largest are 10 times or more massive than the Sun. Regardless of mass, all stars form in cosmic clouds of gas and dust. Astronomers have enthusiastically studied the origins of stars, however, the massive star formation process is still veiled.
This is because massive star formation sites are farther from the earth, and massive baby stars are surrounded by massive clouds with complicated structures. These two facts prevent astronomers from getting clear views of the massive young stars and their formation sites.
A team of astronomers led by Kei Tanaka at Japan's National Astronomical Observatory used the power of ALMA to investigate the environment where massive stars form. They looked at the massive young binary IRAS 16547-4247. The team detected radio emissions from a wide variety of molecules.
In particular, sodium chloride (NaCl) and hot water (H2O) are associated in the vicinity of each star, that is, the circumstellar disk. On the other hand, other molecules such as methyl cyanide (CH3CN), which has been commonly observed in previous studies of massive young stars, were detected further away, but did not map out structures in the vicinity of the stars well.
"Sodium chloride is familiar to us as table salt, but it is not a common molecule in the Universe."Tanaka says in a statement." This was only the second detection of sodium chloride around massive young stars. The first example was around Orion KL Source I, but that's such a peculiar source that we weren't sure if the salt is suitable for seeing gas disks around massive stars. Our results confirmed that salt is actually a good marker. Since baby stars gain mass through disks, it is important to study the motion and characteristics of the disks to understand how baby stars grow. "
Further investigation of the discs shows a interesting clue about the origin of the pair. "We found a tentative sign that the disks are spinning in opposite directions," explains Yichen Zhang, a researcher at RIKEN. If stars are born as twins in a common large gaseous disk, then naturally the disks rotate in the same direction.
"Counter-rotation of the discs can indicate that these two stars are not real twinsbut a couple of strangers that formed in separate clouds and later paired up. "Massive stars almost always have some companions, so investigating the origin of massive binary systems is critical. The team hopes that further observation and analysis provide more reliable information on the secrets of his birth.
The presence of hot water vapor and sodium chloride, which were released by the destruction of dust particles, suggests the dynamic and hot nature of discs around massive baby stars. Interestingly, meteorite investigations indicate that the disk of the proto-solar system also experienced high temperatures in which dust particles evaporated.
Astronomers will be able to track these molecules released from dust particles well using the next-generation Very Large Array, currently in planning. The team anticipates that they can even get clues to understanding the origin of our Solar System by studying hot disks with sodium chloride and hot water vapor.
Baby stars IRAS 16547-4247 lie 9,500 light-years away in the constellation Scorpio. The total mass of stars is estimated to be 25 times the mass of the Sun, surrounded by a gigantic cloud with the mass of 10,000 suns.