Blue Stars In A New Class Of Stellar System. Know All About The New Discovery

The new stellar systems contain only young, blue stars, and are about the size of tiny dwarf galaxies. The blue stars are distributed in an irregular pattern.

Astronomers at University of Arizona have identified five examples of a new class of stellar system that are not quite galaxies and only exist in isolation. The new stellar systems appear as "blue blobs" through a telescope, according to the researchers.

The scientists described their findings at the 240th meeting of the American Astronomical Society. The new stellar systems contain only young, blue stars, and are about the size of tiny dwarf galaxies. The blue stars are distributed in an irregular pattern and seem to exist in surprising isolation from any potential parent galaxy.

Where Are The Stellar Systems Located?

The stellar systems are located within the relatively nearby Virgo galaxy cluster. It is challenging to identify the origins of the five systems because they are separated from any potential parent galaxies by over 300,000 light years in some cases.

Another research team, led by the Netherlands Institute for Radio Astronomy's Elizabeth Adams, compiled a catalogue of nearby gas clouds. This provides a list of potential sites of new galaxies. After this, several research groups, including one led by University of Arizona associate astronomy professor David Sand, started looking for stars that could be associated with those gas clouds. 

What Is The First Collection Of Stars Called?

According to a statement released by University of Arizona, the gas clouds were thought to be associated with the Milky Way galaxy, and most of them probably. However, when the first collection of stars, called SECCO1, was discovered, astronomers realised that it was not near the Milky Way, but rather in the Virgo cluster. This is much farther away, but still very nearby in the scale of the universe. 

According to the statement, Michael Jones, the lead author of a study published in arXiv, an open-access repository of electronic preprints, said SECCO1 was one of the very unusual "blue blobs". The findings of the study, which describes the new stellar systems, were presented during the 240th American Astronomical Society meeting in Pasadena, California, last week.

Jones said it is a lesson in the unexpected, and that when one is looking for things, they are not necessarily going to find the thing they are looking for, but they might find something else very interesting.

How Were The Observations Made?

According to the University of Arizona, the researchers obtained their observations from the Hubble Space Telescope, the Very Large Array telescope in New Mexico and the Very Large Telescope in Chile. 

Most Of The Stars In Each System Are Blue

The scientists learned that most of the stars in each system are very blue and very young and that they contain very little atomic hydrogen gas, which is significant because star formation begins with atomic hydrogen gas. This eventually evolves into dense clouds of molecular hydrogen gas before forming into stars.

Jones said the researchers observed that most of the systems lack atomic gas, but that does not mean there is no molecular gas. He added that there must be some molecular gas because they are still forming stars, and the existence of mostly young stars and little gas signals that these systems must have lost their gas recently. 

The researchers had not expected the combination of blue stars and lack of gas. Also, there was a lack of older stars in the systems, which was unexpected, because most galaxies have older stars. These galaxies are referred to as being "red and dead" by astronomers.

Difference Between Stars Born Red And Blue Stars

Jones said stars that are born red are lower mass and therefore live longer than blue stars, which burn fast and die young. Therefore, old red stars are usually the last ones left living. The blue stars are dead because they do not have any more gas with which to form new stars. 

Jones said the blue stars are like an oasis in the desert. 

According to the statement, the fact that the new stellar systems are abundant in metals hints at how they might have formed.

How Were The Stellar Systems Formed?

Jones said that to astronomers, metals are any element heavier than helium. He added that this tells us that these stellar systems formed from gas that was stripped from a big galaxy, because metals are built up by many repeated episodes, and one only really gets that in a big galaxy.

There are two main ways gas can be stripped from a galaxy, the first being tidal stripping. This occurs when two big galaxies pass by each other and gravitationally tear away gas and stars. The second way gas can be stripped from a galaxy is known as ram pressure stripping.

Jones said this is like if one belly flops into a swimming pool. He added that when a galaxy belly flops into a cluster that is full of hot gas, then it gets forced out behind it. 

In order for the blue blobs to have become as isolated as they are, they must have been moving very quickly. Therefore, the researchers prefer the ram pressure stripping explanation, according to the University of Arizona.

The astronomers believe that one day, the systems will eventually split off into individual clusters of stars and spread out across the larger galaxy cluster.