- Astronomers observe unusual binary stars that have a mass ratio of 80:1.
- The observation has been made possible by a large telescope network, Atacama Large Millimeter Array.
- One of these stars is 40 times more massive than our Sun, while the other one weighs half the mass of the Sun.
Stars are formed within the cloud of gas and dust and scattered throughout most galaxies in the universe. The formation mechanisms of massive stellar objects are still not well-known due to their enormously large distances and extreme embedded nature.
However, we do know that these clouds collapse under gravity, they start rotating faster and forms a disc around them. The matter in the center starts heating up, as the cloud collapses. This hot core of the collapsing cloud –called protostar — eventually becomes a star.
In case of low mass stars (including our Sun), plants can form inside their discs. Computer simulations have shown that spinning clouds often break into 2 or 3 blobs, which explains why most stars in our galaxy are found in pairs or groups of multiple celestial bodies.
Recently, a team of British astronomers used Atacama Large Millimeter Array, a massive telescope network to capture the most detailed view of the formation of a young star, named MM 1a. While observing it, they found that it wasn’t in fact one star, but two.
MM 1a is a young massive star enclosed by a disc of dust and gas. Its companion, named MM 1b, is a faint object detected outside the MM 1a’s disc. It seemed to be revolving around the MM 1a star, which was the main subject of investigation.
Both the star and its cloud disc are so huge that, instead of observing a planet inside the disc, astronomers are witnessing another star being formed. This could be the first example of a fragmented disc to be identified around a young massive star.
The Unstable Beginning And Mass Of The Young Star
The suitable environment for the formation of MM 1b lies outside the massive, cold discs. Since these discs are gravitationally unstable and they can’t even stand against the force of their own gravity, they collapse into fragments.
Artistic impression of MM 1a and MM 1b. Courtesy: J. D. Ilee/University of Leeds
The study suggests that MM 1b might be surrounded by its own disc that is capable of forming planets of its own. But since massive stars like MM 1a have a lifespan of only a million years, the planets formed in the disc of MM 1b won’t last for long.
To calculate the mass of both stars, researchers measured the tiny shifts in the light frequency emitted by the gas, and the amount of radiation coming from the dust. They found that the massive young star MM 1a is 40 times more massive than our Sun, while the faint star MM 1b weighs half the mass of the Sun.
So far, the majority of the binary stars are found to be equal in mass, and likely born together as siblings. The mass ratio of MM 1a and MM 1b (80:1) is quite uncommon in astrophysics, indicating a whole new mechanism of star formation.
The observation has been made possible by Atacama Large Millimeter Array: researchers used 66 dishes of this large telescope in the Interferometry to image the precise surrounding of MM 1a. In the next year, they will simulate the power of a telescope that is 16 kilometers across (compared to the current simulation of 4 kilometers across).