Scientists from the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science and Technology, have recently unveiled the reasons behind the rapid star formation in some dwarf galaxies. Dwarf galaxies, considerably smaller and less luminous than massive ones like the Milky Way, are the most common kind of galaxy in the universe. Intriguingly, despite their size, they frequently form stars at a faster rate than their larger counterparts.
Dwarf Galaxies: An Overview
Dwarf galaxies are estimated to be 100 times less massive than the Milky Way. Despite their abundance, they’re challenging to detect due to their low luminosity, minimal mass, and small size. The rate at which they form stars is typically slower than that of larger galaxies. Interestingly, however, some dwarf galaxies have shown unusual behavior, forming new stars at a mass-normalized rate that is 10-100 times greater than that of the Milky Way.
It’s worth noting that these intense bouts of star-formation activity in dwarf galaxies are relatively short-lived, lasting only a few tens of million years – a small fraction of these galaxies’ lifespan, which stretches into billions of years.
The Findings of ARIES Astronomers: What Triggers Intense Star Formation?
1.
Hydrogen Distribution Irregularities:
To sustain high rates of star formation, a considerable density of Hydrogen is required within the galaxies. The scientists found that in those dwarf galaxies undergoing rapid star formation, Hydrogen distribution is often irregular and not constrained to well-defined orbits. These galaxies also show multiple nuclei and high concentrations of ionized hydrogen in their central regions, indicating highly disturbed distribution of this vital element.
2.
Galaxy-Galaxy Collision:
Evidence of recent collisions or interactions with other galaxies was also detected. Isolated clouds, plumes, and tails of Hydrogen around these dwarf galaxies suggest that galactic encounters may have led to the scattering of gas as debris around these galaxies, further fueling star formation.
Telescopes Used in the Study
For this study, scientists utilized the 1.3-meter Devasthal Fast Optical Telescope (DFOT) located near Nainital, Uttarakhand, and the Giant Metrewave Radio Telescope (GMRT) situated in Maharashtra.
Star Formation: A Brief Overview
Stars are born within dust and gas clouds that permeate most galaxies. The turbulence within these clouds results in dense knots under their own gravitational attraction, leading to the birth of stars.
The process begins when a dense ball of gas, known as a prestellar core, forms from dust and gas in the space between stars (InterStellar Medium, ISM). A disk forms around the core during the collapse and jets are emitted at the poles. Eventually, the star stops growing but gas still falls onto the disk. After a few million years, this process also stops, marking the birth of the star while leftover materials form planets, asteroids, or comets, resulting in a solar system. Typically, such a system has a lifespan of about 10 billion years after formation.