International study offers new insights into star formation in the Milky Way

An international team of astronomers carried out an extensive new survey of the Milky Way that has revealed previously unseen signatures with unprecedented sensitivity and details that hint at how stars form and die. The results were published in a series of papers on Astronomy & Astrophysics by the team, which includes scientists from the Indian Institute of Science (IISc), Bengaluru, and the Indian Institute of Space Science and Technology (IIST), Thiruvananthapuram.

The research team also included scientists from Max Planck Institute for Radio Astronomy (MPIfR), Germany, and National Radio Astronomy Observatory (NRAO), USA, and collaborators from institutions in the United Kingdom, South Africa, Mexico, France, and Australia. According to an IISc release, information for the survey, which spanned a large part of the Milky Way, was gathered using two powerful radio telescopes: the Karl G. Jansky Very Large Array (VLA) at the NRAO and the Effelsberg 100m radio telescope operated by the MPIfR, as part of the GLOSTAR (Global View on Star formation in the Milky Way) project.

Nirupam Roy, assistant professor in the Department of Physics, Rohit Dokara, his former undergraduate student from IISc, Jagadheep D. Pandian, associate professor in the Department of Earth and Space Sciences at IIST are among the Indian scientists who are part of the GLOSTAR project.

A release said Mr. Dokara, now a Ph.D student at MPIfR, is the first author on one of the papers, which reports the detection of new supernova remnants (SNRs) — structures born from the explosive death of massive stars — in our galaxy.

“Previous surveys have detected only about one-third of the expected number of SNRs in the Milky Way (which is nearly 1,000). The GLOSTAR team has now discovered 80 new SNR candidates in the VLA data alone. They were also able to confirm the presence of 77 previously discovered SNR candidates and reclassify a few that were misidentified,” stated the release, also quoting Mr. Dokara as saying that this was an important step towards solving the long-standing mystery of missing supernova remnants.

The researchers were able to detect other traces of star formation, one of them radio emission from methanol molecules in a nearby large star-forming complex called Cygnus X. These, the release said, are typically emitted from massive stars in very early stages of formation. The team was also able to detect dense pockets of ionised hydrogen, another telltale sign of the presence of massive young stars, the release added.

Mr. Roy said young stars are usually surrounded by thick clouds of dust and gas. Because visible light gets absorbed in this dense cloud around stars, most optical telescopes don’t reveal much. What people look for, instead, are radio emissions.

“Since the GLOSTAR survey detects a wide range of radio emissions such as that from methanol molecules to ionised hydrogen, it is able to probe the formation of massive stars from very early to relatively late stages, which is important to get a complete picture of star formation in the Milky Way,” Mr. Pandian said.

The IISc release explained that the Effelsberg radio telescope was a single large dish spanning 100 m in diameter, capable of detecting large-scale structures, whereas the VLA was a collection of small antennas working together as an interferometer to capture the details in high resolution. The data pooled from both telescopes helped the researchers paint a more comprehensive picture of different astrophysical objects in the region.