In the News

Image credit: IISc Office of Communication & Swadha PardesiRecord-breaking detection of radio signal from atomic hydrogen in extremely distant galaxy using GMRT: Atomic hydrogen emits radio waves of 21 cm wavelength, which can be detected using low frequency radio telescopes like the GMRT. Thus, 21 cm emission is a direct tracer of the atomic gas content in both nearby and distant galaxies. However, this radio signal is extremely weak and it is nearly impossible to detect the emission from a distant galaxy using current telescopes due to their limited sensitivity. Until now, the most distant galaxy detected using 21 cm emission was at redshift z=0.376, which corresponds to a look-back time – the time elapsed between detecting the signal and its original emission – of 4.1 billion years (Redshift represents the change in wavelength of the signal depending on the object’s location and movement; a greater value of z indicates a farther object). Using GMRT data, Arnab Chakraborty, postdoctoral researcher at the Department of Physics and Trottier Space Institute of McGill University, and Nirupam Roy, Associate Professor, Department of Physics, IISc have detected a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29. “Due to the immense distance to the galaxy, the 21 cm emission line had redshifted to 48 cm by the time the signal travelled from the source to the telescope,” says Chakraborty. The signal detected by the team was emitted from this galaxy when the universe was only 4.9 billion years old; in other words, the look-back time for this source is 8.8 billion years. This detection was made possible by a phenomenon called gravitational lensing, in which the light emitted by the source is bent due to the presence of another massive body, such as an early type elliptical galaxy, between the target galaxy and the observer, effectively resulting in the “magnification” of the signal. “In this specific case, the magnification of the signal was about a factor of 30, allowing us to see through the high redshift universe,” explains Roy. [Hindu, HT, DH, ToI, India Today, Frontline, More]

Image credit: Jonas Syed/MPIA/THOR teamAstronomers discover a huge filament of atomic hydrogen, a possible precursor to star-forming clouds: A group of astronomers, led by researchers from the Max Planck Institute for Astronomy (MPIA), have identified one of the longest known structures in the Milky Way. It stretches some 3900 light-years and consists almost entirely of atomic hydrogen gas. This filament, called “Maggie”, could represent a link in the matter cycle of the stars. Analysing the measurements suggests that the atomic gas in this lane converges locally to form molecular hydrogen. When compressed in large clouds, this is the material from which stars eventually form. Hydrogen is the most widespread substance in the Universe and the main ingredient in the formation of stars. Unfortunately, detecting individual clouds of hydrogen gas is a demanding task, which makes research into the early phases of star formation challenging. That is why the recent discovery of a surprisingly long structure, a filament, of atomic hydrogen gas by an international research group led by astronomers from the Max Planck Institute for Astronomy (MPIA) in Heidelberg is all the more exciting. [Nature, Daily Mail, METRO, More]

Image credit: Andreas Brunthaler/MPIfR/GLOSTAR teamInternational study offers new insights into star formation in Milky Way: An international team of astronomers has carried out an extensive new survey of our galaxy, the Milky Way, which has revealed previously unseen signatures with unprecedented sensitivity and details that hint at how stars form and die, complex processes that have fascinated researchers for centuries. The results were published in a series of papers in Astronomy & Astrophysics by the team, which includes scientists from the Indian Institute of Science (IISc) and the Indian Institute of Space Science and Technology (IIST). The data 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 National Radio Astronomy Observatory (NRAO), USA, and the Effelsberg 100-m radio telescope operated by the Max Planck Institute for Radio Astronomy (MPIfR), Germany, as part of the GLOSTAR (Global View on Star formation in the Milky Way) project. Nirupam Roy, Assistant Professor at the Department of Physics, and Rohit Dokara, his former undergraduate student from IISc, as well as Jagadheep D Pandian, Associate Professor at the Department of Earth and Space Sciences in IIST are among the Indian scientists who are part of the GLOSTAR project. Dokara, now a PhD student at MPIfR, is the first author on one of the papers that reports the detection of new supernova remnants (SNRs) – structures born from the explosive death of massive stars – in our galaxy. [New Indian Express, DH, ToI, Hindu, More]

Image credit: Veena V. S. et al. (2019)Indian astronomers find evidence of supernova remnants: For several centuries, astronomers have been fascinated by large explosions that occur at the end of a stars lifecycle, resulting in a phenomenon called supernova. A team of Indian astronomers has found tell-tale evidence of a supernova explosion in a star-forming region called G351.7–1.2. The evidence is in the form of a high velocity jet of atomic hydrogen. The team consisted of scientists from Indian Institute of Space science and Technology (IIST), Thiruvananthapuram, Indian Institute of Science (IISc), Bengaluru and National Centre of Radio Astrophysics (NCRA), Pune. The research team, led by V. S. Veena of IIST, found that the jet is in the direction of Scorpius constellation. The explosion should have resulted in a compact stellar object such as a neutron star or a pulsar or a black hole. However, there is no trace of either yet. “We found high-velocity jets of atomic hydrogen extending to about 20 light years racing at a speed of about 50 km per second in opposite directions in the neighbourhood. Clearly, there was a supernova explosion. However, despite our efforts, we could not find the leftover of the massive star,” observed Sarita Vig, a faculty member at IIST and a member of the study team. The presence of highly directional jet points towards the presence of a compact object such as a black hole or a neutron star at the centre. “However, our efforts in finding it at low radio frequencies did not yield positive results,” added Nirupam Roy, another member of the team based at IISc. [Vigyan Prasar, Businessline]

Image credit: Bill Saxton, NRAO/AUI/NSFRadio Telescopes Unravel Mystery of Nova Gamma Rays: Highly-detailed radio-telescope images have pinpointed the locations where a stellar explosion called a nova emitted gamma rays, the most energetic form of electromagnetic waves. The discovery revealed a probable mechanism for the gamma-ray emissions, which mystified astronomers when first observed in 2012. “We not only found where the gamma rays came from, but also got a look at a previously-unseen scenario that may be common in other nova explosions,” said Laura Chomiuk, of Michigan State University. A nova occurs when a dense white dwarf star pulls material onto itself from a companion star, triggering a thermonuclear explosion that blows debris into interstellar space. Astronomers did not expect this scenario to produce high-energy gamma rays. However, in June of 2012, NASA’s Fermi spacecraft detected gamma rays coming from a nova called V959 Mon, some 6500 light-years from Earth. At the same time, observations with the Karl G. Jansky Very Large Array (VLA) indicated that radio waves coming from the nova probably were caused by subatomic particles moving at nearly the speed of light interacting with magnetic fields. The high-energy gamma-ray emission, the astronomers noted, also required such fast-moving particles. Later observations with the extremely-sharp radio “vision” of the Very Long Baseline Array (VLBA) and the European VLBI network revealed two distinct knots of radio emission. These knots then were seen to move away from each other. This observation, along with studies made with e-MERLIN in the UK, and another round of VLA observations in 2014, provided the scientists with information that allowed them to put together a picture of how the radio knots, and the gamma rays, were produced. [ScienceNews, ScienceDaily, Astronomy.com, More]