18-Aug-2022: Scientists formulate model to trace elusive exo-moons from JWST data
Scientists have developed a model to trace the so far elusive exomoons – natural satellites that revolve around exoplanets (planets orbiting stars other than the Sun) with the help of the James Webb Space Telescope (JWST), launched in December 2021. This may also help detect habitable exo-moons in the future and understand new worlds beyond our own.
So far, five thousand exoplanets --- planets orbiting stars other than the Sun, have been discovered by using several ground-based and space telescopes such as Kepler, CoRoT, Spitzer, and Hubble space telescopes. However, the natural satellites or exomoon around any of these planets still remain untraced.
The Solar system is constituted of a large number of natural satellites with various sizes and mass, and many of them influence the ambient environment of the Solar planets. Therefore, a large number of exomoons are expected to be present, and they may play a crucial role in the habitability of rocky exoplanets in the habitable zone of their host stars. While most exoplanets are detected through photometric transit method, signals from exo-moons are too weak to detect mainly because of their extremely small size.
Scientists at the Indian Institute of Astrophysics, Bangalore, an autonomous institute of the Department of Science and Technology, have demonstrated that the newly launched James Webb Space Telescope (JWST) is sufficiently powerful to detect the transit signal of exomoons in the photometric light curves of moon hosting exoplanets.
Professor Sujan Sengupta and his graduate student Suman Saha have developed an analytical model that uses the radius and orbital properties of the host planet and its moon as parameters to model the photometric transit light curve of moon-hosting exoplanets by incorporating various possible orientations of the moon-planet-star system.
The co-alignment or non-coalignment of the orbits of the planet and the moon are used as parameters (using two angular parameters), and they can be used to model all the possible orbital alignments for a star-planet-moon system. Using these generic models and the analysis of photometric transit light curves of exoplanets that is being obtained by JWST, a large number of exomoons can be detected in near future. According to the researchers, an exo-moon around a gas giant planet like Jupiter in the habitable zone of the host star where temperature is appropriate for water to exist in liquid state may harbour life. Under favourable alignment of moon-planet-star, such exomoon may also be detected by JWST. The research has been accepted for publication in The Astrophysical Journal, which is published by the American Astronomical Society (AAS).
11-Jan-2018: James Webb Space Telescope successfully completes critical testing
NASA’s James Webb Space Telescope the world’s premier infrared space observatory of the next decade — has successfully completed critical testing in a massive thermal vacuum chamber, enabling it to function properly in the extremely cold and airless environment in space in 2019.
The James Webb Space Telescope (JWST) is the largest space telescope ever built. It is an international collaboration of about 17 countries including NASA, European Space Agency (ESA) and the Canadian Space Agency (CSA). When it is launched in 2019, it will be
the world’s biggest and most powerful telescope.
It features a 21.3-foot-wide primary mirror made up of 18 adjustable gold-coated segments. Webb Telescope is a barrier-breaking mission for engineers and astronomers that will help solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.
Webb telescope arrived at NASA's Johnson Space Centre in Houston in May 2017, where it underwent critical cryogenic testing for nine months inside Chamber A, a massive thermal vacuum chamber at the centre. On July 10, the cryogenic testing of the telescope began. During approximately 100 days in the chamber, Webb was put through a series of tests designed to ensure the telescope functioned as expected in an extremely cold, airless environment akin to that of space.
Scheduled for launch in the spring of 2019 aboard a European Ariane 5 rocket, the gamut of tests ensured that Webb will safely reach its orbit at Earth's second Lagrange point (L2) and be able to successfully perform its science mission.
When it is launched into space it will be able to peer back in time 3.5 billion years, teaching us more than ever before about the start of the universe. The telescope will be used to look back to the first galaxies born in the early universe more than 13.5 billion years ago, and observe the sources of stars, exoplanets, and even the moons and planets of our solar system.
8-Aug-2022: Deciphering of physical characteristics of a rare class of supernovae hint towards advanced stage of evolution of special class of very hot & massive stars
A team of scientists have deciphered the physical characteristics of a rare class of supernovae called Type Ibn Supernovae (SNe).
Type Ibn supernovae are a rare class of stripped-envelope supernovae interacting with a helium-rich dense circumstellar medium (CSM). These SNe are unique and essential because they help to explore about the typical density, velocity, and composition of the nearby SN environment. They are more luminous than normal supernovae (SNe), which are huge stellar explosions releasing a humongous amount of energy. SN 2019wep is one of the very rare SNe for which a long-term monitoring campaign was launched to decipher the physical characteristics following detection of flash ionisation signatures. This is a unique study where the SN properties are probed along with environmental studies.
An international team of researchers from Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science & Technology, Government of India, Hiroshima University, Japan, and Las Cumbres Observatory, USA, deciphered the physical characteristics of SN 2019wep.
The researchers have identified rare signatures of flash ionisation in the very early spectra of SN 2019wep. The rare signatures hint towards a special class of very hot and massive stars in advanced stages of stellar evolution, having depleted hydrogen, called Wolf-Rayet progenitor star. The early signatures of flash ionisation, especially Helium, were previously traced in some SNe mostly due to the CSM recombination. The team led by Anjasha Gangopadhyay, a former research scholar at ARIES (presently Assistant Professor at Hiroshima University) and Kuntal Misra, scientist at ARIES, traced the unique Carbon and Nitrogen signatures in the optical waveband deciphering the physical characteristics.
The SN Ibns tracked in the research published in The Astrophysical Journal is a peculiar one, which shows a transitioning nature and residual H-alpha. In general, SN Ibn are expected to show He features only, however, this is a unique case where we can see some remaining Halpha in the SN spectrum. The researchers said that SNe Ibns are typically short-lived, and dedicated follow-up campaigns will help unravel the mysteries of the unique members of Type Ibn class and their ancestors.
29-Jul-2022: DST INSPIRE fellow leads study unveiling the secret of distant dwarf galaxy formation
Signals from the outskirts of a galaxy that is not more than 150 million years indicate formation of newer stars by the galaxies beyond their visible boundaries, according to a recent study. The research traces how these young stars, that are found in the form of star-forming complexes or clumps, migrate towards the inner regions and gradually build up the stellar content of these galaxies.
Astrophysicists have been exploring to learn how galaxies, the basic building blocks of our Universe, form and evolve into present-day ones. But the picture still remains incomplete.
The Ultraviolet Imaging Telescope (UVIT) onboard AstroSat, India's first dedicated multi-wavelength space observatory, has recently detected faint emission of Far Ultraviolet (FUV) light in the outskirts of a sample of distant Blue Compact Dwarf (BCD) galaxies that are about 1.5 - 3.9 billion light-years away. These are small galaxies usually characterized by their centrally concentrated star formation.
The discovery, a joint outcome of a study by an international team of astronomers from India, the USA and France, is a significant step towards tracing the mysteries of galaxy formation. The study published in the journal Nature was conceived by Prof. Kanak Saha of Inter University Center for Astronomy and Astrophysics (IUCAA), Pune.
Anshuman Borgohain, the lead author of the article and a recipient of the INSPIRE Fellowship of the Department of Science and Technology (DST), said that the occurrence of such young stars at the periphery of galaxies is usually a tell-tale signature of recent gas accretion from their surroundings that fuel the star-formation and subsequent galaxy growth. The researcher at Tezpur University worked under the joint supervision of Dr. Rupjyoti Gogoi, Assistant Professor of Physics at Tezpur University, and Prof. Kanak Saha, Professor of Astronomy at IUCAA.
“The resolving power of UVIT and UV deep field imaging techniques has been the key to spotting these very young, large star-forming clumps. Due to their large distances from us, it was a challenging task to establish the detection of these faint, extremely blue star-forming clumps with million solar masses,” said Prof. Kanak Saha, highlighting that it helped witnessing the 'live' formation of these far-way dwarf galaxies.
Dr. Bruce Elmegreen, a principal research staff in the IBM Research Division, USA, who contributed to the study, said, “It has been a mystery how some small galaxies like these can have such active star formation. These observations suggest that accreting gas in the far outer parts can be forced to move inward through torques exerted by giant gas and stellar complexes. This migration builds up the central density over the galaxy's lifetime.”
Coauthor Prof. Francoise Combes of Observatoire de Paris, France, Professor at the College de France, elaborated that the discovery illustrates how surprisingly the star formation can proceed in relatively pristine low-metallicity gas. “The outer portions of these gaseous disks are unstable towards fragmentation, even though these dwarfs must be dominated by dark matter, which would limit the fragmentation," she explained. Coauthor Prof. Shyam Tandon, ex-emeritus Professor at IUCAA and PI of UVIT, highlighted the importance of UVIT data in this study.
Dr. Rupjyoti Gogoi, Assistant Professor of Physics at Tezpur University and associate at IUCAA, said that the work, which utilizes data from India’s indigenous satellite, AstroSat, could be an inspiration to young researchers of the country, while Prof. Somak Raychaudhury, Director of IUCAA Pune, and Prof. Vinod K. Jain, the Vice Chancellor of Tezpur University underlined the benefits of such collaborative work.