arXiv subjects

Priya Hasan

Publications and source records attributed to Priya Hasan.

At least 19 recordsLinked to original sources

arXiv2026

The Era of Extremely Large Optical Telescopes II: The GMT and TMT

The advent of Extremely Large Telescopes (ELTs) ground-based optical and infrared observatories with primary mirrors exceeding 20m marks a transformative era in observational astronomy. This article explores the dawn of this new age, focusing on two of the next generation of optical/ infrared facilities: the Giant Magellan Telescope (GMT) and the Thirty Meter Telescope (TMT)\footnote{An accompanying paper by the author is on the European Extremely Large Telescope (ELT).} We describe the key technological innovations enabling the construction of these ambitious observatories, notably, segmented mirror design, advanced adaptive optics (AO), and laser guide star systems. Collectively, these breakthroughs yield more than an order of magnitude increase in both light-gathering area and spatial resolution, delivering image sharpness that, for widefield observations, surpassing space-based telescopes. We shall also discuss the comparison of space and ground-based telescopes and highlight their individual strengths and why space telescopes are not the solution to the satellite interference to ground-based telescopes. Ground based telescopes will continue to always be leaders in astronomical observations.

physics.pop-ph↗

arXiv2026

The Era of Extremely Large Optical Telescopes: The ELT

The advent of Extremely Large Telescopes ELTs, ground-based optical or infrared observatories with primary mirrors exceeding 20 m heralds a transformative epoch in observational astronomy. This article examines the dawn of this new era and the three upcoming facilities in the optical infrared band the Giant Magellan Telescope GMT, the Thirty Meter Telescope TMT, and the European Extremely Large Telescope ELT. This article will focus on the ELT, while a sequel will cover GMT and TMT. We describe the key technological breakthroughs enabling its construction, most notably the segmented mirror design, advanced adaptive optics AO, and laser guide star systems. These innovations will deliver more than an order of magnitude leap in light-gathering area and spatial resolution, providing image sharpness exceeding that of spacebased telescopes for widefield observations. The scientific impact of the ELT is profound and multifaceted. We discuss its inception and construction milestones and explore its potential to directly image and characterize the atmospheres of Earth like exoplanets, searching for biosignatures, and trace the formation of the first stars, galaxies, and supermassive black holes. This paper concludes that ELTs are not mere incremental improvements but foundational instruments that will redefine the frontiers of astrophysics, address some of science's most enduring questions, and inevitably lead to discoveries beyond current prediction.

physics.pop-ph↗

arXiv2026

The Betelgeuse Enigma: The Betelbuddy Hypothesis

In the past six years, Betelgeuse has been in the news and drawn significant public interest. Starting in October 2019, Betelgeuse underwent a striking dimming event, fading from magnitude 0.5 to 1.7 by mid February 2020 a threefold decrease in brightness This gave rise to a number of speculative debates that the star was on the verge of a supernova, a moment of eerie quiet before the cosmic outburst. In a previous article, the author discussed the most accepted explanation to the dimming caused by episodic mass loss that released large dust grains, which obscured Betelgeuse's light and made it appear fainter. This interpretation suggested that the dimming was not a precursor to a supernova, as Betelgeuse is likely still far from reaching that stage. On 21 July 2025, the existence of the companion star was confirmed with direct imaging, for the first time, by the alopeke instrument on the 8.1 m Gemini North telescope. The companion is 6 magnitudes fainter than Betelgeuse and orbits close to Betelgeuse itself, within the supergiant star's extended outer atmosphere. The stellar companion was detected at an angular separation of 52 mas and a position angle of 115 deg east of north. These measurements, along with its brightness, being roughly 6 magnitudes fainter than Betelgeuse at 466 nm, are in excellent agreement with dynamical predictions. Although this was only a 1.5 sigma detection, the agreement in the companion's appearance, separation, position angle, magnitude difference, and estimated mass is reasonable, making the result tentatively acceptable. The next optimum period for observations is November 2027, when we hope to get better observations. This article describes the interesting twists and turns of this study and what lies in the future for Betelgeuse and its companion, Betelbuddy or Siwarha.

astro-ph.SR↗

arXiv2024

Status of Astronomy Education in India: A Baseline Survey

We present the results of a nation-wide baseline survey, conducted by us, for the status of Astronomy education among secondary school students in India. The survey was administered in 10 different languages to over 2000 students from diverse backgrounds, and it explored multiple facets of their perspectives on astronomy. The topics included students' views on the incorporation of astronomy in curricula, their grasp of fundamental astronomical concepts, access to educational resources, cultural connections to astronomy, and their levels of interest and aspirations in the subject. We find notable deficiencies in students' knowledge of basic astronomical principles, with only a minority demonstrating proficiency in key areas such as celestial sizes, distances, and lunar phases. Furthermore, access to resources such as telescopes and planetariums remain limited across the country. Despite these challenges, a significant majority of students expressed a keen interest in astronomy. We further analyze the data along socioeconomic and gender lines. Particularly striking were the socioeconomic disparities, with students from resource-poor backgrounds often having lower levels of access and proficiency. Some differences were observed between genders, although not very pronounced. The insights gleaned from this study hold valuable implications for the development of a more robust astronomy curriculum and the design of effective teacher training programs in the future.

physics.ed-ph↗

arXiv2024

A Detailed Study of Dwarf Galaxies in the Core of the Coma Cluster

In an earlier paper, we determined the morphological types of galaxies in the Coma Cluster using data from the HST/ACS Coma Cluster treasury survey. We found that of the 132 members, 51 are non dwarfs and 81 are dwarfs. We define dwarfs to have a absolute luminosity $M_{F814W}\geq -18.5$ as in \cite{2012ApJ...746..136M}. In this paper, we determine the morphological types of these dwarf galaxies and make a detailed study of their properties. Using GALFIT, we determine the structural properties of our sample and with spectroscopic redshifts, we determined memberships and distances to identify dwarfs. A visual examination of the residual images reveals that our sample of 78 dwarf galaxies comprises of: dwarf lenticular (\textit{dS0}) 22\%, dwarf Elliptical ($dE$) 69\%, dwarf spirals (\textit{dSp}) 4\%, dwarf ring (\textit{dring}) 1\%, dwarf barred spirals (\textit{dSBp}) 3\% and dwarf irregular (\textit{dIrr}) 1\% galaxies. We find that the bulge-disk decomposition (S\'ersic + exponential) fits are good only for the \textit{dS0} galaxies. The remainder of the sample gives good fits only for single S\'ersic fits. The Colour Magnitude Relation (CMR) shows that the $dEs$ are redder and fainter than the rest of the sample (except one $dIrr$ galaxy). The Kormendy relation reveals that $dE$ galaxies have lower surface brightness than the rest of the sample. Our research leads us to the conclusion that dwarf galaxies appear to have a different formation and evolution process than non-dwarf galaxies.

astro-ph.GA↗

arXiv2024

Membership determination in open clusters using the DBSCAN Clustering Algorithm

In this paper, we apply the machine learning clustering algorithm Density Based Spatial Clustering of Applications with Noise (DBSCAN) to study the membership of stars in twelve open clusters (NGC~2264, NGC~2682, NGC~2244, NGC~3293, NGC~6913, NGC~7142, IC~1805, NGC~6231, NGC~2243, NGC 6451, NGC 6005 and NGC 6583) based on Gaia DR3 Data. This sample of clusters spans a variety of parameters like age, metallicity, distance, extinction and a wide parameter space in proper motions and parallaxes. We obtain reliable cluster members using DBSCAN as faint as $G \sim 20$ mag and also in the outer regions of clusters. With our revised membership list, we plot color-magnitude diagrams and we obtain cluster parameters for our sample using ASteCA and compare it with the catalog values. We also validate our membership sample by spectroscopic data from APOGEE and GALAH for the available data. This paper demonstrates the effectiveness of DBSCAN in membership determination of clusters.

astro-ph.GA↗

arXiv2024

Using GMM in Open Cluster Membership: An Insight

The unprecedented precision of Gaia has led to a paradigm shift in membership determination of open clusters where a variety of machine learning (ML) models can be employed. In this paper, we apply the unsupervised Gaussian Mixture Model (GMM) to a sample of thirteen clusters with varying ages ($log \ t \approx$ 6.38-9.64) and distances (441-5183 pc) from Gaia DR3 data to determine membership. We use ASteca to determine parameters for the clusters from our revised membership data. We define a quantifiable metric Modified Silhouette Score (MSS) to evaluate its performance. We study the dependence of MSS on age, distance, extinction, galactic latitude and longitude, and other parameters to find the particular cases when GMM seems to be more efficient than other methods. We compared GMM for nine clusters with varying ages but we did not find any significant differences between GMM performance for younger and older clusters. But we found a moderate correlation between GMM performance and the cluster distance, where GMM works better for closer clusters. We find that GMM does not work very well for clusters at distances larger than 3~kpc.

astro-ph.GA↗

arXiv2023

Exploring the collinear Lagrangian points of exoplanet systems with P-R drag and oblateness

In this paper we study the location and stability of the collinear Lagrangian points for the RTBP for the case in which one of the primary bodies is radiating and the other is oblate. We consider the effect of Poynting-Roberson drag and investigate how the location and stability of the Lagrangian points change with changes in the radiation parameter $\beta$ and oblateness $a$. We apply our results to ten exoplanet systems -- CoRoT-2~b, TOI-1278~b, HAT-P-20~b, Kepler-75~b, WASP- 89~b, TIC 172900988~b, NGTS 9~b, LP 714 - 47~b, WASP- 162~b and XO- 3~b, data of which has been taken from NASA exoplanet archives, with the aim of finding locations in these exoplanet systems where one can detect asteroids, primodial material or seeds where planet formation can take place. We find that the location of the collinear Lagrangian points changes with variation in radiation pressure and oblateness. Further, for all the ten planetary systems, studied in this paper, the Lagrangian points are unstable and can be locations where we expect to find minor planets, asteroids or debris. The unstability of the the Lagrangian points can be a possible cause of relocation and migration of planetesimals.

astro-ph.EP↗

arXiv2023

Status of Women in Astronomy: A need for advancing inclusivity and equal opportunities

Women in the Astronomy and STEM fields face systemic inequalities throughout their careers. Raising awareness, supported by detailed statistical data, represents the initial step toward closely monitoring hurdles in career progress and addressing underlying barriers to workplace equality. This, in turn, contributes to rectifying gender imbalances in STEM careers. The International Astronomical Union Women in Astronomy (IAU WiA) working group, a part of the IAU Executive Committee, is dedicated to increasing awareness of the status of women in Astronomy and supporting the aspirations of female astronomers globally. Its mission includes taking concrete actions to advance equal opportunities for both women and men in the field of astronomy. In August 2021, the IAU WiA Working Group established a new organizing committee, unveiling a comprehensive four-point plan. This plan aims to strengthen various aspects of the group's mission, encompassing: (i) Awareness Sustainability: Achieved through surveys and data collection, (ii) Training and Skill Building: Focused on professional development, (iii) Fundraising: To support key initiatives, and (iv) Communication: Dissemination of results through conferences, WG Magazines, newsletters, and more. This publication provides an overview of focused surveys that illuminate the factors influencing the careers of women in Astronomy, with a particular focus on the careers of mothers. It highlights the lack of inclusive policies, equal opportunities, and funding support for women researchers in the field. Finally, we summarize the specific initiatives undertaken by the IAU WiA Working Group to advance inclusivity and equal opportunities in Astronomy.

astro-ph.IM↗

arXiv2023

Gaps in the Main-Sequence of Star Cluster Hertzsprung Russell Diagrams

The presence of gaps or regions of small numbers of stars in the main sequence of the Hertzsprung Russell Diagram (HRD) of star clusters has been reported in literature. This is interesting and significant as it could be related to star formation and/or rapid evolution or instabilities. In this paper, using Gaia DR3 photometry and confirmed membership data, we explore the HRD of nine open clusters with reported gaps, identify them and assess their importance and spectral types.

astro-ph.SR↗

arXiv2023

Deep Photometry of Suspected Gravitational Lensing Events: Potential Detection of a Cosmic String

Cosmic strings (CS) are one-dimensional cosmological-size objects predicted in realistic models of the early Universe. Analysis of the cosmic microwave background (CMB) anisotropy data from the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck surveys revealed several CS candidates. One of the candidates, CSc-1, was found to be most reliable because of the statistically significant chains of gravitational lensing (GL) candidates in its field. We observed the brightest of the objects in the CSc-1 field, a galaxy pair SDSSJ110429.61+233150.3. The significant correlation between the spectra of the two components indicates the possible GL nature of the pair. Our simulations of observational data in the CSc-1 field shows that a large number of pairs can be explained by the complex geometry of the CS. Simulations of the SDSSJ110429 galaxy pair has shown that the observed angle between the components of the pair can be explained if the CS is strongly inclined and, possibly, bent in the image plane. In our preliminary data, we also detected the sign of the sharp isophotal edge in one image, which along with CMB and spectral data strongly suggests the possibility of a CS detection.

astro-ph.GA↗

arXiv2023

The enhanced YSO population in Serpens

The Serpens Molecular Cloud is one of the most active sites of ongoing star formation at a distance of about 300 pc, and hence is very well-suited for studies of young low-mass stars and sub-stellar objects. In this paper, for the Serpens star forming region, we find potential members of the Young Stellar Objects population from the Gaia DR3 data and study their kinematics and distribution. We compile a catalog of 656 YSOs from available catalogs ranging from X-ray to the infrared. We use this as a reference set and cross-match it to find 87 Gaia DR3 member stars to produce a control sample with revised parameters. We queried the DR3 catalog with these parameters and found 1196 stars. We then applied three different density-based machine learning algorithms (DBSCAN, OPTICS and HDBSCAN) to this sample and found potential YSOs. The three clustering algorithms identified a common set of 822 YSO members from Gaia DR3 in this region. We also classified these objects using 2MASS and WISE data to study their distribution and the progress of star formation in Serpens.

astro-ph.GA↗

arXiv2021

Starlight in Darkness: The Birth of Stars

This article will briefly review the theory of star formation (SF) and its development using observations. This is very relevant in the present context since planet formation appears to be a byproduct of SF, and the whole question of life in the universe and its origin can be viewed with a new perspective.

physics.pop-ph↗

arXiv2021

GAIA: The 3D Milky Way Mapper

GAIA (originally the acronym for Global Astrometric Interferometer for Astrophysics) is a mission of the European Space Agency (ESA) which will make the largest, most precise three dimensional map of our Galaxy by an unparalleled survey of one per cent of the galaxy's population of 100 billion stars to the precision of micro arcseconds. This article will briefly review Gaia, the data releases and the possible implications of this mission. The reader will be introduced to the DR1 and DR2 data releases and the scientific outcomes of DR1 as a forerunner to the much awaited DR2 of this one-of-a-kind mission.

physics.pop-ph↗

arXiv2021

Will Betelguese Explode?

Since October 2019, Betelgeuse began to dim noticeably and by January 2020 its brightness had dropped by a factor of approximately 2.5, demoting it from the position of the top (apparent) brightest 11 th star to the 21 st!!! Astronomers were excited and thought of it as the lull before the storm, Betelguese was ready to go supernova!!! This article is aimed more as a case study where we show how this question was answered using scientific arguments and data. It will also highlight the importance of supernovae to human existence and give a brief discussion on the evolution of massive stars. And also, answer the question!!!

physics.pop-ph↗

arXiv2021

Astronomy Data, Virtual Observatory and Education

We shall present with examples how analysis of astronomy data can be used for an educational purpose to train students in methods of data analysis, statistics, programming skills and research problems. Special reference will be made to our IAU-OAD project `Astronomy from Archival Data' where we are in the process of building a repository of instructional videos and reading material for undergraduate and postgraduate students. Virtual Observatory tools will also be discussed and applied. As this is an ongoing project, by the time of the conference we will have the projects and work done by students included in our presentation. The material produced can be freely used by the community.

physics.ed-ph↗

arXiv2021

Astronomy Education in Covid Times

We shall describe the various activities done by us in Covid Times including outreach and educational workshops in Physics and Astronomy. We shall discuss the caveats in virtual teaching of Astronomy and the lessons learnt in the process.

physics.ed-ph↗

arXiv2021

The Phosphene Controversy: Is it Phosphene? Is there life on Venus?

On 14th September 2020, the Royal Astronomical Society made an official statement coupled with a webminar on the discovery of phosphine on Venus. Single-line millimetre-waveband spectral detections of phosphine (with a signal-to-noise ratio of $\approx$ 15$\sigma$) from the JCMT and ALMA telescopes indicated a phosphine abundance of 20 ppb (parts per billion), 1000 times more than that on the Earth. Phosphine is an important biomarker and immediate speculation in the media about indicators of life being found on Venus followed. This article presents an analysis of the study and the results on the observation of the spectral absorption feature of phosphine in the clouds of Venus, thus implying as a potential biosignature. If phosphine is produced through biotic, as opposed to abiotic pathways, the discovery could imply a significant biomass in the Venusian atmosphere. The discovery led to a major controversy with criticism of the analysis and results and responses to it. The issue remains unresolved, leading to a fresh interest in the study of Venus including ground-based observations as well as space-probes that can answer these questions conclusively.

physics.pop-ph↗