About Me

This is me!

Hi! Thank you for visiting my webpage.

I'm a Ph.D. Candidate in the Department of Earth, Planetary, and Space Sciences at the University of California, Los Angeles (UCLA). At UCLA, I work with Dr. Hilke Schlichting on topics entailing formation and evolution of small exoplanets. I started my PhD program in 2017 and received an MS in Planetary Science (Geophysics & Space Physics) in Summer 2019.

In 2016, I graduated from the Indian Institute of Technology (IIT), Kanpur with a Bachelor's and Master's (Dual degree) in Aerospace Engineering. For my Master's thesis, I worked on the dynamics of rings around non-spherical bodies under the supervision of Dr. Ishan Sharma and Dr. Sharvari Nadkarni-Ghosh. Furthermore, I even worked on projects encompassing planetary rings, orbital dynamics, N-body simulations, kinetic/granular theory and designing & building Formula-One prototype cars.

To know about my research, please visit the 'Research' or 'Publications' section. For other details, you may access my CV or visit the 'Contact' section to know how we could get in touch.

Research

Horizon

My general research interests revolve around the formation, evolution, interiors and dynamics of planetary bodies (extra-solar and solar). Below I list my present and past research projects which can be classified into the following broad categories:

  • Formation and evolution of planetary bodies

    -- Origin of supear-Earths and sub-Neptunes: Understanding the radius valley as a by-product of planet formation
    -- Understanding the evolution of early Moon

  • N-body simulations and planetary ring dynamics

    -- Rings around small, non-spherical planetary bodies
    -- Saturn's F-ring: dynamics under continual formation and disruption of aggregates

  • Dynamics, impacts and craters

    -- Investigating the observed asymmetry in the distribution of Lunar cold-spots

  • Other major projects

    -- Adaptively optimized trajectories for rendezvous with an asteroid
    -- Formula SAE, Italy'13 by SAE International (IITK Motorsports)


  • Origin of super-Earths and sub-Neptunes: Understanding the radius valley as a by-product of planet formation under the core-powered mass-loss mechanism



    A video explaining how the radius valley can be understood as a by-product of planet formation under the core-powered mass-loss mechanism. Credits: Emilie Eshbaugh (UCLA undergraduate student) and Hilke Schlichting.



    The video above by Emilie Eshbaugh (UCLA) gives a great explanation and introduction to this project. If you prefer a textual summary and would like further details, please read below or refer Ginzburg et al. 2018 and Gupta & Schlichting (2019, 2020).

    Till 1995, we only knew about the eight planets in our Solar system. Since, we have discovered thousands of planets in our galaxy orbiting other stars, i.e. exoplanets (4031 as of Aug 1 2019; see NASA Exoplanet Archive). These discoveries have revolutionized the field of exoplanetary science and offer new insights into the formation and evolution of planets.

    One of the key findings from recent observations has been that the abundant planets in our galactic neighborhood, to-date, are 1 to 4 Earth radii in size, i.e. larger than Earth and smaller than Neptune. Intriguingly, further observations have revealed that there is a lack of planets of sizes 1.5 - 2.0 Earth radii, i.e. a radius 'valley', in the size distribution of such small, short-period (<100 days) exoplanets. Moreover, a transition in planet density has been noted around ~1.6 Earth radii, with smaller planets having higher bulk densities, consistent with rocky Earth-like compositions while larger planets having lower bulk densities, suggesting that these planets are engulfed in H/He atmospheres. It has thus been suggested that this valley likely marks a transition regime between smaller rocky planets, i.e. 'super-Earths' to larger planets with significant atmospheres, i.e. 'sub-Neptunes'.

    Observed planet size distribution

    Radius valley in the distribution of small, close-in planets separating populations of super-Earths and sub-Neptunes. Plot based on data from Fulton et al. 2017.

    Typically, atmospheric erosion due to high-energy radiation from the host stars, i.e. photoevaporation, is suggested as an explanation to these observations. Recently, however, Ginzburg et al. 2018 and my advisor and I (Gupta & Schlichting 2019, 2020) have demonstrated that atmospheric loss due to a planet's own cooling luminosity, i.e. core-powered mass-loss, can also explain the observed radius valley, even without photoevaporation. Furthermore, we have demonstrated that planetary evolution under this mechanism can explain a multitude of trends observed in the planet size distribution with orbital period, insolation flux and stellar mass, metallicity, age (Gupta & Schlichting, 2020).

    Figure 1, Gupta & Schlichting 2019, MNRAS

    Schematic demonstrating how the core-powered mass-loss mechanism results in super-Earths and sub-Neptunes and thus the radius valley. See Gupta & Schlichting, 2019 for details.

    It is likely that the observed planet distribution was not just sculpted by core-powered mass-loss and photoevaporation, but by a multitude of processes over their lifetime such as giant impacts or different planet formation pathways (icy planets, formation in gas depleted disks or after dispersal of gas disks). Nevertheless, our work shows that the valley in the size distribution of exoplanets is an inevitable by-product of the planetary formation process, i.e. through the core-powered mass-loss mechanism.

    To know more, please refer:
    A. Gupta & H.E. Schlichting, 2020. MNRAS. Accepted. [ADS] [arXiv]
    A. Gupta & H.E. Schlichting, 2019. MNRAS 487, 24-33. [ADS] [arXiv]

  • Rings around small, non-spherical planetary bodies

    Haumea and its rings

    Artistic rendition of the triaxial shaped dwarf planet Haumea with its surrounding ring. Image credit: Wikipedia user 'Tomruen'.

    For years, we have known of the rings around the giant planets of our Solar System. Rings are also expected to exist around extrasolar planets but have not been detected so far. However, what was not expected was the existence of rings around much smaller, non-spherical bodies of our Solar System. This changed in 2014 with the discovery of rings around a small body named Chariklo, followed by another discovery in 2017, of rings around the dwarf planet, Haumea. These discoveries suggest that the ring systems are much more common in our Solar System than previously thought, and their existence has challenged our understanding of their evolution and formation.

    In collaboration with my former group from IIT Kanpur (Dr. Ishan Sharma, Dr. Sharvari Nadkarni-Ghosh, Shri B. Bharath and others), I have been trying to understand the dynamics of rings around non-spherical bodies through N-body simulations.

    To know more, please refer:
    A. Gupta, S. Nadkarni-Ghosh & I. Sharma, 2018. Icarus 299, 97-116. [ADS][arXiv]

  • Investigating the observed asymmetry in the distribution of Lunar cold-spots

    Moon

    The cratered surface of the moon. Image credit: Lunar Reconnaissance Orbiter.

    We have known for some time that our Moon has a spatial (longitudinal and latitudinal) asymmetry in the distribution of craters. This asymmetry is due to our Moon's synchronous motion around Earth and is also observed around other natural satellites like in the Galilean system. Since these observations, this problem has been investigated and explained using analytical, semi-empirical and numerical models.

    However, recent observations of the distribution of lunar 'cold-spot' craters by the Lunar Reconnaissance Orbiter (LRO) have revealed that their longitudinal asymmetry is higher than that previously observed. These 'cold-spot' craters are the recently formed lunar craters which show distinctly low night-time temperatures around them thus allowing them to be observed by LRO's thermal instruments. These are estimated to be a million years old or younger and to have sizes between ~ 50 - 2000 m -- much younger and smaller than the craters observed previously. Therefore, this discrepancy in the distribution of cold-spot craters raises questions, for example, about the assumptions and inferences made by the previous studies when investigating the older observations regarding the impactor size distribution or the source of these craters.

    Through this project, we are trying to answer such questions. While I was leading this project in its earlier stages, it is currently being led by Sophia Turner who is a senior-year undergrad at UCLA.

  • Saturn's F-ring: dynamics under continual formation and disruption of aggregates

    Saturn's F ring

    Cassini image shows Saturn's potato-shaped moon, Prometheus, dynamically and physically interacting with the F-ring. Image credit: NASA/JPL/Space Science Institute.

    Saturn's F-ring is one of the most beautiful and dynamically active systems in our Solar system. This is due to the continual formation and disruption of aggregates in this ring which is because it is located near Saturn's Roche limit. Under Prof. Heikki Salo's (University of Oulu, FI) guidance, who is an expert on numerical simulations of planetary rings, I investigated the dynamics of this ring system using N-body simulations and also the mechanism of confinement in rings due to the shepherding satellites.

  • Other Major Projects

    ISS

    ISS Composite Star Trail Image. Image credit: NASA on The Commons - flickr.

    Adaptively optimized trajectories for rendezvous with an asteroid
    Formula SAE, Italy'13 by SAE International (IITK Motorsports)

Top Panel: Earth's horizon and ESA Johannes Kepler ATV. Image Credit: NASA on the Commons - flickr

Contact

Planets by Anneka Tran

If you have any questions, comments or suggestions regarding my work and publications or would like to collaborate, please do get in touch. I’d love to hear from you!

Email

akashgpt [at] ucla.edu, akashgpt.ucla [at] gmail.com

Address

Room 4642, Geology Building
Department of Earth, Planetary, and Space Sciences
University of California, Los Angeles
595 Charles Young Drive East,
Los Angeles, CA 90095-1567, USA.


Image Credit: Anneka Tran

Publications

ALMA images
  • Peer-Reviewed Publications



  • Seminars and Conference Talks & Posters



  • Saturn's icy moon Enceladus. Image Credit: NASA/JPL/Space Science Institute