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Planets Beyond the Solar System

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Planets Beyond the Solar System Understanding exoplanets in the era of large telescopes Yogesh C. Joshi Aryabhatta Research Institute of Observational Sciences (ARIES), India 1 Detection of exoplanets: Transit and Radial Velocity Method When planet passes in front of the stellar disc, it blocks light and we see a dip (loss of flux) in the light curve. 2 ΔF/F0 = (Rp/R*) When planet revolves around the star, the star wobbles and we see a variation in the radial motion. ( ⅓ 1 2G Mp sin i K = ( ⅔ 2 ½ P Ms (1 – e ) Exoplanets: present status More than 4100 exoplanets are already detected till date Planetary system close to solar system: TRAPPIST-1 4 Planetary system close to solar system: TRAPPIST-1 • TRAPPIST-1b, the innermost planet, is likely to have a rocky core, surrounded by an atmosphere much thicker than Earth's. • TRAPPIST-1c may also have a rocky interior, but with a thinner atmosphere than planet b. • TRAPPIST-1d is the lightest of the planets – about 30 percent the mass of Earth. • TRAPPIST-1e is the only planet in the system slightly denser than Earth, suggesting it may have a denser iron core than our home planet. In terms of size, density and the amount of radiation it receives from its star, this is the most similar planet to the Earth. • TRAPPIST-1f, g and h are far enough from the host star that water could be frozen as ice across their surfaces. If they have thin atmospheres, 5 they would be unlikely to contain heavy molecules of Earth, such as CO2. Exoplanetary science with large telescope High-precision photometry High-resolution spectroscopy 6 Radial Velocity through high-resolution spectroscopy HD 85512: 3.6 M⨁ transiting exoplanet Credit: ESPRESSO consortium (2018) 7 Studying the stellar rotation WASP-14b (Joshi et al. 2009) Studying the planet’s surface feature We can study dark spots in cool stars through anomaly in their transit light curves. 9 Planet passing over a dark spot and bright spot Studying the planet’s atmosphere (Transmission spectroscopy) The transit spectroscopy, a measure of atmosphere perpendicular to the line of sight as a function of λ a powerful tool for the characterization of planetary atmospheres. The wavelength dependent absorption during the primary transit is indicative of the composition of its atmosphere at the day-night terminator region such as gases, hazes, and clouds. IMAGE: EUROPEAN SOUTHERN OBSERVATORY The higher C/O abundance ratio in high-metallicity stars with planets Indicative of existence of terrestrial planets with a carbon-dominated composition Different from the composition of Earth. Studying the planet’s atmosphere Effective size of the exoplanet determines size of the transit depth – stronger absorption leads larger dips presence of high altitude clouds Optical transmission spectrum for WASP-19b through Magellan + HST observation (Espinoza et al. 2019) Atmospheric characterization of rocky planets – future science goal We have few dozens of exoplanets discovered around 10-12 mag bright nearby stars having short orbital period. These are attractive target for the detailed characterization including planet’s atmosphere through transmission spectroscopy and theoretical modelling. IRCS spectrograph on Subaru can Courtesy: Astro2020 science white paper play a significant role in studying Mass-radius relation for 418 exoplanets atmospheric compositions of these planets. 12 Few science cases with Subaru telescope ARIES perspective 13 Star formation • Detection and calculation of the mass function towards the sub-stellar mass limit is challenging. • The deep optical and infrared (IR) observations of star forming regions are needed to detect sub-stellar mass members of young clusters. • The higher spatial resolution and sensitivity of Subaru wide field Hyper Suprime-Cam (in optical) and Infrared Camera and Spectrograph (in IR) will allow individual stars to be spatially resolved, even in the dense parts the young clusters, both Galactic and extragalactic scales. • These observations will constrain the physical parameters of the individual objects and mass function of the young clusters towards lower mass end, and to understand the mechanisms responsible for the formation of the stellar/sub-stellar mass objects. • Multi-object spectroscopy with MOIRCS will be useful to obtain spectra 14 of many sub-stellar objects and determine their evolutionary stages. Dynamical study of open star clusters There are many open clusters having large angular radius. Due to dynamical mass-segregation effect, low mass stars are in the outer region of these large-size clusters. Its challenging to observe entire clusters and detect low-mass stars as well since we need observations of large sample of such clusters NGC 1960 (M36) down to their lowest-mass limit. HSC on Subaru can play a significant role to probe the dynamical history of these clusters which will put important constraints in understanding star formation and evolution 15 mechanism in the Galaxy. Gamma-ray bursts/Supernovae and follow-up • Subaru telescope is very useful for extragalactic transient sources. • As GRB host galaxies are faint and a larger aperture telescope is required to study the host galaxy morphology. • Nebular phase spectroscopy of supernovae reveals the explosion geometry as well as the properties of the progenitor star. This also provides a direct clue to the explosion mechanism giving rise to various types of Supernovae. • FOCAS, HDS and IRCS can be used for above science. • Further, HSC can be used for searching EM counterparts of 16 gravitational wave sources. Characterization of exoplanet candidates We have already discovered large number of giant exoplanets There are many earth size rocky planets too Next step is to characterize these atmosphere HDS on Subaru can be very useful Kepler-22b to study atmospheric composition Radius ~ 2.38 RE of these rocky planets through Mass ~ 36 ME transmission spectroscopy. Optical characterization and Radial velocity monitoring with Belgian and Indian Telescopes (ORBIT) 1. Confirmation and characterization of exoplanets around cool stars 2. Detection of low-mass eclipsing binaries where one component is late K or M-dwarf Follow-up work on Kepler/K2 mission archival data produced catalogues of most-likely Exoplanet candidates. We selected candidates having V<=10 mag, Porb<~5 d, Depth>0.5% + observable from Nainital/Hanle as well as La Palma We aim to confirm exoplanetary/binarity in these candidate stars using high–precision photometric and RV follow-up observations ORBIT project 19 Science with Subaru: Synergy with 3.6-m DOT • CCD Optical Imager • TIFR Near Infrared Imaging Camera-II (TIRCAM) • ARIES Faint object spectrograph and Camera (ADFOSC) • TIFR – ARIES Near-infrared Spectrometer (TANSPEC) • High resolution Optical spectrograph of ARIES (HIRA).
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