Astronomy

Marvel at the Variety of Planets Found by TESS Already

The hunt for new exoplanets continues. On May 23rd, an international collaboration of scientists published the NASA TESS-Keck Catalog, an effort to publicly release over 9000 radial velocity measurements collected by NASA’s space-based Transiting Exoplanet Survey Satellite (TESS) and the ground-based Keck Observatory, located in Hawai’i, and the Automated Planet Finder, located at the Lick Observatory in California. An accompanying analysis of these validated 32 new planetary candidates and found the masses of 126 confirmed planets and candidates with a wide range of masses and orbits. Let’s dig into some details.

Radial velocity (RV) measurements are a backbone of exoplanet hunting. Telescopes collect data on how a star “wobbles” by checking for a red-shift (if it’s moving toward the Earth) or blue-shift (if it’s moving away) based on the gravitational pull of an exoplanet orbiting it. If the data presents a repeating pattern, the scientists know they have a likely exoplanet candidate on their hands.

To calculate the planet’s rotational period, scientists use the frequency of the changes in light from the star. They can estimate a planet’s orbital period based on how quickly the star cycles through the red and blue shifts they would expect from a complete planetary orbit. Unfortunately, since telescope time is limited, most of the exoplanets found so far using this method have much shorter orbital periods than the Earth.

Fraser discusses the end of TESS’s first mission.

Calculating a planet’s mass is also possible using the RV method – simply by calculating the planet’s gravitational pull as it is either directly behind or in front of the star. The magnitude of the respective red or blue shift can be directly tied to the planet’s mass, causing the gravitational pull.

Some truly unique worlds are hiding in the data, with two that stood out enough to be mentioned in a press release from the Keck Observatory. One is an overweight version of a “sub-Neptune”,” while another is a rapidly orbiting “super-Earth”.” 

A “sub-Neptune” is a category of planet that is a gas giant slightly smaller than Neptune, the smallest gas giant in our solar system. A planet known as TOI-1824 falls into this category but has a unique weight – it’s 19 times as massive as Earth despite being only about 2.6 times its size. That is an extremely dense planet and well outside of the range of other typical sub-Neptunes, which typically vary between 6 and 12 times the mass of our own planet.

TESS has had plenty of data updates over its lifetime – Fraser discusses one here.

A planet in the dataset that is closer in size to our own is TOI-1798c. From the mass perspective, it’s about the same size as Earth. However, it is so close to its parent’s star that it orbits it every 12 hours. This puts it in the category of an “Ultra-short period” (USP) orbit. Typically, USPs are tidally locked to their star and blasted with massive amounts of radiation. Estimates put the solar radiation it receives from its host star at 3000 times that received by the Earth. It doesn’t sound like an enjoyable vacation spot.

Doubtless, other exoplanets are hiding in the trove of data released as part of this paper. And each of those unique systems warranted their own published paper as well. As humanity begins to collect more and more discovered exoplanets, more strange and exciting new worlds will be found. It’s a crazy galaxy out there, and we’re only just starting to explore it.

Learn More:
Keck Observatory – New Catalog Showcases a Diverse Exoplanet Landscape with Strange, Exotic Worlds
Polanski et al. – The TESS-Keck Survey. XX. 15 New TESS Planets and a Uniform RV Analysis of All Survey Targets
UT – TESS Has Found Thousands of Possible Exoplanets. Which Ones Should JWST Study?
UT – Six Planets Found Orbiting an Extremely Young Star

Lead Image:
Artist’s rendering of some of the exoplanets contained in the TESS-Keck Catalog.
Credit – W. M. Keck Observatory / Adam Makarneko

Andy Tomaswick

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