A Sneak Peek At A Distant Planet's Rocky Surface

 ur starlit spiral Milky Way Galaxy is literally filled with brave new worlds--distant planets that were born to stars beyond our own Sun. Some of these planetary children of distant stars are similar to the familiar planets dwelling within our own Solar System, while others are genuine "oddballs" that are unlike anything astronomers believed could exist--that is, until they were discovered. Even though the discovery of new exoplanets has become routine, surprising revelations about their often exotic attributes still keep pouring in. In August 2019, a team of astronomers announced that they have gotten a rare sneak peek at the conditions existing on the surface of a distant rocky planet in orbit around another star. The exoplanet very likely has little, if any, atmosphere, according to data from the IRAC camera aboard NASA's infrared Spitzer Space Telescope.


This exoplanet study, published in the August 19, 2019 issue of the journal Nature, is just one of a treasure trove of nearly 700 publications using IRAC since 2009. This is when Spitzer's Warm Mission began, and IRAC became its only operating instrument. The IRAC camera's team is based at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, and is led by Dr. Giovanni Fazio.


The distant rocky planet, named LHS 3844b, may also be well-coated with the same cooled volcanic material that creates the dark lunar regions known as mare (Latin for sea). This means that the exoplanet might be similar to Mercury, or to Earth's Moon.


LHS 3844b was discovered in 2018 by NASA's Transiting Exoplanet Satellite Survey (TESS) mission. It is located 48.6 light-years from Earth, and has a radius 1.3 times that of our own planet. It orbits a small, cool type of star called an M dwarf. This is especially important because, as one of the most common and long-lived types of stars in our Galaxy, M dwarfs may be the stellar parents of a high percentage of the total number of planets in our Milky Way. The smaller the star, the longer its "life" on the hydrogen-burnng main-sequence of the Herttzsprung-Russell Diagram. This is because relatively cool stars burn their supply of hydrogen fuel more slowly than their much hotter and more massive stellar kin, who "live" fast, and "die" young.


TESS discovered the remote rocky world using the transit method. This method spots the existence of an exoplanet when it floats in front of the glaring face of its parent star, thus dimming its light across the line-of-sight between the star and Earth.


During follow-up observations, IRAC detected light originating from the surface of LHS 3844b. The planet completes one full orbit around its stellar parent in only 11 hours. With such a close-in orbit to the searing-hot surface of its star, LHS 3844b is probably "tidally locked" with one side of the planet perpetually facing its star. The star-facing side, referred to as the "dayside", is approximately a roasting 1,410 degrees Fahrenheit. Being quite hot, the planet radiates an abundant amount of infrared light which IRAC, an infrared camera, is capable of measuring. This observation is important because it marks the first time IRAC data have been able to provide information about the atmosphere of a terrestrial-sized alien world in orbit around an M dwarf star.





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