March 23, 2023

Looking into the potential for life around the galaxy’s smallest star

The superstar at the center of the study is an M-dwarf called D 98-59, which measures just 8% of our sun’s mass

Once the world’s most powerful telescope roll-outs into space this year, researchers will learn whether Earth-sized exoplanets in our ‘ solar neighborhood’ have a key prerequisite to get life— an atmosphere.

These  planets   orbit an M-dwarf, the smallest and many common type of star within the galaxy. Scientists do not currently know how common it is just for Earth-like planets around this kind of star to have characteristics that could make them habitable.

“ As a starting place, it is very important know whether small, rocky planets orbiting M-dwarfs possess atmospheres, ” said Daria Pidhorodetska, a doctoral pupil in UC Riverside’s Division of Earth and Planetary Sciences. “ If so, this opens up our search for existence outside our solar system. ”

To assist fill this gap within understanding, Pidhorodetska and her team studied whether the soon-to-launch James Webb Space Telescope, or the currently-in-orbit Hubble Room Telescope, are capable of detecting atmospheres on these planets. Additionally they modeled the types of atmospheres likely to be found, if they exist, and how they could be distinguished through each other. The study has now already been published in the  Astronomical Journal .

Study co-authors include astrobiologists Edward Schwieterman plus Stephen Kane from UCR, as well as scientists from Johns Hopkins University, NASA’s Goddard Space Flight Center, Cornell University and the University associated with Chicago.

The star at the center of the study is an M-dwarf known as L 98-59, which actions only 8% of our sun’s mass. Though small, it is only 35 light years from Earth. It’s brightness and relative closeness ensure it is an ideal target for statement.

Shortly after these people form, M-dwarfs go through the phase in which they can sparkle two orders of magnitude brighter than normal. Solid uaviolet radiation during this stage has the potential to dry out their orbiting planets, evaporating any water from the surface and destroying many gases in the  atmosphere .

“ We wanted to know when the ablation was complete regarding the two rocky planets, or even if those terrestrial sides were able to replenish their atmospheres, ” Pidhorodetska said.

The researchers patterned four different atmospheric situations: one in which the L 98-59 worlds are dominated by water, one in which the environment is mainly composed of hydrogen, a Venus-like carbon dioxide atmosphere, and another in which the hydrogen in the environment escaped into space, leaving behind only oxygen and ozone.

They found that the two telescopes could offer complementary information making use of transit observations, which calculate a dip in light that develops as a planet passes before its star. The T 98-59 planets are much nearer to their star than Planet is to the sun. They total their orbits in less than per week, making transit observations simply by telescope faster and more cost effective than observing other systems where the planets are farther from their  stars .

“ It will only take a few transits with Hubble to detect or rule out a hydrogen- or steam-dominated atmosphere with out clouds, ” Schwieterman said. “ With as few as twenty transits, Webb would allow us to characterize gases within heavy carbon dioxide or oxygen-dominated atmospheres. ”

Of the four atmospheric scenarios the researchers considered, Pidhorodetska said the dried-out oxygen-dominated atmosphere is the most likely.

“ The amount of radiation these planets are getting from that distance from the star is intense, ” she said.

Even though they may not have atmospheres that will lend themselves to life these days, these planets can offer a significant glimpse into what might happen to Earth under various conditions, and what might be possible on Earth-like worlds somewhere else in the galaxy.

The L 98-59 system was only discovered in 2019, and Pidhorodetska said she is excited to get more information about this when Webb is released later this year.

“ We’re on the precipice of revealing the secrets of a star system that was hidden until very lately, ” Pidhorodetska said.

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