One of mankind’s most timeless questions: are we alone in the universe? Prof. Lisa Kaltenegger, astronomy, and her research team, have recently identified 1,822 stars that could potentially have orbiting planets that support life.
The stars of interest were spotted from the TESS Mission, launched back in June 2018, and could be viable candidates for having planets similar to our own.
Finding another planet resembling Earth primarily depends on how effectively astronomers can detect and characterize exoplanets, or planets that orbit stars outside our solar system.
By using powerful space telescopes, they have already made — and continue to make — progress in spotting and learning more about such exoplanets. These researchers are specifically focusing on studying rocky planets that orbit relatively closer stars to Earth.
“Generally, a planet needs to be a certain distance away from the star to not be too hot — so the oceans won’t evaporate due to the extreme heat — and not too far away from the stars, so the planet does not freeze over because it receives so little energy from its sun,” Kaltenegger said. In essence, Kaltenegger explained that, to support life, a planet must fall within the star’s habitable zone.
According to Kaltenegger, the majority of the stars from the TESS Habitable Zone Catalog are cooler, redder stars (also known as M stars) that are reasonably close to Earth and are easily observable from telescopes on Earth.
Kaltenegger and her team model the light fingerprints of planets that orbit other stars, by searching for small dips in brightness emitted from that star.
“It is easier to find [planets] around small stars because an Earth-sized planet blocks more starlight from your view if the star is small, than if the star is very big,” Kaltenegger explained. “When a planet blocks part of the hot stellar surface from our view, the star appears periodically dimmer because we don’t see all of its hot bright surface. From how much it dims, we can figure out how big the planet is compared to its star,” Kaltenegger said.
According to Kaltenegger, astronomers assess whether the studied planet is getting comparable amounts of energy from its star as the Earth receives from the Sun; this is called Earth-analog irradiation. Studying this provides insight into whether or not the environment on a particular planet is hospitable to any form of life.
Other factors that Kaltenegger’s group considers in their research include the size of a particular planet’s star and the planet’s orbit time around that star.
However, this exciting research around exoplanets does also present a few non-trivial challenges.
“In general, the big problem is that planets are very small compared to their stars,” Kaltenegger said. “But our telescopes are getting bigger to collect more light from such small dim objects.”
Additionally, to observe an exoplanet’s atmosphere from the ground, astronomers would need to take careful steps to distinguish between detectable water molecules from Earth’s own atmosphere and the actual water present in the atmosphere of the studied planet.
According to Kaltenegger, with the next generation of telescopes, such as the James Webb Space Telescope and the Extremely Large telescope, astronomers will for the first time in human history be able to spot and explore the atmosphere of other worlds that could be like ours.