Tuesday, June 6, 2017

Is Exoplanet LHS 1140b the Best Place to Search for Alien Life?

This artist’s impression shows the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth and may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Credit: ESO/spaceengine.org

Located just 40 light years away from our solar system, an extrasolar world named LHS 1140b, could the holy grail for alien life hunters. This rocky planet, slightly larger than Earth, is currently considered as the most possible location for extraterrestrial life.

Discovered in April 2017, LHS 1140b is a so-called “super-Earth” - a planet with a mass higher than Earth's, but below the masses of Uranus and Neptune. The newly detected exoworld has a mass of about 6.6 Earth masses and a radius of 1.4 Earth radii. LHS 1140b orbits a small, cool star (LHS 1140) approximately every 25 days at a distance of nearly 0.09 AU - just in the middle of the habitable zone.

Best candidates to search for alien life are planets with liquid surface water and possessing an atmosphere. According to astronomers, LHS 1140b receives similar amounts of energy from its star that Earth does from the Sun, which means it may have liquid water on its surface. Moreover, given its large surface gravity and cool insolation, LHS 1140b may have retained its atmosphere despite the greater luminosity (compared to the present day) of its host star in its youth.

“The star LHS 1140 is very inactive - we have not seen the star flare while we have been monitoring it. In contrast, the habitable-zone planets around Proxima Centauri, the nearest star and TRAPPIST-1 receive a lot of high energy radiation from their host stars. This may affect their ability to retain an atmosphere and of course could damage organisms on the surface,” Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics, lead author of the paper detailing the discovery of LHS 1140b, told Astrowatch.net.

Dittmann added that LHS 1140b is composed of things similar in density to that which the Earth is made of.

“This contrasts with Proxima Centauri b, which we do not know the orbital inclination for (and therefore only have a minimum mass), and the TRAPPIST-1 planets, which recent work has shown that they are actually unlikely to be rocky planets and probably more like the icy moons of Jupiter or Saturn,” he said.

Given the fact that LHS 1140b is similar in size to Earth but several times more massive than our planet, it has a very high density. This means that this exoplanet is probably made of rock and has a dense iron core.

While the planet’s basic parameters have been already estimated, it is now important for astronomers to search for the signs of an atmosphere on this alien world. Therefore Dittmann and his colleagues plan to observe LHS 1140b using every available telescope.

“Discovering the planet is just the beginning. Our plan right now is to hit it with everything we have. We have put in proposals with the Hubble Space Telescope to maybe hopefully detect the first hint of its atmosphere. The first of these proposals was accepted and we're starting to get data, and we're waiting to hear back on the others. We have also asked for time with NASA’s Chandra X-ray Observatory in order to see exactly how strong the star emits at X-rays. Moreover, we have also put in a proposal to look for additional planets in the system with NASA’s Spitzer Space Telescope as well as for possible signs of exomoons around LHS 1140b as well,” Dittmann revealed.

In the future the astronomers plan to observe LHS 1140b with the powerful James Webb Space Telescope (JWST) slated to be launched into space in October 2018. JWST has everything it takes to revolutionize our understanding of exoplanet atmospheres. It is a huge telescope sensitive at wavelengths where a lot of molecules can show features. JWST will be able to find things like water, methane, ozone, and carbon dioxide.

The researchers also want to study LHS 1140b using large ground-based optical observatories currently under construction like the Giant Magellan Telescope (GMT) and the Extremely Large Telescope (ELT), with the hope of detecting what may be in the planet’s atmosphere, including molecular oxygen. What is noteworthy, molecular oxygen has strong features in optical wavelengths, which is where the 30-meter ground based telescopes come in. Luckily the star is bright enough at optical (unlike the TRAPPIST-1 system) where this is feasible to do. Therefore, Dittmann and his team think that they can possibly detect signs of molecular oxygen in the LHS 1140b system.

However, the most important question now is could these future observations confirm the presence of life on this nearby exoworld?

“As for what signs of life looks like, we do not really know. Most things we can think of can also be produced through other means as well. So this is going to be a long debate between a lot of people for a while about what detection of life might actually look like. I think oxygen is going to be important, but not sufficient on its own. Beyond that, we will have to look for other things, maybe methane. But again, this is going to be a subject of intense study for a while,” Dittmann concluded.

No comments:

Post a Comment