The name is LHS 1140b. It’s a rocky planet just like Earth. It’s located just 40 light years away. David Charbonneau of the Harvard-Smithsonian Center for Astrophysics said if the Milky Way galaxy were the size of the United States, the LHS 1140b and the Earth would both fit inside the Central Park. Scientists said this exoplanet was the most promising candidate to look for the possibility of alien life outside our solar system.
It’s in the Goldilocks zone of a red dwarf star
Jason Dittmann and his colleagues described the findings of their study Thursday in the journal Nature. The planet orbits a red dwarf star called LHS 1140 every 25 days. It is in the so-called Goldilocks zone of its parent star, meaning its temperature is just right to have liquid water on the planet’s surface. There are many other exoplanets that are in the habitable zone of their parent stars, but the newly discovered super-Earth is our best bet because of the type of star it orbits and its orientation to Earth.
Jason Dittmann, the lead author of the study, said it was the most exciting exoplanet discovery in nearly a decade. The exoplanet was discovered using the MEarth-South survey in Chile and the European Southern Observatory (ESO)’s HARPS instrument. Astronomers look for subtle dips in the brightness of a star to find an exoplanet that passes in front of it. The LHS 1140b causes the light from its host star to dim a little every 25 days.
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The rocky exoplanet has retained its atmosphere
Astronomers found that this planet is 1.4 times the diameter of our Earth, and 6.6 times the mass of our planet. Its mass suggests that the planet is rocky. Scientists estimate that the planet is about five billion years old. The host star LHS 1140 is only about one-fifth the size of our sun. In its close orbit, the exoplanet receives only 0.46 times as much light from its host star as the Earth gets from the sun. Astronomers believe that the planet has retained most of its atmosphere.
Scientists are now trying to examine the planet’s atmosphere, which could offer clues about the possibility of life and signs about whether life already exists there. Starlight passing through the planet’s atmosphere could reveal details about the chemical composition of its atmosphere. The exoplanet’s density can also tell you how tightly it holds on to its atmosphere.
Testing an existing theory
The biggest reason scientists are enthusiastic about the exoplanet is the type of star it orbits. The star LHS 1140 is very different from our sun. It is an M dwarf (or red dwarf) star. Red dwarfs are significantly smaller and cooler than our sun. Since they are cooler and dimmer, astronomers can study the planets orbiting them in great detail. Studying planets close to a bright star is incredibly difficult.
Not too long ago, planets orbiting the red dwarfs did not interest scientists because they were mostly tidally locked. It means one side of the planet always faced the host star while the other side was always in the dark. More recently, scientists theorized that if these planets have thick atmospheres, the winds could easily distribute the heat, making both hemispheres livable.
The LHS 1140b offers a great opportunity to test that proposition. Also, the M dwarfs are one of the most common types of stars in our galaxy. The newly discovered exoplanet would help scientists figure out whether planets orbiting such stars have the possibility of life.
Red dwarfs can damage an orbiting planet’s atmosphere
The red dwarfs are violent in their early lives, bombarding UV radiation and X-rays on planets in close orbit. They could potentially damage the atmosphere, evaporate liquid water, or even kill the early life forms. Fortunately, scientists said the exoplanet LHS 1140b is heavy enough to be able to retain its atmosphere or regenerate it later on through volcanic activities.
For now, astronomers plan to use the Hubble Space Telescope to collect data on its atmosphere. But it can be studied in great detail only when the next-generation of large telescopes such as the James Webb Space Telescope, set to launch next year, the Thirty Meter Telescope, and the Giant Magellan Telescope come online.