Astronomers Discover Three Potentially Habitable Worlds

Three Potentially Habitable Worlds Found Around Nearby Ultracool Dwarf Star

This artist’s impression shows an imagined view from the surface one of the three planets orbiting an ultracool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO’s La Silla Observatory. These worlds have sizes and temperatures similar to those of Venus and Earth and are the best targets found so far for the search for life outside the Solar System. They are the first planets ever discovered around such a tiny and dim star.

Astronomers have discovered three planets with sizes and temperatures similar to those of Venus and Earth, orbiting an ultra-cool dwarf star just 40 light-years from Earth.

Astronomers using the TRAPPIST telescope at ESO’s La Silla Observatory have discovered three planets orbiting an ultracool dwarf star just 40 light-years from Earth. These worlds have sizes and temperatures similar to those of Venus and Earth and are the best targets found so far for the search for life outside the Solar System. They are the first planets ever discovered around such a tiny and dim star. The new results are published in the journal Nature.

A team of astronomers led by Michaël Gillon, of the Institut d’Astrophysique et Géophysique at the University of Liège in Belgium, have used the Belgian TRAPPIST telescope to observe the star 2MASS J23062928-0502285, now also known as TRAPPIST-1. They found that this dim and cool star faded slightly at regular intervals, indicating that several objects were passing between the star and the Earth. Detailed analysis showed that three planets with similar sizes to the Earth were present.

TRAPPIST-1 is an ultracool dwarf star — it is much cooler and redder than the Sun and barely larger than Jupiter. Such stars are both very common in the Milky Way and very long-lived, but this is the first time that planets have been found around one of them. Despite being so close to the Earth, this star is too dim and too red to be seen with the naked eye or even visually with a large amateur telescope. It lies in the constellation of Aquarius (The Water Carrier).

Emmanuël Jehin, a co-author of the new study, is excited: “This really is a paradigm shift with regards to the planet population and the path towards finding life in the Universe. So far, the existence of such ‘red worlds’ orbiting ultra-cool dwarf stars was purely theoretical, but now we have not just one lonely planet around such a faint red star but a complete system of three planets!”

Michaël Gillon, lead author of the paper presenting the discovery, explains the significance of the new findings: “Why are we trying to detect Earth-like planets around the smallest and coolest stars in the solar neighborhood? The reason is simple: systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology. So if we want to find life elsewhere in the Universe, this is where we should start to look.”

Astronomers will search for signs of life by studying the effect that the atmosphere of a transiting planet has on the light reaching Earth. For Earth-sized planets orbiting most stars, this tiny effect is swamped by the brilliance of the starlight. Only in the case of faint red ultra-cool dwarf stars — like TRAPPIST-1 — is this effect big enough to be detected.

Follow-up observations with larger telescopes, including the HAWK-I instrument on ESO’s 8-meter Very Large Telescope in Chile, have shown that the planets orbiting TRAPPIST-1 have sizes very similar to that of Earth. Two of the planets have orbital periods of about 1.5 days and 2.4 days respectively, and the third planet has a less well-determined period in the range of 4.5 to 73 days.

“With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun. The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the Solar System,” explains Michaël Gillon.

Although they orbit very close to their host dwarf star, the inner two planets only receive four times and twice, respectively, the amount of radiation received by the Earth, because their star is much fainter than the Sun. That puts them closer to the star than the habitable zone for this system, although it is still possible that they possess habitable regions on their surfaces. The third, outer, planet’s orbit is not yet well known, but it probably receives less radiation than the Earth does, but maybe still enough to lie within the habitable zone.

“Thanks to several giant telescopes currently under construction, including ESO’s E-ELT and the NASA/ESA/CSA James Webb Space Telescope due to launch in 2018, we will soon be able to study the atmospheric composition of these planets and explore them first for water, then for traces of biological activity. That’s a giant step in the search for life in the Universe,” concludes Julien de Wit, a co-author from the Massachusetts Institute of Technology (MIT) in the USA.

This work opens up a new direction for exoplanet hunting, as around 15% of the stars near to the Sun are ultra-cool dwarf stars, and it also serves to highlight that the search for exoplanets has now entered the realm of potentially habitable cousins of the Earth. The TRAPPIST survey is a prototype for a more ambitious project called SPECULOOS that will be installed at ESO’s Paranal Observatory.

Reference: “Temperate Earth-sized planets transiting a nearby ultracool dwarf star” by Michaël Gillon, Emmanuël Jehin, Susan M. Lederer, Laetitia Delrez, Julien de Wit, Artem Burdanov, Valérie Van Grootel, Adam J. Burgasser, Amaury H. M. J. Triaud, Cyrielle Opitom, Brice-Olivier Demory, Devendra K. Sahu, Daniella Bardalez Gagliuffi, Pierre Magain and Didier Queloz, 2 May 2016, Nature.
DOI: 10.1038/nature17448

5 Comments on "Astronomers Discover Three Potentially Habitable Worlds"

  1. Husein Kattab | May 4, 2016 at 11:36 am | Reply

    I believe that scientists should reconsider the ongoing asdumption that brown or red dwarfs seize to grow or evolve. As long as there is mayerial in the vecinity then they will keep growing and evolve into g class stars.


  2. Harold W Miller | May 4, 2016 at 3:33 pm | Reply

    An M8 star will exist ten trillion years before it uses all its fuel. Even then it won’t go through a “red giant” phase but will slow heat up until it’s blue then fade into a black dwarf. During its lifetime, it will probably accumulate interstellar gas and dust. Unless it’s hydrogen the dust will settle to its core and will stay there until the little star is completely converted to helium. However, while that process will change its composition somewhat, it will neve accumulate enough gas to become a K or G star.

    • What you just wrote is your theory. I can make up plausible theories. However I found nothing you said worth thinking about twice. Which makes it hogwash.

  3. Dylan Collins | May 5, 2016 at 9:42 pm | Reply

    We need to send out radio signals in that direction. It would take roughly 80 years to hear back from any form of intelligent life, but it would be interesting.

    • As we are listening in all directions 24/7 here on earth right?
      What makes you think any intelligent life (if there is any on those worlds) would listen for 24/7 in all directions?
      They can’t be that bored, can they?

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