7 Earth-sized planets orbiting nearby star discover by Astronomers

seven-planet-extrasolar-system-discoveredAstronomers have found at least seven Earth-sized planets orbiting the same star 40 light-years away, according to a study published Wednesday in the journal Nature. The findings were also announced at a news conference at NASA Headquarters in Washington. This discovery outside of our solar system is rare because the planets have the winning combination of being similar in size to Earth and being all temperate, meaning they could have water on their surfaces and potentially support life.


 “This is the first time that so many planets of this kind are found around the same star,” said Michaël Gillon, lead study author and astronomer at the University of Liège in Belgium.

The seven exoplanets were all found in tight formation around an ultracool dwarf star called TRAPPIST-1. Estimates of their mass also indicate that they are rocky planets, rather than being gaseous like Jupiter. Three planets are in the habitable zone of the star, known as TRAPPIST-1e, f and g, and may even have oceans on the surface.
The TRAPPIST-1 star, an ultracool dwarf, has seven Earth-size planets orbiting it.

The TRAPPIST-1 star, an ultracool dwarf, has seven Earth-size planets orbiting it.

  • The researchers believe that TRAPPIST-1f in particular is the best candidate for supporting life. It’s a bit cooler than Earth, but could be suitable with the right atmosphere and enough greenhouse gases.
  • TRAPPIST-1 doesn’t put out much energy, but the inner six exoplanets are in such tight orbit around their host that they have temperatures comparable to those on Venus, Earth, and Mars.

trappist-1-planetary-system

  • The scientists observations and measurements suggest the inner six planets have rocky compositions, and that three of TRAPPIST-1’s surrounding bodies may orbit within a habitable zone that represents the “holy grail for planet-hunting” as they could be warm enough to host surface water and oceans.
  • The team believes this discovery could mean that similar dwarf stars are able to host Earth-sized planets in tight orbits, making them “promising targets” in the search for extraterrestrial life.
  • If TRAPPIST-1 sounds familiar, that’s because these researchers announced the discovery of three initial planets orbiting the same star in May. The new research increased that number to seven planets total.

What we know?

The planets are so close to each other and the star that there are seven of them within a space five times smaller than the distance from Mercury to our sun. This proximity allows the researchers to study the planets in depth as well, gaining insight about planetary systems other than our own.
The seven planets of TRAPPIST-1 compared with Mercury, Venus, Earth and Mars.

The seven planets of TRAPPIST-1 compared with Mercury, Venus, Earth and Mars.

  • Starting closest to the star and moving out, the planets have respective orbits from one and a half to nearly 13 Earth days. The orbit of the farthest planet is still unknown.
  • Standing on the surface of one of the planets, you would receive 200 times less light than you get from the sun, but you would still receive just as much energy to keep you warm since the star is so close. It would also afford some picturesque views, as the other planets would appear in the sky as big as the moon (or even twice as big).
  • On TRAPPIST-1f, the star would appear three times as big as the sun in our sky. And because of the red nature of the star, the light would be a salmon hue, the researchers speculate.
  • The researchers believe the planets formed together further from the star. Then, they moved into their current lineup. This is incredibly similar Jupiter and its Galilean moons.
2300-trappistsystem0222-web-v2

These new Earth-size planets orbit a dwarf star named Trappist-1 about 40 light years from Earth. Some of them could have water on their surfaces.

  • Like the moon, the researchers believe the planets closest to the star are tidally locked. This means that the planets always face one way to the star. One side of the planet is perpetually night, while the other is always day.
  • Based on preliminary climate modeling, the researchers believe that the three planets closest to the star may be too warm to support liquid water, while the outermost planet, TRAPPIST-1h, is probably too distant and cold to support water on the surface. But further observation is needed to know for sure.

How the discovery was made

TRAnsiting Planets and PlanetesImals Small Telescope–South One of the observing domes of La Silla Observatory

TRAnsiting Planets and PlanetesImals Small Telescope–South One of the observing domes of La Silla Observatory

  • TRAPPIST-1 barely classifies as a star at half the temperature and a tenth the mass of the sun. It is red, dim and just a bit larger than Jupiter. But these tiny ultracool dwarf stars are common in our galaxy. They were largely overlooked until Gillon decided to study the space around one of these dwarfs.
  • The researchers used a telescope called TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) to observe its starlight and changes in brightness. The team saw shadows, like little eclipses, periodically interrupting the steady pattern of starlight. This is called transiting. The shadows indicated planets, and further observation confirmed them.
  • In July, the team was able to determine that two of the closest planets to the stars had atmospheres that were more compact and comparable to those of Earth, Venus and Mars by observing starlight through the planets’ atmosphere.
  • In July, the team was able to determine that two of the closest planets to the stars had atmospheres that were more compact and comparable to those of Earth, Venus and Mars by observing starlight through the planets’ atmosphere.

 Looking for Next

  • By using a global network ground-based telescopes like TRAPPIST and space-based telescopes like Spitzer, the researchers continued looking toward the TRAPPIST system and were able to determine the orbital periods, distances from their star, radius and and masses of the planets.

finding-planets-with-microlensing

  • In 2018, the James Webb Space Telescope will launch and be positioned 1 million miles from Earth with an unprecedented view of the universe. It can observe large exoplanets and detect starlight filtered through their atmosphere.
  • The researchers are also searching for similar star systems to conduct more atmospheric research. Four telescopes named SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) based in Chile will survey the southern sky for this purpose.
  • This star system will probably outlive us because this type of star evolves so slowly. When our sun dies, TRAPPIST-1 will still be a young star and will live for another trillion years, Gillon said. After we are gone, if there is another part of the universe for life to carry on, it may be in the TRAPPIST-1 system.
  • “This is the most exciting result I have seen in the 14 years of Spitzer operations,” said Sean Carey, manager of NASA’s Spitzer Science Center at Caltech/IPAC in Pasadena, California. “Spitzer will follow up in the fall to further refine our understanding of these planets so that the James Webb Space Telescope can follow up. More observations of the system are sure to reveal more secrets.”

Habitable Exoplanet

kepler-findings

  • While this discovery was made using the Spitzer Space Telescope, one of the most important instruments in the search for other planets is the Kepler Space Telescope, which is credited with 2,331 confirmed exoplanet discoveries. It uses a technique called the transit method, watching for a star to dim when a planet passes in front of the distant sun. About 74 percent of known exoplanets have been discovered using that method, according to NASA.
  • Earlier this month, astronomers announced that they had evidence of perhaps as many as 114 new exoplanets; the data they used to find those came from Hawaii’s Keck Observatory, which made observations of over 1,600 stars for over two decades. One of those newly-discovered planets that has garnered attention is a hot, rocky “super Earth” called Gliese 411b.
  • Scientists have even discovered a planet orbiting the closest star to Earth, aside from the sun. Called Proxima b, that planet is somewhat larger than our own planet and lies about four light years away— close by cosmic standards but still incredibly far away from a human perspective. (One light year— the distance light can travel in one Earth year— equals almost 6 trillion miles.) The important Proxima b discovery was announced last August.

(Source: NASA/Université de Liège)

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