Credits: NASA/JPL-Caltech
The discovery sets a new record for greatest number of habitable-zone planets found around a single star outside our solar system. All of these seven planets could have liquid water – key to life as we know it – under the right atmospheric conditions, but the chances are highest with the three in the habitable zone.
“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,” said Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington. “Answering the question ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”
Seven Earth-sized planets have been observed by
NASA's Spitzer Space Telescope around a tiny, nearby, ultra-cool dwarf
star called TRAPPIST-1. Three of these planets are firmly in the
habitable zone.Credits: NASAWatch this video on YouTubeThe TRAPPIST-1 star, an ultra-cool dwarf, has seven
Earth-size planets orbiting it. This artist's concept appeared on the
cover of the journal Nature on Feb. 23, 2017.Credits: NASA/JPL-CaltechView full image and captionAt about 40 light-years (235 trillion miles) from Earth, the system
of planets is relatively close to us, in the constellation Aquarius.
Because they are located outside of our solar system, these planets are
scientifically known as exoplanets.This exoplanet system is called TRAPPIST-1, named for The Transiting
Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. In May 2016,
researchers using TRAPPIST announced they had discovered three planets
in the system. Assisted by several ground-based telescopes, including
the European Southern Observatory's Very Large Telescope, Spitzer
confirmed the existence of two of these planets and discovered five
additional ones, increasing the number of known planets in the system to
seven.The new results were published Wednesday in the journal Nature, and
announced at a news briefing at NASA Headquarters in Washington.Using Spitzer data, the team precisely measured the sizes of the
seven planets and developed first estimates of the masses of six of
them, allowing their density to be estimated.Based on their densities, all of the TRAPPIST-1 planets are likely to
be rocky. Further observations will not only help determine whether
they are rich in water, but also possibly reveal whether any could have
liquid water on their surfaces. The mass of the seventh and farthest
exoplanet has not yet been estimated – scientists believe it could be an
icy, "snowball-like" world, but further observations are needed."The seven wonders of TRAPPIST-1 are the first Earth-size planets
that have been found orbiting this kind of star," said Michael Gillon,
lead author of the paper and the principal investigator of the TRAPPIST
exoplanet survey at the University of Liege, Belgium. "It is also the
best target yet for studying the atmospheres of potentially habitable,
Earth-size worlds."This artist's concept shows what each of the
TRAPPIST-1 planets may look like, based on available data about their
sizes, masses and orbital distances.Credits: NASA/JPL-CaltechView full image and captionIn contrast to our sun, the TRAPPIST-1 star – classified as an
ultra-cool dwarf – is so cool that liquid water could survive on planets
orbiting very close to it, closer than is possible on planets in our
solar system. All seven of the TRAPPIST-1 planetary orbits are closer to
their host star than Mercury is to our sun. The planets also are very
close to each other. If a person was standing on one of the planet’s
surface, they could gaze up and potentially see geological features or
clouds of neighboring worlds, which would sometimes appear larger than
the moon in Earth's sky.The planets may also be tidally locked to their star, which means the
same side of the planet is always facing the star, therefore each side
is either perpetual day or night. This could mean they have weather
patterns totally unlike those on Earth, such as strong winds blowing
from the day side to the night side, and extreme temperature changes.Spitzer, an infrared telescope that trails Earth as it orbits the
sun, was well-suited for studying TRAPPIST-1 because the star glows
brightest in infrared light, whose wavelengths are longer than the eye
can see. In the fall of 2016, Spitzer observed TRAPPIST-1 nearly
continuously for 500 hours. Spitzer is uniquely positioned in its orbit
to observe enough crossing – transits – of the planets in front of the
host star to reveal the complex architecture of the system. Engineers
optimized Spitzer’s ability to observe transiting planets during
Spitzer’s “warm mission,” which began after the spacecraft’s coolant ran
out as planned after the first five years of operations."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.”Following up on the Spitzer discovery, NASA's Hubble Space Telescope
has initiated the screening of four of the planets, including the three
inside the habitable zone. These observations aim at assessing the
presence of puffy, hydrogen-dominated atmospheres, typical for gaseous
worlds like Neptune, around these planets.This 360-degree panorama depicts the surface of a
newly detected planet, TRAPPIST 1-d, part of a seven planet system some
40 light years away. Explore this artist’s rendering of an alien world
by moving the view using your mouse or your mobile device.Credits: NASA In May 2016, the Hubble team observed the two innermost planets,
and found no evidence for such puffy atmospheres. This strengthened the
case that the planets closest to the star are rocky in nature."The TRAPPIST-1 system provides one of the best opportunities in the
next decade to study the atmospheres around Earth-size planets," said
Nikole Lewis, co-leader of the Hubble study and astronomer at the Space
Telescope Science Institute in Baltimore, Maryland. NASA's
planet-hunting Kepler space telescope also is studying the TRAPPIST-1
system, making measurements of the star's minuscule changes in
brightness due to transiting planets. Operating as the K2 mission, the
spacecraft's observations will allow astronomers to refine the
properties of the known planets, as well as search for additional
planets in the system. The K2 observations conclude in early March and
will be made available on the public archive.This poster imagines what a trip to TRAPPIST-1e might be like.Credits: NASA/JPL-CaltechSpitzer, Hubble, and Kepler will help astronomers plan for follow-up
studies using NASA's upcoming James Webb Space Telescope, launching in
2018. With much greater sensitivity, Webb will be able to detect the
chemical fingerprints of water, methane, oxygen, ozone, and other
components of a planet's atmosphere. Webb also will analyze planets'
temperatures and surface pressures – key factors in assessing their
habitability.NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California,
manages the Spitzer Space Telescope mission for NASA's Science Mission
Directorate. Science operations are conducted at the Spitzer Science
Center, at Caltech, in Pasadena, California. Spacecraft operations are
based at Lockheed Martin Space Systems Company, Littleton, Colorado.
Data are archived at the Infrared Science Archive housed at
Caltech/IPAC. Caltech manages JPL for NASA.
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