Team predicts satellite could locate hundreds of Earth-sized planets

Jan 12, 2010 by Morgan Bettex
If approved, TESS would spend two years searching the sky for planets orbiting roughly 2.5 million nearby stars. Image: Teague Soderman

(PhysOrg.com) -- The race to find exoplanets -- planets outside our solar system -- continues to quicken. Last week NASA researchers announced that the agency’s new space telescope, Kepler, has discovered five new exoplanets, expanding the number of known exoplanets to 422, an increase of about 25 percent in the past year alone. A satellite proposed by MIT researchers could accelerate these discoveries and even detect hundreds of Earth-sized planets — a few of which could be natural candidates for life.

The MIT team, led by Senior Research Scientist George Ricker of the Kavli Institute for Astrophysics and Space Research, is awaiting NASA approval for the Transiting Survey Satellite (TESS), which would conduct the first-ever spaceborne survey of transiting , or planets that pass in front of their host stars as seen from Earth. By searching a region of the sky 400 times larger than revealed by Kepler’s scope, TESS would observe 2.5 million of the closest and brightest stars when it is launched. Ricker’s team predicts it would detect between 1,600 and 2,700 planets within two years, including between 100 and 300 small planets.

“Although TESS should find hundreds of small planets, only a handful would be in the ‘’ and would be natural candidates for life,” said MIT assistant professor of physics Joshua Winn, who is part of Ricker’s team.

Most of the 422 exoplanets discovered to date (and catalogued here by astronomer Jean Schneider of the Paris Observatory) are hot Jupiters, giant planets that are likely inhospitable to biological activity. TESS would focus on finding smaller planets similar in size to Earth. Using six wide-angled, high-precision cameras to scan the sky for temporary drops in brightness caused when a planet passes in front of its star, TESS would measure the light obscured by a planet as it transits. TESS would then catalog the light curves caused by these transits so that follow-up work through ground observations and high-resolution spectroscopy can determine the planet’s mass, radius and density. Spectroscopic studies with the upcoming James Webb of bright exoplanets found by TESS could reveal details about a planet’s atmosphere, such as whether water or carbon dioxide exist.

Ricker’s team disclosed details about TESS in its first comprehensive public presentation at the annual American Astronomical Society conference on Jan. 6 in Washington.

A mix of science and guesswork

Winn and fellow MIT professor Sara Seager explained the science behind their estimate that TESS could detect as many as 2,700 planets, including several hundred Earth-sized planets.

Estimating how many planets TESS would find is a complicated process that Winn compares to counting how many people in a crowded stadium are waving cigarette lighters at the moment you take off a blindfold. The number would depend on how far away your eyes can detect a flame, as well as how many people are actually waving lighters at that moment. “The first question is a physics question,” Winn explained. “The second question is unanswerable unless you happen to know exactly how many people carry lighters and are likely to wave them around.” Add to that the fact that the flame from each lighter may have a different brightness, just as stars may differ in brightness and planets may differ in size. These factors had to be taken into account to estimate how many planets TESS might find.

To reach their estimate, the scientists made an educated guess about how many of these stars actually have planets orbiting them, based on information already known about giant planets, such as orbital distance and size. “It’s a bit more complicated, but we assume in this case that all planets are equally common, and that the abundance is about the same as the abundance of ,” Winn said of the several hundred giant exoplanets that have been found to date. The scientists then considered certain properties of the stars and of TESS, such as stellar luminosity and the size of the camera lenses, to estimate how many Earth-like planets will transit their host from a distance that TESS could probe.

Schneider said that although he hasn’t examined the numbers in detail, he believes the estimate and methodology are “a reasonable order of magnitude” given his experience with other satellites searching for exoplanets.

While the overall estimate is not surprising to the MIT team, it is the prospect of finding 100 to 300 Earth-sized planets that tantalizes astronomers.

The TESS project began in 2007 when NASA announced its Small Explorer (SMEX) satellite program to provide funding for science missions using small to mid-sized spacecraft. In June 2008, NASA selected Ricker’s team, which includes scientists from MIT, the Harvard-Smithsonian Center for Astrophysics and NASA-Ames Research Center, to receive $750,000 for an initial feasibility study. A year later, NASA elected not to proceed with TESS, but said the MIT-led group and other teams could submit new proposals later this year.

Ricker’s team is currently working on implementing modifications to the original proposal. “We are really making the case for NASA and the astronomy community as a whole to establish that this must be the next big leap that will be made in this field,” Ricker said.

TESS is part of a joint effort between the Kavli Institute, the Department of Physics and the Department of Earth, Atmospheric and Planetary Sciences at MIT to study exoplanets. The project also involves scientists at the Harvard-Smithsonian Center for Astrophysics, NASA Ames Research Center, NASA Goddard Space Flight Center and Las Cumbres Observatory Global Telescope Network.

Explore further: Image: Multicoloured view of supernova remnant

Related Stories

Recommended for you

Image: Multicoloured view of supernova remnant

32 minutes ago

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

35 minutes ago

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

45 minutes ago

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

Image: Horsehead nebula viewed in infrared

1 hour ago

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance ...

The Milky Way's new neighbour

1 hour ago

The Milky Way, the galaxy we live in, is part of a cluster of more than 50 galaxies that make up the 'Local Group', a collection that includes the famous Andromeda galaxy and many other far smaller objects. ...

Image: Hubble sweeps a messy star factory

1 hour ago

This sprinkle of cosmic glitter is a blue compact dwarf galaxy known as Markarian 209. Galaxies of this type are blue-hued, compact in size, gas-rich, and low in heavy elements. They are often used by astronomers ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

Aliensarethere
5 / 5 (1) Jan 12, 2010
This is not so different from the Kepler Telescope. One should focus on a next generation which can detect hundreds of Earth-like planets in the liquid water zone.
yyz
not rated yet Jan 12, 2010
Nothing against the concept of TESS, but wouldn't large, land-based survey telescopes like PanStarrs 4, VISTA and LSST pick up a sizeable portion of transiting exoplanets across a large swath of sky? I can see the need to look beyond the Kepler mission, but won't these large survey telescopes provide a large number of possible Earth-like transiting exoplanets for Herschel and JWST to scrutinize?
jsa09
1 / 5 (1) Jan 12, 2010
Given our solar system as a model it would be reasonable to presume that the smaller the planet the more of them there are.

The difficulty is not going to be in finding the stars with the planets but in being able to see the planets near the stars.

If the TESS is as accurate in measurement as the authors claim and it is possible to see an earth like planet around another star then it may well be able to see a Mars like planet as well.

I am however, pretty annoyed at people calling any planet that has been seen that is smaller than Jupiter an "Earth-Like" planet. That would make Venus an "Earth-Like" planet and it is nothing like the Earth even though it is almost the same size.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.