Planet hunting: How MIT's TESS will bring search for life closer to home
Scientists with MIT's TESS project hope to build on the lessons of the successful Kepler planet-hunting mission and find planetary systems close enough for telescopes to study in detail.
(Page 2 of 2)
TESS is slated to carry an array of four exquisitely sensitive telescopes that can detect variations of starlight as small as 0.000040 percent. That sensitivity not only brings Earth-mass planets at Earth-like distances orbiting sunlike stars well within TESS's ability to detect it. It also boosts the chance the observatory will detect small planets around smaller, dimmer stars – including red dwarfs. These are estimated to be the most numerous type of star in the galaxy.Skip to next paragraph
In Pictures Looking into the skies: Telescopes
Subscribe Today to the Monitor
Over TESS's two-year mission it will be tough for the observatory to spot planets that take 365 days or more to orbit their star, because TESS will not stare at the same patch of sky continuously, as does Kepler.
But Kepler has shown that virtually every star has at least one planet, and where there's one, often there are many, Hudgins notes. So for stars about the size of the sun or somewhat larger, TESS may only find the tip of an extrasolar planetary iceberg. It will be up to ground- and space-based telescopes to monitor these systems over longer periods of time to detect additional planets.
But for smaller, cooler stars, especially red dwarfs, habitable zones are closer to the star, where it doesn't take as long for a planet to complete an orbit.
In all, TESS could find several hundred Earth-mass planets, MIT's Dr. Ricker has estimated.
The mission will be able to take advantage of two research tools Kepler has pioneered for overcoming the limitations inherent in using the transit method of detecting planets, as the orbital winking is known.
The Kepler team has discovered, for instance, that it can detect slight variations in the timing of a planet's orbit when a system hosts more than one planet. The subtle change in timing results from the gravitational interaction among planets in a multiplanet system.
If Kepler can spot at least one of the additional actors, the data and a detailed knowledge of the host star allow the team to estimate the masses of the two planets. Armed with the planets’ sizes from the transit method and masses from timing the orbits, researchers can estimate the planets' densities. And knowing the orbital period, they can estimate how far the planets are from the star. Armed with their knowledge of how hot the star is, they can figure out whether any of the observed planets orbit within a star's habitable zone.
The Kepler team also has evolved a method for ruling out to a high level of confidence so-called false detections of planets – winks in a star's light that could come from variations in its own brightness or be influenced by another, dimmer star close by.
These approaches have allowed the Kepler team to use models to get a rough estimate of what the planets it discovers would be like without having to wait for additional observations from other teams. Such observations are typically too difficult to make because the stars in Kepler's field of view are so distant and dim.
"If you build really good tools, there's all kinds of smart, creative people that are going to figure out innovative ways to do things that you never imagined you could do with that instrument before you flew it," Hudgins says.
TESS's discoveries will have the benefit of closer, more detailed scrutiny by others. But Kepler's techniques will allow the TESS team to make initial inferences about the planets they discover, inferences that should help set priorities for follow-up measurements from other observatories, where telescope time is a precious, limited commodity.
Although TESS is four years away from its currently planned launch, the two missions send what Hudgins sees as an exciting message.
"We live in a galaxy that has an incredible number of planets in it. Virtually every star in our galaxy likely has planets around it. What TESS is going to do is show us the planets that are in our own backyard," he says.
RECOMMENDED: Are you scientifically literate? Take our quiz