In 2018, NASA launched a probe called TESS (Transiting Exoplanet Survey Satellite) a highly specialized form of space-based telescope designed to search out exoplanets orbiting distant stars. Now, over four years into its mission, TESS has identified over 2,100 possible planets. Recently, TESS has been used in concert with the Hubble telescope to study a distant “super-Earth,” and paired with Hawaii's Keck Observatory to observe a series of doomed planets that are spiraling into their star.
In 2018, DailyKos was on hand for the launch of TESS and interviewed program scientist Dr. Doug Hudgins about all the possibilities ahead for TESS. Four years into what was originally a two year mission, deputy project scientist Dr. Allison Youngblood was kind enough to share what TESS has revealed, what remains to discover, and how new instruments like the James Webb Space Telescope are providing even more ways to extend the discoveries from TESS.
Among other things, Dr. Youngblood explains why so many of the planets TESS finds are much closer to their stars than Earth, why the other planetary systems we observe seem so different from our own, and how you can personally become involved in helping TESS locate new worlds.
TESS finds planets using the “transit method.” That it, it measures the light coming from the stars it observes and looked for dips in the output. If those dips are regular, it can show that part of the star is being regularly blocked a planet moving between that star and Earth.
The secret to TESS’s success is that its instruments are capable of observing a number of stars at a time, so it’s possible to keep an eye on many stars long enough to catch a planet going by. Even so, there are reasons why stars under scrutiny from TESS can have planets that still go unnoticed. For one thing, the orbits of those planets may be at such an angle that they don’t come between the star and Earth, so no matter how long we looked, we wouldn’t see them.
Time is also a factor. For example, if TESS was sitting at another star looking back at Earth, scientists might have to wait a year to have any clue it was there, and more years to see that signal repeat. For that reason, TESS tends to look at smaller stars than our own Sun, where planets in the “habitable zone” have much shorter orbits.
So, in perfect conditions, TESS would see almost 10 times as many transits of TOI-700 d, and each one of those transits would be easier to spot.
Because of the need to capture multiple transits, and because the scientists involved were looking ahead to how TESS could work in conjunction with the JWST, most of TESS targets are actually M-class “red dwarf” stars that are both smaller and cooler than the sun. The habitable zone around these stars, which is defined as the distance from the star where liquid water could exist, is much closer than around the Sun. So planets travel faster. So TESS sees more transits. And because the stars are smaller, planets block relatively more of their light. That makes for a clearer signal. For TESS and other systems studying transits, these M-class dwarfs are the best.
However, just because a planet is in the habitable zone, doesn’t mean it’s actually habitable. People may get visions of steaming jungles—or alien cities—every time terms like “super-Earth” come up, but the name doesn’t mean they’d be super places to live.
When it comes to the discoveries of TESS, it takes more than just computers crunching the return data to find new planets. Citizen science programs like Planet Hunters TESS allow anyone to sit down, go through a quick tutorial, and start sifting through data in a way that’s very hard for machines to match.
One of the things that has turned up with TESS, as it did with earlier exoplanet missions like Kepler, is that the systems we’re discovering just don’t look much like ours. And that seems to be true even when we look at other stars similar to our own. Does this mean that our own Solar System is unusual?
One other place you’re likely to be hearing about TESS in the near future is in reports from the James Webb Space Telescope. While the beautiful images of galaxies and nebulas may get a lot of attention, when it comes to priority targets, TESS is helping to define where that new instrument gets directed. In fact, finding planets for JWST to look at was one of the TESS mission’s main objectives. They were designed to work together.
Those planets are ones where Webb has a good chance of making discoveries about the makeup of the planet’s atmosphere. That might reveal if any of those planets in the habitable zone actually have high levels of water present.
While TESS may already be operating beyond the limits of its initial mission, that mission is far from over.
So maybe TESS will discover a not-so-super Earth, orbiting a not-so-dwarf star after all. Given enough time, and enough helping eyeballs to scan the data, worlds very much like our own just might appear in the data. In the meantime, TESS is generating data, not just on planets, but stars, asteriods, and comets.
TESS will keep operating for years. Maybe decades. And it will keep returning data that’s valuable for many areas of science. But it’s not the last of its kind.
It turns out that hunting exoplanets requires just the kind of instrument that are good for a lot of other space science, so the search for other worlds also brings back data on a whole host of subjects. And from all these missions we get at least a glimpse of all the possibilities that lie out there among the stars.
In 2018, DailyKos was on hand for the launch of TESS and interviewed program scientist Dr. Doug Hudgins about all the possibilities ahead for TESS. Four years into what was originally a two year mission, deputy project scientist Dr. Allison Youngblood was kind enough to share what TESS has revealed, what remains to discover, and how new instruments like the James Webb Space Telescope are providing even more ways to extend the discoveries from TESS.
Among other things, Dr. Youngblood explains why so many of the planets TESS finds are much closer to their stars than Earth, why the other planetary systems we observe seem so different from our own, and how you can personally become involved in helping TESS locate new worlds.
TESS finds planets using the “transit method.” That it, it measures the light coming from the stars it observes and looked for dips in the output. If those dips are regular, it can show that part of the star is being regularly blocked a planet moving between that star and Earth.
The secret to TESS’s success is that its instruments are capable of observing a number of stars at a time, so it’s possible to keep an eye on many stars long enough to catch a planet going by. Even so, there are reasons why stars under scrutiny from TESS can have planets that still go unnoticed. For one thing, the orbits of those planets may be at such an angle that they don’t come between the star and Earth, so no matter how long we looked, we wouldn’t see them.
Time is also a factor. For example, if TESS was sitting at another star looking back at Earth, scientists might have to wait a year to have any clue it was there, and more years to see that signal repeat. For that reason, TESS tends to look at smaller stars than our own Sun, where planets in the “habitable zone” have much shorter orbits.
So, in perfect conditions, TESS would see almost 10 times as many transits of TOI-700 d, and each one of those transits would be easier to spot.
Because of the need to capture multiple transits, and because the scientists involved were looking ahead to how TESS could work in conjunction with the JWST, most of TESS targets are actually M-class “red dwarf” stars that are both smaller and cooler than the sun. The habitable zone around these stars, which is defined as the distance from the star where liquid water could exist, is much closer than around the Sun. So planets travel faster. So TESS sees more transits. And because the stars are smaller, planets block relatively more of their light. That makes for a clearer signal. For TESS and other systems studying transits, these M-class dwarfs are the best.
However, just because a planet is in the habitable zone, doesn’t mean it’s actually habitable. People may get visions of steaming jungles—or alien cities—every time terms like “super-Earth” come up, but the name doesn’t mean they’d be super places to live.
When it comes to the discoveries of TESS, it takes more than just computers crunching the return data to find new planets. Citizen science programs like Planet Hunters TESS allow anyone to sit down, go through a quick tutorial, and start sifting through data in a way that’s very hard for machines to match.
One of the things that has turned up with TESS, as it did with earlier exoplanet missions like Kepler, is that the systems we’re discovering just don’t look much like ours. And that seems to be true even when we look at other stars similar to our own. Does this mean that our own Solar System is unusual?
One other place you’re likely to be hearing about TESS in the near future is in reports from the James Webb Space Telescope. While the beautiful images of galaxies and nebulas may get a lot of attention, when it comes to priority targets, TESS is helping to define where that new instrument gets directed. In fact, finding planets for JWST to look at was one of the TESS mission’s main objectives. They were designed to work together.
Those planets are ones where Webb has a good chance of making discoveries about the makeup of the planet’s atmosphere. That might reveal if any of those planets in the habitable zone actually have high levels of water present.
While TESS may already be operating beyond the limits of its initial mission, that mission is far from over.
So maybe TESS will discover a not-so-super Earth, orbiting a not-so-dwarf star after all. Given enough time, and enough helping eyeballs to scan the data, worlds very much like our own just might appear in the data. In the meantime, TESS is generating data, not just on planets, but stars, asteriods, and comets.
TESS will keep operating for years. Maybe decades. And it will keep returning data that’s valuable for many areas of science. But it’s not the last of its kind.
It turns out that hunting exoplanets requires just the kind of instrument that are good for a lot of other space science, so the search for other worlds also brings back data on a whole host of subjects. And from all these missions we get at least a glimpse of all the possibilities that lie out there among the stars.