TESS Finds First Earth-Size Planet in the Habitable Zone

From NASA

Jan. 7, 2020

TOI 700 Artists' Illustration

In a galaxy 100 light-years away in the constellation Dorado sits a planetary system named TOI 700. It is home to TOI 700 d, the first Earth-size habitable-zone planet discovered by TESS, NASA’s Transiting Exoplanet Survey Satellite.

Image Credit: NASA/Goddard Space Flight Center

Last Updated: Jan. 7, 2020

Editor: Yvette Smith

78 thoughts on “TESS Finds First Earth-Size Planet in the Habitable Zone

  1. I’m thinking there is a typo, there is no galaxy 100 light years away. Maybe another solar system within our galaxy that is 100 light years away but not another galaxy.

    • The meaning of the word “galaxy” in popular culture has morphed into meaning any stellar system like our solar system. The language is alive and continues to evolve in a way that will confuse older generations. It’s a pretty sick gig.

      • On the other hand, some folks are clueless. Time after time these editors and PR types put out stuff that is just plain wrong. Are the real scientists not allowed to correct them?

        My question is, what’s the justification for making the planet blue? Do they know it’s covered with water?

        • Yes, the text has many obvious mistakes that are only possible for a scientifically illiterate person to make.
          Of course NASA puts out briefs about science written by someone who is clueless about the topic. Thats how communication works today, organisations hite people who know nothing and dont think, to write about stuff and always get it wrong. I dont understand why that is a thing but it is.

        • I’ve seen them mistake (equate?) light years to AUs several times in articles, resulting in ridiculous scale distortions. Innumeracy: 1, 2, many.

          Can we please set aside just one planet for Constitutional, paleoconservatives? Otherwise, we age going to see liberals “destroy and migrate” issues we have between US States, except on a galactic scale. https://www.zerohedge.com/personal-finance/new-irs-data-reveals-winners-losers-wealth-migration-across-50-states

      • As Francisco d’Anconia said to James Taggert (Atlas Shrugged) “You ought to learn some day, Jim, that words have an exact meaning.” If you shrug and allow mis-uses of defined words because of some form of post-modern laxity, eventually no-one will be able to communicate with anyone.

        • except words dont have exact meanings.

          cleave is my favorite.

          the history of linguistic change demonstrates, empirically, that your panic about mis using words is unfounded. no disaster.

          disaster. go look at that words history

          • Some words change in meaning over time.
            Other words have multiple meanings.

            Neither of those is the same thing as not having an exact meaning.
            Surely an English major should know that.

          • Having had an on-going discussion with one of the two polymaths that I know, I learned that words don’t have meaning at all. They have “common usage”. However, within a technical discipline, it is valuable for words to have specific meanings, and for those meanings to be constant. The PR flack who wrote the press release knew his/her audience, the general public (and Congress, of course).

          • Having had an on-going discussion with one of the two polymaths that I know, I learned that words don’t have meaning at all. They have “common usage”. However, within a technical discipline, it is valuable for words to have specific meanings, and for those meanings to be constant. The PR flack who wrote the press release knew his/her audience, the general public (and Congress, of course).

    • I would put it as only a poetic note, not more. Our Milky Way is almost 1000 times bigger then that… Sure the author knows this…

      From Nasa’s link:
      ” TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It’s roughly 40 of the Sun’s mass and size and about half its surface temperature.”
      I guess that is 40% of the Sun’s mass

      ” The star appears in 11 of the 13 sectors TESS observed during the mission’s first year, and scientists caught multiple transits by its three planets.
      The innermost planet, called TOI 700 b, is almost exactly Earth-size, is probably rocky and completes an orbit every 10 days.
      The middle planet, TOI 700 c, is 2.6 times larger than Earth — between the sizes of Earth and Neptune — orbits every 16 days and is likely a gas-dominated world.
      TOI 700 d, the outermost known planet in the system and the only one in the habitable zone, measures 20 larger than Earth, orbits every 37 days and receives from its star 86% of the energy that the Sun provides to Earth.

      Is that 20 times larger then Earth? I know, I am no native english speaking, so maybe natives could help me understand.
      From the article it looks like the Earth size planet (TOI 700b) is not in the habitable zone.
      The one in habitable zone is 20 times bigger or whatever 20 larger means?

        • “(mass is 70% larger)”

          So it really shouldn’t be described as “Earth-like”. To be Earth-like, it would have to be a size that suits human beings, I would say.

          • It shouldn’t be too bad. Acceleration due to gravity at the surface would be about 11.6 m/s2 instead of Earth’s 9.8 m/s2. (Multiply by 1.7 for increased mass, divide by 1.2 squared because gravity is an inverse-square law.) You’d get an extra 44% surface area, too.

      • There’s been many decades-long dumbing-down of seemingly everything presented to the public. The article-writers can’t even get simple things like numbers/percentages right.

    • “In a galaxy 100 light-years away in the constellation Dorado …”

      I noticed that, too. It should be corrected to read “In a galaxy far, far away….” 🙂 and the music should swell just slightly in volume. Must be a reference to the galaxy Luke and Leia are watching through that open door at the end of “Empire Strikes Back”.

      • They must have meant Solar System rather than Galaxy as we can’t resolve stars well enough in other Galaxy’s to resolve planetary transits

      • That’s what I thought — maybe a (rather lame) inference to the Star Wars movies.

        Maybe the writer(s) can make a record-breaking run to the grocery store in less than 12 parsecs. 🙂

    • You’re right, Sam.

      From the website: “TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It’s roughly 40% of the Sun’s mass and size and about half its surface temperature. The star appears in 11 of the 13 sectors TESS observed during the mission’s first year, and scientists caught multiple transits by its three planets.

      TOI 700 d, the outermost known planet in the system and the only one in the habitable zone, measures 20% larger than Earth, orbits every 37 days and receives from its star 86% of the energy that the Sun provides to Earth. All of the planets are thought to be tidally locked to their star, which means they rotate once per orbit so that one side is constantly bathed in daylight.

    • In a galaxy 100 light-years away in the constellation Dorado sits a planetary system named TOI 700.

      Galaxy DIAMETER = 2 x radius:

      https://www.google.com/search?q=galaxy+diameter+in+light+years&oq=galaxy+diame&aqs=chrome.
      ____________________________________

      https://www.google.com/search?q=constellation+Dorado+milky+way&oq=constellation+Dorado+milky+way&aqs=chrome.

      The Constellation Dorado – In-The-Sky.org
      constellation Dorado milky way von in-the-sky.org

      “The Milky Way’s dwarf satellite galaxy, the Large Magellanic Cloud, falls mostly within Dorado, with the remainder lying in Mensa.”

  2. Whoa! No galaxy is …100 light years away”. Where IS this new planet? It’s not in this so-called galaxy.”

  3. Cool! I wonder if it benefits from the same remarkably stable climate (+/- a couple degrees C) that we’ve enjoyed these past 11000 years or so!

  4. In a galaxy 100 light years away

    It’s around 2.5 million light years to Andromeda. I guess that would be in our galaxy, 100 light years away?

    Or is that a joke that went over my head?

  5. Calling all doomsters your SpaceX flights to TOI 700 will soon be boarding-
    https://www.spacex.com/mars
    “You want to wake up in the morning and think the future is going to be great – and that’s what being a spacefaring civilization is all about. It’s about believing in the future and thinking that the future will be better than the past. And I can’t think of anything more exciting than going out there and being among the stars.”

    • “And I can’t think of anything more exciting than going out there and being among the stars.”

      Just like Ricky Gervais…

  6. Would it be correct to assume that another Earth size planet would have a near enough similar gravity? Perhaps it’s interior might be mostly lead in which case it’s first skiers might look more and more like fat toads as they ski further and further downhill, to say nothing about atmospheric pressure. I think we should be told before booking with Ryan air for our off world ski trip.

    • The estimated mass is 1.7x Earth (with large error bars). The radius is 20% more than Earth, so, if the estimated mass is anywhere close, the surface gravity would be about 20% more than Earth’s.

      • That’s OK as the doomsters would be a lot skinnier by the time they got there. Besides they don’t want to fly but ride their bicycles or walk on Utopia.

        • Alot of the doomsters are so indoctrinated about the Earth’s imminent demise that they think Mars is our only hope. I almost feel sorry for their delusions, but would support their departure.

  7. Maybe I’m missing something but with such fabulous new technology why do we continue to see the same 20+ year old photos of the planets in our own solar system? A few new ones but not many and none of at least five planets.

    • I don’t think that’s one of ours. (Neptune is the only possibility.) Looks computer generated to me.

      One reason for few new photos is that Cassini’s mission is over and the various orbiters are looking at small features on our moon and Mars.

      • Apart from the rings those images are distant and underwhelming, Andy. Why no new shots of most of the planets for decades? And we see images of the surface of Mars but not Venus? The ‘atmosphere’? Oh please. It’s not called Never A Straight Answer for nothing.

    • No reply from NASA in my Email today, and the error is still on the web. Maybe I’ll try some potential Email addresses to get Yvette Smith directly.

  8. This really is a bad joke to consider any planet in M-class star system Earth-like.
    For it to be in a “habitable zone” means close enough for warmth to keep water liquid on a surface with an Earth-like atmosphere. TOI-700d may fit that one parameter, but the closeness certainly means its tidally locked in spin rotation, like Mercury is to our Sun. One side bakes, the other side is frozen solid.
    Furthermore, even though they observed no flaring from that particular M class star in the few years they watched it, means little in the longer term of many millions of years needed for life to evolve. M class stars are noted for typical massive super-flaring. (Their convective zone is in direct contact with the outer-core, that is they have no radiative zone) The closeness needed for a “habitable zone” in a dwarf star system means even one superflare would likely sterilize any of it planets hit by the xrays and CME blast.

    Really a bad joke to call this an “Earth-like” planet.

    • I would think a planet would need to orbit a “Sol-like” star in order to possibly have an “Earth-like” climate. Dwarf stars would periodically blast the planet with flares, while larger stars would continuously blast it with UV and worse. Merely being in the “Goldilocks zone” is the just the beginning of requirements to make a planet Earth-like.

      SR

      • “I would think a planet would need to orbit a “Sol-like” star in order to possibly have an “Earth-like” climate.”

        I think that’s right. We are looking for a planet and star that matches our solar system as closely as possible. Red Dwarfs are not even close. Worlds on which humans weigh twice as much as on Earth are not even close.

    • I agree Joel — there will be oodles of planets discovered in a “habitual zone” zone around their star, but that itself would say little about the potential for life, particularly around an M-star. Now if such an earth-size (assumed rocky) was found around a sun-like G star, that would be interesting.

    • “and receives from its star 86% of the energy that the Sun provides to Earth.” Earth is barely warm enough for life and has resulted in snowball earth conditions multiple times. With only 86% of the energy, I don’t imagine the planet could be suitable for life; likely more similar to Mars than earth.

    • Some of NASA-Goddard Space Flight Center’s main web hosting servers are currently down this morning (and still as of 1/08/2020 1930 UTC). Apparently they let their SSL certificate expire on 1/7/2020, so that at UTC midnight going to 1/08/2020 getting a secure https connection using their RSA certificate won’t work for anyone.

      It is only affecting some of GSFCs webhosting though, as GSFC’s STEREO pages are still on-line/accessible:
      https://stereo.gsfc.nasa.gov/beacon/

      But GSFC’s SDO is down/inaccessible:
      https://sdo.gsfc.nasa.gov/data/

  9. T 701d may be in the “habitable zone” (warm enough for liquid water but not too hot to boil it away) IF it had a period of rotation much shorter than its period of revolution around its star, so that heat accumulated during daylight hours could dissipate during night-time hours anywhere on the planet, such as occurs on Earth.

    But if it is “tidally locked” so that the same side always faces its star, any liquid water on the daylight side would rapidly boil away, and on the dark side would be permanently frozen. If this planet ever had any water, it could remain liquid only near the edges of the daylight side, with a low angle of incidence of light from the star (in the twilight zone, with apologies to Rod Serling).

    If the dwarf star only has 40% of the Sun’s mass and half its (absolute) temperature, by the Stefan-Boltzmann law it would produce only (0.5)^4 * 0.4 = 2.5% of the Sun’s radiant energy, so that its orbital radius would have to be only about 16% of the Earth’s distance from the Sun in order to receive the same radiation intensity at the zenith as the Earth does from the Sun. Since the planet T-701d has an orbital period shorter than that of Mercury and is tidally locked, its surface probably resembles Mercury more than Earth.

    The mass of a planet does affect its “habitability”, in terms of the gravity required to hold a gaseous atmosphere. The Moon receives about the same amount of solar radiation as the Earth, but the Moon cannot hold an atmosphere with its much weaker gravity.

    But the planet’s mass and the amount of radiation received are not the only conditions for “habitability”–the planet must also rotate much faster than its period of revolution, so that heat accumulated during daylight can be dissipated at night, without too much fluctuation in temperature. This is much more likely for planets with longer orbital periods (farther from their stars), but for such planets to receive the optimum amount of radiation from their star, the star must emit radiation nearly equal to or greater than the radiation emitted by the Sun.

    • These TESS transit searches for exoplanets are biased towards finding systems that have planets with short orbital periods, that is much less than 365 Earth days. This is due to the rescanning coverage periods (plates as they are called) involved and the operational lifetime of the TESS mission and the time spent collecting the data. Finding a planet like Earth at ~ 1 AU on G class star (similar to our with our 8,766-hour orbital period would require continuous observations of several decades or more to distinguish the Earth-transit dimming and then the deconvolution of that long-duration transit dimming signal from the other planets (Venus, Mars, Jupiter, Saturn) in our system.
      So TESS is only likely to find fast orbiting exoplanets. Which for habitable zones means finding them around the very abundant M-class dwarf stars. And M-class dwarfs are all ill-behaved with lots of intense magnetic-induced flaring. That they didn’t observe that in this one case doesn’t exclude that.

      Further, the ability to hold a gaseous atmosphere of water vapor for billions of years for a rocky planet is also likely dependent on a magnetic shield. Vapor H2O will get dissociated by EUV/UV. The hydrogen will get stripped off much more rapidly if the TOA is being ablated by stellar winds. If the host star flares, any protective ozone will be destroyed, bathing the lighted-side surface with intense EUV/UV. On Earth of course our geomagnetic shielding greatly diminishes solar wind ablation of the exosphere/upper stratosphere. TO1-700d may be large enough to have a molten outer core to drive a MHD dynamo. But regular flaring would strip away any ozone formed from O2 liberated from UV-water dissociation.

      Then there is our Moon stabilizing our obliquity transit range. Also driving lunar tidal induced crustal flexing which aids Earth’s tectonics and plate recycling.

      I am a proponent of the very extremely rare Earth hypothesis. Something on the order of 1 in 10^13 stars might host an Earth-like planet with all our life-giving, life sustaining characteristics. That means we are very likely alone in our galaxy.

      • Once you end up with only one side of the planet facing the sun (star), your atmosphere vanishes. The temp on the back side is so cold everything solidifies. You end up with a planet like our moon that is hard vacuum. Any air on the hot side that travels to the cold side freezes. Or gets so hot it escapes. That does not take very long to happen. No air, no life.

        These M class stars do not have a “habitable” zone. Someone does not understand what this word means.

      • I subscribe to that myself (“Rare Earth”). The evidence (such as it is) seems compelling.

        However, I do have to watch myself – the hypothesis is very handy for my fictional world building, so I do evaluate it with an inbuilt bias…

      • Joel, the M-star in question was said to be slow-rotating, so perhaps not any longer much flair-prone. But that would prb’ly mean the system is very old & planets around it prb’ly internally cold & devoid of atmospheres.

        Perhaps a large moon of a gas-giant (and tidally-locked to the giant) in the habitable zone of an M-star might be protected by the giant’s magnetic field & be able to hold an atmosphere…..

      • “These TESS transit searches for exoplanets are biased towards finding systems that have planets with short orbital periods, that is much less than 365 Earth days. This is due to the rescanning coverage periods…”

        Interesting. So you’re saying astrophysicists haven’t yet reached the competency of climate scientists, who can now detect “climate change… from any single day of weather at global scale.”

    • Additionally, recently I was reading about the differences between Venus and Earth. Theories tell us that the event that created our moon reduced the density of our atmosphere, making earth’s surface less hellish, and more like, well, earth. A planet 70% more massive than earth would likely have a very thick atmosphere unless a catastrophic event like the creation of our moon had happened there as well.

  10. In other words, in order to be Earth-like, a planet would need to orbit a Sol-like (G class) star at an Earth-like distance, rotating at an Earth-like rate, having an Earth-like size with an Earth-like atmosphere, and a surface having land and sea coverage with Earth-like ratios.
    Slightly closer proximity to its sun could be compensated by faster rotation, while slightly larger size could be compensated by a slightly less dense or smaller core. Slightly greater distance from its sun could be compensated by a slightly denser atmosphere.

    SR

    • >>In other words, in order to be Earth-like, a planet would need << and to have been hammered by an iron and oxygrn rich planetary mass early on forming a hot iron core, giving lots of oxygen and other heavy elements, and providing a nice periodic tidal flow to stir things up.

  11. “In a galaxy 100 light-years away in the constellation Dorado sits a planetary system named TOI 700. It is home to TOI 700 d, the first Earth-size habitable-zone planet discovered by TESS, NASA’s Transiting Exoplanet Survey Satellite.”

    Do tell…
    Announcing such absolute conclusions based on observing cyclical dimming of the host star; provide zero evidence on what caused the dimming. Forall we know, the dimming is caused by a charcoal flight of interstellar birds stuck in orbit around the sun.

  12. A planet in a Goldilocks zone is not news, a galaxy at 100 light years distance is. LOL.

    Makes you wonder about publishing QC procedures at NASA.

    BTW, error is still there after two days…

      • NASA might be right that the star is from another galaxy. I remember reading a while back that there are at least a score of dwarf galaxies orbiting the Milky Way. One of them is the Sagittarius Dwarf galaxy that is being stretched and splattered into an elliptical stream of gas and stars that arches above and intersects with the plane of Milk Way right where we sit in the Orion arm. The implication is that any of our local stellar neighbors might be from Sagittarius, which technically is another galaxy. Sol might be an interloper from Sagittarius, which would make us the aliens in the Milky Way.

  13. Mercury actually DOES rotate relative to the sun. It is in a spin-orbit resonance. Possibly some of these planets of M-class stars are in stable spin-orbit resonances?

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