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Astronomers Detect Four Earth-Sized Planets Orbiting The Nearest Sun-Like Star (ucsc.edu)

Posted by BeauHD on from the hop-skip-and-a-jump-away dept.

Tim Stephens reports via The University of California in Santa Cruz: A new study by an international team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby sun-like stars. Two of them are super-Earths located in the habitable zone of the star, meaning they could support liquid surface water. The planets were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimeters per second. The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.

10 of 102 comments (clear)

  1. Re:30 cm/s by ShanghaiBill · · Score: 3, Informative

    Fir those who wonder, 30 cm/s is roughly 10km/h, so about the speed of a jogger.

    You are off by a factor of 10. It is about 1 km/h, so about the speed of a fast tortoise.

     

  2. Sun gravitational lens by Katatsumuri · · Score: 5, Informative

    Our best bet to get a closer look any sooner is to use our Sun as a gravitational lens. It is still a challenge, because we would need to put a telescope at the correct side of the Sun at about 550 AU, far beyond the orbit of Pluto, but it is much closer to our technological reach than actual interstellar probes. NASA is thinking about this project: https://www.technologyreview.c...

  3. Getting close to answering a BIG question! by wisebabo · · Score: 2

    Wow, it appears like we are really getting close to being able to answer the question: are we alone in the Universe?

    I'm amazed that they were able to detect the "wobbles" using (relatively) inexpensive ground-based telescopes. Just a little bit of improvement and they'll be able to detect earth sized planets (although maybe 1.7x mass isn't too bad; I think the surface gravity might be just a little higher depending on the density).

    Soon, a space based telescope (the James Web ST?) may, with these super-sensitive instruments, be able to take the next crucial step and determine the composition of their atmospheres. If they detect free oxygen or other products of biological (or even industrial!) by-products, we'll know that there's life elsewhere in the universe! Maybe we'll find out sooner this way than a similar positive result coming from a probe we send to Mars, Europa, Enceladus or Titan.

    Of course, although I'm hoping that we'll see a biological signal, I really really doubt we'll see something that is the product of a technological civilization. Unfortunately, we still don't know the answer to Fermi's paradox. (I really wish the Chinese would take their new giant radio telescope and dedicate it to looking for signals). Until we hear from someone; we'll have to assume that maybe (intelligent) life in the Universe is rare.

    I hope it's not because intelligent life usually kills itself off (like we seem to be doing: https://www.nytimes.com/2017/0...

    Full disclosure: in my partially misspent youth I worked on S.E.T.I. :)

    1. Re:Getting close to answering a BIG question! by Baron_Yam · · Score: 4, Interesting

      >we still don't know the answer to Fermi's paradox.

      "Space is big. Really big. You just wonâ(TM)t believe how vastly hugely mindbogglingly big it is. I mean you may think itâ(TM)s a long way down the road to the chemistâ(TM)s, but thatâ(TM)s just peanuts to space." - The Hitchhikerâ(TM)s Guide To The Galaxy

      I know some space enthusiasts talk about even a single civilization sending out a Von Neumann probe resulting in the whole galaxy being blanketed in a few hundred million years... but space is big, hostile, slow to traverse, and resources are really tough to get access to.

      It's very much possible that there's no single answer to the Fermi Paradox, but it's a little bit of all the factors. The base raw materials for life are likely extremely common (similar clouds of gas collapsing into similar systems), but life may be rare and I would expect complex life building technologically advanced space-faring (or even communicating) civilizations to be a fraction of those.

      Combine the likely rarity of intelligent life with the massive distances (involving massive time delays)... and you can get a lot of lonely species all thinking there's nobody else out there simply because they can't communicate with each other in any practical way.

    2. Re:Getting close to answering a BIG question! by Xyrus · · Score: 2

      We're far more likely to be able to detect signs of biological/technological processes in another planet's atmosphere long before we actually hear any radio signals from them. To detect a radio signal things need to happen in just the right way for us to hear it. For atmospheric detection all we need is a spectral analysis. You find CFCs in their atmosphere and it's pretty certain that something a little more advanced than bacteria are on that planet.

      --
      ~X~
  4. Re:30 cm/s by Anonymous Coward · · Score: 2, Interesting

    Is speed of the wobble what was meant? I thought it must be 30cm/second of rotational arc, which translates to a 200km peak variation as the planet orbits from one side 180 deg around to the other.

  5. Re:closer look by Anonymous Coward · · Score: 2, Insightful

    I think we're still at the phase of our development where there is no point sending out interstellar probes. By the time they get there, either there is no human race left to monitor the info they send back, or we already sent out faster and better equipped probes that overtook them along the way. There is far more within our solar system that we have to study, perfecting the propulsion techniques with gradually increasing distances first.

  6. Re: 30 cm/s by Anonymous Coward · · Score: 2, Informative

    It is the radial speed of the star b ing measured via doppler shift. It is the speed that the star is moving toward and away from Earth as a result of the orbiting planets' gravitational tug on the star.

  7. Re:closer look by Sique · · Score: 2, Insightful
    Going back to Paracelsus and his doctrine ("All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy."), we find out, that "lethal plant" is not a good qualifier. To the contrary: Anything that's not lethal to us in a certain dose does not have any effect on us. Otherwise we could increase the effect by increasing the dose until it is lethal.

    Thus we can conclude: Anything that (in a certain dose) has a lethal effect on us, might have another, maybe beneficial effect on us if dosed right. So all we need is the proof that a plant has an effect on us. And how will you do that without having a human (or a model organism like bacteria or guinea pigs instead of a human) nearby to test for the effect?

    --
    .sig: Sique *sigh*
  8. Re:super earths by Baron_Yam · · Score: 2

    When the term Earth-like is used, it usually means 'rocky planet of approximately the same mass'.

    Whether it's the right temperature, has an atmosphere, is in a 'safe' orbit with theoretically tolerable levels of radiation and reasonable temperature variation, tidally locked, etc... all more or less up for grabs depending on who offered the quote and who is reporting it.

    I expect the term will end up being more specific as we learn of more exoplanets and improve our ability to determine their characteristics.