Skip to content
December 19, 2012 / JayMan

A Less Lonely Universe

dn23021-1_300It’s always good to have good news to report, and now is a great time for that. Following the recent discovery of an Earth-mass planet around our stellar neighbor Alpha Centauri, astronomers have recently announced the potential discovery of five near Earth-mass planets around another neighboring Sun-like star, Tau Ceti; of which, two may be able to support life as we know it (paper here).

Tau Ceti, after Alpha Centauri, is the next nearest Sun-like star, being of similar mass, age, composition, and temperature to our own Sun. It is situated 11.9 light years away (70.1 trillion miles), as can be seen on this map of nearby stars (within 12.5 light years):

Tau Ceti is near the bottom of the image.

The team used special filtering techniques to remove the “noise” in the star’s light, and by carefully analyzing its motion via the radial velocity method, they detected “wobbles” that are most consistent with a system of five planets. Assuming that these planets are close to their minimum masses (that is, if the plane of the system is not horribly inclined to our line of sight), these planets all appear to be in the vicinity of Earth’s mass. However, they are all on the heavy side (ranging from 2.0-6.6 times Earth’s mass), making them “super Earths”, bigger and heavier than our world.

Tau Ceti System

This is a schematic comparison of the Tau Ceti system to our own (inner) Solar System (outer gas giant planets excluded). The sizes of the planets and the central stars are NOT to scale with the radius of the planets’ orbits, but the orbits are to scale with each other and the planets are scaled to their relative sizes (assuming that the Tau Ceti planets are the same density as Earth.) The outer two planets are suspected to be in Tau Ceti’s “habitable zone”; that is, the orbital distance from the star where the temperature should be suitable for liquid water to exist on a planet’s surface. My own calculations shows that the habitable zone of Tau Ceti is actually a lot narrower than I’ve shown here, but I’ve artificially expanded it to include these planets. (In reality, Tau Ceti e is likely too close to the star for there to be liquid water on the surface.) Additional observations will be needed to confirm these planets, and their orbital parameters and bulk characteristics will be subject to refinement.

There are other issues with this system, however. One is that these planets are more massive than Earth, and it’s unclear what conditions would arise on planets with many Earth masses. Also, Tau Ceti possesses a much larger and more massive “Kuiper Belt” than our own Solar System. This is an extended region of large icy bodies at the outer fringes of the system—of which Pluto is a member in own Solar System. This massive disk of objects likely serves as a source of impacting bodies, which may lead to much more frequent large impacts of the type that caused the extinction of the dinosaurs here on Earth.

In any case, the fact that two of the nearby Sun-like stars are now known to harbor near Earth-mass planets—and indeed, one appears to have an entire planetary system, where one, and perhaps two of these planets may be life-bearing—is a testament to the likely ubiquity of such planets in the Galaxy. The confirmed discovery of a life-bearing planet elsewhere in the cosmos seems to be an eventuality that grows ever more imminent.

Since, presumably, intelligent, technological life should also be common in the Galaxy, it naturally follows to ask why we have not spotted any. A recent such discussion took place over at Mangan’s. While a variety of ideas were put forward (as they typically are in such discussions), the bottom line is we just don’t know; only time may (hopefully) tell.

Edit, 12/25/12: See this animation of the putative Tau Ceti system over at Sol Station (Java required).

Advertisements

15 Comments

Leave a Comment
  1. Dan / Dec 19 2012 3:31 PM

    There’s no intelligent life anywhere but here bro. Seti’s been going on forever, and zilch.

    I remember when a mars rock that landed in antarctica had bacteria and it was hailed by all the media as a discovery of extraterrestrial life. Fools just had a contaminated sample, probably from the scientists’ grubby, eager paws.

    Liberals seek salvation in the discovery of ET because they are terrified of being all alone. The big question in my mind is, why are liberals obsessed with finding space people that aren’t there?

    • JayMan / Dec 19 2012 6:11 PM

      There’s no intelligent life anywhere but here bro. Seti’s been going on forever, and zilch.

      When you’ve completed your survey of the Galaxy (nevermind the rest of the universe), do get back to me! 🙂

      The big question in my mind is, why are liberals obsessed with finding space people that aren’t there?

      It’s that openness to experience thing, the trait that liberals have that is being bred out. If you aren’t very open, you won’t get it.

    • redzengenoist / Dec 20 2012 12:03 PM

      “Seti’s been going on forever”

      It hasn’t, is the point.

      The fraction of time/space/spectra covered is an infinitely small subset of forever/everywhere/everything. SETI itself freely admits to being similar to Voyager, the probe we sent out to say “hello”. Voyager isn’t expected to “really” say hello, and SETI isn’t expected to “really” hear hello. It’s like listening for messages from God in the cosmic radiation; romantic science for its own sake.

    • Sarah Lambert / Dec 23 2012 8:18 PM

      “Fools just had a contaminated sample, probably from the scientists’ grubby, eager paws.” I didn’t know this had been proved. Do you have the reference?

      “Seti’s been going on forever, and zilch.” Well. there are a thousand million stars in the Galaxy, so if we spent 10 minutes looking at each star, it would take around nineteen thousand years to examine the whole galaxy. Seti has been looking for 52 years.

  2. Dan / Dec 20 2012 4:21 PM

    I was really big on SETI and space exploration generally when I was younger. In fact, Carl Sagan was a main reason I went to Cornell (although by the time I got there he was basically done interacting with students, probably because he was already very sick).

    Jayman, Seti devotees are every bit as religious as others — they pin inordinate hope on extraterrestrial salvation.

    At some point while staring at photos of other moons and planets I was struck by how utterly barren and dull it all is. We haven’t explored the universe, but we’ve worked hard at the moon, mars, etc. and have not discovered so much as a fossilized cell.

    Is it not something that a random 1 inch square of Earth is objectively more interesting (i.e. has more going on) than the whole solar system that we have seen so far?

    “SETI isnt expected to really hear hello”

    The hell it isn’t. If you think SETI (which is around 50 years old) isn’t serious about actually detecting life, you don’t know as much as about SETI you let on. If you would only remember the movie Contact, which was written by SETI pioneer Sagan (or any of Sagan’s other writing), you would appreciate that SETI is emphatically not science for its own sake, nor is it mere romance. There are some really big hopes and dreams pinned on finding another advanced civilization.

    • JayMan / Dec 21 2012 12:13 PM

      Is it not something that a random 1 inch square of Earth is objectively more interesting (i.e. has more going on) than the whole solar system that we have seen so far?

      No, not really, especially when you consider that are apparently untold billions of solar systems like ours in the Galaxy alone. It’s like searching one apartment in the Petronas Towers, finding no one living there, and then concluding that the rest of the skyscrapers must be empty…times a million…

  3. Dan / Dec 20 2012 4:38 PM

    I find it comedic that Newt Gingrich can talk about going to the moon again and be the butt of jokes while Obama can talk about Mars exploration and be hailed as a visionary. To laugh at the latter of course would be blaspheming against diety, something that the righteous media does not do.

    Since we have lost the ability to get to the moon we would need to master that level again toward reaching Mars. Not that Mars will be any different from the moon if present observations are any indication.

    But I understand if Obama needs to feel like JFK.

  4. tony_k / Dec 20 2012 8:56 PM

    I enjoy the concepts discussed on this and similar blogs despite being far behind the author and commenters in scientific knowledge and aptitude. So forgive this simplistic comment regarding the possibility of ET life.

    The discovery of planets possibly similar to Earth seems to presume intelligent, superior to human, life. I don’t understand that presumption. How many hundreds of thousands of species exist on Earth? Yet only one has emerged as an intelligent, self-aware, civilization building species. There’s no close second, capable of intra-planet travel, much less interplanetary. One species in a million and it’s taken eons to get here.

    I just don’t get the presumption that intelligent life, capable of even considering interplanetary travel, has beaten similar odds on any earth-like planet.

    • JayMan / Dec 20 2012 10:19 PM

      The sheer number of planetary systems and the very old age of the universe indicates that, even if the emergence of life is incredibly rare, there is still plenty of opportunity for it to happen. Our existence proves that the odds are not zero. Sure, we could be alone in our Galaxy if the evolution of a technological species is unlikely enough, but we have reasons to believe it is not quite so unlikely.

      The reason that any given technological species we would find is likely to be more advanced than us is the fact that, compared to the age of the Earth, or even the length of time that multicelluar life has existed, civilization seems to have emerged in a short amount of time. Assuming that the time scales for such events to occur on other planets is comparable, then the odds are any extant civilization is far, far older than our own, and hence, presumably, more advanced.

  5. Koichi Ito / Dec 23 2012 5:12 AM

    There was planet founded around Alpha Centauri B and Epsilon Eridani. Now we know that Tau Ceti has five planet orbiting around. So fourth planet from Tau Ceti (Tau Ceti b or Tau Ceti 4) could be our primised planet?

  6. wallowinmaya / Dec 30 2012 6:26 PM

    First of all, I really love your blog. Great job!

    But I have to comment on this post.
    If we discovered alien life forms, it would be very bad news. And not for speciesictic reasons.

    Why? Simply put, because of the Great Filter, (http://en.wikipedia.org/wiki/Great_Filter) a concept that kinda explains the Fermi Paradox.

    Here just a very short explanation in my own words, please read e.g. this paper by Oxford Philsopher Nick Bostrom (http://www.nickbostrom.com/extraterrestrial.pdf) or the Wikipedia entry.

    There are billions of planets out there, but we don’t see any alien civilization that colonizes the universe. There has to be some filter that prevents the transformation of dead matter to expanding life.
    There are basically two possibilities:
    1. There is an early Filter, i.e. the evolution of simple life is very improbable and we’re the only life form in the universe. That would explain the Fermi Paradox.
    2. There is a late Filter. Life evolves rather often but something prevents intelligent life from colonizing the galaxy.

    If we now observe some simple life forms, we can conclude that there is no early Filter. This means that there has to be a later Filter, i.e. something that stops all intelligent life from expanding into the universe. This doesn’t have to be a disaster, it could be that there are millions of life forms out there and all of them don’t want to colonize the universe. But IMHO it would be rather improbable that alien values and drives are so homogeneous. More likely is some kind of catastrophe.

    • JayMan / Dec 30 2012 8:05 PM

      First of all, I really love your blog. Great job!

      Thank you!

      There are billions of planets out there, but we don’t see any alien civilization that colonizes the universe. There has to be some filter that prevents the transformation of dead matter to expanding life.
      There are basically two possibilities:
      1. There is an early Filter, i.e. the evolution of simple life is very improbable and we’re the only life form in the universe. That would explain the Fermi Paradox.
      2. There is a late Filter. Life evolves rather often but something prevents intelligent life from colonizing the galaxy.

      The fundamental problem with this line of reasoning is that it makes two key assumptions:

      1. That technological life tends to expand indefinitely
      2. That such expansion or even the very existence of such life leaves easily detectable traces

      We do not know if either of these assumptions are correct. Indeed, there is good reason to believe that they are not true. Hence, the necessity of “The Great Filter” is obviated.

  7. wallowinmaya / Dec 31 2012 5:30 AM

    I would put those two key assumptions in more *probabilistic* terms:

    1. *Some* of the alien life try to expand indefinitely.

    Look at our own species. We’ve always searched for new ressources and tried to extend our habitat. There is a high probability that at least one of the million alien life (provided there is no early filter) forms out there tries to do the same.

    2. There are of course several possibilities, but it’s *likely* that at least one of the million life forms out there doesn’t give a shit about easily detectable traces and just tries to convert all matter in the universe in to something useful. Why should they try to hide? They have nothing to fear and could probably exterminate us if they wanted to.

    We don’t know much about the psychological characteristics of intelligent life forms, so we have to widen our confidence intervalls and assign moderate probabilities to all possible scenarios. But *if* there are many aliens out there, there is a moderate to high probability that at least one of them will have the drive and the means to colonize the galaxy.

    • JayMan / Dec 31 2012 10:26 AM

      1. *Some* of the alien life try to expand indefinitely.

      Look at our own species. We’ve always searched for new ressources and tried to extend our habitat. There is a high probability that at least one of the million alien life (provided there is no early filter) forms out there tries to do the same.

      Maybe. Maybe not. It’s entirely possible that indefinite expansion isn’t feasible or practical. After you’ve colonized a few solar systems, what further is there to gain? Expansion is driven primarily by population growth. Since technological advance might lead to prolonged lifespans, population growth might come to a standstill, and so would the need for expansion.

      There are of course several possibilities, but it’s *likely* that at least one of the million life forms out there doesn’t give a shit about easily detectable traces and just tries to convert all matter in the universe in to something useful.

      At what point does it stop being useful? If you could harness all the energy radiated by an entire star, just what would you do with it?

      The probability of the above situations could easily be exactly zero, again obviating the entire argument.

      The bottom line is that there are too many unknowns (both known and unknown) to start making too many declarations about the behavior of technological life. We will just have to see.

Trackbacks

  1. Me… « JayMan's Blog

Comments are welcome and encouraged. Comments DO NOT require name or email. Your very first comment must be approved by me. Be civil and respectful. NO personal attacks against myself or another commenter. Also, NO sock puppetry. If you assert a claim, please be prepared to support it with evidence upon request. Thank you!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: