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Stars Traveling Close To Light Speed Could Spread Life Through the Universe

Posted by samzenpus on from the starry-life-seed dept.

KentuckyFC writes Stars in the Milky Way typically travel at a few hundred kilometers per second relative to their peers. But in recent years, astronomers have found a dozen or so "hypervelocity stars" traveling at up to 1000 kilometers per second, fast enough to escape our galaxy entirely. And they have observed stars orbiting the supermassive black hole at the center of the galaxy traveling at least an order of magnitude faster than this, albeit while gravitationally bound. Now a pair of astrophysicists have discovered a mechanism that would free these stars, sending them rocketing into intergalactic space at speeds in excess of 100,000 kilometers per second. That's more than a third of the speed of light. They calculate that there should be about 100,000 of these stars in every cubic gigaparsec of space and that the next generation of space telescopes will be sensitive to spot them. That's interesting because these stars will be cosmological messengers that can tell us about the conditions in other parts of the universe when they formed. And because these stars can travel across much of the observable universe throughout their lifetimes, they could also be responsible for spreading life throughout the cosmos.

12 of 184 comments (clear)

  1. Anyone for a game of pool? by Ded+Bob · · Score: 4, Funny

    The stakes are stellar.

  2. Cubic gigaparsec ... by Mostly+a+lurker · · Score: 4, Funny

    Ummm, how many Olympic sized swimming pools is that?

    1. Re: Cubic gigaparsec ... by AA1 · · Score: 5, Informative

      (2.93799895 Ã-- 10^79) liters in cubic gigaparsec divided by about 2.5 million liters per Olympic pool, so roughly 1.1751996e+73 pools.

    2. Re:Cubic gigaparsec ... by RelaxedTension · · Score: 5, Funny

      With these kind of huge sizes, I think it's more like a gigabuttload, or as the layman would say, a Kardashian.

    3. Re: Cubic gigaparsec ... by buchner.johannes · · Score: 4, Informative

      Unfortunately, space is not Euclidean on giga-parsec scales. Here, when talking about 5000 Gpc, they refer to a "comoving scale". That is a scale where the expansion of the universe has been divided out, so that e.g. the same number of galaxies remain in this box. So if you would place the atoms of the number of swimming pools you computed in the volume, they would be twice as dense at the largest distances, where the Universe was half the current size. Also, the largest distance within a 5000 Gpc^3 is 3200 Gpc (space is not Euclidean).

      --
      NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
  3. I don't understand this ... by ColdWetDog · · Score: 4, Insightful

    OK, if we find a hypervelocity star and we do spectrographic analysis, etc - that can help us determine if our galaxy is similar or different from others. That's obviously neat and important.

    The bit of 'spreading life' doesn't make sense. Are these stars dragging a solar system (which might have living organisms) around with them? Is there some postulate that life comes from giant nuclear fusion balls?

    Aliens?

    --
    Faster! Faster! Faster would be better!
    1. Re:I don't understand this ... by khasim · · Score: 4, Informative

      The bit of 'spreading life' doesn't make sense.

      That's what I thought, also. Even if they were dragging planets with them (is it possible for planets to orbit that fast?) wouldn't the planets have been sterilized by the conditions at the center of whatever galaxies they came from?

      Just finding one of them should be cool enough. There's no need to postulate about "life".

    2. Re:I don't understand this ... by Anonymous Coward · · Score: 4, Interesting

      The stars' velocity relative to the bulk of matter in our galaxy doesn't change anything within its own frame of reference. It can have a perfectly happy solar system just like ours. Now - whether or not such a solar system was likely to form in the environment that flung that star out so quickly is another matter entirely, but assuming that if formed somehow, there is nothing keeping it from being stable like our solar system - until some of that hyper-velocity interstellar dust zips through and sand-blasts the bejesus out of everything.

      It would be an interesting form of "intergalactic bus" to hitch a ride on a passing star, orbit it and use its radiation (and that of the passing dust) to sustain a ship until you get wherever you're interested in going.

    3. Re:I don't understand this ... by Immerman · · Score: 4, Informative

      Relativistic effects are a non-issue because there is no preferred reference frame in the universe. Our own sun is at this very moment moving at 99.9999999% of lightspeed, when observed from the appropriate position. When observed from there the relativistic effects are quite profound, but the beauty of relativistic effects is that their existence is entirely dependent upon the observer's frame of reference - a thousand different observers on a thousand different relativistic trajectories will see a thousand different sets of relativistic effects on us, and yet we, in a more local frame of reference see virtually none. And every one of those thousands of different observations are all mathematically equivalent.

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
    4. Re:I don't understand this ... by Immerman · · Score: 4, Interesting

      >You seem to forget the newton laws and the star only travels around 1/3rd of light speed

      Relative to what, the galactic core? Why is that special, it's just an arbitrary point in space? Remember, relativity means everything in the universe is moving at 99.9999999999999999999999999% of light speed, when seen from the right inertial reference frame.

      As for how they could spread life - that should be obvious. If there's life on a planet around the star, something will probably survive the still-ridiculously-long journey across intergalactic space, the only plausible way anything could. That would afford sufficiently patient intelligent species a vehicle to travel to new galaxies, as well as performing non-sentient panspermia on an intergalactic scale. And as it passes through a new galaxy that planet is going to be sandblasted by the interstellar medium, leaving a wake of life-bearing ejecta behind it. And given the rogue star's highly atypical path a lot of stars will very quickly pass through that cloud, depositing that life on their own planets, where it could potentially take root. And conversely, if it passes near a life-bearing normal star, that same "sandblasting" will be depositing any lifebearing ejecta on its planets, giving even lifeless worlds a chance of hosting vibrant ecologies by the time the next galaxy is encountered.

      Due to the relative velocities involved it actually requires life to survive far less time space than in a traditional interstellar panspermia scenario, though the odds of a successful "seeding" are probably still lower than in a merely interplanetary seeding within the same star system - which is beginning to seem almost inevitable with what we know of the physics of asteroid impacts and various organisms' ability to survive in space (to say nothing of DNA and RNA, which don't necessarily need the host organism to reproduce)

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
    5. Re:I don't understand this ... by careysub · · Score: 4, Informative

      Answers to various comments/questions on this sub-thread:

      Time dilation at 1/3 c is 5.7%, quite a noticeable amount, but not remotely close to to turning billions of years into millions.

      Tidal effects are small for super-massive galactic black holes. I doubt tidal disruption of Earth-like (i.e. fairly close) orbits would occur, especially for cool M-type stars (the most common kind).

      While individual particles of cosmic dust hitting the planet at 1/3 c won't be a problem, (they will simply explode high in the upper atmosphere), the energy flux hitting the atmosphere from interstellar gas would be considerable. Average interstellar space has something like 1,000,000 hydrogen atoms per cubic meter. At 100,000 km/sec every second there would be 100,000*1,000*1,000,000= 10^14 hydrogen atoms hitting each square meter of atmosphere. The kinetic energy of those atoms would be about 1000 J, so roughly 1000 watts/m^2 of heating from interstellar hydrogen. Earth gets 1400 watts/M^2 of heat from the Sun, so it would roughly double the heating of an Earth-like world until it cleared the galaxy plane. If it ran into a denser patch (all of the region in the galactic center would be denser than the average I quoted) then the heating could be 10, 100, even 1000 times higher for a bit. I think this would cook any existing Earth-like planet.

      Once in interstellar space though the heat load would drop by a factor of 10,000 to 100,000 of the average interstellar value and would cease to be significant. From there on the planet and star system would evolve on their own, and a new biosphere could come into existence.

      --
      Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
  4. Re:Just stars or whole solar systems? by magarity · · Score: 4, Interesting

    If they have planets, of couse. And if you could intercept and move on to one of those planets, you could observe a much longer chunk of time go by in the rest of the universe. That would be fascinating for any astronomer.