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

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

Posted by samzenpus on Monday December 1, 2014 @06:58AM 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.

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Anyone for a game of pool? by Ded+Bob · 2014-12-01 07:07 · Score: 4, Funny

The stakes are stellar.
Cubic gigaparsec ... by Mostly+a+lurker · 2014-12-01 07:11 · Score: 4, Funny

Ummm, how many Olympic sized swimming pools is that?
1. Re: Cubic gigaparsec ... by AA1 · 2014-12-01 07:19 · 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 · 2014-12-01 07:30 · 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 · 2014-12-01 09:05 · 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).
  
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I don't understand this ... by ColdWetDog · 2014-12-01 07:14 · 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?

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1. Re:I don't understand this ... by khasim · 2014-12-01 07:20 · 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 · 2014-12-01 07:37 · 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 Zocalo · 2014-12-01 07:45 · Score: 3, Insightful
  
  It's not just the radiation levels in a galactic core or the overall velocity of the star system that bothers me, we're also quite a way into the territory or relativistic speeds here so there could also be some very odd effects at different points in a planet's orbit depending on the inclination of the orbital plane to the overall direction of motion. It seems like an awfully big strech to expect even the most primitive forms of life to be able to start under those conditions, let alone survive the trip. That badly needs a justification that the paper fails to provide, unless you count a throwaway line and a couple of references, neither of which look like the would explain how life might exist under those conditions.
  
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4. Re:I don't understand this ... by Immerman · 2014-12-01 08:22 · 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.
  
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5. Re:I don't understand this ... by Immerman · 2014-12-01 08:47 · 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)
  
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6. Re:I don't understand this ... by careysub · 2014-12-01 09:12 · 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.
  
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7. Re:I don't understand this ... by buchner.johannes · 2014-12-01 09:31 · Score: 3, Interesting
  
  Not all supermassive black holes are actively accreting. In fact, the fraction of time their accretion disks actually output massive amounts of radiation is ~10%, on patches of ~ hundred million years timescales.
  A planetary system could form outside the center of the galaxy and travel close to the galactic center. You have to keep in mind that the distances between stars are enormous when compared to distances between planets. For example, our nearest star is 270 000 earth-sun distances (4 lightyears) away, while Jupiter is only 5 earth-sun distances from the Sun. So a "stripping" of planets, due to tidal forces, is extremely small, even when it comes close to the supermassive black hole in the center of the galaxy. It is true however that for the closest orbits, such as 120 earth-sun distances for S2 (S2 reaches speeds of 5000 km/s), this effect will be important. However, I suspect that while a single, quick swing-by will alter the orbits of planets (generally increasing ellipticity), that effect leads to the immediate destruction of the entire system. Normal planetary systems are also not stable systems. Changes in the orbits, interactions between planets, etc. are common; Only when stable oscillations are reached, the orbits remain the same for a few million years. So I suspect that the planets can re-arrange into a stable system (perhaps under ejection of one of the planets).
  I think the changes are better if the system is a newly born star, where planetoids are still forming in a thick disk of gas and dust. Then, the partially destroyed disk can re-arrange quickly and form planets after swing-by. That would not necessarily be a problem for "spreading of life", if this process occurs e.g. via comets.
  
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8. Re:I don't understand this ... by flyingsquid · 2014-12-01 12:54 · Score: 3, Informative
  
  OK, first of all, let's assume that the collision of two giant galactic black holes can fling stars out of the galactic center in a way that doesn't completely destroy any planetary systems within those star systems. How on earth does life get off of such a planet onto another? If a collision in the solar system were to launch a microbe-laden rock out of the star system, it's still traveling at a third of lightspeed. How do those microbes make a safe landing? For that matter, what about the planet that those microbes land on? Chicxulub is estimated to have released 100 million megatons of explosive energy, which is equivalent to giving every man woman and child on the planet a Hiroshima nuke and detonating them all at once. Now, the Chicxulub asteroid is estimated to have traveled around 20,000 km/sec. And .3 lightspeed is 100,000,000 m/sec, or about 5,000 times the speed of the Chicxulub asteroid. Since kinetic energy scales as velocity squared, we're dealing with an impact that is 25,000 Chicxulub asteroids. So imagine wiping the dinosaurs out. And then doing it again, 24,999 times. That's 2,500,000,000,000 megatons - 2.5 trillion megatons- of explosives. Even a much smaller asteroid- say, 1 km in diameter instead of 10 km- is still going to pack far more wallop than Chicxulub did, and create an extinction event. Even a single kilogram is going to come in with as much energy as a large H-bomb. My guess is that if these stars have any effect whatsoever on the evolution of life in the universe, it's probably not a terribly constructive one...
Re:Just stars or whole solar systems? by magarity · 2014-12-01 07:23 · 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.
Re:Title by crunchygranola · 2014-12-01 07:57 · Score: 3, Informative

The the term used in the paper is "semi-relativistic" - fast enough that relativistic effects cannot be ignored in even routine calculations about its properties. At 1/3 the speed of light the time dilation effect amounts to a 5.7% difference for example.
"Close to the speed of light" is the summary author's attempt to render "semi-relativistic" in sensible common place terminology.

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Re:Or maybe... by Immerman · 2014-12-01 10:33 · Score: 3, Informative

Simple - because the more we learn about just how durable some life* is, the more it seems inevitable that panspermia happens. Almost certainly between planets within the same solar system, and quite possibly between solar systems as well. Whether it finds fertile ground or not is another question. Basically, even if you assume life "just happens" on a regular basis, panspermia allows it to then spread to places far less hospitable to biogenesis. For example, we have plenty of microbes on Earth that would probably have no problem thriving on Mars, Europa, etc, even if those worlds never offer the rich organic chemical soup and high energy gradients that are probably necessary to spawn life in the first place. When we finally start doing biological studies on those planets it will be very interesting to see if life (A) exists there currently, and (B) is related to Earth life.
* not to mention pseudo-living molecules like RNA and DNA, which don't necessarily need their host organism in order to reproduce and kick-start the evolutionary cycle on a new world.
The answers to those questions may tell us a great deal about the probably ubiquity of life in the universe, and is one of the reasons we try so hard to avoid contaminating them with Earthborn life from our probes. If they spawned their own life it may be less sophisticated than what has evolved here, on our lushly energy-rich plaent, and might be completely eradicate by invasive Earth organisms before we ever have a chance to detect it, depriving us of the knowledge that life likely arises pretty much everywhere. Or alternately, if they were colonized by Earth life long ago (Or perhaps we were all colonized by Mars life - it could potentially have supported life long before the Earth cooled sufficiently), then there is much to be learned about the ways that life evolved in (almost) completely isolated ecosystems. Even if there's only microbial life to be found, the evolutionary divergence could make the Galapagos islands look like just more of the same.

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