Stars Traveling Close To Light Speed Could Spread Life Through the Universe 184
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.
Anyone for a game of pool? (Score:5, Funny)
The stakes are stellar.
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Seriously, what if one of these stars smashed into another similar one headed right for it at relativistic speed? It would be like the Large Hadron Collider at astronomical scale. Maybe it would create a star made of Higg's Bosons or who knows what. Maybe the resulting collision would create a Black Hole so dense it would suck in the entire Universe.
Then I had another, totally different thought. Suppose one of these happened to be passing by... You could send a space ship at normal velocity up to meet it in
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A space ship will not get captured by the gravity of the star. At 0.3C, we're not getting significant relativistic effects, so it will attract just like a star would. This means that the acceleration (which isn't going to mash or spaghettify anything) is going to be just the same as what you'd get from an ordinary star, although not for long. At 0.3C, it won't be around all that long to transfer anything, and since the spaceship is pretty much motionless compared to the star it's going to attract the sh
Cubic gigaparsec ... (Score:5, Funny)
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http://www.wolframalpha.com/input/?i=number+of+olympic+swimming+pools+in+a+cubic+gigapasec
1.2×10^73
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Re: Cubic gigaparsec ... (Score:5, Informative)
Re: Cubic gigaparsec ... (Score:5, 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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3200 Gpc? Er... how's that possible in a ball of radius 14.3Gpc (4.2Gpc before counting expansion)? Unless you lost ^3 somewhere.
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See http://www.wolframalpha.com/in... [wolframalpha.com]
Re:Cubic gigaparsec ... (Score:5, Funny)
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With these kind of huge sizes, I think it's more like a gigabuttload, or as the layman would say, a Kardashian.
The Kardashian is an antiquated measurement. The Minaj is the new international measurement, equivalent to roughly 10 Kardashians.
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1 cubic parsec is (according to Google) 2.93799895 × 10^49 cubic meters. 1 Olympic-size swimming pool has 2500 cubic meters of volume. Diving, that gives 1.1751996 x 10^46 Olympic-size swimming pools.
Cubic *giga*parsec, so presumably you're off by a factor of 1e27. But what's 1e27 Olympic pools between friends...
I don't understand this ... (Score:5, 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?
Re:I don't understand this ... (Score:5, Informative)
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".
Re:I don't understand this ... (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.
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While I suppose it's possible, I find it highly unlikely that any planet forming in the environment of a supermassive black hole (amounts of radiation we can't even really fathom) would be anything but sterile.
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At least while they were there.
Then again, at the speeds these buggers are moving, they've only been free of the black hole shit for about three minutes.
But you know what they say: you can take the star out of the environment of a supermassive black hole but you can't take the environment of a supermassive black hole out of the star.
Re:I don't understand this ... (Score:4, 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.
Re:I don't understand this ... (Score:4, Informative)
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Why does a whole earth of life need to form near the black hole? The star doesn't need to bring a planet full of spores with it, just an infusion of elements that may be rare in another galaxy. The alien star might then get captured and live out its life in a benign galaxy eventually becoming a nebula full of heavy elements that will become the next star/planet system. Essentially it's bringing planetary system embryos with it*.
This thread seems caught up on the idea life being transported. Providing buildi
Re:I don't understand this ... (Score:4, Insightful)
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You seem to forget the newton laws and the star only travels around 1/3rd of light speed. Planetary live is not at all effected, it does not notice the fast movement as the reference point is the sun around they orbit.
However, how such a system should spread live is beyond me.
Re:I don't understand this ... (Score:5, 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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Let's assume that a star travelling 1/3rd the speed of light had a habitable planet on it and there was life on that planet. What would moving so fast do to the stars in the sky? Would they be blurred? Would some sections of sky be darker or lighter (or redder/bluer) than others? Would the star patterns change on a regular basis?
It might be interesting to figure this out.
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These comments remind me I'm currently reading a new sci-fi novel by Larry Niven and Greg Benford, actually two novels, "Bowl of Heaven" and its sequel, "Shipstar".. Imagine a spinning bowl that had the circumferance of somewhere close to the orbit of Venus, and being propelled by plasma from the captive star thru a knot-hole in the bowl. .. THAT could truly be called a "star-drive"... The bowl has a spin for about 8/10s of a G, and has a bunch of alien species living on it.. And as close as I can tell, as
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Re:I don't understand this ... (Score:5, 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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My understanding is the relative velocities between macro sized objects in the universe are rather small. Small enough where relativistic effects are minute. The article mentions 3% the speed of light being the high end. You would be hard pressed to find anything larger then a particle moving 99% the speed of light relative to our sun. Even these hyper-velocity stars are only 33-50% the speed of light.
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And? There doesn't have to be any sort of object at all in a location for it to be a valid reference frame. Posit the existence of a point passing our galaxy at 99% light speed - that hypothetical point is a perfectly valid inertial reference frame, and you can model our entire galaxy as though you were standing on that motionless point while our galaxy zooms past at 99%c, and while far more complicated, the math still all works out the same: You can still accurately predict the path of a baseball thrown
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And if they appear red in every direction - as is the case for anything at a distance?
Perhaps convention states a preference, but that reference frame gets no special physical significance. After all the vast majority of the universe is (presumably) invisible, forever causally isolated from us by the ever-accelerating expansion of the universe (assuming of course that FTL isn't possible). Any "average" reference frame is by it's nature limited to that tiny fraction of the universe we can see. An observer
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Relativistic speeds relative to what? The star and planets are in their own reference frame, and we're moving at 0.3C relative to them, so any problems they'd have due to relativistic motion we'd have also. As far as relativistic speeds go, its time is passing less than 5% slower, and we see it as 4.8% more massive, so for most purposes these aren't relativistic speeds.
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Such stars should be able to have planets orbiting them, since the frame of motion is relative to the star, not the rest of the universe.
Frame dragging is totally a thing.
The more interesting thing, is that for such stars, should they have planetary systems, time will be much slower for them than for the rest of the universe, due to their high velocity relative to the universe. This means that they may be billions of years old by our reckoning, but only millions of years old by their reckoning.
I think the i
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Umm, no.
0.333c give you a time dilation factor of 0.943. So for every century that passes here, 94 years and a few months will pass there.
As seen from here, of course.
As seen from there, for every century that passes, 94 years and a few months will pass here. Ain't relativity grand?
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tl;dr version:
Time dilation is a hyperbolic curve. The fun stuff doesn't start showing up until you get VERY near the speed of light.
For the math purists, forgive me if "hyperbolic" is the wrong term. The active ingredient is something like 1/(c**2 - v**2)
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Don't you mean time will be much slower for the rest of the universe, which is zooming by at close to light speed while the rogue star stands still? Relativity works both ways after all, and at least for non-accelerating motion the effects are basically entirely observer-dependent.
The sky would only change much while passing through a galaxy, and even then not all thatquickly. Consider - even traveling at 99% lightspeed, if they passed perpendicularly halfway between us and Alpha Centauri, it's only seeing
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Now how would this effect multiple generations of explorers on a planet orbiting a hypervelocity star?
Re:I don't understand this ... (Score:5, 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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Fast? From the viewpoint of orbiting planets, the star is at rest and it's the rest of the universe that's moving.
Even if they weren't, any lifeform that somehow leaves its home planet is unlikely to survive hitting another at 100,000 km/s. Unless our yellow star gives it new superpowers as plot demands, o
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I would be a bit curious about how livable such planets would be. Space is pretty empty; but not entirely so; and if you are travelling at those sorts of speeds relative to the almost-nothing, you'll be running into hydrogen atoms and dust specks and things fast enough that the experience will be s
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Well, we're already basically standing downrange of a particle accelerator as it is - we're constantly bombarded by intergalactic high energy particles traveling at insane fractions of lightspeed. It's not going to matter much if your planet is moving at 0.9c when you get hit by something moving at 0.9999999c. We've recorded impacts of single electrons with as much mass-energy as an entire iron atom, and that's just the impacts that have hit the miniscule portion of the planet on which we have built detec
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Just a guess here...
Take it back a step. Say one galaxy is super dense and has lots of supernovas. It's stars would be full of heavier elements essential for life. If one of these stars gets flung into a diffuse galaxy and gets captured it would be providing the elements that are unlikely to form on their own in that area. Eventually it would burn up and provide the basis for a new solar system so no need to BYOPlanets! It would seem the odds are small but the universe is a big place...
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TFA says, they can spread life "beyond the boundaries of their host galaxies"
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I can maybe see the life evolving in one of these solar systems after it leaves the black hole area, presuming the atmospheres of planets aren't scoured away by high-speed interactions with the interstellar medium.
However, how could this life "spread"? I don't see how you slow down any complex molecules from these speeds without totally incinerating them.
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Are these stars dragging a solar system (which might have living organisms) around with them?
Entourage! Fanatics! Paparazzi! Yes, they follow the stars, but I'm not sure its necessarily "life."
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> Is there some postulate that life comes from giant nuclear fusion balls?
Umm, yeah, that's kind of the default assumption, isn't it? Big ball of fusion, plus orbiting rocky bits coalesced from heavier elements, plus a few other key ingredients and voila! Life maybe happens. We're not really clear on the details yet, but the only other explanation involves some timeless dude with a long white beard waving a magic wand around, so most rational people give the benefit of the doubt to the former explanatio
Just stars or whole solar systems? (Score:2)
Do the stars drag planets along with them at those speeds?
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Yes, that is a principal of relativity: all inertial frames are equivalent.
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I think that you are right. A system moving close to C will be as stable as a system stationary relative to the distant background. However, the interaction which causes such a system to accelerate to C would destroy most fragile structures, likely including most planetary orbits.
Re:Just stars or whole solar systems? (Score:5, 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.
Title (Score:2)
How is a third of the speed of light considered "close to the speed of light"?
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Well, how close've yoouu got, huh?
Re:Title (Score:4, 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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If you were moving at 1/3 the speed of light, you are approximately 6% shorter than you were in a rest frame. (To an outside observer? I am never sure if I have this stuff right because it's totally impossible for me to demonstrate with an experiment. For a thought experiment, inside of your frame of reference you wouldn't be able to tell because your measuring devices would experience the same transformation.)
If you were at 2/3 the speed of light, you would be about 34.1% shorter. This is length contra
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And I have made a basic error of assuming that 1.0 = 100% (gamma where relativity has no effect) means 1.06-1.0 = 6% (effect of reduction is 6%.)
To understand the mistake, explain what happens when Gamma is 2.0... I'll give you a hint, it doesn't mean that you are now 100% shorter than you were.
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That's like saying the 33% I got on my math exam was actually very close to 100%.
If by very close you mean not close at all, then yes, you are right, 33% is very close to 100%.
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Actually, it's *far* worse than that. Until you hit about 80% of lightspeed you're hardly seeing any relativistic effects at all, and you've got to be well into the nineties before relativity starts getting dramatic. The difference in kinetic energy between a dead standstill and 80% of lightspeed is completely negligible compared to the difference between 95% and 96%.
It's like saying the 33% on your exam very close to 100%, if you would have gotten a 90% just for spelling your name correctly.
Then again w
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Iain Banks got there first (Score:2, Interesting)
Great book set in a planetary system orbitting one of these stars: Against a Dark Background
http://en.wikipedia.org/wiki/Against_a_Dark_Background
Life? (Score:2)
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Silly human, there's no sound in space.
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Yeah, I'd like to see some matter from that star or system interact with something else at "normal" galactic speeds. That would be awesome, space opera stuff a la Doc Smith. A meteor or asteroid at 1/3rd c? Randall Munroe should look into this.
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Well in all fairness, if you get hit by a star you probably aren't going to care how fast it was going...
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At a distance of multiple light years? Can we even detect the CMEs from Alpha Centauri? Sure, an extra 33%c would boost the energies significantly, but at that distance the ejection would be so diffuse that I suspect it would be completely lost in the continuous background hail of charged particles already hitting us at only tiny fractions of a percent under lightspeed.
Sexism tags (Score:3, Insightful)
Why the "notsexist" and "!sexist" tags for this article?
I read the summary a couple of times ( yes, I really did! I dont care if you dont believe me ), and I am struggling to find any sexism or innuendo.
Whats the deal?
Is it because of the word "these", or the word "entirely" ?
Or is it because of the sentence "That's more than a third of the speed of light." ?
Its getting really hard to tell these days whats sexist and what isnt, so if somebody could shed some light on this, it would be greatly appreciated.
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Why the "notsexist" and "!sexist" tags for this article?
I read the summary a couple of times ( yes, I really did! I dont care if you dont believe me ), and I am struggling to find any sexism or innuendo.
Whats the deal?
Whadyamean, what's the deal? There's no sexism or innuendo, so it's not sexist. See?
Like how you're supposed to announce yourself as "not a paedophile" when going to the pool. Right?
Its getting really hard to tell these days whats sexist and what isnt
That's why we have the tags. This story is simply not sexist.
I think it should also be on record that it's not racist, just in case, but I guess we're expected to figure that out for ourselves.
How is "more than a third" (Score:2)
Stars approaching at the speed of light... (Score:3)
Bet you never saw that coming.
pathetic humans (Score:2, Funny)
" ... they could also be responsible for spreading life throughout the cosmos."
You humans are so self-centered. You think that because you are 'alive' according to your way of thinking, that being alive is ideal. Anything that 'spreads life' is a good thing.
Well, guess what? Some of us who are not so limited in our thinking happen to believe that your idea of life is erroneous. You fail to consider that you are only the poor expression of a nearly perfect DNA molecule. Your purpose is to continue to propaga
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Woooosh...
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If that's what it takes to make me 'happy', thanks - but I'll stick with the peyote.
Are there really so many of these? (Score:2)
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A cubic gigaparsec is a cube with an edge of 3.26 * 10^9 light years. Or roughly a volume of 3.46 * 10^28 cubic light years.
By your own admission, the galaxy is 15 orders of magnitude smaller than a gigaparsec (disclaimer, I haven't checked your number).
If there are 10^5 hypervelocity stars in a cubic gigaparsec, then there is roughly a 10^-10 chance of one of them being inside the Milky Way. That's .00000001% probability.
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No problem. As another calibration tool, consider that the radius of the *CURRENTLY VISIBLE* universe is roughly 5 gigaparsecs.
Energy Requirements (Score:2)
Or maybe... (Score:2)
Or maybe life is just an inevitable outcome when the right conditions are met? Why science has such a hardon for panspermia is beyond me.
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Because a lot of folks are hoping that there is somebody/thing out there that's smarter than we are. These supreme beings / aliens / Progenitors or someone very much like them will one day wander by and get us out of the intractable mess we've seemed to create for ourselves.
The logical problem with this is just that if we came from 'them', 'they' might be just as screwed up as we are.
And that's not a very comforting thought.
Re:Or maybe... (Score:4, 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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Starship... Star-ship (Score:3)
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The problem is, in order to orbit the hyper-velocity star or land on one of its planets you need to first achieve hyper-velocity yourself. If you can do that, do you really need the star?
Leeloo Dallas Multipass (Score:2)
Lightspeed relative to what? (Score:2)
I see they finally found that absolute point in the universe that does not move.
A plausible method of intergalactic travel? (Score:2)
If you could accelerate an interstellar ship enough the intercept one of these exiting stars, you could orbit it and use it's radiation to sustain the colony. Eventually, the colony could reach another galaxy.
Of course, this assumes building and accelerating an interstellar ship to c/3 is feasible, which is still a bit of a stretch, though not impossible.
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The star would see the rest of the galaxy as moving slower than it should, to just the same degree that the galaxy would see the star moving slow than it otherwise should.
Each party would see the other as moving with a slower measure of time than itself.
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Well, yeah, but you would also have the rest of the universe rushing at you, and you would be saying "ah, so that's where we're going!"
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Wrong. If that were the case then all the stars in the universe would gradually slow down to "absolute zero speed" (a nonsensical term according to Special Relativity) and condense into a single supermassive black hole.
What actually happens is that the star expells the photons away with the same force in every direction, resulting in no net acceleration, and it's simply the rest of the universe that sees them as bluer (higher energy, as observed from an approaching reference frame) or redder (lower energy,
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You are right. And I actually just explained it, though perhaps not well.
What happens is that if you fire a photon "forward" it still travels it light speed, but it's waveform gets compressed, converting the kinetic energy of the star into kinetic energy of the photon: that compressed waveform translates to a higher frequency, and thus higher energy, and makes the light appear bluer* (aka blueshift). The speed is the same, but the mass (energy) is greater.
The exact opposite thing happens to a photon fired
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Those stars are stationary.
We're moving at a third of the speed of light.
No wonder I'm so tired all the time.
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Nah man. They're out cruising, but their guns couldn't take the heat, reducing them to just yelling and making rude gestures.
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Yes, and the "other body" in question here is likely the center of mass of other galaxies in the local cluster. Among which there's definitely some variation in speed, but I don't believe anything on a relativistic scale.