<p>There are plenty of rapidly moving objects in astrophysics. </p>

<p>A good place where one can get moving relativistically is near an event horizon of a black hole. A simple Newtonian estimate illustrates the point. Black hole has all its mass $M$ hidden under an event horizon of the radius of order $r_{g}=\dfrac{2GM}{c^2}$. An object moving circularly in the gravitational field of a black hole at the radius $\alpha r_{g}$, where $\alpha&gt;1$, would have Newtonian orbital velocity $v$ equal to $v=\sqrt{\dfrac{GM}{\alpha r_g}}=\dfrac{c}{\sqrt{2\alpha}}$. </p>

<p>This is a quilitative estimate of the velocity scale. From general relativity there are no stable circular orbits at $\alpha&lt;3$, but any body will have additional acceleration when inspiralling into the black hole. To add a bit of complexity, when one starts thinking in terms of general relativity, one has to wonder, what do we really mean by objects' velocity and about such kinds of questions.</p>

<p>Nevertheless, the above conclusion is correct: <strong>In the field of black holes intact objects can obtain relativistic velocities, which are comparable to the speed of light</strong>.</p>

<p>There are many physical examples of such systems: binary megring black holes, black holes merging with neutron stars, supermassive black holes and white dwarfs, etc. While all these systems are driven to eventual merger at relativistic velocities, it is hard for any of their components to get ejected and become free floating. To my knowledge, there are no known free floating relativistic astrophysical bodies, but some of them are indeed probably produced from the pieces of material ejected away at mildly relativistic speeds during mergers involving black holes. </p>

<p>One other rare possibility is to have a compact binary system in the field of a supermassive black hole, which is being disrupted due to interaction with it. However, the probability for such a disruption happening when the compact binary is just about to merge is vanishingly low.</p>

<p>Another ubiquitous class of objects are relativistic jets, which are ultrarelativistic streams of plasma, produced mainly when some accretion onto a black hole is taking place. Particles in such jets move at highly relativictic velocities, though the exact nature of jet formation is yet not completely understood. Finally, there is plenty of relativistic particles present in the background, such as cosmic ray particles and neutrinos. </p>

<p>One last thing to mention would be plasmas which are at relativistic temperatures (of order $10^9 K$), and which hence contain particles (mainly, electrons) moving relativistically. It is rare that plasmas get temperatures that high, but it is definitely possible during core-collapse supernova.</p>

<p>Finally, at sufficiently early stages of the Big Bang, absolutely everything in the Universe was moving relativistically!</p>

<p><strong>Edit</strong>: A few more things which came to my mind afterwards: 1) Man-made particle beams in particle accelerators are relativistic, macroscopic, but not astrophysical objects. 2) If there exists intelligent life in the Universe, it might have also produced relativistic objects of macroscopic, but again probably not astrophysical, scale (like spacecrafts).</p>

CC BY-SA 3.0
2013-11-07T20:08:53.023Z
2013-11-08T12:35:16.477Z
2013-11-08T12:35:16.477Z
Alexey Bobrick
<p>There is also another mediator particle which moves at the speed of light other than the photon. This is the <a href="http://en.wikipedia.org/wiki/Gluon" rel="nofollow">gluon</a>, which is the exchange particle for the strong force. The odd thing about the gluon is that it's never seen by itself (that is, outside of collections of other gluons).</p>

<p>Also, though neutrinos <strong>do</strong> in fact have mass, they are neutral particles. Why I'm bringing this up is because in <a href="http://en.wikipedia.org/wiki/Supernova" rel="nofollow">supernovae</a> explosions neutrinos can arrive before the photons in some circumstances - they do not interact with charged particles. Also, because they are weakly interacting particles, they pass through considerable amounts of mass (namely dust and gas) before an interaction might occur. What this means is if you could detect the neutrinos coming from a supernova it could potentially give you early warning that the photons would soon follow. This would give you time to measure its light curve (see: <a href="http://arxiv.org/abs/astro-ph/0406214" rel="nofollow">SNEWS: The SuperNova Early Warning System</a>). </p>

CC BY-SA 3.0
2016-04-03T07:48:08.240Z
The only example of detected neutrinos from a supernova had neutrino arrivals before the supernova photons. Your answer is written like this is a phenomenon that hasn't been seen yet.
ProfRob
CC BY-SA 3.0
2013-11-07T20:54:03.080Z
Good point about neutrinos! Don't forget also about gravitons, which also propagate at the speed of light with little interaction, not being particles in a common sense, though.
Alexey Bobrick
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2013-11-07T23:09:16.730Z
For that matter, beta particles outpace photons in the cooling chambers of nuclear reactors, but of course their $\gamma$s are orders of magnitude less than that of the caffeinated neutrinos :) Also, interesting link, thanks!
Manishearth
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2013-11-08T03:50:06.400Z
@Alexey Bobrick I didn't include gravitons, but you're correct, they would absolutely travel at the speed of light.
astromax
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2013-11-08T12:11:26.233Z
Sorry for a little anti-advertisement here, but I would like to underline that, being nice and interesting as a comment, this reply is not the answer to the question about the fastest moving objects in the Universe => I encourage the readers to read the other posts and the writers to think and add more on the matter: about mascrosopic, preferably astrophysical, objects, which move at relativistic velocities with respect to other macroscopic objects.
Alexey Bobrick
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2013-11-09T14:22:40.783Z
Well it depends on what he really meant by the word particle. If he meant to say macroscopic astrophysical objects then that's what he should have stated. I know he mentions comets, but he also mentions "things hurled by supernovae", which my answer is a direct response to. I agree that off topic answers must be avoided, but you also need to be careful you're not putting words in @Haaakon's mouth.
astromax
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2013-11-10T13:08:22.827Z
I meant to say "object" not "particle" in the first sentence.
astromax
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2015-06-20T17:06:51.453Z
Saying neutrinos "outpace the photons" is a little misleading, because a casual reader could think you're saying that the neutrinos are traveling faster than photons can. They _escape_ from the supernova first, yes, and are traveling fast enough that the (later-escaping) photons won't overtake them under most circumstances. (It depends on the actual velocity of the neutrinos; given enough time/travel distance, the photons should eventually overtake them...)
Peter Erwin
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2015-06-20T21:14:49.750Z
@PeterErwin Fair point about semantics. I've re-worded my answer.
astromax
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2013-11-07T20:39:52.550Z
2015-06-20T21:13:09.660Z
2015-06-20T21:13:09.660Z
astromax
<p>5/2013 I was thinking:</p>

<p>If one googles the question - you get back earth answers: cheetah, cars, airplanes.  I wanted to know in the universe.  I was thinking about the "thought experiment" of a ladder moving at light speed that contracts enough to fit into a too small garage.  I reasoned if there is NO macro mass (like a ladder)  in the universe that approaches light velocity, what is the point of the ladder thought experiment?</p>

<p>Then I read about how fast NGC 1365 is spinning:  "spinning so fast that its surface is traveling at nearly the speed of light." Press Release: 2013-07, 2/27/13 01:00:00 PM EST</p>

<p>One generally reads it would take infinite energy to move mass to the speed of light.  I've reasoned this is why one generally hears about massless particles moving at the speed of light (photons and ?).  But now we have NGC 1365 spinning at nearly the speed of light, with its two numbers of mass, and spin.  I am not sure what "nearly" is - say 90% or ?</p>

<p>Even though we are speaking about the spin speed, nonetheless at 2 million miles across, this NGC 1365 black hole with mass is assuredly the fastest velocity mass we know about in the universe, right?</p>

<p>I reason: article says "Imagine a sphere more than 2 million miles across" - this description is its diameter, D  = 2,000,000 miles or 3,218,688 km.</p>

<p>The circumference of this object is Pi x D = 3.14 x 3,281,688 km = 10,106,680.32 km.</p>

<p>The interesting question is what is it like for an object that sits on the tangent to the circumference ["circumference" means "Innermost Stable Circular Orbit", at the point in common with the line and the Innermost Stable Circular Orbit].  I lose track if this raises accuracy vs. precision?  With an object 2,000,000 miles across, is a "point" on its Innermost Stable Circular Orbit equal to a semi truck, a small car, a refrigerator, a book, marble, molecule, or atom???  </p>

<p>Whatever the size of the mass at this point, the tangent to the Innermost Stable Circular Orbit does describe an asymptote with a "macro" length.  The mass's movement along this asymptote does explain its velocity, straight line.  Hence this has got to be the highest velocity, straight line, not angular, mass we know of in the universe.  RIGHT???
Does speed angular vs. straight line matter (have effect) in a large object.  We are on a spinning planet and don't notice its speed.</p>

<p>thanks, JMc</p>

CC BY-SA 3.0
2015-06-19T17:09:36.790Z
2015-06-19T17:09:36.790Z
Julie
<p><a href="https://en.wikipedia.org/wiki/S62_(star)" rel="nofollow noreferrer">S62</a> is, according to Wikipedia, the so far closest detected star orbiting the supermassive black hole at the center of our galaxy, <a href="https://en.wikipedia.org/wiki/Sagittarius_A*" rel="nofollow noreferrer">Sagittarius A*</a>:</p>
<blockquote>
<p>At closest approach its velocity is about 0.10c (10% of the speed of light), so ~30km/s</p>
</blockquote>
<p>Arxiv paper: <a href="https://arxiv.org/abs/2002.02341" rel="nofollow noreferrer">S62 on a 9.9 yr Orbit around SgrA*</a></p>

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2021-05-24T20:27:35.883Z
2021-05-24T20:27:35.883Z
2080
<p>The fastest hypervelocity stars are supposed to go about 900km/s 2million mph 
<a href="https://www.space.com/19748-hypervelocity-stars-milky-way.html" rel="nofollow noreferrer">https://www.space.com/19748-hypervelocity-stars-milky-way.html</a></p>

<p>Quasars are an obvious example of matter with near light speed velocity.</p>

<p>When accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity.</p>

<p><a href="https://en.wikipedia.org/wiki/Astrophysical_jet" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Astrophysical_jet</a>
<a href="https://i.sstatic.net/4LQZk.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4LQZk.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2017-12-07T22:09:38.320Z
2017-12-07T22:15:37.533Z
2017-12-07T22:15:37.533Z
bandybabboon
<p>I think there was an ahem <em>ACTUAL EXPERIMENT DONE</em> ahem where two electrons were fired in the exact opposite direction and the negative charge changed to positive with same said change happening at the same time to the other electron.</p>
<p>This experiment if valid and true would mean <em>something</em> is travelling faster than the speed of light.</p>

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2024-03-29T20:12:33.663Z
This violates conservation of charge.
MiltonTheMeme
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2021-05-24T19:12:51.807Z
2021-05-24T19:12:51.807Z
Doctor Zhivago
<p>The answer to this is surprising:</p>

<p>We are.</p>

<p>And many (if not all) other galaxies.</p>

<p>And they move faster than light.</p>

<p>See, the universe is expanding, <a href="http://en.wikipedia.org/wiki/Accelerating_universe" rel="noreferrer">at an accelerating rate</a>. The fabric of spacetime itself stretches out, so that galaxies seem to move away from each other. The interesting thing is that relativity does not forbid these from moving away faster than light. While <em>local</em> space is flat and the local speed of light must be upheld, this need not hold at a global scale, so it is possible to have frames which move away from each other faster than $c$. Indeed, <a href="http://curious.astro.cornell.edu/question.php?number=575" rel="noreferrer">there are some galaxies that are moving away from us faster than light</a> (<a href="http://curious.astro.cornell.edu/question.php?number=56" rel="noreferrer">the only reason we see them is that they used to be closer and moving at a slower speed</a>). Any pair of galaxies that are 4200 Mpc away from each other (that is, with a redshift of 1.4), are moving away from each other faster than light in each other's frames (numbers stolen from the linked page).</p>

<p>Since the only consistent way to talk about motion is relative, one can say that we are moving away from other galaxies faster than light, since the reverse is also true. This can put galaxies in the bucket of the fastest moving objects in the universe. As for <em>which</em> is the fastest, I don't know, we would have to find a pair of galaxies which are the farthest apart (distance measured in the frame of the galaxy, of course), but since the universe is probably more than what we observe<sup>1</sup>, we can't pinpoint the pair of galaxies for which this is true.</p>

<hr>

<p>For those who think that it is cheating<sup>2</sup> to short-circuit the question with space expansion, there are other objects that go faster than light (they are not the fastest objects in the universe though), and these can be found on good 'ol Earth.</p>

<p><strong>Electrons</strong>:</p>

<p>In nuclear reactor cooling pools<sup>3</sup>, we have a phenomenon known as <a href="http://en.wikipedia.org/wiki/Cherenkov_radiation" rel="noreferrer">Cerenkov radiation</a>. Basically, emitted beta particles move faster than the speed of light in water. This creates an effect of similar origin as the sonic boom, where strong light emanates from the medium. </p>

<p><img src="https://i.sstatic.net/WQtF3.jpg" alt="enter image description here"></p>

<hr>

<p>Saywhat? You think I'm cheating again<sup>2</sup> by putting everything relative to the speed of light in a medium?</p>

<p>Alright, fine. Here are some fast objects that <em>don't</em> require space expansion to be fast, nor do they involve any trickery of semantics where the medium in which they are being measured is not mentioned. Many have already been mentioned by astromax.</p>

<ul>
<li><p><strong><a href="http://en.wikipedia.org/wiki/Tachyons" rel="noreferrer">Tachyons</a></strong>:These are particles which go faster than $c$ &mdash; this does not violate relativity as long as they never decelerate to subluminal speeds. However, there isn't much (any?) experimental evidence for these. A lot of BSM models do predict their existence, though. So there's still some cheating here, on to bradyonic matter:</p></li>
<li><p><strong><a href="http://en.wikipedia.org/wiki/Gluon" rel="noreferrer">Gluons</a></strong>: These are massless, and though they don't occur freely (except possibly in <a href="http://en.wikipedia.org/wiki/Glueball" rel="noreferrer">glueballs</a>, though these most probably have mass) they do travel <em>at</em> $c$. But these can't move at any other speed, so again, this is slightly cheating. On to fermionic matter:</p></li>
<li><p><strong><a href="http://en.wikipedia.org/wiki/Neutrinos" rel="noreferrer">Neutrinos</a></strong>: Now these are viable candidates. The electron neutrino is known to have very, very little mass (we have an upper bound for it, which gives ), and as a result it can easily attain very high speeds. Put it in a gravitational field, and it goes even faster. If you want macroscopic objects, however:</p></li>
<li><strong>Stuff spiraling around spinning black holes</strong>: Black holes have a strong gravitational field, and when rotating, they can impart angular momentum (lots of it) to nearby objects like accretion disks. Objects close to a black hole are accelerated to pretty high speeds. In fact, if an object is within the <a href="http://en.wikipedia.org/wiki/Ergosphere" rel="noreferrer">ergosphere</a>, it moves faster than light from the point of view of certain frames of reference.</li>
<li><strong>Stuff falling into black holes</strong>: From the faraway frame, an object speeds up and approaches the speed of light as it approaches the horizon of a black hole. Arbitrarily large speeds bounded by $c$ can be attained here.</li>
<li><strong>Black hole plasma jets</strong>: Jets being flung out of black holes can get pretty fast relative to each other.</li>
</ul>

<p><sup>1. Due to cosmic expansion, there can be galaxies that are no longer visible to us. Some galaxies may never have been visible to us, if we start watching from when galaxies started forming.</sup></p>

<p><sup>2. I, for one, agree with you.</sup></p>

<p><sup>3. And other places where you have massive particles being emitted really fast into  a medium</sup></p>

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2016-04-03T07:45:14.943Z
Extremely confusing to the casual reader, as evidenced by a question referencing this answer as evidence that particles can travel faster than the speed of light.
ProfRob
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2013-11-08T04:04:14.017Z
Nice post. A couple of things, though: 1) While galaxies may travel faster than the speed of light with respect to one another, you may want to make the distinction that this is a global (not a local) statement, 2) The actual electron neutrino (and all neutrino flavors for that matter) is not known. We may have limits on these masses, and structure in the universe would certainly look much different if they were much heavier than what people believe them to be, but that disclaimer should be present, 3) lastly, what do you mean when you say that neutrinos travel faster in a gravitational field?
astromax
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2013-11-08T04:24:26.867Z
Here's more of a discussion as to why no laws were harmed in the making of your post: http://curious.astro.cornell.edu/question.php?number=56. In summary, the reason why we can see things that are globally moving away from us faster than the speed of light is because they weren't always. While it's true that the rate of expansion between two distant points in the universe are moving faster than c (hence making them causally disconnected from the point at which they did so), that wasn't always the case in the past. We're simply seeing the lag - our cosmic monitors haven't refreshed yet.
astromax
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2013-11-08T08:54:12.237Z
@astromax Thanks for the input and the edit! (1) I _think_ I know what you mean, but could you elaborate? (2) Yes, but the upper bound is pretty tiny for $\nu_e$, so we get a rather high lower bound for avg speed. I'll edit that in though. (3) Oh, I just meant that neutrinos can be accelerated further in a gravitational field, making them even faster. (4) I mentioned that in the post ("the only reason..."), but the link is appreciated!
Manishearth
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2013-11-08T13:37:29.690Z
Well - as the previous link points out, inertial reference frames go out the window when you talk about acceleration. Locally, everybody is an inertial reference frame (and locally space is always flat - this is one of the important things about GR), so the local speed of light is always obeyed. Globally, all bets are off.
astromax
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2013-11-08T14:58:15.180Z
@astromax Ah, alright, I sort of assumed that wouldn't cause any confusion, but it's a good thing to mention. Thanks!
Manishearth
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2013-11-09T00:38:04.763Z
Well, sorry to say, but your post, being fun in itself, doesn't provide an answer to the question (yet?). The question is about astrophysical objects moving relativistically wrt other local object. It is not about particles, light propagation in medium or cosmological expansion. Just to avoid misleading the reader.
Alexey Bobrick
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2013-11-09T05:39:02.267Z
@AlexeyBobrick I personally count particles as objects, but I see what you're getting at. The "in a medium" bit was just a sideshow, really. In that case plasma jets are probably  likely answer as mentioned in your answer (I'll add it in). Not sure if we can consider jets to be an "object" though
Manishearth
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2013-11-09T11:25:38.037Z
@Manishearth: Particles are microscopic objects, that's the difference. Jets are macroscopic, the question is also about macroscopic things.
Alexey Bobrick
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2013-11-09T12:39:34.793Z
@Manishearth Great answer!!! +1
Eduardo Guerras Valera
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2013-12-07T13:59:12.840Z
Man can we exchange brains?
Junaid
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2013-11-07T23:04:54.860Z
2017-12-04T16:54:33.490Z
2017-12-04T16:54:33.490Z
Manishearth
<p>We know that nothing can have proper velocities larger than the speed of light in vacuum. But are there any objects in space that get close to it? Any comets, or other objects thrown by gravity or supernova explosions that were hurled to incredible speeds? </p>

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2015-06-19T21:40:05.827Z
Small point to add, but the fastest observed particle with mass might be this one:  https://en.wikipedia.org/wiki/Oh-My-God_particle   0.999 999 999 999 999 999 999 9951c - much faster than anything accelerated at CERN.   Neutrinos also travel close to the speed of light and they have tiny mass.   Not sure how close to c they get.
userLTK
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2015-06-19T23:13:42.837Z
Mundane, Milky-way-ocentric answer:
Fastest Star in the Galaxy Has a Strange Origin
: "*The runaway star, US 708, is traveling at 745 miles per second (1200 km/s) — that's  26 million miles per hour (43 million km/h) —making it the fastest star in the Milky Way ever clocked by astronomers, according to the new research. Its speed will allow it to escape the gravitational pull of the galaxy, and eventually make its way into intergalactic space.*" http://www.space.com/28737-fastest-star-galaxy-strange-origin.html
Wayfaring Stranger
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2013-11-07T19:54:39.717Z
"We know nothing can travel faster than light."  Do we? I've read in more than one place that Einstein's relativity prohibits accelerating to the speed of light and there are theories which permit faster than light travel provided the material never slows below the speed of light.  Of course such material would be rather exotic...
GreenMatt
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2013-11-07T20:12:04.877Z
@GreenMatt Interesting. Though it would seem discussing it would be off topic for this site
bogen
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2013-11-07T20:27:35.030Z
@Haaakon Exotic matter is theoretical, not hypothetical, and thus on topic.
called2voyage
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2013-11-09T20:15:20.957Z
@Haakon, could you please make your question specific: do you mean large enough macroscopic object, astrophysical bodies, or any types of objects in your question?
Alexey Bobrick
<gravity><universe><comets><speed>
What's the fastest moving object in the universe?
bogen
# What's the fastest moving object in the universe?

(Asked by: username_0 on 2013-11-07)

We know that nothing can have proper velocities larger than the speed of light in vacuum. But are there any objects in space that get close to it? Any comets, or other objects thrown by gravity or supernova explosions that were hurled to incredible speeds?

**Tags:** gravity, universe, comets, speed
> **Comments:**
> **username_3**: "We know nothing can travel faster than light."  Do we? I've read in more than one place that Einstein's relativity prohibits accelerating to the speed of light and there are theories which permit faster than light travel provided the material never slows below the speed of light.  Of course such material would be rather exotic...  
> **username_0**: @GreenMatt Interesting. Though it would seem discussing it would be off topic for this site  
> **username_4**: @Haaakon Exotic matter is theoretical, not hypothetical, and thus on topic.  
> **username_5**: @Haakon, could you please make your question specific: do you mean large enough macroscopic object, astrophysical bodies, or any types of objects in your question?  
> **username_1**: Small point to add, but the fastest observed particle with mass might be this one:  https://en.wikipedia.org/wiki/Oh-My-God_particle   0.999 999 999 999 999 999 999 9951c - much faster than anything accelerated at CERN.   Neutrinos also travel close to the speed of light and they have tiny mass.   Not sure how close to c they get.  
> **username_2**: Mundane, Milky-way-ocentric answer: Fastest Star in the Galaxy Has a Strange Origin : "*The runaway star, US 708, is traveling at 745 miles per second (1200 km/s) — that's  26 million miles per hour (43 million km/h) —making it the fastest star in the Milky Way ever clocked by astronomers, according to the new research. Its speed will allow it to escape the gravitational pull of the galaxy, and eventually make its way into intergalactic space.*" http://www.space.com/28737-fastest-star-galaxy-strange-origin.html  

---

## 7 answers

### Answer by username_8 on 2013-11-07. Score: 36 | Accepted answer

The answer to this is surprising:

We are.

And many (if not all) other galaxies.

And they move faster than light.

See, the universe is expanding, [at an accelerating rate](http://en.wikipedia.org/wiki/Accelerating_universe). The fabric of spacetime itself stretches out, so that galaxies seem to move away from each other. The interesting thing is that relativity does not forbid these from moving away faster than light. While *local* space is flat and the local speed of light must be upheld, this need not hold at a global scale, so it is possible to have frames which move away from each other faster than $c$. Indeed, [there are some galaxies that are moving away from us faster than light](http://curious.astro.cornell.edu/question.php?number=575) ([the only reason we see them is that they used to be closer and moving at a slower speed](http://curious.astro.cornell.edu/question.php?number=56)). Any pair of galaxies that are 4200 Mpc away from each other (that is, with a redshift of 1.4), are moving away from each other faster than light in each other's frames (numbers stolen from the linked page).

Since the only consistent way to talk about motion is relative, one can say that we are moving away from other galaxies faster than light, since the reverse is also true. This can put galaxies in the bucket of the fastest moving objects in the universe. As for *which* is the fastest, I don't know, we would have to find a pair of galaxies which are the farthest apart (distance measured in the frame of the galaxy, of course), but since the universe is probably more than what we observe1, we can't pinpoint the pair of galaxies for which this is true.

---

For those who think that it is cheating2 to short-circuit the question with space expansion, there are other objects that go faster than light (they are not the fastest objects in the universe though), and these can be found on good 'ol Earth.

**Electrons**:

In nuclear reactor cooling pools3, we have a phenomenon known as [Cerenkov radiation](http://en.wikipedia.org/wiki/Cherenkov_radiation). Basically, emitted beta particles move faster than the speed of light in water. This creates an effect of similar origin as the sonic boom, where strong light emanates from the medium.

![enter image description here](https://i.sstatic.net/WQtF3.jpg)

---

Saywhat? You think I'm cheating again2 by putting everything relative to the speed of light in a medium?

Alright, fine. Here are some fast objects that *don't* require space expansion to be fast, nor do they involve any trickery of semantics where the medium in which they are being measured is not mentioned. Many have already been mentioned by astromax.

* **[Tachyons](http://en.wikipedia.org/wiki/Tachyons)**:These are particles which go faster than $c$ — this does not violate relativity as long as they never decelerate to subluminal speeds. However, there isn't much (any?) experimental evidence for these. A lot of BSM models do predict their existence, though. So there's still some cheating here, on to bradyonic matter:
* **[Gluons](http://en.wikipedia.org/wiki/Gluon)**: These are massless, and though they don't occur freely (except possibly in [glueballs](http://en.wikipedia.org/wiki/Glueball), though these most probably have mass) they do travel *at* $c$. But these can't move at any other speed, so again, this is slightly cheating. On to fermionic matter:
* **[Neutrinos](http://en.wikipedia.org/wiki/Neutrinos)**: Now these are viable candidates. The electron neutrino is known to have very, very little mass (we have an upper bound for it, which gives ), and as a result it can easily attain very high speeds. Put it in a gravitational field, and it goes even faster. If you want macroscopic objects, however:
* **Stuff spiraling around spinning black holes**: Black holes have a strong gravitational field, and when rotating, they can impart angular momentum (lots of it) to nearby objects like accretion disks. Objects close to a black hole are accelerated to pretty high speeds. In fact, if an object is within the [ergosphere](http://en.wikipedia.org/wiki/Ergosphere), it moves faster than light from the point of view of certain frames of reference.
* **Stuff falling into black holes**: From the faraway frame, an object speeds up and approaches the speed of light as it approaches the horizon of a black hole. Arbitrarily large speeds bounded by $c$ can be attained here.
* **Black hole plasma jets**: Jets being flung out of black holes can get pretty fast relative to each other.

1. Due to cosmic expansion, there can be galaxies that are no longer visible to us. Some galaxies may never have been visible to us, if we start watching from when galaxies started forming.

2. I, for one, agree with you.

3. And other places where you have massive particles being emitted really fast into a medium

> **Comments:**
> **username_6**: Nice post. A couple of things, though: 1) While galaxies may travel faster than the speed of light with respect to one another, you may want to make the distinction that this is a global (not a local) statement, 2) The actual electron neutrino (and all neutrino flavors for that matter) is not known. We may have limits on these masses, and structure in the universe would certainly look much different if they were much heavier than what people believe them to be, but that disclaimer should be present, 3) lastly, what do you mean when you say that neutrinos travel faster in a gravitational field?  
> **username_6**: Here's more of a discussion as to why no laws were harmed in the making of your post: http://curious.astro.cornell.edu/question.php?number=56. In summary, the reason why we can see things that are globally moving away from us faster than the speed of light is because they weren't always. While it's true that the rate of expansion between two distant points in the universe are moving faster than c (hence making them causally disconnected from the point at which they did so), that wasn't always the case in the past. We're simply seeing the lag - our cosmic monitors haven't refreshed yet.  
> **username_8**: @astromax Thanks for the input and the edit! (1) I _think_ I know what you mean, but could you elaborate? (2) Yes, but the upper bound is pretty tiny for $\nu_e$, so we get a rather high lower bound for avg speed. I'll edit that in though. (3) Oh, I just meant that neutrinos can be accelerated further in a gravitational field, making them even faster. (4) I mentioned that in the post ("the only reason..."), but the link is appreciated!  
> **username_6**: Well - as the previous link points out, inertial reference frames go out the window when you talk about acceleration. Locally, everybody is an inertial reference frame (and locally space is always flat - this is one of the important things about GR), so the local speed of light is always obeyed. Globally, all bets are off.  
> **username_8**: @astromax Ah, alright, I sort of assumed that wouldn't cause any confusion, but it's a good thing to mention. Thanks!  
> **username_5**: Well, sorry to say, but your post, being fun in itself, doesn't provide an answer to the question (yet?). The question is about astrophysical objects moving relativistically wrt other local object. It is not about particles, light propagation in medium or cosmological expansion. Just to avoid misleading the reader.  
> **username_8**: @AlexeyBobrick I personally count particles as objects, but I see what you're getting at. The "in a medium" bit was just a sideshow, really. In that case plasma jets are probably  likely answer as mentioned in your answer (I'll add it in). Not sure if we can consider jets to be an "object" though  
> **username_5**: @Manishearth: Particles are microscopic objects, that's the difference. Jets are macroscopic, the question is also about macroscopic things.  
> **username_15**: @Manishearth Great answer!!! +1  
> **username_16**: Man can we exchange brains?  
> **username_7**: Extremely confusing to the casual reader, as evidenced by a question referencing this answer as evidence that particles can travel faster than the speed of light.  

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### Answer by username_6 on 2013-11-07. Score: 17

There is also another mediator particle which moves at the speed of light other than the photon. This is the [gluon](http://en.wikipedia.org/wiki/Gluon), which is the exchange particle for the strong force. The odd thing about the gluon is that it's never seen by itself (that is, outside of collections of other gluons).

Also, though neutrinos **do** in fact have mass, they are neutral particles. Why I'm bringing this up is because in [supernovae](http://en.wikipedia.org/wiki/Supernova) explosions neutrinos can arrive before the photons in some circumstances - they do not interact with charged particles. Also, because they are weakly interacting particles, they pass through considerable amounts of mass (namely dust and gas) before an interaction might occur. What this means is if you could detect the neutrinos coming from a supernova it could potentially give you early warning that the photons would soon follow. This would give you time to measure its light curve (see: [SNEWS: The SuperNova Early Warning System](http://arxiv.org/abs/astro-ph/0406214)).

> **Comments:**
> **username_5**: Good point about neutrinos! Don't forget also about gravitons, which also propagate at the speed of light with little interaction, not being particles in a common sense, though.  
> **username_8**: For that matter, beta particles outpace photons in the cooling chambers of nuclear reactors, but of course their $\gamma$s are orders of magnitude less than that of the caffeinated neutrinos :) Also, interesting link, thanks!  
> **username_6**: @Alexey Bobrick I didn't include gravitons, but you're correct, they would absolutely travel at the speed of light.  
> **username_5**: Sorry for a little anti-advertisement here, but I would like to underline that, being nice and interesting as a comment, this reply is not the answer to the question about the fastest moving objects in the Universe => I encourage the readers to read the other posts and the writers to think and add more on the matter: about mascrosopic, preferably astrophysical, objects, which move at relativistic velocities with respect to other macroscopic objects.  
> **username_6**: Well it depends on what he really meant by the word particle. If he meant to say macroscopic astrophysical objects then that's what he should have stated. I know he mentions comets, but he also mentions "things hurled by supernovae", which my answer is a direct response to. I agree that off topic answers must be avoided, but you also need to be careful you're not putting words in @Haaakon's mouth.  
> **username_6**: I meant to say "object" not "particle" in the first sentence.  
> **username_9**: Saying neutrinos "outpace the photons" is a little misleading, because a casual reader could think you're saying that the neutrinos are traveling faster than photons can. They _escape_ from the supernova first, yes, and are traveling fast enough that the (later-escaping) photons won't overtake them under most circumstances. (It depends on the actual velocity of the neutrinos; given enough time/travel distance, the photons should eventually overtake them...)  
> **username_6**: @PeterErwin Fair point about semantics. I've re-worded my answer.  
> **username_7**: The only example of detected neutrinos from a supernova had neutrino arrivals before the supernova photons. Your answer is written like this is a phenomenon that hasn't been seen yet.  

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### Answer by username_5 on 2013-11-07. Score: 14

There are plenty of rapidly moving objects in astrophysics.

A good place where one can get moving relativistically is near an event horizon of a black hole. A simple Newtonian estimate illustrates the point. Black hole has all its mass $M$ hidden under an event horizon of the radius of order $r\_{g}=\dfrac{2GM}{c^2}$. An object moving circularly in the gravitational field of a black hole at the radius $\alpha r\_{g}$, where $\alpha>1$, would have Newtonian orbital velocity $v$ equal to $v=\sqrt{\dfrac{GM}{\alpha r\_g}}=\dfrac{c}{\sqrt{2\alpha}}$.

This is a quilitative estimate of the velocity scale. From general relativity there are no stable circular orbits at $\alpha<3$, but any body will have additional acceleration when inspiralling into the black hole. To add a bit of complexity, when one starts thinking in terms of general relativity, one has to wonder, what do we really mean by objects' velocity and about such kinds of questions.

Nevertheless, the above conclusion is correct: **In the field of black holes intact objects can obtain relativistic velocities, which are comparable to the speed of light**.

There are many physical examples of such systems: binary megring black holes, black holes merging with neutron stars, supermassive black holes and white dwarfs, etc. While all these systems are driven to eventual merger at relativistic velocities, it is hard for any of their components to get ejected and become free floating. To my knowledge, there are no known free floating relativistic astrophysical bodies, but some of them are indeed probably produced from the pieces of material ejected away at mildly relativistic speeds during mergers involving black holes.

One other rare possibility is to have a compact binary system in the field of a supermassive black hole, which is being disrupted due to interaction with it. However, the probability for such a disruption happening when the compact binary is just about to merge is vanishingly low.

Another ubiquitous class of objects are relativistic jets, which are ultrarelativistic streams of plasma, produced mainly when some accretion onto a black hole is taking place. Particles in such jets move at highly relativictic velocities, though the exact nature of jet formation is yet not completely understood. Finally, there is plenty of relativistic particles present in the background, such as cosmic ray particles and neutrinos.

One last thing to mention would be plasmas which are at relativistic temperatures (of order $10^9 K$), and which hence contain particles (mainly, electrons) moving relativistically. It is rare that plasmas get temperatures that high, but it is definitely possible during core-collapse supernova.

Finally, at sufficiently early stages of the Big Bang, absolutely everything in the Universe was moving relativistically!

**Edit**: A few more things which came to my mind afterwards: 1) Man-made particle beams in particle accelerators are relativistic, macroscopic, but not astrophysical objects. 2) If there exists intelligent life in the Universe, it might have also produced relativistic objects of macroscopic, but again probably not astrophysical, scale (like spacecrafts).


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### Answer by username_10 on 2015-06-19. Score: 1

5/2013 I was thinking:

If one googles the question - you get back earth answers: cheetah, cars, airplanes. I wanted to know in the universe. I was thinking about the "thought experiment" of a ladder moving at light speed that contracts enough to fit into a too small garage. I reasoned if there is NO macro mass (like a ladder) in the universe that approaches light velocity, what is the point of the ladder thought experiment?

Then I read about how fast NGC 1365 is spinning: "spinning so fast that its surface is traveling at nearly the speed of light." Press Release: 2013-07, 2/27/13 01:00:00 PM EST

One generally reads it would take infinite energy to move mass to the speed of light. I've reasoned this is why one generally hears about massless particles moving at the speed of light (photons and ?). But now we have NGC 1365 spinning at nearly the speed of light, with its two numbers of mass, and spin. I am not sure what "nearly" is - say 90% or ?

Even though we are speaking about the spin speed, nonetheless at 2 million miles across, this NGC 1365 black hole with mass is assuredly the fastest velocity mass we know about in the universe, right?

I reason: article says "Imagine a sphere more than 2 million miles across" - this description is its diameter, D = 2,000,000 miles or 3,218,688 km.

The circumference of this object is Pi x D = 3.14 x 3,281,688 km = 10,106,680.32 km.

The interesting question is what is it like for an object that sits on the tangent to the circumference ["circumference" means "Innermost Stable Circular Orbit", at the point in common with the line and the Innermost Stable Circular Orbit]. I lose track if this raises accuracy vs. precision? With an object 2,000,000 miles across, is a "point" on its Innermost Stable Circular Orbit equal to a semi truck, a small car, a refrigerator, a book, marble, molecule, or atom???

Whatever the size of the mass at this point, the tangent to the Innermost Stable Circular Orbit does describe an asymptote with a "macro" length. The mass's movement along this asymptote does explain its velocity, straight line. Hence this has got to be the highest velocity, straight line, not angular, mass we know of in the universe. RIGHT???
Does speed angular vs. straight line matter (have effect) in a large object. We are on a spinning planet and don't notice its speed.

thanks, JMc


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### Answer by username_11 on 2021-05-24. Score: 1

[S62](https://en.wikipedia.org/wiki/S62_(star)) is, according to Wikipedia, the so far closest detected star orbiting the supermassive black hole at the center of our galaxy, [Sagittarius A\*](https://en.wikipedia.org/wiki/Sagittarius_A*):

> At closest approach its velocity is about 0.10c (10% of the speed of light), so ~30km/s

Arxiv paper: [S62 on a 9.9 yr Orbit around SgrA\*](https://arxiv.org/abs/2002.02341)


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### Answer by username_12 on 2017-12-07. Score: 1

The fastest hypervelocity stars are supposed to go about 900km/s 2million mph
<https://www.space.com/19748-hypervelocity-stars-milky-way.html>

Quasars are an obvious example of matter with near light speed velocity.

When accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity.

<https://en.wikipedia.org/wiki/Astrophysical_jet>
[![enter image description here](https://i.sstatic.net/4LQZk.jpg)](https://i.sstatic.net/4LQZk.jpg)


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### Answer by username_13 on 2021-05-24. Score: -3

I think there was an ahem *ACTUAL EXPERIMENT DONE* ahem where two electrons were fired in the exact opposite direction and the negative charge changed to positive with same said change happening at the same time to the other electron.

This experiment if valid and true would mean *something* is travelling faster than the speed of light.

> **Comments:**
> **username_14**: This violates conservation of charge.  

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