It's funny how every time I read an astronomy headline mention the word "visible", my brain immediately interprets it as a conventional photograph and is slightly disappointed when there isn't one.
The actual preprint on arxiv.org is here:<p><a href="https://arxiv.org/abs/2002.02341" rel="nofollow">https://arxiv.org/abs/2002.02341</a>
But what is the fastest known UNBOUND star that does NOT orbit a black hole? As of November 2019, it was S5-HVS1. Its speed is over 1,700 km/s or 1,056 mi/s. That's about 0.57% of light speed. S5-HVS1 will be flicked out of the Milky Way. The previous record-holder was US708, a white dwarf travelling at 1,200 km/s or 746 mi/s.
I find it really fascinating to think that when 60 minutes pass on star S62, on Earth 100 minutes would have passed in the same duration. This is Sci-Fi territory in my mind. I am having all sorts of difficulty imagining some implications of this.<p>Does this roughly mean, things are "sped up" in S62 from our point of view, if we could observe some activity on that star?
So if Copernicus and Einstein were drinking coffee with Galileo and Hawking on a little planet orbiting this star, trying to formulate an Alpha Sagittaricentric model of the galaxy, how much would Einstein and Hawking be contributing to the conversation? How important is relativity to explaining what they would be observing of the light from other stars?
Speaking of moving fast, is there anything in physics that limits how fast things are moving in space? I don't mean the limit of speed (that is already known) but realistically, how likely is there to exist, say, a tiny, fist-sized asteroid moving at a slightly sub-luminal speed? Say, 0.9997C in our frame of reference? And if such a thing were to exist, what would the consequences of it colliding with the Earth be? For the reference, an US quarter coin traveling at that speed has relativistic kinetic energy of 4.85MT TNT. We obviously wouldn't be able to detect an object moving this fast, but how likely is it to be out there?
If you were to look at this star in it's peak velocity relative to a stationary observer, you would see a pretty big shift in it's color!<p>Say the star was our sun, with a peak frequency at ~525nm. For reference, that's a good solid green, like that of fresh wet grass. If the star were moving away from you at 0.08c, then the color would redshift down to 569nm, a nice pale lime. If the star were moving toward you, then it would blueshift up to 481nm, an ultramarine blue. You can see the colors by wavelength here:<p><a href="http://pages.cs.wisc.edu/~yetkin/code/wavelength_to_rgb/wavelength.html" rel="nofollow">http://pages.cs.wisc.edu/~yetkin/code/wavelength_to_rgb/wave...</a>
> <i>In 2018, S2 made its closest approach to the black hole, giving us a chance to observe an effect of relativity known as gravitational redshift.</i><p>The reality seems more complicated because the star speeds up at the closest approach. When it speeds up, it is subject to time dilation. Time slows down more as it speeds up, and so any electromagnetic waves emitted by the body will have a lower frequency.<p>The effect of the speed up is not separable from the fact that it has dunked deeper into the gravitational field of the black hole, which also contributes time dilation.<p>> <i>If you shine a beam of light into the sky, the light doesn't slow down, but gravity does take away some of its energy.</i><p>The red shift that we see is purely a time dilation effect. So that is to say, if there were, say, a 101.5 Mhz radio station on that star, we would see that at a lower Mhz figure purely due to the oscillator of that station appearing to be slower due to time dilation. Someone riding that star, clapping their hands once per second might look like they are clapping once every 1.2 seconds.<p>The beam of light which is conveying to us the events from a source cannot alter the frequency of those events, even if it changes speed along the way. If we see 1000 events per second, then it means the source is generating 1000 events per second, according to our frame of reference. It cannot be that the source is generating 1200, but then the light somehow subtracts from that due to losing energy while escaping gravity.
> <i>If you shine a beam of light into the sky, the light doesn't slow down, but gravity does take away some of its energy. As a result, a beam of light becomes redshifted as it climbs out of a gravitational well.</i><p>This is not true; or at least not that simple.<p>Under general relativity, the speed of light is c only locally. A remote observer can see a slowed down light.<p>It doesn't make sense that light could be <i>bent</i> by gravity, but not slowed down; and then there is the business of light not being able to escape from black holes.<p><a href="https://physics.stackexchange.com/questions/59502/does-gravity-slow-the-speed-that-light-travels" rel="nofollow">https://physics.stackexchange.com/questions/59502/does-gravi...</a>
I'm curious - is this star likely to be "eaten" in the near future, and when something like that happens, could it potentially create a dangerous gamma ray burst or something?<p>I think I've read something about how the Milky Way's central black hole is unusually quiet, and speculation whether that was a prerequisite for life to develop.
The article's title is somewhat misleading. The warping of spacetime that this star is making visible is not the warping due to the star itself; it is the warping due to the huge black hole at the center of our galaxy that the star is orbiting.
There are surely red/yellow dwarf stars even closer to the black hole (beyond our observational capability). The skies on their planets would be fascinating (but hostile to life).
Blogspam (but with worse editing) of <a href="https://phys.org/news/2020-08-fastest-star.html" rel="nofollow">https://phys.org/news/2020-08-fastest-star.html</a>
> spacetime<p>Abstract theoretical concepts do not exist outside sectarian consensus.<p>This phrase is equivalent of saying like 'numbers became longer' or similar nonsense.