3 ms·

Well, we're getting photons and probably cosmic rays from Sagittarius A, so not that unlikely. :-) You're right about small mass but macroscopic objects though

Well, we're getting photons and probably cosmic rays from Sagittarius A, so not that unlikely. :-) You're right about small mass but macroscopic objects though, since Sag A's rotation is very sub-extremal, its mass is sufficiently high (higher mass means less curvature just outside the horizon), and its accretion structures and jets are sufficiently dim that there is essentially no chance for a rocky object to get any sort of gravity assist, much less to relativistic speeds. Much smaller black holes are likely sources of "dangerous" gravity assists, but they also usually have accretion structures whose ICS-boosted radiation would probably disintegrate candidate objects. On the other hand, even a fairly small chunk of rock boosted to near the speed of light would pretty much end Earth. (Time to dig up https://what-if.xkcd.com/1/ https://what-if.xkcd.com/1/ :) )

mirimir 11y ago
Yes, I get that Sag A is pretty quiet. But there was an X-ray flash about 60 years ago, based on echos seen in Chandra images. Also, there is this: http://www.space.com/19748-hypervelocity-stars-milky-way.html http://www.space.com/19748-hypervelocity-stars-milky-way.htm... The impact description in Killing Star is similar to xkcd's, for what it's worth.
- raattgift 11y ago
  "up to 2 million miles per hour" is pretty slow compared to the speed of light :-) These stars are in Kepler orbits so the speed tells us the relationship between their mass and the central mass. We can also use their periastrons to trace out the minimal radius of the central mass. Whatever's there is almost certainly a supermassive black hole. Gas or dust or a swarm of smaller black holes in the same radius would undergo gravitational collapse (and light up LIGO! and probably put out a lot of electomagnetic radiation too... but Sag A* is not very bright). The UCLA Galactic Centre Group has a bunch of cool information about this sort of thing. You might enjoy: http://www.galacticcenter.astro.ucla.edu/animations.html http://www.galacticcenter.astro.ucla.edu/animations.html

mirimir 11y ago

Yes, I get that Sag A is pretty quiet. But there was an X-ray flash about 60 years ago, based on echos seen in Chandra images. Also, there is this: http://www.space.com/19748-hypervelocity-stars-milky-way.html http://www.space.com/19748-hypervelocity-stars-milky-way.htm... The impact description in Killing Star is similar to xkcd's, for what it's worth.

raattgift 11y ago
"up to 2 million miles per hour" is pretty slow compared to the speed of light :-) These stars are in Kepler orbits so the speed tells us the relationship between their mass and the central mass. We can also use their periastrons to trace out the minimal radius of the central mass. Whatever's there is almost certainly a supermassive black hole. Gas or dust or a swarm of smaller black holes in the same radius would undergo gravitational collapse (and light up LIGO! and probably put out a lot of electomagnetic radiation too... but Sag A* is not very bright). The UCLA Galactic Centre Group has a bunch of cool information about this sort of thing. You might enjoy: http://www.galacticcenter.astro.ucla.edu/animations.html http://www.galacticcenter.astro.ucla.edu/animations.html