# Tag: astrophysics

## astrophysics – Do “almost black holes” exist?

The Question : 72 people think this question is useful The only things I read about so far in astrophysics are either black holes, developing black holes or not black holes at all. So I am wondering, is it physically possible to have an object that is almost a black hole, but not a black

## thermodynamics – What is the speed of sound in space?

The Question : 92 people think this question is useful Given that space is not a perfect vacuum, what is the speed of sound therein? Google was not very helpful in this regard, as the only answer I found was $300\,{\rm km}\,{\rm s}^{-1}$, from Astronomy Cafe, which is not a source I’d be willing to

## astrophysics – How can a black hole produce sound?

The Question : 95 people think this question is useful I was reading this article from NASA — it’s NASA — and literally found myself perplexed. The article describes the discovery that black holes emit a “note” that has physical ramifications on the detritus around it. Sept. 9, 2003: Astronomers using NASA’s Chandra X-ray Observatory