# Detecting Black Holes

**URL:** <https://boards.straightdope.com/t/detecting-black-holes/68516>\
**Category:** Factual Questions\
**Created:** [June 12, 2001, 7:23am UTC](https://boards.straightdope.com/t/detecting-black-holes/68516 "2001-06-12T07:23:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Ell](https://avatars.discourse-cdn.com/v4/letter/e/e47774/32.png) [@Ell](https://boards.straightdope.com/u/Ell)\
**Post date:** [June 12, 2001, 7:23am UTC](https://boards.straightdope.com/t/detecting-black-holes/68516/1 "2001-06-12T07:23:57Z")

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What are all the ways that black holes can be detected?

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**Author:** ![Fern\_Forest](https://avatars.discourse-cdn.com/v4/letter/f/71c47a/32.png) [@Fern\_Forest](https://boards.straightdope.com/u/Fern_Forest)\
**Post date:** [June 12, 2001, 7:58am UTC](https://boards.straightdope.com/t/detecting-black-holes/68516/2 "2001-06-12T07:58:21Z")

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1. It can act like a lens making the objects behind it warped.
2. We can look at objects orbiting it, calculate it’s mass and not that no known object can be that small yet have such a large mass
3. We can detect x-rays eminating from the super hot material orbiting it.  
… There may be more

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**Author:** ![Fern\_Forest](https://avatars.discourse-cdn.com/v4/letter/f/71c47a/32.png) [@Fern\_Forest](https://boards.straightdope.com/u/Fern_Forest)\
**Post date:** [June 12, 2001, 8:00am UTC](https://boards.straightdope.com/t/detecting-black-holes/68516/3 "2001-06-12T08:00:22Z")

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I’ll rewrite two since it has an typo and is uncomprehensible with it.

1. We can look at objects orbiting it notice how quickly it revolves around the central object. Calculate the mass of the central object and note that no known object can be that small yet have such a large mass