# Two black holes on collision course! Double trouble? **URL:** \ **Category:** Factual Questions\ **Created:** [November 20, 2002, 11:36pm UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822 "2002-11-20T23:36:11Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![buzzz\_kill](https://avatars.discourse-cdn.com/v4/letter/b/439d5e/32.png) [@buzzz\_kill](https://boards.straightdope.com/u/buzzz_kill)\ **Post date:** [November 20, 2002, 11:36pm UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/1 "2002-11-20T23:36:11Z")
NASA’s Chandra X-ray Observatory’s Astronomers have found two super massive black holes orbiting each other. They are on an inevitable collision course. _(don’t worry, for several hundred million years)_ Will the new super, super massive black hole’s mass equal the sum of the two pre-collision? Has there been any evidence pointing to this event ever occurring in the past? ================================================== [http://chandra.harvard.edu/press/02\_releases/press\_111902.html](http://chandra.harvard.edu/press/02_releases/press_111902.html) ================================================== ---
**Author:** ![username\_for\_rent](https://avatars.discourse-cdn.com/v4/letter/u/ea5d25/32.png) [@username\_for\_rent](https://boards.straightdope.com/u/username_for_rent)\ **Post date:** [November 20, 2002, 11:50pm UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/2 "2002-11-20T23:50:31Z")
[1994 maybe?](http://archive.ncsa.uiuc.edu/SCMS/DigLib/text/astro/Colliding-Black-Holes-Seidel.html). ---
**Author:** ![SlickRoenick](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@SlickRoenick](https://boards.straightdope.com/u/SlickRoenick)\ **Post date:** [November 21, 2002, 12:40am UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/3 "2002-11-21T00:40:11Z")
> [@](#): > > \*Originally posted by buzzz\_kill \* > \*\*They are on an inevitable collision course. _(don’t worry, for several hundred million years)_ \*\* Guess we should start packing up our bags and leaving. ---
**Author:** ![NardoPolo](https://avatars.discourse-cdn.com/v4/letter/n/ecae2f/32.png) [@NardoPolo](https://boards.straightdope.com/u/NardoPolo)\ **Post date:** [November 21, 2002, 1:56am UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/4 "2002-11-21T01:56:35Z")
Depends on how you look at it. My interpretation is they already merged, we just haven’t seen the effects yet. The galaxy is 400 million light-years away, and we should see the results from here in 100 million years. Thus, it seems they would have merged 300 million years ago, roughly speaking. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 21, 2002, 5:54am UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/5 "2002-11-21T05:54:59Z")
I think this is the first time a black hole pair has been discovered. On the other hand, binary neutron stars have been observed for a long time and their orbital period is decreasing at a measurable rate. The decrease rate fits the predictions of general relativity, so it’s a very convincing proof that binary systems lose energy by radiating gravitational waves. As they get closer, the rate of energy loss increases exponentially. In the last few seconds before collision it will emit a stronger gravitational wave than anything else in the unvierse. I haven’t seen the number for black hole collisions, but for neutron star collisions, our current technology can detect one tens of millions of light-years away. In 10 years we should be able to detect one over a billion light-years away. We think about 10 neutron star collisions happen every year within that distance. ---
**Author:** ![Milton\_De\_La\_Warre](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Milton\_De\_La\_Warre](https://boards.straightdope.com/u/Milton_De_La_Warre)\ **Post date:** [November 21, 2002, 1:01pm UTC](https://boards.straightdope.com/t/two-black-holes-on-collision-course-double-trouble/137822/6 "2002-11-21T13:01:51Z")
So what happens when the waves or whatever reach the earth? Would we notice anything? Does the effect decrease over distance?