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Fraser
2006-Oct-06, 07:18 PM
Ever wonder how many black holes are nearby? Well, NASA has gone and counted them for you. According to data gathered by NASA's Swift satellite, there are about 200 supermassive black holes within about 400 million light-years of the Earth. Swift's first job is to scan the skies for gamma ray bursts, but during downtime, the spacecraft hunts for objects that emit X-rays. And supermassive black holes are one of the most powerful sources of X-rays out there.

Read the full blog entry (http://www.universetoday.com/2006/10/06/survey-of-nearby-black-holes/)

antoniseb
2006-Oct-06, 10:56 PM
This is a nice side benefit of Swift. Having a census of these things is a good start toward understanding more about them, and eventually how they formed.

BigDon
2006-Oct-06, 11:41 PM
What about the smaller ones inside our own galaxy? I'd be more interested in those. Are they too hard to see?

GBendt
2006-Oct-08, 01:17 PM
When reading that NASA is trying to count nearby Black Holes, I expect that they mean to count the lots of Black Holes which ought to exist in our galaxy, and not those supermassive ones which are known to exist within the core of almost every large galaxy. Thus, NASA has counted Black Holes that are well known, and the information it gives provides nothing new.
If we knew the number of small Black Holes in our galaxy, we should be able to compare this number to the number of massive hot stars known to exist today, which usually end in type II supernova. Such, we might be able to come to a sound guess on how many supernovae produce a Black Hole, and how many produce a neutron star.

So we still have to look forward to this information becoming available.

Regards

Günther

madman
2006-Oct-10, 03:30 PM
there seem to be a lot of point sources in the background.

see attached images.

wasn't there a diffuse xray background that was finally resolved as point sources...and are these it/them?

Sagantool
2006-Dec-29, 10:29 PM
Just wondering how our local space environment may change if our galaxies central black hole one day became active again?

Thanks!

snabald
2006-Dec-29, 11:55 PM
Just wondering how our local space environment may change if our galaxies central black hole one day became active again?

Thanks!

I'm pretty sure Sagittarius A* is quite active.

Sagantool
2007-Jan-06, 03:44 PM
I'm pretty sure Sagittarius A* is quite active.

"Our galaxy’s central black hole is dormant, and this and similar black holes are not included in the Swift census." - this quote comes from the Blog we are commenting on: Survey of Nearby Black Holes

In addition, within Michio Kaku's "Parallel Worlds" he states "...the black hole (SagA*) in our backyard is rather quiescent at present" page 124

as an interesting note "if not for (the dust cloud between us and SagA*), a huge fireball would be visible to us on Earth every night... and would probably outshine the moon" pg 124 also