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We’re taking a page from the best nature guide books and bringing you a Field Guide to Black Holes this week. Check back each day for a new page in the book.
First up? The basic black hole.
First up? The basic black hole.
A black hole is an object whose main characteristics are mass and spin. 
It also has a “surface,” called an event horizon. This boundary defines the place where an object has to go faster than light – faster than anything can go – to escape. http://go.nasa.gov/2OozGm4
It also has a “surface,” called an event horizon. This boundary defines the place where an object has to go faster than light – faster than anything can go – to escape. http://go.nasa.gov/2OozGm4
Since light can’t escape from inside a black hole, these objects can be hard to detect. But one thing black holes can’t hide is their gravity. 
They affect their environment just like any other mass in the universe.
They affect their environment just like any other mass in the universe.
For decades, scientists have tracked stars orbiting the black hole at the center of our galaxy. 
Using those observations, they’ve estimated the black hole weighs 4 million times the Sun’s mass!
Using those observations, they’ve estimated the black hole weighs 4 million times the Sun’s mass!
Black holes can also act as a lens. 
They can cause light from distant objects to bend around them. By looking for signatures of warped light, we can tell where there’s something with a lot of mass.
They can cause light from distant objects to bend around them. By looking for signatures of warped light, we can tell where there’s something with a lot of mass.
Follow us throughout the day to learn more about these basic black holes. And come back tomorrow to hear about fancier ones with accretion disks and jets — and how we detect them!
