Amazing facts about black holes

10 Amazing Facts About Black Holes

An artists illustration of the central engine of a Quasar. These “Quasi-stellar Objects” QSOs are now recognized as the super massive black holes at the center of emerging galaxies in the early Universe. (Photo Credit: NASA)
Imagine matter packed so densely that nothing can escape. Not a moon, not a planet and not even light. That’s what black holes are — a spot where gravity’s pull is huge, ending up being dangerous for anything that accidentally strays by.

But how did black holes come to be, and why are they important? Below we have 10 facts about black holes — just a few tidbits about these fascinating objects.

Fact 1: You can’t directly see a black hole.

Because a black hole is indeed “black” — no light can escape from it — it’s impossible for us to sense the hole directly through our instruments, no matter what kind of electromagnetic radiation you use (light, X-rays, whatever.) The key is to look at the hole’s effects on the nearby environment, points out NASA. Say a star happens to get too close to the black hole, for example. The black hole naturally pulls on the star and rips it to shreds. When the matter from the star begins to bleed toward the black hole, it gets faster, gets hotter and glows brightly in X-rays.

Fact 2: Look out! Our Milky Way likely has a black hole.

A natural next question is given how dangerous a black hole is, is Earth in any imminent danger of getting swallowed? The answer is no, astronomers say, although there is probably a huge supermassive black hole lurking in the middle of our galaxy. Luckily, we’re nowhere near this monster — we are about two-thirds of the way out from the center, relative to the rest of our galaxy — but we can certainly observe its effects from afar. For example: the European Space Agency says it’s four million times more massive than our Sun, and that it’s surrounded by surprisingly hot gas.

Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI
Fact 3: Dying stars create stellar black holes.

Say you have a star that’s about 20 times more massive than the Sun. Our Sun is going to end its life quietly; when its nuclear fuel burns out, it’ll slowly fade into a white dwarf. That’s not the case for far more massive stars. When those monsters run out of fuel, gravity will overwhelm the natural pressure the star maintains to keep its shape stable. When the pressure from nuclear reactions collapses, according to the Space Telescope Science Institute, gravity violently overwhelms and collapses the core and other layers are flung into space. This is called a supernova. The remaining core collapses into a singularity — a spot of infinite density and almost no volume. That’s another name for a black hole.

Fact 4: Black holes come in a range of sizes.

There are at least three types of black holes, NASA says, ranging from relative squeakers to those that dominate a galaxy’s center. Primordial black holes are the smallest kinds, and range in size from one atom’s size to a mountain’s mass. Stellar black holes, the most common type, are up to 20 times more massive than our own Sun and are likely sprinkled in the dozens within the Milky Way. And then there are the gargantuan ones in the centers of galaxies, called “supermassive black holes.” They’re each more than one million times more massive than the Sun. How these beasts formed is still being examined.

A binary black hole system, viewed from above. Image Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)
Fact 5: Weird time stuff happens around black holes.

This is best illustrated by one person (call them Unlucky) falling into a black hole while another person (call them Lucky) watches. From Lucky’s perspective, Unlucky’s time clock appears to be ticking slower and slower. This is in accordance with Einstein’s t