A black hole is a region of space-time that has such a strong gravitational field that nothing, not even light, can escape it. They are created when a massive star dies and explodes as a supernova, leaving its core as either a neutron star or a black hole. Supermassive black holes are also found in the centers of galaxies. Black holes are quite common, at least more common than we thought a century ago.
I don’t know if the number of space enthusiasts working in the entertainment industry has increased or if people in general have started to like space more, but there has been a marked increase in the popularity of space-related media in the last decade. And thanks to movies like Star Trek, The Black Hole, Interstellar etc., black holes have been repeatedly featured on the big screen.
Black holes are quite an interesting ‘entity’, if one may call them that. They show some seriously mind-boggling features and since they are not ‘visible’, per se, can prove to be quite difficult to spot. Therefore, if you were to embark on a space journey in a hypothetical spacecraft that never runs out of fuel and can withstand any amount of damage, how often would you find black holes?
Before we answer that, it’s important to understand a few things…
What’s a ‘Black hole’?
The most basic way of defining a black hole would be to say that it’s a region of space-time that has such a strong gravitational field that nothing, not even light, can escape it. Since light does not escape them, black holes appear completely dark, or in effect, don’t appear at all, hence the name ‘black’ holes.
Why can’t light escape black holes?
Light travels very fast; clocking a speed of 300,000 kilometers per second (186,000 miles per second), which is no casual feat. Given that immense speed, it seems impossible to imagine something that could stop something as fast as light from escaping its grip.
Consider this: if you threw a ball hard enough to make it move at 12 kilometers per second, two things would happen: 1. the ball shall shoot into space, overcoming Earth’s gravity (because it would overcome Earth’s escape velocity of 11.2 km/s; 2. you would no longer be considered a normal human being. Likewise, the escape velocity of black holes is much greater than the speed of light, so light has a hard time leaving them.
When a massive star dies, it explodes as a supernova, leaving its core as either a neutron star or a black hole. However, these are not the only black holes. The observations of ground-based instruments and the Hubble Space Telescope have revealed the presence of unimaginably enormous supermassive black holes in the centers of galaxies that hold millions of solar-masses worth of material.
Furthermore, with our increasing information on other galaxies, scientists have also come to recognize the presence of extragalactic black holes. Furthermore, it’s believed that ‘seed’ black holes existed even before galaxies and stars were formed.
Chandra X-ray Observatory
The inception of the Chandra Observatory was a big step towards identifying and learning more about black holes. Previously referred to as the Advanced X-ray Astrophysics Facility (AXAF), it’s a space observatory that was launched by NASA in 1999. It is 100 times more sensitive to X-ray sources than anything that had previously been used, and it is one of the “Great Observatories”, which include legends like the Hubble Space Telescope, the Spitzer Space Telescope and the Compton Gamma Ray Observatory.
In 2001, it detected the first X-ray emission from a supermassive black hole called Sagittarius A, which is located in the center of our galaxy. It also confirmed the abundance of supermassive black holes in two ‘deep fields’, and indicated that these black holes had been more active in the past. It also discovered a new type of black hole in galaxy M82. The latest discovery of the observatory came in February 2016, when it recorded a jet from a very distant black hole named called B3 0727+409 that was being illuminated by the leftover glow from the Big Bang.
For more information about the Chandra Observatory and its latest findings, check out their website.
Black holes are quite common, at least more common than we thought a century ago. They may be even greater in number, but we need far more advanced space technology to get a proper ‘glimpse’ of these mysterious phenomena of our universe.
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