Cosmos
From the Cosmos newsroom.
A black hole represents one of the universe’s most enigmatic and powerful phenomena.
New black holes are formed when massive stars exhaust their nuclear fuel and collapse under their own gravity. This process condenses a star’s mass into an incredibly small area, creating a point in space where the gravitational pull is so powerful that nothing, not even light, can escape. Hence the name “black hole.”
The “event horizon” of a black hole is, essentially its boundary, where the velocity you’d need to escape from its gravity equals the speed of light.
Black holes come in different sizes. Stellar-mass black holes, formed by the gravitational collapse of a single star, are typically a few to 100 times more massive than our Sun.
On the other end of the spectrum are supermassive black holes, which reside at the centres of galaxies, including our own Milky Way. These can contain the mass of millions or even billions of Suns. Scientists are still not sure how these black holes form.
The supermassive black hole at the centre of our galaxy, known as Sagittarius A*, has a mass around 4 million times that of the Sun, with an event horizon radius about 17 times wider than the Sun.
Debunking black hole myths
Black holes are not just spaces of empty darkness; they can emit significant amounts of radiation as matter falls into them. This occurs outside the event horizon, in the accretion disc – a ring of matter caught in the black hole’s gravity and heated to extremely high temperatures, emitting x-rays and gamma rays.
This debunks the myth that black holes are cosmic vacuums sucking in everything within their reach – if they were, they’d gobble up the accretion disc’s radiation too. The truth is far subtler: if the Sun were replaced by a black hole of the same mass, Earth’s orbit would be unchanged. To be “sucked” in, an object must cross the event horizon.
Another common myth is that black holes are portals to other universes or dimensions. While science fiction often uses black holes as narrative devices for interstellar travel or portals, there is no scientific evidence to support such theories.
According to general relativity, the centre of a black hole, known as the singularity, is where density becomes infinite, and current laws of physics can no longer describe the resulting conditions.
The singularity doesn’t open a pathway to another universe. Instead, it represents a limit to our understanding of physics under extreme gravity.
Hawking radiation, named after physicist Stephen Hawking, who proposed it, is another fascinating aspect that challenges the perception of black holes as eternal, unchanging objects.
Hawking suggested that black holes emit radiation due to quantum effects near the event horizon, causing them to lose mass over astronomical timescales and eventually evaporate completely.
This quantum phenomenon illustrates that black holes are not permanent fixtures of the cosmos but rather dynamic entities subject to the laws of thermodynamics.
In summary, black holes are not the monstrous entities often depicted in pop culture but are instead key to understanding gravitational forces, the lifecycle of stars, and the universe’s most extreme conditions.
Through studying black holes, scientists hope to unravel the mysteries of gravity, quantum mechanics, and the very fabric of spacetime, reflecting their profound significance in cosmic evolution.
Cosmos is the science of everything, including black holes. Fall into more black hole reading here:
- Relive the excitement of the first black hole image
- What do black holes and dark matter have in common?
- Meet Subrahmanyan Chandrasekhar, discoverer of black holes in theory
*This article was generated by our custom AI service. Our service was built to focus on our archive of more than 15,000 factually correct science news stories and features. It also uses Open AI to help create the content. All generated content is fact checked by a trained science communicator and edited by our publishing team.
