Revealing the Mysteries of the Cosmos
Hubble continues to explore scientific frontiers. Many are still shrouded in mystery, waiting for science to explain them. The topics discussed in this section cover some of the most mysterious and fascinating phenomena in the cosmos that Hubble helps us understand: black holes, gravitational waves, gravitational lensing, and gamma-ray bursts.
What Are Black Holes?
A black hole is a region of space packed with so much matter that its own gravity prevents anything from escaping — even a ray of light. Although we can’t see a black hole, the material around it is visible. Material falling into a black hole forms a disk, similar to a whirlpool in a bathtub drain. Matter swirling around a black hole heats up and emits radiation that can be detected. Around a stellar black hole, this matter is composed of gas. Around a supermassive black hole in the center of a galaxy, the swirling disk is made not only of gas, but also of stars.
What Are Gravitational Waves?
Gravitational waves are invisible ripples in the fabric of space-time. They are caused by some of the most violent and energetic events in the universe. These include colliding black holes, collapsing stellar cores, merging neutron stars or white dwarf stars, the wobble of neutron stars that are not perfect spheres, and possibly even the remnants of gravitational radiation created by the birth of the universe. Gravitational waves travel at the speed of light (186,000 miles per second or 300,000 kilometers per second), squeezing and stretching anything in their path.
READ THE GRAVITATIONAL WAVES ARTICLE
What Is Gravitational Lensing?
When taken to the extreme, gravity can create some intriguing visual effects that Hubble’s is well suited to observing. Einstein’s general theory of relativity describes how mass concentrations distort the space around them. Strong gravitational lensing occurs when gravity from a huge amount of matter, like a cluster of galaxies, warps space-time, distorting and magnifying the light from distant galaxies that are behind it in the same line of sight. The effect is similar to that of a giant magnifying glass. It allows researchers to study the details of early galaxies too far away to be seen with current technology and telescopes.
READ THE GRAVITATIONAL LENSING ARTICLE
What Are Gamma-ray Bursts?
Discovered in the 1960s by U.S. military satellites looking for covert nuclear tests, gamma-ray bursts are short-lived explosions of gamma rays, the most energetic form of light. Lasting from a few milliseconds to several hours, they shine hundreds of times brighter than a typical supernova and about a million trillion times as bright as the Sun. Observed in distant galaxies, they are the brightest electromagnetic events known to exist in the universe. A typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime.