The Hubble telescope is 25 years old, and in that time it has revolutionized our understanding of the cosmos.
Dark of Night
When you look up in the night sky, there are areas of the sky that appear dark. That’s because there is nothing in that region bright enough for us to see with the naked eye. If you looked upon this region with a telescope, you would find dim stars and galaxies, but you would still see areas that appeared dark to you. How far could you take this? If you kept looking at smaller and smaller dark regions with ever more powerful telescopes, what would you see?
Second Look
One of the advantages of modern astronomy is that most observational data gets stored in a raw form. This is particularly true for the major space telescopes. Most of that raw data is also stored publicly, either a certain time period or even as the data is gathered. This means that long after an observation is made, people can go through the data to analyze it in new ways. As a case in point, a team recently gathered old data from the Hubble Space Telescope, and processed it using new methods.
Hubble’s Tuning Fork
Edwin Hubble is perhaps most famous for discovering a relationship between the distance of a galaxy and the speed at which a galaxy moves away from us. This relation is now known as Hubble’s Law, and is evidence for the expansion of the universe. But Hubble’s primary interest was in galactic nebulae (what we now just call galaxies).
Scale
When something is far way, it can look quite small. That is why the resolving power of your instrument is so important.
Islands in the Sky
In the 1700s, it was clear that the Messier objects such as M-31 are not stars. They are also not comets, as they they don’t move through the sky. Messier actually cataloged these objects so he wouldn’t confuse them with comets, which also look like fuzzy patches in the sky.
More Things in Heaven and Earth
Take a moment to let the profound nature of this image sink in. This image is what we got when we pointed the Hubble telescope at what looked like empty space. Each smudge of light in this image is a young galaxy, from about 500 million years after the big bang. Thousands of galaxies in a patch of sky the size of a grain of sand.
Cosmic Energy
We know the universe is expanding at an ever increasing speed. This is due to a type of energy known as dark energy.
Hubble’s Constant
Hubble’s constant shows a relationship between the distance of a galaxy and the speed at which it moves away from us. Its discovery was the first evidence that the universe is expanding.