Hubble Space Telescope
By Steve Morris, 9 Oct 2012
The Hubble Space Telescope was launched in 1990 and is the world's first space-based optical telescope.
Hubble is named after the astronomer Edwin Hubble (1889 - 1953) who first confirmed that the universe is expanding, paving the way for the Big Bang theory. The initial target for the telescope was to help determine the age of the universe (which it did - it's 13 to 14 billion years!) and to help astronomers better understand the evolution of galaxies. It has achieved all this, and also found some surprises, such as the existence of dark matter and dark energy. It has also discovered many extrasolar planets (planets orbiting other stars).
A view from space
Hubble orbits the earth at a height of 569km, travelling at a speed of 17,500 mph, which means that it orbits the Earth every 97 minutes. It's powered by two 25-foot solar panels and has the equivalent of 20 car batteries on board. The telescope is nearly the size of a small bus and weighs 11 tonnes, but it was designed to just fit inside the space shuttle Discovery.
With a total cost at launch of $1.5 billion, you need a good reason to put a telescope into orbit. The benefit of having a space telescope is that it eliminates atmospheric distortion that causes stars to "twinkle". It also allows the telescope to see ultraviolet, gamma- and X-rays that are blocked by the Earth's atmosphere.
Hubble's two mirrors were ground so that they do not deviate from a perfect curve by more than 1/800,000th of an inch. If Hubble's primary mirror were scaled up to the diameter of the Earth, the biggest bump would be only six inches tall.
However, when first launched, Hubble's primary mirror was found to have a tiny flaw that blurred its images. Fortunately it was possible to repair the telescope in space and a five-day mission by the crew of the Space Shuttle Endeavor successfully made the repairs.
The philosophy behind Hubble is very democratic. Any astronomer in the world can submit a proposal and request time on the telescope. An expert review team selects which proposals can go ahead. The results are then made available to the entire scientific community. And of course, many photographs are in the public domain.
Hubble's successor, the James Webb Space Telescope, is currently in production and will study the most distant objects from the earliest universe.
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