The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990, and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST is named after the astronomer Edwin Hubble, and is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.
The HST was built by the United States space agency NASA, with contributions from the European Space Agency. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft.
With a 2.4-meter (7.9 ft) mirror, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely high-resolution images, with substantially lower background light than ground-based telescopes. Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
FACTS ABOUT HUBBLE
1. The HST’s history is longer than you might have thought, going back to just after World War II. In 1946, the astronomer Lyman Spitzer (1914-97) identified the main advantages that a space-based observatory would have over ground-based telescopes. Spitzer spent much of his career to pushing for the building of a space telescope.
2. Originally the HST was to have been bigger. NASA began seriously planning it in the mid-1970s. It was originally proposed to have a mirror diameter of 3m, but this was reduced to 2.4 m to save money.
3. The HST is still bigger than you might think. It weighs 11 tonnes and is 15.9 m long. That’s nearly as long as a couple of Routemaster doubledecker buses (each 8.4m long).
4. The HST doesn’t use as much power as you think. It uses about 2800 watts, while a typical kitchen kettle is rated at 2200 watts. Hubble gets its power from a couple of solar panels (each 2.6 x 7.1 m).
5. Hubble is pretty fast for a telescope, speeding around the world at 28 000 km/h. This is twelve times as fast as the cruising speed of the Concorde supersonic airliner (2270 km/h).
6. The HST can observe the furthest away galaxies ever seen but there are a couple of nearby objects it cannot look at. These are the Sun (so bright it would damage its sensors) and the planet Mercury, which is too close to the Sun.
7. Hubble is essentially a giant camera but it doesn’t use film. Its instruments capture the light from the Universe with electronic detectors (CCD’s) so it is basically a giant digital camera.
8. Hubble’s images of the wonders of the cosmos are recorded in shades of black and white, not colour. The final colour images we all love are actually combinations of two or more black-and-white exposures made through coloured filters. During image processing the colours matching the filters are added to the picture.
9. The HST has achieved all the objectives it was designed for. Probably its greatest achievement was measuring the age of the Universe to be about 13.8 billion years. This figure was more accurate than any previous measurement.
10. The Hubble telescope is in the final phase of its life. Sometime after 2014 failure of its vital systems will render it useless. Unless some kind of rescue is made, which is pretty unlikely, it will re-enter the Earth’s atmosphere and burn up sometime between 2019 and 2030. Goodbye Hubble, we’ll miss you. But don’t be sad, it will be replaced by the even larger James Webb Space Telescope.