The Hubble Space Telescope celebrates its 30th birthday. This year marks a significant milestone in astronomy as the Hubble Space Telescope – the world’s first optical telescope in space- has been orbiting the earth for 30 years, since its launch in April 1990 and has been relaying the most amazing photographs of planets and galaxies millions of light years from earth. The Hubble Telescope has been able to see 10-15 billion light years away and the furthest area that it has recorded, has been aptly called the ‘Hubble Deep Field’. Quite simply, the Hubble Space Telescope has revolutionised astronomy.
“Hubble”, a fitting name…
The Hubble Space Telescope (affectionately known as ‘Hubble’) was named after the American astronomer, Edwin Powell Hubble (1889-1953) Edwin Hubble used the largest telescopes possible at the Wilson Observatory in California. He has been credited with making a number of important discoveries including the fact that the Milky Way is only one of many similar galaxies. He made his greatest discovery in 1929 when he found that the further a galaxy is from earth, the faster and further it seemed to move. This idea of an expanding universe became the foundation of the ‘Big Bang Theory’.
Scientists decided that launching a telescope into space was the only way to ensure that they got a truly clear view of the universe, as using even powerful telescopes on land had been found to have limitations. They had found that the earth’s atmosphere could blur images and also some important wave lengths of light. They believed that having a telescope in space, high above the earth’s atmosphere could be really advantageous.
…And a historic moment
The Hubble Space Telescope was launched aboard the space shuttle Discovery (STS-31) on 24 April 1990. Hubble was then deployed solo into orbit the following day, on 25 April. Hubble makes a complete orbit of the earth every 95 minutes. Hubble orbits at an altitude of 547km (339 miles) and at an inclination towards the sun of 28.5º. Hubble travels at an average speed of 27,300 km per hour. The first exciting image relayed to earth from the space telescope was of a star cluster (NGC3532) on 20 May 1990. Since then, 150 gigabits of raw scientific data are relayed every week. To date, Hubble has travelled four billion miles around the earth and has been able to age the universe at 13.8 billion years..
The Hubble Space Telescope measures 13.2 metres (43.45 feet) which is the approximate length of a bus and has a diameter of 4,2 metres (14 feet). When launched, Hubble weighed 10,886kg (24,000 pounds) but this increased to 12,247 kg (27,000 pounds) following the fourth service mission in 2009, when extra equipment was installed. Hubble is powered by the sun and has two 25 foot solar panels on its body which generate 5,500 watts which is stored in the equivalent of 22 car batteries!
The science behind Hubble
Hubble is a Cassegrain Telescope which uses reflection. This type of telescope uses two mirrors – a large primary mirror and smaller secondary mirror. The light enters the telescope and hits the primary mirror. The light is then reflected onto the secondary mirror that focuses and channels the light m back to the small central hole in the primary mirror. As the light travels through the mirror it is captured by a range of scientific instruments.
Hubble’s primary mirror has a diameter of 2.4 metres (94.5 inches) and weighs 828kg (1,825 pounds), whilst the secondary mirror measures 0.3 metres (12 inches) and weighs 12.3 kg (27.4 pounds).
There are five key pieces of equipment onboard for processing the data from the light. The light travels through the primary mirror and directly passes to a Wide Field Camera, Cosmic Origins Spectrograph, Advanced Survey Camera, Space Imaging Spectrograph and Fine Guidance Sensors. The Hubble space telescope also has optical cameras on board and these are digital CCD cameras.
All the photographs they take are in greyscale pixels but coloured filters are used to introduce different colours into each image. Although many would say that the addition of the colour makes the photographs more dramatic and artistically appealing, there is a more important reason for using colour and that is to highlight the finest details that could be otherwise missed by the human eye.
Using its optics and sensitive detectors which work particularly well with UV light and because there is no distortion of the light it uses, Hubble is able to spot something as small as a coin on the surface of the moon. Its sensitive cameras and spectrograph have been able to capture many fascinating images colliding asteroids and even the most distant galaxies.
The mystery of dark energy
There have been some exciting discoveries made with data provided by Hubble and used in conjunction with land-based telescopes. One discovery is that the cosmos is getting larger. This was first suggested by Edwin Hubble nearly 100 years ago and his calculations for this growth were named the ‘Hubble Constant’.
Using measurements made by the Hubble telescope in conjunction with those made using ground telescopes, astronomers have found that the galaxy is definitely enlarging and to their surprise, that this expansion has been accelerated. They believe that the cause for this is the dark energy that has been discovered by Hubble.
This discovery has excited astronomers most as this strange and invisible dark energy appears to permeate space and constitutes up 70% of the mass and energy in the universe. The exploration of this discovery by astronomers won them the 2011 Nobel Prize in Physics. Their work continues as they explore how dark energy can affect star clusters and distort light from distant galaxies.
The discovery of more planets
Another major discovery for astronomers, has been the existence of other planets. When Hubble was launched in April 1990, astronomers believed that our global system was the only one with planets, but since then, more have been discovered by NASA’s Kepler Space Observatory working closely with Hubble. No less than 3,000 extrasolar planets have been discovered. Hubble has been used to analyse the atmospheric composition of the planets and although most of them have been found to be too hot to support life as we know it, exploration continues.
Using data collected by Hubble, astronomers have been able to study the creation and growth of a number of new galaxies and even to monitor hydrogen leaking from another planet. For more detailed information about the exciting discoveries made using Hubble and the chance to see a gallery of Hubble’s most iconic photographs log onto
www.hubblesite.org and www.nasa.gov.
Changing our knowledge of the cosmos
Hubble has meant that astronomers have been able to view distant planets and stars like never before. Hubble has made 1.3 million observations since it was deployed and astronomers analysing its data have published 15,000 scientific papers. The subjects of these papers have ranged from planet formation to enormous black holes.
Hubble has been designed to stay in space and to be maintained in space by astronauts. So far there have been five space shuttle missions over the years to repair and maintain Hubble. Astronauts have also made several upgrades as well as being able to replace the five main instruments onboard.
The Hubble telescope has been a project of international cooperation. It was built by the United States Space Agency -NASA- with contributions from the European Space Agency (ESA). The Space Telescope Science Institute (STSI) plans the work undertaken by Hubble and also analyses the data it produces, whilst Hubble is physically controlled by the Goddard Space Flight Center.
An increased interest in astronomy
The use of Hubble has been far reaching as all new astronomical text books make reference to the data collected by it. Interestingly, few students studying astronomy at university known a time without Hubble. Hubble has create an increased public interest in astronomy and some of the most amazing and iconic images it has captured can now be seen on book jackets, tee-shirts at the movies and even on stained glass windows. What the space telescope has revealed has been both exciting and thought-provoking and fundamentally changed our understanding of the cosmos.
Hubble is currently more productive than ever and will certainly remain in service until 2030, if not for a further ten years after that. Hubble has been the greatest development in astronomy since Galileo made his first telescope in 1609 to look at the moon and other planets. The photographs provided by the Hubble Space Telescope have been astounding and astronomers the world over are looking forward to seeing many more in the years to come…