For more than 15 years, the Hubble Space Telescope (HST) has been providing scientists and the public with spectacular images of deep space. One of the most technologically advanced pieces of equipment that humans have put into orbit, Hubble, named after the astronomer Edwin Hubble, has helped researchers make important discoveries about our universe, ranging from planets and stars to galaxies and cosmology.
The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space
Telescope Science Institute. Built at a cost of $1.5 billion, the Hubble Space Telescope was carried into orbit by a space shuttle in 1990. Although not the first space telescope, Hubble is one of the largest and most versatile, and is both a vital research tool and a public relations boon for astronomy.
HOW IT GOT THERE
Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, scientists found that the main mirror had been ground incorrectly, which severely compromised the telescope’s capabilities. However, after a servicing mission in 1993, the telescope was restored to its intended quality by adding a corrective lens.
The spacecraft in which the telescope and instruments were to be housed was another major engineering challenge. It would have to adequately withstand frequent passages from direct sunlight into the darkness of Earth’s shadow, which would generate major changes in temperature, while bein
g stable enough to allow extremely accurate pointing of the telescope. A shroud of multi-layer insulation keeps the temperature within the telescope stable, and surrounds a light aluminum shell in which the telescope and instruments sit. Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned. Because graphite composites are hygroscopic, there was a risk that water vapor absorbed by the truss while in Lockheed’s clean room would later be turn to ice in the vacuum of space. To reduce that risk, a nitrogen gas purge was performed prior to launching the telescope into space.
Hubble is the only telescope designed to be serviced in space by astronauts. Four servicing missions were performed from 1993 to 2002, but the fifth was canceled on safety grounds following the Columbia disaster. One final servicing mission was completed in 2009. The telescope is now expected to function until at least 2014. Its successor, the James Webb Space Telescope, is due to be launched by 2018.
Hubble was originally designed to be returned to earth on board a shuttle. With the retirement of the shuttle fleet, in July 2011, this is no longer possible. NASA engineers developed the Soft Capture and Rendezvous System (SCRS), a ring-like device that was attached to Hubble’s aft bulkhead during SM4, which will enable the future rendezvous, capture, and safe disposal of Hubble, by either a crewed or robotic mission.
WHAT IT’S ACCOMPLISHED
Hubble’s orbit outside the distortion of Earth’s atmosphere allows it to take extremely sharp images with almost no background light. It has a marked role in many discoveries, not least of which has been to strengthen the hypothesis that dark energy causes the expansion of the Universe to accelerate. It was also instrumental in narrowing down the estimated age of the Universe from 10 to 20 billion years to 13 to 14 billion, as well as giving astronomer’s detailed information on supernovae, and galaxies in various evolutionary states.
Hubble’s Ultra Deep Field image, for instance, is the most detailed visible-light image ever made of the universe’s most distant objects. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
One of Hubble’s most famous images, Pillars of Creation, shows stars forming in the Eagle Nebula.
A unique legacy of Hubble are the Hubble Deep Field and Hubble Ultra Deep Field images, which utilized Hubble’s unmatched sensitivity at visible wavelengths to create images of small patches of sky that are the deepest ever obtained at optical wavelengths. The images reveal galaxies billions of light years away, and have generated a wealth of scientific papers.
The high-resolution spectra and images provided by the HST have been especially well suited to establishing the prevalence of black holes in the nuclei of nearby galaxies. While it had been hypothesized in the early 1960s that black holes would be found at the centers of some galaxies, and work in the 1980s identified a number of good black hole candidates, it took images from Hubble to show that black holes are probably common to the centers of all galaxies.
The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 came just a few months after Servicing Mission 1 had restored Hubble’s optical performance. Hubble images of the planet were sharper than any taken since the passage of Voyager 2 in 1979, and were crucial in studying the dynamics of the collision of a comet with Jupiter, an event believed to occur once every few centuries.
Other major discoveries made using Hubble data include proto-planetary disks (proplyds) in the Orion Nebula; evidence for the presence of extra solar planets around sun-like stars; and the optical counterparts of the still-mysterious gamma ray bursts. HST has also been used to study objects in the outer reaches of the Solar System, including the dwarf planets Pluto and Eris.
While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. Astronomers from the High-z Supernova Search Team and the Supernova Cosmology Project used the telescope to observe distant supernovae and uncovered evidence that, far from decelerating under the influence of gravity, the expansion of the universe may in fact be accelerating. This acceleration was later measured more accurately by other ground-based and space-based telescopes, confirming Hubble’s finding.
SOME HUBBLE FACTS
More than 30,000 objects have come under the all seeing eye of the Hubble Space Telescope in its 21-year history.
The Hubble Space Telescope transmits a large quantity of data every week (approx. 120 gigabytes). The power required for it to perform its various operations comes from its two 25-foot solar panels, which charge 6 nickel-hydrogen batteries.
Hubble is rather small compared to most ground-based telescopes. Its dimensions are 43.5ft in length, has a maximum diameter of 14ft, and weighs in at around 11 tons
Despite the colorful images released by NASA, the pictures taken by the Hubble Space Telescope are black and white. The color added later to enhance features of an object, as well as give an indication of how the object would appear if our eyes were on a par with Hubble.
Editor Phil Robertson is an award-wining journalist and graphic designer. With a degree from the University of Florida’s School of Journalism, his career in journalism and publishing spans over 30 years, and includes positions as editor and publisher for several newspapers and magazines. During his career he has received a first-place award for investigative journalism from the Society of Newspaper Editors, and five ADDY awards for advertising design.
