Hubble Space Telescope is a powerful orbiting telescope that has captured images of heavenly bodies for over 30 years. It is a reflecting telescope with a light-gathering mirror 94 inches (240 centimeters) in diameter. The telescope is named after the American astronomer Edwin P. Hubble, who made fundamental contributions to astronomy in the 1920’s.
Loading the player...Space exploration: Hubble Space Telescope
Astronomers have used the Hubble Space Telescope to obtain images of celestial objects and phenomena in detail never before observed. These include pictures of stars surrounded by dusty disks that might someday evolve into planetary systems, images of galaxies on the edge of the observable universe, pictures of galaxies colliding and tearing each other apart, and evidence suggesting that most galaxies have massive black holes in their centers.
How the telescope works.
In orbit about 380 miles (610 kilometers) above Earth, the Hubble Space Telescope views the heavens without looking through Earth’s atmosphere. The atmosphere bends light due to a phenomenon known as diffraction, and the atmosphere is constantly moving. This combination of diffraction and movement causes starlight to jiggle about as it passes through the air, and so stars appear to twinkle. Twinkling blurs images seen through ground-based telescopes. Because an orbiting telescope is above the atmosphere, it can produce pictures in much finer detail than a ground-based telescope can.
Loading the player...Wide Field and Planetary Camera 2
The Hubble Space Telescope can also observe ultraviolet and infrared light that is blocked by the atmosphere. These forms of light, like visible light, are electromagnetic radiation. The wavelength (distance between successive wave crests) of ultraviolet light is shorter than that of visible light. Infrared light has longer wavelengths than visible light. Ultraviolet light comes from highly energetic processes, such as the formation of disks around black holes and exploding stars. Infrared light provides information about cooler, calmer events, such as the formation of dust clouds around new stars.
The United States space agency, the National Aeronautics and Space Administration (NASA), operates the Hubble Space Telescope in cooperation with the European Space Agency (ESA). The telescope is controlled by radio commands relayed from NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Astronomers tell the telescope where to point, and computer-driven instruments aboard the telescope record the resulting observations. The telescope transmits the data by radio to astronomers on the ground.
The Hubble Space Telescope has two kinds of instruments: (1) imagers, which take pictures; and (2) spectrographs, which analyze light. Imagers are electronic detectors called charge-coupled devices (CCD’s). The CCD’s convert light into electronic signals, which an on-board computer records and sends to the ground.
A spectrograph, like a prism, spreads light into its component colors, much as water droplets spread sunlight into a rainbow. The resulting band of light is called a spectrum (plural spectra). Using spectrographic data from the Hubble Space Telescope, astronomers can determine the composition of stars and galaxies—measuring, for example, the amounts of hydrogen, carbon, and other chemical elements in them.
History.
The space shuttle Discovery launched the telescope into orbit in 1990. Soon after launch, engineers discovered a flaw in the telescope’s light-gathering mirror. The flaw made the images less clear than they otherwise would have been. Engineers designed an optical device to bend light reflected by the mirror in a way that would make up for the error. Astronauts from the space shuttle Endeavour installed the device on the telescope in 1993, correcting the flaw.
Loading the player...20 years of Hubble Space Telescope
During the 1993 mission, astronauts also mounted new instruments on the telescope. As part of a continuing program to upgrade the telescope, astronauts installed additional components in 1997, 1999, 2002, and 2009.
In 2004, NASA administrators canceled a final servicing mission to the telescope that had been scheduled for 2006. The officials based the decision on concern for the safety of astronauts after the loss of the space shuttle Columbia in 2003. Scientists, politicians, and astronomy enthusiasts protested that the decision would bring an early end to the telescope’s observations. NASA officials then studied the possibility of sending a robotic craft to perform needed repairs. They concluded that such a craft could not be developed in time to save the telescope. In October 2006, NASA administrators announced that the agency would send space shuttle astronauts to service the telescope after all.
In 2007, an electrical malfunction in the telescope’s newest instrument, the Advanced Camera for Surveys, caused the device to stop working. Scientists continued observations with the telescope’s remaining instruments.
In 2009, astronauts completed the last scheduled servicing mission on the telescope. They successfully repaired the Advanced Camera for Surveys while also completing several other instrument upgrades. The upgrades have left the telescope with the most advanced set of instruments in its history.
The James Webb Space Telescope, which is designed to replace some of Hubble’s capabilities, began operating in 2022. With a main mirror that is 6.5 meters (21 feet) across, Webb has seven times more light-collecting area than Hubble. But Webb is designed to study infrared light and thus does not replace Hubble’s visible-light capabilities.
