The Hubble Space Telescope

The Hubble Space Telescope (HST) is the brainchild of the European Space Agency (ESA) and NASA. It was designed to operate in a long-lived space-based optical observatory for the benefit of the international astronomical community. The orbiting facility is named for the American astronomer Edwin P.  Hubble, who revolutionized our knowledge of the size, structure, and makeup of the universe through his pioneering observations in the first half of the 20th century. The HST is being used by astronomers and space scientists to observe the visible universe to distances never before obtained and to investigate a wide variety of interesting astronomical phenomena. In 1996, for example, HST observations revealed the existence of approximately 50 billion (109) more galaxies than scientists previously thought existed!

The HST is 13.1 meters long and has a diameter of 4.27 meters. This space-based observatory is designed to provide detailed observational coverage of the visible, near-infrared, and ultraviolet portions of the electromagnetic (EM) spectrum. The HST power supply system consists of two large solar panels (unfurled on orbit), batteries, and power-conditioning equipment. The 11,000 kilogram free-flying astronomical observatory was initially placed into a 600-kilometer low-Earth orbit (LEO) during the STS-31 space shuttle Discovery mission on April 25, 1990.

Because of HST’s location above the Earth’s atmosphere, its science instruments can produce high-resolution images of astronomical objects. Ground-based telescopes, influenced by atmospheric effects, can seldom provide resolutions better than 1.0 arc-second, except perhaps momentarily under the very best observing conditions. The Hubble Space Telescope’s resolution is about 10 times better, or 0.1 arc-second.

Here are just a few of the exciting discoveries provided by the Hubble Space Telescope: (1) It gave astronomers their first detailed view of the shapes of 300 ancient galaxies located in a cluster 5 billion light-years away; (2) it provided astronomers their best look yet at the workings of a black hole “engine” in the core of the giant elliptical galaxy NGC4261, located 45 million light-years away in the constellation Virgo; (3) HST’s detailed images of newly forming stars helped confirm more than a century of scientific hypothesis and conjecture on how a solar system begins; and (4) HST gave astronomers their earliest look at a rapidly ballooning bubble of gas blasted off a star (Nova Cygni, which erupted on February 19, 1992).

Pushing the limits of its powerful vision, the HST has also uncovered the oldest burned-out stars in the Milky Way galaxy. Detection of these extremely old, dim white dwarfs has provided astronomers a completely independent indication of the age of the universe, an assessment that does not rely on measurements of the universe’s expansion. Finally, from September 2003 to January 2004, the Hubble Space Telescope performed the Hubble Ultra Deep Field (HUDF) observation, the deepest portrait of the visible universe ever achieved by humankind. The HUDF revealed the very first galaxies to emerge from the so-called dark ages - the time shortly after the big bang event when the first stars reheated the cold universe. This historic portrait of the early universe involved two separate long-exposure images captured by the HST’s Advanced Camera for Surveys (ACS) and the Near-Infrared Camera and Multi-object Spectrometer (NICMOS).

Imagery from the HST has revolutionized our view of the visible universe. Refurbished by shuttle servicing missions, this amazing facility should continue to provide astrophysicists and astronomers with incredibly interesting data for several more years.

Questions to Ponder

• Why is it important for the Hubble Space Telescope to be outside the Earth's atmosphere?
• How long does it take for the hubble space telescope to orbit the earth?
• Is the Hubble Space Telescope a reflecting or refracting telescope?