Hubble and his telescope
Introduction
This chapter covers the biography and discoveries of American scientist Edwin Powell Hubble. The chapter looks at one of the most important inventions of modern astronomy - the Hubble Space Telescope.
Who is Hubble?
Edwin Powell Hubble was born at the end of the nineteenth century in the USA. Hubble had been interested in science from an early age. Edwin Hubble was a very good student and athlete. After school he went to Oxford University to study law. After graduation Hubble set up a small law firm. But it did not take long for Hubble to realise he was not happy as a lawyer and that his real passion was astronomy. As a result, he went to Yerkes Observatory to continue his studies. Later he received a doctorate in astronomy from the University of Chicago.
Hubble has helped to resolve some long-standing problems in astronomy. Hubble was the first scientist to prove that Cepheids (pulsating variable stars) were outside our galaxy. He also determined the existence of several other galaxies such as our own Milky Way, which had until then been believed to constitute the entire universe.Hubble also devised a classification system for the various galaxies he observed, sorting them by content, distance, shape and brightness. From these observations he was able to formulate the statement which is now referred to as Hubble's Law. Hubble's Law helped astronomers determine the age of the universe and prove that the universe was expanding. See image 1.
Hubble's Law
If you look at the colour spectrum you will notice that it has a 'red end' and a 'purple end'. The light from distant stars and more distant galaxies is not featureless, but has distinct spectral characteristics. Their spectra are shifted towards the red end of the spectrum. According to Doppler's previous discoveries, this shift indicates that all galaxies are moving away from us. Hubble's Law is the statement, in the branch of astronomy called physical cosmology, that the redshift in light (visible light from an object shifted towards the red end of the spectrum) coming from distant galaxies is proportional to their distance from the Earth. When a radiating object moves away from us, we observe a redshift in its light, meaning that its light waves are getting longer, or shifting, to the red part of the spectrum.
Hubble's telescope
A telescope is an instrument designed to gather light or radiation from a large area and bring it into focus, where the radiation can be analysed. The purpose of most astronomical telescopes is to provide the brightest possible images, since most objects that astronomers study are very faint.
For centuries, telescopes had grown bigger and better, providing a clearer and sharper view. Once telescopes had reached a size that allowed them to see quite well, astronomers encountered a problem unrelated to the telescope's design - the Earth's atmosphere. As light passes through the atmosphere, it can be bent in unpredictable ways by warm and cool air pockets. In order to view the universe in all wavelengths of light, a space telescope had to be built.
After many years of scientific research and observations Hubble came up with the draft for the space telescope. The Hubble Space Telescope (HST) is a telescope in orbit (the path travelled by a body in space) around the Earth. Because this telescope is outside the Earth's atmosphere it can take sharp images of different objects in space that cannot be seen and photographed form Earth. See image 2.
In 1962, the USA's National Academy of Sciences recommended building a large space telescope. It was named the Hubble Space Telescope. Construction of the Hubble Space Telescope was completed in 1985. But its launch was delayed due to the 1986 space shuttle 'Challenger' disaster. Hubble was launched in 1990. Within days Hubble was sending back amazing pictures of the universe but all the images were out of focus. It was discovered that one of its mirrors was faulty. In 1993 the space shuttle 'Endeavor' captured, fixed and modified the Hubble Space Telescope. It became a vital tool of astronomical research. During the second servicing mission in 1997, more parts were added to the telescope or were repaired and replaced. See image 3.
See animation 1.
Hubble mission operations
Today hundreds of scientists, engineers and technicians are responsible for operating the Hubble Space Telescope. Their tasks range from choosing the research targets to performing in-orbit upgrades.
Hubble mission operations fall into two categories:
- Engineering operations, which test and maintain the Hubble spacecraft's performance
- Scientific operations, which select and schedule observation programs, prepare and conduct observations and calibrate the scientific instruments
The future of Hubble is currently unclear. More parts need to be replaced but NASA has determined that a repair mission by astronauts would be unreasonably dangerous.Hubble's successor telescope, the James Webb Space Telescope (JWST), is due to be launched in 2013. This new telescope will be far superior to Hubble for most astronomical research programs.
