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Hubble Q & A Hubble Q & A

Students have a lot of questions about the Hubble Space Telescope. Find a list of background-filled answers here.

Questions and Answers

1. What is the Hubble Space Telescope?

The Hubble Space Telescope is a space-based telescope that was launched in 1990 from the space shuttle Discovery. From its position above Earth's atmosphere, Hubble has expanded our understanding of the universe — and of star birth, star death, galaxy evolution and black holes in particular.

Hubble's view is so spectacular because of its location above Earth's atmosphere. Shifting pockets of air distort light from space — that's why stars seem to twinkle when viewed from the ground. Furthermore, the atmosphere blocks some wavelengths of light partially or entirely, making space the only place where it is possible to get a truly clear and comprehensive view of the universe.

Hubble's large mirror collects light from celestial objects and directs it to the telescope's instruments, the astronomer’s eyes to the universe. Hubble's current instruments are the Wide Field Camera 3 (WFC3), Cosmic Origins Spectrograph (COS), Near Infrared Camera and Multi-Object Spectrometer (NICMOS), Advanced Camera for Surveys (ACS), Space Telescope Imaging Spectrograph (STIS) and Fine Guidance Sensors (FGS).

These are not the only instruments that have flown aboard Hubble. The telescope was designed to be visited periodically by astronauts, who bring new instruments and technology, and who make repairs. Perhaps the most famous of these servicing missions is the first, in 1993. After Hubble's 1990 launch, the telescope's primary mirror was discovered to be out of shape on the edges by 1/50 of a human hair. This very small defect made it difficult to focus faint objects being viewed by Hubble. Astronauts installed corrective optics on the telescope, fixing the flawed vision. Four more astronaut visits would follow, each boosting Hubble's observatory capabilities.


2. Why service the Hubble Space Telescope?

NASA decided early in the telescope's development to design the observatory so it could be serviced while in orbit. Instruments were designed as modular units, comparable to dresser drawers that could be easily removed and replaced. When a component broke or a more technologically advanced instrument became available, astronauts were able to install the new equipment. The telescope's designers equipped Hubble with handholds and other special features to make servicing tasks less difficult for astronauts wearing bulky spacesuits.

By periodically upgrading the science instruments, NASA reasoned that it could provide the science community worldwide with state-of-the-art technology that took advantage of Hubble's unique position high above Earth's obscuring atmosphere. Servicing missions have occurred in 1993, 1997, 1999, 2002 and 2009.


3. Will there be another servicing mission to Hubble?

Servicing Mission 4 in 2009 was the final mission to Hubble. Just as with any piece of advanced technology, Hubble has too many parts for all of them to be repaired indefinitely. As the years progress, components slowly degrade to the point at which they cease functioning.

When that happens, Hubble will continue to orbit Earth until its orbit decays, allowing it to spiral toward Earth. Hubble was designed specifically to function with the space shuttle, but its prolonged lifespan has extended beyond the retirement of the space shuttle program. Instead, a robotic mission is expected to help de-orbit Hubble, guiding its remains through a plunge through the atmosphere and into the ocean.


4. Can we see live photos from Hubble?

There is no "real-time" camera or webcam on board the telescope for live relay links. The images that Hubble takes are digital pictures and spectra released to the public after one year (to allow the astronomers who requested the data enough time to do their research). The data, which are transmitted from the telescope in digital form, needs to be converted from this digitized information by computers into black-and-white photos. These are then enhanced to discern details in the images.

For more detailed information on how the telescope and its instruments operate, visit HubbleSite's Nuts & Bolts.


5. Are the colors in Hubble images real?

There are no "natural-color" cameras aboard Hubble. The optical cameras on board have all been digital CCD cameras, which take images as grayscale pixels.

Sometimes the color is as natural as possible. However, the color given to the images is not just "artistic embellishment." The images are, indeed, downloaded as black and white, and color is added for a number of different reasons — for example, to show the dispersion detail of chemical elements and highlight features so subdued that the human eye cannot see them.

For more information, read Behind the Pictures on HubbleSite, which explains in detail how color is added to images.


6. Can Hubble take pictures of Earth?

The surface of Earth is whizzing by as Hubble orbits, and the pointing system, designed to track the distant stars, cannot track an object on Earth. The shortest exposure time on any of the Hubble instruments is 0.1 second, and in this time Hubble moves about 700 meters, or almost half a mile. So a picture Hubble took of Earth would be all streaks.

To find images of Earth from other sources in space go to The Gateway to Astronaut Photography of the Earth.


7. Sometimes a corner of an image is missing. Why is that?

The strange, stair-shaped images come from the Wide Field and Planetary Camera 2, or WFPC2. WFPC2, removed from Hubble in 2009, consisted of four cameras, each of which takes a picture of a section of the target. It's like taking four pictures of a single scene, then putting them together to create the whole picture.

But one of WFPC2's cameras takes a magnified view of the section it's observing, to allow us to study that section in finer detail. When the images are processed, that magnified section is shrunk down to the same size as the other sections, so that it fits into the image.

For a more thorough explanation for the stair-stepped shape of the Hubble photos, read Hubble's Wacky Window on HubbleSite.


8. Who is the Hubble Space Telescope named after?

Edwin P. Hubble revolutionized cosmology by proving that some clouds of light astronomers saw in the night sky were actually other galaxies beyond our Milky Way. His greatest discovery was in 1929, when he identified the relationship between a galaxy's distance and the speed with which it is moving. The farther a galaxy is from Earth, the faster it is moving away from us. This is known as Hubble's Law. He also constructed a method of classifying the different shapes of galaxies.

Edwin Powell Hubble was born in Marshfield, Missouri. In 1910, he received his undergraduate degree from the University of Chicago and studied law under a Rhodes Scholarship at Oxford University. His true love, however, was astronomy, and he returned to the University of Chicago to earn a Ph.D. in that subject and to work at the Yerkes Observatory. He served in the infantry during World War I.

He once said that he "chucked the law for astronomy," knowing that even if he was second-rate or third-rate, it was astronomy that mattered.


9. What is Hubble doing now?

Hubble continues to rack up observations and make new discoveries. One of its most exciting current projects, Frontier Fields, promises to deliver a wealth of new information about the early history of the universe and the infancy of galaxies. Scientists will rely on Hubble's revelations for years as they continue in their quest to understand the cosmos — a quest that has attained clarity, focus and triumph through Hubble's rich existence.


10. Interesting facts about the Hubble Space Telescope and astronomy…


  • Pointing the Hubble Space Telescope and locking onto distant celestial targets is like holding a laser light steady on a dime that is 200 miles away.

  • The Hubble Space Telescope whirls around Earth at a speed of 17,000 miles per hour. If cars moved that fast, a coast-to-coast trip across the continental United States would take only 10 minutes.

  • Each month the orbiting observatory collects enough information to fill the Library of Congress almost two times over.

  • Images and data collected by the telescope travel 90,000 miles over satellite and ground links before they reach the Space Telescope Science Institute in Baltimore, Maryland.

  • Engineers designed Hubble with servicing in mind. The telescope is equipped with 31 foot restraints and 225 feet of handrails.

  • The tool chest that astronauts use during servicing missions contains more than 100 tools, including common screwdrivers and wrenches.