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What Is the Hubble Space Telescope?
April 28, 2009
The Hubble Space Telescope is a large telescope in space. It was launched into orbit by space shuttle Discovery in 1990. Hubble orbits about 550 kilometers (342 miles) above Earth. It is the length of a large school bus and weighs as much as two adult elephants. Hubble travels about 5 miles per second, and is powered by sunlight.

Hubble takes sharp pictures of objects in the sky such as planets, stars and galaxies. Hubble has taken thousands of images. These include detailed pictures of the birth and death of stars, galaxies that are billions of light years away, and comet pieces crashing into Jupiter's atmosphere.

Scientists have learned a lot about the universe from these pictures. Many of them are also beautiful to look at.

What Makes Hubble Different From Telescopes on Earth?
Earth's atmosphere alters and blocks the light that comes from space. Hubble orbits above Earth's atmosphere, which gives it a better view of the universe than telescopes have at ground level.

Where Did the Name Hubble Come From?
Hubble is named after an American astronomer, Edwin P. Hubble. He made important discoveries in the early 1900s. He showed that the galaxy containing the solar system - the Milky Way - was only one of many galaxies. His work also helped show that the universe is expanding. This led to the big-bang theory, which says that the universe began with an intense burst of energy and has been expanding ever since.
What Is Servicing Mission 4?
Servicing Mission 4 is the name of the next, and final, space shuttle mission to repair the Hubble telescope. This will be the fifth time astronauts have visited Hubble. The other missions were named Servicing Mission 1, Servicing Mission 2, Servicing Mission 3A and Servicing Mission 3B.

Astronauts plan to install two new instruments and fix two broken instruments during the mission. Scientists hope that the repairs and upgrades made by the astronauts will keep the telescope running for at least five more years.

What Instruments Are on Hubble?
Hubble started out with five scientific instruments: two cameras, two spectrographs and a photometer. A spectrograph is an instrument that splits light into its individual wavelengths. A photometer is an instrument that measures the intensity or brightness of light. Over the years, Hubble's original instruments have been replaced.

Astronauts on Servicing Mission 4 plan to install two new instruments - the Wide Field Camera 3, or WFC3, and the Cosmic Origins Spectrograph, or COS. They also plan to repair two instruments - the Space Telescope Imaging Spectrograph, or STIS, and the Advanced Camera for Surveys, or ACS.

WFC3 will be Hubble's main new camera. It will study everything from the formation of distant galaxies to the planets in the solar system. COS will be useful to study how stars, planets and galaxies formed and evolved, and how elements such as carbon and iron first formed. Carbon and iron are necessary for life.

STIS has helped scientists determine the temperature, chemical composition, density and motion of objects in space. It has also been used to detect black holes. ACS has taken sharp images of deep space. These images have helped scientists study some of the earliest activity in the universe.

The Near Infrared Camera and Multi-Object Spectrometer was installed during a servicing mission to Hubble in 1997. NICMOS sees objects in deep space by sensing the heat they emit. It helps scientists study how stars, galaxies and planetary systems form.
What Are Hubble's Most Important Discoveries?
Images taken by Hubble have helped scientists estimate the age and size of the universe. Scientists believe the universe is about 13 or 14 billion years old. Hubble has also helped scientists understand how planets and galaxies form. An image called "Hubble Ultra Deep Field" shows the farthest galaxies ever seen.

Hubble has detected black holes, which suck in everything around them, including light. The telescope has played a key role in the discovery of dark energy, a mysterious force that causes the universe to expand faster and faster as time goes on. And it has revealed details of gamma-ray bursts - powerful explosions of energy that occur when massive stars collapse.

Hubble has also seen planets revolving around stars similar to Earth's sun.

Where Do the Colors in Hubble's Images Come From?
Hubble pictures start out as shades of black and white. Colors are then added to the pictures for different reasons. Sometimes colors are chosen to show how an object might look to the human eye. Other times colors are used to highlight an important detail. Or they can be used to show details that would otherwise be invisible to the human eye.

Where Can I See More Hubble Pictures?
› HubbleSite Gallery   →
› NASA's National Space Science Data Center Photo Gallery   →

More About Hubble:
› NASA's Main Hubble Page   →
› HubbleSite   →
› What Is a Black Hole?

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Dan Stillman, Institute for Global Environmental Strategies

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The Hubble Space Telescope orbits above Earth
The Hubble Space Telescope makes one orbit around Earth every 97 minutes.
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A large spiral galaxy with a tail that makes it look like a giant tadpole
The Hubble Space Telescope took this picture of the Tadpole Galaxy and its tail of large, bright blue star clusters.
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Red and yellow gases surround the blue center of the Helix Nebula
This colorful image of the Helix Nebula was taken by the Hubble Space Telescope.
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Page Last Updated: September 18th, 2013
Page Editor: NASA Administrator