Hubble Space Telescope

The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy. The Hubble Space Telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories.

Hubble features a 2.4 m (7 ft 10 in) mirror, and its five main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes.

Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe. The Hubble Space Telescope was funded and built in the 1970s by NASA with contributions from the European Space Agency. Hubble is the only telescope designed to be maintained in space by astronauts, and it continues to provide valuable insights into the universe.

Concept, design and aim

The Hubble Space Telescope was designed to be a large and versatile telescope that could observe the universe from space. Unlike telescopes on Earth, it would not be affected by the blurring effect of Earth’s atmosphere, allowing it to see stars and other objects much more clearly.

Astronomers had long dreamed of putting a telescope in space so they could study stars, galaxies, and other objects without the interference of Earth’s atmosphere. The idea became more serious after World War II, when new rocket technology made it possible to send instruments into space. Over the years, many smaller space telescopes were launched, but the Hubble Space Telescope was planned to be much bigger and more powerful.

Getting the money for Hubble was a long and difficult process. At one point, funding was almost completely cut, but astronomers worked hard to convince lawmakers of its importance. Finally, with support from both the United States and Europe, the project moved forward. Construction involved many different teams and required new technologies to build the telescope’s mirrors and systems.

After many delays, including one caused by a space shuttle disaster, Hubble was finally launched in 1990. It has since provided amazing images and information, changing how we understand the universe.

List of Hubble instruments

The Hubble Space Telescope can hold five science instruments at once, along with special sensors that help aim the telescope. Over the years, Hubble has had many different tools to study stars, galaxies, and other objects in space. Some of these tools have been replaced with newer, better ones during space shuttle visits.

Today, Hubble’s main tools include the Advanced Camera for Surveys, the Cosmic Origins Spectrograph, the Space Telescope Imaging Spectrograph, and the Wide Field Camera 3. There is also a special camera called NICMOS that is currently resting but could be used again if needed.

Flawed mirror

Soon after the Hubble Space Telescope was launched, scientists noticed that the pictures it took were not as clear as they should be. The problem was with the telescope’s main mirror, which had been shaped slightly wrong. This made the images blurry, especially for faint objects far away in space.

To fix this, scientists created special tools to correct the mirror’s mistake. These tools acted like glasses for the telescope. New cameras and mirrors were added during space missions, and by 2002, all the original instruments had been replaced with ones that could correct the problem on their own.

Servicing missions and new instruments

Hubble was built to be fixed and upgraded while it orbited Earth. NASA sent space shuttles to service Hubble five times, starting in December 1993 and ending in May 2009. Astronauts would attach to Hubble with a robotic arm and perform many tasks during spacewalks. They fixed broken parts, added new instruments, and made other upgrades. After each mission, Hubble became even better at helping scientists observe space.

The first servicing mission in 1993 fixed a problem with Hubble’s mirror and added new cameras and computers. Later missions added tools that let Hubble see in different kinds of light, like infrared. The last mission in 2009 fixed more instruments and added new cameras, making Hubble better than ever. These missions helped Hubble continue working and giving us amazing pictures of space for many years.

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Major projects

Since it launched, the Hubble Space Telescope has been used for many important research projects. Some of these projects use Hubble alone, while others combine its abilities with other telescopes like the Chandra X-ray Observatory and ESO's Very Large Telescope. One current project is called ULLYSES, which studies young stars to learn more about how stars form. Another project, OPAL, focuses on learning about the atmospheres of outer planets like Jupiter and Uranus.

One of the largest projects ever done with Hubble is called CANDELS. It aims to study how galaxies evolved in the very early universe. Another major project is the Frontier Fields program, which looks at very distant galaxies to learn about their formation. The Cosmic Evolution Survey (COSMOS) is designed to study how galaxies change over time and depending on where they are located. There is also the Cluster Lensing and Supernova survey with Hubble (CLASH), which observed galaxy clusters to learn about dark matter and dark energy. Finally, Hubble created extremely detailed maps of the Andromeda Galaxy, showing hundreds of millions of stars.

Public use

Anyone can apply for time to use the Hubble Space Telescope, no matter where they are from. However, there is a lot of competition because only about one-fifth of the requests get chosen each year.

Amateur astronomers were also given a chance to use the telescope for a few years. Their proposals were carefully checked to make sure they were good science and needed the special abilities of the space telescope. Even though this program stopped, amateur and everyday scientists still help find new things for the Hubble to look at, working together with professional scientists.

Scientific results

Hubble has helped solve many long-standing problems in astronomy and also raised new questions that scientists are still trying to understand. One of its main goals was to measure distances to stars more accurately, which helps us understand how fast the universe is expanding and how old it is. Hubble’s observations showed that the expansion of the universe is actually speeding up, a discovery that led to the idea of dark energy — a mysterious force that we still don’t fully understand.

Hubble has also been key in discovering black holes at the centers of galaxies and capturing amazing images of distant parts of space, like the Hubble Deep Field. It has observed events in our solar system, such as the collision of a comet with Jupiter and the discovery of moons around Pluto. These observations help scientists learn more about our cosmic neighborhood and the wider universe.

Hubble data

Hubble stores its data on the spacecraft, which is then sent to a satellite and relayed to special antennas on Earth. The data travels to control centers where scientists can study it. Each week, Hubble sends about 140 gigabits of information.

Images from Hubble start out in black and white. Scientists combine different black-and-white pictures taken with special filters to create colorful images. Some of these pictures may show infrared or ultraviolet light, which are shown in deep red or blue for us to see. All of Hubble’s data is saved in archives where scientists can access it after a year, though some special images are shared right away.

Outreach activities

NASA wanted the Hubble Space Telescope to capture people's imagination because many taxpayers helped pay for it. After some early problems with the telescope's mirror, the first servicing mission fixed the issue and produced amazing images that excited the public.

Several efforts help keep people informed about Hubble. In the United States, the Space Telescope Science Institute runs the HubbleSite.org website and the Hubble Heritage Project, which shares beautiful images of space objects. In Europe, the Hubble European Space Agency Information Centre creates news and photos about Hubble's discoveries. These efforts help everyone enjoy the wonders of space explored by Hubble.

Equipment failures

The Hubble Space Telescope uses special tools called gyroscopes to keep itself steady and point accurately at stars and planets. It has six of these gyroscopes, but it only needs three to work properly. Sometimes, these gyroscopes can stop working. In 2009, all six were replaced, and this helped Hubble keep working well.

Hubble also has many instruments that can stop working over time. For example, in 2019, one of its main cameras had a problem with its software, but engineers fixed it quickly. In 2021, a computer on Hubble stopped working because of a power issue, but NASA switched to a backup system and got Hubble running again. These fixes show how scientists work hard to keep Hubble exploring space for us.

Future

NASA plans for the Hubble Space Telescope include ensuring its safe re-entry into Earth's atmosphere. Hubble's orbit slowly decays due to the very thin layers of Earth's atmosphere, and without help, it could fall back to Earth between 2028 and 2040. To prevent uncontrolled re-entry, NASA installed a special mechanism during the last Space Shuttle mission in 2009. This allows for a controlled descent by either a crewed or robotic mission in the future.

There have been ideas to service Hubble again using new spacecraft. Some suggest using a crewed mission to upgrade its instruments and keep it working longer. Others have proposed robotic missions. However, as of 2024, NASA has not approved a private mission to service Hubble due to concerns about potential damage to the telescope.

Hubble has successors, with the James Webb Space Telescope being the main one. Launched in 2021, it observes farther infrared light than Hubble and looks at very distant objects in the universe. Other future telescopes, like the Large Ultraviolet Optical Infrared Surveyor (LUVOIR), might follow, offering even better views of space. Ground-based telescopes are also growing larger and better, but they cannot fully replace space telescopes like Hubble because Earth's atmosphere blocks some types of light.