Since its launch in 1990, the Hubble Space Telescope (HST) has provided a dazzling array of images that have awed and inspired the public.
But Hubble’s about far more than just pretty pictures. The mission has gathered dozens of terabytes of data over the decades, providing key insights into the universe, from objects as close as the moon to the most remote galaxies, with incredible photos of supernovas and nebulas in between.
Here we explore the history of the telescope and its discoveries, provide interesting Hubble facts and link to some of the orbiting observatory’s best images.
Getting Hubble off the ground
When Galileo Galilei first turned a spyglass to the heavens in 1610, he had trouble making out the rings of Saturn that are visible in inexpensive telescopes today. Advances in optics eventually improved scientists’ views of the planets, stars and distant galaxies, but Earth’s atmosphere still blocked or distorted much of the light for observers on the ground. Larger telescopes were, and still are, placed atop mountains, where the thinner atmosphere at higher elevations allows clearer pictures.
In 1946, soon after World War II, astronomer Lyman Spitzer proposed launching a space telescope, which could overcome the limitations of ground-based observatories. It took a couple more decades before the idea garnered enough support for the U.S. National Academy of Sciences to organize a committee of scientists to evaluate the potential of a “Large Space Telescope.” With Spitzer at the helm, the committee published a document in 1969 that outlined the scientific uses of a Large Space Telescope and advocated for its construction, according to a Hubble history written by Gabriel Olkoski for NASA.
The National Academy of Sciences took the pitch to NASA — the only agency capable of making the Large Space Telescope a reality. NASA was already considering a space telescope of some type, but the agency was undecided about how big to make it and where to start. In 1971, George Low, the agency’s acting administrator at the time, greenlit the Large Space Telescope Science Steering Group, and NASA soon began lobbying Congress for funding for the endeavor.
The expensive project was a tough sell, and funding was initially denied by the House Appropriations Subcommittee in 1975. NASA then upped its lobbying efforts and got buy-in from European Space Agency, which shared the costs. Congress eventually granted funding for NASA’s portion of the Large Space Telescope in 1977.
Development began almost immediately. NASA planned to launch the telescope in 1983, but various production delays pushed the launch date back to 1986.
In the meantime, the Large Space Telescope was renamed Hubble in honor of Edwin Hubble, an American astronomer who, among other things, determined that the universe extended beyond the borders of the Milky Way.
Hubble’s planned liftoff was delayed again after the space shuttle Challenger exploded a minute after takeoff on Jan. 28, 1986, killing all seven astronauts on board. It was more than 2.5 years before shuttle flights resumed and NASA could begin planning Hubble’s launch again.
The world’s first space telescope finally launched aboard the space shuttle Discovery on April 24, 1990 and a day later was deployed into low Earth orbit, about 340 miles (545 kilometers) above our planet. Getting Hubble developed and launched cost $1.5 billion, but there would be ongoing costs as well — both expected and unexpected.
Blurry initial images — and a fix
Initial instruments on Hubble included the Wide Field Planetary Camera, the Goddard High Resolution Spectrograph (GHRS), the Faint Object Camera (FOC), the Faint Object Spectrograph (FOS) and the High Speed Photometer.
Hubble experienced equipment issues right off the bat. For example, the telescope’s first images came back so blurry that they were close to useless scientifically. It turned out that Hubble’s 7.9-foot-wide (2.4 meters) main mirror had a defect — a spherical aberration caused by a manufacturing error. The flaw was minute, at just 1/50th the thickness of a sheet of paper, but that was big enough to cause major imaging problems.
Hubble became a laughingstock, the butt of jokes that spread through popular culture. For instance, the 1991 film “Naked Gun 2 1/2: The Smell of Fear” features a photo of Hubble. It appears on the wall of an establishment called Loser’s Bar, along with pictures of the Hindenburg, the 1906 San Francisco earthquake, the Ford Edsel and other famous disasters.
But all was not lost, for Hubble was designed to be serviced by astronauts. On Dec. 2, 1993, the space shuttle Endeavour ferried a crew of seven to fix Hubble during five days of spacewalks. Two new cameras, including the Wide-Field Planetary Camera 2 (WFPC-2) — which later took many of Hubble’s most famous photos — were installed during the fix. In December 1993, the first new images from Hubble reached Earth, and they were breathtaking.
Spacewalking astronauts repaired, maintained and upgraded Hubble on four additional servicing missions, which took place in February 1997, December 1999, March 2002 and May 2009.
The 1997 mission replaced some failed or degraded hardware and installed two new instruments, the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer. The new instruments, which replaced the GHRS and FOS, extended Hubble’s vision into the near-infrared wavelength range, NASA officials wrote in a servicing mission explainer.
The next astronaut visit was originally intended to be a relatively routine maintenance trip that lifted off in June 2000. But the fourth of Hubble’s orientation-maintaining gyroscopes failed in November 1999, sending the observatory into a protective “safe mode.” (Hubble has six gyros but needs at least three functioning ones to collect science data.) In response, NASA revised its servicing mission plans, splitting the next one into two parts, the first of which launched in December 1999.
On that 10-day mission, astronauts replaced all of Hubble’s gyros, as well as one of its three fine guidance sensors, and performed other maintenance work as well.
The next crewed Hubble visit, known as Servicing Mission 3B (following from 1999’s Servicing Mission 3A), occurred in December 2002. During that 11-day trip, “astronauts replaced Hubble’s solar panels and installed the Advanced Camera for Surveys (ACS), which took the place of Hubble’s Faint Object Camera, the telescope’s last original instrument,” NASA officials wrote in the servicing mission explainer.
The fifth and final Hubble servicing mission was a 13-day trip that launched in May 2009. Astronauts replaced the observatory’s solar panels and installed two new instruments, the Cosmic Origins Spectrograph and Wide Field Camera 3. The spacewalkers also revived the ACS and STIS, both of which had failed. “With these efforts, Hubble was brought to the apex of its scientific capabilities,” NASA officials wrote.
And ever since, Hubble has continued to provide unprecedented information about our universe and inspire curious minds around the world.
Hubble is a joint project between NASA and the European Space Agency. Here are some basic facts about the telescope and the mission, courtesy of NASA:
- Length: 43.5 feet (13.2 meters)
- Weight: 24,500 lbs. (11,110 kilograms)
- Maximum diameter: 14 feet (4.2 m)
- Launch: April 24, 1990, from space shuttle Discovery (STS-31)
- Deployment: April 25, 1990
- Servicing Mission 1: December 1993
- Servicing Mission 2: February 1997
- Servicing Mission 3A: December 1999
- Servicing Mission 3B: February 2002
- Servicing Mission 4: May 2009
- Orbit: Average altitude of 340 miles (547 km), inclined 28.5 degrees to the equator.
- Time to complete one orbit: 95 minutes
- Speed: 17,000 mph (27,000 km/h)
Hubble transmits about 120 gigabytes of science data every week. That would be roughly 3,600 feet (1,097 meters) of books on a shelf. The collection of pictures and data is stored on magneto-optical disks.
- Energy source: Sunlight
- Mechanism: Two 25-foot solar panels
- Power usage: 2,800 watts
- Batteries: 6 nickel-hydrogen (NiH), with a storage capacity equal to 20 car batteries
- Primary mirror diameter: 94.5 in (2.4 m)
- Primary mirror weight: 1,825 lb (828 kg)
- Secondary mirror diameter: 12 in (0.3 m)
- Secondary mirror weight: 27.4 lb (12.3 kg)
Hubble has been serviced five times. Here are the highlights of each servicing mission:
- Servicing Mission 1 – STS-61, December 1993: A corrective optics package was installed, and the Wide Field Planetary Camera was replaced with the Wide Field and Planetary Camera 2 (including an internal optical correction system.) The computers were upgraded. The astronauts also replaced solar arrays, gyroscopes, magnetometers, computers and other equipment.
- Servicing Mission 2 – STS-82, February 1997: Among other tasks, astronauts installed the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), replacing the GHRS and the FOS. An unexpected problem with NICMOS shortened its expected lifespan to only 2 years, less than half of initial projections.
- Servicing Mission 3A – STS-103, December 1999: The third servicing mission was divided into two parts after three of the six gyroscopes (pointing devices) failed on Hubble. Just a few weeks before 3A lifted off, a fourth gyroscope failed and left the telescope unable to point in the right direction for observations. 3A replaced all the gyroscopes, a fine guidance sensor and the computer, among other tasks. The mission put Hubble back in service shortly after the repairs were completed.
- Servicing Mission 3B – STS-109, March 2002: This mission installed the Advanced Camera for Surveys (replacing the FOC), repaired NICMOS and replaced the solar arrays.
- Servicing Mission 4 – STS-125, May 2009: This mission was at first scheduled for February 2005, but NASA canceled it after the Columbia shuttle was damaged during launch and broke up during re-entry in 2003, killing seven astronauts. Hubble is in a different orbit than the International Space Station. Should a shuttle be damaged upon liftoff, there was no safe haven for astronauts to retreat to in case of emergency. However, following outcry from Congress, the scientific community and the public, the Hubble mission was reinstated and scheduled for 2008. When one of Hubble’s data-handling units failed, the mission was pushed back to 2009 to include a replacement part for that, too. The astronauts on Mission 4 repaired or replaced several systems and installed two new instruments: Wide Field Camera 3 and the Cosmic Origins Spectrograph.
Hubble’s elevated perspective and advanced optics allow it to peer farther away than previous ground-based optics are able to see. Because light takes time to travel long distances, the range of the HST makes it function similar to a time machine; the light it views from remote objects only reveals how that object appeared when the light left it, not how it appears today. Thus when we look at the Andromeda galaxy, 2.5 million light-years from Earth, we see it as it was 2.5 million years ago.
And with Hubble, distant objects are revealed that otherwise can’t be seen at all.
When astronomers pointed the HST to a seemingly empty patch of sky in Ursa Major in 1995, for instance, they captured an image of over 3,000 galaxies too distant to be detected by other telescopes. (This was later called the Hubble Deep Field). Some of the galaxies were so young, they had not yet begun serious star formation. Other deep field observations in the same area were performed, peering deeper into space each time. These were called the Hubble Ultra-Deep Field (released in 2004) and the Hubble eXtreme Deep Field (released in 2012).
In addition to gazing at the early universe, Hubble also helped astronomers gauge how much time had passed since the Big Bang. By measuring a special kind of pulsing star known as a Cepheid variable, they were able to narrow down the age of the universe from its pre-HST range of 10 to 20 billion years to a more precise 13.7 billion years.
Hubble also examines individual stars in various stages of their evolution – from the clouds of dust that form infant stars to the corpses of those long since detonated, and those in between. It has even been able to peer outside of our galaxy, the Milky Way, and into its neighbors, the Magellanic Clouds and Andromeda Galaxy.
More challenging to see than stars are planets orbiting other suns. Yet in 2008, Hubble captured pictures of the planet Fomalhaut b, the first time an extrasolar planet was directly imaged in visible light. But most planets are more challenging to photograph. Much of the HST’s work with other planets comes through the detection of their atmosphere as they pass in front of their sun; the atmosphere filters the light from the stars, and the Hubble records the changes.
Hubble may spend much of its time peering light-years from Earth, but on occasion it takes the time to photograph the planets traveling around our sun. High resolution images taken of Jupiter, Saturn and even Pluto can provide insights that can only be topped by planetary probes circling the planets. Images from the HST allows scientists on Earth to monitor changes in the planet’s atmosphere and surface. When the comet Shoemaker-Levy crashed into the Jupiter in 1994, Hubble photographed the fatal collision. The aftermath revealed a great deal about the gas giant’s atmosphere.
Further, Hubble has seen what appears to be water plumes erupting from the moon Europa, a moon of Jupiter. The telescope made an initial observation in March 2014 and then saw a follow-up candidate plume in the same location in February 2016.
In orbit for more than two decades, Hubble has provided scientists with a greater understanding of the planets, galaxy, and the whole universe. Among the most amazing Hubble discoveries and research projects:
- Creating a 3-D map of mysterious dark matter.
- Discovering Nix and Hydra, two moons of Pluto.
- Helping determine the rate of the universe’s expansion.
- Discovering that nearly every major galaxy is anchored by a black hole.
- Helping refine the age of the universe.
Recent Hubble discoveries
Here are some additional highlights of Hubble’s discoveries over the past few years:
- 2020: Spotted evidence for a mysterious star-eating black hole at the edge of another galaxy, and celebrating its 30th birthday!
- 2019: Took a close-up of a spiral galaxy that may help demystify black holes, showed us the colorful demise of a dying star and captured incredible images of Comet Borisov.
- 2018: Spied the enormous ‘El Gordo’ galaxy cluster, watched a giant storm on Neptune disappear and caught the first look at the leftovers of a supernova explosion.
- 2013: Performed several observations of the spectacular Comet ISON before the comet broke up near the sun around Thanksgiving, examined an explosion on a distant star, discovered a new moon around Neptune and revealed details about the Milky Way’s history based on images of 400 galaxies in various stages of evolution.
- 2014: Watched asteroid P/2013 R3 falling apart; observed a rare, close supernova called SN 2014J; found an extremely distant “cosmic magnifying glass“; and released an image – called the Ultraviolet Coverage of the Hubble Ultra Deep Field – that showed the universe’s evolution.
- 2015: Made fresh observations of the “Pillars of Creation” to see how they changed over time, captured the sharpest view ever of the Andromeda Galaxy, performed the best 3-D view of the deep universe, and observed a dark vortex on the planet Neptune. The year 2015 was also Hubble’s 25th anniversary in space.
- 2016: Made close-up observations of Comet 252P/LINEAR), spotted the farthest galaxy then known, and showed that the universe likely has 10 times the number of galaxies previously thought to have existed.
- 2017: Found a stratosphere on a huge exoplanet, spotted ultrabright galaxies, watched the farthest known active comet, and accidentally discovered several asteroids when they snuck into observations of a galaxy cluster.
Stpectacular Hubble pictures
Below are some of the best images taken by the Hubble.
Find more in this gallery of awesome Hubble pictures.
Saturn’s Rings in Ultraviolet – A new look at some of the most well-known rings in the solar system. Credit: NASA and E. Karkoschka (University of Arizona)
Hubble Ultra Deep Field – Staring at a patch of dark sky, the HST turned up over 10,000 early galaxies unseen from the surface of Earth.. Credit: NASA, ESA, R. Windhorst (Arizona State University) and H. Yan (Spitzer Science Center, Caltech)
When Galaxies Collide – Two colliding galaxies produced a long-tailed, ring-shaped galaxy. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
A Moon of Uranus – The HST captures an eclipse as the moon, Ariel, passes in front of the sun. Credit: NASA, ESA, L. Sromovsky (University of Wisconsin, Madison), H. Hammel (Space Science Institute), and K. Rages (SETI)
Hubble captures images of dust storms on the red planet at the polar caps. Credit: NASA, James Bell (Cornell Univ.), Michael Wolff (Space Science Inst.), and The Hubble Heritage Team (STScI/AURA)
Butterfly Emerges From Stellar Death – A dying star ejecting dust and gas has created a beautiful planetary nebula. Credit: NASA, ESA, and the Hubble SM4 ERO Team
Cosmic Pearls From Supersonic Shockwave – Shock waves unleashed from a 1987 supernova are now colliding with the dust and gas around the star, heating the ring and causing it to glow. Credit: NASA, P. Challis, R. Kirshner (Harvard-Smithsonian Center for Astrophysics) and B. Sugerman (STScI)
Galactic Gas Bubbles – A bubble of gas in the center of the galaxy NGC 3079 rises above the flattened disk. Credits: NASA, Gerald Cecil (University of North Carolina), Sylvain Veilleux (University of Maryland), Joss Bland-Hawthorn (Anglo- Australian Observatory), and Alex Filippenko (University of California at Berkeley).
Eta Carinae – The Dumbel Explosion – Dust and gas exploding on both sides of the star, Eta Carinae, are shown in remarkable detail. Structures only 10 billion miles across can be observed despite the stars great distance. Credit: Jon Morse (University of Colorado), and NASA
The Ring Nebulae – A dying star shucked off the dust and gas to create the most famous planetary nebulae. The HST revealed dark clumps of material embedded in the edges of the gas ring, while the dying star hides in the center. Credit: The Hubble Heritage Team (AURA/STScI/NASA)
Preparing for the Trip to Vesta – Images taken by the HST helped astronomers and engineers plan for NASA’s Dawn Mission to the asteroid Vesta and the protoplanet Ceres. Credits for Vesta: NASA; ESA; L. McFadden and J.Y. Li (University of Maryland, College Park); M. Mutchler and Z. Levay (Space Telescope Science Institute, Baltimore); P. Thomas (Cornell University); J. Parker and E.F. Young (Southwest Research Institute); and C.T. Russell and B. Schmidt (University of California, Los Angeles). Credits for Ceres: NASA; ESA; J. Parker (Southwest Research Institute); P. Thomas (Cornell University); L. McFadden (University of Maryland, College Park); and M. Mutchler and Z. Levay (Space Telescope Science Institute)
A Stream of Sub-atomic Particles – Electrons and other sub-atomic particles stream from a black hole in the center of the galaxy M87. Credit: NASA and The Hubble Heritage Team (STScI/AURA)
Shoemaker-Levy Bruises Jupiter – When the comet Shoemaker-Levy bombarded Jupiter in 1994, it left its mark on the planet. Credit: Hubble Comet Team and NASA.
This article was updated on April 20, 2020 by Space.com Reference Editor Kimberly Hickok.