Science Themes

Designed and built to explore five broad scientific topics, Hubble has helped us answer some of our most-pressing questions about the cosmos, while simultaneously presenting us with discoveries that generate new questions to answer.

A packed field of galaxies and curved blue streaks and arcs. Bright blue-white foreground star at bottom right.
Galaxy cluster Abell 370, located some 5 billion light-years away, contains an astounding assortment of several hundred galaxies. It is one of the very first galaxy clusters in which astronomers observed the phenomenon of gravitational lensing, the warping of spacetime by the cluster’s gravitational field. The gravitational lens distorts light from galaxies lying far behind causing them to appear as arcs and streaks in the image.
NASA, ESA, and J. Lotz and the HFF Team (STScI)


Hubble’s three decades of exploration have forever changed our understanding of the universe. Its discoveries have won the Nobel Prize, proven Einstein’s theories, detected planets beyond our solar system, enlightened our understanding of dark matter and dark energy, and prompted questions that go beyond those we first sought to answer with it.

Hubble is a cooperative mission between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland oversees the daily on-orbit operations of Hubble, while the Space Telescope Science Institute in Baltimore, Maryland coordinates and conducts the observatory’s science operations under a contract to NASA.

Hubble's Universe Video Series

This video series celebrates Hubble's 30 years in orbit, and the astonishing secrets about our universe it revealed. While Hubble is most famous for its images of galaxies and nebulae, it also unlocked secrets here in our own solar system.

Science Themes

Hubble’s scientific mission focuses on five broad topics:

Field is filled with galaxies in colors of white, yellow, blue-white, and red; all on a black background.
Approximately 10,000 galaxies fill a small area of sky called the Hubble Ultra Deep Field. Created through the collaboration of 20 astronomers and scientists, this is the deepest image of the universe ever made at optical and near-infrared wavelengths.
NASA, ESA, S. Beckwith and the HUDF Team (STScI), and B. Mobasher (STScI)

Origin and Evolution of the Universe

Named for the astronomer, Edwin Hubble, who first found proof that the universe is expanding, the Hubble Space Telescope was initially conceived to help astronomers determine the expansion rate, structure, and age of the universe. Hubble’s observations of Type IA supernovae improved our calculations of that expansion rate, called the Hubble Constant, but they also helped show that the expansion of the universe isn’t slowing down, like astronomers expected. Instead, it is accelerating – a discovery that won the 2011 Nobel Prize in Physics.

Astronomers believe the accelerating universe is caused by “dark energy” that acts like an “antigravity” force. Unlike the normal energy we see in the universe, dark energy is invisible. It does not emit, absorb, or reflect light. We detect dark energy by its influence on the objects we can see, such as galaxies.

Like dark energy, invisible dark matter is detected through observations of how its gravity effects regular matter. Only its gravitational pull reveals its presence. Dark matter’s gravity is the glue that keeps stars, dust, and gas together in a galaxy, forming the large-scale structure of the universe.

Large galaxy clusters that act as gravitational lenses are the perfect laboratory to study dark matter. Astronomers using Hubble can map dark matter in massive galaxy clusters by how its gravity bends and distorts the light of distant galaxies located behind the cluster. The greater the concentration of dark matter in the galaxy cluster, the more dramatic its light-bending distortion will be.


The Whirlpool Galaxy is a spiral galaxy located 31 million light-years away. Also known as M51, it highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters.
NASA, ESA, S. Beckwith (STScI), and the Hubble Heritage Team (STScI/AURA)

Galaxies are the visible foundation of the universe; each one a collection of stars, planets, gas, dust, and dark matter held together by gravity. Hubble observations showed that at the heart of every galaxy is an enormous black hole whose size directly depends on the galaxy’s central bulge of stars. Hubble even gave us the first image of the large, flat accretion disk encircling a black hole.

Beyond the structure and evolution of individual galaxies, Hubble’s Deep Field observations revealed that the universe is littered with galaxies going back to a few billion years after the Big Bang. Moreover, the Deep Fields document a very active star-forming period that happened about 3 billion years after the big bang.

Hubble’s observations have greatly expanded our understanding of galaxies, giving us insight into how they form, grow, and evolve through time.

Stars and Their Environments

A string of pinkish pearls surrounds an exploded star. Black background dotted with stars. Two bright stars, with diffraction spikes, at lower left and upper right of the ring.
Supernova 1987A blazed with the power of 100 million suns for several months following its discovery on February 23, 1987. This time-lapse video sequence of Hubble images reveals dramatic changes in a ring of material around the exploded star. The images, taken from 1994 to 2016, show the effects of a shock wave from the supernova blast smashing into the ring. The ring begins to brighten as the shock wave hits it. The ring is about one light-year across.
NASA, ESA, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation), and P. Challis (Harvard-Smithsonian Center for Astrophysics)

Hubble has chronicled the lives of stars from their birth in vast clouds of gas and dust called nebulae, to their violent death throes in cataclysmic explosions called supernovae. The observatory’s infrared instruments, WFC3 and NICMOS, take advantage of longer wavelength infrared light that isn’t scattered by the obscuring dust surrounding newly-born stars. These infrared views peered into our Milky Way galaxy's heart, discovering massive infant stars gathered together in clusters. Looking at the components of their light, astronomers can determine the chemical makeup of these young stars, which helps determine how they will evolve.

Hubble's infrared vision has also studied individual stars and star clusters in nearby galaxies. These observations offer astronomers the opportunity to better understand how stars evolve in different environments.


This artist's illustration shows two Earth-sized planets (TRAPPIST-1b and TRAPPIST-1c) passing in front of their parent star.
This artist's illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. NASA's Hubble Space Telescope looked for signs of atmospheres around these planets.

When Hubble launched in 1990, the study of planets beyond our solar system wasn’t even a field of research. Two years later, astronomers discovered the first exoplanet. It wasn’t until 2008 that Hubble took the first visible-light image of a planet-like object outside of our solar system. Called Fomalhaut b, astronomers studied it with Hubble for years, and in the process noticed that something strange was happening. The planet appeared to dim with each successive observation. Then, in 2020, it seemed to vanish completely. Further research revealed that Fomalhaut b may actually be a vast, expanding cloud of dust produced in a collision between two large bodies orbiting the star Fomalhaut.

Hubble also captured the first detailed edge-on view of a large disk of gas and dust around the 20-million-year-old star Beta Pictoris. The telescope revealed that the disk’s dust distribution barely changed over 15 years, despite the fact that the entire structure is orbiting the star like a carousel. This means the disk's structure is smooth and continuous, at least over the interval between the Hubble observations.

Researchers using Hubble also directly measured the mass growth of a growing, Jupiter-sized planet called PDS 70b. The planet, which began forming approximately 5 million years ago, may be in the tail end of its formation process.

Solar System

Hubble’s high-resolution images have charted the evolution of the solar system’s planets and moons for more than 30 years.

The telescope’s observations of Pluto paved the way for the New Horizons mission by imaging features on Pluto’s surface and finding new moons around the dwarf planet. It also helped New Horizons find a target to study after Pluto. Hubble discovered the double-lobed asteroid, called Arrokoth (previously named Ultima Thule), in the Kuiper Belt in 2014. New Horizons visited this oddly shaped asteroid in 2019, making it the farthest and most primitive object in the solar system visited by a spacecraft.

This is the most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003. Hubble's view isn't sharp enough to see craters or mountains, if they exist on the surface, but Hubble reveals a complex-looking and variegated world with white, dark-orange, and charcoal-black terrain. The overall color is believed to be a result of ultraviolet radiation from the distant Sun breaking up methane that is present on Pluto's surface, leaving behind a dark, molasses-colored, carbon-rich residue. The center disk (180 degrees) has a mysterious bright spot that is unusually rich in carbon monoxide frost. This region will be photographed in the highest possible detail when NASA's New Horizons probe flies by Pluto in 2015. The Hubble images are a few pixels wide. But through a technique called dithering, multiple, slightly offset pictures can be combined through computer-image processing to synthesize a higher-resolution view than could be seen in a single exposure. This series of pictures took four years and 20 computers operating continuously and simultaneously to accomplish.

Without Hubble there would be no flyby of Ultima Thule. And without Hubble, New Horizons would not have been as productive studying Pluto's small moons. In fact, without Hubble's early images revealing how interesting Pluto's surface markings are, there might have never been a mission to explore this fascinating dwarf planet.

Alan Stern

Alan Stern

Principal Investigator, New Horizons

Requesting Time on Hubble

Hubble observes the cosmos 24 hours a day, 7 days a week, 365 days a year, collecting more than 10 terabytes of information yearly. Every moment of Hubble’s time is filled with detailed observations that are precisely scheduled and designed to maximize the science data they collect.

Anybody can apply for time with Hubble. There are no restrictions on nationality or academic affiliation, but competition is fierce. Astronomers who want to use the telescope must submit a detailed proposal to the Space Telescope Science Institute where science operations are coordinated and conducted under contract to NASA. This two-phased process is a rigorous assessment of the science and whether or not the observations are the best use of Hubble’s instruments and time. In Phase I, observers must provide a list of targets and their coordinates, what Hubble instrument(s) they want to use, how many estimated orbits it will take to acquire their observations, and the scientific justifications for why Hubble is the only telescope able to accomplish the proposal’s scientific goals.

Because observing time is measured by the number of orbits required for a successful observation, programs that need several orbits receive much greater scrutiny.

Once submitted, the proposal is anonymized and reviewed for its scientific merits by a Telescope Allocation Committee (TAC). If approved, the proposal moves on to Phase II where observers outline the details that fit within Hubble’s many constraints. These include making sure an observation in one part of the sky isn’t followed by another in the opposite part of the sky. Repeatedly moving the telescope 180 degrees would waste both time and energy, and place additional wear on Hubble’s precision pointing systems.

Impact & Benefits

Astronomical Community Impacts

As Hubble explored the boundaries of the cosmos, it was expanding horizons on Earth.

When we think about the ways that Hubble changed astronomy, we think about the big discoveries and observations. But Hubble also transformed the field of astronomy, speeding changes that were already happening and giving rise to new ones.

Learn More
Countless galaxies in orange, white, light blue, and yellow fill the screen against a black background. Faint arcs appear to curve around the image's center.
Abell 370 is a massive galaxy cluster whose immense gravity distorts and magnifies the light of galaxies behind it. Hubble used the cluster to push its sight farther in space, allowing it to see galaxies beyond its normal vision.
NASA, ESA, and J. Lotz and the HFF Team (STScI)