A telescope does not need to take a visible-light photograph to reveal something extraordinary. Some watch for X-rays from superheated matter; others search for tiny dips in starlight or map the faint glow left by the early universe. Together, space observatories have made the sky much richer than it appears to human eyes.
These ten space telescopes and observatories were selected for their distinctive scientific roles, recognizability and educational value. They are arranged as a guided tour from detailed images to surveys and the early universe—not as a ranking of scientific importance. Both retired and operating missions are included. Mission status can change; the descriptions below emphasize established work rather than promising future results.
1. Hubble Space Telescope — a familiar eye on a changing universe
Launched in 1990, Hubble brought distant galaxies, stellar nurseries and planetary atmospheres into unusually sharp focus from above much of Earth’s atmosphere. Its images are famous, but its value goes beyond their beauty: repeated observations let astronomers measure change and compare objects at different stages of their lives.
Hubble observes multiple wavelengths, including visible and ultraviolet light. That makes it a useful complement to infrared-focused Webb, rather than simply an older version of the same instrument. Its longevity also shows the value of servicing: astronauts repaired and upgraded Hubble on five missions, the last in 2009.
2. James Webb Space Telescope — looking through dust in infrared
Launched in 2021, Webb specializes in infrared observations. Infrared light can pass through some dusty regions that obscure visible light, allowing astronomers to investigate star-forming clouds and other hidden structures. Webb also studies distant galaxies and planets orbiting other stars.
The distinction is important: Webb does not literally photograph the Big Bang. It collects light emitted by objects, and the light from extremely distant galaxies has travelled for a long time before reaching its instruments. That makes those observations a way to study earlier eras of cosmic history.
3. Chandra X-ray Observatory — the high-energy universe
Some of the universe’s most dramatic environments are best studied in X-rays. Chandra, launched in 1999, observes X-rays produced by extremely hot matter, including material around black holes and the remnants of exploded stars.
A visible-light image may show a graceful galaxy while X-ray data highlights energetic gas in and around it. Combining those views helps astronomers distinguish structures that would otherwise be invisible. Chandra is one of NASA’s four Great Observatories, designed to examine the universe in different parts of the electromagnetic spectrum.
4. Spitzer Space Telescope — uncovering a cooler cosmos
Spitzer, another Great Observatory, studied infrared light from 2003 until its retirement in 2020. Its targets ranged from dusty regions where stars form to distant galaxies and planets beyond our solar system.
Infrared astronomy is especially useful for studying cool objects and dust that glow less conspicuously in visible light. Spitzer’s observations helped establish a foundation for later infrared work, including Webb’s more detailed investigations. Its data remain a resource even though the spacecraft no longer collects new observations.
5. Kepler Space Telescope — a census of planets
Before Kepler, astronomers already knew of planets beyond the solar system. The mission, launched in 2009, transformed the scale of the search by watching stars for small, repeated drops in brightness that can occur when a planet crosses in front of its star.
Those dips are clues, not automatic proof: candidate signals need further analysis. Kepler’s observations enabled the discovery of thousands of planets and showed that planets are common in our galaxy. The spacecraft was retired in 2018, but its archive continues to support research.
6. TESS — searching nearby stars for transits
The Transiting Exoplanet Survey Satellite uses the same basic transit idea as Kepler, but surveys large areas of sky for planets around relatively nearby stars. Launched in 2018, TESS offers a way to find targets that other telescopes can investigate in greater detail.
A transit reveals a recurring change in brightness; additional observations can help determine whether a candidate is a planet and characterize it. TESS also records other changing objects, from pulsating stars to distant supernovae. Its wide survey illustrates how planet hunting can create a broader astronomical data set.
7. Fermi Gamma-ray Space Telescope — catching extreme events
Launched in 2008, Fermi observes gamma rays, an exceptionally energetic form of light. Its targets include pulsars, active galaxies and gamma-ray bursts. These are not ordinary scenes viewed through a bigger lens: the signals trace processes that accelerate particles to immense energies.
Fermi also discovered vast structures now called the Fermi bubbles above and below the plane of the Milky Way. The observatory demonstrates why viewing the sky in different wavelengths can expose structures that visible-light astronomy alone would not show in the same way.
8. XMM-Newton — collecting X-rays from cosmic objects
The European Space Agency’s XMM-Newton, launched in 1999, combines X-ray observations with an optical/ultraviolet telescope. Scientists use it to investigate objects ranging from galaxy clusters to planets in our solar system.
X-rays offer evidence about hot gas and energetic processes; optical and ultraviolet measurements add context from other kinds of light. XMM-Newton and Chandra both study X-rays, but their instruments offer different observational strengths. Using more than one observatory can therefore provide a fuller picture than either alone.
9. COBE — mapping ancient light
The Cosmic Background Explorer, or COBE, measured the cosmic microwave background: radiation released in the early universe that has cooled and stretched as the universe expanded. Launched in 1989, it was decommissioned in 1993.
Its measurements gave scientists evidence about the early universe and mapped tiny variations in this background. Those variations matter because they are connected to the seeds from which later cosmic structure developed. COBE’s legacy is a reminder that an astronomy map can be as consequential as a dramatic photograph.
10. Planck — refining the early-universe map
ESA’s Planck mission made precise measurements of small variations in the cosmic microwave background. Launched in 2009 and decommissioned in 2013, it extended the study of this ancient light with a more detailed view.
The background is not a picture of the universe at the instant of the Big Bang. It dates from roughly 380,000 years later, when the universe had cooled enough for light to travel freely. By studying its patterns, researchers can test models of the universe’s composition and evolution.
Why different telescopes matter
No single telescope sees everything. Hubble’s detailed images, Kepler’s long watch on stars and Planck’s microwave maps answer different questions with different signals. The strongest picture of the universe comes from combining those perspectives—and remembering that each is evidence to interpret, not a complete view by itself.
For a closer look at our cosmic neighborhood, explore 10 strange moons in the solar system.