Top 10 Largest Space Telescopes in Orbit

Space telescopes have revolutionized modern astronomy, allowing scientists to peer deeper into the cosmos than ever before. As space agencies have gained experience launching large payloads into orbit, telescope size and imaging power has steadily increased over the past three decades.

Let‘s countdown the current top 10 largest telescopes in space by weight, from the pioneer Hubble Space Telescope to newcomers like the James Webb.

10. Planck – 452 lbs

The Planck space observatory clocks in at number 10 on our list. Launched in 2009 by the European Space Agency (ESA), this compact telescope weighed only 452 lbs but played a big role in our understanding of the early universe.

Orbiting the Earth‘s second Lagrange point beyond the moon, Planck imaged the first light of the universe, known as the cosmic microwave background. By mapping tiny temperature variations within this radiation, Planck provided precise data on the age, composition, and geometry of the cosmos. Its detailed all-sky maps also shed light on elusive dark matter.

Planck exceeded its planned 2-year mission, finally being shut down in 2013 after over 4 years of game-changing observations.

9. CoRoT – 660 lbs

The ESA‘s planet-hunting CoRoT comes next at 660 lbs. Launched in 2006, CoRoT searched for exoplanets by detecting the tiny dips in a star‘s brightness caused when a planet passes in front. Within two years, CoRoT had discovered its first rocky super-Earth and several hot gas giants.

CoRoT paved the way for more advanced exoplanet missions like NASA‘s Kepler and TESS spacecraft. After its initial 3-year mission concluded, the trailblazing telescope continued observations for another 3 years before running out of fuel and being decommissioned in 2014.

8. Herschel Space Observatory – 694 lbs

In 2009, ESA launched the Herschel Space Observatory to study the cool universe with sensitive infrared instruments. At launch, its 3-foot wide mirror made it the largest infrared space telescope ever deployed at that time.

Although its mission was shorter than most on this list at just over 4 years, Herschel transformed our view of star and galaxy formation by peering through thick veils of cosmic dust that block visible light. It examined hundreds of dusty stellar nurseries within the Milky Way and observed early galaxies forming shortly after the Big Bang.

7. Kepler Space Telescope – 1,052 lbs

NASA‘s planet-hunting Kepler telescope has made perhaps the biggest impact of all the telescopes on this list. Launched in 2009, Kepler discovered over half of the 4,500+ exoplanets currently known thanks to its 95 megapixel camera that could detect tiny brightness dips from orbiting worlds.

Among its many notable discoveries, Kepler found the first Earth-sized planet in a habitable zone and revealed that small, potentially rocky worlds are extremely common throughout our galaxy.

After facing multiple mechanical failures, Kepler exceeded its 3.5-year mission plan by over 5 years before finally running out of fuel in 2018, having massively advanced our understanding of exoplanets.

6. Neil Gehrels Swift Observatory – 1,858 lbs

Still going strong after 18 years in orbit, NASA‘s Neil Gehrels Swift Observatory catches high-energy explosions in the act. Swift launched in 2004 to study fleeting gamma-ray bursts: the biggest explosions since the Big Bang.

With its wide-angle cameras that can swiftly turn to capture short-lived events, Swift has observed over 1,100 gamma-ray bursts and been pivotal in unraveling their origins. Researchers use Swift to probe the early universe and gain insights into black holes, neutron stars, supernovae, and other exotic astrophysical phenomena.

5. Spitzer Space Telescope – 1,877 lbs

From cool dust clouds to hot exoplanets, NASA‘s Spitzer Space Telescope has been a leader in infrared astronomy for the past two decades after its 2003 launch.

Spitzer was the first telescope to directly capture light from an exoplanet and went on to reveal key details about hot Jupiters, super Earths, and other worlds. With its heat-sensing vision, Spitzer peered through galactic dust to see stars and planetary systems forming, explored the structure of galaxies, and imaged our Milky Way’s core.

After more than 16 years far surpassing its planned mission lifetime, Spitzer was retired in early 2020. NASA‘s James Webb Space Telescope has taken over Spitzer’s duties as our leading infrared eye on the universe.

4. Fermi Gamma-ray Space Telescope – 4,303 lbs

If you want to study the highest energy light in existence, gamma-rays, the Fermi telescope is NASA’s flagship. Launched in 2008, the nearly 10 by 8 feet observatory packs high-tech gamma cameras and monitors to catch the universe’s most powerful explosions.

Fermi revelas where huge amounts of energy are being unleashed, like around supermassive black holes swallowing matter or when neutron stars collide. It can also track jets of plasma streaming from active galactic nuclei and map out bubbles of gamma rays permeating our galaxy from ancient supernovae.

Originally slated for a 5-year tour of duty, Fermi remains in action over a decade later, still astounding astronomers with new finds like the recent discovery of a record-smashing gamma-ray megaflare.

3. Chandra X-ray Observatory – 9,561 lbs

When it comes to observing the x-ray universe, NASA’s Chandra X-ray Observatory is unrivaled. The third of NASA‘s Great Observatories to launch, Chandra has amazed astronomers for over two decades after first reaching orbit in 1999.

With its ability to capture high-energy emissions from extreme cosmic events, the school bus-sized Chandra provides insight into astronomical phenomena too hot and violent to study in visible light: exploding stars, matter swirling into black holes, shockwaves from stellar explosions, and the superheated gas clouds permeating galaxy clusters.

Images from Chandra’s sharp x-ray vision have greatly advanced our comprehension of dark matter, dark energy, black holes, and cosmic evolution. For over 15 years past its initial 5-year mission plan, this formidable flagship telescope continues to push the boundaries of high-energy astrophysics.

2. James Webb Space Telescope – 13,168 lbs

As the biggest space telescope ever put into orbit, you would expect big things from NASA’s James Webb Space Telescope, and it has certainly delivered. Since its launch late last year, Webb’s sheer size and scientific capabilities have allowed it to far surpass every other infrared telescope.

Unfolding to over 21 feet in width, Webb is equipped with sensors, mirrors, and sunshields engineered to detect the faintest heat signals from the first stars and galaxies. By capturing infrared light from 13 billion years ago, this giant orbiting observatory is illuminating the earliest epochs of cosmic history as never before.

In the coming years, Webb’s advanced instruments will also analyze atmospheres of exoplanets, peer through obscuring nebulae in our galaxy, and survey galaxies back to not long after the Big Bang. Astronomers will rely on this highly complex, $10 billion telescope to transform our knowledge of the infrared universe throughout its planned 5 to 10-year operational lifespan.

1. Hubble Space Telescope – 24,500 lbs

Claiming the title for largest space telescope is NASA‘s Hubble Space Telescope. Launched in 1990 aboard the space shuttle Discovery, Hubble was the first major optical telescope put into orbit.

During its more than 30-year career, Hubble has made over 1.5 million observations and spawned countless discoveries that have fundamentally changed astronomy. Its crisp images in visible and ultraviolet light have enabled groundbreaking research on black holes, dark matter, distant galaxies, exoplanets and more.

Hubble’s stunning cosmic photos have also captivated the public for decades. From vibrant stellar nurseries to glittering galaxy clusters spanning billions of lightyears, Hubble’s imagery has fueled our imaginations and inspired generations.

Now over three decades into its planned 15-year mission and still going strong, NASA’s flagship Hubble Space Telescope remains the largest and most scientifically impactful space telescope in operation. But with the newly arrived James Webb gaining steam, Hubble may soon have to pass the torch as our most powerful eye on the universe.

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