From James Webb to Euclid, here are top 10 most powerful space telescopes

Indian Express

01-07-2025

One of the many breakthroughs of the scientific community remains the invention of space telescopes — telescopes that orbit above the Earth's atmosphere to observe the Universe (planets, stars, galaxies) closely with significant clarity.
These telescopes have an important advantage over ground-based telescopes in that they have access to a wider electromagnetic spectrum, enabling them to detect the wavelengths of light (such as X-rays, gamma rays, infrared) which generally gets absorbed or reflected by the Earth's atmosphere, Las Cumbres Observatory stated.
The first ever space telescope, the Orbiting Astronomical Observatory 2 (OAO-2), was launched into the low Earth orbit in 1968 aboard an Atlas-Centaur rocket, as per the National Space Centre. For the next four years following its placement, as per the Centre, the OAO-2 beamed data back to scientists on Earth, including the first observations of astronomical objects in ultraviolet light.
There are more than 30 space telescopes which are currently active, and here, we take a look at the 10 most powerful of them:
1. James Webb Space Telescope
Launched in the year 2021, the James Webb Space Telescope is the largest and the most powerful observatory, as per the National Aeronautics and Space Administration (NASA).
One of the most significant endeavours of the Webb telescopes include studying every phase in the history of our Universe, which ranges from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System, as per NASA.
The Space Administration has referred to the Webb as the 'premier observatory of the next decade'. The telescope observes the cosmos in infrared using highly sensitive instruments. The agencies overlooking the JWST are NASA, European Space Agency (ESA) and the Canadian Spaece Agency (CSA).
2. Hubble Space Telescope
Launched in April 1990, the Hubble Space telescope has proven to be a testament to the revolutionary scientific instruments that have propelled our understanding with their remarkable discoveries.
Its design, technology and serviceability have made it one of NASA's most transformative observatories, NASA's website states hailing the telescope's achievements. From determining the atmospheric composition of planets around other stars to discovering dark energy, Hubble has changed humanity's understanding of the universe, the website added.
Operated by the agencies NASA and ESA, the Hubble observes the cosmos in untraviolet, visible and near-infrared, from the low Earth orbit.
3. Chandra X-ray observatory
Launched in the year 1999, the Chandra X-ray observatory, NASA's flagship mission for X-ray astronomy, detects X-ray emissions from very hot regions of the universe such as exploded stars, clusters of galaxies, and matter around black holes, as per the website.
Operated solely by NASA, it is the 'most powerful X-ray telescope, with eight times the resolution of any previous X-ray telescope and able to detect sources more than 20 times fainter,' the website describes.
Here are some mind-blowing facts about the Chandra observatory, according to the Harvard University:
– Chandra can observe X-rays from particles up to the last second before they fall into a black hole.
– At 45 feet long, Chandra is the largest satellite the shuttle has ever launched.
– The electrical power required to operate the Chandra spacecraft and instruments is 2 kilowatts, about the same power as your hair dryer.
– STS-93, the space mission that deployed Chandra, was the first NASA shuttle mission commanded by a woman.
4. Spitzer Space Telescope
Launched in 2003, the Spitzer Space Telescope was the final mission in NASA's Great Observatories Program — a unit of four space-based observatories, each observing the Universe in a different kind of light, as per the Caltech's Cosmos website.
Spitzer, though retired in 2020, continues to remain the most influential as it allowed scientists to peek into cosmic regions which were hidden when observed through optical telescopes.
Operated by NASA, its observations, in infrared light, included dusty stellar nurseries, centers of galaxies, and starlight from very distant galaxies at the edge of the Universe.
5. Planck Space Observatory
Planck was ESA's first mission to study the Cosmic Microwave Background (CMB), the relic radiation from the Big Bang, which occurred about 14 thousand million years ago, according to the operator's website.
Launched in 2009, Planck measured the temperature variations across the microwave background with much better sensitivity, angular resolution and frequency range than any previous satellite, giving astronomers an unprecedented view of our Universe when it was extremely young, just 300 000 years old, the website highlighted.
Planck worked perfectly for 30 months, completing five full-sky surveys with both its instruments. Able to work at slightly higher temperatures than HFI, the Low Frequency Instrument (LFI) continued to survey the sky for a large part of 2013, providing even more data to improve the Planck final results, before being turned off later that year, as per the ESA website.
6. Gaia
Launched in 2013, Gaia has made more than three trillion observations of two billion stars and other objects throughout our Milky Way galaxy and beyond, mapping their motions, luminosity, temperature and composition, the European Space Agency highlighted over its website.
The telescope's extraordinarily precise three-dimensional map will provide the data needed to tackle an enormous range of important questions related to the origin, structure and evolutionary history of our galaxy.
While the telescope ended its observations this year in January, the telescope was responsible for creating a 3D map of over 1 billion stars in the Milky Way, leading the ESA, its operator, to call it the 'billion star surveyor.'
7. Fermi Gamma-ray Space Telescope
NASA's Fermi Gamma-ray Space Telescope is a powerful space observatory that detects gamma rays, the most energetic form of light, the NAS website states.
Launched in 2008, Fermi enables scientists to address questions revolving around 'crushed stellar remnants like pulsars and the origin of high-energy charged particles called cosmic rays to stellar explosions known as gamma-ray bursts,' it stated.
As per NASA's observations, Fermi data has revealed a vast new component of our galaxy known as the Fermi Bubbles, a structure that spans 50,000 light-years and likely formed as a result of an outburst from the monster black hole at the center of our galaxy.
According to the National Space Centre, Fermi was initially expected to operate (under NASA) for five years, but the mission has been extended with no signs of stopping any time soon.
8. TESS (Transiting Exoplant Survey Satellite)
Launched in 2018 as a follow-up to Kepler, NASA's TESS is responsible for discovering exoplanets, that is, worlds beyond our solar system.
During the course of its extended observations of the sky under optical wavelengths, TESS finds and monitors all types of objects that change in brightness, from nearby asteroids to pulsating stars and distant galaxies containing supernovae.
In July 2020, TESS finished its primary mission, imaging about 75 per cent of the starry sky as part of a two-year-long survey, the NASA website highlighted. While capturing this giant mosaic, TESS found 66 new exoplanets.
9. Euclid Space Telescope
Euclid is an ESA (European Space Agency) mission with critical contributions from NASA that aims to explore two of the biggest mysteries about the universe today: dark matter and dark energy, the NASA website highlighted.
To study the evolution of the 'dark universe,' Euclid will make a 3D map of the universe, it added. It will do so by observing billions of galaxies out to 10 billion light-years, across more than a third of the sky.
Recently launched in 2023, Euclid is designed to tackle some of the most pertinent questions related to the Universe, including, what is the structure and history of the cosmic web? How has the expansion of the Universe changed over time? What is the nature of dark matter and dark energy?
The telescope observes the cosmos in visible and near-infrared light. The mission's lifetime is six years, with the possibility of extension, as per the ESA website.
10. XRISM (X-ray Imaging and Spectroscopy Mission)
NASA has partnering with JAXA (Japanese Aerospace Exploration Agency) on the XRISM mission to study celestial objects that emit X-rays, its website stated.
Launched in 2023, the mission aims to investigate big cosmic questions such as how the largest structures in the universe came to be, what happens to matter under extreme gravitational force, and how high-energy particle jets work. It's purpose involves studying the dynamics of hot gas in galaxy clusters, and black holes.
In one of its significant breakthroughs, XRISM has managed to capture the most detailed portrait yet of gases flowing within Cygnus X-3, one of the most studied sources in the X-ray sky, according to NASA.