The Hubble Space Telescope orbits Earth almost 550km above our heads. It travels about 27,000km per hour and take just 95 minutes to complete one orbit. Its primary mirror is 2.4 metres in diameter and weighs 828kg.


Launched by Space Shuttle Discovery on 24 April 1990, it was the first significant optical telescope to be placed in space.

Named after Edwin P Hubble (1889-1953) an American astronomer, the space telescope has made more than 1.3 million observations since its mission began.

It is a vital scientific instrument that is a result of a collaboration between NASA and ESA, and has produced beautiful images of the cosmos, but also data revealing the secrets of the Universe.

With the ability to observe in visible, infrared and ultraviolet light, Hubble can tell us a lot about the Universe.

Data collected by the space telescope has been used to write more than 16,000 peer-reviewed scientific papers and has been referenced by others over 800,000 times, a figure that grows daily by around 150 references.

It has captured the deepest ever telescopic image, peering so far into the distant Universe that it can view galaxies as they appeared just a few hundred million years after the Big Bang.

An image of the Hubble Space Telescope captured during the fourth servicing mission. Credit: NASA Goddard

Why build a space telescope?

For centuries we have been observing the stars with our feet firmly on the ground.

Though telescopes have significantly developed over time, we are still constrained in our ability to view the cosmos by Earth's atmosphere.

Just before light reaches out telescopes it has to pass through that turbulent atmosphere, which causes fine cosmic details to be lost.

We can reduce the effects of this by strategically placing telescopes high above city lights and as far beyond the hazy skies as we can, like ESO's Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

This panoramic view of the Chajnantor Plateau shows the site of the Atacama Large Millimeter/submillimeter Array (ALMA), taken from near the peak of Cerro Chico. Babak Tafreshi, an ESO Photo Ambassador, has succeeded in capturing the feeling of solitude experienced at the ALMA site, 5000 metres above sea level in the Chilean Andes. Light and shadow paint the landscape, enhancing the otherworldly appearance of the terrain. In the foreground of the image, clustered ALMA antennas look like a crowd of strange, robotic visitors to the plateau. When the telescope is completed in 2013, there will be a total of 66 such antennas in the array, operating together. ALMA is already revolutionising how astronomers study the Universe at millimetre and submillimetre wavelengths. Even with a partial array of antennas, ALMA is more powerful than any previous telescope at these wavelengths, giving astronomers an unprecedented capability to study the cool Universe — molecular gas and dust as well as the relic radiation of the Big Bang. ALMA studies the building blocks of stars, planetary systems, galaxies, and life itself. By providing scientists with detailed images of stars and planets being born in gas clouds near the Solar System, and detecting distant galaxies forming at the edge of the observable Universe, which we see as they were roughly ten billion years ago, it will let astronomers address some of the deepest questions of our cosmic origins. ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA. Links More about ALMA at ESO
This panoramic view of Chile's Chajnantor Plateau shows the site of the Atacama Large Millimeter/submillimeter Array (ALMA), taken from near the peak of Cerro Chico. Credit: ESO/B. Tafreshi (

Though these telescopes make valuable observations, they are still not immune to the effects of our atmosphere.

In 1990, we launched a telescope that would sit high upon the ultimate mountaintop: Earth orbit.

Scientific significance

Along with producing infamous stunning images, Hubble has played a significant part in discovering and characterising the mysterious dark energy that infiltrates the depths of space.

It has helped determine the age of the Universe, provided views of star formation and evidence of black holes.

In 1995, the Hubble Space Telescope captured the the iconic ‘Pillars of Creation’ image, showing newly-formed stars glowing in the Eagle Nebula.

The NASA/ESA Hubble Space Telescope has revisited one of its most iconic and popular images: the Eagle Nebula’s Pillars of Creation. This image shows the pillars as seen in visible light, capturing the multi-coloured glow of gas clouds, wispy tendrils of dark cosmic dust, and the rust-coloured elephants’ trunks of the nebula’s famous pillars. The dust and gas in the pillars is seared by the intense radiation from young stars and eroded by strong winds from massive nearby stars. With these new images comes better contrast and a clearer view for astronomers to study how the structure of the pillars is changing over time.
A high resolution image of the Eagle Nebula captured by the Hubble Space Telescope in 2014. Credit: NASA, ESA/Hubble and the Hubble Heritage Team

In 1998, astronomers published new data collected from their observations of Type Ia supernovae.

These are exploded stars that shine with a consistent brightness, so their apparent brightness can be used to deduce how far away they are.

This in turn can be used to measure distances in the Universe, and has led to the conclusion that the expansion of the Universe is actually accelerating, rather than slowing down.

Hubble has also detected a phenomenon known as gravitational lensing, which occurs because mass warps space and time, to the extent that very massive objects like galaxy clusters actually distort and bend light from distant galaxies.

Working out how much light is bent by galaxy clusters enables astronomers to calculate how much dark matter exists within those clusters.

Galaxies, galaxies everywhere - as far as the NASA/ESA Hubble Space Telescope can see. This view of nearly 10,000 galaxies is the deepest visible-light image of the cosmos. Called the Hubble Ultra Deep Field, this galaxy-studded view represents a "deep" core sample of the universe, cutting across billions of light-years. The snapshot includes galaxies of various ages, sizes, shapes, and colours. The smallest, reddest galaxies, about 100, may be among the most distant known, existing when the universe was just 800 million years old. The nearest galaxies - the larger, brighter, well-defined spirals and ellipticals - thrived about 1 billion years ago, when the cosmos was 13 billion years old. In vibrant contrast to the rich harvest of classic spiral and elliptical galaxies, there is a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. A few appear to be interacting. These oddball galaxies chronicle a period when the universe was younger and more chaotic. Order and structure were just beginning to emerge. The Ultra Deep Field observations, taken by the Advanced Camera for Surveys, represent a narrow, deep view of the cosmos. Peering into the Ultra Deep Field is like looking through a 2.5 metre-long soda straw. In ground-based photographs, the patch of sky in which the galaxies reside (just one-tenth the diameter of the full Moon) is largely empty. Located in the constellation Fornax, the region is so empty that only a handful of stars within the Milky Way galaxy can be seen in the image. In this image, blue and green correspond to colours that can be seen by the human eye, such as hot, young, blue stars and the glow of Sun-like stars in the disks of galaxies. Red represents near-infrared light, which is invisible to the human eye, such as the red glow of dust-enshrouded galaxies. The image required 800 exposures taken over the course of 400 Hubble orbits around Earth. The total amount of exposure time was 11.3 days,
This view of 10,000 galaxies is the deepest visible-light image of the cosmos. The snapshot contains galaxies of differing size and ages. The smallest, reddest galaxies may be among the most distant known, seen as they existed when the Universe was in its infancy. Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team

Hubble has imaged Jupiter's Great Red Spot and captured the first pictures of Saturn's largest moon Titan.

It helped astronomers discover moons around Pluto and rings around Uranus.

In 2001, the Hubble Space Telescope made the first direct measurement of an exoplanet's atmosphere.

In 2018, it was used to investigate the system of planets around star TRAPPIST-1; seven exoplanets that are rocky just like Earth, some of which are orbiting within their host star's habitable zone.

The same year, astronomers used Hubble to track asteroid ‘Oumuamua, the first known interstellar object to pass through our Solar System.

The NASA/ESA Hubble Space Telescope has provided images of Saturn in many colors, from black-and-white, to orange, to blue, green, and red. But in this picture, image processing specialists have worked to provide a crisp, extremely accurate view of Saturn, which highlights the planet's pastel colors. Bands of subtle colour - yellows, browns, grays - distinguish differences in the clouds over Saturn, the second largest planet in the solar system.
Hubble's view of Saturn, highlighting the planet's subtle pastel colours. The small dark spot on the images is the shadow from Saturn's moon Enceladus. Credit: Hubble Heritage Team (AURA/STScI/NASA/ESA)

Cultural significance

A telescope for the people; images released by Hubble can be accessed by all.

Click here to take a look at what the Hubble Space Telescope is viewing right now.

This NASA/ESA Hubble Space Telescope image of the cluster Westerlund 2 and its surroundings has been released to celebrate Hubble’s 25th year in orbit and a quarter of a century of new discoveries, stunning images and outstanding science. The image’s central region, containing the star cluster, blends visible-light data taken by the Advanced Camera for Surveys and near-infrared exposures taken by the Wide Field Camera 3. The surrounding region is composed of visible-light observations taken by the Advanced Camera for Surveys.
This image of the Westerlund 2 cluster and its surroundings was released to celebrate Hubble's 25th year in orbit. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

Hubble images have brought the vastness of the cosmos into our homes, and its mesmerising scenes have become a familiar part of popular culture, found on everything from textbooks and posters to postage stamps and coffee cups.

More like this

Hubble images have reinvigorated our interest in astronomy; the beauty of the cosmos is too good to ignore.

This image shows a small section of the Veil Nebula, as it was observed by the NASA/ESA Hubble Space Telescope. This section of the outer shell of the famous supernova remnant is in a region known as NGC 6960 or — more colloquially — the Witch’s Broom Nebula.
A small section of the Veil Nebula, as seen by Hubble. This section of the supernova remnant is in a region known as NGC 6960, The Witch's Broom Nebula. Credit:NASA, ESA, Hubble Heritage Team
This image of a pair of interacting galaxies called Arp 273 was released to celebrate the 21st anniversary of the launch of the NASA/ESA Hubble Space Telescope. The distorted shape of the larger of the two galaxies shows signs of tidal interactions with the smaller of the two. It is thought that the smaller galaxy has actually passed through the larger one.
This object is actually two different galaxies that have merged to form a single object known as Arp 273. It is thought that the smaller galaxy has actually passed through the larger one. Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

The celestial comeback kid

However, Hubble's journey was not always plain sailing, it is fondly known as the comeback kid of celestial imaging.

Scientists and engineers alike were dismayed when the first images were sent back from Hubble shortly after its launch, and were found to be blurry.

The Hubble Space Telescope's first ever image. Despite the aberration in Hubble's mirror, the space telescope's image (right) offers more clarity then what can be achieved with ground-based observations (left). Credits: Left: E. Persson (Las Campanas Observatory, Chile)/Observatories of the Carnegie Institution of Washington; Right: NASA, ESA, and STScI

After lengthy investigations it was found that there was a spherical aberration on the primary mirror, causing blurring around the edges.

This meant that images would always be blurred due to light bouncing off the mirror surface and not being properly focussed.

However, Aden Meinel a top telescope designer, worked out how to adjust for the aberration through curving the mirrors that reflected light from Hubble's primary mirror, thereby cancelling out the distortion of the primary mirror.

Hubble's first service mission was carried out in 1993 using NASA's Space Shuttle Atlantis.

The mission saw new instruments installed and the aberration corrected.

The success of the mission was conveyed in the images that were sent back to Earth.

Hubble then went back to producing iconic images of galaxies, nebulae, stars and more.

This new image shows the dramatic shape and colour of the Ring Nebula, otherwise known as Messier 57. From Earth’s perspective, the nebula looks like a simple elliptical shape with a shaggy boundary. However, new observations combining existing ground-based data with new NASA/ESA Hubble Space Telescope data show that the nebula is shaped like a distorted doughnut. This doughnut has a rugby-ball-shaped region of lower-density material slotted into in its central “gap”, stretching towards and away from us.
A Hubble image of the Helix Nebula. Credit: NASA, ESA, and C. Robert O'Dell (Vanderbilt University).

The space telescope was placed in a strategically low Earth orbit to enable access to it, so that astronauts could visit and correct any defects or install new instruments as technology has improved over the years.

In total Hubble has undergone five servicing missions carried out by astronauts using NASA's now defunct Space Shuttle.

The first took place in 1993 and the final servicing mission took place in 2009.

Astronauts Michael Good and Michael Massimino pictured during the final Hubble servicing mission. Credit: NASA
Astronauts Michael Good (top) and Mike Massimino (bottom) pictured during the final Hubble servicing mission. Credit: NASA

The future

Though originally designed to last for 15 years, Hubble is currently in its 29th year of operation.

It may already be past its expiration date, yet NASA estimates that it will continue to perform well into the next decade.

Hubble will soon be joined by its 'big brother' the James Webb Space Telescope (JWST), and working in conjunction with one another they will continue to survey the cosmos.

Unlike Hubble, the JWST will examine the Universe in infrared only and its orbit will be about 1.6 million km from Earth, making service missions impossible.


The JWST is due to launch on the Ariane 5 rocket from French Guiana in 2021 and continue the legacy of the Hubble Space Telescope.