By Emily Levesque, University of Washington
Since 1993, the Hubble Space Telescope has been fully operational as the world’s first large optical space telescope. An immense team of scientists helped bring Hubble into the world, and the staff of the Space Telescope Science Institute in Baltimore still keep it running today. Images from Hubble have made groundbreaking discoveries across every subfield of astronomy.
A Memorable Image
One early but memorable image came in 1995, when astronomers decided to point Hubble at absolutely nothing. The observation had been Bob Williams’s idea. Williams was the director of the Space Telescope Science Institute, and as part of that position, he was granted 10% of the available telescope time on Hubble. Still, the choice to stare at nothing seemed odd at first, especially coming just two years after Hubble’s crucial repair when the telescope was still trying to make up for the lost time.
Williams explained his reasoning to his colleagues: Pointing Hubble at an empty patch of sky for a long time—more than 100 hours, in total—would make for an unprecedentedly long and deep exposure, opening the eye of the most sensitive telescope in the world in the hopes that they might capture the light from some of the faintest, faraway galaxies ever seen.
The results were astounding. The little empty patch of sky Williams had chosen, near the handle of the Big Dipper, was in fact teeming with thousands of faint galaxies. Some of the galaxies were 12 billion light-years away. The light Hubble captured had been emitted by the galaxies less than two billion years after the Big Bang and had spent the intervening 12 billion years sprinting across the universe before ultimately landing on Hubble’s mirror.
The observation became known as the Hubble Deep Field, and the experiment was repeated in 2004 and again in 2012, producing the Ultra Deep Field and the Extreme Deep Field. The Extreme Deep Field captured more than 5,000 galaxies; the most distant galaxies were 13.2 billion light-years away, showing us light emitted just 500 million years after the Big Bang.
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Hubble’s Sharp Images
Hubble also made a number of impressive discoveries closer to home. In 1994, it took some of the first images of the impact when comet Shoemaker-Levy 9 crashed into Jupiter. In 2005, it discovered Nix and Hydra, two tiny moons orbiting the dwarf planet Pluto. And in 2016, it captured what seemed to be enormous plumes of water erupting from the surface of Europa, one of Jupiter’s moons.
Hubble’s surveys of nearby galaxies are so sharp that astronomers are able to resolve individual stars within the galaxies. These images have proven to be extremely valuable, even in the many years since Hubble first captured them. Telescopes on the ground now regularly discover supernovae—the bright flashes of light from explosive stellar deaths—and pinpoint their location in distant galaxies.
By comparing the locations of these supernovae to pre-explosion pictures of the same galaxy taken by Hubble, astronomers can now identify the stars at the explosion site. Follow-up images taken with Hubble after the light from the supernova fades will sometimes reveal that a star has disappeared, allowing astronomers to identify the exact star that had died and produced the supernova.
Providing Invaluable Data
From these observations, we’ve been able to gather invaluable data about the final stages before a star’s death for the very first time. At larger distances, the Hubble Space Telescope is, appropriately, used today by multiple teams trying to measure the Hubble constant, the single number that’s used to quantify the expansion of the universe.
Teams use observations of distant Cepheid variable stars, or cleanly resolved images of stellar clusters in other galaxies, to calculate distances and refine the currently accepted value of this elusive constant. Hubble has also studied the supermassive black holes at the centers of galaxies, mapped the distribution of dark matter, and revealed that the universe likely contains 10 times the number of galaxies than we previously believed existed.
The Best Images of Nearby Stars
Hubble has also produced some of the best images ever captured of nearby stars and nebulae. Hubble’s cameras have captured unforgettable pictures of objects like the Helix Nebula—the leftover gas puffed off from a star like our Sun at the end of its life; the Crab Nebula—the explosive remnant of a supernova; and perhaps Hubble’s most iconic photo, the ‘Pillars of Creation’, an area within a nebula where new stars are born. Hubble images now show up everywhere, from the front page of The New York Times to the backgrounds of our smartphones.
Like Edwin Hubble himself, many of the researchers that use the Hubble Space Telescope study the universe using visible light, the same light that our eyes rely upon for us to see. The power of optical space telescopes may be impressive, but it’s only one window into the vast wealth of light that space has to offer.
Common Questions about the Discoveries and Images from the Hubble Space Telescope
The most memorable image from Hubble was captured in 1995. This was taken when the astronomer Bob Williams decided to point the telescope at nothing. That empty patch of space was full of faint galaxies. The Hubble Deep Field was the name given to this precious observation.
An impressive image from Hubble showed Jupiter when it got hit by the Shoemaker-Levy 9 comet in 1994. Also, one of the discoveries by Hubble was dwarf planet Pluto’s two tiny moons, Nix and Hydra, in 2005.
Hubble captured unique and unforgettable images of different objects such as the Helix Nebula and the Crab Nebula. The ‘Pillars of Creation’ also made out to be one the most iconic pictures from the Hubble Space Telescope.