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30 years of Hubble: Images and discoveries that shaped astronomy

Posted on by ScIU Editorial Team

To celebrate International Astronomy Day (May 7), we are highlighting this post from ScIU’s archives! It was originally published by Jennifer Sieben in April 2020 and has been lightly edited to reflect current events.

April 24th, 2020 was the 30th anniversary of the launch of perhaps the most famous telescope: the Hubble Space Telescope. Orbiting the earth, this telescope has changed the way astronomers and the public alike view the universe. With over 1.4 million observations, providing data for more than 16,000 peer-reviewed scientific papers, Hubble has exceeded expectations.

Stunning Images

If you have ever seen an image of a spiral galaxy as a desktop background, textbook cover, or in the background of an inspirational quote, the chances are high that it was taken by Hubble. Images like these highlight the spectacular beauty of our universe and are often a great tool to encourage interest in science. Hubble images demonstrate that science can be more than a mixture of numbers and buggy code; it can also be spiral galaxies that show where new stars are being formed and remind us that the mystery of galaxy formation is still unsolved. New data received from Hubble constantly challenges our preconceived notions about the universe. 

A bright spiral galaxy with two prominent arms of red with a blue glow of stars. The center is bright white.
A Hubble image of the Whirlpool Galaxy, featuring pink star-forming regions and brilliant blue strands of star clusters. Image taken in 2011. Image credit: NASA/ESA, S. Beckwith (STScI), and the Hubble Heritage Team (STScI/AURA).

Planned Science

Hubble’s main science objective was to determine the size and age of the universe. To do this, astronomers measure the changing brightness of Cepheid variable stars, stars that have a varying brightness that follows a regular shape, but the frequency of the pattern is dependent on the actual luminosity of the star. Astronomers use the frequency of this pattern to determine how far away a galaxy is. Hubble’s large mirror helped detect Cepheid variable stars at farther distances, and the expansion and age of the universe was confirmed. Moreover, this same high resolution allowed for even more distant supernovae observations that showed the universe’s expansion is accelerating. This completely changed the field of cosmology and led to the 2011 Nobel Prize in Physics.

A spiral galaxy with multiple arms. Light blue arms against a black background with a bright white center. A bright, pale blue star to the right of the center is in stark contrast to the darker arms.
A NASA/ESA Hubble Space Telescope (HST) view of the spiral galaxy NGC 4603, the most distant galaxy in which Cepheid variables have been found. Image taken in 1999. Image credit: Jeffrey Newman (University of California Berkeley) and NASA/ESA.
A disk galaxy is seen side-on like a dusty frisbee. Dark clouds are seen against a dark background with a purple glow coming out from the center of the disk. In the lower left, a bright white dot shines.
Hubble Space Telescope image of supernova 1994D (lower left) in galaxy NGC 4526. Image taken in 1999. Image credit: NASA/ESA, The Hubble Key Project Team, and The High-Z Supernova Search Team.

Closer to home, Hubble was also instrumental in the New Horizons mission. Hubble took images of the Pluto system from the early 1990s to 2010 in order to prepare for the flyby of New Horizons. And it was a good thing it did: Hubble discovered four of Pluto’s moons, and the mission scientists used these data to avoid a collision. 

After capturing gorgeous images of Pluto, New Horizons then flew past the duck-shaped Kuiper Belt Object Arrokoth, another object discovered by Hubble. Without the space telescope, we never would’ve gotten to see this bizzare object and the mission would’ve ended much sooner. 

Five fuzzy white dots are seen on a blackish-blue background. The largest dot is in the center, labelled as Pluto. The others are further out and white circles are drawn on to demonstrate the orbits of the outer four planets.
Hubble discovered Pluto’s four small moons: Nix, Hydra, Styx, and Kerberos. Image credit: NASA/ESA and M. Showalter (SETI Institute).

Unexpected Discoveries

Astronomy is a science of many surprises, and putting a telescope in space only revealed more. One such image was the Hubble Deep Field. The telescope pointed its camera to a part of the sky that appeared practically empty to all previous observations. And then, it left the shutter open for ten days, collecting all the light from a seemingly empty part of space. By using a long exposure, just like a traditional camera on Earth, astronomers were able to see what was hiding in the dark. This image is only 1/30th the size of the full moon, and yet it revealed 3,000 galaxies, several hundred of which had never been seen before.

The result was ground-breaking, so astronomers did it again (Hubble Ultra Deep Field) and again (eXtreme Deep Field), each time using longer exposure times and upgraded instruments.

Several hundred galaxies of all shapes and colors shine against a black background.
The new full-color eXtreme Deep Field image is even more sensitive than the Hubble Deep Field and contains about 5,500 galaxies, even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness of what the human eye can see. It combines 10 years of data. Image credit: NASA/ESA; G. Illingworth, D. Magee, and P. Oesch (University of California Santa Cruz); R. Bouwens (Leiden University); and the HUDF09 Team.

Due to the long lifetime of the Hubble Space Telescope, astronomers have been able to view the unprecedented: motion and changes in the shapes of stellar jets over time. Stellar jets are caused by gas swirling into newly forming stars, some of which is then channeled by magnetic fields and shot from the poles of the spinning stars in opposite directions at supersonic speeds. Looking in the infrared, these energetic jets of glowing gas emitted from young stars can be seen in unparalleled detail. Many observations over time have been invaluable to understanding the cause of these jets and the environment in which stars are born. 

On the left is a blue wisp in a bit of a squiggle. On the right is a bright white cloud. There is a very faint wisp of light connecting them. As the year progresses, the two main components move apart.
The glowing, clumpy streams of material shown moving left and right in this Hubble image are the signposts of star birth. A young star in the center of the image is hidden by dust. As they move through space, these outflows create bow shocks and ripples as they collide into other clouds of material in the neighborhood of the star. Image credit: NASA/ESA, P. Hartigan (Rice University), and G. Bacon (STScI).

What’s Next?

Hubble lasted many more years than expected, with many shuttle missions providing repairs to the aging equipment. But as the telescope enters its 4th decade of science, it will be retired soon. There is no one telescope planned that will replace this grand observatory, but a combination of the James Webb Space Telescope (JWST) and the Wide Field Infrared Survey Telescope (WFIRST) may come close. Both telescopes will have greatly advanced camera technology, in addition to larger mirrors that can collect more light (similar to leaving a camera shutter open longer, leading to greater depth and detail). Together, they will cover the wavelength range that Hubble operated in, while also reaching beyond. I cannot wait for the next generation of space telescopes to surpass Hubble and illuminate even more wonders of the universe. 

 

Edited by: Riddhi Sood and Chloe Holden

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