Today we celebrate the 25th anniversary of the launch of the Hubble Space Telescope. Hubble is hardly the first telescope: ever since Galileo, astronomers have used telescopes to study the sources of light from the universe, near and far. Stars, galaxies, nebulae, and planets too far away for humans to visit become accessible by studying the information contained in their radiation that travels to our telescopes. And yet after a journey of sometimes thousands or even billions of light-years, the light from these distant sources can be blurred or obscured by Earth’s atmosphere before it reaches our telescopes on the ground. The Hubble Space Telescope, launched in 1990, solves this dilemma by orbiting the Earth above the atmosphere, providing crystal-clear images that have opened our eyes to a universe barely imagined before.
So what news has the light from the Cosmos brought us, via the Hubble telescope?
We first notice magnificent beauty. The exquisite angular resolution that Hubble can achieve allows us to see individual stars in dense clusters, revealing rich varieties of stars, like gemstones: red and blue, bright and faint. Astronomers study populations of stars to determine their age, composition, and how they formed. Stars and interstellar gas make up galaxies, which themselves can be beautiful spiral pinwheels, rotating and sometimes even merging with one another.
Then there is the sheer magnitude of the universe. There are at least 200 billion stars in our own Milky Way galaxy alone, and hundreds of billions of other galaxies within the observable universe. Hubble’s sensitive camera is allowing us to see some of the faintest, most distant galaxies ever detected. The light from these ancient objects has traveled over 13 billion years to get to us, traversing space that is itself stretching and expanding, reddening the light that we see. Light from some distant galaxies is actually magnified, and its path altered, by the gravitational effects of massive clusters of galaxies it passes along its journey to us. This “gravitational lensing” effect can distort the appearance of distant galaxies into long arcs and multiple apparitions. Astronomers measure that distortion to study the distribution of mysterious invisible “dark matter” in the foreground clusters.
The light Hubble receives is also telling us of incredible activity in the universe. We see our own solar system buzzing with activity, such as aurorae on Uranus and Saturn, and asteroids colliding. We also see magnificent clouds of interstellar dust and gas where infant stars are vigorously forming deep inside. Hubble’s ability to detect infrared light from these warm young stars enables us to see into these hidden nurseries. Light from more distant galaxies, as they stretch away from us with the expansion of space, is even showing us that this expansion is accelerating: some kind of “dark energy” is pushing the universe apart.
So the International Year of Light and Light-based Technologies 2015 is a perfect time to celebrate how the Hubble Space Telescope, and the technology and ingenuity that brought it about, is revealing a universe of remarkable magnitude, activity, and beauty. Hubble observations continue to transform our understanding of the amazing universe in which we abide. Happy 25th Birthday, Hubble!
Jennifer Wiseman is the NASA Senior Project Scientist for the Hubble Space Telescope. She is a senior astrophysicist at Goddard Space Flight Center, where she studies the formation of stars using visible-light, radio, and infrared telescopes. She previously headed Goddard’s Laboratory for Exoplanets and Stellar Astrophysics, where scientists are developing techniques for detecting and studying planets outside of our solar system. Dr. Wiseman is interested in science public engagement and science policy. She is a former Councilor of the American Astronomical Society and a program director for the American Association for the Advancement of Science. She also served as a Congressional Science Fellow for the American Physical Society. Dr. Wiseman enjoys giving public talks about the excitement of astronomy and scientific discovery. She grew up on an Arkansas farm enjoying late night walks under dark starry skies.