After 35 years, the Hubble Space Telescope is still churning out hits. In just the last year or so, scientists have used the school bus–sized observatory to confirm the first lone black hole, reveal new space rocks created by a NASA asteroid-impact mission and pinpoint the origin of a particularly intense, mysterious burst of radio waves.
These findings are a testament to the fact that there’s still plenty of science for the telescope to do. And there are some observations that simply can’t be done with any other telescope, including Hubble’s younger sibling, the James Webb Space Telescope.
To date, Hubble has observed more than 100 million objects ranging from comets in our solar system to dying stars in the Milky Way to distant galaxies that formed not long after the Big Bang. Researchers have collectively written more than 21,000 peer-reviewed publications using Hubble data (this astronomer–turned–science journalist wrote two of them).
Simply put, “it’s been a huge asset,” says Peter Senchyna, an astronomer at Carnegie Science Observatories in Pasadena, Calif.
Hubble can see what other telescopes cannot
Hubble was launched into space aboard the space shuttle Discovery in 1990 and shepherded into low Earth orbit by astronauts. It’s been there ever since, at an altitude of roughly 515 kilometers above Earth’s surface. From that vantage point, Hubble has a nearly unobstructed view of the cosmos, largely free of the absorbing and blurring effects of our planet’s atmosphere.
A key attribute that differentiates Hubble from other telescopes is that it can collect data in the ultraviolet part of the electromagnetic spectrum. That’s crucial for understanding celestial objects that have temperatures measuring tens of thousands of degrees Celsius or more, such as massive stars and the chaotic regions near black holes. UV light is “telling us something about the hottest objects,” Senchyna says.
Telescopes on the ground cannot observe UV light from space since our planet’s atmosphere blocks most of it. (That’s a good thing, given that UV rays can cause cells to mutate and trigger cancer.) While some other space-based telescopes are sensitive to UV light, their images are much fuzzier; Hubble can resolve objects one-tenth as large as these other telescopes can. And the James Webb Space Telescope, also renowned for spectacular images, isn’t sensitive to UV light at all. (It excels at observing in infrared, which allows it to probe dust-enshrouded objects and particularly distant galaxies.)
“At shorter ultraviolet and optical wavelengths, [Hubble] is still the best thing we’ve ever done as a species in terms of sensitivity and resolution,” says Kevin Hainline, an astronomer at the University of Arizona’s Steward Observatory in Tucson.
Every year, hundreds of scientists propose new observations using Hubble, but only about 20 percent of those proposals are granted. Aoife Brennan, an astronomer at Trinity College Dublin, is among the lucky few. She studies debris disks, amalgams of rock and dust akin to our solar system’s Kuiper Belt, in other planetary systems. And on April 24 — exactly 35 years to the day after Hubble was launched — the telescope will begin observing one of Brennan’s targets: a debris disk roughly 200 light-years from Earth. Brennan hopes that the new data will help reveal the prevalence of gas in debris disks, which has implications for how planets form.
Hubble images continue to inspire
Even people who don’t study the sky for a living appreciate Hubble, Brennan says. “When I say that I work with Hubble data, all of my friends and family immediately know what that is,” she says. “We’re very used to seeing Hubble images.”
Joe DePasquale helps to create some of those images. DePasquale is the principal science visuals developer at the Space Telescope Science Institute, the Baltimore-based organization that coordinates Hubble’s science operations. He and colleagues select, process and colorize Hubble observations for release to the press and the general public.
Raw data are collected at ultraviolet, visible and near-infrared wavelengths and must be corrected to account for artifacts caused by, for instance, cosmic rays, DePasquale says. “I take data from the telescope and turn it into beautiful color images.” One of DePasquale’s favorite Hubble images shows the Lagoon nebula, a region of active star formation roughly 4,000 light-years away. “It’s a beautiful composition, and the colors are amazing,” he says.
Hubble images tend to stick in one’s brain. Senchyna remembers seeing pictures of comet Shoemaker-Levy 9 crashing into Jupiter in 1994 captured by Hubble. He was just a few years old, but those visuals stuck with him. “That was the sort of thing that got me hooked on astronomy,” he says. Hubble can inspire a sense of curiosity and wonder about the universe, he adds, and that’s a powerful thing. “That’s a huge part of why we need to be funding these flagship observatories.”
Here are some of the Hubble images from the last 35 years that have informed and inspired both scientists and the general public alike.
A cosmic mash-up
In 2010, astronomers discovered a puzzling asteroid, one with a cometlike tail of dust. Hubble data revealed that this object, called P/2010 A2, probably formed during the collision of two asteroids. It was the first time scientists had observed the aftermath of such a crash.
A light show on Jupiter
An aurora near Jupiter’s north pole glows brightly at ultraviolet wavelengths. Hubble has revealed that Jupiter’s strong magnetic field makes auroras on the giant planet particularly intense and long-lasting, unlike those on Earth.
A solar system collision
In July 1994, over 20 fragments of comet Shoemaker-Levy 9, which had been torn apart by tidal forces from Jupiter’s gravity, collided with the planet. Over the course of several days, Hubble revealed the evolution of this titanic collision (starting with the bottom image).
In the throes of death
A dying star in the Milky Way, nicknamed the Jewel Bug nebula for its resemblance to the vivid insect, sloughs off layers of gas and dust. Researchers think that the intricate shapes seen here may be due to the presence of a stellar companion merging with the dying star.
Cosmic sculptor
The Lagoon nebula is a stellar nursery located about 4,000 light-years from Earth. This image shows dust and gas being sculpted by a star roughly 30 times as massive as the sun. Different colors in the image represent four different wavelengths of light observed by Hubble’s Wide Field Camera 3.
A group of stellar youngsters
This agglomeration of stars, a globular cluster known as NGC 1850, is held together by the stars’ mutual gravity and resides in the Large Magellanic Cloud, a galaxy near the Milky Way. Unlike typical globular clusters, this grouping contains relatively young stars, creating a cache of stars born across two generations. Hubble observed NGC 1850 over a range of wavelengths of light, but UV observations were especially useful in detecting the youngest, hottest stars.
Turbulent times
Known officially as NGC 4826, this spiral galaxy is also dubbed the Black Eye galaxy due to the dark band of dust covering part of its center. Turbulent motions of gas within this galaxy are responsible for the birth of new stars, which appear blue in this image.
Filling in the blanks
In 1995, Hubble took this composite picture of what, to the naked eye, looks like a speck of empty space. Scientists were astounded to discover thousands of previously unseen galaxies in different stages of evolution.