25-04-2025
Happy 35th, Hubble: 10 of the Telescope's Coolest Achievements
On April 24, 1990, NASA's Space Shuttle Discovery carried the Hubble Space Telescope into low Earth orbit. Since then, the telescope—a collaboration between NASA and the European Space Agency—has racked up so many groundbreaking scientific achievements and stunning space images that it's hard to remember them all. In honor of Hubble's 35th birthday, we're looking back on some of its most exciting milestones.
Hubble had been in space for less than two years when its Goddard High Resolution Spectrograph detected traces of boron in a not-too-distant star. At an estimated age of 14.5 billion years, the star was (and still is) believed to have been one of the oldest stars ever identified, meaning Hubble had already gathered clues about the chemistry of the early universe. (Note: NASA's write-up from 1992 contains some minor miscalculations regarding the age and distance of the star, called HD 140283; these figures were thought to have been true at the time, but have since been corrected.)
Black holes might seem mysterious today, but they were even more elusive just a few decades ago, when scientists weren't sure whether gravitationally collapsed objects actually sat at the heart of active galaxies. In 1994, Hubble's Wide Field Planetary Camera-2 captured an image of an object at the center of M87, a giant elliptical galaxy 50 million light-years away. Though the object was as heavy as 3 billion Suns, it was squeezed into a space no larger than our solar system, supporting Albert Einstein's then 80-year-old general theory of relativity.
Hubble's image of the black hole at the center of M87. Credit: Holland Ford, Space Telescope Science Institute/Johns Hopkins University; Richard Harms, Applied Research Corp.; Zlatan Tsvetanov, Arthur Davidsen, and Gerard Kriss at Johns Hopkins; Ralph Bohlin and George Hartig at Space Telescope Science Institute; Linda Dressel and Ajay K. Kochhar at Applied Research Corp. in Landover, Md.; and Bruce Margon from the University of Washington in Seattle.; NASA
In 2008, Hubble took a big step toward someday identifying signs of life on an exoplanet. The telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) had wrapped up extensive observations of HD189733b, a Jupiter-sized planet 63 light-years away in the constellation Vulpecula. Those observations revealed definitive proof of methane and water vapor in the exoplanet's atmosphere. Though HD189733b is considered far too hot to contain life—its atmosphere is an estimated 1,700 degrees Fahrenheit—the discovery of organic molecules in its atmosphere demonstrated the telescope's ability to find signs of potential habitability on planets outside our solar system.
For more than a decade, this picture has been the one to pop into the public's mind when we think of Jupiter. Hubble snapped it in 2014, when NASA wanted an update on the Great Red Spot's gradual shrinkage. The storm feature had indeed become smaller than ever, measuring just 10,250 miles across, compared with the 14,500-mile diameter captured by Voyager 1 and Voyager 2 just 35 years prior.
Credit: NASA, ESA, and A. Simon (Goddard Space Flight Center),
Though Voyager 1 and Voyager 2 first identified the subsurface ocean on Jupiter's Europa, Hubble called dibs on the moon's cryovolcanoes. In 2016, NASA announced that Hubble had imaged plumes of water erupting from Europa's surface. Because Europa's ocean would be difficult to sample directly, these plumes offered the tantalizing possibility of analyzing the moon's water without touching down on the surface. Sure enough, Europa Clipper, which NASA finally launched in October 2024, will spy on the cryovolcanoes as it zips around the icy body.
Not one to waste time, Hubble quickly made another moon-related discovery by helping the Kepler Space Telescope find the first-ever signs of an exoplanet moon. While Kepler had the first inkling that a so-called "exomoon" might be present around Kepler 1625b, a super-Jupiter roughly 8,200 light-years away, Hubble's closer examination found additional signs of the exomoon's existence. Kepler 1625b i still hasn't been confirmed, but if it does exist, it's likely the size of Neptune.
Artist's illustration of Kepler 1625b i orbiting Kepler 1625b. Credit: NASA, ESA, and L. Hustak (STScI)
After decades of wondering whether black holes could go solo, scientists finally found direct evidence of one that had. Combined with ground telescope observations, Hubble's observations of a black hole 5,150 light-years away revealed that the object had no stellar companion with which to interact. Because interactions with starlight make black holes easier to identify, "rogue" black holes had long gone undetected, but this one offered proof that isolated stellar-mass black holes did exist.
Between 2009 and 2020, Hubble captured a series of images of the Butterfly Nebula, whose clouds of dust and gas form near-symmetrical "wings." By investigating how those observations morphed over time, researchers at the University of Washington found that the Butterfly Nebula's central white dwarf was releasing multiple jets of ultra-hot stellar material, gradually sculpting the nebula's edges. Though Hubble's observations didn't solve the mystery of how the nebula's characteristic shape formed in the first place, they offered an intimate look at how a nebula's clouds can evolve over a relatively short period of time.
A Hubble image of the Butterfly Nebula from 2020, just three years before the telescope's investigation of its central white dwarf. Credit: NASA, ESA, Joel Kastner (RIT)
The Andromeda Galaxy is the closest major galaxy to our own Milky Way, making it an obvious point of interest for astronomers. In January, scientists released a whopping 2.5-gigapixel image of the spiral galaxy—the product of a decade-long project aimed at depicting Andromeda in unprecedented detail. This incredible feat will undoubtedly aid in research related to the galaxy for years to come.
It's a magical thing to view the birthplace of thousands of stars, and Hubble's image of NGC 346 doesn't disappoint. Earlier this month, the ESA published a captivating depiction of the Small Magellanic Cloud's stellar nursery, where at least 2,500 newborn stars shone brightly between threads of gas and dust. NASA likened the baby stars to cosmic sculptors, "carving out a bubble" within their nebula.
A colorized Hubble snapshot of NGC 346. Credit: ESA/Hubble & NASA, A. Nota, P. Massey, E. Sabbi, C. Murray, M. Zamani (ESA/Hubble)
