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The telescope’s journey has been anything but smooth. From an initial spherical aberration in its primary mirror that threatened the entire mission to five high-risk servicing missions by space shuttle crews between 1993 and 2009, Hubble’s story is one of human ingenuity overcoming seemingly insurmountable challenges.<\/p>\n
These heroic interventions by astronauts, including European Space Agency team members on two of the missions, have enabled Hubble to make nearly 1.7 million observations of approximately 55,000 astronomical targets. The resulting scientific discoveries have generated over 22,000 research papers with more than 1.3 million citations as of February 2025.<\/p>\n
Before Hubble’s launch in 1990, our view of the cosmos was severely limited by Earth’s atmosphere. Ground-based telescopes could see only halfway across the universe, and estimates for the age of the cosmos varied widely. Supermassive black holes remained theoretical entities, and no planets had been confirmed beyond our solar system.<\/p>\n
Among the telescope’s most significant contributions are precise measurements of the universe’s expansion rate, confirmation that supermassive black holes exist at the centers of most galaxies, the first analysis of exoplanet atmospheres, and critical observations leading to the discovery of dark energy \u2013 the mysterious force accelerating cosmic expansion.<\/p>\n The anniversary image collection showcases Hubble’s versatility. New observations of Mars reveal water-ice clouds giving the Red Planet a frosty appearance as its northern polar cap experiences the beginning of Martian spring. The planet was approximately 98 million kilometers from Earth when these images were captured in late December 2024.<\/p>\n Another highlight is a small portion of the massive Rosette Nebula, a star-forming region spanning 100 light-years located 5,200 light-years from Earth. Hubble’s image focuses on just a 4-light-year section, roughly the distance between our Sun and Alpha Centauri, revealing dark hydrogen clouds being sculpted by radiation from nearby massive stars.<\/p>\n The barred spiral galaxy NGC 5335 rounds out the collection, showcasing patchy star formation across its disk rather than the well-defined spiral arms common in many galaxies. Its central bar structure, which “channels gas inwards toward the galactic center, fueling star formation,” appears in approximately 30 percent of observed galaxies, including our own Milky Way.<\/p>\n European astronomers have made particularly effective use of Hubble, consistently securing more than the 15% of observing time guaranteed through ESA’s participation in the mission. Their discoveries include evidence for intermediate-mass black holes, extraordinarily bright explosions far from any host galaxy, and most notably, the identification of Earendel in 2022 \u2013 the most distant single star ever observed, seen as it existed 12.9 billion years ago when the universe was less than a billion years old.<\/p>\n Beyond deep space, Hubble continues to reveal secrets within our solar system. The OPAL program recently celebrated a decade studying the outer planets, discovering water vapor on Jupiter’s moons Europa and Ganymede, mysterious “spokes” in Saturn’s rings, and monitoring changes in the size of Jupiter’s Great Red Spot.<\/p>\n Perhaps most remarkably, Hubble has transitioned from pioneer to partner, now working in tandem with the James Webb Space Telescope to provide complementary observations across different wavelengths. Webb itself might never have been built without Hubble first revealing what its designers call an “undiscovered country” of countless distant galaxies.<\/p>\n “Unlike any other telescope before it, Hubble has made astronomy very relevant, engaging, and accessible for people of all ages,” notes the anniversary statement. “Hubble became ‘the people’s telescope,’ touching the minds as well as the emotions of hundreds of millions of humans around the globe.”<\/p>\n As Hubble enters its 36th year of operation, it shows no signs of slowing down. With its immense archive of more than 400 terabytes of data and continued production of groundbreaking science, the telescope that fundamentally changed humanity’s perception of the cosmos remains an indispensable tool in astronomers’ quest to understand the universe.<\/p>\n","protected":false},"excerpt":{"rendered":"![\"This](\"https:\/\/scienceblog.com\/esa\/wp-content\/uploads\/sites\/13\/2025\/04\/Planetary_nebula_NGC_2899_pillars.jpg\")
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