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On April 24, 1990, Space Shuttle Discovery lifted off from Kennedy Space Center carrying one of the most ambitious scientific instruments ever built: the Hubble Space Telescope. The following day, Hubble was deployed into orbit approximately 340 miles above Earth. Notably, Hubble was designed to do something revolutionary: observe the universe without the blurring interference of Earth's atmosphere. Since then, over the next three and a half decades, we’ve learned exponentially more about the cosmos.
Why put a telescope in space?
Although Earth’s atmosphere is necessary for sustaining life, it is also frustrating for advancing our understanding of astronomy. That’s because the air molecules in our atmosphere scatter and absorb light (which causes the twinkling effect that makes stars look beautiful), but also blurs their images and blocks entire ranges of the electromagnetic spectrum. Therefore, ground-based telescopes, no matter how large or sophisticated, are always looking through this distorting veil.
A telescope in orbit above the atmosphere has none of these limitations. It can observe with extraordinary sharpness across a much wider range of wavelengths. The idea of a space telescope was first proposed by astronomer Lyman Spitzer in 1946, and NASA began developing Hubble in the 1970s. By the time it launched in 1990, it had taken decades of engineering, international collaboration, and billions of dollars to build.
Hubble’s origins
Shortly after deployment, scientists discovered that Hubble's primary mirror was the wrong shape — it was off by 2.2 micrometers (which is about one-fiftieth the width of a human hair). Even though the mismatch was small, the product was seriously altered. The error produced blurry images that were deeply disappointing and publicly embarrassing for NASA.
To amend this issue, in 1993, a space Shuttle servicing mission installed corrective optics, which are a set of precisely shaped mirrors that compensated for the flaw. In a sense, they function like contact lenses for the telescope. Thankfully, the fix worked perfectly. Hubble returned crystal-clear images and went on to become one of the most productive scientific instruments in history.
What Hubble has taught us
Hubble has produced a list of extraordinary scientific contributions. For one, it provided the measurements that allowed astronomers to pin down the age of the universe at approximately 13.8 billion years. Even more, it also played a central role in the discovery of dark energy: the mysterious force accelerating the expansion of the universe. This finding was so incredible that it earned the 2011 Nobel Prize in Physics! Hubble imaged the deep field (a tiny patch of sky containing thousands of galaxies), demonstrating that the observable universe contains hundreds of billions of them. It also studied the atmospheres of exoplanets, observed the collision of a comet with Jupiter, and captured the birth and death of stars in breathtaking detail.
While the mission was originally designed to last 15 years, it is still operating after 35. Since its deployment, Hubble has made more than 1.5 million observations and contributed to thousands of peer-reviewed papers through its comprehensive data. The Hubble Space Telescope is one of the greatest scientific achievements in history, and continues to transform how we see ourselves in relation to the universe.
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