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Since its launch in 1990, the Hubble Space Telescope has transformed humanity’s view of the universe. Orbiting Earth above the atmospheric distortions that hinder ground-based observations, Hubble has provided astronomers with clear, detailed images for over three decades. Despite being one of the most iconic scientific instruments ever built, several lesser-known aspects of its design, operation, and history might surprise even amateur astronomy enthusiasts or those who closely follow space exploration.
It Was Initially Sent Into Orbit With a Major Flaw
Hubble was launched aboard the Space Shuttle Discovery in April 1990, but the first images it returned were worryingly blurry. Engineers discovered that its primary mirror had been ground incorrectly by just 2.2 microns — about 1/50th the thickness of a human hair. This minor miscalculation, however, significantly impaired Hubble’s ability to focus light, creating indistinct and distorted images. A servicing mission in 1993 delivered a corrective optical system called COSTAR (Corrective Optics Space Telescope Axial Replacement), which successfully compensated for the flaw. This fix was often compared to placing glasses on the telescope, and it allowed Hubble to begin capturing the sharp, notable images for which it is now renowned.
Hubble Requires No Fuel to Stay in Orbit
Unlike spacecraft that travel through space under propulsion, Hubble is in a stable low Earth orbit approximately 340 miles above the surface. It doesn’t require fuel to remain in place, because it is continuously in free-fall around Earth — essentially perpetually falling but never hitting the ground due to its high tangential velocity. While minor propulsion has occasionally been needed to adjust its orientation or altitude, the observatory uses gyroscopes and reaction wheels to maintain its positioning. This means Hubble can operate for years without the need for continuous refueling.
Its Instruments See a Range of Light Invisible to the Human Eye
Though its most iconic photos are typically presented in visible light, Hubble observes in a broader electromagnetic spectrum that includes ultraviolet and near-infrared wavelengths. These capabilities allow scientists to study phenomena that would otherwise be unobservable from the ground or in visible light. For example, ultraviolet observations reveal the energetic processes in young stars, while infrared capabilities help peer through dense interstellar dust clouds to observe the formation of stars and galaxies. The telescope’s data is often translated into the images the public sees through a process known as false-color imaging, which assigns visual colors to different wavelengths that are not naturally visible to human eyes.
Hubble Has Been Serviced in Orbit Multiple Times by Astronauts
Unlike many satellites, Hubble was designed to be serviceable by astronauts. Between 1993 and 2009, five servicing missions were conducted by NASA astronauts via the Space Shuttle program. These missions replaced aging hardware, replaced gyroscopes, replaced batteries, and installed new scientific instruments, considerably extending Hubble’s operational life and scientific capabilities. Each mission involved complex spacewalks, sometimes lasting over seven hours, allowing NASA to not only address flaws but also enhance Hubble’s performance well beyond its original design expectations. This hands-on maintenance approach was unique and has helped keep the telescope relevant for decades longer than initially anticipated.
It Doesn’t Capture Color Photos As Experienced by the Eye
Hubble’s camera systems do not take photographs in color as a smartphone or consumer camera would. Instead, it captures monochrome images through different filters, each designed to isolate specific wavelengths. These individual black-and-white exposures are then assigned colors during processing to build a full-color image. This not only reconstructs a visually appealing representation but also highlights various features based on their chemical composition and temperature. The iconic “Pillars of Creation” image, for example, was pieced together using narrowband filters targeting hydrogen, sulfur, and oxygen emissions. The final coloration in Hubble photos is often intended to convey scientific information, not to offer a literal depiction.
Hubble Has Peered Back Billions of Years in Time
One of Hubble’s most astonishing abilities is its capacity to look deep into the cosmos and therefore far back into the past. Because light takes time to travel across the universe, when astronomers observe distant galaxies, they are essentially viewing them as they appeared billions of years ago. Hubble’s Deep Field missions — which involved pointing the telescope at seemingly empty patches of the sky for long durations — revealed thousands of previously unseen galaxies, some dating to within a few hundred million years of the Big Bang. These images have reshaped understanding of cosmic evolution and the formation of large-scale structures in the universe.
It Helped Pin Down the Age of the Universe
Determining the precise age of the universe was one of astronomy’s longstanding questions before Hubble’s launch. By observing Cepheid variable stars — a type of star whose brightness changes in a predictable pattern — Hubble allowed astronomers to refine measurements of cosmic distances. These observations were essential for calibrating the so-called cosmic distance ladder. When combined with measurements of the cosmic microwave background and Hubble’s own observations of the expansion rate of the universe (known as the Hubble constant), astrophysicists were able to arrive at an estimated age for the universe of approximately 13.8 billion years.
A Delay in Its Launch Gave Time for Technological Improvements
The original launch date for Hubble was scheduled for the mid-1980s. However, the tragic Space Shuttle Challenger disaster in 1986 led to delays across NASA’s entire shuttle program. While this was a setback, it unintentionally allowed additional time for engineers to test and improve some of the telescope’s optics and instruments. As a result of this additional development time, the final deployed telescope included several upgrades that might not have been present in the earlier version, had it launched on its original timeline. These enhanced systems contributed to the overall success and longevity of the telescope.
Its Replacement Will Not Revisit the Same Orbit
While the James Webb Space Telescope (JWST) is frequently referred to as Hubble’s successor, it differs significantly in design, purpose, and location. Rather than occupying a low Earth orbit, JWST will reside at a more distant location known as Lagrange Point 2, nearly a million miles from Earth. This position allows it to maintain a stable temperature and shield itself from infrared interference emitted by Earth. Hubble, by contrast, operates in visible and ultraviolet light, and its lower orbit made it accessible for service missions. JWST’s orbit means no such maintenance will be possible. NASA expects the two telescopes to complement each other rather than perform the same tasks.
Hubble’s Archive Will Continue to Provide New Discoveries
Even as newer telescopes come online, Hubble’s legacy will persist through a vastly rich archive of data. All of the images and spectral data recorded by the telescope are stored and made publicly available through scientific databases like the Mikulski Archive for Space Telescopes. Researchers around the world continue to draw from these repositories to study phenomena ranging from exoplanet atmospheres to gravitational lensing. In some cases, astronomers have used archived Hubble data to make discoveries years after the original observations were made. This extensive archive ensures that Hubble’s observational power will remain a contributing force in scientific discovery for years to come.
10 Best Selling Books About Astronomy Telescopes
Turn Left at Orion by Guy Consolmagno and Dan M. Davis
This practical observing guide helps amateur astronomers use astronomy telescopes to locate and view hundreds of deep-sky objects and Solar System targets from a backyard setup. It pairs sky navigation with object descriptions so readers can move from a basic star-hopping method to confident telescope observing sessions under real night-sky conditions.
NightWatch A Practical Guide to Viewing the Universe by Terence Dickinson
This widely used introduction explains how to choose a telescope, plan stargazing sessions, and read sky charts in a way that fits nontechnical adults who want results at the eyepiece. It emphasizes practical observing skills, including how to find constellations, planets, and brighter deep-sky objects with common beginner telescope types.
The Backyard Astronomer‘s Guide by Terence Dickinson and Alan Dyer
This handbook focuses on getting started in amateur astronomy with clear guidance on selecting astronomy telescopes, binoculars, and core accessories without assuming prior technical background. It connects equipment choices to real-world observing goals, helping readers plan what to observe, how to observe it, and how to build steady progress from casual stargazing to structured night-sky projects.
Star Ware The Amateur Astronomer’ohs Guide to Choosing Buying and Using Telescopes and Accessories by Philip S. Harrington
This equipment-centered guide explains how telescope design choices affect performance, from optical tubes and mounts to eyepieces and filters used in visual astronomy. It supports readers who want an informed buying process and a realistic setup plan for telescope observing, with attention to usability, portability, and matching gear to targets in the night sky.
Astronomy Hacks Tips and Tools for Observing the Night Sky by Robert Bruce Thompson and Barbara Fritchman Thompson
This hands-on book focuses on practical ways to improve telescope observing outcomes through low-friction upgrades, field techniques, and troubleshooting methods that reduce common beginner frustrations. It covers workflow topics such as finder alignment, observing comfort, recording observations, and entry-level astrophotography, all oriented toward better stargazing results.
The Dobsonian Telescope A Practical Manual for Building Large Aperture Telescopes by David Kriege and Richard Berry
This detailed manual explains how Dobsonian astronomy telescopes are designed and constructed, with an emphasis on practical building decisions that affect stability, motion, and optical alignment. It is frequently used by readers who want a large-aperture telescope for deep-sky observing and want a clear understanding of materials, fabrication steps, and performance tradeoffs.
How to Use an Astronomical Telescope A Beginner’s Guide to Observing the Cosmos by James Muirden
This beginner-focused guide explains how to set up a telescope, align common mounts, and locate targets efficiently without requiring advanced math or specialized jargon. It connects basic equipment operation to practical stargazing, guiding readers toward consistent results when observing the Moon, planets, and brighter deep-sky objects.
Telescope Optics A Comprehensive Manual for Amateur Astronomers by Harrie G. J. Rutten and Martin van Venrooij
This technical-but-readable reference explains how telescope optics work in practical terms, including image formation, aberrations, and how design choices influence visual astronomy and astrophotography outcomes. It helps readers interpret specifications and evaluate real performance, supporting better decisions when selecting or optimizing astronomy telescopes for specific observing goals.
Making Your Own Telescope by Allyn J. Thompson
This classic guide explains the fundamentals of building a telescope, including practical methods for creating and testing optical components and assembling a usable instrument for night-sky observing. It supports readers who want a hands-on pathway into amateur telescope making while still keeping the end goal centered on real stargazing with a functional astronomy telescope.
Inside the Star Factory The Creation of the James Webb Space Telescope NASA’s Largest and Most Powerful Space Observatory by Christopher Wanjek
This narrative history explains how a flagship space telescope was engineered, built, tested, and integrated, focusing on the technical and organizational realities behind modern astronomical instrumentation. It provides nontechnical readers a grounded view of how advanced telescopes extend astronomy beyond Earth’s atmosphere and why design constraints shape what the observatory can measure.
Today’s 10 Most Popular Science Fiction Books
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