The Hubble Space Telescope
Launched in 1990 and serviced five times by Space Shuttle crews, Hubble has made more than 1.5 million observations — revealing the age of the universe, confirming the accelerating expansion driven by dark energy, and imaging everything from nearby planets to galaxies 13 billion light-years away.
A 10-day exposure of a tiny patch of sky revealed nearly 3,000 galaxies — proving that even the most apparently empty areas of space contain countless galaxies billions of light-years away.
Observations of distant supernovae by Hubble helped confirm in 1998 that the universe's expansion is accelerating — driven by a mysterious force now called dark energy. This finding earned the 2011 Nobel Prize in Physics.
Hubble was the first telescope to detect the atmosphere of an exoplanet and measure its composition, pioneering techniques now used by JWST to study potentially habitable worlds.
By measuring the distance to Cepheid variable stars, Hubble refined the Hubble constant and helped pin down the age of the universe to approximately 13.8 billion years.
Hubble was launched on April 24, 1990, aboard Space Shuttle Discovery. It has been in operation for over 34 years, making it one of the longest-running space observatories in history.
Hubble orbits Earth at approximately 27,300 km/h (17,000 mph). At this speed it completes one full orbit every 95 minutes and travels roughly 650,000 km per day — farther than the distance to the Moon and back.
Hubble can technically resolve objects on Earth, but it moves too fast and its tracking systems are optimised for distant stationary targets. Its primary purpose is observing deep-space objects, not Earth.
Hubble and the James Webb Space Telescope (JWST) are complementary, not competitors. Hubble observes ultraviolet and visible light; Webb primarily observes infrared. Together they cover a much wider range of the electromagnetic spectrum.
Hubble has been serviced five times by Space Shuttle crews: in 1993, 1997, 1999, 2002, and 2009. The 1993 mission corrected a flaw in the primary mirror. No further crewed servicing missions are planned.
Hubble's position is computed in real time using TLE orbital elements from CelesTrak and the SGP4 propagation model. Position updates every second. Also track the ISS, Starlink-1008, and Voyager 1 & 2.