The Hubble Space Telescope: what it is and whether you can see it
Hubble has orbited Earth since 1990, above the blurring atmosphere. How it works, how astronauts repaired it, what it discovered, and whether it can be seen from Korea.
A telescope above the air
The atmosphere blurs and dims starlight and blocks ultraviolet light completely. Hubble, launched by the Space Shuttle Discovery in April 1990, avoids all that from about 500 km up. Its 2.4 m mirror is small by today's ground standards, but its images are sharp and steady.
Repaired in orbit
Soon after launch, its mirror turned out to be ground to slightly the wrong shape. In 1993 astronauts installed corrective optics, and four later Space Shuttle servicing missions, the last in 2009, replaced cameras, gyroscopes and batteries. No other telescope has been upgraded like this in space.
What it showed us
Hubble helped pin down the age of the universe at about 13.8 billion years, took the Deep Field images showing thousands of galaxies in a tiny patch of sky, and contributed to the discovery that the expansion of the universe is speeding up. It now works alongside the James Webb Space Telescope, which observes mainly in infrared.
Can you see it?
Hubble's orbit is tilted only 28.5° to the equator, so from Korea it never rises high: it stays low in the southern sky, where buildings and haze often hide it. From southern Korea on a clear evening it can be seen as a moderately bright, steady point moving west to east.