You may have seen some out-of-this-world photographs of galaxies far, far away, taken by the Hubble Space Telescope (HST), which was launched into space from the Space Shuttle Discovery back in 1990. But before the public ever sees those breathtaking images of nebulae and supernovae, the digital images consisting of only grayscale pixels are enhanced with color, created through multiple exposure overlays that combine images using various filters, typically red, blue and green. Those filters capture only specific wavelengths of light, which are then used to make a full-color composite image.
We can see clearly now:
- The deep-space telescope was named after astronomer Edwin Hubble, who determined in 1924 that Andromeda was a galaxy millions of light years away from Earth, and not a nebula.
- The HST’s first images came back to Earth blurry, caused by a tiny “spherical aberration” in its main focusing mirror. In 1993, space-walking astronauts added an instrument to correct its fuzzy vision.
- The HST’s successor, called the James Webb Space Telescope, will be launched in 2021. The $10 billion USD satellite will be placed well beyond the Moon, more than 1 million miles (1.6 million km) from Earth.