Hubble Space Telescope
The Hubble Space Telescope was the first of NASA's Great Observatories launched in April, 1990. Above Earth's atmosphere, Hubble captures light rays from space and directs them to its instruments for observation. Hubble is a Cassegrain reflector telescope, which means that incident light first hits a primary mirror, reflects off, and is focused by a secondary mirror into the scientific instruments (as seen in the image below). Hubble has a low-Earth orbit at 569km above Earth, taking only 97 minutes to complete one full orbit.
Hubble's Six Instruments (click instruments below to expand)
1. NICMOS (Near-Infrared Camera & Multi-object Spectrometer
NICMOS is a near infrared camera or "heat sensor". It allows Hubble to observe objects hidden by interstellar dust (such as star birth sites) and view farther into space than ever before.
The image below shows planetary nebula NGC 7027. As it burns out, NICMOS is able to view past the dust to image the star at its centre.
2. ACS (Advance Camera for Surveys)
ACS detects visible light, and is so sensitivite that it can detect the most distant objects.
3. WFC3 (Wide Field Camera 3)
WFC3 is one of Hubble's newest cameras. It detects near-ultraviolet, visible, and infrared light, giving Hubble panchromatic coverage. It is used to study dark matter, dark energy, formation of stars, and is able to detect remote galaxies.
WFC3 gives Hubble its ability to take images of the universe that are very far away, generating the famous ultra deep-field images.
4. COS (Cosmic Origins Spectrograph)
COS is a spectrograph that detects ultraviolet light emitted by extrasolar objects. Like a prism, the spectrograph separates light into its component frequencies, allowing Hubble to tell us about the object's temperature, chemical composition, density, and motion.
The image below is an example of date from COS showing that oxygen and carbon are present in the remnant of Supernova N132D.
5. STIS (Space Telescope Imaging Spectrograph)
STIS is a spectrograph that detects ultraviolet, visible, and near-infrared light. It is used to map galaxies and hunt black holes.
The image below shows STIS's view of Saturn's auroral curtains that are present at both poles.
6. FGS (Fine Guiding Sensors)
FGS are sensors used to point and lock Hubble at 'guide stars'. It allows distances between stars to be precisely measured, as well as their relative motions.
Hubble's hunt for Exoplanets
Hubble uses four planetary detection methods: The Transit Method, Direct Imaging Method, Astrometry, and Gravitasional Microlensing. Though Hubble was not designed to explicitly hunt for exoplanets, it has significantly contributed to the field. It was the first telescope to capture a visible-light image of a planet orbiting a star outside of our Solar System.
Hubble's exploration of Exoplanet atmospheres
Hubble's spectrometer (NICMOS) allows it to detect water, carbon, oxygen, carbon dioxide, methane, and other molecules that may be present in a planet's atmosphere. This allows us to detect if distant planets from Earth are capable of supporting or already support life. Hubble was the first telescope to detect an organic molecule (methane) on a planet outside of our Solar System.