This past Sunday marked the 10th anniversary of NASA's Spitzer Space Telescope. Named for astronomer Lyman Spitzer, it is an infrared telescope, which allows us to observe objects invisible from the Earth. Not only can our eyes not see at infrared wavelengths, most infrared light is absorbed by the Earth's atmosphere, making it essential for most infrared observations to be taken from space.
Infrared telescopes are ideal for studying cool (temperature-wise) objects such as brown dwarfs and planets. In fact, Spitzer was the first telescope to observe light emitted by a planet outside our solar system; in 2005, it detected infrared light from a "hot Jupiter", a Jupiter-like planet very close to its star. Spitzer also enabled discoveries related to objects in our own solar system. In 2009, it discovered the largest ring of Saturn. The diffuse ring contains dust that emits infrared radiation, enabling Spitzer to detect its presence.
Spitzer has also given us incredible glimpses into regions where new stars are being formed. Visible light is absorbed by the large amounts of gas and dust in these stellar nurseries, but infrared observations allow us to see past that to view stars in their infancies. Astronomers have also used Spitzer to look through the dust in the center of our galaxy to confirm the presence of a large stellar bar in the Milky Way's nucleus. At the centers of some spiral galaxies, the stars form a bar-like structure. The Milky Way's bar, confirmed through observations of 30 million stars, may help funnel matter towards the supermassive black hole living in its center.
In 2009, Spitzer ran out of the coolant used to chill some of its instrumentation, and it has been running in "warm mode" since then. Despite this, Spitzer continues to make impressive discoveries, and give us a unique window into previously unexplored parts of our universe.