NASA has announced some more details on the James Webb telescope, slated to replace Hubble as the most important such instrument in orbit. Hubble is located in an elliptical low Earth orbit, with an orbital height of 589km and an orbital velocity of 7,500 m/s. The Webb will be located at Lagrange Point 2. This is an area where gravity will keep the telescope in a sun-earth line. As a result, the telescope will always be in the shadow of the Earth. NASA has a report on the transition.
Hubble has been one of NASAs great successes over the last 17 years, both in terms of the quality scientific information generated and in terms of the way the project reflects upon the organization. By finally offering an astronomical vantage point not affected by the Earth’s atmosphere, Hubble has been able to make unprecedented observations and discoveries. For example, consider the various exoplanets discovered in recent years, either because of how they obscure stars by passing in front of them or cause stars to wobble with their gravitational pull. Hubble was also ideally placed to observe the impact of Comet Shoemaker-Levy 9 into Jupiter. I remember watching the video feed from that at the Vancouver Planetarium, back in 1994. Some pretty stunning images of the universe have also been generated.
Just yesterday, Hubble may have observed a ring of dark matter. Given the disjoint between how galaxies behave gravitationally and the number and mass of stars we can observe, scientists have speculated that most of the material composition of the universe consists of dark matter and dark energy. The former has gravitational effects but does not interact with electromagnetic radiation. The latter is hypothetically involved in universal expansion: serving as one possible explanation for why the universe is expanding at an expanding rate, as observed through the Doppler shift. Data from the remainder of Hubble’s operational life and the full span of the Webb telescope’s operation may help with the refinement or rejection of both of these ideas, with coincidental improvement in our understanding about the contents and evolution of the universe.