The primary mirror of the JWST, the Optical Telescope Element, is composed of 18 hexagonal mirror segments made of gold-plated beryllium which combine to create a 6. 5-meter (21 ft; 260 in) diameter mirror that is much larger than the Hubble’s 2. 4-meter (7. 9 ft; 94 in) mirror. Unlike the Hubble, which observes in the near ultraviolet, visible, and near infrared (0. 1 to 1 μm) spectra, the JWST will observe in a lower frequency range, from long-wavelength visible light through mid-infrared (0. 6 to 27 μm), which will allow it to observe high redshift objects that are too old and too distant for the Hubble to observe. The telescope must be kept very cold in order to observe in the infrared without interference, so it will be deployed in space near the Earth–Sun L2 Lagrangian point, and a large sunshield made of silicon- and aluminum-coated Kapton will keep its mirror and instruments below 50 K (−220 °C; −370 °F).
A Moon Made Of Lightweight Fluff! Methone is small and oval--and unlike other tiny objects, composed of rock and ice, that scurry around our Solar System. Methone, which was observed up close for the very first time in 2012, is not pockmarked by impacts like other worldlets of its kind. Instead, this strange little moon, is very smooth--it shows not a hill nor an impact crater anywhere on its weirdly smooth surface. This shiny, white, icy egg in Space, residing in a peaceful nest of ice crystals, is an enigma wrapped in a bewildering mystery that some astronomers may have solved. The answer to the bewitching riddle of Methone? It is composed of lightweight fluff! Dr. Soderblom and his team, including Dr. Maria Zuber, who is the E.A. Griswold Professor of Geophysics and MIT's vice president of research, have published their findings in the September 10, 2015 issue of the journal Geophysical Research Letters. Life as we know it depends on the presence of three ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, mainly carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. With this new discovery of the existence of hydrogen, in the tattle-tale plume shooting out from the surface of Enceladus, Cassini has revealed to the prying eyes of curious astronomers, that this small, icy moon has almost all of these ingredients important for habitability. At this point, Cassini has not detected the presence of phosphorus and sulfur in the hidden subsurface ocean of this distant small world, but many planetary scientists suspect that they will eventually be detected because the rocky core of Enceladus is believed to be similar to certain meteorities that contain these two critical elements.