Wooster Physicists

I awoke early this Christmas morning to watch the successful launch of the James Webb Space Telescope. I remember the genesis of the telescope a quarter of a century ago when it was called the Next Generation Space Telescope. (The telescope’s name is controversial, and I would have preferred an astronomer’s name.) Its development has been prolonged and difficult, as the graphs below attest, but like its predecessor, the Hubble Space Telescope, I am confident of its revolutionary importance — if the upcoming weeks of deployment and months of commissioning succeed.

Development of the unprecedented Webb telescope has been long and challenging

Hubble is a warm visible light telescope, with some near infrared and ultraviolet capability, in a low 540-kilometer Earth orbit. Webb will be a cold infrared telescope, with some red and orange capability, in a halo orbit about the second Earth-Sun Lagrange point 1.5 million kilometers anti-sunward from Earth.

(L_2 is an unstable equilibrium point: in an inertial reference frame, solar and terrestrial gravity combine to pull a mass into a solar orbit with a larger radius but the same period as Earth’s, so the mass appears to hover almost a million miles above Earth’s center; in a frame rotating with Earth about Sun, the combined gravitational force inward balances the centrifugal pseudo-force outward.)

Webb is optimized to study the early universe. Light from the first galaxies is both fainter due to distance and redder due to the expansion of the universe, so a larger, colder, more remote telescope is desirable. By contrast, Hubble is warm enough that its own infrared emission blinds it to this light.

During Webb’s long gestation, exoplanet science dramatically bloomed. Exoplanets are easier to detect in infrared light where the contrast between the glow of a star and its exoplanets is less. Consequently, the study of exoplanets and their atmosphere will be another Webb focus.

First though, Webb must survive six months of terror as it unfolds its giant sunshield and segmented mirror through hundreds of single points of failure.

Launched just last month, Lucy will be the first spacecraft to visit Jupiter’s trojan asteroids, rocky swarms that orbit about 60 degrees ahead and behind Jupiter in its orbit. Hal Levison, Lucy’s Principal Investigator, has described Lucy’s complicated trajectory, which includes an Earth gravity-assist and visits to both trojan swarms, as “part science, part art, and part luck”.

Named after the Lucy fossil that elucidates hominid history, Lucy will illuminate solar system history as the trojans are thought to be pristine remnants of planetary formation. The Lucy fossil itself was named after The Beatles‘ song “Lucy in the Sky with Diamonds” and, indeed, Lucy’s thermal emission spectrometer includes a large diamond beam splitter. During its 12-year primary mission, Lucy will visit seven trojans, including a near-twin binary pair, and one tiny main-belt asteroid named after Donald Johanson, the discover of the Lucy fossil.

Lucy’s trajectory involves an Earth (green) flyby and visits to the trojan asteroids leading and lagging Jupiter (brown) in its orbit. (NASA)