Move over, James Webb: humanity is about to get another eye in the sky. There’s just been a new space telescope announced, named TOLIMAN, and it’s already got funding from the Breakthrough project.
The telescope is designed around two things: its target, and the exotic optics the telescope will use. TOLIMAN’s mission is to point directly at the Alpha Centauri system, in order to search for potentially habitable exoplanets there. The system actually contains three stars; Proxima Centauri (inside the red circle above) is confirmed to host a rocky planet in its Goldilocks zone, and there are likely several other planets elsewhere in the system.
Proposed design of the TOLIMAN space telescope. Credit: University of Sydney.
The name TOLIMAN stands for “Telescope for Orbit Locus Interferometric Monitoring of our Astronomical Neighbourhood.” Clunky, we know. But the acronym was chosen in homage to the space telescope’s target star system. Toliman is the official name of a star within the Alpha Centauri system: α Centauri B, the smaller and cooler of the binary pair around which Proxima Centauri orbits.
The 30-cm telescope is surprisingly small, for a space telescope, but its target is Earth’s nearest neighboring star system: Alpha Centauri. Alpha Cen is the brightest star in the constellation Centaurus, visible in the southern sky, and it’s about 4.3 light-years from Earth.
Image: Stellarium, via NASA
The system was first documented by Arabic astronomers during the Golden Age of Islam. The word “Toliman” itself is the Latinized version of an ancient Arabic name for Alpha Centauri, which meant “the Ostriches.” But two other stars in the Southern sky already bore that name, so to bring the name of the new star into accord with the constellation in which it was found, it was later renamed Rijl al-Qinṭūrus. This in turn was Latinized to Rijel Kentaurus, “the Centaur’s foot,” which is where TOLIMAN is going to point.
TOLIMAN’s exotic optics are its other keystone feature. The telescope will use a “diffraction pupil lens” for its observations. Multiple overlaid structural patterns are arranged on the surface of the lens, so that the different areas separate incident light by its phase.
Top: Black and white regions show three overlaid patterns on the diffraction pupil lens; black and white regions in each are in antiphase. They perform a kind of binning by phase. Bottom: The point-spread field associated with each. Right: “The patterns to the left illustrate 3 separate log-harmonic spirals, while to the right is the combined effect of the sum of all 3 log-harmonic spirals (upper) together with the corresponding PSF (lower).” Credit: study authors.
Because of this ability to distinguish separate sources, this design lends itself very well to studying Alpha Cen in particular. The system’s binary pair are only about 23 AU apart — about the distance from the Sun to Uranus. That means they have very little angular separation between them. Even so, the two stars can be clearly distinguished by the diffraction pupil design, because where they might overlap visually, using this lens means that different light sources stand out from one another in an obvious, kaleidoscopic way:
Different light sources really do stand out quite sharply from one another. Image: Fig. 3, TOLIMAN project abstract; Tuthill et al., 2018.
The international collaboration is led by Peter Tuthill of the Sydney Institute for Astronomy, and it includes teams from the University of Sydney, Breakthrough Initiatives, Saber Astronautics, and NASA’s JPL. Jason Held, CEO of Saber Astronautics, described TOLIMAN in a press release as “an exciting, bleeding-edge space telescope,” one that will be “supplied by an exceptional international collaboration. It will be a joy to fly this bird.”