The Italian National Institute of Astrophysics (INAF) has unveiled the ASTRI project, the first prototype for a new low-cost, ground-based telescope that will look at gamma-ray emissions from the sky.
The observatory, which is located on the slopes of Mount Etna, was able to pass its most difficult test yet on October 16. The telescope was able to keep its angular resolution constant over a wide field of view. This is a crucial necessity for gamma-ray telescopes.
Gamma-rays don’t penetrate our atmosphere but interact with the gas molecules present, generating a cascade of subatomic particles that move faster than light in air (but still slower than light in a vacuum). Moving so fast, they emit what is known as Cherenkov light, which is what this telescope is designed to look for.
"The telescope was built and completed for the first time ever adopting the Schwarzschild-Couder configuration," said Giovanni Pareschi, astronomer at the INAF-Brera Astronomical Observatory and principal investigator of the ASTRI project, in a statement. "This kind of telescope has never been realized until now, mainly due to technological difficulties."
This telescope model was first proposed by Karl Schwarzschild in 1905 and the design was then enhanced by André Couder in 1926. Its two mirrors were designed to eliminate most of the optical aberration in the field of view, but it was too difficult and expensive to actually build.
“However, recent advances in technology (in particular for the realization of the primary and secondary mirrors) have made the implementation of this design practicable (thanks also to the study by Prof. Vladimir Vassiliev at UCLA) for the observation of Cherenkov light emitted by the atmospheric showers generated by cosmic gamma rays,” added Pareschi.
ASTRI is the precursor for the Cherenkov Telescope Array (CTA), the next generation of gamma-ray observatories that will have more than 100 telescopes across two sites in both hemispheres. ASTRI is one of the Small Size Telescopes, and the CTA expect to have 70 of these telescopes between both sites.
The telescope is expected to observe the first Cherenkov light next month.