Hubble marks 200,000th orbit as it hunts a reappearing supernova

NASA’s Hubble Space Telescope completed its 200,000th orbit of Earth on 19 September, NASA announced on Wednesday.

Hubble has travelled more than 5 billion miles around Earth during its 36 years in space and has now exceeded 1.7 million total observations, according to the NASA Hubble Mission Team at the Goddard Space Flight Center.

An observation completed on the day of the 200,000th orbit concerns one of Hubble’s defining scientific legacies: measuring the expansion rate of the universe, known as the Hubble Constant. Hubble is revisiting the same regions of the sky to monitor for the reappearance of a supernova — an exploding star — named Athena.

The massive galaxy cluster MACS J0417 acts as a gravitational lens, bending and magnifying light from objects far behind it. Light from a supernova can reach Earth along multiple paths, causing the same stellar explosion to appear more than once — months or even years apart depending on the path it took.

Supernova Athena was discovered by NASA’s James Webb Space Telescope in 2025 and is predicted to reappear between now and early March 2027. NASA says measuring the timing of Athena’s reappearances could help researchers map the mass of MACS J0417 and refine understanding of the expansion rate of the universe.

After more than 36 years in orbit, Hubble remains highly productive: its ultraviolet and visible-light observations complement the James Webb and Roman space telescopes, and astronomers request about seven times as much Hubble observing time as is available each year.

Sources

• NASA (Hubble Mission Team, Goddard Space Flight Center): “NASA’s Hubble Seeks Lensed Supernova, Marks 200,000 Orbits” — https://science.nasa.gov/missions/hubble/nasas-hubble-seeks-lensed-supernova-marks-200000-orbits/