Dark matter candidate particles are a no-show in Hitomi data

Before the demise of Japan’s latest X-ray satellite, Hitomi, the probe might have put to rest speculation about radiation from dark matter in a cache of galaxies.

In 2014 astronomers reported that several galaxy clusters appeared to inexplicably produce X-ray photons with energies of about 3.5 kiloelectron volts. The researchers suggested that the radiation could be coming from the decay of sterile neutrinos — hypothetical particles that are one candidate for the elusive dark matter that is thought to bind galaxies and clusters together.

Before the Hitomi X-ray satellite (aka ASTRO-H) failed on March 26, it got a look at the Perseus galaxy cluster, a horde of galaxies about 232 million light-years away. The telescope saw no sign of the previously reported X-ray photons, scientists report in a paper online July 25 at arXiv.org. A similar search of the dwarf galaxy Draco last year with the XMM-Newton satellite also failed to turn up the mystery X-rays. The no-show photons make it less likely that sterile neutrinos are the dark matter particles that scientists have been looking for.

Hitomi spun itself to death less than six weeks after it launched, when a problem with its control system caused the spacecraft to rotate out of control. The Japanese space agency is considering building Hitomi 2.0 for a possible launch in 2020.