Hitomi’s X-Ray Eye is Now Watching the Cosmos
published during a full moon.

The Universe is a dark, dusty place. But thanks to Hitomi’s X-ray sensors, we can now peer through veils of cosmic gas and dust that optical telescopes cannot. 



ASTRO-H launched successfully on Wednesday, Feb. 17, 2016, at 3:45 a.m. EST. The satellite subsequently deployed its solar arrays and is currently functioning normally. ASTRO-H will provide astronomers with a new view of the high-energy universe and has been renamed Hitomi, which translates to “pupil of the eye.” Credit: NASA

On Wednesday, February 17th, an H-IIA rocket lit up the night as it carried Japan’s sixth satellite into space. The newest X-ray astronomy satellite (preliminarily dubbed ASTRO-H) — a joint collaboration between The Japan Aerospace Exploration Agency (JAXA), The National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Canadian Space Agency (CSA) — was officially named “Hitomi.” Generally speaking, hitomi is the word for eye but more specifically the pupil, which is the entrance to the eye — just like the aperture.

Inspiration for the name comes from an ancient Japanese legend. According to the JAXA website, the legend goes like this: “One day, many years ago, a painter was drawing four white dragons on a street. He finished drawing the dragons, but without “Hitomi”. People who looked at the painting said “why don’t you paint Hitomi, it is not complete! The painter hesitated, but people pressured him. The painter then drew Hitomi on two of the four dragons. Immediately, these dragons came to life and flew up into the sky. The two dragons without Hitomi remained still.”

Hitomi is the largest space observatory ever launched by Japan. Designed to study the hot, energetic portions of the Universe, Hitomi will search for black holes and other ‘high energy’ bodies, including supernovas, by detecting the radiation they spew out into the cosmos in the form of X-rays. Hitomi does this by observing and analyzing an object’s spectra. Spectra are loaded with information, and by deciphering an object’s spectra, scientists can learn a great deal about that object. For example, spectra from galaxy clusters can provide the velocity and turbulence of the plasma throughout the cluster, which tells scientists how the cluster formed. When combined with optical data, X-ray information has provided scientists with indirect evidence of dark matter. Scientists are hopeful that Hitomi will determine what causes the puzzling X-ray signals seen in certain galaxies. Could it be dark matter decaying into photons or could it be something else entirely?

“We see X-rays from sources throughout the universe, wherever the particles in matter reach sufficiently high energies,” said Robert Petre, chief of Goddard’s X-ray Astrophysics Laboratory and the U.S. project scientist for Astro-H. “These energies arise in a variety of settings, including stellar explosions, extreme magnetic fields, or strong gravity, and X-rays let us probe aspects of these phenomena that are inaccessible by instruments observing at other wavelengths.”

This new “eye on the cosmos” will scan for X-rays using a suite of four instruments including a cutting edge X-ray micro-calorimeter, which observes a wide range of X-rays from space with the world’s top-level spectral capability. Another very special instrument onboard is the Soft X-ray Spectrometer (or SXS). This ultra-sensitive instrument works with the help of special refrigeration unit that cool the detector to just above absolute zero. As X-rays are absorbed by the detector, they will increase the temperature. Scientists will use that temperature rise to measure the energy of the X-ray. The SXS is expected to generate the most accurate X-ray measurements of any instrument to date. First developed in 1984, the SXS instrument has experienced setbacks. Its first ride to orbit failed shortly after launch in 2000, and its second attempt was on board the Suzaku spacecraft in 2005. The instrument made it to orbit then, but failed after only 17 days as a helium leak in the cooling system prevented the sensor from staying super-chilled.

“Our team has been working on this experiment for 30 years,” Andrew Szymkowiak, a senior researcher at Yale University said. “While we’ve really enjoyed working with our Japanese colleagues, during the many weeks of instrument integration, testing, and launch rehearsals, it is going to be so rewarding to finally get to reap the scientific rewards.”


This illustration shows the locations and energy ranges of ASTRO-H science instruments and their associated telescopes. One keV equals 1,000 electron volts, which is hundreds of times the energy of visible light. Credits: JAXA/NASA’s Goddard Space Flight Center

Currently, the other major X-ray observing satellites are NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, which both launched in 1999. According to project scientists Chandra will take better pictures than Hitomi, but Hitomi can more precisely measure the composition and motion of matter around objects such as black holes. Furthermore, according to NASA, Hitomi has the capability to observe X-ray sources 10 times fainter than those observed by Suzaku, allowing scientists to peer through veils of gas and dust that optical telescopes cannot.

To read more about the outer space mysteries Japan’s Hitmoi can help uncover, read this article by NOW.SPACE writer, Kasiz Galazka.

Watch the launch here: