This Is the Most Detailed Map of Black Holes Ever Created

With 3 million newfound objects, and counting.
Brad Bergan

Imagine a map of every black hole in the universe.

A German-made space telescope is bringing us closer to this than ever before, generating the most intricate map of black holes and neutron stars throughout the cosmos by unveiling more than 3 million newly-discovered objects in less than two years, according to an initial report from

When the initial data batch dropped earlier this year, cosmology and astronomy enthusiasts basked in the glory of a universe invisible to optical telescopes (or the naked eye, for that matter). But since then, the scope of a universal map is making waves in the scientific community.

Germany's X-ray telescope could reveal the distribution of dark energy

The space observatory, dubbed eROSITA when it launched in 2019, is the first X-ray telescope based in space that can observe, image, and study the entire sky. Equipped as the main payload on the Russian-German Spectrum-Roentgen-Gamma mission, it orbits parallel to the Earth in Lagrange point 2, one of the five gravitationally-neutral positions throughout the sun-Earth system, where the forces of gravity from the sun and Earth achieve a neutral balance. Since it's distant from both, this position also serves as a prime locale from which to glimpse the entire cosmos. And it does so with an unconscionably strong X-ray detector.

In June, the eROSITA team of scientists at the Max Planck Institute for Extraterrestrial Physics in Germany made public a great abundance of data gathered by the space-based instrument, fueling future studies in the scientific community. As of writing, the space telescope has already made substantial contributions, including the reveal of a batch of gigantic X-ray bubbles zapping their way out from the center of our galaxy. And the latest release puts eROSITA forward as a means to answer very old questions about the cosmos. Namely, the elusive distribution of the mysterious dark energy throughout the universe, according to statements made by Andrea Merloni, senior scientist of the endeavor, in the report.

Most Popular
eROSITA X-ray all-sky survey
Every bright light is a neutron star or black hole. Source: Jeremy Sanders, Hermann Brunner and the eSASS team (MPE) / Eugene Churazov, Marat Gilfanov (IKI)

Peering into the invisible universe

"For the first time, we have an X-ray telescope that can be used in very similar ways as the large field optical telescopes that we use today," said Merloni in the report. "With eROSITA, we cover the entire sky very efficiently and can study large-scale structures, such as the entire Milky Way." Surveys of the entire sky like Gaia from the European Space Agency, or the European Southern Observatory's Very Large Telescope (based on the surface) can image colossal groups of stars and other astronomical objects. Gaia images nearly two billion stars within our galaxy, and evaluates their positions and distances from Earth, to unspeakable accuracies. "Large survey telescopes are now quite commonplace because they are very useful to study cosmology [of the cosmos' evolution] and things such as dark energy," explained Merloni in the report.

"But optical telescopes are much easier to design than X-ray telescopes," added Merloni. This is a bit of a downer, since a number of the most significant objects in the cosmos are invisible to optical telescopes because they emit no visible wavelengths. In other words, neutron stars and black holes aren't very observable with optical telescopes, and neither are distant clusters of galaxies, which form the filaments of the totality of the known universe and are far easier to study via X-rays. "The X-ray telescopes so far have been able to look very deep into the center to observe the early universe," said Merloni in the report. "But it has always been very difficult to compile large populations [of neutron stars, black holes, and distant galaxy clusters] and create a large catalog that you could then use to study their cosmological evolution."

There's much to admire about the visible universe, but if we're going to answer long-standing questions about how it has and will evolve, astronomers and scientists must leverage the power of present and future X-ray telescopes, in addition to other wavelengths, like ultraviolet and infrared. Months from now, the James Webb Space Telescope will launch into deep space and assume a position much like eROSITA's, expanding our capability to produce data for even further scientific inquiries into the mysteries of not only the Milky Way, but the ancient depths of the early universe.


Correction: An earlier version of this article implied that eROSITA was the first-ever space-based X-ray telescope. This has been updated to reflect that it's the first that can observe the entire sky.

message circleSHOW COMMENT (1)chevron