Trippy NASA study: Black holes are dark matter and they're everywhere

NASA caption: After masking out all known stars (next slide), galaxies and artifacts and enhancing what's left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors indicate brighter areas. The CIB glow is more irregular than can be explained by distant unresolved galaxies, and this excess structure is thought to be light emitted when the universe was less than a billion years old. Scientists say it likely originated from the first luminous objects to form in the universe, which includes both the first stars and black holes. less NASA caption: After masking out all known stars (next slide), galaxies and artifacts and enhancing what's left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors ... more Photo: NASA/JPL-Caltech/A. Kashlinsky (Goddard) Photo: NASA/JPL-Caltech/A. Kashlinsky (Goddard) Image 1 of / 33 Caption Close Trippy NASA study: Black holes are dark matter and they're everywhere 1 / 33 Back to Gallery

One reason scientists have not yet found dark matter -- the stuff the rest of the universe needs to be made of for there to be the kind of gravitational effects hard to explain without it -- could be that its not a thing so much as a condition: that is, instead of a massive exotic particle it might be black holes.

And not the black holes created by collapsing stars, but "primordial black holes" (PBHs) created by super dense matter present in the first second after the big bang.

What this would mean is that our galaxy, indeed all galaxies, are bubbles of visible matter deep in an ocean of these primordial black holes. It's an idea that has two key bits of data to support it: One is the lumpy nature of the cosmic infrared and X-ray background glows (the heat from when everything began, image above), and, two, is the collision of two massive black holes recorded as gravitational waves in September by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Wash., and Livingston, La.

"This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good," said Alexander Kashlinsky, an astrophysicist at NASA Goddard, in a news release. "If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun's mass."

Here's how the author of the NASA story, Francis Reddy, recounted the process in an email exchange with us:

Remember, this event would have happened by the first second of the universe's history, which was of course rapidly expanding. Ultimately, the local attraction of PBHs overcame expansion and they clustered into spheres (minihaloes) to create the first "lumps" of matter in the cosmos. They became the seeds for the formation of the first stars by creating conditions where gas could first become concentrated (by the gravity of the haloes) to form stars. The idea is, if this happened, the PBHs are still there, surrounding each galaxy. The collective mass of the PBHs surrounding each galaxy becomes the invisible mass that accounts for the gravitational effects we explain as caused by dark matter. So, the idea is that PBHs could be dark matter. There are consequences to that if true, and Dr. Kashlinsky has shown that two of them -- the cosmic infrared background and its relationship to the cosmic X-ray background -- are compatible with the idea. It's not exactly a compact chain of reasoning, but it does capture the imagination to think that black holes are all around us -- and that LIGO might have detected them as dark matter.

Indeed it does.

NASA caption for video: Primordial black holes, if they exist, could be similar to the merging black holes detected by the LIGO team in 2014. This computer simulation shows in slow motion what this merger would have looked like up close. The ring around the black holes, called an Einstein ring, arises from all the stars in a small region directly behind the holes whose light is distorted by gravitational lensing. The gravitational waves detected by LIGO are not shown in this video, although their effects can be seen in the Einstein ring. Gravitational waves traveling out behind the black holes disturb stellar images comprising the Einstein ring, causing them to slosh around in the ring even long after the merger is complete. Gravitational waves traveling in other directions cause weaker, shorter-lived sloshing everywhere outside the Einstein ring. If played back in real time, the movie would last about a third of a second.

How will they ever test this theory? NASA's release explained:

Occasionally, some primordial black holes will pass close enough to be gravitationally captured into binary systems. The black holes in each of these binaries will, over eons, emit gravitational radiation, lose orbital energy and spiral inward, ultimately merging into a larger black hole like the event LIGO observed. "Future LIGO observing runs will tell us much more about the universe's population of black holes, and it won't be long before we'll know if the scenario I outline is either supported or ruled out," Kashlinsky said.

So, if we start detecting more of these black-hole mergers, then the evidence begins to mount for those wild things to make up the bulk of the universe. Maybe that's how it all ends and the re-begins: All the black holes collapse into one and then ... blam!

But ... what really does happen to PBHs? Research lead Kashlinsky told us:

In principle, there may be some (small) modifications to the PBH mass due to accretion from either the rest of the dark matter (if it exists in WIMPs [Weakly Interacting Massive Particles, widely regarded as the leading candidate of what dark matter could be] in addition to PBHs) and/or gas and some of them may have merged as in LIGO event increasing the total mass and decreasing the total number, but that should not modify the original parameters significantly.

Jake Ellison can be reached at 206-448-8334 or jakeellison@seattlepi.com. Follow Jake on Twitter at twitter.com/Jake_News. Also, swing by and *LIKE* his page on Facebook. If Google Plus is your thing, check out our science coverage here.