Over the past three years, LIGO discovered ten independent instances of merging black holes in our Universe.
Despite all we’ve learned, five big unknowns still plague scientists.
1.) How small are the lowest-mass black holes?
LIGO has yet to detect any low-amplitude binaries, providing no information about this population.
2.) Is there a pile-up of black holes above a certain mass?
We don’t have enough detections to know what mass of black holes are most abundant.
3.) What are the mass ratios in binary systems?
The ones found so far are of nearly equal, 1-to-1 ratio masses. Large mass differences are hitherto undetected.
4.) Where do black hole binaries form?
We haven’t identified whether they’re primarily located in rich clusters or isolated galaxies.
5.) Do merger rates change as the Universe evolves?
A dearth of events, particularly as a function of distance, prevents understanding whether or how merger rates change.
On the other hand, we can already draw two amazing conclusions.
1.) 99% of black holes in binary, merging systems are below 43 solar masses.
2.) Our observable Universe contains 800,000 ± 500,000 merging black hole binaries per year.
With LIGO’s new data run coming later this year, we hope to obtain superior answers.
Mostly Mute Monday tells the scientific story of a physical phenomenon in images, visuals, and no more than 200 words. Talk less; smile more.