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from the still-might-be-made-of-missing-socks dept.
Arthur T Knackerbracket has found the following story:
For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe's mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.
UC Berkeley physicists have dashed those hopes.
A supernova (bright spot at lower left) and its host galaxy (upper center), as they would appear if gravitationally lensed by an intervening black hole (center). The gravitational field of the black hole distorts and magnifies the image and makes both the galaxy and the supernova shine brighter. Gravitationally magnified supernovas would occur rather frequently if black holes were the dominant form of matter in the universe. The lack of such findings can be used to set limits on the mass and abundance of black holes. (Miguel Zumalacárregui image)
Based on a statistical analysis of 740 of the brightest supernovas discovered as of 2014, and the fact that none of them appear to be magnified or brightened by hidden black hole "gravitational lenses," the researchers concluded that primordial black holes can make up no more than about 40 percent of the dark matter in the universe. Primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times that of the sun collapsed into objects a hundred kilometers across.
The results suggest that none of the universe's dark matter consists of heavy black holes, or any similar object, including massive compact halo objects, so-called MACHOs.
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(Score: 0) by Anonymous Coward on Wednesday October 10 2018, @12:21PM (3 children)
The astronomer's only tool is basically analyzing light. Interesting that all their focus is now on invisible stuff they only infer exists from the light emitted by other objects. Or does it just seem that way because the media likes to talk about it?
(Score: 2) by Thexalon on Wednesday October 10 2018, @04:43PM (2 children)
No, it isn't. Some of the other things they can use:
1. EM radiation outside of the visible spectrum, such as X-rays [harvard.edu] and radio waves [greenbankobservatory.org]. They've been doing this since the 1930's, which would be about when EM radiation was just beginning to be understood.
2. Everything we already know about gravity.
3. Math.
4. Most recently, gravitational waves [caltech.edu].
For instance, as far as detecting black holes goes, the main focus there is on X-rays, which are outside of the visible EM range.
The reason that you're focused on the stuff that's visible is that the visible stuff is what produces those nice pretty pictures that convinces everyone that space telescopes are a good idea.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 0) by Anonymous Coward on Wednesday October 10 2018, @05:09PM
This is light, its all made of photons. Gravitational waves could be useful someday but up until now there has been no way to verify their interpretation of the data is correct. They need to detect something then predict something will happen in the future based on it.
(Score: 2) by bob_super on Wednesday October 10 2018, @05:30PM
I'm sure they've done the math, but nobody ever writes it down for the general public: how much of the universe's mass is in the photons and gravitational wave energy that's flying all around the place?