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(I'm a Ph.D. student working on LIGO) I think the author is missing the point a bit. LIGO is an observatory, and as it gets more sensitive, we certainly hope t
by stefco_ 9y ago
(I'm a Ph.D. student working on LIGO)
I think the author is missing the point a bit. LIGO is an observatory, and as it gets more sensitive, we certainly hope to see GW detections become normal!
It is already interesting and surprising that the universe contains so many intermediate mass black holes. This was unexpected, and our continued observation of them means that they are unlikely to be a statistical fluke.
Others have mentioned that LIGO also searches for other source types, like neutron star mergers, continuous GWs, and core-collapse supernovae. Assuming our predictions are right, these will be exciting to see, but eventually some of those observations will become routine.
However, you still gain a lot of information from routine observations! Routine observations let us start understanding the statistics of phenomena, which lets us figure out things like how common black holes are and when they evolve in our universe's history. It doesn't sound as sexy as a new discovery, but it's the kind of stuff you use to brainstorm and test new cosmological theories. You need it in order to do real science!
I'll also add that, as a new type of observatory, LIGO and Virgo are like an entirely new sense. It's like we can hear the universe all of a sudden, and our hearing is improving with time. What is really exciting to me is that we will most likely see things that nobody has predicted yet.
- nonbel 9y ago>"It is already interesting and surprising that the universe contains so many intermediate mass black holes. This was unexpected, and our continued observation of them means that they are unlikely to be a statistical fluke." Interesting. Can you put a number on how unexpected this was? What is the probability "the universe contains so many intermediate mass black holes" independent of the LIGO data?
- ajross 9y agoNot a professional, but AIUI the issue was the the models were just incomplete. These black holes are too big to be stellar collapse remnants, so they must have formed in the early universe. We don't have a good model for that yet that produces even stuff like the CBR spectrum or galaxy mass distribution. Nonetheless one of the things that no one was looking for was these medium black holes, so the fact that it's been observed is "surprising" in the sense of good news: it further constrains the big bang models.
- stefco_ 9y agoThis paper went out after the first detection in O1 (observing run 1) [1]. It discusses event rates inferred from the original event (GW150914) as well as previous predictions. CalTech also keeps a running list of detection papers, free for the public to read [2]. [1] https://arxiv.org/abs/1602.03842v3 https://arxiv.org/abs/1602.03842v3 [2] https://www.ligo.caltech.edu/page/detection-companion-papers https://www.ligo.caltech.edu/page/detection-companion-papers
- kobeya 9y agoThere’s two main formation pathways for black holes: ongoing stellar collapse and galaxy collapse in the early universe. The former makes stellar-mass black holes. The latter makes enormous million-stellar mass black holes or larger. That’s 5-6 orders of magnitude difference. What’s interesting is that we can measure/infer the mass of a black hole from these gravitational waves and we are finding a lot of ~1000x stellar mass black holes. Too big to be stellar collapse, too small to be galaxy centers. Where do these come from? The number for how many there should be is very close to zero. Presumably you’d only get one from a stellar black hole gobbling up enough mass to get that big, but 10 doublings is too much to have happened except by freak accident, and these are regularly occurring. The current best theory is that they formed in the early universe before or during galaxy formation by some process that we don’t yet understand.
- stromgo 9y agoWhere did you get this 1000x stellar mass figure from? According to https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations https://en.wikipedia.org/wiki/List_of_gravitational_wave_obs... so far the observed merger components were between 7.5 and 35.4 solar masses. The sample of stars in the night sky is biased by luminosity and longevity. I'd be curious to see a distribution of stellar masses that compensates for these two biases. On such a chart, extrapolating the trend in the high-mass range just before the error bars become too large would tell us whether 30-solar-mass stellar remnants are expected or unexpected by observation data.