My theory of supermassive BH formation is that they were formed before atoms even existed. Atoms are notorious for resisting collapse. This would make them very early indeed, but no-one can see a mechanism for their formation in a reasonable time once matter, as opposed to other energy (such as photons) was almost entirely atomic.

I think (but could be wrong) that we'll have to wait for eLISA - the interferometer in space - before we have the sensitivity to detect primordial gravitational radiation (if any) from before the epoch of last scattering (WMAP, Planck &c).

thanks....
the down side is if we don't detect anything .....

a) there wasn't anything to detect

b) our detector is insufficent

how would we ever know which???

Most models I'm aware of predict a testable (in principle) spectrum of gravitational radiation and eLISA should be sufficient to distinguish between them. Knowing the experimentalists though, I would not be too shocked if something else comes along sooner. For example, Roger Penrose predicts patterns from black hole evaporation in a previous epoch should be discernible. I'm sure there are others of which I know nothing...

With more observed events and improved sensitivity, it may be possible to test alternatives to GR, alternatives that predict different patterns of gravitational radiation.

Currently, the sources' masses are estimated assuming GR. Though GR has been very successful so far, most of its successes so far have been in weak-field situations, and merging black holes is clearly a strong-field one.

Europe selects grand gravity mission

LISA (space based interferometer) gets the green light but maybe a bit too late for some of us.

...
The earmarked launch date for LISA is 2034. Efforts will be made, though, to bring this forward because of the excitement that currently surrounds gravitational wave science.

"It won't be much earlier - even if we had all the money in the world," Prof Giménez said. "It's a question of the technology readiness. It takes time to build a mission as complex as this. 2030 is the earliest we could do it, assuming we get the money we need and have no problems."

newolder wrote:Europe selects grand gravity mission

LISA (space based interferometer) gets the green light but maybe a bit too late for some of us.
...

So you're not 6 after all!

and NASA has a LISA webpage again: https://lisa.nasa.gov

A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

LIGO source

An arXiv release is expected soon that should detail the elements of the catalogue... But I've seen a report that the catalogue includes 4 compact binary mergers (BH-BH) not previously described with one of them resulting in an 80+ Solar mass object with 5 solar masses going into gravitational radiation. This is the largest, most distant and most rapidly spinning remnant yet. Catalogued as GW170729

ETA I've just noticed that the pdf is linked at the above LIGO page. That's my bedtime story sorted for tonight then...

I made an A4 paper size calculation/estimation with low math, in which i analyze the stability of a non rotating, electrically charged black hole. Very weird really because i used only surface tension, gravity and Coulomb law. The result astonished me again. Without complications finally i got a 6 grade algebraic equation with particular conclusions. No high math like ODE or PDE occur in the derivation! This black hole explodes -at the result radius- and mashed inside to its event horizon (EH) INSIDE. We get a hollow black hole. I am still thinking on the amazing ways of interpretation. Since this happens New universe may be born inside? Unfortunately we cannot see under EH... maybe this speculation could resolve the Fermi paradox too. Maybe i am wrong but really enjoyed! maybe not true but can be promising for scifi writers

The entropy of gravitational black holes is proportional to their surface area (not volume) so you might be onto something but I wouldn't worry about resolving the Fermi paradox just yet...

Obseving run 3 (O3) has begun at the LIGO (x2) & VIRGO (x1) stations and the first possible binary black hole merger notification has been issued on Monday, 8th April 2019: https://gcn.gsfc.nasa.gov/notices_l/S190408an.lvc

Let the science continue (and don't forget about the Event Horizon Telescope release tomorrow, Wednesday)...

On the sky:


Distance estimate converts to about 4.8 billion light years.

No EM observation entries so far.

Data source

It seems to be a good week for black holes... A second candidate event in O3:
Circular

Event database entry -> 2.6 billion light years -ish distant.

Binary black hole merger at >99% probability.

... and now it's binary neutron star merger time (probably): https://gracedb.ligo.org/superevents/S190425z/view/



About 2 to 3 hours ago so the telescopes should be slewing. Optical, multi-messenger follow up expected later. Event tracked to approx 1 billion light years distance (266 Mpc).

ETA +1 day, via @LIGO:

Prime candidate for the #S190425z counterpart is a #kilonova visible for a few days in optical/IR light. But (unlike #GW170817) astronomers have 25% of the sky to search this time, so it helps to have many eyes on the sky, and it's why our #O3 public alerts are so important...

Candidates coming in rapidly now:

...
https://gracedb.ligo.org/superevents/S190426c


The classification of the GW signal, in order of descending

probability, is BNS (49%), MassGap (24%), Terrestrial (14%), NSBH

(13%), or BBH (<1%).

...

NASA source

377 give or take 100 Mpc distant.

Edit for distance estimate correction.

Public talk by Dr. David Reitze, Executive Director of the LIGO Laboratory, Caltech.

To be live streamed at this youtube in about 27 hours from now-ish: https://www.youtube.com/watch?v=ZQzKpBaQx3I

Further details at The Gravitational Wave Astronomical Revolution

A new month and a new candidate binary black hole merger about 1.2 billion light years distant.

Event notification & details link

Graphic definition of the categories listed in those reports:

Another binary neutron star candidate about 900 million light years distant: https://gracedb.ligo.org/superevents/S190510g/view/

newolder wrote:Another binary neutron star candidate about 900 million light years distant: https://gracedb.ligo.org/superevents/S190510g/view/

ETA via @LIGO

After analysing more data, we now estimate a 58% probability of it being noise, and only 42% of it being a real binary neutron star. Further updates will be issued as we learn more...

Latest candidate, from yesterday, for a binary black hole merger: https://gracedb.ligo.org/superevents/S190513bm/view/

More than 6 billion light years distant.