Rebecca Smethurst aka Dr. Becky is an astrophysicist specializing in
research on Supermassive Black Holes aka SMBHs, arbitrarily defined as
having at least 10^5 solar masses.

The following is a 16-minute Youtube video that describes an
interesting conundrum about SMBHs:

<https://www.youtube.com/watch?v=6tXIoViA_0g>

Short version: There is good evidence that almost all galaxies have
SMBHs near their centers, and their masses are strongly correlated to
the size of their associated galaxies, which suggests they co-evolved.
There is also good evidence that about 10% of galaxies have merged
with at least one other of about the same size in their lifetime, as
Andromeda and Milky Way are expected to do in the next few billion
years. This suggests these merged galaxies have either:

1. multiple SMBHs, or
2. the SMBHs merged into one.

The conundrum is the math implies the SMBH's can't get closer to each
other than about a parsec within the age of the universe. In the
process of orbiting ever closer to each other, the SMBHs should kick
out from the merged galaxies objects that would otherwise reduce their
orbital velocity and allow them to continue to move closer to each
other. Without these objects, the SMBHs can't slow down and so can't
get closer. OTOH merging black holes are the only known way to create
SMBHs.

I have previously posted links which discuss Pulsar Timing Arrays,
which can detect gravitational waves created by merging SMBHs. The
Laser Interferometer Space Antenna aka LISA is also designed to
directly detect the extremely long wavelength gravitational waves of
merging SMBHs. However, this is an extremely complex and expensive
system, and is scheduled to be launched in 2037. Considering how many
times JWST was delayed, I would be surprised if LISA was launched
before 2050.

On Thu, 17 Aug 2023 01:30:47 -0400, jillery <69jpil69@gmail.com>
wrote:

Sent to wrong froup. My bad.

>Rebecca Smethurst aka Dr. Becky is an astrophysicist specializing in
>research on Supermassive Black Holes aka SMBHs, arbitrarily defined as
>having at least 10^5 solar masses.
>
>The following is a 16-minute Youtube video that describes an
>interesting conundrum about SMBHs:
>
><https://www.youtube.com/watch?v=6tXIoViA_0g>
>
>Short version: There is good evidence that almost all galaxies have
>SMBHs near their centers, and their masses are strongly correlated to
>the size of their associated galaxies, which suggests they co-evolved.
>There is also good evidence that about 10% of galaxies have merged
>with at least one other of about the same size in their lifetime, as
>Andromeda and Milky Way are expected to do in the next few billion
>years. This suggests these merged galaxies have either:
>
>1. multiple SMBHs, or
>2. the SMBHs merged into one.
>
>The conundrum is the math implies the SMBH's can't get closer to each
>other than about a parsec within the age of the universe. In the
>process of orbiting ever closer to each other, the SMBHs should kick
>out from the merged galaxies objects that would otherwise reduce their
>orbital velocity and allow them to continue to move closer to each
>other. Without these objects, the SMBHs can't slow down and so can't
>get closer. OTOH merging black holes are the only known way to create
>SMBHs.
>
>I have previously posted links which discuss Pulsar Timing Arrays,
>which can detect gravitational waves created by merging SMBHs. The
>Laser Interferometer Space Antenna aka LISA is also designed to
>directly detect the extremely long wavelength gravitational waves of
>merging SMBHs. However, this is an extremely complex and expensive
>system, and is scheduled to be launched in 2037. Considering how many
>times JWST was delayed, I would be surprised if LISA was launched
>before 2050.

On 8/17/23 01:30, jillery wrote:
> Rebecca Smethurst aka Dr. Becky is an astrophysicist specializing in
> research on Supermassive Black Holes aka SMBHs, arbitrarily defined as
> having at least 10^5 solar masses.

When one of those struck the earth it killed all the dinosaurs.