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Black hole spins

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Grzegorz Wiktorowicz
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Message 738 - Posted: 12 Nov 2015, 15:52:52 UTC

Written by Wojciech Gładysz

There are many words one could use to describe a black hole: strange,
bizzare or out of this world. These are all valid terms, but they are not
very specific. You cannot objectively measure the strangeness of a black
hole, so scientists had to come up with a different idea for describing
those esoteric objects.

Black holes, as we now know, can be fully described by three numbers: their
mass, their spin and their electric charge. Astrophysical black holes (the
ones we are dealing with in our research) are believed to have almost no
electric charge, so our description simplifies. We are generally very happy
when something gets simpler, but the original difficulty of the problem
greatly reduces the excitement.

Let's say we want to know the mass and the spin of a given black hole.
First, we need to find it! It emits no light and almost no radiation
(except for the Hawking one that we do not know how to measure), so it does
not make our job easy. The only possible way of finding one, in the
vastness of space, is by looking at its gravitational interactions with
"visible" objects (such as the stars). Therefore, interacting binary
systems are the best cosmic laboratories available for the study of black
holes.

The mass part of a black hole is pretty simple - we can calculate it once
we know the mass of its companion star and the parameters of the binary
system they form (e.g. the separation of the objects). What about its spin?
And, what is more important, what is this spin you've been reading about?
Spin is nothing more than a fancy name for angular momentum. Our planet
rotates and thus have certain angular momentum - undisturbed, it will
continue keeping the same angular momentum forever. This is because in our
Universe angular momentum is conserved! If you'd like to change the
rotational motion of the Earth, you'd have to act on it by an external
torque (an asteroid maybe?). The spin of a black hole is therefore a
measure of how fast this black hole rotates.

There are at least three observational methods which allow you to estimate
the spin. None of them is perfect and the underlying physical principles
are greatly simplified. Therefore, the obtained spin values are very
uncertain. That is why we want to examine how our astrophysical
evolutionary models fit into that picture. I used the word "models" on
purpose - there is a bunch of them. When a star interacts with a black
hole, it can transfer its mass and make the black hole heavier. This
flowing mass carries momentum and may increase the spin of the black hole.
But the question is - what fraction of this flowing mass is transferred to
the black hole? 100% or maybe 50%? And what was the initial spin of a black
hole when it first formed? How the spin evolution would be affected by
changing its initial value from 0 to 0.5 on a 0-1 scale? The initial spin
value is still an open question in astrophysics. If we found a binary
system in which a black hole would be fed solely by stellar wind coming
from its companion and would be highly spinning, this would mean that the
spin comes from earlier evolutionary stages and is inborn rather than
acquired by mass accretion (which in the case of stellar-wind-fed systems
is negligible).

Black holes in interacting binaries may be fed by stellar winds coming from
their companions and by more direct mass transfers (the so-called Roche
Lobe overflows). We have models ready to examine the influence of these two
physical phenomena on the spin evolution. This is what we want to examine
with your help!
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Profile Aaron

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Message 2301 - Posted: 7 Jul 2017, 1:24:39 UTC - in response to Message 738.  
Last modified: 7 Jul 2017, 1:27:22 UTC

Thank you for this. It's nice to understand what my computers are working on!

What kind of data do you see in a completed work unit? Is it a full evolutionary story of a given system, or is it just a tiny piece of data that needs to be combined with many other work units in order for it to make any sense?
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Message 2757 - Posted: 28 Mar 2018, 23:59:19 UTC

Thank you for your help and informations.
God Bless You!
Fotós Miskolc
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Message 2759 - Posted: 29 Mar 2018, 8:20:52 UTC

Nice info... thank you very much.

Waiting for WU's to start crunching!

Cheers

MRC
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Ray

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Message 3102 - Posted: 25 Nov 2018, 20:08:14 UTC - in response to Message 738.  

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Ray

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Message 3103 - Posted: 25 Nov 2018, 20:36:31 UTC - in response to Message 3102.  

30 Billion years, can be as a blackhole disposition, we can as a whole replicate a 40.ipN/300K billion 90megawat, per imaterial body is 8oo, 36932@ if we reapititudal a compleat a 15million paracycle emptitude black hole we are able to travel to Mars in 500day. a 3aK[][p][][]2K,,,[ we could in actual fact preprovide a 369phoiladephia experiment transverse send a planetary cycle body from earth to Mars ie NYC, or salem, not much sense in actually bartering small frie, hey back to nuts, in any case translate a prolytical body as such, a poly duponte body as a city we may find in icear79382###_/ 300 ligh years using a ligacaine, or drc.arFiarg. as such at light years we can be able pw a body obtuse at approach to ligh speed or thereaby increase the velosity by flite through a planet, as approach to sucha moicron we are transformed into a formless body as is sanctified as is the planetary bias lov we can exemplify the witness of the planets of such an obstacle do not had form or physics characteristics at all we find these are travesed into a serieies of bodies before time , these 50billion light years, at the time of Christos blekate, we drew a patch from befgore time as which the bigbang no'' the fallenicacalcave. we are as it were at the time 3 if we use a pen drew it in the syphrebourge, we hold also we can usage an alien object into time
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Hal Bregg
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Message 3218 - Posted: 21 Jan 2019, 23:03:16 UTC - in response to Message 2301.  

Thank you for this. It's nice to understand what my computers are working on!

What kind of data do you see in a completed work unit? Is it a full evolutionary story of a given system, or is it just a tiny piece of data that needs to be combined with many other work units in order for it to make any sense?


Still now answer. I am, too, courious what actual completed WU would look like and what it would contain.
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Profile Krzysztof Piszczek - wspieram Polski projekt BOINC
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Message 3219 - Posted: 21 Jan 2019, 23:26:58 UTC - in response to Message 3218.  

It is zipped txt file with large number of app calculated numbers.
Krzysztof 'krzyszp' Piszczek

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Hal Bregg
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Message 3220 - Posted: 22 Jan 2019, 19:21:13 UTC - in response to Message 3219.  
Last modified: 22 Jan 2019, 19:26:24 UTC

So numbers, numbers and more numbers. Numbers everywhere.

Thanks for the info, Krzysztof.

PS.

Would it be and issue to remove jibberish messages posted by Ray?
Unless they are here for a reason.
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