Starship Asterisk*

alter-ego wrote:

Chris Peterson wrote: ... But what actually happens beyond the event horizon, and especially very near the center, isn't certain.

I'll add that what happens at or near the event horizon isn't certain either. Since we haven't been able to really observationally (indirect or direct) probe that close, there is active interest in the details near the event horizon.

walker1001 wrote:

PhilT wrote:Antennae ???? I think it looks more like Africa. We have celestial bodies named after North America, California, etc. why not rename this one to Africa ?

Second that.

PhilT wrote:Antennae ???? I think it looks more like Africa. We have celestial bodies named after North America, California, etc. why not rename this one to Africa ?

Chris Peterson wrote: ... But what actually happens beyond the event horizon, and especially very near the center, isn't certain.

Chris Peterson wrote:

ta152h0 wrote:
one more, considering this is Sunday. Are black holes still considered singularities acting as giant magnets ?

Giant magnets? They were never considered to act like magnets.

• Perhaps you are thinking of a magnetar or a Dirac string:

http://en.wikipedia.org/wiki/Dirac_string wrote:
<<A Dirac string is a hypothetical one-dimensional curve in space, conceived of by the physicist Paul Dirac, stretching between two Dirac magnetic monopoles with opposite magnetic charges, or from one magnetic monopole out to infinity. The gauge potential cannot be defined on the Dirac string, but it is defined everywhere else. The Dirac string acts as the solenoid in the Aharonov–Bohm effect, and the requirement that the position of the Dirac string should not be observable implies the Dirac quantization rule: the product of a magnetic charge and an electric charge must always be an integer multiple of 2π. The Dirac string is the only way to incorporate magnetic monopoles into Maxwell's equations, since the magnetic flux running along the interior of the string maintains their validity.>>

• However, black holes may possibly have a little "hair":

http://www.scientificamerican.com/article/black-holes-may-have-hair/ wrote: Black Holes May Have "Hair"
Oct 21, 2013 |By Megan Gannon and SPACE.com

<<Astronomer John Wheeler, who coined the term "black hole" nearly 50 years ago, famously said that "black holes have no hair" because of their simplicity. Now "hair" is used as a colloquial term among physicists as a stand-in for any other measure needed to describe a black hole that departs from: their mass, their angular momentum (how fast they spin) and their electric charge. [However,] Thomas Sotiriou, a physicist at the International School for Advanced Studies of Trieste and his colleagues looked at black holes in the context of the equations of scalar-tensor theories of gravity. The researchers found that [such non-Einsteinian] black holes [may] develop scalar "hair" when ordinary matter surrounds them.>>

See: http://www.scientificamerican.com/artic ... have-hair/

ta152h0 wrote:one more, considering this is Sunday. Are black holes still considered singularities acting as giant magnets ?

neufer wrote:I'm pretty sure that all angular momentum is quantized.

Chris Peterson wrote:

neufer wrote:
All particles have either integer spin or half-integer spin
(in units of the reduced Planck constant ħ)
but occasionally the equatorial speed is more relevant.

You do like to add to confusion sometimes, don't you?

• You're expecting a confusion confession

Chris Peterson wrote:
"Spin" is not the same as "rotation". In quantum mechanics (which this question did not address), spin is a measure of quantized angular momentum. It does not mean that a particle has a physical rotation, with some "equatorial" speed. Black holes demonstrate physical rotation, and their angular momentum is not quantized.

http://en.wikipedia.org/wiki/Azimuthal_quantum_number wrote:
<<The azimuthal quantum number is a quantum number for an atomic orbital that determines its orbital angular momentum and describes the shape of the orbital. The azimuthal quantum number is the second of a set of quantum numbers which describe the unique quantum state of an electron (the others being the principal quantum number, following spectroscopic notation, the magnetic quantum number, and the spin quantum number). It is also known as the orbital angular momentum quantum number, orbital quantum number or second quantum number, and is symbolized as ℓ

The letters after the f sub-shell just follow f in alphabetical order except those already used. One mnemonic to remember the sequence S. P. D. F. G. H. ... is:

"Sober Physicists Don't Find Giraffes Hiding In Kitchens Like My Nephew".

A few other mnemonics are:

[list]Smart People Don't Fail,
Silly People Drive Fast,
Silly Professors Dance Funny,
Scott Picks Dead Flowers,
Some Poor Dumb Fool! etc.>>[/list]

neufer wrote:All particles have either integer spin or half-integer spin
(in units of the reduced Planck constant ħ)
but occasionally the equatorial speed is more relevant.

booky1@earthlink.net wrote:Wait - the previous versions of this object appear to be reversed left to right. Which is correct?

ta152h0 wrote:
I keep my red/blue glasses next to this laptop, just in case the APOD guys decide to ujpload another anaglyph.

• But his brain was so loaded it nearly ujploaded
  The poor girl would shake with alarm;
  He'd ne'er leave the girl with the strawberry curls
  And the band played on.

ta152h0 wrote:
Off topic- recent studies indicated, and reported one black hole spun at half the speed of light. I thought spins were measured in radians/second or more commonly, revolutions per unit of time .

Nitpicker wrote:

APOD Robot wrote:When two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space.

When playing golf, one's opponents often claim that trees (eucalypt, say) are 90% air. This is probably true, but when trying to hit a golf ball through a gum tree, it is the free cross-sectional area that is relevant, and this is much smaller. Much like astronomy, golf is very humbling.

ta152h0 wrote:I keep my red/blue glasses next to this laptop, just in case the APOD guys decide to ujpload another anaglyph. Off topic- recent studies indicated, and reported one black hole spun at half the speed of light. I thought spins were measured in radians/second or more commonly, revolutions per unit of time .

JohnD wrote:In which case, doesn't the Drake Equation need another expression, perhaps Ffp for "Fraction fatally perturbed"? I couldn't put a value on it.

JohnD wrote:It's always said that even in a galactic collision the stars stay apart. But what about the gas and dust that are there too?
Star forming areas will develop, with all the radiation that will engender. Will there be a higher rate of nova formation, or other events that would raise the radiation level in the vicinity?
For those reasons, would a colliding galaxy be less favourable for life than one in a quieter neighborhood?

I understand that the Sun is presently in a low density area of the Milky way, and will enter one with a higher density soon (galactic soon - hundreds of thousands of years). What can we expect from that?

APOD Robot wrote:When two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space.