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#126 2005-01-31 18:15:46

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

If you're interested in balloon astronomy, you should check out the lecture by Walter Lewin (x-ray astronomer at MIT) http://ocw.mit.edu/OcwWeb/Physics/8-02E … x.htm]here (Lecture #36, the last one).  He has a nice slideshow about 8 minutes into it.  Also talks about neutron stars afterwards.

EDIT :: Needs RealPlayer to view

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#127 2005-02-02 21:31:27

SpaceNut
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

More on another telescope using balloons for lift under the Earth or space telescope thread.

Lost and Found: X-ray Telescope Locates Missing Matter

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#128 2005-02-03 05:56:17

Palomar
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From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

If you're interested in balloon astronomy

*Hi Mark.  Actually I'm -more- interested in the reason for that balloon mission:  Supernova acceleration of cosmic rays, heavy nuclei bombardment, etc.  (The balloon itself is interesting, but secondarily so).

Actually, we do have a http://www.newmars.com/forums/viewtopic … Scientific Ballooning thread.  It's not gotten much attention so far. 

This is one of those unavoidable "overlap" situations.  That thread is open; there is a link or two in it as well.

I'd prefer "Singularity" stay focused on black holes, magnetars, gamma rays, etc.  But of course a bit of overlap is understandable.

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#129 2005-02-10 06:10:12

Palomar
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From: USA
Registered: 2002-05-30
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

*This article goes very nicely with the program about supermassive black holes I saw in 2003 (mentioned in this thread previously):

http://www.spaceref.com/news/viewpr.htm … imulations show how growing BH's regulate galaxy formation

The black hole to quasar to star formation within a galaxy interaction; that BH mass is related to the size of a galaxy is in agreement with what this simulation shows:

Di Matteo and her colleagues simulated the collision of two nascent galaxies and found that when the two galaxies came together, their two supermassive black holes merged and initially consumed the surrounding gas. But this activity was self-limiting. As the remnant galaxy's supermassive black hole sucked up gas, it powered a luminescent state called a quasar. The quasar energized the surrounding gas to such a level that it was blown away from the vicinity of the supermassive black hole to the outside of the galaxy. Without nearby gas, the galaxy's supermassive black hole could not "eat" to sustain itself and became dormant. At the same time, gas was no longer available to form any more stars.

"We've discovered that the energy released by black holes during a quasar phase powers a strong wind that prevents material from falling into the black hole," Springel said. "This process inhibits further black hole growth and shuts off the quasar, just as star formation stops inside a galaxy. As a result, the black hole mass and the mass of stars in a galaxy are closely linked.

--Cindy

::EDIT::  http://antwrp.gsfc.nasa.gov/apod/ap030703.html]Vela Pulsar's Dynamic Jet

These are false-color x-ray images from Chandra.  This pulsar was "born" over 10,000 years ago via a supernova explosion. 

In this time-lapse series of pictures, the jet seems to dance around very much like an out-of-control firehose, shooting along the pulsar's direction of motion (toward the top right corner) to a length of about half a light-year while whipping back and forth at about half the speed of light.


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#130 2005-02-11 09:16:27

Palomar
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From: USA
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

5 March 1979:  Soviet spacecraft Venera 11 and 12 were in the inner Solar System, drifting along on an elliptical orbit.  Radiation readouts stayed around 100 counts per second (nominal).  At 10:51 Eastern Standard Time a gamma radiation pulse hit both probes.  In a fraction of a millisecond the radiation level soared above 200,000 counts per second and swiftly went off-scale.  Eleven seconds after that, gamma rays overpowered Helios 2 (NASA probe).  The radiation wave reached Venus soon after and saturated the detector on the Pioneer Venus Orbiter.  Seconds after that, Earth got hit. 

*In 0.2 second as much energy as the Sun radiates in approximately 10,000 years was released. 

*Also, it concentrated that energy in gamma rays as opposed to spreading it across the electromagnetic spectrum.  That was our first-detected experience with a magnetar.

*After the initial hard hit more (but gentler, fainter) bursts of gamma rays were detected as coming from the same region of the sky.


http://antwrp.gsfc.nasa.gov/apod/ap030704.html]*N49 and "March 5th Event" magnetar 

N49 also marks the location of another energetic outburst -- an extremely intense blast of gamma-rays detected by satellites on March 5, 1979. That date was the beginning of an exciting journey in astrophysics which led researchers to the understanding of an exotic new class of stars. The source of the "March 5th Event" is now attributed to a magnetar - a highly magnetized, spinning neutron star also born in the ancient stellar explosion which created supernova remnant N49.

The magnetar travels 1200 km/second through the debris cloud (which is contained in the LMC; debris spans 30 light years).

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#131 2005-02-11 10:09:17

SpaceNut
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

What a spectacular blast but where and which one is the remaining nuetron star from this blast? ???

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#132 2005-02-11 10:21:08

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

What a spectacular blast but where and which one is the remaining nuetron star from this blast? ???

*Hi SpaceNut:  Unfortunately they don't pinpoint the magnetar's location in the photo and I've not yet found another photo which does contain an arrow or marker.  [::edit::  Which actually is odd, because the magnetar was once the star which exploded, thereby creating the debris cloud too of course.  So it's doubly surprising they didn't indicate it with an arrow or marker  ::end edit::]

Sorry.

--Cindy

::EDIT::  Oh, oh, oh!  I see what happened.  My wording indicated it'd be pointed out.  sad  I'll change my wording in the post.  Sorry, SpaceNut; I honestly didn't intend to create confusion.


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#133 2005-02-11 10:49:22

SpaceNut
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

Actually the confusion comes from the page link:

The source of the "March 5th Event" is now attributed to a magnetar - a highly magnetized, spinning neutron star also born in the ancient stellar explosion which created supernova remnant N49

So I guess the question is if a star explodes is there still some core material left that would make up the new neutron star or magnetar or is all that remains the cloud as viewed. big_smile

Edit:
From one of the links I got to the page with how it was located

The burster is located 

In the months and years after March 5, 1979, scientists analyzed data from the different spacecraft. Each detector had a clock that tagged the time on when the gamma rays first hit, to the nearest millisecond. By comparing these times from spacecraft at different places in the solar system, astronomers were able to tell at what angle the plane wavefront of gamma rays had passed through the solar system. This in turn told them where in the sky the burst came from. It took more than a year to do this accurately. The result was a huge surprise.

The xray picture though still does not make it clear as to where it is in the visible image.

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#134 2005-02-11 11:41:09

Palomar
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From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

Actually the confusion comes from the page link:

The source of the "March 5th Event" is now attributed to a magnetar - a highly magnetized, spinning neutron star also born in the ancient stellar explosion which created supernova remnant N49

So I guess the question is if a star explodes is there still some core material left that would make up the new neutron star or magnetar or is all that remains the cloud as viewed. big_smile

*SpaceNut:  Based on what I've read (which could be wrong of course...I'm just an amateur astronomer):  The magnetar is the former star which went supernova.  The debris cloud is what's left of the star's outer gas layers when it blew; the magnetar is what remains of the actual stellar body (-edit-: although this does not happen in the case of every supernova, i.e. not all supernovaed stars become magnetars; but this particular star did).

Does this help?  If this is wrong, someone else correct me please.

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#135 2005-02-14 13:04:04

Palomar
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From: USA
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

Swifts]http://www.universetoday.com/am/publish/swift_first_burst.html?1422005]Swift's 1st burst *pinpointed*

*An update on the burst detected 23 December 2004.  Was "in" the (southern) constellation of Puppis.  Three additional bursts in January (some of this is repeated info). 

These bursts are, of course, being studied by 'scopes around the globe. 

Cosmic gamma-ray bursts produce more energy in the blink of an eye, than the Sun will release in its entire lifetime.

That is always mind-boggling, no matter HOW many times you read it.  :-\ 

Because Swift allows a response to new gamma-ray bursts within minutes, astronomers hope to use the intense light from gamma-ray bursts as cosmic "flashlights." They plan to use the bright visual afterglows to trace the formation of the first galaxies, only a few hundred million years after the Big Bang, and the composition of the gas that permeates the universe. "This is much like using a flashlight to study the contents of a dark room," said Berger. "But because the flashlight is on for only a few hours, we have to act quickly."

One scientist comments that Swift is opening a new window on our universe and can't wait to see what it catches.  Ditto!

Lots of great cooperation going on towards the further study of gamma rays. 

"I'm thrilled," said Berger. "We've shown that we can chase the Swift bursts at a moment's notice...! This is a great sign of exciting advances down the road."

Ditto again.  Wish I were actually a part of the action, rather than merely yapping about it on the 'net. 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#136 2005-02-16 12:09:44

Palomar
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From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … ifferences in black hole "diets"

*Some is a rehash of previously posted info.

Supermassive black holes (those with 100 million times our Sun's mass) gorged themselves "voraciously" until they ran out of gas and dust, whereupon they were forced into a starvation diet -- and their growth stopped.

Smaller black holes (10 - 100 million Solar masses) apparently have a more "controlled eating plan."  They take in smaller portions and continue to grow.

Some are gluttons on binges, others prefer to graze.  LOL.

-also-  Census taken:

Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first time, the ones in between have been counted properly.

"We need to have an accurate head count over time of all growing black holes if we ever hope to understand their habits, so to speak," -- Richard Mushotzky

--Cindy

::EDIT::  There's also a note in the article that some "previously hidden BH's" are apparently underweight (or below their weight limit).  Hmmmmm.


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#137 2005-02-18 06:50:00

Palomar
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From: USA
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.spacedaily.com/news/stellar-05g.html]A flash of light from across the galaxy so powerful

*...it bounced off Luna and lit up Earth's upper atmosphere.  yikes  27 December 2004. 

My god.

It's the brightest explosion yet detected from beyond our Solar System; for over 1/10th of a second it was brighter than a full Moon. 

The light detected from the giant flare was far brighter in gamma rays than visible light or X-rays. It was probably created by an unprecedented eruption on the surface of an exotic neutron star which is classed both as an ultra-magnetic magnetar and as a soft gamma repeater (SGR).

Is dubbed SGR 1806-20 -- which is 50,000 l/y from us, and is located "in" Sagittarius. 

"This is a once-in-a-lifetime event. We have observed an object only 20 kilometres across, on the other side of our Galaxy, releasing more energy in a tenth of a second than the Sun emits in 100,000 years," said Fender.

Geez. 

--Cindy

::EDIT::  http://www.terradaily.com/news/weather-05i.html]Earth itself emits gamma ray flashes?

Whoa. 

Named Terrestrial gamma-ray flashes (TGFs), these very short blasts of gamma rays lasting about one millisecond, are emitted into space from Earth's upper atmosphere. Scientists believe electrons traveling at nearly the speed of light scatter off of atoms and decelerate in the upper atmosphere...

There may be 50 per day.  They say this energy is "as high as" gamma rays from black holes and neutron stars.  :-\ 

The exact mechanism that accelerates the electron beams to produce TGFs is still uncertain, he said, but it probably involves the build-up of electric charge at the tops of thunderclouds due to lightning discharges. This results in a powerful electric field between the cloudtops and the ionosphere, the outer layer of Earth's atmosphere.

They're speculating on the relation of this to blue jets, sprites, etc.


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#138 2005-02-18 11:46:07

Palomar
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From: USA
Registered: 2002-05-30
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

*Either this is entirely new news or they're just now catching up.  I know I posted an article similar to this at least 1-1/2 months ago, but am not sure it's the same system and I can't find it to make sure.  sad  It must be another system because it wouldn't take them this long to post the other event I'm recalling.

Anyway:

http://www.universetoday.com/am/publish … 05]Fastest Spinning Pulsar Found

Includes image.

Actually it's in a binary system.  They are approximately as close to one another as Earth to Luna; they orbit each other every 2-1/2 hours.  The x-ray pulsar of the pair rotates 600 times per second.  My god.  On this pulsar, a day would last 0.0016 seconds and a year is 147 minutes. 

The x-ray pulsar is siphoning material off its companion.  It's a bit complex, and happy reading! 

'The rate at which this object is spinning is truly amazing,' commented Dr Shaw. 'It gives us an opportunity to study the effects of such extreme forces of this rotation on the exotic material found in neutron stars, which does not exist on Earth. It is possible that there are more of these objects waiting to be discovered, *!--possibly even faster ones--!*; if they are there, INTEGRAL will find them.'

--Cindy

P.S.:  The post above this one has two really interesting articles in it as well; was posted earlier today.


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#139 2005-02-21 08:24:34

Palomar
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From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.space.com/scienceastronomy/0 … .html]Baby black hole?  Runt of the litter?

*First article I recall pertaining to this.  Is the central BH in the galaxy NGC 4395.  Lies 14 million l/y away.  Astronomers have discovered it is more massive than originally thought, but "is still the least massive of its type ever detected."  Discovered in 1989 and is approximately 100 times smaller than other black holes found at the nucleus of active galaxies.

One astronomer says it's a bit smaller than he'd anticipated.

Discusses theoretical differences between stellar and supermassive black holes (has been discussed here before).

They're wondering if the BH in question remained small because it's already consumed all stellar material available to it or if it was "starved of cosmic food all along."

In order to measure the mass of the central black hole inside NGC 4395, researchers used a technique called reverberation mapping...

In the past, astronomers have estimated the NGC 4395’s central black hole to be between 55,000 and 66,000 solar masses. But the new measurements by Laor and Peterson suggest the object contains a lot more material. The astronomers hope the measurement will help them better understand the role black holes play in the development of galaxies.

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#140 2005-02-21 08:31:53

Palomar
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From: USA
Registered: 2002-05-30
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.spacedaily.com/news/stellar-05g.html]A flash of light from across the galaxy so powerful

*...it bounced off Luna and lit up Earth's upper atmosphere.  yikes  27 December 2004. 

My god.

It's the brightest explosion yet detected from beyond our Solar System; for over 1/10th of a second it was brighter than a full Moon. 

The light detected from the giant flare was far brighter in gamma rays than visible light or X-rays. It was probably created by an unprecedented eruption on the surface of an exotic neutron star which is classed both as an ultra-magnetic magnetar and as a soft gamma repeater (SGR).

Is dubbed SGR 1806-20 -- which is 50,000 l/y from us, and is located "in" Sagittarius. 

"This is a once-in-a-lifetime event. We have observed an object only 20 kilometres across, on the other side of our Galaxy, releasing more energy in a tenth of a second than the Sun emits in 100,000 years," said Fender.

Geez. 

--Cindy

http://antwrp.gsfc.nasa.gov/apod/image/ … g]Magnetar Burst Sequence -- IMAGE

*Nice illustration.  Is today's Astropix offering.  Here's the caption which goes with:

Was the brightest Galactic blast yet recorded a key to connecting two types of celestial explosions? Last December, a dense sheet of gamma rays only a few times wider than the Earth plowed through our Solar System, saturating satellites and noticeably reflecting off the Moon. A magnetar near our Galactic Center, the source of Soft Gamma Repeater (SGR) 1806-20, had unleashed its largest flare on record.  The brightness and briefness of the tremendous explosion's initial peak made it look quite similar to another type of tremendous explosion if viewed from further away -- a short duration gamma-ray burst (GRB).  Short duration GRBs are thought by many to be fundamentally different than their long duration GRB cousins that are likely related to distant supernovas.  Illustrated above is a series of drawings depicting an outgoing explosion during the initial SGR spike. A fast moving wave of radiation is pictured shooting away from a central magnetar. The possible link between SGRs and GRBs should become better understood as more and similar events are detected by the Earth-orbiting Swift satellite.

Amazing critters. 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#141 2005-02-23 16:08:26

Palomar
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From: USA
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … 322005]New article on black holes & cosmic x-ray background

*Says matter whips around a black hole at near to the speed of light before being gobbled up.  High-energy radiation results from the superheating. 

The whole sky is filled with a diffuse, high energy glow: the cosmic X-ray background. In the last years the astronomers could show, that this radiation can almost completely be associated with individual objects. Similarly, Galileo Galilei in the beginning of the 17th century resolved the light of the Milky Way into individual stars. The X-ray background originates in hundreds of millions of supermassive Black Holes, which feed from matter in the centres of distant galaxy systems.

European researchers have measured iron hurtling around black holes.  They've "found a relativistic effect because it's moving so quickly."

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#142 2005-03-08 11:58:54

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

Yay!!  :band:  A new article about black holes. 

http://www.universetoday.com/am/publish … 32005]Area around BH's "surprisingly turbulent"??

What's up with that?  Based on all the stuff posted here for quite a while, that doesn't seem like anything surprising to me.  :-\  Does it to you?

Anyway, does mention the "governor" in respect to the workings of these critters.  Those are new comments.

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#143 2005-03-14 08:08:46

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://science.nasa.gov/headlines/y2005 … .htm]Happy birthday Albert Einstein

*Check out the article and links within it.  :up:  I'm very pressed for time, can't currently comment beyond this. 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#144 2005-03-16 08:16:43

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … 2005]Black holes might obscure earliest times

*From astrophysicists at Penn SU who are

concerned that the light bending effects of gravity around black holes might be so severe that early times in the Universe might be impossible to study.

Will opt to copy and paste, as my brain's currently not up to summarizing what I read...

these large gravity wells also affect electromagnetic radiation and may hinder our ability to ever locate the center of the universe

"Any attempt to discover what was happening a long time ago at the beginning of our universe must take into account what gravitationally assisted negative refraction does to the radiation being viewed," says Dr. Akhlesh Lakhtakia

Hmmmm.  Well, now what?  Discusses negative refraction and observation perspective. 

"We should not be disappointed if we cannot discover the origin of the universe," says Lakhtakia. “The gravitational effect probably makes it so that we do not really know where we are looking.”

Great.  sad

Nevertheless, Lakhtakia and his collaborators are optimistic that scientists will eventually overcome many of the obstacles put forward by negative refraction in outer space.

Now that's what I love about science:  End it on a positive note!  smile  Yes, hopefully so.  It wouldn't be the first obstacle the brainiacs have overcome. 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#145 2005-03-21 12:53:54

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … 2005]Black holes could contain a perfect fluid

*This is one of -- if not THE -- weirdest articles about black holes I've ever read.  Have fun.  tongue 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#146 2005-03-22 12:54:44

Palomar
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Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

*Medium-weight black holes proven to exist?

http://www.universetoday.com/am/publish … 32005]From galaxy M74

Perhaps has 10,000 x the mass of Sol.  Observed by Chandra.  This BH could usher in the certainty of that new class of BH's they've been speculating about (medium).

"It is important to verify the existence of intermediate-mass black holes, because they would bridge the gap between stellar-mass black holes and supermassive black holes in the centers of galaxies,"

cool

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#147 2005-03-27 11:12:36

DanielCook
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From: Atlanta, GA
Registered: 2004-02-19
Posts: 90

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … 2005]Black holes could contain a perfect fluid

*This is one of -- if not THE -- weirdest articles about black holes I've ever read.  Have fun.  tongue 

--Cindy

I was also initially confused by this article ... but read another article elsewhere that clarifies: the "black holes" they are referring to are not the regular "astronomical" black holes we all know and love, but some feature of string theory ... still very fascinating.


-- memento mori

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#148 2005-03-27 16:47:36

reddragon
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Posts: 193

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

Black Holes Could Contain a Perfect Fluid

How can a singularity be a fluid? Doesn't a fluid have to contain multiple distinct particles. A black hole is, I think, compacted so tightly that it's all one infinitely small particle, a singularity. A single molecule of water for instance isn't specifically a fluid or a solid because it's only one particle. (It could be part of a fluid or a solid.) I don't think you can define a state of matter except in relation to the strength of bonds between it's atoms and the properties resulting from that.

A black hole's temperature should be 2 trillion degrees Celsius

Based on other things I have read I thought that black holes had very low temperatures. Some scientists once believed that black holes had a temperature of 0 K, assuming that with an escape velocity greater than the speed of light they could not emit any kind of radiation. Stephen Hawking proved that they do emit some radiation and thus have a temperature. However, I had always thought that this was still quite low.

At such extreme heat, it is not surprising that it might evaporate like other liquids. That is exactly what happens to black holes in three spatial dimensions, according to a well-accepted theory of particle radiation from black holes by physicist Stephen Hawking.

The evaporation of black holes due to Hawking radiation is not anything like the evaporation of liquids due to heat. The evaporation of liquids occurs when molecules of the liquid gain enough energy to escape from it and break the bonds that hold a liquid in a fixed volume. Hawking radiation involves quantum vacuum fluctuations. These are the creation and subsequent annihilation of particle/anti-particle pairs in otherwise empty space for reasons that I do not pretend to understand. If I understand Hawking radiation correctly, the anti-particle sometimes falls into the black hole before being annihilated and the regular particle avoids destruction and goes happily on its way. (Unless it too falls into the black hole. I'm not sure what happens then.) Anyway this somehow causes the black hole to have to give off some of its mass in radiation. Again I don't really understand why this is.

I know I'm in over my head here. I don't really understand all this stuff, and I'm probably misinterpreting what the article is saying. If anyone here has a better understanding of theoretical physics, perhaps you can point out where I went wrong.

Edit:

I was also initially confused by this article ... but read another article elsewhere that clarifies: the "black holes" they are referring to are not the regular "astronomical" black holes we all know and love, but some feature of string theory ... still very fascinating.

Sorry, I missed that at first. Are these black holes still singularities with escape velocities greater than c?


Far out in the uncharted backwaters of the unfashionable end of the Western Spiral arm of the Galaxy lies a small unregarded yellow sun.

             -The Hitchhiker's Guide to the Galaxy
              by Douglas Adams

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#149 2005-04-01 20:19:44

DanielCook
Member
From: Atlanta, GA
Registered: 2004-02-19
Posts: 90

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

ok ... lets see if I can explain this ...

The researchers where drawing comparisons between the astronomical black-holes (that result from gravitational collapse of matter) and a quark-gluon plasma http://www.space.com/scienceastronomy/0 … ng.html](a state of matter that existed shortly after the big bang)

When both of these are expressed in ten dimensions using string theory, they are similar in structure and may have similar characteristics - que all the fluff about evaporating black holes, bacteria et al in the article.

The article is not very consistent in the usage of the term "black hole", using it to refer to both the "standard" gravitational black holes, and the "mathematical" black hole structure shared between the former and a quark-gluon plasma.


-- memento mori

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#150 2005-04-05 11:53:03

Palomar
Member
From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Singularity - Black Holes, Gamma Rays, Magnetars, etc

http://www.universetoday.com/am/publish … ]Starburst galaxies hide BH's

*A study involving Hubble.  Starburst galaxies create, on average, 50 times more stars than regular galaxies.  Some of the galaxies in this study are 6 billion light years away.  Each starburst region can be tens of thousands of l/y in diameter.

The radio search took place in an area known as the Hubble Space Telescope Deep Field North - a patch of sky smaller than the full Moon that contains tens of thousands of galaxies

Astronomers from the UK think these regions could also be the home to black holes. The team looked at Hubble images of these star-forming regions, and compared them to X-ray images of the same locations and found the telltale signs for both star formation and black holes.

More stars should equal more "stellar" (at least -- and as contrasted with galactic and middle-weight) black holes, right? 

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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