Why isnt black holes, just black stars?

[ocoini]

So I was thinking about the universe, and everything.. 42..! And jumped around from site to site reading and looking at pictures. I started off at our solar system, oort cloud and kuiper belt, made my way to other galaxies, then back to our sun. And I learned about this and that. But I eventually made my way to understanding why our sun has a yellow glow, and howcome other stars shine with different colors.

So black holes pop into my head, i hate thoose.. and then I was thinking that, hey, maybe black holes are just black starsystems that are very "clouded" or something. cus... i really don't like the idea of a black hole.. So I googled that aswell.. but ofcourse, it's not something new ;D what is?

But all I found was this tiny article, ridiculeing MY idea! (ofcourse not first ^_^) http://arxiv.org/abs/0707.2450

At a quick glance I can't find any more explenation about why this doesnt compute. And im about to go to bed, so i registered here and maybe someone want to explain to me

Why black holes can't just be Black Stars?

I hate black holes... and asteroids... and anything moveing things about in general..

[Disinfo Agent]

Black holes are not stars because they don't glow.

[Sam5]

I doubt I can explain anything to a poster who admits that

1. he doesn't understand what astrophysicists mean by the term "black hole",

2. he hates the notion of a "black hole".

Many people do seem to hate that which they do not understand, simply because they do not understand it, but that's certainly not a promising starting point for any discussion of modern physics.

I think maybe some of these people might be high school or even junior high school people who haven’t yet developed a “sophisticated” way of conversing about astronomy yet, and who are not familiar with technical terminology.

When I studied astronomy in Junior High school back in the mid-1950s, the term “black hole” was not used in popular astronomy books. I have a 1959 university astronomy textbook here that doesn’t use the term. It uses the term “black dwarf”.

Back then the popular astronomy books used the term “dark star”, “black star”, or “black dwarf”. I think the term “black hole” didn’t become popular until maybe the ‘60s or ‘70s, and I don’t think it is appropriate to call them “holes”. They are not “holes in space”, and I think the term “dark star” is more appropriate.

[Trocisp]

I don't believe it would be considered a star, because stars are... uh... you know, fusing elements at their core, and Black Holes have... well.... who knows, but singularities I think at their cores.

[Sam5]

I don't believe it would be considered a star, because stars are... uh... you know, fusing elements at their core, and Black Holes have... well.... who knows, but singularities I think at their cores.

How about a “black ex-star”. Or a “black former star”. As opposed to a “planet”, “comet”, “asteroid”, etc.

[BigDon]

The object formally known as a star?

[pzkpfw]

...maybe black holes are just black starsystems that are very "clouded" or something.

I believe the possibility of a black hole was proposed before the observation of one occured^*.

That is, astronomers didn't see some dark space and make up a reason for it; first came the idea that an object could have strong enough gravity to not even let light out.

Thus your alternative idea doesn't really stand. Sorry.




(^* Has it?)

[Sam5]

The object formally known as a star?

Lol, yes.

[Chunky]

So I was thinking about the universe, and everything.. 42..! And jumped around from site to site reading and looking at pictures. I started off at our solar system, oort cloud and kuiper belt, made my way to other galaxies, then back to our sun. And I learned about this and that. But I eventually made my way to understanding why our sun has a yellow glow, and howcome other stars shine with different colors.

So black holes pop into my head, i hate thoose.. and then I was thinking that, hey, maybe black holes are just black starsystems that are very "clouded" or something. cus... i really don't like the idea of a black hole.. So I googled that aswell.. but ofcourse, it's not something new ;D what is?

But all I found was this tiny article, ridiculeing MY idea! (ofcourse not first ^_^) http://arxiv.org/abs/0707.2450

At a quick glance I can't find any more explenation about why this doesnt compute. And im about to go to bed, so i registered here and maybe someone want to explain to me

Why black holes can't just be Black Stars?

I hate black holes... and asteroids... and anything moveing things about in general..

i think your gonna be known as me around here.

good luck though

[Jeff Root]

It hadn't occurred to me that the title of the movie "Dark Star" might
mean exactly the same as "black hole". Does anyone know or want to
opine that that is what was meant?

Oh, I see in "Black Holes & Time Warps" that the term "dark star" was
apparently used circa 1783 by John Michell to describe the Newtonian
equivalent of a black hole.

I'd say that "black hole" means "place of overwhelmingly strong gravity".

John Wheeler coined the term "black hole" in 1967. See page 256 of
"Black Holes & Time Warps".

-- Jeff, in Minneapolis

[Trocisp]

How about a “black ex-star”. Or a “black former star”. As opposed to a “planet”, “comet”, “asteroid”, etc.

Not all black holes were former stars....

[darkday123]

How about a “black ex-star”. Or a “black former star”. As opposed to a “planet”, “comet”, “asteroid”, etc.

What if some asteroids crash together and become a black hole without ever becoming a star?

[Durakken]

What the hell are some of you smoking...

#1. A star doesn't need to "shine" to be classified as a star... There are a number of stars out there that give out only non-visible light and are planet like. I forget the official terminology for what a star is, but I know it isn't an object that "shines." It's similar to that.

#2. A star that gives off non-visible light is called a dark star...

#3. Black holes are so called because you can not seem them and things can "fall in"...We call the absence of "light" black and things we fall into a hole so therefor it's a friggin black hole.

#4. Black Holes as faras I have heard can only be created under man made conditions OR from a collapsing star. There is simply not enough matter in anything else to cause a black hole naturally, though i assume it is possible if you can tip the scale which causes it in stars where gravity causes an implosion rather than giving way to an explosion.

[Trocisp]

Black Holes as faras I have heard can only be created under man made conditions OR from a collapsing star.

http://en.wikipedia.org/wiki/Primordial_black_hole

[Durakken]

Those conditions no longer exist. Read the rest of what comes after that quote. The "primordial black hole" needs high density universe which we no longer have. There for the only thing that is dense enough currently known is a star.

[tommac]

I think it becomes a black hole at the point when the gravity is so strong that it pulls back space time at a speed faster than light.

[jokergirl]

It's not pining, it's passed on. This star is no more. It has ceased to be. It's expired and gone to meet its maker. This is a late star. It's a stiff. Bereft of life, it rests in peace. If you hadn't nailed it to the universe, it would be pushing up the daisies in another. Its metabolic processes are now of interest only to astronomers! He's off the twig! He's kicked the bucket, he's shuffled off his mortal coil, run down the curtain and joined the choir invisible! This is an ex-star!

[astromark]

' No Captain we should not go to close to that strong gravity field. It might be a_________________________________________________ __________________________________________________ __________________________________________________ ______________________________ Oops !

I like that Jokergirl... Where did it come from? other than the Parrot thing.? Mark.

[sabianq]

hi all,
I thought i would chime in here.
I think the concept of the Black Hole (not a reference to my ex girlfriend) is very beautiful in nature. the very basic concept is (from what i understand the theory to be) since according to relativity, spacetime is deformed by mass. the actual geometry of space time is influenced by matter. so when you get enough mass (material) in one spot, you create a "dimple" in the "fabric" of space time. like a star or planet. this "dimple" causes other matter to be attracted to it. kind of like when you place a bowling ball on a trampoline, you get an indentation, then when you put a marble on the trampoline, the marble rolls to the bowling ball because of the shape of the surface of the trampoline is distorted by the weight of the bowling ball.
This is how gravity works according to our best guess.

So what the heck is a black hole?

Well, this is what mainstream thinks:

Objects as big as the planets and stars make big dents in spacetime.
and when a star gets really really big, its gravity is so strong that the internal pressure form its core cannot sustain its size anymore, so it crushes in on itself. if the star is only so big, it becomes a neutron star, that is where the very body of the star is compact superdense matter, we think it may just be neutrons and protons in the core, but we really dont understand them.
(interesting thought tangent, maybe a neutron star can be though of as a massive element)
a neutron star can have the same mass of our sun but be only 10 or so miles in diameter, so you can see how this would put a big dent in speace time.

yea, yea, what about a black hole?

ok, when a star that is 5 or more times bigger than our sun collapses in on itself, it doesn't stop collapsing when the protons and neutrons collide, it keeps going, the matter becomes so small and so dense that the very core becomes a singularity. some people think it may be a rip in the very fabric of space time, some people think the core is just a super duper dense strange object, regardless of what it is, the gravity is so strong that even light cannot escape when if it enters its event horizon.
the event horizon is a boundary in physics where an event that happens cannot effect an outside observer.
Black holes do not "suck" light into them, Gravity cannot travel faster than the speed of light, however, the escape velocity needed to overcome the gravational field can be equal to the speed of light. If light is generated inside the event horizon, it cannot escape, and if light is directed toward it, it will not reflect back or travel through the other side.
Actually, Black holes are paradoxically the brightest objects in the universe, as matter passes though the event horizon, it heats up and emits x and gamma rays, the light emitted outside the event horizon does indeed make its way to our observatories.

There are a class of stars that do not emit light in the visible light range that could also be considered "black" but they already have a name and they are called "brown dwarfs" they emit light in the low energy side of the spectrum, infrared and radio.

hope this helps

[sabianq]

Not all black holes were former stars....

ah.. but Michael Jackson was a former black star.

sorry, could not resist.

[Sam5]

There are a class of stars that do not emit light in the visible light range that could also be considered "black" but they already have a name and they are called "brown dwarfs" they emit light in the low energy side of the spectrum, infrared and radio.

Stars that emit no visible light but that do emit radio waves are known as “radio stars”.

A very young one could be called a “child star”.

Ones that evolve through several stages are called “stage stars”.

[John Mendenhall]

' No Captain we should not go to close to that strong gravity field. It might be a_________________________________________________ __________________________________________________ __________________________________________________ ______________________________ Oops !

Astro, you're fading fast . . .

[John Mendenhall]

I believe the possibility of a black hole was proposed before the observation of one occured^*.

That is, astronomers didn't see some dark space and make up a reason for it; first came the idea that an object could have strong enough gravity to not even let light out.

Thus your alternative idea doesn't really stand. Sorry.

(^* Has it?)

As far as I know, there are no direct observations, yet. The radio telescope folks are close to having enough resolution.

There are objects (SMBH) for which no other reasonable explanations exist, but even they are too small to observe directly.

[Trocisp]

Those conditions no longer exist. Read the rest of what comes after that quote. The "primordial black hole" needs high density universe which we no longer have. There for the only thing that is dense enough currently known is a star.

Yes, but the black holes could still be around.

[jokergirl]

I like that Jokergirl... Where did it come from? other than the Parrot thing.? Mark.

Just came from me. I thought the quote tag was appropriate.

[sabianq]

Stars that emit no visible light but that do emit radio waves are known as “radio stars”.

brown dwarfs are radio stars, I don't think "radio star" is a real classification
http://www.nature.com/nature/journal.../410310a0.html
http://www.sciencedaily.com/releases...0419111759.htm
http://www.nrao.edu/pr/2001/browndwarf/
http://www.ncbi.nlm.nih.gov/pubmed/11268184
http://news.bbc.co.uk/2/hi/science/nature/6574433.stm

A very young one could be called a “child star”.

star classifications are already documented and the term "child star" really is not considered mainstream.

you have:
DWARF STARS
yellow red and brown

Giant and Supergiant Stars - Old, Large Stars
blue giant
red super giant

Faint, Virtually Dead Stars
white
brown dwarf
neutron
and pulsar


Binary Stars:
double star
and binary star

and
CEPHEID VARIABLE STARS

Ones that evolve through several stages are called “stage stars”.

all stars go through several stages but i don't think that a "stage star" is a term used in mainstream Cosmology.

maybe on Amerikan Idol

[Tim Thompson]

... i really don't like the idea of a black hole .. But all I found was this tiny article, ridiculeing MY idea! ...

News from the front: There is a real world outside of yourself which is not obliged to behave in accordance with your likes & dislikes, nor mine either.

... so i registered here and maybe someone want to explain to me Why black holes can't just be Black Stars?

You might as well ask, Why can't mice be elephants?. The boring but insightful answer is, because they aren't.

I hate black holes ... and asteroids ... and anything moveing things about in general ..

Zeno didn't like the idea of motion either. But we have actually learned one or two things in the last 2400 or so years.

What if some asteroids crash together and become a black hole without ever becoming a star?

The largest of the main belt asteroids is Ceres, which weighs in at 8.7x10²⁰ kg, and by itself carries about 1/3 of the total mass of the entire asteroid belt. It would take about 2,286,000,000 Ceres size asteroids to add up to one solar mass. And of course, smashing asteroids together releases a lot of energy long before you get anything like black hole mass, and all that energy has to go somewhere & do something. So I think we can all agree that this is unlikely to happen around here any time soon.

#1. A star doesn't need to "shine" to be classified as a star ... #2. A star that gives off non-visible light is called a dark star ...

As far as I know, all "ordinary" stars always shine and always emit visible light. However, you might not see the light if the star is enshrouded in dust. In 2004 the Spitzer Space Telescope discovered an entire cluster of stars (GLIMPSE C01, Kobulnicky, et al., 2005) hidden behind so much dust nobody had seen them before.

Also, I have never heard the term "dark star" used in this context. I do recall that when I was young, the term "black dwarf' was used to describe a white dwarf which had cooled off completely. Nobody uses the term "black dwarf" anymore because we now know that white dwarfs cool so slowly that the universe is not yet old enough for any "black dwarfs" to exist. You might be thinking of "brown dwarf", which is too big to be a planet but too small to be a star. A brown dwarf will be between about 13 and 80 Jupiter masses.

There are a class of stars that do not emit light in the visible light range ... and they are called "brown dwarfs" ...

Brown dwarfs do emit light in the visible range, they are just hard to see because they are relatively dim and relatively far away.

I believe the possibility of a black hole was proposed before the observation of one occurred ...

As far as I know, there are no direct observations, yet.

Pzkpfw is correct on the timing. Karl Schwarzschild developed the first black hole solutions to Einstein's equations in 1915, the same year they were first published, and long before anyone claimed any kind of observational support for the concept. As I recall, the first observed object that appeared to fit the requirements to be a black hole was Cygnus X-1, discovered in the 1960's and suspected as a black hole in the 1970's.

I think it is fair to say that there is direct evidence. One example is something I have pointed out before, namely the difference between a hard solid surface that any compact object, except a black hole, must have, and the peculiar event horizon of a black hole. There is observational evidence for this difference. From another thread earlier this year ...

Finally, I will point out that solid surfaces & event horizons are observationally distinguishable, one from the other. Material that falls on a solid surface behaves differently from material that falls on an event horizon. This difference can be used to observationally infer the presence of an event horizon around a compact object, and therefore observationally distinguish between solid objects and black holes in candidate objects. This has been done, and it is fair to say that we have observationally segregated black holes from non black holes in a few cases (i.e., Remillard, et al., 2006; Done & Gierlinski, 2003; Paul, et al., 1998).

Another interesting observational trick is found in Shen, et al., 2005, where the authors use very long baseline interferometry at radio wavelengths to image the general relativistic shadow of the supermassive black hole at the center of the milky Way. The black hole itself is not quite resolved, but the space around it is, and the effect observed is as predicted if there is an event horizon present.

[John Mendenhall]

News from the front: There is a real world outside of yourself which is not obliged to behave in accordance with your likes & dislikes, nor mine either.

I think it is fair to say that there is direct evidence.

Agreed and agreed.

[zerocold]

Really quantum physics allows the existence of BHs?, im not an expert on that matter, but QFs dont tell that there is a minimal time-space-energy fraction? meaning that mass cant be shrinked below these limits?

Is'nt that explanation simpler and better than the "infinite time" vs "hawking radiation" theory?

I also have heard the "cold star" term

[loglo]

The object formally known as a star?

Thats Prince isn't?

Hey! Didn't he have a name like that at one point??