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ToSeek
2003-May-21, 12:01 AM
Third-closest star discovered (http://www.gsfc.nasa.gov/topstory/2003/0520newstar.html?JServSessionIdr005=kvws8ktb75.app 13b)

At least if you count the Alpha Centauri system as one (#2 is Barnard's Star).

informant
2003-May-21, 08:53 AM
OMG! :o
Look at that first picture - Nancy was right!
Run for your lives. (http://www.comicspage.com/comicspage/main.jsp?catid=1148&custid=69&file=20030416csbhl-a-p.jpg&code=csbhl&dir=/broomhilda)

gethen
2003-May-21, 01:12 PM
SO253000..5+165258?????? So near a neighbor certainly deserves a more personal name, doesn't it? Is someone or some agency likely to give it a name that's not such a mouthful? Whose job is that?

Glom
2003-May-21, 01:17 PM
How about Barry?

informant
2003-May-21, 01:45 PM
Or Fido?

gethen
2003-May-21, 02:58 PM
Well when I suggested Larry as an alternate name for our moon on another thread it was not widely hailed as a good choice, so I suspect Barry and Fido will probably not gain popular acclaim either. :wink:

g99
2003-May-21, 05:58 PM
[big booming voice] Bob! [/big booming voice]

Squink
2003-May-21, 11:43 PM
The unlabeled picture of the stellar disk is an artist's rendition, not a photograph.
Here's a more detailed article: Newly-discovered star may be third-closest to us (http://www.spaceflightnow.com/news/n0305/20closestar/)

carolyn
2003-May-22, 06:10 PM
Hey! noticed this.........

Jane Platt
NASA Jet Propulsion Laboratory

Any relation Phil ?

RichField
2003-May-22, 06:24 PM
Hey! noticed this.........

Jane Platt
Any relation Phil ?

Considering they pronounce and spell their names differently, I would say almost certainly :O

Actually, I have only have a guess that they're pronounced differently.

carolyn
2003-May-22, 09:08 PM
Oh yeh, :oops: put it down to being nearly friday! how silly do I feel!!!!!!!!!!!!!!!!!!!!!!!!

tracer
2003-May-30, 07:52 AM
From both articles:

The new star has only about seven percent of the mass of the Sun, and it is 300,000 times fainter.
:o Holy Farking Snit, that's dim! :o

In fact, that's the intrinsically dimmest star I've ever heard of. Wolf 359, which used to hold the record as far as I know, is a glaring 50,000 times dimmer than the sun. This new star is six times dimmer than that, if the trigonometric parallax measurements of it are anywhere near accurate.

If stars this dim are peppering interstellar space, we may have severely underestimated the number of red dwarfs there are in the galaxy. This could go a long way toward explaining the missing mass!

beskeptical
2003-May-30, 08:19 AM
From both articles:

The new star has only about seven percent of the mass of the Sun, and it is 300,000 times fainter.
If stars this dim are peppering interstellar space, we may have severely underestimated the number of red dwarfs there are in the galaxy. This could go a long way toward explaining the missing mass!

I am of the understanding dust and other normal matter that isn't visible such as planets and dim stars and black holes do not account for the dark matter.

Why this is known will have to be explained by those more knowledgeable. I'm afraid I would not explain it well enough to pass for understanding it.

nebularain
2003-May-30, 01:54 PM
Not an expert, either, but my guess would be the fact that there is a boatload more mass in Dark Matter than visible matter, as has been calculated (something like over 90% - 98% of the universe's mass is Dark Matter?), and there is now way dust, black holes, red dwarfs, etc. can account for that much mass.

My guess, anyway.

tracer
2003-May-30, 06:01 PM
Despite weighing in at around a tenth of the sun's mass (on average), a typical red dwarf produces less than 1/10,000 of the sun's visible light. That's a mass-to-luminosity ratio 1000 times that of the sun.

The light put out by our galaxy as a whole approximates the spectrum one would expect from a G-type (sunlike) star. Our calculations of how much visible (non-dark) matter there is in the galaxy are based on this overall color, and on how bright the galaxy is. But how do you determine how much of this light is being contributed by stars with a low mass-to-luminosity ratio, like Sirius, and how much is being contributed by stars with a high mass-to-luminosity ratio, like red dwarfs?

A tiny error in our estimate of how much of the galaxy's light is being contributed by red dwarfs will produce a huge error in our estimate of the amount of visible matter in the galaxy, because the mass-to-luminosity ratio of red dwarfs is so high.

So what I'm saying is, with the discovery of this new super-dim next-door-neighbor, our estimate of the amount of non-dark matter may be proven to be way off. Therefore, our estimate of what percentage of the galaxy's mass consists of dark matter (via our observations of the galaxy's rate of rotation) may be way too high.

Eric Carlson
2003-May-30, 06:13 PM
So what I'm saying is, with the discovery of this new super-dim next-door-neighbor, our estimate of the amount of non-dark matter may be proven to be way off. Therefore, our estimate of what percentage of the galaxy's mass consists of dark matter (via our observations of the galaxy's rate of rotation) may be way too high.

Well, this is a little complicated. I haven't heard about this new star, but presumably its simply a brown dwarf. We have a pretty good idea of how many brown dwarfs there are around because brown dwarfs radiate a fair amount of light in the infrared, so they aren't that hard to find using infrared telescopes. Based on such observations, brown dwarfs are a bit less common than stars. Since they are also a lot less massive, they don't contribute as much to the mass of a galaxy as stars do.

There are several other arguments, none of them particularly convincing. I won't run through them all, because they are, to me, not very convincing.

There are also arguments that the total amount of ordinary matter (includes anything that was originally made from atoms) cannot correspond to the total amount of matter. This is based mostly on calculations of the amount of Helium that would have been produced in the Big Bang. Finally, there are models of how the cosmic microwave background would have evolved as it went through clouds of ordinar matter (which can absorb light) and dark matter (which cannot). These are consistent with the primordial nucleosynthesis calculations. Roughly speaking, the answer is that there can't be enough ordinary matter to account for all the mass in galaxies.

dgruss23
2003-May-30, 07:14 PM
Eric Carlson wrote:
There are also arguments that the total amount of ordinary matter (includes anything that was originally made from atoms) cannot correspond to the total amount of matter. This is based mostly on calculations of the amount of Helium that would have been produced in the Big Bang.

So it is important to note that since the amount of baryonic dark matter in the universe is yet to be determined, the census of baryonic dark matter provides an important test of the Big Bang model.


Finally, there are models of how the cosmic microwave background would have evolved as it went through clouds of ordinar matter (which can absorb light) and dark matter (which cannot). These are consistent with the primordial nucleosynthesis calculations. Roughly speaking, the answer is that there can't be enough ordinary matter to account for all the mass in galaxies.

This thread (http://www.badastronomy.com/phpBB/viewtopic.php?t=5133) outlines some preliminary evidence that baryonic dark matter could make up a significant portion of the dark matter in galaxies.

Eric Carlson
2003-May-30, 07:24 PM
So it is important to note that since the amount of baryonic dark matter in the universe is yet to be determined, the census of baryonic dark matter provides an important test of the Big Bang model.

Yes, it does provide an important test. Though I consider the Big Bang proven, and therefore, the conclusion is inescapable.



This thread (http://www.badastronomy.com/phpBB/viewtopic.php?t=5133) outlines some preliminary evidence that baryonic dark matter could make up a significant portion of the dark matter in galaxies.

It is possible, if you go through enough contortions, to conclude that a significant portion of the matter in galaxies could be in the form of ordinary matter. But notice how many things have to be postulated to make this work. It has to be molecular, it has to be clustered on a certain scale, etc.

I would like to note that the big bang model predicted, in advance, such things as the spectrum of temperature fluctuations in the microwave background, the time dilation of type Ia supernovas. Alternative theories claim that they COULD predict such things in advance, but they actually didn't, to my knowledge.

tracer
2003-May-30, 08:16 PM
I haven't heard about this new star, but presumably its simply a brown dwarf.
Nope -- our new buddy SO25300.5+165258 is spectral class M6.5. At the lower end of red-dwarfsville, sure, but still within the outskirts of that town.


We have a pretty good idea of how many brown dwarfs there are around because brown dwarfs radiate a fair amount of light in the infrared, so they aren't that hard to find using infrared telescopes. Based on such observations, brown dwarfs are a bit less common than stars.
Are you kiddin'? Brown dwarfs are exceedingly difficult to find. Although the majority of their light output is in the infrared, they are still much more intrinsically dim in the infrared than even the coolest red dwarf star (let alone all those other hot stars out there). The reason we haven't found more than a handful of brown dwarfs thus far is because they're hard to pick out from among all the intrinsically-brighter-but-farther-away background stars, not because they're uncommon.

dgruss23
2003-May-30, 08:33 PM
Eric Carlson wrote: Yes, it does provide an important test.

We’re in agreement here. :D


Though I consider the Big Bang proven, and therefore, the conclusion is inescapable.

I personally would never go so far as to say “proven” and “inescapable”. Theories should always be subject to further testing and verification or refutation.


It is possible, if you go through enough contortions, to conclude that a significant portion of the matter in galaxies could be in the form of ordinary matter. But notice how many things have to be postulated to make this work. It has to be molecular, it has to be clustered on a certain scale, etc.

But remember its a hypothesis: The dark matter content of spiral galaxies is entirely baryonic. This is a statement that can be tested. The requirements you call “contortions” are there for reasons. The Pfenniger et al reference outlines the reasons it has to be molecular gas. As to the clustering scale - observations again play a role – as does the stability of gas clouds. So researchers that are looking into the matter(pun not intended) have concluded that IF the dark matter is baryonic, then the current observations leave these possible forms. This is a classic example of the process of science in action – eliminating options that would be inconsistent with available data and evaluating those that still remain.


I would like to note that the big bang model predicted, in advance, such things as the spectrum of temperature fluctuations in the microwave background, the time dilation of type Ia supernovas.

Did the Big Bang PREDICT the existence of dark matter, inflation, and dark energy? In fact, the Big Bang has many possible versions and much of what is going on with the WMAP results is an attempt to see which version of the Big Bang can be fitted best to the WMAP results. Here (http://xxx.lanl.gov/abs/astro-ph/0304237) is an example. So the Big Bang has its predictive successes, but it also has its "contortions" to fit the data.


Alternative theories claim that they COULD predict such things in advance, but they actually didn't, to my knowledge.

And how can they? Any new model that comes along will not be able to “predict” that which has already been observed. But alternatives should be able to make testable predictions or they are of no value.

Just to avoid confusion, it should also be noted in the context of these comments that baryonic dark matter as an explanation for the dark matter is not a theory any more than the microwave background is a theory. It’s a hypothesis. If observations demonstrate that the dark matter is entirely baryonic – or even baryonic in amounts that are not consistent with the current concordance model for the Big Bang, that does not mean that we have a new “baryonic dark matter” theory. We would then be looking for an alternative that would be consistent with the large amounts of baryonic dark matter.

tracer
2003-May-31, 06:22 AM
What does the "SO" in SO25300.5+165258 stand for? (I assume it's the abbreviation of some standard or semi-standard stellar catalog, but I don't know of any one place you can go to look all the catalog abbreviations up.)