PDA

View Full Version : Hip 11952



DesertFox
2012-Oct-16, 09:12 PM
Hoping that somebody might be able to help with this
HIP 11952 is the Population II star recently in the news because it has planets orbiting around it.

HIP 11952 is listed as a F2 class star.
To me, that means a star larger than the sun with a lifespan of around 3 billion years
According to articles on the star, it is suppose to be around 12.7 billion years old

Checking the mass, it is listed as being around 0.85 that of the sun.
That means to me a K class star with a lifespan of 15 billion years or so.

A third problem is that the star's diameter is listed as 1.6 solar radius which does not fit with a star that is only 0.85 that of the sun

Anybody have an explanation?

antoniseb
2012-Oct-16, 09:54 PM
I didn't look anything up, but the likely case is that this is an evolved K star that is now approaching the giant branch as it slides up the HR diagram.

grant hutchison
2012-Oct-16, 10:18 PM
The discovery paper is here (http://arxiv.org/abs/1208.4000), and contains quite a lot of discussion about the star itself. As antoniseb deduced, it seems to be evolving off the Main Sequence - hence its departure from the usual Main Sequence parameters.

Grant Hutchison

DesertFox
2012-Oct-16, 11:00 PM
The sad this is that I suggested exactly that on another forum and was called an idiot
My thought was that it the star was probably originally a G class star which in the process of its burning lost about 30% of its mass while at the same time brightening.
As far as why it is old for a G class star, population Ii class stars are suppose to burn less brightly / cooler

antoniseb
2012-Oct-16, 11:52 PM
The sad this is that I suggested exactly that on another forum and was called an idiot ...
Because you are new, no penalty... but as a heads up, we avoid discussing other forums, and don't bring baggage from them. You're welcome here. I'm sure you'll fit in nicely.

DesertFox
2012-Oct-17, 01:51 AM
Sorry about that then. . .Still glad to know that my thoughts were probably on the right track at least

Wonder how much being low metal might extend the life span of a Population II star compared to a Population I star of the same class?
Would it be significant?

StupendousMan
2012-Oct-17, 02:33 AM
Wonder how much being low metal might extend the life span of a Population II star compared to a Population I star of the same class?
Would it be significant?

I don't know, but if I used the MESA stellar evolution code

http://mesa.sourceforge.net/

I could find out. Or maybe you could. Why not give it a try?

grant hutchison
2012-Oct-17, 11:32 AM
The Extrasolar Planet Encyclopaedia (http://exoplanet.eu/catalog) is generally useful if you're puzzled about an exoplanet or its star. It'll give you a link to relevant papers, and the authors of these papers can generally be relied upon to discuss any puzzling or unusual aspects of the planet and star.

Grant Hutchison

DesertFox
2012-Oct-17, 11:52 AM
That looks pretty damn complicated. . . .

StupendousMan
2012-Oct-17, 01:08 PM
I feel your pain. Some things are just pretty damn complicated. There's a story (related by Proclus) more than two thousand years old along these lines. Ptolemy Soter (the local king) took a few lessons in geometry. After a short time and many proofs, he asked if there were any easier ways to get to the answers. Euclid is reported to have replied, "There is no royal road to geometry."

This remains true in many sciences, including astronomy.

DesertFox
2012-Oct-17, 03:25 PM
Not saying that I could never learn the program but at the moment I don't know it. . . .
From reading the support documentation, I think you are expected to know areas that I just don't know

It is always funny when something is complicated when you first look at it but later becomes easy and you wonder why it was ever hard

How do you consider the planet to impact theories on planetary formation?

Romanus
2012-Oct-18, 12:23 AM
It's probably a combination of its being evolved (as others have already mentioned), and being a subdwarf (which would appear "earlier" and hotter than a Pop I star of the same mass even on the MS).

galacsi
2012-Oct-18, 10:17 AM
It's probably a combination of its being evolved (as others have already mentioned), and being a subdwarf (which would appear "earlier" and hotter than a Pop I star of the same mass even on the MS).

Yes probably an evolved star, it is the opinion of Wikipedia ( http://en.wikipedia.org/wiki/HIP_11952 ), but what is strange is that it is now a F2. Does that means it started as a A star ? With a mass 0.85 ofthe sun ? Hum . . . something wrong here.:confused:

DesertFox
2012-Oct-18, 09:33 PM
0.85 is between a G5 and a K0 in mass
My understand though is that our sun will have lost about 30% of its mass when it is near red giant stage

galacsi
2012-Oct-19, 12:17 PM
0.85 is between a G5 and a K0 in mass
My understand though is that our sun will have lost about 30% of its mass when it is near red giant stage

I am OK with that Desertfox, but when a star start becoming a giant ,I learnt it will become redder , hence the name red giant. However this star hip 11952 is a F2. I am lost here.

chornedsnorkack
2012-Oct-19, 02:12 PM
Faint young Sun was not only smaller, but colder than now. During main sequence and early subgiant evolution, a star brightens and expands but also gets hotter. It is only after the star has brightened to several times its original brightness that its expansion outstrips brightening and it starts cooling.

galacsi
2012-Oct-19, 05:06 PM
Faint young Sun was not only smaller, but colder than now. During main sequence and early subgiant evolution, a star brightens and expands but also gets hotter. It is only after the star has brightened to several times its original brightness that its expansion outstrips brightening and it starts cooling.

Thanks : It explains it all.

chornedsnorkack
2012-Oct-19, 05:37 PM
Thanks : It explains it all.

Not all.

Another part is that subdwarfs are hotter and smaller for the same mass and luminosity.

John Jaksich
2012-Oct-20, 01:41 AM
I don't know, but if I used the MESA stellar evolution code

http://mesa.sourceforge.net/

I could find out. Or maybe you could. Why not give it a try?

I have downloaded and installed the program; it took awhile. But, the installation kit which is an "add-on" did help.

I will let the forum know how program works?

PlutonianEmpire
2012-Oct-20, 03:58 AM
I feel your pain. Some things are just pretty damn complicated. There's a story (related by Proclus) more than two thousand years old along these lines. Ptolemy Soter (the local king) took a few lessons in geometry. After a short time and many proofs, he asked if there were any easier ways to get to the answers. Euclid is reported to have replied, "There is no royal road to geometry."

This remains true in many sciences, including astronomy.
Not always. :p

I learned of a basic(?) formula a while back for calculating binary star orbits, and found that the formula I was given seemed to be needlessly complicated (I could be wrong ;) ):

a1 = (a1 + a2) * m2/(m1 + m2)
a2 = (a1 + a2) * m1/(m1 + m2)

a = semi-major axis
m = mass
The formula above is good for an educational exercise, I guess, but what that translated into my mind was that it was just total semi-major axis (orbital separation) times the mass of a specified object divided by the combined masses of both objects.

Dunno if that counts towards anything. :lol:

John Jaksich
2012-Oct-22, 06:06 PM
I don't know, but if I used the MESA stellar evolution code

http://mesa.sourceforge.net/

I could find out. Or maybe you could. Why not give it a try?

As I stated previously---I did download and install the program. It works as described by the authors. There were a few minor tweaks in the script to get it to comply the initial test case. But, in one word it is "great." . . . so far. It also possesses the ability to graphically display the results which I have yet to master that aspect.

John Jaksich
2012-Nov-05, 12:17 PM
As I stated previously---I did download and install the program. It works as described by the authors. There were a few minor tweaks in the script to get it to comply the initial test case. But, in one word it is "great." . . . so far. It also possesses the ability to graphically display the results which I have yet to master that aspect.

I have been working through the test-suite of the program: MESA and did come across a plot --as I stated before, the program works very well and here is a screen shot of one in the test-suite:

17688


It is very unfortunate that I am not an expert on the subject ----but I am working my way into it as best that I can for the moment.

The developers took approximately 6 years to all of the components working and graphics were developed at Cal Tech. I think this is certainly a winner!

whimsyfree
2012-Nov-10, 03:18 AM
Not all.

Another part is that subdwarfs are hotter and smaller for the same mass and luminosity.

"Subdwarf" is ambiguous. (Unfortunately most astronomical terms have no consistent meaning.) You are correct that a main sequence star with HIP 11952's extremely low metallicity would be smaller and earlier than a "normal" main sequence star. However, Setiawan et al. give 1.6 Rsun for HIP 11952. That is one type of subdwarf. The other type of subdwarf is a post-giant star, but they are always referred to as O or B. Maybe the star is a subgiant subdwarf. It still seems anomalously early. pre-sdB is another idea.


My understand though is that our sun will have lost about 30% of its mass when it is near red giant stage

I don't believe so.

galacsi
2012-Nov-10, 05:35 PM
The Extrasolar Planet Encyclopaedia (http://exoplanet.eu/catalog) is generally useful if you're puzzled about an exoplanet or its star. It'll give you a link to relevant papers, and the authors of these papers can generally be relied upon to discuss any puzzling or unusual aspects of the planet and star.

Grant Hutchison

I just discovered your link. Wow ! I played with the diagrams and it is great fun (and instructive)

NEOWatcher
2012-Nov-12, 01:02 PM
My understand though is that our sun will have lost about 30% of its mass when it is near red giant stage
I don't believe so.
Why not (http://en.wikipedia.org/wiki/Red_giant#The_Sun_as_a_red_giant)?

However the results of studies announced in 2008 show that due to tidal interaction between Sun and Earth, Earth would actually fall back into a lower orbit, and get engulfed and incorporated inside the sun before the Sun reaches its largest size, despite the Sun losing about 38% of its mass.

whimsyfree
2012-Nov-14, 12:04 AM
Why not (http://en.wikipedia.org/wiki/Red_giant#The_Sun_as_a_red_giant)?

Because I haven't seen any references that assert that the Sun will lose that much mass on the main sequence or as a subgiant. Your links and quotes were not relevant to that point.

NEOWatcher
2012-Nov-14, 05:55 PM
Because I haven't seen any references that assert that the Sun will lose that much mass on the main sequence or as a subgiant. Your links and quotes were not relevant to that point.
To what point do you think I was referring to? The comment I responded to was your comment about losing mass going into red giant face.

I'm here to learn, and "I don't think so" doesn't teach me anything, so I tried doing my own research.

The way I read the wiki statement it says a similar thing. So; what am I reading wrong? Is wiki wrong?

whimsyfree
2012-Nov-14, 10:58 PM
To what point do you think I was referring to? The comment I responded to was your comment about losing mass going into red giant face.

I'm here to learn, and "I don't think so" doesn't teach me anything, so I tried doing my own research.

The way I read the wiki statement it says a similar thing. So; what am I reading wrong? Is wiki wrong?

Not AFAIK but I still don't see where it says the Sun will lose 30%+ of its mass before becoming a red giant. Considerable mass loss occurs during the red giant phase. I haven't seen any references that say it occurs before that.

NEOWatcher
2012-Nov-15, 01:03 PM
Not AFAIK but I still don't see where it says the Sun will lose 30%+ of its mass before becoming a red giant. Considerable mass loss occurs during the red giant phase. I haven't seen any references that say it occurs before that.
Then perhaps someone can chime in and clarify what's going on.

John Jaksich
2012-Nov-15, 02:17 PM
According to the following power law--from any standard text (I will cite appropriate references below) Radius ~ Mass^.7

Or in words---the radius of a solar body is proportional to the .7 of the stellar mass---there will be an approximate 30 % loss of total mass of the Sun as it grows to a Red Giant

The *on-line* reference which I pulled it from is here:www.astro.uni-bonn.de/~nlanger/siu_web/ssescript/.../chapter1-3.pdf

Here is the exact page and it can also be seen from the Hertzsrung-Russell diagram in the text (page 5)

or in short : L ∝ M 3.8 and R ∝ M 0.7


Other textbooks are:

C.J. Hansen, S.D. Kawaler & V. Trimble, Stellar Interiors, 2004, Springer-Verlag, ISBN 0-387-
20089-4 (H)


A. Maeder, Physics, Formation and Evolution of Rotating Stars, 2009, Springer-Verlag, ISBN
978-3-540-76948-4 (M)


M. Salaris & S. Cassisi, Evolution of Stars and Stellar Populations, 2005, John Wiley & Sons,
ISBN 0-470-09220-3 (S)

John Jaksich
2012-Nov-15, 03:09 PM
According to the following power law--from any standard text (I will cite appropriate references below) Radius ~ Mass^.7

Or in words---the radius of a solar body is proportional to the .7 of the stellar mass---there will be an approximate 30 % loss of total mass of the Sun as it grows to a Red Giant

The *on-line* reference which I pulled it from is here:www.astro.uni-bonn.de/~nlanger/siu_web/ssescript/.../chapter1-3.pdf

Here is the exact page and it can also be seen from the Hertzsrung-Russell diagram in the text (page 5)

or in short : L ∝ M 3.8 and R ∝ M 0.7


Other textbooks are:

C.J. Hansen, S.D. Kawaler & V. Trimble, Stellar Interiors, 2004, Springer-Verlag, ISBN 0-387-
20089-4 (H)


A. Maeder, Physics, Formation and Evolution of Rotating Stars, 2009, Springer-Verlag, ISBN
978-3-540-76948-4 (M)


M. Salaris & S. Cassisi, Evolution of Stars and Stellar Populations, 2005, John Wiley & Sons,
ISBN 0-470-09220-3 (S)

Apparently the *link* has collapsed---and according to wikipedia--->

" A red giant is a luminous giant star of low or intermediate mass (roughly 0.5–10 solar masses) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower. The appearance of the red giant is from yellow orange to red, including the spectral types K and M, but also class S stars and most carbon stars. . . . . However the results of studies announced in 2008 show that due to tidal interaction between Sun and Earth, Earth would actually fall back into a lower orbit, and get engulfed and incorporated inside the sun before the Sun reaches its largest size, despite the Sun losing about 38% of its mass."

I am sorry to see previous site get shuttered from my citation. . .

John Jaksich
2012-Nov-15, 05:37 PM
Let me try again (but this time with a H-R diagram):

17708

Credit is due to the University of Nebraska--Lincoln

Here is the link, if anyone is concerned:

http://astro.unl.edu/naap/hr/hr_background3.html


Using the previous relation: the math is fairly simple. (Our Sun is marked by a the red x--on the diagram)

whimsyfree
2012-Nov-15, 11:21 PM
According to the following power law--from any standard text (I will cite appropriate references below) Radius ~ Mass^.7

Or in words---the radius of a solar body is proportional to the .7 of the stellar mass---there will be an approximate 30 % loss of total mass of the Sun as it grows to a Red Giant

The *on-line* reference which I pulled it from is here:www.astro.uni-bonn.de/~nlanger/siu_web/ssescript/.../chapter1-3.pdf

Here is the exact page and it can also be seen from the Hertzsrung-Russell diagram in the text (page 5)

or in short : L ∝ M 3.8 and R ∝ M 0.7


Those relations are only rough guides and are applicable only to main sequence stars. How do they help explain HIP 11952?


Apparently the *link* has collapsed---and according to wikipedia--->

" A red giant is a luminous giant star of low or intermediate mass (roughly 0.5–10 solar masses) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower. The appearance of the red giant is from yellow orange to red, including the spectral types K and M, but also class S stars and most carbon stars. . . . . However the results of studies announced in 2008 show that due to tidal interaction between Sun and Earth, Earth would actually fall back into a lower orbit, and get engulfed and incorporated inside the sun before the Sun reaches its largest size, despite the Sun losing about 38% of its mass."

I am sorry to see previous site get shuttered from my citation. . .

That's interesting but what hypothesis concerning HIP 11952 is it relevant to?


Let me try again (but this time with a H-R diagram):

17708

Credit is due to the University of Nebraska--Lincoln

Here is the link, if anyone is concerned:

http://astro.unl.edu/naap/hr/hr_background3.html


Using the previous relation: the math is fairly simple.

What math? I don't see the what you are getting at with this series of posts.

John Jaksich
2012-Nov-16, 12:10 AM
Those relations are only rough guides and are applicable only to main sequence stars. How do they help explain HIP 11952?



That's interesting but what hypothesis concerning HIP 11952 is it relevant to?



What math? I don't see the what you are getting at with this series of posts.

Hi,

To at least it seems like a "back-of-the-envelope" computation-----

I am under the impression that the *current* question was about a main sequence star? Based on one of your previous posts:


Because I haven't seen any references that assert that the Sun will lose that much mass on the main sequence or as a subgiant. Your links and quotes were not relevant to that point.

My bold emphasis---to attempt to answer that question . . .


However, in the FIRST post---->

A third problem is that the star's diameter is listed as 1.6 solar radius which does not fit with a star that is only 0.85 that of the sun The quoted star is larger than 1 solar radius but has a .85 solar mass----> to me at least ----> it is an evolved star----as mentioned in a previous thread.


To give the my assertions more solid footing---I would need to compute it with the *downloaded software* that was mentioned earlier in the thread----. . . and I am still in the process of understanding it to my personal satisfaction. . . .

I can attempt to do a "full-blown" computation on my Debian workstation--if anyone wants to see the numbers?.

I am *sorry* if you believe that I attempted to lead you astray.

whimsyfree
2012-Nov-16, 01:53 AM
Hi,

To at least it seems like a "back-of-the-envelope" computation-----

I am under the impression that the *current* question was about a main sequence star? Based on one of your previous posts:



My bold emphasis---to attempt to answer that question . . .


No, the question I addressed was whether the Sun loses substantial mass in approaching red giant status. I don't believe that it will. It will lose a good deal of mass as an RGB star (about a third of its current mass, according to Schröder and Connon Smith (http://adsabs.harvard.edu/abs/2008MNRAS.386..155S)). That is mass loss that occurs as a red giant, not in "becoming" or "nearing" red giant status. To say that A is becoming or nearing status X is to say that it is not of status X.


However, in the FIRST post----> The quoted star is larger than 1 solar radius but has a .85 solar mass----> to me at least ----> it is an evolved star----as mentioned in a previous thread.


I'm not aware of a previous thread, sorry. Searching for HIP11952 and 11952 turns up only this thread.

In this thread the possibility that it is evolved has been discussed. The problem is finding a point where it fits. Obviously not RGB so if it is evolved it must be either a sub-giant or post-RGB. Where do you think it fits?

The given mass and radius could fit a pre-ZAMS star, but I don't know about the spectral class.

StupendousMan
2012-Nov-16, 12:23 PM
If you go to ADS

http://adsabs.harvard.edu/abstract_service.html

and type "HIP 11952" into the "Object Name" box, then press the "submit"
button, you'll be given a list of papers which mention the star.
The very first one was published earlier this year, and is available
in its full form on astro-ph.

I suggest you read Section 3 for a discussion of the measured parameters
for this star and hints to its evolutionary state.

ADS is a really useful resource. You could also go to SIMBAD

http://simbad.u-strasbg.fr/simbad/

and type the name of the star into the "search by identifier" box.
The returned page of information includes a set of "References"
to the literature, which includes this paper.

John Jaksich
2012-Nov-16, 03:50 PM
If you go to ADS

http://adsabs.harvard.edu/abstract_service.html

and type "HIP 11952" into the "Object Name" box, then press the "submit"
button, you'll be given a list of papers which mention the star.
The very first one was published earlier this year, and is available
in its full form on astro-ph.

I suggest you read Section 3 for a discussion of the measured parameters
for this star and hints to its evolutionary state.

ADS is a really useful resource. You could also go to SIMBAD

http://simbad.u-strasbg.fr/simbad/

and type the name of the star into the "search by identifier" box.
The returned page of information includes a set of "References"
to the literature, which includes this paper.


Thanks --I did not know of SIMBAD

whimsyfree
2012-Nov-17, 12:06 AM
If you go to ADS

http://adsabs.harvard.edu/abstract_service.html

and type "HIP 11952" into the "Object Name" box, then press the "submit"
button, you'll be given a list of papers which mention the star.
The very first one was published earlier this year, and is available
in its full form on astro-ph.


I get Setiawan et al. which is the same paper the I referred to in #23 above. They suggest it is a subgiant, as I did in #23 above. I was surprised at the F2 spectral class. They refer to Girardi et al. 2010 (http://iopscience.iop.org/0004-637X/724/2/1030) which, from the abstract, doesn't seem directly relevant. The also refer to Marigo et al. 2008 (http://adsabs.harvard.edu/abs/2007arXiv0711.4922M) which leads me to CMD 2.4 website (http://stev.oapd.inaf.it/cgi-bin/cmd_2.4). Playing around with that suggests subdwarfs can be really hot for their mass.