What percentage of stars are variable

Does anyone have good traceable estimates that would answer this ?
All classes
Visible to nakes eye or maybe in amateur telecopes.
Thanks
Zinc

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Pierre Vandevennne wrote:

"Zinc Potterman" . (delete 123's to reply)
wrote in :

Does anyone have good traceable estimates that would answer this ?
All classes
Visible to nakes eye or maybe in amateur telecopes.

By some definitions, virtually all of them, including our own sun are.

He's got a good point there -- if you look at them close enough, or long
enough, it's impossible to find a star that isn't variable. The
variability can arise from a wide range physical processes, from simple
oscillations, to giant eruptions, to carbon "soot" forming, to rotating
starspots.

So unfortunately your simple question presupposes a simple answer and
there (simply) isn't one...

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply have a physician remove your spleen

Zinc Potterman (delete 123's to reply) wrote:
Does anyone have good traceable estimates that would answer this ?
All classes. Visible to nake[d] eye or maybe in amateur telecopes.

There are 38,624 confirmed and suspected variable stars in the most
current general variable catalogue:

Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed. aka Samus
2004) Samus N.N., Durlevich O.V., et al.
http://cdsweb.u-strasbg.fr/cgi-bin/Cat?II/250

superceding the -

General Catalogue of Variable Stars, 4th Edition, Volumes I-III
(Kholopov+ 1988) Kholopov, P.N., Samus', N.N., Frolov, M.S., Goranskij,
V.P.,
http://cdsweb.u-strasbg.fr/cgi-bin/Cat?II/139B

These are the small fraction of the 27,198,952,706 estimated stars that
can be seen if your scope has an aperature that can reach down to
magnitude 20. If you telescope as a more realistic limiting magnitude
of let's say mag 16, you can see an estimated 379,844,556 stars.
http://www.stargazing.net/david/cons...manystars.html

As CeeBee notes, the exact limiting magnitude you can visualize depends
on the aperature of your scope and whether you are also using
astrophotography techniques. To find the visual (not photographic)
telescopic limiting magnitude of your scope or binoculars, use this
online calculator -
http://www.go.ednet.ns.ca/~larry/astro/maglimit.html

Of the 38,624 variables, the AAVSO www.aavso.org currently tracts
about 7782 variable stars in its master database. The AAVSO master
database can sorted for observation planning purposes using Patrick
Chevalley's VAROBS software -
http://www.astrosurf.org/astropc/varobs/index.html

The visible universe is currently estimated to contain 70 sextillion
stars - that's 70 thousand million million million.

http://www.abc.net.au/cgi-bin/common...ish_910295.htm


- Canopus56

"Space is big. You just won't believe how vastly, hugely,
mind-bogglingly big it is. I mean, you may think it's a long way down
the road to the drug store, but that's just peanuts to space."
The Hitchhiker's Guide to the Galaxy

Zinc Potterman wrote:
Does anyone have good traceable estimates that would answer this ?
All classes
Visible to nakes eye or maybe in amateur telecopes.

Perhaps if you explained why you are asking it would be easier to give
an appropriate answer. I mean, are you interested in how many stars in
our galaxy are variable, or haw many can be seen to vary in the scope or
to the eye? If the latter how variable is variable? And what do you
mean by traceable?

Note that the numerical answers you have gotten so far only include
those stars that have been given variable star designations for one
reason or another. This is not a representative sample overall.


--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply have a physician remove your spleen

Zinc Potterman (delete 123's to reply) wrote:

Does anyone have good traceable estimates that would answer this ?
All classes
Visible to nakes eye or maybe in amateur telecopes.

You can find a few statistics and good references to further
information in this article by Bohdan Paczynski: (the following URL
should be all on one line):

http://adsabs.harvard.edu/cgi-bin/np...b72b2327723032

If you can't read the full version of the paper, you can find a
preprint at

http://arxiv.org/abs/astro-ph/0005284

The short answer is: it depends on your definition of "variable".

Michael Richmond

Brian Tung knows.

Zinc Potterman wrote:

Does anyone have good traceable estimates that would answer this ?
All classes
Visible to nakes eye or maybe in amateur telecopes.
Thanks
Zinc

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zincnews123 at tiscali.c123o.u123k
To reply to address don't click.
Cut and paste, change at to symbol
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canopus56 wrote:
Zinc Potterman (delete 123's to reply) wrote:
Does anyone have good traceable estimates that would answer this ?
All classes. Visible to nake[d] eye or maybe in amateur telecopes.

P.S. -

Table 16.1 in Allen's _Astrophysical Quantities_ takes the GCVS (4th
Ed. 1988) and sums the known variables by type. It's available at most
university libraries.

You can do nearly the same thing as Table 16.1 by downloading the GCVS
and importing it into a spreadsheet. Then use the data analysis to sum
each type.

But Table 16.1 in _Astrophysical Quantities_ already has a good
organizational grouping the many variable types by major categories,
i.e. - eclipising binaries, cephids, flare stars, etc.

As Stupendous Man notes, over 90% of variables fainter than mag. 12
have not been surveyed, so extrapolating the ratios of totals in Table
16.1 and the GCVS would be questionable.

- Canopus56