Topic: How common is the Sun?

[Astronuc]

Yesterday, I was listening to a radio program, which discussed the sun and other stars like it.  It was mentioned that stars like the Sun represent about 4% of stars in our galaxy and those exactly like the Sun would be a much smaller percentage of course.  It would seem though that the sun if fairly unique, and the Solar System rather rare.

Anyway, I've been trying to find the program, which I think was on Stardate.org.  So far, no such luck.

Meanwhile, I have discovered various lists or catalogs of closest stars or similar stars.

From Known Space - http://www.jimloy.com/astro/known.htm

[Astronuc]

Found it - The Sun has a Twin!

Astronomers have identified a yellow star they say is the best twin to our own sun yet seen. In other words, it's a star that's almost identical to the sun. And that's interesting because our sun shines on a life-bearing planet.

But stars like the sun are rare, according to astronomers. They account for only 4 percent of all stars in our Milky Way galaxy. And stars exactly like our sun must be even more rare. Scientists reported the previously best known example - a star named 18 Scorpii - ten years ago.

Now Jorge Melendez at Mount Stromlo Observatory in Australia and Ivan Ramirez at the University of Texas at Austin say they've found an even better solar twin. Its name is HD 101364. It is 220 light-years from Earth.

These astronomers say the star's mass, temperature, and chemical composition appear to match the sun's exactly. But the star may emit slightly more light than our sun. Since sun-like stars brighten as they age, this suggests the star may be a billion years older than our sun.

But that difference might actually be good news for extraterrestrial life seekers. It means an orbiting planet has had even more time to give rise to life than Earth has.

 from http://www.earthsky.org/radioshows/51873/the-sun-has-a-twin

The star that is the sun's new twin - HD 101364 - also has the name HIP 56948.

  :koala

http://arxiv.org/abs/0709.4290 - HIP 56948: A Solar Twin With a Low Lithium Abundance

http://kencroswell.com/HD98618.html

http://kencroswell.com/18scorpii.html

[Astronuc]

Some background on Jorge Melendez and his work on stars similar to the sun

http://msowww.anu.edu.au/~jorge/profesion.htm

Research Fellow at the Research School of Astronomy and Astrophysics (Australian National University). He received his undergraduate degree in physics from the Universidad Nacional Mayor de San Marcos (Peru), the oldest university in the Americas. He obtained his PhD in astronomy at the Universidade de Sao Paulo, gathering the most complete list of atomic data for spectral synthesis in the infrared, and for further work on population synthesis. During the PhD Melendez also obtained oxygen abundances from infrared OH lines, showing that [O/Fe] is ~ constant in halo stars. Working with B. Barbuy, they obtained beautiful IR spectra of extremely high S/N, in order to detect tiny IR-OH lines at metallicities as low as [Fe/H] = -3. Another important study done with B. Barbuy was the determination of chemical abundances in giants of the Bulge Globular Cluster NGC 6553.[/color]

Melendez spent two years (2003-2005) at Caltech working with J. Cohen on abundance variations in GC stars, and on a survey for finding the oldest stars in the MW Galaxy. During his time in Pasadena he also collaborated with I. Ramirez (U. Texas) on the calibration of the fundamental properties of FGK stars. Their new IRFM temperature scale (Ramirez & Melendez 2005a,b) has been applied to the determination of lithium and oxygen abundances in metal-poor stars, a work with important implications on Big Bang Nucleosynthesis and the evolution of the light elements.

Since Sept/2005 Melendez has been working with M. Asplund (RSAA, ANU), and his main interests are the physical (e.g. temperature, mass, luminosity, radius) and chemical properties (e.g. iron, carbon, oxygen, lithium) of cool (FGK) stars, the evolution of the Chemical Elements in the Universe, the discovery of solar twins, and the fundamental properties of possible host stars of habitable systems in our Galaxy.

[/color]

[Astronuc]

delta Pavonis - spectral class: G6-8IV

B-V-magnitude	0,76
U-B-magnitude	0,45
R-I-magnitude	0,34

note (category: spectra):

Metal rich star with normal Doppler broadening.

http://www.alcyone.de/SIT/mainstars/SIT000654.htm
 

Emissions from the transition regions and coronae of three cool dwarf stars
http://adsabs.harvard.edu/abs/1983A&A...119..243F
 

Solar-Like Oscillations In beta Centauri

http://arxiv.org/PS_cache/astro-ph/pdf/0508/0508609v1.pdf

[Qazaq2003]

HIP 56948, Sol's twin, is located between the bowl of the Big Dipper in Ursa Major, and the tail of Draco, and shines at about magnitude 9.