Re: [Phys-L] stellar properties

[John Denker <jsd@av8n.com>]

On 01/25/2014 05:56 PM, Anthony Lapinski wrote:
> I also want data for the brightest
> stars, rather than the closest ones, as students are familiar with them.

Yeah, but a large dataset of reasonably nearby stars /contains/ all
the brightest ones, for obvious reasons.  Furthermore, if you want 
good distance/parallax data, you're stuck with the reasonably nearby 
ones for that reason also.  If you want /only/ the brightest ones, 
it's up to you to filter the dataset.

There's a lesson in that for the students:  Outside of fairy tales
(Cinderella meets Goldilocks) you essentially never find a dataset
that exactly fits your needs.
 *) Sometimes you can find some huge compendium, from which you
  can select the tidbits you need.
 *) Sometimes you can find two or more datasets that look at the
  elephant from different angles, and you can do a big join to
  get the whole picture.
       http://en.wikipedia.org/wiki/Join_(SQL)
 *) et cetera.


===================

Here's another source of data:

  http://heasarc.gsfc.nasa.gov/W3Browse/all/hipparcos.html
  The Hipparcos and Tycho Catalogues ...
  Each of the catalogues contains a large quantity of very high 
  quality astrometric and photometric data. In addition there are 
  associated annexes featuring variability and double/multiple star 
  data, and solar system astrometric and photometric measurements.

  http://www.rssd.esa.int/index.php?project=HIPPARCOS
  A number of resources are provided indicating how the Hipparcos 
  and Tycho data can be used as educational tools

If you want an example of data analysis malpractice, look here:
  http://www.rssd.esa.int/index.php?project=HIPPARCOS&page=high_p
They say the effect of parallax is evident.  They should have added
a couple of parameters to the model to account for it.  They should
have drawn a wiggly line to show us how much of the scatter in the
data is explained by parallax and how much is not.

=====================

If you're willing to wait five years:

  http://sci.esa.int/gaia/
  08 January 2014 -- ESA's billion-star surveyor Gaia is now in its 
  operational orbit around a gravitationally stable virtual point in 
  space called 'L2', 1.5 million km from Earth.

  http://sci.esa.int/gaia/28890-objectives/
  Gaia's mission is scheduled to last for five years. During that time, 
  it will log the position, brightness and colour of every visible celestial 
  object that falls within its field of view. By repeating these observations 
  throughout its mission, astronomers will be able to calculate the distance, 
  speed and direction of motion of each of the celestial objects, chart variations 
  in their brightness, and determine whether they have nearby companions.