Astroquery SIMBAD : Obtaining data for diameter, mass, distance, luminosity and age of celestial object

Question

1. Is there any way in astroquery we can obtain data for diameter and distance of star for example? Seems like I can not find any of these reading the astroquery documentation and checking all supported fields in the votable_fields_dict.json file.

   Checking documentation on SIMBAD however (see image), there are measurements supporting these :

2. I'm pretty sure that luminosity of celestial object can be calculated using the Hertzsprung-Russell Diagram (HRD) and later on mass can be calculated using luminosity obtained in previous step. Also age of celestial object can be calculated based on the HRD. Can you please confirm this (Or there is some way to obtain these values using astroquery)?

Answer 1

SIMBAD does not have uniform information about stellar distance and diameter. Only some objects will have this information. SIMBAD stores it in the 'measurements' attribute. You can access this again through votable fields:

>>> from astroquery.simbad import Simbad
>>> Simbad.add_votable_fields('measurements')
>>> acen = Simbad.query_object('alpha centauri')

Then inspect acen.colnames to see all the data that is available: for alpha centauri, there is a lot!

For your second question, we can measure the brightness of objects very easily, but we can only measure their luminosities if we know their distances. This is a complicated task and requires different information for different objects. For Alpha Centauri, we can measure its distance directly by parallax, so its luminosity is straightforward to determine, but for most objects in the SIMBAD catalog more roundabout techniques are needed. This is a deep question and more appropriate for physics.stackexchange.com. If you want to just access catalogs of distances, sometimes SIMBAD will have that information, sometimes VIZIER will, but there is no single place to get reliable distances to astronomical objects.