<p>Hipparcos measured the parallax (distance) of stars, along with their colors in two wavelength regions (B_Tycho, "blue" and V_Tycho, "green"). Using the color information you can make a reasonable estimate for the stellar temperature, and coupled with the parallactic distance, this would allow you to get an estimate for the stellar radius.</p>

<p>But Hipparcos does not provide us with any good information about stellar metallicities, ages*, radial velocity, rotation, or surface gravity.</p>

<p>* - aside from stars that you can group in position and velocity space to identify as belonging to stellar moving groups with defined ages.</p>

CC BY-SA 3.0
2017-03-17T21:49:53.583Z
Thanks for the answer, I thought that would be the case.  When you talk about B_Tycho and V_Tycho, you're talking U-B and B-V indices right?
MiscellaneousUser
CC BY-SA 3.0
2017-03-17T22:11:43.013Z
Nope. Hipparcos had an onboard photomultiplier that measured photometry on several million stars. The filters it used were close to Johnson-Cousins B and V, but not quite. So all the stars in the Hipparcos (and Tycho) catalogs have "Tycho magnitudes" in these particular filters. The color index you can measure for each star is then B_Tyhco - V_Tycho. This also means that the transformation from (B_Tycho-V_Tycho) to temperature will not be quite the same as Johnson-Cousins (B-V) to temperature.
Thomas
CC BY-SA 3.0
2017-03-17T21:16:05.033Z
2017-03-17T21:16:05.033Z
Thomas
<p>Is it possible to derive Metallicity/Age/Radial Velocity/Rotational Velocity/Surface Gravity of a star from Hipparcos data files or are do they require individual studying?</p>

<star><star-catalogues><hipparcos>
Stellar Information from Hipparcos
MiscellaneousUser
# Stellar Information from Hipparcos

(Asked by: username_0 on 2017-03-17)

Is it possible to derive Metallicity/Age/Radial Velocity/Rotational Velocity/Surface Gravity of a star from Hipparcos data files or are do they require individual studying?

**Tags:** star, star-catalogues, hipparcos


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## 1 answers

### Answer by username_1 on 2017-03-17. Score: 2 | Accepted answer

Hipparcos measured the parallax (distance) of stars, along with their colors in two wavelength regions (B\_Tycho, "blue" and V\_Tycho, "green"). Using the color information you can make a reasonable estimate for the stellar temperature, and coupled with the parallactic distance, this would allow you to get an estimate for the stellar radius.

But Hipparcos does not provide us with any good information about stellar metallicities, ages\*, radial velocity, rotation, or surface gravity.

\* - aside from stars that you can group in position and velocity space to identify as belonging to stellar moving groups with defined ages.

> **Comments:**
> **username_0**: Thanks for the answer, I thought that would be the case.  When you talk about B_Tycho and V_Tycho, you're talking U-B and B-V indices right?  
> **username_1**: Nope. Hipparcos had an onboard photomultiplier that measured photometry on several million stars. The filters it used were close to Johnson-Cousins B and V, but not quite. So all the stars in the Hipparcos (and Tycho) catalogs have "Tycho magnitudes" in these particular filters. The color index you can measure for each star is then B_Tyhco - V_Tycho. This also means that the transformation from (B_Tycho-V_Tycho) to temperature will not be quite the same as Johnson-Cousins (B-V) to temperature.  

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