1
$\begingroup$

I was looking at the constellation Scorpius the other day, and noticed that the last star in the tail (the telson's tip) -- known as Upsilon Scorpii, υ Scorpii, or Lesath -- seemed yet more red than the "heart" of the scorpion -- Antares or Alpha Scorpii. Was it that I was drunk, or some kind of sky pollution? (Actually, a friend confirmed it was red, and she seemed sober than me.) Or is it, indeed, red? I couldn't find any information on-line. I saw this database, but don't know how to find a star by its name, or if they have information about the color.

$\endgroup$
9
  • $\begingroup$ @RobJeffries The red color was confirmed by at least another person (see my edit). Is there any site like a on-line telescope? $\endgroup$
    – Rodrigo
    Oct 11, 2017 at 11:28
  • 1
    $\begingroup$ Rodrigo, what you saw and what the star is are two different things. The star is blue/white. When you look at it through the atmosphere, especially low to the horizon, then it may appear to be something else. You asked a question - you have the answer. $\endgroup$
    – ProfRob
    Oct 11, 2017 at 11:31
  • $\begingroup$ @RobJeffries δ Sco, β Sco and π Sco were almost behind some not very close trees, so somewhat close to the horizon. Therefore υ Sco wasn't so low. It was the first time that I noticed it look SO red, and this called my attention. I would like if it could be confirmed by someone else (or at least discover why it appeared so red). $\endgroup$
    – Rodrigo
    Oct 11, 2017 at 11:43
  • $\begingroup$ Actually it is very close to lambda Sco which is a brighter star. But just as blue/white. $\endgroup$
    – ProfRob
    Oct 11, 2017 at 11:50
  • 1
    $\begingroup$ Then it is indeed a mystery! :-) $\endgroup$ Oct 13, 2017 at 23:47

2 Answers 2

3
$\begingroup$

I don't know what could cause Upsilon Scorpii to appear red as it is not noted as being a highly variable star. It's spectral type is B2, which implies it would be blue/white in colour. If you know the spectral type of a star, which many stellar databases will note, you can work out its colour from this.

$\endgroup$
2
  • $\begingroup$ The red color was confirmed by at least another person (see my edit). Is there any site like a on-line telescope? I got intrigued about this. $\endgroup$
    – Rodrigo
    Oct 11, 2017 at 11:28
  • $\begingroup$ Aladin Lite shows Upsilon Scorpii as blue in the DSS2 survey. $\endgroup$
    – user21
    Oct 11, 2017 at 16:07
2
$\begingroup$

Upsilon Sco is a blue/white (B-V =-0.17) B2 IV star according to the SIMBAD database entry.

As a slightly evolved B-type star it is unlikely to show any great variability and none has been recorded as far as I can see from a scan of the available references on the star. In fact it was included in a catalogue of the "least variable stars" by Adelman (2001), based on long duration monitoring by the Hipparcos satellite.

It might appear red if observed very low through a dusty atmosphere.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .