9
$\begingroup$

Last night, I was on my balcony at 1AM (PST) and I looked up and saw two stars near the horizon (I'd guess ~30 degrees above the horizon), and they were "twinkling" about twice as fast as other stars higher in the sky, and I could clearly see them changing from red to white to blue repeatedly. Other stars in the sky only appeared white to me, and didn't seem to "twinkle" as rapidly as these two stars did. The red and blue make me think of red-shift and blue-shift, but I don't know how I would see both from the same object.

What was I seeing?

I don't know if it helps, but I am in the Los Angeles area, and I was looking in a roughly north direction. almost exactly to the east, according to google maps.

Edit: I tried taking a picture, but light pollution from the nearby street lights wouldn't permit me taking a decent picture. However, I noticed a group of three stars close together in nearly a perfect almost vertical line, and managed to find that in Stellarium. I think I found the two stars I am seeing: Procyon and Sirius

What I found in Stellarium

Is there anything about either of these stars that would make them show as red/blue?

Improve this question
$\endgroup$
5
  • 2
    $\begingroup$ Can you specify how far apart these two stars were? A good metric would be to use the width of fingers or your hand at arms length. E.g., the two stars were three fingers apart when held at arms length. $\endgroup$
    – zephyr
    Oct 27, 2017 at 19:53
  • 2
    $\begingroup$ (in case this is not obvious) The same stars will be there tonight (for at least a month or two) at almost exactly the same position. If they have gone, then you didn't see "stars" you saw aeroplanes or Halloween lanterns or something else. $\endgroup$
    – James K
    Oct 27, 2017 at 20:01
  • $\begingroup$ @JamesK I stared at the stars for about 5 or 10 minutes, they never changed position. They were also too high in the sky to be any sort of decoration. I'll take a picture tonight, hopefully my camera can do a high enough exposure to capture the light from the stars. $\endgroup$
    – Gogeta70
    Oct 27, 2017 at 20:05
  • 1
    $\begingroup$ Ha, go figure. Check the last sentence in this section on wikipedia $\endgroup$
    – Gogeta70
    Oct 28, 2017 at 8:24
  • 1
    $\begingroup$ You can install the application 'Star Walk 2' on your iPhone, or on Android Phone from App Store. It's one of the best apps for observation of night sky. It may help you to identify most of the bright objects in the night sky. $\endgroup$
    – Jaideep Khare
    Oct 28, 2017 at 13:46

4 Answers 4

Reset to default
11
$\begingroup$

It's most probably Sirius. At this time of year (at 1 am local time) it's low in the sky in the East, so there is a lot of atmosphere in the way, and as Sirius is a bright bluish star, it will show all the colours described as it twinkles.

Improve this answer
$\endgroup$
2
  • $\begingroup$ @JamesK Sirius seems to be the right answer, at least one of the two I was seeing. Maybe 30 degrees was a high estimate on my part... :P $\endgroup$
    – Gogeta70
    Oct 28, 2017 at 8:16
  • $\begingroup$ This should be the standard answer. Every year in March / April this kind of question pops up again and again - when Sirius is due south in the evening sky. $\endgroup$
    – Florin Andrei
    Apr 2, 2018 at 17:46
8
$\begingroup$

As you have already identified the objects you were seeing, I'll explain the effect you were seeing. In that situation there are three things to consider: atmospheric chromatic dispersion, seeing and human color perception.

Light entering the atmosphere is refracted, because of the changing speed of light in air compared to the vacuum of space. The amount of refraction depends on the wavelength, causing optical dispersion. This effect is strongest for objects appearing near the horizon. Basically the different color components of the star's image appear at slightly different elevations in the sky (nice in-depth explanation).

Turbulence in the atmosphere causes the "twinkling" or seeing. Moving pockets of hotter and colder air act like lenses that are projecting the star's light into varying directions, so a varying amount of light reaches your eye. Together with the dispersion this produces a colorful twinkling.

Because the color perception in the human eye doesn't work in faint light, this colorful twinkling is observed for the brightest stars only.

The doppler shift is not the reason for the red and blue colors. At a typical velocity dispersion of 30km/s of our surrounding stars, the doppler shift changes the wavelength by an imperceptible 10-4 fraction. Also this would have to change extremely rapidly, which simply does not occur for our average night-sky stars or most other objects, for that matter :-)

Improve this answer
$\endgroup$
4
$\begingroup$

Using a star chart and based on your location, direction of observation, and time of observation, I'd guess you were seeing the star Capella.

Capella is quite a striking star because it's actually four stars. There are two sets of binary pairs that are almost exactly along the same line of sight such that the light from the four stars together co-mingles and from Earth looks like a single star. Interestingly, the different stars have different colors, meaning that as you stare at it, it can appear white, red, or blue, just as you described. Note that the human eye cannot observe redshift and blueshift like you describe.

The fact that the star twinkled more than those higher up is due to the atmosphere itself. The closer to the horizon a star is, the more it will twinkle due to the starlight passing through more atmosphere before reaching you.

Improve this answer
$\endgroup$
4
  • 1
    $\begingroup$ The phenomenon is called "seeing" by astronomers, and it's basically air turbulence. The higher the turbulence, the more twinkling. $\endgroup$
    – Florin Andrei
    Oct 27, 2017 at 19:17
  • $\begingroup$ Possible but Capella is higher in the sky, and the OP mentioned "two stars" Perhaps Castor and Pollox? $\endgroup$
    – James K
    Oct 27, 2017 at 19:40
  • $\begingroup$ Awesome! Unfortunately, I looked on google maps at my address, and it appears I was actually looking east. I judged my direction by the nearby northbound freeway, which actually travels east for a few miles near where I live. I'll try to take a picture tonight with a high exposure - maybe seeing the stars can give a better idea of what I was seeing. $\endgroup$
    – Gogeta70
    Oct 27, 2017 at 19:41
  • $\begingroup$ @JamesK You may be right. I'm not convinced it was Capella, but its in the right area at the right time at least, and I know it can definitely appear red and/or blue. $\endgroup$
    – zephyr
    Oct 27, 2017 at 19:52
-2
$\begingroup$

They are not stars I’m from Prince Edward Island Canada those red blue and white looking disco balls in the sky are something the police or military are using. Look on U tube thier are people all over the world seeing the same thing . If u watch those for long enough they will drop every 3 hours approximately. And in most cases especially mine thier is heavy drone activity when these are present. I have really good footage of a lot of this stuff as I bought good camera equipment to gather evidence. If u have these near your house it’s not a good thing as your privacy is being affected from the law or military.

Improve this answer
$\endgroup$
1
  • 6
    $\begingroup$ The information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted. $\endgroup$
    – Glorfindel
    Apr 1, 2018 at 9:26

You must log in to answer this question.

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