Astronomy People: What Did I see?
August 19th, 2010While taking the dog out for her nightly last night I noticed a “star†madly twinkling, fairly low in the west. It seemed almost to be changing colors, flickering between red and a greenish-white. I watched it for a minute or two, thinking it must be a distant aircraft flying directly away from me, but no, it didn’t go away. Intrigued, I got out my 10×25 field binoculars. They showed what looked like a red point of light flickering around a greenish-white point—very hard to distinguish though, given they were hand-held.
My best guess is I saw a star or planet in near alignment with a more distant star, and the flickering was a result of refraction as it sank lower behind the humid atmosphere. But I’m not good at reading star charts and would appreciate further thoughts.
This was between 10pm and 10:30pm HST, August 18. Approx lat/long 20.90 156.43
Posted on: Thursday, August 19th, 2010 at 9:47 am
Categories: Meanderings.
August 19th, 2010 at 7:29 pm
I’m guessing it was Mars lining up with a star, but I can’t swear to that because I’m not sure of Mars’ position right now.
August 20th, 2010 at 10:20 am
Hi Linda,
I stumbled across the following here (http://nightskyonline.info/?p=922), by googling “western horizon flickering object august” (it is the 3rd result):
“If you are new to astronomy, one of the first questions you are likely to ask at the moment is “What is that bright flickering star I can see above the Western horizon in the early evening sky?â€. That is Venus. The reason for it flickering has to do with the light from it being ‘bent’ or broken into the individual colours of the rainbow/spectrum by the Earth’s atmosphere as it starts to set. The lower down an object is the more atmosphere the light has to travel through. Add in a bit of wind in the upper atmosphere and you start to get a ‘star’ which can change colour and make people wonder if they are seeing a UFO. They aren’t. It is just Venus.”
I then checked out the sky you were looking at by setting the coordinates & time you provided into a really neat (& free) planetarium application called Stellarium. Sure enough, there’s Venus on the western horizon, & Mars sits right next to it (which ought to interest the poster of the previous comment). Saturn lies a bit below these, & to the right (northwards), while above & a smidge further south of them is a star, Vica. Above all these, almost perfectly west, is a very bright star called Arcturus, one of my favorites. I used to be into astronomy quite a bit; but now I reside in the Seattle area, so you can imagine how rarely I get to see much anymore. Checking out your mystery object brought back some good times. Thanks.
August 20th, 2010 at 2:31 pm
Hi Ryan. Thanks for the research! I knew it couldn’t be Venus, because Venus would have already set at the time I saw it. But I think Arcturus is indeed the likely suspect. I found a star chart of Hawaii skies here– http://www.ifa.hawaii.edu/publications/starcharts/ –which puts Arcturus in the proper position. Then when I googled “twinkling Arcturus” I came up with this:
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“The more air the star has to travel through, the more it twinkles. As the altitude of Arcturus above the horizon increases, it shines through less and less air so its twinkling lessens. Next time you’re out compare two fairly equally bright stars; one near the horizon and one high overhead. The latter will twinkle less.
“Also, more air leads to the bending or refraction of starlight, spreading it out into into a rainbow, which explains why you saw it flashing colours. That colour display also lessens as the star rises in the sky and will increase again as Arcturus begins to set. ”
(This is from a comment by astroneil at http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3639687/Main/3638932 )
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So I think that’s the solution. I didn’t realize a star’s light could be spread out like a rainbow. Now I’ve got a new effect to look for.
Thanks again!
August 20th, 2010 at 2:58 pm
Yay, mystery solved!
August 20th, 2010 at 3:10 pm
Mark, thanks for your input too!