Starship Asterisk*

http://apod.nasa.gov/apod/ap070415.html

I'm curious about why there are at least 2 groups of RR Lyrae variable stars that appear to be highly synchronized. Could such a group be one star lensed by something inbetween us and them? Could they have formed simultaneously in close proximity and drifted apart? Seems intriguing.

They probably just seem synchronized because it's really not a movie but apparently only a repetition of four images, taken during one night. My guess is that, if you'd see a true movie, most stars would probably have a unique cycle.

Looking at a yellow star on the left side of the cluster, I noticed a dark dot that appears to rotate around the star. Is this just an anomaly of the time sequence or might there be something to this.

I'm just an amateur viewer of the site, but this caught my eye.

Thanks

I see a single dark pixel or two. I'd say it's an imager defect or a glitch in the data.



A way you can tell is this: Actual objects in the image will all have about the same level of focus or fuzziness. This dark pixel is alone and not fuzzy like all the stars.

Also, the stars cannot be seen as disks or balls by any telescope we have on Earth. The fact that they're showing up in an image as more than one pixel in size is an imaging or possibly atmospheric artifact. At this distance they're all point light sources, so you would not be able to see anything in front of one of them.

While bright star images may bloom during exposure due to twinkling, optics, or even the characteristics of the imager itself, atrophotographers often also allow the sizes of brighter stars to grow even larger during image processing, so as to represent them as brighter within the severe limitations of our display and print technology. We have no display that's capable of representing the extreme dynamic brightness differences of astronomical objects directly, so we use tricks like increasing star size to help represent reality within the limitations of the medium.

-Noel

there appear to be approx 20 or so dark pixels that appear in the central portion of the cluster at the same frames as this anomoly.

This dark pixel is alone and not fuzzy like all the stars.

How could a single pixel appear fuzzy? A small dark object roughly located at around the centre of a pixel would surely appear exactly as that does.

I agree it is almost certainly a detector artifact by the way.

My point is that it's pretty clear that the stars in the image are NOT focused anywhere near the single pixel level, and so something in the image appearing as a single dark pixel must be an artifact (imager defect, tiny dust speck, glitch in the data... You get the idea).

-Noel

[I'm no scientist. Just an interested novice.] So I was directed to this APOD from 15 Apr 2007 by a link in today's APOD, 19 Nov 2013. The explanation does not really tell me the cause of the stars blinking. I'm not sure how long astronomers have been finding extrasolar planets by measuring the light from flickering stars, when they pass in front of them (has it been a decade already?), but could all of the flickering we see in these time-lapse photos be because a planet is passing in front of them? Is a planet always the cause of a twinkling star? If so, then there must be a lot of planets out there! This old APOD proves it!

moconnor wrote:[I'm no scientist. Just an interested novice.] So I was directed to this APOD from 15 Apr 2007 by a link in today's APOD, 19 Nov 2013. The explanation does not really tell me the cause of the stars blinking. I'm not sure how long astronomers have been finding extrasolar planets by measuring the light from flickering stars, when they pass in front of them (has it been a decade already?), but could all of the flickering we see in these time-lapse photos be because a planet is passing in front of them? Is a planet always the cause of a twinkling star? If so, then there must be a lot of planets out there! This old APOD proves it!

It's not planets, and it does very clearly explain that the blinking stars are RR Lyrae variable stars.

I ended up going through the Hubble archive and discovering that there is a 12 hour sequence of images to make a similar animation with for this cluster. Variable stars! Now I'm searching around for some more distant star clusters which fit into the frame better to try to capture a more lively animation.

Edit: Oops, the forum can resize animated gifs to thumbnail size but the thumbnail was still pretty big. Here is a link to the file (5.59 MB) at Flickr instead:
http://farm4.staticflickr.com/3692/1105 ... d6d3_o.gif

Ahh, nice gold stars. I take it the blinking ones are the 'variable' ones. I also take it that we're not seeing the actual timing of their variableness though.

Yes, it was a 12 hour sequence condensed into a quick loop.