Author Topic: OR, U Cygni  (Read 1975 times)

mccarthymark

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OR, U Cygni
« on: October 01, 2014, 10:07:16 AM »
I try to observe as much as I can from home.  Even with the usual light pollution and seeing limitations, there is still much to see: doubles, bright clusters, and so on.  Last night I tried a couple new doubles in Cassiopeia, but even though I had put my scope out in the back yard after coming home from work at 6:30pm, I was still getting some tube currents by 9:30pm.  I was going to pack it in, but decided to wait, and revisited some familiar targets (Gamma Delphini the beautiful yellow pair; Beta Cygni copper and blue; the Blinking Planetary) to help pass the time.  Fortunately by 10pm the tube currents and the sky settled down and I was getting very nice steady stars.

After the Blinking Planetary I went to Omicron 1 & 2 Cygni; then checked my chart for something else to view, and noticed U Cygni nearby, which was marked as a carbon star.  I had seen a few carbon stars before but WOW what a sight U Cygni was!  Very small, not bright, but a deep ruby red color.  It looked just like a ruby on black velvet.  I couldn’t get over its color.  There was a nearby white (and much brighter) star which likely helped with the color contrast.

Looking up this star this morning, I find it is classed (Morgan–Keenan C system) C7-C9 which has strong carbon abundance and helps account for the deep red color.  It’s also a variable, ranging from 5.9-12.1.  To my eye last night it was small and faint; I’d guess 10-11 mag.  Checking AAVSO’s light curve generator now, it seems I was in the neighborhood: latest readings are 10.5!  The period is 421 days, and it is nearing its minimum.  I will revisit this star next year—the nearby bright star is 8.0, so it will be interesting to compare U Cygni to it again, when U Cygni has outshone it.  I wonder if U Cygni's color will be as deep?

All goes to show you need not always go to dark sites to enjoy this hobby.  I hope others will give this one a try, it’s really
beautiful.

--Mark
« Last Edit: October 01, 2014, 01:00:36 PM by mccarthymark »
Mark

Lumpy Darkness

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Re: OR, U Cygni
« Reply #1 on: October 01, 2014, 11:02:37 AM »
Another nice report, Mark.  Inspires me to pull out my 10" this week in my backyard too.  Long time since I've done that.

I love how we get such a strong visceral reaction to seeing such intense colors in stars, or splitting tight or unequal doubles.  Then how it prompts us to understand the science behind the object. Aesthetic leads to intellect.

I'm reminded how I felt finding these special sights is like digging for gems.

Keep the reports coming!

mccarthymark

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Re: OR, U Cygni
« Reply #2 on: October 01, 2014, 01:07:29 PM »
For sure!  I've read a bit more about it.  I'm not the only one who has noticed the deep red color of this star recently, there are other ORs out on the web.  And, to answer my question, the color does change as it passes through its variation -- its deepest red is at minimum (now and the next ~2-3 months) but will be a lighter orange-red color at maximum late next year.  This is the case for all of them, but is more pronounced with those with huge variability, such as this one.

I'm hooked now.  I'll start the AL Carbon Star program, steal my daughters' colored pencils for sketching, and do it on index cards so I can file by star and track changes over time.  These are really fascinating.
Mark

Lumpy Darkness

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Re: OR, U Cygni
« Reply #3 on: October 01, 2014, 01:11:47 PM »
Hind's Crimson Variable is another you'll like then, in Lepus.  I recall that it reddens deeply as it dims.  Bet they're the same type stars.

DDK

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Re: OR, U Cygni
« Reply #4 on: October 01, 2014, 02:04:23 PM »
They are the same type stars. Aesthetic leads to intellect, cool thought. And it goes back the other way. Fascinating how it's hot carbon putting out deep red light. They're old and big and hot and way along on their way thru the main sequence.
At CalStar, Mark Buxbaum was showing off T Lyrae in his new 22". Small and very deep red. I've seen a handful of well-known carbon stars, all surprising with their color. Haven't seen U Cyg yet!
mu Cep (Herschel's garnet star), S Cep, yep R Lep, and c Pup, UX Dra, Y CVn (La Superba), and V Aql.
TAC - astro anarchy at work <*>

sgottlieb

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Re: OR, U Cygni
« Reply #5 on: October 02, 2014, 09:58:10 AM »
I don't usually post observing reports on individual stars, but I'll fess up that I'm a closet carbon star observer.  Notice the mag estimate back in Sept '06.

U Cyg
20 19 36.6 +47 53 39
V = 6.5-12.0

18" (9/25/06): striking ruby red carbon star (B-V = 3.3) at 115x.  A white mag 7.9 star (HD 193700) just 1.1' NE forms an excellent contrast for the deep red color.  Viewed well below maximum brightness, perhaps mag 10-11.  A curved chain of stars oriented NW to SE passes through U Cyg and the mag 8 star. Period = 463 days.