Zeta Boötis

[timwetherell]

Has anyone observed Zeta Boötis recently? I was just wondering what the current separation was? It's listed as 0.7" in Sissy Hass' double star book which should in theory be resolvable (or at least significantly elongated) in my scope but I wasn't having much luck last night. Might be a seeing issue or it's entirely possible I was looking at the wrong star! 

Wasn't all bad though, Izar was my "new to the northern hemisphere" discovery of the night. Really stunning - to me the north's answer to Antares 

[chiltonstar]

27 minutes ago, timwetherell said:

Has anyone observed Zeta Boötis recently? I was just wondering what the current separation was? It's listed as 0.7" in Sissy Hass' double star book which should in theory be resolvable (or at least significantly elongated) in my scope but I wasn't having much luck last night. Might be a seeing issue or it's entirely possible I was looking at the wrong star! 

Wasn't all bad though, Izar was my "new to the northern hemisphere" discovery of the night. Really stunning - to me the north's answer to Antares 

Currently (2015) 0.4 arcsec according to Stelle Doppie, and 0.5 arcsec according to CDSA. In my 180 Mak at x350, it is an elongated oval.

Izar is also my favourite double - simply stunning!!

Chris

[Saganite]

Hi Tim,

My Cambridge Double Star Atlas gives .4" as of 2015

[John]

Have to have a go at Zeta with my 130

Izar is a beaut though !.

 

[timwetherell]

25 minutes ago, Saganite said:

Hi Tim,

My Cambridge Double Star Atlas gives .4" as of 2015

Thanks, yes that would explain a lot. I could have convinced myself that it was slightly oval but I've split 0.7" before so I didn't think that could be right. Sneaky little things these double stars, keep getting closer together!

[timwetherell]

1 hour ago, John said:

Have to have a go at Zeta with my 130

Izar is a beaut though !.

 

It was perceivably egg shaped in my 180mm at 1100x so may be slightly out of round in the 130 too if you give it enough "welly"! I was expecting 0.7" but if it was 0.7" in 2008 and 0.4" in 2015 maybe more like 0.3" today. Your 15" should do that on a good night?

Yes, I hadn't seen Izar before - it's an absolute cracker! I kinda miss Antares which is a real beauty when high in Oz but hard to split lower down. not sure if it can be done from the UK as it never really gets clear of the mush?

[John]

I split Antares last year with my 130mm triplet. It was very low, between 2 houses in fact, but the split was clear and very nice

[chiltonstar]

4 hours ago, timwetherell said:

It was perceivably egg shaped in my 180mm at 1100x so may be slightly out of round in the 130 too if you give it enough "welly"! I was expecting 0.7" but if it was 0.7" in 2008 and 0.4" in 2015 maybe more like 0.3" today. Your 15" should do that on a good night?

Yes, I hadn't seen Izar before - it's an absolute cracker! I kinda miss Antares which is a real beauty when high in Oz but hard to split lower down. not sure if it can be done from the UK as it never really gets clear of the mush?

Impressive that you could use x1000 in the UK!

I've split Antares twice now from the UK - doesn't need a big scope, just a good southern sight line and excellent++ seeing!

Simulations of Zeta Bootis with a 180 MCT and a 130mm frac, both at a nominal x1000 (Aberrator)

Chris

 

 

[timwetherell]

Interesting! I think in my 7" frac it looked somewhere in between those two but it's hard to precisely quantify "eggyness"  Mostly I was winding up the umph in a desperate attempt to split it as I mistakenly thought it was 0.7"

Seeing was pretty good last night in the south west, I was observing jupiter at 300x and it was holding in the steady moments. I was going to do a drawing but it was 11pm and there was a glass of brandy in the lounge with my name on it!

[John]

Tim, presumably your 7" frac is not the Great Wetherell Refractor but a different one - is that correct ?

I thought I'd read that the GWT had gone to the USA ?

 

[Dave In Vermont]

As we've got differing arc. seconds for this star(s), does anyone have it's listed period between min. & max?

A most interesting star this Zeta (and Izar)!

Dave

[Stu]

This is the info SkySafari has:

Orbital period 125.24 years, getting harder through until late 2023, next easiest in 2082!

Orbit

What is unusual about this binary system is its orbital eccentricity. The stars loop around each other on hugely elongated paths, which carry them from 1.4 AU apart (about Mars's distance from the Sun) to 64 AU (50% farther than Pluto). The pair are visually inseparable at closest approach, which occurred in 1897 and will take place again in 2021. At farthest separation, the are easily resolved; the best view will come in 2082.

This ellipticity is close to a record. With an orbit like this one, no planets would be possible in the system. The large eccentricity suggests some kind of violent encounter with another star; perhaps a third member was lost in the process.

[Moonshane]

Very cool post Stu. I like the additional information

[Dave In Vermont]

Thanks for that! Just what was needed.

Here's a wonderful site for anyone who enjoys double-stars:

https://bestdoubles.wordpress.com/

Have fun -

Dave

[chiltonstar]

Nice orbit Stu and information - certainly changes fast, even in the time I've been looking at it! From my notes of 1 year ago, I could see a slight waist whereas last night it was oval, but no waist!

Chris

[Stu]

59 minutes ago, chiltonstar said:

Nice orbit Stu and information - certainly changes fast, even in the time I've been looking at it! From my notes of 1 year ago, I could see a slight waist whereas last night it was oval, but no waist!

Chris

Thanks Chris. It is interesting to step through the years on SkySafari and watch the speed change as it goes around its orbit. It whips around very quickly when passing closest to the other component, but at its furthest reach it is moving far slower, as you would expect. I guess that explains the rapid changes you have observed.

[chiltonstar]

27 minutes ago, Stu said:

Thanks Chris. It is interesting to step through the years on SkySafari and watch the speed change as it goes around its orbit. It whips around very quickly when passing closest to the other component, but at its furthest reach it is moving far slower, as you would expect. I guess that explains the rapid changes you have observed.

I suppose when a pair are as close together as this, any slight change will be very apparent, whereas if they were 100 arcsec apart, you wouldn't spot a 0.1 arcsec change in a year. Interesting how well resolved Zeta Herculis was last night as well, even at x540; the colour difference there seems obvious cf Zeta Bootis, where the two components both seem white.

Chris

[Stu]

7 minutes ago, chiltonstar said:

I suppose when a pair are as close together as this, any slight change will be very apparent, whereas if they were 100 arcsec apart, you wouldn't spot a 0.1 arcsec change in a year. Interesting how well resolved Zeta Herculis was last night as well, even at x540; the colour difference there seems obvious cf Zeta Bootis, where the two components both seem white.

Chris

I think it is more than that Chris. I believe, from my school boy physics that there is an exchange of potential and kinetic energy due to the conservation of energy. When closer to the other component there is less potential energy so more kinetic energy i.e. the star is moving much faster. At the outer reaches of the orbit at maximum separation, there is much more potential energy, less kinetic and the star moves much slower.

I think this is illustrated by these four images. The first two show the annual change in position at closest approach, and the second pair are again the annual change but at furthest approach. Big change in the first, barely noticeable in the second so it is a real change in orbital speed.

[chiltonstar]

44 minutes ago, Stu said:

I think it is more than that Chris. I believe, from my school boy physics that there is an exchange of potential and kinetic energy due to the conservation of energy. When closer to the other component there is less potential energy so more kinetic energy i.e. the star is moving much faster. At the outer reaches of the orbit at maximum separation, there is much more potential energy, less kinetic and the star moves much slower.

I think this is illustrated by these four images. The first two show the annual change in position at closest approach, and the second pair are again the annual change but at furthest approach. Big change in the first, barely noticeable in the second so it is a real change in orbital speed.

Indeed: I seem to remember the same thing, although my schooldays were rather more distant than yours!

There is a target list somewhere of interesting short-period doubles which would make a nice observing project if I can find it.

chris

[Moonshane]

I observed this last night and noted in the Cambridge double star book that I had observed it previously. Somewhat puzzled I found it and wondered what all the fuss was about as at about 200x it was an easy wide split. I then checked again and realised I'd looked at  Zeta Coronae Borealis instead!  Then, naturally the clouds rolled in so I didn't have chance to look at the real Zeta Bootis. I was reminded though of how good my 6" f11 is on doubles. Izar was stunning as was Porrima, so perhaps I have a chance in due course.

[John]

I tried Zeta Bootis a week or so back with my 130mm triplet. Got an elongated egg shape so clearly not a single star but no sign of a "waist" between the two airey disks.

Zeta Herc has been going well this season - I've probably "got my eye in" with that one

Some lovely multiple stars in that part of the sky. Izar and Porrima as you say Shane plus the triple Alkalurops (mu Bootis) which I've become very fond of

[Moonshane]

Oh, yeah I looked at that too (mu Bootis) last night as it's next to the Zeta I was observing, hence the confusion! 

[Moonshane]

Zeta Coronae Borealis is actually worth a look. A bit like a dimmer wider Castor. In other words, nothing like Castor LOL.

[John]

47 minutes ago, Moonshane said:

Zeta Coronae Borealis is actually worth a look. A bit like a dimmer wider Castor. In other words, nothing like Castor LOL.

In the same way that Porrima is a bit like half of Epsilon Lyrae