5th Moon?

[CowsonConcrete]

Hi,

Long time reader, first time poster.

I have spent the last month watching Jupiter from my backgarden using a Celestron 102mm Spotting scope with a 10mm eye piece. When I get Jupiter in my sights I can see 4 moons in a straight line but then off to the left and slightly up is another large "moon" object - What is this?

Thanks for any help.

[starstalker]

Uranus is near jupter at the moment, is it that?

[acey]

Most likely a star. The fifth moon, Himalia, is fainter than Pluto and needs large aperture. Does "large" mean bright or disc-like? Uranus would be resolvable as a disc.

[oldfruit]

Is it moving from night to night in relation to jupiter? If not it could be Uranus as they are very close at the moment.

[CowsonConcrete]

I don't think it's another planet as it looks like the other moons. To clarify I see 3 large moons and a smaller one in a line in front of jupiter and this "other" object is perhaps half a degree to the East.

Thanks for your quick responses by the way.

[acey]

Everything moves from night to night in relation to Jupiter. I'd say it's almost certainly a star - someone with Stellarium or similar could provide a candidate - in which case if you watch it over several nights then you should find that Jupiter and its moons will move in relation it, while the object itself remains fixed in relation to other field stars.

If it looks bright in comparison with the moons then it should be brighter than mag 5 hence not hard to identify.

Edit: I just had a quick look on Cartes du Ciel and the star SD-03 5697 might be candidate, though it's magnitude 7. Interestingly there's also the minor planet TYC5255-00876-1 though it's mag 11. I don't see how either would appear "larger" than moons, though perhaps the glare of Jupiter was making the moons look fainter.

The 5.5 mag star 20 Psc would have been the nearest bright star last night so maybe that's the strongest contender.

[starstalker]

try and get a picture up?

[oldfruit]

Do you have stellarium? I have just checked and there is a 5.45 magnitude star to the upper left at the moment, about as bright as the moons?

[CowsonConcrete]

Apologies Acey, I'm new to this. I tend to look between 7.30pm and 8pm. I'll check it out tonight and see if I can take a picture and attach it to future posts.

[CowsonConcrete]

Thanks for all your help. I'll check my friends Stellarium over the weekend.

Great site.

Rather than add my details I'll give you the link to my blog;

Constellations and Coffee

Hope it's not too amateurish!

Thanks again

[lukebl]

You will find that Jupiter moves from night to night, so it will inevitably pass by stars along the way, and what you see near it one night will be different from, say, a week or two later.

[LukeSkywatcher]

A friend emailed me today saying that he has been observing Jupiter for a few nights now. He is not an astronomer by ANY means. I keep him informed with stuff. He said that last night he saw Jupiter and 5 moons.

The "fifth" moon people see is a star. Its a very common mistake made.

[perrin6]

Probably definitely perhaps 20 Pisceum (maybe).