Jupiter 5th largest moon?

[ubertank]

Got the scope in my light polluted garden for a bit tonight. There was slight cloud cover but I wanted to have a mooch at the moon anyway.

Anyway, I had a look over at Jupiter and could see a 5th moon. It was much dimmer than the big four, but it was definitely there. I know Jupiter has 67 moons, but does this 5th one have a name? I'd not spotted it on previous outings.

[lukebl]

What you saw would have been a star. After the 4 Galilean moons, then next brightest are 14th mag and very tricky to see visually except with big apertures, or photographically.

[ubertank]

I thought it may have been a star actually so went back and checked half an hour or so later to see if it would have been in the same spot. I thought to myself if it were a star it should change position slightly due to the distance differential, but saw it in the same spot. I guess it must have moved and I didn't spot it.

Thanks for the clarification though. Still learning

[Capricorn]

Fifth biggest is Himalia.

However I doubt that you saw it, don't get me wrong, but the smallest of the Galilian moons is 4,800,000 x 10^16 Kg, Halilia is 670x10^16Kg so 0.00014 the size of the smallest Galliian. Almost 1/10,000.

So much smaller that I seriously doubt it being visible except to a camera.

Jupiter's Moons

Go to the Mass column and click to reorder by the largest with regards Mass. After the main 4 everything else is really small.

At the moment Jupiter is in the Hyades so the Milky Way is there, it could have been a distance faint star. What makes it more doubtful is that you say there was a slight cloud cover. Throw in that is has a very low albedo, so not bright at all.

It was located it seems by the Lick Observatory which is 36".

[ubertank]

No you guys will be absolutely right. I thought it was a star initially and spent 10 minutes googling to see if the 5th was observable but found no definite reply so thought I'd check.

Thanks for the replies and the helpful information.

[dtr42]

have had same experience saw 4 moons and then another 3 bright objects checked on stellarium and it was background stars, an easy mistake to make

[bennylee79]

yeah, it was hip 20785. I too thought it was a 5th moon but after checking stellarium i found out it wasnt. The good thing about it i was showing friends jupiter through my scope so they were very interested in finding out if it was a fifth moon.

[Tddun]

Pete Lawrence photo'd this moon once I believe, don't have the link at hand though.

[Skylook123]

_{Fasten seatbelts for trivia launch. E.E. Bernard announced the September 09, 1892 discovery of a fifth Jovian moon, Amalthea, visually, using the 36" refractor at Lick Observatory in an 1892 article in the Astronomical Jounal entitled "Discovery and Observation of a Fifth Satellite to Jupiter." By average distance from Jupiter, it is in the inner group and third moon from Jupiter. Himalia was the sixth discovery, in 1904, by Charles Dillon Perrine, who also discovered the seventh moon, Elara, in 1905 (both also from the Lick Observatory, I believe, but photographically). The three were merely called Jupiter V, VI and VII until named by the IAU 1975.}

_{Ramble mode off....}

[Mr Fiery Jack]

I saw the star you are talking about tonight too, an easy enough mistake to make if you didn't know.

[lukebl]

Here's a capture I made last year of Himalia, one of the 'easiest' of the smaller moons. Still at 14th mag, and almost overpowered by the intense glare of Jupiter. Single frame, 60 seconds, SXVF-H9, 250mm f/4.7 Newtonian.

The bright 'star' to the lower left edge of the glow is Callisto and the one upper right, almost lost in the glare, is Ganymede. The other two Galilean moons are completely lost in the glare. All the other stars are just stars!

[Double Kick Drum]

No you guys will be absolutely right. I thought it was a star initially and spent 10 minutes googling to see if the 5th was observable but found no definite reply so thought I'd check.

Thanks for the replies and the helpful information.

If you fancy bagging some more moons, Saturn is your best bet.

Titan is around mag. 8, Rhea, Tethys and Dione are all around mag. 10, Iapetus slightly feinter again (depending what side is showing) and at a push Enceladus can get up towards mag. 11.5.

I think Mimas and Hyperion might be theoretically possible but are likely to need serious aperture / imaging equipment.

Iapetus is the feintest moon I have found, done with a five inch refractor.

Happy hunting!

[ubertank]

So much awesome helpful information.

Love this forum.

Thanks again everyone!