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Earths "second moon", is it visible in a scope ?


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One of these days, I might revisit VIDEO Astronomy! lol. At magnitude +15.8 (maximum) it should be quite possible to image it with my trusty 8" f/4 Newt. Hey, Pluto is brighter(!), yet I suspect

There must be somebody up for the challenge?  Maybe a tweak of the title and moving this to the imaging section might get their competitive juices flowing!  Got to google it now. How come it

All news to me?   This asteroid/second Moon at only 3 miles wide, fainter than Pluto and  over 7 Million miles out, its going to be hard to find! Its suggested  that a telescope of  320mm / 12.5" sc

There must be somebody up for the challenge? 

Maybe a tweak of the title and moving this to the imaging section might get their competitive juices flowing! 

Got to google it now. How come it never gets mentioned? Guessing that it must be tiny given the Mag.

Paul

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So it's not really a moon of earth as it goes round the sun, but shares some of our orbit, even if it cannot actually hit the earth.  You can find pics on the internet, but no real surface details..

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45 minutes ago, spaceboy said:

As the title asks. Is it possible to see Cruithne using a scope and if so has anyone seen it and how would you go about finding it ????

Had a quick look on Wiki which obviously isn't peer reviewed but taking that on the chin it says it made it's closest approach to Earth every November between 1994 and 2015. It also mentions it's on a 1 Earth year orbit around the Sun so I'm guessing November 2016 might be a close approach also in which case it might be a good time to try and spot it. 

Wiki also suggests a 12.5" scope would be needed due to it's magnitude, so that rules me out. 

 

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Cruithne was discovered by Duncan Waldron on October 10, 1986  analysing a photographic plate taken with the UK Schmidt Telescope at Siding Spring Observatory, Australia. The telescope has an aperture of 1.24m and apparently can image down to magnitude 21.

So it's possible :icon_biggrin:.

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21 hours ago, mikeyj1 said:

So it's not really a moon of earth as it goes round the sun, but shares some of our orbit, even if it cannot actually hit the earth.  You can find pics on the internet, but no real surface details..

By definition for it to be a moon it has to orbit around the planet under the influence of Earths gravity so technically it isn't "Earths moon". On the other hand and in the very loose sense it is a second moon. That is because Cruithne was going about it's daily business flying through space when it came under the influence of Earths gravity. This then set in to motion an orbit of it's own which as it was created by Earths gravity some consider it as a second moon. Even though it doesn't actually orbit Earth it does return to us.

Just think, had things been slightly different we may have had two celestial bodies permanently lighting our night sky.....or it may have just passed through never to be seen again.

Edited by spaceboy
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Doing a quick check on this page, it looks as if it will not be easy ... looks as if it never going to get above 20 degrees from the NW horizon at sunrise from 5th - 14th December, and then returning to lower altitudes, peaking at mag 16.5. I guess it is a bit like comet-observing - if it crosses the earth's orbit when the earth is there, it is brighter and easier, if the earth is a long way away, it isn't so good.

Still, if it is a choice between now and "the next series of close approaches" (the late 2200's), I suggest you try now.

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Here's its orbit. Not really Earth's moon!

Orbits_of_Cruithne_and_Earth.gif

It's currently mag 16.8, and in the constellation Pyxis at -20 declination, rising at 03:30. Too low down for my setup!

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2 hours ago, LukeSkywatcher said:

Ive heard the name Cruithne before but thought it was an old Gaelic word/name for the "Moon".

 

If it orbits the earth (even if it is 800 years to do so) and it was earths gravity that made it do so, a "moon" it is..........in a very loose sense :D

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23 minutes ago, spaceboy said:

 

If it orbits the earth (even if it is 800 years to do so) and it was earths gravity that made it do so, a "moon" it is..........in a very loose sense :D

If the graphic posted above is accurate it is clearly eccentrically orbiting the Sun :wink:

 

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1 hour ago, spaceboy said:

 

If it orbits the earth (even if it is 800 years to do so) and it was earths gravity that made it do so, a "moon" it is..........in a very loose sense :D

What i meant was that i thought the ancients here in Ireland named our moon as Cruithne. I doubt whether they were referring to something that takes 800 yrs and is too faint to see, but rather the one we see in the sky today.

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All news to me?   This asteroid/second Moon at only 3 miles wide, fainter than Pluto and  over 7 Million miles out, its going to be hard to find!
Its suggested  that a telescope of  320mm / 12.5" scope  would be minimal?

There is an image of a dot( Cruithne) https://en.wikipedia.org/wiki/File:Cruithne.jpg taken from the Powell Observatory in 2001.  Built In 1984 they had a 30"  Mirror, a 16" scope and a 12" scope.
I had  issues finding M31 in the early Years, but now that I know exactly where to look, it takes seconds to locate, so what chance do I have, plus I'd need a BIGGER scope ✫

Edited by Charic
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As it goes around the Sun and Earth in many small circular orbits it also crosses the orbits of Mars and Venus, with it's spyrographic horseshoe yearly orbit  and at more than ten miles wide it's an extinction class object and will eventually be kicked loose and be flung out, impact or orbit another celestrial body and may even be replaced by another asteroid or comet. Horseshoe orbits are common in the solar system and Saturn has a few satellites using this type of orbit. Horseshoe orbits lack longevity and are some of the most unperdictable in the system so if You do have the scope and tracking ability it would be worth a look to see such a chaotic and dangerous object before its gone, or we are. :)

 

Edited by Aaron F Johnson
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One of these days, I might revisit VIDEO Astronomy! lol. At magnitude +15.8
(maximum) it should be quite possible to image it with my trusty 8" f/4 Newt. :p

Hey, Pluto is brighter(!), yet I suspect would be difficult to confirm - It being in
the dense star region of Sagittarius etc.  I have envisage an updated technique
(animated .gif ?) ... based on the "Blink Microscope" used to discover Pluto?!? :)

The challenges would be... Knowing where Cruithne is... That it would be in a
fairly sparsely populated star field... That we get two (or more) CLEAR nights! :D

FWIW, I was thinking of having a go at Minor Planets sometime... The latest
(Nov) issue of "Astronomy Now" has an article on NEOs (Near Earth Objects!)
by Martin Mobberly... Brighter and with documented positions for early Nov. ;)

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