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Earth Acquires a Quasi-Moon
richard_za writes "Earth has acquired a so called quasi-moon, an asteroid: 2003 YN1, which will encircle us for the next couple of years while it orbits the sun on a horse-shoe shaped path. Full story on News24. It was found by team led by Paul Chodas, an asteroid specialist at Nasa's Jet Propulsion Laboratory in California. An orbit simulation can be seen in this Java applet."
Here's a link to Discovery Channel's coverage without the need for registration.
Mike
I think the "moon" label is very inaccurate. It's not orbiting anything but the Sun. It's also, as you noted, much farther away than our own moon. According to the Java applet (which is pretty cool, btw) the asteroid will be on the other side of the sun for a lot of the time (and even outside the orbit of Mars).
Catchy, but misleading headline. Still pretty neat, though.
And this is a dupe from 4 years ago.
Earth's Second Moon 2nd Moon Orbiting Earth Discovered
There is an entire branch of astronomy that uses distributed observations to map the size and shapes of asteroids using occultations (eclipses with distant stars). When an asteroid passes in front a distant star, the star winks out and then reappears. Knowing the duration (start and stop times) of the occultation, the location of the observer, and the orbits of the Erath and asteroid lets people estimate the size and shape of the asteroid. International Occultation and Timing Association collects data from telescopes around the world (many in the hands of hobbyists) and uses the data to make these estimates.
Two wrongs don't make a right, but three lefts do.
This is the third asteroid we've found which has an orbit tied loosely to that of the Earth. The others are 3753 Cruithne and 2002 AA29. You can see pictures and applets and read about these other bodies at Paul Wiegert's web site:
http://www.astro.uwo.ca/~wiegert/
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The kind that you wouldn't be able to detect (except maybe by careful monitoring of the sun with a well-filtered telescope pointed at exactly the right spot). Imagine something much smaller than the moon and even farther away passing in front of the sun. That's what this is.
To experience a solar eclipse from a temporary sattelite would be a once-in-a-lifetime experience.
If it were noticeable. But temporary satellites (like the ISS) cast (highly-attenuated) shadows on the Earth every day.
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Our plain old moon orbits the sun, too. The sun pulls on it with twice the force of the Earth. The Earth merely perturbs the moon's orbit around the sun enough to make it look wobbly. In fact I just found out that Earth's moon is unique in this respect by reading this page about planets and moons!
What a fool believes, he sees, no wise man has the power to reason away.
According to the article, the magnitude is around 24. The best the human eye can see is about magnitude 5 given excellent conditions.
:
It is essentially invisible unless you have a decent research telescope.
More info on the astronomical magnitude scale can be found here
http://cfa-www.harvard.edu/icq/MagScale.html
I can't get to the applet, but I suspect both are correct.
You're very likely looking at a projection from above. Pluto's orbit is tilted about 30 degrees, so, from above, it will look closer than Neptune, but if you ran a tape measure out in a 3d universe, you'd see it was farther.
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Actually, believe it or not Luna's orbit is also more influenced by the Sun than the Earth -- if you trace out its path relative to the Sun, it makes an ellipse, not a ... bleah, forget the name of the shape. Anyway, there aren't any loops in evidence.
From a mathematical standpoint, it would be more appropriate to say that Luna orbits the Sun, rather than that it orbits the Earth.
That said, the Earth+Luna system still has a combined center of gravity which lies beneath the Earth's surface, so in that sense at least Luna is still Earth's satelite.
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