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."

no reg link...

[sweeney37]

Here's a link to Discovery Channel's coverage [discovery.com] without the need for registration.

Mike

Re:So it's not a threat

[lukewarmfusion]

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.

Isn't it Cruithne???

[Pig Hogger]

Doesn't the Earth already has a second moon, Cruithne [burtleburtle.net]???

And this is a dupe from 4 years ago.

Earth's Second Moon [slashdot.org] 2nd Moon Orbiting Earth Discovered [slashdot.org]

Re:Isn't it Cruithne???

[Geoffreyerffoeg]

According to the Discovery Channel article linked elsewhere, 2003 YN17 is at least the fourth moon. The three others are the real moon (Luna, as some call it), Cruithne, and 2002 AA29.

Have the other two left already/have there been others in the past?

Re:Obligatory SW Quote

[aceat64]

SW = Star Wars. I hope you were joking, because that's just sad.

Re:I wonder... (distributed astronomy)

[G4from128k]

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 [lunar-occultations.com] collects data from telescopes around the world (many in the hands of hobbyists) and uses the data to make these estimates.

Not the first "quasi-moon" for Earth

[StupendousMan]

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/ [astro.uwo.ca]

Re:I wonder...

[tverbeek]

What sort of eclipse can we expect from this?

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.

Re:"Our" moon?

[bunratty]

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 [challenger.org]!

Re:Is it visible?

[dtl]

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

Does the applet have correct orbits?

[Ephboy]

I was looking at the orbits of Pluto and Neptune on the applet, and noticed that Pluto is shown as inside Neptunes orbit at present and until 2011, but I was under the impression that Pluto was once again the farthest planet, as of 1999 [nasa.gov], and wouldn't pass in again until 2226. So I'm not sure their orbits are correct....

Re:Horseshoe?

[Guppy06]

Nah, he'd still be scratching his head at the whole "precession of Mercury" thing.

Re:Does the applet have correct orbits?

[yotto]

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.

Re:Isn't it Cruithne???

[Pooua]

Have the other two left already

No, Cruithne is projected to be in our neighborhood for thousands of years.

"Earth has a second moon, of sorts, and could have many others, according to three astronomers who did calculations to describe orbital motions at gravitational balance points in space that temporarily pull asteroids into bizarre orbits near our planet.

"The 3-mile-wide (5-km) satellite, which takes 770 years to complete a horseshoe-shaped orbit around Earth, is called Cruithne and will remain in a suspended state around Earth for at least 5,000 years."

Space.com: More Moons Around Earth? It's Not So Loony [space.com]

Re:uh wha'zat?

[MenTaLguY]

Actually the horseshoe shape is only its path relative to Earth. Its path relative to the sun is much more mundane.

Re:So it's not a threat

[MenTaLguY]

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.

er, one question here,

[pair-a-noyd]

"while it orbits the sun on a horse-shoe shaped path"

Uh, wouldn't it be easier to fly an elliptical orbit?

Correct simulator link & other links

[waynegoode]

The simulator link is incorrect. It points to 2004 YN1. The correct link [nasa.gov]. For a good view in the simulator, tilt the 3D view to straight down, center on earth and zoom in all the way.

New Scientist has an interesting article [newscientist.com] in their latest issue.

For a more technical explanation, read the paper [usra.edu] presented at the Lunary Planetary Science Conference [usra.edu] last week.

Re:Is it visible?

[luna69]

I've seen down to a little better than m=6.8 in dark skies, and given the magnitude scale's logarithmic nature, that's a fair bit better than m=5. From cities, it's often impossible to see much better than m=3 or so.

With a little more specificity, if this object is m=24, then it's about (24-7)=17 magnitudes fainter than the *best* that the human eye can do. To put that into perspective, given that five magnitudes of difference is about 100x difference in actual brightness (~2.5^5), a difference of 17 magnitudes is *roughly* 5.8E6 (2.5^17) times fainter than the human eye is capable seeing in optimal, dark-sky conditions.

Also, see: International Dark-Sky Association [darksky.org]

I need to get out more...

[troon]

The picture on the Discovery Channel coverage [discovery.com] is not the asteroid in question. I know this means I need to get out more, but I instantly recognized that picture as 243 Ida [nineplanets.org] and its tiny satellite Dactyl.

Re:space station

[Catbeller]

You've described the mass driver, the standard asteroid/ore moving workhorse of the O'Neill/L5 space colonization effort.

It works like this: picture a bucket on a recirculating rail. The rail is pretty long, hundreds of feet at least. The bucket meglevs along the rail.

There would be at least three railguns on the asteroid, pointing away from the asteroid in opposing directions. Actual orientation is not that important, what is important is that the rails point away.

In operation, the "bucket" stops at a point along the rail on the surface of the asteroid. Some mechanism plonks a pound or so of rock into the bucket. The bucket locks the material down.

The bucket now electromagnetically moves away to the railgun run. On reaching it, it accelerates. At an approprate time, it releases the payload. The bucket slows down, and returns to the loading point.

The process changes the the path of both the payload (reaction mass) and to the asteroid itself. Repeat this process millions of times, and you alter the asteroid's orbit.

The beauty part of a mass driver is that it has no moving parts in contact. You just need something to shovel in the reaction mass, and electricity to run the linear accelerators.

Asteroids can be moved in this manner. Rockets won't hack it, nor ion engines, nor nuclear explosions. Lack of control, or raw power.

We could shape the orbits of these Earth grazers to bring them a little closer to home so that we can exploit them for raw materials to build habitats, build ships, build elevators.

Space elevator projects require a large mass at the opposite end of the tether from the surface to anchor the cable. Asteroids have been suggested for the necessary mass. Mass drivers are the way to go if you want to get that mass.