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HOME, HOME ON LAGRANGE: EARTH FINDS ITS TRUE COMPANION?

by acanuck 7/27/2011 - 6:51 pm

Meanwhile, in non-debtpocalypse news, I read today that a Canadian-led team of astronomers has discovered Earth's "First Asteroid Companion," the as-yet-unnamed 2010 TK7.

Fascinating -- except that the headline is totally wrong. None of the articles I scanned today mention it, but we've known about another "asteroid companion" for nearly a quarter-century. It's called Cruithne (pronounced KROOeee-nyuh), and it orbits the sun in a somewhat more elliptical version of Earth's path.

Its year is synchronized within about a day of ours, with the result that it makes a close approach every November. It's also a far more substantial object than 2010 TK7 -- at roughly three miles in diameter, Cruithne is 15 times as wide and hundreds of times as massive. At one point, some were calling it "Earth's second moon," but that was clearly wrong, since it doesn't orbit our planet at all. Worth a google, though.

Ars Technica is one of the handful of publications that got today's story right, calling 2010 TK7 "Earth's First Trojan Companion." That's because, unlike Cruithne, TK7's orbit is linked to at least one of Earth's Lagrangian points. Ars Technica explains it nicely:

http://arstechnica.com/science/news/2011/07/astronomers-find-earths-first-trojan-asteroid.ars

An argument could be made that TK7 may not really be a Trojan, since it appears to wander between Lagrange 3 and 4, and its discoverers concede its orbit may not be stable or predictable beyond 250 years. Cruithne, on the other hand, appears to have co-orbited with Earth for at least a million years.

There are a bunch of smaller objects that also do weird horseshoe-shaped dances with Earth, and some even get temporarily captured into our orbit. Like I said, fascinating stuff.

So there it is. Hope this post took your minds temporarily off the debt-ceiling "debate." Damn those Republicans! Damn them to hell! Sorry, the celestial calming effect seems to wear off pretty fast. 

 

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Interesting. I just revisited Google News on this story, and lots more headlines now read "First Trojan" as opposed to this morning's "First Asteroid Companion." I didn't check how many mention Cruithne, but it's clear the initial reporting got some nerd feedback.

by acanuck 7/27/2011 - 7:03 pm

Thanks acanuck! It's a truly interesting story, and the bit about Cruithne is even more fascinating.

by Verified Atheist 7/27/2011 - 8:27 pm

What a rush!  Nice work Ack. smiley

by bslev 7/27/2011 - 9:22 pm

Lovely.  Yes,  I do feel better now.   Thanks for sharing.  I may take this as my screen name someday:  Cruithne (pronounced KROOeee-nyuh)

by Ramona 7/27/2011 - 10:34 pm

Best headline for this story.  Bravo!

by Johnny Cashed (not verified) 7/28/2011 - 3:32 pm

It's been a good week in the asteroid field. Launched nearly four years ago, the Dawn probe has finally parked itself off Vesta, and is sending back spectacularly detailed photos. After studying that asteroid for about a year, Dawn will head off toward the dwarf planet Ceres. Expect to see photos of it in 2015, assuming NASA's still in business.

by acanuck 7/28/2011 - 5:27 pm

Where do you stand on the Pluto question? 

Was going to ask you where you stood on Pluto, but that's cold.

by Articleman 7/30/2011 - 8:38 pm

Cold indeed. Until Pluto's demotion in 2006, I'd gotten pretty comfortable living in a nine-planet solar system. Problem was, another Kuiper Belt object -- initially called Xena, now officially Eris -- had been discovered three years earlier and it was slightly larger than Pluto.

So there were either 10 planets or there were eight, with Pluto and Eris being the first known members of a separate classification. As observations of the outer solar system rapidly improved, it was pretty clear the number of planets would keep growing forever unless Pluto took a pay cut. Clyde Tombaugh's family agreed, making it easier for the rest of us. It was the right decision.

As the poster boy and prototype for "dwarf planets" (called plutoids if they're outside Neptune's orbit), Pluto lent them all prestige. More are discovered every year: Quaoar, Haumea, Makemake, Varuna, Orcus and Sedna (the furthest such object yet spotted) are recognized or awaiting formal certification. It's estimated there are 200 or more.

Many of these objects have highly elliptical orbits. I won a $50 bar bet in the early '90s by challenging a loudmouth to name the furthest planet from the sun. At that time, Pluto's orbit happened to have taken it inside Neptune's. The guy changed bars.

 

by acanuck 7/31/2011 - 3:14 am (re: Articleman)

Nearly forgot: when the IAU rewrote the definition of "planet" in 2006, they briefly considered elevating Ceres (mentioned in the main post) to full planethood along with Pluto and Eris. That would have made the total 11 and counting. Instead, they all were dumped into the new category.

by acanuck 7/31/2011 - 3:37 am (re: acanuck)

I totally object to Ceres being a planet instead of a planetoid, not only because it is the largest fragment of the not-formed or destroyed terrestrial fifth planet, but because planets are worlds, and that would make it the world Ceres.  (rimshot)

I didn't know Tombaugh's family was cool with it.  It bums me out.  I spend time in Flagstaff, and started visiting Lowell Observatory in the 90s.  They used to let you use the device with which he discovered Pluto, which was a machine that switched two photo plates briskly so you could compare them.  In the two plates, which were replicas of those he used, you could see the white dot that moved against the stars, and in that, see in the same object how he discovered Pluto.

I always thought that was tremendously cool.

It is exciting that we're finding all these elliptically orbiting chunks of ice and rock out there past Pluto.  I liked the name Xena a lot, but I guess the official folks nixed that.  When I was a kid, I used to want to be an archaeologist or an astronomer, both things, oddly, that you can be in Flagstaff.  While losing Pluto is a downer, it does show that the new generation of kids can still find lots of neat things, which to me, since we can't exactly take tours of the Oort cloud in person, is a lot of what makes astronomy exciting.

by Articleman 7/31/2011 - 4:12 pm (re: acanuck)

For half a century after its discovery (mid-1800s), Ceres was considered by some to be the eighth planet (fifth from the sun, of course). Then astronomers realized that idea of Ceres as a world was off-base.

I'll admit the new criteria for planethood are really arbitrary. The IAU decided which objects they wanted to include, and wrote the rules accordingly. But like I said, they had to do it or leave the solar-system cast of characters forever in flux.

Yeah, Xena got nixed because she's a comic-book character, not a real deity. And the IAU does love its traditional naming rules. At least they've opened up the process to gods that aren't Greek or Roman (Haumea and Makemake are Hawaiian).

It's cool that you actually got to look through Tombaugh's device. Most of the new discoveries result from an e-database version of that technique. Mike Brown at Caltech is tops at finding dwarf planets, and I noticed that a team at obscure little Athabasca University, in Alberta, got credit for finding TK7. They're big on IT, and I figure a lot of student exercises involve number-crunching of data from major observatories.

One thing on my bucket list is to visit the Griffiths Observatory in L.A. to see the Big Picture, a 150 foot by 20 foot photo-mosaic of a tiny slice of sky, taken by the Palomar telescope. Here's a link (blow the image up to full screen on a high-res monitor or TV, and scroll):

http://bigpicture.caltech.edu/explore.htm

by acanuck 7/31/2011 - 5:11 pm (re: Articleman)

Seeing those galaxies on the Big Picture reminds me of why I liked science fiction so much as a kid.  Don't tell me there's no one out there.

by Articleman 7/31/2011 - 5:16 pm (re: acanuck)

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