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Thu May 30, 2013, 08:52 PM

Surprise, Asteroid 1998 QE2 has a moon!

From Universe Today:

Late yesterday, NASA turned the 230-foot (70-meter) Deep Space Network antenna at Goldstone, California toward Asteroid 1998 QE2 as it was heading toward its closest approach to Earth, and they got a big surprise: the asteroid is a binary system. 1998 QE2 itself is 1.7 miles (2.7 kilometers) in diameter, and the newly found orbiting moon is about 600 meters in diameter.

The radar images were taken were taken on May 29, 2013, when the asteroid was about 3.75 million miles (6 million kilometers) from Earth.

“Radar really helps to pin down the orbit of an asteroid as well as the size of it,” said Paul Chodas of NASA’s Near-Earth Object Program office, speaking during a JPL webcast about this asteroid on May 30. “We now know our size estimates were pretty good, but finding it was a binary was surprising.”

NASA said that about 16 percent of asteroids are binary or even triple systems.



Radar images from May 29, 2012 of Asteroid 1998 QE2,
showing its binary companion. Credit: NASA.


Wow! I wonder if it's made of green cheese, just like Earth's moon???

The following is a sequence of radar images recorded by NASA's Deep Space Network antenna in Goldstone, Calif., showing the rotation of asteroid 1998 QE2 plus its moon, visible as a bright spot. Credit: NASA / JPL-Caltech / GSSR


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Response to DreamGypsy (Original post)

Thu May 30, 2013, 08:55 PM

1. Who knew something that small could have a moon!

I'm amazed...

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Response to CaliforniaPeggy (Reply #1)

Thu May 30, 2013, 09:16 PM

3. Gee, I'm a lot less than 1.7 miles in diameter ...

...and I have a moon. Not observed by a lot of people, I hope...my parents, my wife, I guess a bunch of guys in the showers after PE. I have no idea how it would appear to radar...?

But seriously, CA-Peggy, you have a good point.

I searched on "smallest moon" and found this, What is the smallest moon in the solar system?:

There are hundreds of Moons that are around 10 kilometers or less in diameter. Mainly in orbit around Jupiter or Saturn.

Jupiter's smallest moon is probably S/2003 J 12 or S/2003 J9 at only 1 kilometer in diameter.

Saturn's smallest moon is probably Aegaeon at only 0.5 kilometer in diameter - although it is classified as a moonlet.

If you don't want the moon to be around a planet, the Asteroid IDA (243 IDA) has a tiny moon called Dactyl which is under a kilometer in diameter.


So, Aegaeon wins as the smallest known moo(let), at 500 meters in diameter. The unnamed moon of Queen Elizabeth 1998 is apparently second.


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Response to DreamGypsy (Reply #3)

Thu May 30, 2013, 09:19 PM

4. Thank you for looking that up. It's fascinating!

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Response to DreamGypsy (Original post)

Thu May 30, 2013, 09:08 PM

2. Surprise, 1998 QE2 is a "planet" according to the In't Astrological Union (IAU) definition.

Scroll down to the bottom of the post here: http://www2.ess.ucla.edu/~jlm/epo/planet/planet.html

Apparently it has sufficient mass to retain its own satellite, which is surprising. Both of them are soon to be visiting our part of the solar system.

The fact that it has a moon shows that 1998 that it has "cleared its neighborhood" of other objects, and is is a full-fledged planet, according to another IAU definition: http://en.wikipedia.org/wiki/Clearing_the_neighbourhood

"Clearing the neighbourhood of its orbit" is a criterion for a celestial body to be considered a planet in the Solar System. This was one of the three criteria adopted by the International Astronomical Union (IAU) in its 2006 definition of planet.[1]

In the end stages of planet formation, a planet will have "cleared the neighbourhood" of its own orbital zone, meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence. A large body which meets the other criteria for a planet but has not cleared its neighbourhood is classified as a dwarf planet. This includes Pluto, which shares its orbital neighbourhood with Kuiper belt objects such as the plutinos. The IAU's definition does not attach specific numbers or equations to this term, but all the planets have cleared their neighbourhoods to a much greater extent than any dwarf planet, or any candidate for dwarf planet.

The phrase may be derived from a paper presented to the general assembly of the IAU in 2000 by Alan Stern and Harold F. Levison. The authors used several similar phrases as they developed a theoretical basis for determining if an object orbiting a star is likely to "clear its neighboring region" of planetesimals, based on the object's mass and its orbital period.[2]

Clearly distinguishing "planets" from "dwarf planets" and other minor planets had become necessary because the IAU had adopted different rules for naming newly discovered major and minor planets, without establishing a basis for telling them apart. The naming process for Eris stalled after the announcement of its discovery in 2005, pending clarification of this first step.


This could change the way we view planetary systems, or that moon could just be an interstellar craft in a parking orbit.

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Response to leveymg (Reply #2)

Thu May 30, 2013, 09:50 PM

6. When did the IAU declare 1998 QE to be a dwarf planet?

Yes, it has a moon. But that's not enough. Wikipedia currently asserts that:

Ceres, minor-planet designation 1 Ceres, is the only dwarf planet in the inner Solar System, and the largest asteroid. It is a rock–ice body 950 km (590 mi) in diameter, and the smallest identified dwarf planet.


1998 QE2 is only 1.7 miles in diameter. It looks round-ish, from the radar images. But is it round enough to determine that it has assumed hydrostatic equilibrium? Do we know that it has cleared its neighborhood? Does its orbit avoid the orbits of all other more massive asteroids so it can assert gravitational dominance?

I'm awaiting the official word from the IAU.

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Response to DreamGypsy (Reply #6)

Thu May 30, 2013, 09:58 PM

7. It seems to meet both definitions: 1) round(ish), 2) cleared its orbit. As for 3) if it hasn't

avoided the orbit of other more massive asteroids, it would itself be in orbit.

I'd argue it's a planet.

The fact that it appears to have a moon is extraordinary. Almost off the charts.

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Response to leveymg (Reply #7)

Thu May 30, 2013, 10:24 PM

9. Argue as you will ...

...but as QE's orbit changes due to occasional passes near earth, or other large bodies, will some future path bring her into close conjunction with Ceres? If so, who will win?

Only the computer analysis knows for sure.

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Response to leveymg (Reply #7)

Fri May 31, 2013, 12:21 AM

12. Except it hasn't cleared its orbit.

There's this little body of rock called Earth nearby. It needs to clear the complete solar orbit to meet the specifications, not just the immediate area.

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Response to Angleae (Reply #12)

Fri May 31, 2013, 06:57 AM

14. There's only one ("trojan") asteroid we know is in earth orbit, and this isn't it.

See, http://www.pbs.org/newshour/rundown/2011/07/trojan-asteroid-synced-in-orbit-with-earth.html

If 1989 QE2 were in planetary orbit, I'd agree with you. If it's not in orbit around another body other than the sun (that we've been able to determine), and has a satellite of its own, then how has QE2 not cleared its orbit?

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Response to leveymg (Reply #14)

Fri May 31, 2013, 07:00 AM

15. It has to clear it's own orbit of all bodies that would have a significant gravitaional effect on it

This is the reason Pluto isn't a planet any more. It hasn't cleared everything significantly larger that it from it's orbit, most notibly Neptune.

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Response to leveymg (Reply #7)

Fri May 31, 2013, 03:23 AM

13. Pluto has moons; it has not cleared its orbit, and is not an IAU planet

and neither is QE2. Its orbit crosses that of Mars and the asteroid belt. Not only does it have close encounters with Earth (<0.04 AU), it has them with Vesta too (<0.02 AU): http://echo.jpl.nasa.gov/asteroids/1998QE2/1998QE2_planning.html

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Response to DreamGypsy (Original post)

Thu May 30, 2013, 09:21 PM

5. Time for a (Jonathan) Swiftie…

So, naturalists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller still to bite 'em;
And so proceed ad infinitum.

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Response to Jackpine Radical (Reply #5)

Thu May 30, 2013, 10:06 PM

8. Ah, Swiftie's, I know your Jonathan, but the ones I favor are Tom ...

...Tom Swifties.

"Who left the toilet seat down?" Tom asked peevishly.
"They had to amputate them both at the ankles," said Tom defeatedly.


History

While their exact origins remain uncertain, the spread of Tom Swifties in the United States was abetted by an article in the May 31, 1963 edition of TIME Magazine, which also announced a contest for its readers to submit their own Tom Swifties. Included was a special category, "TIME Swifties," which were to contain a reference to TIME Magazine;[2] however, only a few submissions were made of this nature. Among the submissions that were subsequently printed was "Someone has stolen my movie camera!" Tom bellowed and howled.

The TIME contest caused the popularity of Tom Swifties to grow, for a period of some years. Tom Swifties found a large teenage audience on the joke column on the last page of each month's issue of Boys' Life, the magazine for Boy Scouts.


There are two Tom Swifties that I remember well, because ... I think...I was the originator. Both are about toothpaste. Is that weird or what?

"Oh, I dropped my toothpaste" said Tom, crestfallen.



"Ahh!! My toothpaste tube exploded!!!" said Tom with a gleem in his eye.

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Response to Jackpine Radical (Reply #5)

Thu May 30, 2013, 11:05 PM

10. +1000

 

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Response to DreamGypsy (Original post)

Thu May 30, 2013, 11:57 PM

11. Maybe that isn't a moon.

Maybe that's a spaceship. Maybe that was what the Heaven's Gate cult was waiting for. Maybe they confused Asteroid 1998 QE2 for the Comet Hale–Bopp.

But, maybe not. Who knows what's in the minds of religious cultists.

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