Starship Asterisk*

by **bison** » Wed Mar 31, 2010 10:35 pm

A good deal has happened with the P/2010 A2 (LINEAR) story since early February. For starters, the tail and the peculiar X-shaped pattern at its end have held their shape remarkably well, refusing to be scattered by the the force of the explosive collision supposed to have created them, or by the Solar wind. The tail, which was supposed to be driven away from the Sun, like that of a comet, has recently been photographed pointing almost directly AT the Sun. Dr. David Jewitt, who has now photographed the object several times with the Hubble Space Telescope has declined to release any of the images, beyond the first one. No explanation has been offered for why the debris of a collision should not be spherically distributed, how a narrow tail could have formed, why the supposed debris has not smeared out the complex structure it contains, or why the object's brightness has gone up, down, and up again, rendering it recently as bright as it was at the time of its discovery, over two and a half months ago. Ross

by **Lasse H** » Fri Feb 12, 2010 3:49 pm

Thank you very much! Very educational.
Lasse

by **Chris Peterson** » Fri Feb 12, 2010 3:13 pm

Lasse H wrote:
Chris Peterson wrote: ... At the distance to the object, each pixel is subtending a 20,000 km area ...
I don't understand this (but I hope I will if I get an explanation): In the tail 'each pixel' = '20,000 km' ? That would make the tail of this object billions of kilometers long. Not to mention the small nucleus itself, which is said to be only 140 meters in diameter, and yet seems to be composed of maybe hundreds of pixels.

It looks like I switched meters for kilometers when I did my calculation. The UVIS WFPC3 camera used for this image has a pixel scale of 0.04 arecseconds, and the distance to the object was 144 million kilometers. So each pixel subtends an actual distance of 28 km at the distance to the object. That makes the imaged portion of the tail some 70,000 km long. (Even if the scale were 20,000 km per pixel, however, the tail would only be tens of millions of kilometers long, which is very typical of small comets.)

At 28 km per pixel, no individual object in this image is resolved. The remaining fragment, estimated at 140 meters in diameter, is completely unresolved- much smaller than a single pixel. It only appears to cover tens of pixels because of diffraction in the optics. The size of the nucleus was estimated based on its brightness, and an assumed albedo. That's how the sizes of most asteroids are determined- very few are large enough to be resolved optically.

by **Lasse H** » Fri Feb 12, 2010 11:22 am

Chris Peterson wrote: ... At the distance to the object, each pixel is subtending a 20,000 km area ...

I don't understand this (but I hope I will if I get an explanation): In the tail 'each pixel' = '20,000 km' ? That would make the tail of this object billions of kilometers long. Not to mention the small nucleus itself, which is said to be only 140 meters in diameter, and yet seems to be composed of maybe hundreds of pixels.

Lasse

by **BMAONE23** » Mon Feb 08, 2010 5:52 pm

It reminds me of those things hanging from the trees in "Blair Witch"

by **Rubie** » Mon Feb 08, 2010 4:13 pm

It looks more like a V to me.. I dont see the X.

by **bystander** » Mon Feb 08, 2010 12:04 am

Mystery "X" Stands For "X-traterrestrial" to Some Believers
Discovery Space News - 2010 Feb 07

When Hubble Space Telescope first photographed the strange comet-like object p/2010 a2 I just knew it would get attention among the X-Files crowd.

The "X" pattern of dust debris, presumably from an asteroid collision, is simply arresting.

Last week's release of the Hubble picture spurred a lot of spirited speculation on Internet discussion boards that the "X" was something other than a natural phenomenon:

by **Rubie** » Sat Feb 06, 2010 10:08 pm

I think it looks like it totally just changed pathes, for some unknown reason. enjoy the inverted view

I was diggin it. hah

by **bystander** » Fri Feb 05, 2010 5:50 pm

Well, Oldfarts deserve a little coddling. There are quite a few of us here. But orin is still the Resident Geezer.

by **Oldfart** » Fri Feb 05, 2010 4:48 am

Chris, yes, that makes sense. I was interpreting the pixtelization (is that a word?) plus maybe some high-contrast processing of the image as showing a bunch of big rocks hurtling through space. I feel better now...

Thanks for being so patient!

Don

by **Chris Peterson** » Fri Feb 05, 2010 3:57 am

Oldfart wrote:It was my notion that the Hubble photo resolved the tail, showing that it was comprised of thousands of individual points of light, and I assumed that each little point of light resulted from sunlight reflecting from an object like a rock or something. You seem to suggest that these objects could actually be quite small, perhaps centimeter-size pebbles or even smaller. Is that right? If so, I guess I was just WAY underestimating Hubble's ability to see tiny things that far away.

The tail is, indeed, resolved. What that means is that we are able to see structural detail, because the size of the entire tail is much greater than the minimum resolution of the optics and camera. But it doesn't mean that the individual particles that make up the tail are resolved (any more than you resolve the molecules in the dyes that make up pixels on your computer screen, even though you clearly resolve each character of my response). In the case of nebulous objects like comets or asteroidal debris trails, we are able to image (or even see visually) structure because there is so much material. The Hubble camera certainly would not be able to detect a single 1cm particle at that distance. But each pixel is actually recording the light reflected off of thousands, millions, or billions of particles. At the distance to the object, each pixel is subtending a 20,000 km area (and an infinite depth, of course, but we really only care about the depth through the tail). That's a very large volume of space. Hope that makes sense.

by **geckzilla** » Fri Feb 05, 2010 3:30 am

I think your initial hunch was correct, Oldfart. Chris was just making sure you were making the distinction between detecting and resolving. The grain present in the image is evenly distributed and perceived granules in the tail are probably just part of that grain.

by **Oldfart** » Fri Feb 05, 2010 3:20 am

Chris, thanks for trying to help me figure out what's going on here. I say "trying", because I'm still a bit fuzzy about this. As in:

It was my notion that the Hubble photo resolved the tail, showing that it was comprised of thousands of individual points of light, and I assumed that each little point of light resulted from sunlight reflecting from an object like a rock or something. You seem to suggest that these objects could actually be quite small, perhaps centimeter-size pebbles or even smaller. Is that right? If so, I guess I was just WAY underestimating Hubble's ability to see tiny things that far away. Thanks for clarifying!

Don

by **Chris Peterson** » Thu Feb 04, 2010 8:01 pm

Oldfart wrote:The tail of this object is evidently comprised of many chunks of stuff large enough to be individually detected by Hubble. I don't know what size rocks can be resolved by Hubble at this distance, but it's pretty evident that these are big rocks. If so, how could the whimpy light pressure from the sun affect them so strongly that they were forced to group into a compact, well organized tail? Doesn't make sense to me...

There is a big difference between being able to detect something and being able to resolve it. None of the material from this object is large enough to be resolved by Hubble's camera. But there are thousands or millions of individual components bright enough to be detected. Even fine dust that is lit by the Sun is easily detectable. Material smaller than about a centimeter is highly affected by both the solar wind and by radiation pressure.

by **Oldfart** » Thu Feb 04, 2010 5:25 am

The tail of this object is evidently comprised of many chunks of stuff large enough to be individually detected by Hubble. I don't know what size rocks can be resolved by Hubble at this distance, but it's pretty evident that these are big rocks. If so, how could the whimpy light pressure from the sun affect them so strongly that they were forced to group into a compact, well organized tail? Doesn't make sense to me...

Don

by **NoelC** » Thu Feb 04, 2010 4:23 am

How much of that Hubble image granularity is just plain grain in a noisy photo and how much is actual space grit reflecting light, I wonder.

Would be nice to see another image. Is this bright enough for a ground based shot? Granted, it's probably not very big.

-Noel

by **lobcod** » Thu Feb 04, 2010 2:12 am

Your theory is plausible, but if you look very closely, you will clearly see the cloaked outline of a Klingon Bird of Prey. We are not alone!!

by **bystander** » Thu Feb 04, 2010 12:33 am

Bad Astronomy: Hubble captures picture of asteroid collision!

Now, let me just take a moment and say HOLY HALEAKALA WHAT WE’RE SEEING HERE IS THE COLLISION BETWEEN TWO PREVIOUSLY UNDISCOVERED ASTEROIDS THAT EXPLODED LIKE THERMONUCLEAR WEAPONS WHEN THEY IMPACTED!!!

Phew. OK, I feel better. I needed to get that off my chest.

by **keshlam** » Wed Feb 03, 2010 11:32 pm

alfredogracia wrote:It looks like a Klingon Battlecruiser...

... or perhaps an old-fashoned bottle-with-fins rocket. If so, the vapor trail would mark the path of its retrorocket exhaust (which it would have been falling into, after all) and the bright spot at the tip of the "fin" is actually light from an attitude jet (which explains why it isn't lined up as one would expect if it had been firing retros; it rotated for some reason and is now controlling that rotation).

No, I don't think so. Humans are too darned good at picking out plausible patterns in random noise. But it can be entertaining to play "what if".

by **alfredogracia** » Wed Feb 03, 2010 9:27 pm

It looks like a Klingon Battlecruiser...

by **neufer** » Wed Feb 03, 2010 9:07 pm

geckzilla wrote:So what are the chances of actually figuring out what happened to the asteroids?
How long ago do we suppose they collided?

Well, I'm sure folks are frantically searching archived data to see when the tail was first visible.

Future Hubble images of the evolution of the "X" pattern should also be useful.

P/2010 A2 is close to Mars so you might want to check out Wally's astronomical photo.

Orbit and position of Comet P/2010 A2 (LINEAR).
Image created with the program C2A. Credit: Carl Hergenrother.

The Dawn spacecraft is about 4 times closer than us to P/2010 A2
and should remain close to P/2010 A2 for quite a while as it converges on Vesta.
I wonder if they are taking any pictures.

When (and if

) Dawn reaches Vesta it will be interesting to see how cratered Vesta is.

by **geckzilla** » Wed Feb 03, 2010 8:07 pm

...Except that The Sun likes to try to convince people that aliens are in town every chance it gets, including this one, even though there's never a shred of evidence. Makes money. Whatever you do, do not read the comments posted after the article. I think they will osmose bits of your brain through your skull just by being exposed to them.

So what are the chances of actually figuring out what happened to the asteroids? How long ago do we suppose they collided?

by **il2** » Wed Feb 03, 2010 7:54 pm

I did send a note to The Sun to try and verify where they obtained the information in the story. I just thought it was weird that the text in their story was transposed from the APOD story. And when I didn't see Mr. Jewitt mentioned in the story, I was a little concerned. I don't want to be "that guy" who complains and this is the first I've ever done so, but I don't believe it's right to run a story without properly citing it, especially when it comes to someone's discovery.

In the end, I'm glad to see they ran the story...the more exposure this type of science is given, the better.

by **neufer** » Wed Feb 03, 2010 5:29 pm

wwooten wrote:Back in October 2007, I thought this is exactly what happened to Comet Holmes, based on the sudden brightening of Comet Tempel II when hit by Deep Impact years before. Perhaps an object no bigger than a large building hit Holmes, and the debris blew off pointing away from us, so we do not see the long tail that this angle of impact produced.

It seems to me likely that Comet Holmes collided with
a former (broken off) piece of itself both in 2007 & back in 1892.

http://en.wikipedia.org/wiki/Comet_Holmes wrote:
Comet Holmes was discovered by Edwin Holmes on November 6, 1892 while he was conducting regular observations of the Andromeda Galaxy (M31). Its discovery in 1892 was possible because of an increase in its magnitude similar to the 2007 outburst; it brightened to an approximate magnitude of 4 or 5 before fading from visibility over a period of several weeks.

Comet Holmes:
Code: Select all
Aphelion distance: 	  5.183610 AU
Perihelion distance: 	2.053218 AU
Semi-major axis: 	    3.618414 AU
Inclination: 	       19.1126°

However, since the 2007 Holmes outburst took place shortly after (the May 4th)
Holmes 2.05 AU perihelion passage one can now envision Holmes having possibly
collided with a high inclination piece of Flora asteroid debris in the inner belt:

http://asterisk.apod.com/vie ... ra#p115226

by **ColoradoSky** » Wed Feb 03, 2010 5:09 pm

It will be interesting to watch the trajectory of debris in the next few months. Will our relative orbits allow Hubble to get a few more shots?

The picture is even better rotated 180 degrees, imho

Starship Asterisk*

APOD: P2010 A2: Unusual Asteroid Tail ... (2010 Feb 03)

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