Comet Holmes

MeteorWayne · Nov 25, 2007

Basically the same one since discovery in 1892, and most likely quite a few thousand years before that <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

3488 · Nov 25, 2007

Yes, although only a small nucleus approx 3.4 KM across, it still has a mass of billions of tons, so although outgassings & jets may look spectacular, they are way too weak to significantly change the orbit of Comet Holmes. The orbit will not change significantly for millenia yet. The biggest influence will be Jupiter's gravity. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

adrenalynn · Nov 25, 2007

Yuppers. I try to be fairly technically accurate so I don't get taken to task. Hence the "near enough" comments. I noticed you CYA'd too, with the "Basically". <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

Testing · Nov 25, 2007

Up in the Owens Valley over the weekend. Very good sky. My second best site. Could just make out Holmes naked eye and good view with binocs against the full Moon. Will be tough soon. <div class="Discussion_UserSignature"> </div>

adrenalynn · Nov 26, 2007

Yeah, between the water vapor and the full moon, I haven't even bothered the open the observatory up in the last week and change... <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

rule303 · Dec 1, 2007

"Yup! Same one (near enough) it was on 7 years ago, give or take." Wow, I never thought Id get a chance to use this, but at a period of roughly 7 years, that gives Holmes a semi-major axis of 3.65 AU, rounded to 4, an aphelion distance of 8 AU, putting it at furthest distance nearly 1 AU from the orbit of Saturn. I hope this is right, Kepler never lied to me yet...

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MeteorWayne · Dec 1, 2007

Sorry, your numbers are off. semimajor axis (a) is 3.617468 AU You don't just double it to get aphelion you must use the eccentricity (e), which is 0.432429 This gives perihelion of 2.053 AU, and aphelion of 5.18 AU That means it orbits in the asteroid belt between Mars (1.52 AU) and Jupiter (5.20 AU) MW Perihelion= a(1-e), aphelion= a(1+e) <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

rule303 · Dec 1, 2007

Awesome...Thanks meteorwayne. Sorry about the bad number crunch. I thought it seemed a bit far at first. I will remember this now. -Steve

MeteorWayne · Dec 1, 2007

No problem I knew all that quite a while ago, and dug it back up when I was reseraching the "Is Pluto a Planet?" issue. I calculated aphelion and perihelion for all solar system bodies larger than 250 km in diameter. Or rather, excel calculated them after I told it how <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

rule303 · Dec 1, 2007

Just one more question...Can you calculate the eccentricity from Kepler alone? If I can get the semi-major axis, how can I know its perihelion in order to complete the equation e=f/a? For example, using the period of 7 years, we get: 49=a cubed then 49=3.659 Getting this far, how could I get the number needed to complete Perihelion=a(1-e) and aphelion= a(1+e)? I've been mulling this since I read your response <img src="/images/icons/smile.gif" /> Thanks, -Steve

MeteorWayne · Dec 1, 2007

No you need the semimajor axis and the eccentricity. Kepler only shows the speed of travel along the orbit. Of course if you have any 2 of the 4 items (semimajor axis, eccentricity, perihelion or aphelion), you can calculate the others. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

adrenalynn · Dec 9, 2007

We had an absolutely BEAUTIFUL night last night. Alas, I was busy for most of it. No time to get set-up for imaging. My skies were approaching visual 6 magnitude, with uncountable stars. I recovered Holmes with but a moment's search with the naked eye (now well below Mirfak), and with averted vision was able to distinguish a tail. With my little 8x30 pocket binoculars, averted vision provided quite the elongation. Magnitude is very difficult to estimate because of the diffusion. I think a system like that used for nebula (collected light from the entire nebula summed together to give the overall magnitude) would have to be applied - and I've never been all that great at estimating that. Orion Nebula is an accepted Mag 4, so I'd say our comet was something like a mag 3.5-3.75 I'm uncertain that I have enough focal reduction to capture the whole thing anymore through the 'scopes. Very large and diffuse. If we have another clear cold night tonight, I'll try to photograph it as a mosaic. Following that, it's about time to go hunting for 8P/Tuttle! Good comet season coming up! <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

3488 · Dec 9, 2007

Hi Adrenalynn, I caught sigt of Holmes briefly too last night. Holmes is well below Mirfak now. In the 7 X 50s although rather large & none too easy to see (the contrast appeared very low), the elongation was very pronounced. Tonight, forget it, its overcast. <img src="/images/icons/frown.gif" /> Here is a nice image from Hungary. As you say, 8P/Tuttle is brightening up. <img src="/images/icons/laugh.gif" /> Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

adrenalynn · Dec 9, 2007

Great shot! Thanks for posting it. I hope I can do it justice from here tonight. So far we have some light cirrus clouds. I'm hopefull it's blowing out, not in. Haven't checked the forecast yet. (no clouds but poor to average seeing until 2200hrs (which means front yard which means street lights... after that, it appears I may have fog blowing-in again. Sigh. ) Latest reports I've seen for Tuttle are Mag 9.6. Well within reach of the 5" coupled to the 20D from my home observatory. (14.6 average limiting magnitude) <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

adrenalynn · Dec 9, 2007

I just went and looked at Tuttle on the charts for the first time. Little thing is moving along at a good clip. And will presistently stay right over the streetlights for me. Grrr. Should still be imageable though. Great pointer-star, it's traversing right near Er Rai in Cepheus. In fact, Cepheus will make an arrow that points almost right at it for the next few days. Er Rai is about a magnitude 3. It's about 45 degrees (give or take) high in my sky 24hrs/day. Here's a chart image containing Holmes and Tuttle @ 20:30hrs from my QTH tonight: Chart of Tuttle and Holmes at 20:30hrs Dec. 9, 2007 from Sac. CA. USA <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

adrenalynn · Dec 10, 2007

Doh! Me thinks I was looking at Monday night, not Sunday night. <img src="/images/icons/blush.gif" /> Clouds are socked-in tight. <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

adrenalynn · Dec 10, 2007

Not exactly a beacon of "pretty" - but hey - hand-guided 65" through a hole in the cloud-cover. ISO 1600. http://www.jlrdesigns.com/astrophotography/holmes-12-10.jpg At least I got it... I didn't even have the chance to set the scope up to track... <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

3488 · Dec 10, 2007

Well done & thank you Adrenalynn, Like that image a lot & have downloaded it. Your image still shows Holmes to be fairly circular, where as I saw it looking a little bit more oval. As iss immediately obvious with you photo, the contrast is becoming increasingly difficult. The ISO 1600 is a pretty fast setting, so that backs the contrast issue up. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

cnick · Dec 11, 2007

Comet Holmes has formed a very large (sort of) spherical shell (coma) of material around the size of the Sun. This coma is extremely tenuous, so much so that stars can be seen shining thru the center. This means the starlight is penetrating through 800,000 miles (more or less) worth of coma. Yet it was for a time easily visible to the naked eye. My question pertains to how we are seeing the comet, is it only by reflected sunlight? or is any of the light intrinsic to the comet? It seems to me that most of the sunlight must be passing through the comet and not being reflected back. Another question: Holmes resides entirely between the orbits of Mars and Jupiter and has since it's discovery in 189(2?) How could volatiles or ices sublimate at these distances? never mind cause the comet to explode. Is it not very cold out there? Would a dirty iceball or icy dirt ball be anything but frozen solid in the cold realm of Mars/Jupiter type distances?

MeteorWayne · Dec 12, 2007

First, the coma is lit by reflected sunlight. Second, it's warm enough for ices to sublimate at that distance. When it is closes to the sun (~ 2AU) is typically when comets start to become visible. Now the comet did not explode, although clearly something very big did happen. The current thoughts are that possibly a layer of material on the surface from the discovery event (a similar large outburst) may have been separated from the surface. As to why it happns 5 months after closest approach to the sun, as I suggested very early on, current theories suspect it takes that long for the warmth to soak in to the ice layer. The surface material acts like an insulator, but stores the heat, and a few months later the heat works it's way into the interior. However, it's all rather theoretical at this point; hopefully after observations have been analyzed, we will understand more. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

cnick · Dec 13, 2007

MeteorWayne: Thanks for clarifying that. Very interesting! Comets are fascinating, my interest has been stimulated from observing Holmes, though now it is becoming quite faint and I expect will fade out of view in the next few weeks. Has ice ever been observed on a comet? or detected by any space probes? It seems to me that it would be difficult to directly detect if it is beneath the surface, or is the presence of ice there an assumption?

adrenalynn · Dec 13, 2007

Have a look at NASA's "stardust program". <div class="Discussion_UserSignature"> .bipartisan (bī-pär'tĭ-zən, -sən) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.IMPEACH OBAMA! </div>

MeteorWayne · Dec 13, 2007

BTW, finally I had a chance to see Comet Holmes again. It's been a few weeks, so I was pleasantly surprised to see it was still easy to spot with the naked eye during my short meteor session. It's faint and large!! <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

cnick · Dec 13, 2007

Adrenalynn: Thanks for the nasa stardust link. Scientists will be analyzing this data for years to come. Comets are intriguing and mysterious objects. They are seemingly small and insignificant, yet are capable of putting on such a spectacular show! While the articles answered my questions somewhat, however... alas! I have even more questions. It seems to me that the "dirty snowball theory" is inadequate in light of information received from stardust and deep impact. Nasa scientists are evidently realizing this, as the articles are peppered with phrases like "totally unexpected," "surprising results," "more complex than we thought," etc etc. The close up pictures of comets (Wild2, Tempel1) from Nasa, look to me to be solid and asteroid like, as opposed to the loose conglomeration of ice and dust that was initially predicted by the "dirty snowball theory." Wild 2's surface was covered with "spires, pits, and craters." The Stardust mission's analysis of particles was surprising in that it revealed that they were formed at very high temperatures. That was totally unexpected. I guess that there is much more to be learned from the study of comets! I would expect that the scientific process of judging a theory must include it's ability to predict. "Surprising results" and "totally unexpected" are not exactly phrases that show confidence in a theory. Are there any alternative (to the "dirty snowball") theories being put forth? or can we make adjustments to accomodate the new information?

MeteorWayne · Dec 13, 2007

Actually, the data is consistent with a dirty snowball, or an icy dirtball. What was surprising was that the "dust or dirt" showed signs of being heated far above the temperatures expected out in the repositories where comets are thought to have formed. So the unexpected and surprising part has more to do with the early development of the solar system than the comets themselves. The images of comet nuclei are pretty consistent with what we expected, especially after our first close up of Halley's comet. The ice/dust/dirt micture is covered by a cohesive surface of material that has been modified by it's long time on the surface interacting with the solar wind, UV radiation, meteoroid impacts, and cosmic rays. Through that surface, jets eject material, as the ices beneath reach a temperature where they sublimate (turn from solid to gas) and pass through a crack, or hole melted through the surface. One other thing to remember is that we have learned over the last few decades is that there is a huge variety of small solar system objects, from solid iron, to solid rock, to porous rubble piles, and widely varying percentages of various ices. It's a continuum. There are not just asteroids and comets; there is no sharp dividing line between them. An object might appear like an asteroid far from the sun, but get it close enough to warm, and voila, it's a comet. There are a few known comets that reside totally within the asteroid belt; comet Holmes is but one example. It's all a part of learning about our solar system, which is why Dawn, New Horizons (it's been said Pluto would just be a really big comet if it was closer to the sun), Rosetta, and many other missions will continue our educational process. Now that's SCIENCE <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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