Question about Halley's Comet

I was womdering…

halleys comet orbits around our sun approximately once every 76 years. And each time it passes, immense amounts of dust, dirt, ice and whatever come off the comet in a large long tail. This happens each time it atoms our sun, correct? And the material is in no way replenished in its elongated orbit, so it is getting smaller each time it passes by. So, how many passes does it have left before it is no longer viable? Has there been any estimation as to how large Halleys comet was long ago, and when the thing will have no more ice left to melt and blast off? How big will the chunk of rock be left, or will there be anything of significance left at all? Eventually this has to take place right? Halleys comet will one day die out?

Also, is halleys comet contained within our stars ort cloud, or is it coming from outside the cloud, or from inside the cloud?

Finally, a gravity related question. Is there a limit to the number of things an object can attract with its gravity? For example the sun has the 8 planets, all the moons, the asteroid belt, the ort cloud, an various other things caught within its gravitational pull. Would there be a limit to the amount of objects an object like the sun can hold into orbit, PR is it only limited by the space within the gravitational “viable” if you will, that surrounds the sun?

From Kepler’s Third Law, if the period is 76 years, the semi-major axis is about 18 AUs, which would keep it within the orbit of Uranus, and thus never really out in the Oort Cloud.

(Rather than make the obvious joke, I’ll make the joke about a super-villain who had an Oort Gun. It didn’t do any damage, just inertialess knock-back. One hit…and you’re in the Oort Cloud.)

Gravitational force exists between everything and everything else

Well, in theory, anyway - if gravity propagates at the speed of light, there may be objects in the universe that are forever beyond the gravitational reach of each other, if they are expanding away from each other too fast.

ETA: There’s a practical limit to the number of objects that can orbit a body before they start smacking into, or perturbing each other.


Thanks for that info si.

I’ve been waiting for someone to give me the standard:

"I’ve never made it without biting. Ask Mr. Owl, who says "let’s find out. Ah one, ah t-t-two, ah three. <CRUNCH>. Three.

Yeah, I know it doesn’t make sense. And it’s not funny. But it’s a good piece of counting matierlal.

Nitpick: Halley’s semi-major axis is about 18 AU, but the aphelion is about 35 AU because its orbit is so eccentric. So its orbit takes it beyond Neptune, into the region of the Kuiper Belt, but not into the Oort Cloud.

I was at junior school last time Halley’s comet came round, and remember it being very anticlimactic. Wikipedia says it gave “the worst viewing circumstances for Earth observers for the last 2,000 years”, because it was on the opposite side of the sun from the Earth, but presumably this was known ahead of time. Even so, wasn’t it still a lot less bright than had been expected, even given the unfavourable positioning? If so, what caused that?

Nitpick 2: It’s proper name is “Comet Halley”, not Halley’s comet.

Eventually, comets do break down. A children’s book once related a periodic comet, that eventually broke into twin comets, after a few more passes, one of the twins seemed dimmer, the next pass, the comet was replaced by a meteor shower. I don’t know the name of the comet, that became a twin, that became a meteor shower, however.

Is that a modern convention? People certainly used to call it ‘Halley’s Comet’, all the way back to the time when Halley was still alive.

ETA: (Cite)

Tell me about it. I bought myself a 4" refractor telescope so I could see it “up close!” I didn’t see it at all from my latitude. I did learn what type of telescope not to buy though.

Looks like it. Looks like the 1980s. I couldn’t find any obvious references to “Comet Halley” before 1980 in Google News Archives, compared to “Halley’s Comet.” Doesn’t mean they weren’t there, but they were surely outnumbered.

Biela’s Comet

This. What a disappointment. Although, on the bright side (no pun intended): it’s good motivation to try my best to stick around to see the NEXT visit.

That said, Hale-Bopp sure was a pleasant view. Well, at least until the “culty suicides” put such a damper on the festivities.

This is what happens when you cut money out of the military and put it into health care.

Slight hijack, but for you people disappointed by Halley’s comet, keep your fingers crossed for Comet ISON, discovered a couple weeks ago and scheduled to pass by late next year. Some optimists are estimating it will be brighter than the moon and visible during the day.

That’s exciting I hope it is a good show. I remember the disappointment with Halley; I cant even remember seeing it now.

The one that really floored me was Hyatake the year before Hale-Bopp. Not as bright as Hale-Bopp, but I remember seeing it from dark areas of town. We went out one night for a little hike in the country to see it and I was amazed. It was HUGE. What I had seen before was just the bright center but the tail stretched across the sky (35 degrees according to the Wiki). It passed within 0.1 Au. The sense of scale was incredible.

Nitpick 3: “Its”

To address the OP: I once heard that a comet gets about 100 passes thru the inner solar system. So, after whatever time Halley’s Comet got gravitationally knocked into its current orbit, it’ll have its last pass thru about 7,600 years after that.

Of course, that was 40 years ago I read that. Cometary science may have a different theory now.

The OP didn’t quite ask this, but it’s kind of implied in some of his questions.

Comet Halley, like all short period comets, probably originated in what’s called the Scattered Disk., a subsection of the Kuiper Belt. The Scattered Disk is made up of those KBOs that are not in neat circular orbits or in resonance with Neptune. Their orbits cross those of one or more of the gas giants (usually just Neptune’s). Also included in the Scattered Disk is a subgroup called Centaurs, which orbit completely within the outer Solar System, that is, between the orbits of Jupiter and Neptune.

Since Scattered Disk Objects cross a large planet’s orbit, a close approach could change (perturb) their orbit so that they go inward to pass near the next planet inward’s orbit. Further perturbations may cause them to orbit further inward. The last perturbation they get is from Jupiter, which will do one of three things: 1) eject them from the Solar System, 2) cause them to collide with Jupiter (see Shoemaker-Levy 9) or 3) go into the inner system and become a comet.