Comet ISON shaping up to be a spectacular display

Jan 15, 2013 by Bob Yirka report
Image of comet ISON as seen on 22 September 2012 through a 0.25-m reflector by the Team of observers of Remanzacco Observatory. Credit: Remanzacco Observatory

(Phys.org)—Excitement is mounting for astronomers and star gazers the world over as word spreads that Comet ISON may go down in the history books as one of the flashiest ever. First discovered in September of last year by Russian astronomers, Vitali Nevski and Artyom Novichonok, Comet ISON (C/2012 S1) has been drawing attention ever since.

Comets, as most are well aware, are balls of ice and rock that move though space – when they get close enough to the sun, they sprout tails giving rise to poetic descriptions of beauty by some and claims of mystical phenomenon by others. ISON is expected to be at its brightest in late November of this year, leading some to link it with the Star of Bethlehem which the Bible says led the three wise men to the newborn baby Jesus. Its perihelion – closest approach to the sun – is expected to occur on November 28 and the comet will likely be best viewed in the .

Of course, projecting the brilliance of a comet or its tail length is an iffy proposition to be sure. It could just break apart when it nears the sun (it's expected to come as close as 32,000 miles), leaving us here on Earth less than impressed with the results, (see Comet Kohoutek - 1973.) More optimistically, because of its size and orientation, it might just present us with the brightest comet show ever seen.

Right now Comet ISON is in Jupiter's orbit, hurtling towards a rendezvous with the sun. As it approaches, bits of it will be vaporized, leading to the creation of a tail. Once it arrives, it will whip around the sun at approximately 425,000 mph and then head back into space passing our planet on its way, allowing us to see it in all its finery.

The best viewing time for the comet is expected to be early in the morning before the sun comes up, as it approaches, and then at both pre-dawn and just after the sets as the comet is leaving. When it's approaching, its tail will follow behind it, but as it's leaving, due to , it will be following its own tail. Estimates on Comet ISON's brightness vary – some suggest it might be equal in luminescence to the planet Mars, while others hint that it might be as bright as the moon, which means it would be visible even during daylight hours.

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antialias_physorg
3.7 / 5 (3) Jan 15, 2013
Anyone have a number for the comet's diameter? I've been hunting around but couldnt find any obvious answers.

On another note I wonder when the first doomsday (or resurrection of christ) prophecies about the comet will start to surface.
lowerarchy
4.8 / 5 (4) Jan 15, 2013
On another note I wonder when the first doomsday (or resurrection of christ) prophecies about the comet will start to surface.

"leading some to link it with the Star of Bethlehem"
Looks like it's already happened...
cantdrive85
1 / 5 (14) Jan 15, 2013
"Comets, as most are well aware, are balls of ice and rock that move though space"

Right.....as few are aware, this is a true statement only if you ignore visual evidence, Stardust, and Deep Impact.
Jeddy_Mctedder
1 / 5 (4) Jan 15, 2013
Weve discovered a comet that in september was beyond jupiter.
Over the last ten years astronomy has made a quantum leap in its vission. We were once blind seeing only with our eyes and relatively simple optical system and now with digitalization of optics and we are beginning to truly see the cosmos.

This comet will define a new era for science.......the masses will see it and they will understand our sciences are bring us a new level of insight to the cosmos, to seeing the great beyond.
GSwift7
1 / 5 (1) Jan 15, 2013
Anyone have a number for the comet's diameter? I've been hunting around but couldnt find any obvious answers


No way to know that yet. Gotta wait till it gets in closer.

Wheeww! Nearly half a million miles/hour. Earth's circumference is apx 24,000 miles. At 425,000 miles per hour that takes you around the Earth almost 18 times per hour. Or, that takes you around the Earth once in less than 3.5 minutes. Or, about 118 miles in one second.

Humans don't have the technology to get a spacecraft going that fast. Well, maybe if you flew out to Pluto, refueled, then headed back and used every trick in the book to speed up. It would take decades to do it, if it's possible at all.
LariAnn
3.7 / 5 (3) Jan 15, 2013
Here's a truly fanciful idea - launch a probe to rendezvous with the comet as it is leaving, and have the probe land on it and hitch a ride. If successful, we could get data on the entire orbit of the comet (assuming the probe is as hardy and long-lasting as the Voyagers). We might not have enough time to figure out how to get the probe up to speed for the rendezvous before it becomes possible - hence the fanciful quality of the idea. Then again, we'd only need enough fuel for that because the rest of the trip would be "funded" by the comet itself. It is fascinating to imagine the possibility of such a mission.

As long as I'm being fanciful, the probe could be designed so that on the next time passing by here, it would lift off and return to Earth with samples!
VendicarD
3 / 5 (8) Jan 15, 2013
Faux news is reporting...

Inside this comet is an army of space vampires returning from their 100,000 year slumber to once again feed on the blood of mankind - especially nakkie white women.

The only thing that will save mankind from the scourge of vampire tyranny are more tax cuts for the wealthy and an increase in Right-shoring of American jobs to third world labor camps.
antialias_physorg
3.5 / 5 (4) Jan 15, 2013
Here's a truly fanciful idea - launch a probe to rendezvous with the comet as it is leaving, and have the probe land on it and hitch a ride.

Not gonna happen. The fastest probes we have ever launched have less than 10% of the speed of this comet.
philw1776
4 / 5 (4) Jan 15, 2013
LariAnn, first the comet's relative velocity is too high for us to reach it as you correctly surmised. Secondly, the rest of the trip is not funded by the comet. Once you reach it you've done the funding by matching its orbit. Thirdly, the comet's orbit is so near hyperbolic that it may never return or will return in hundreds of thousands or millions of years. Exact orbit parameters are yet unknown.
LariAnn
5 / 5 (4) Jan 15, 2013
LariAnn, first the comet's relative velocity is too high for us to reach it as you correctly surmised. Secondly, the rest of the trip is not funded by the comet. Once you reach it you've done the funding by matching its orbit. Thirdly, the comet's orbit is so near hyperbolic that it may never return or will return in hundreds of thousands or millions of years. Exact orbit parameters are yet unknown.


Hence, my description of the idea as "fanciful". However, by "funding" I meant that the probe would not need any more propellant once it had made a landing on the comet because the comet's motion alone would carry the probe for the rest of the trip. Contrast this with a probe making such a journey out of and into the Solar System using only propellant it could carry, plus slingshot assists.

Finally, even if the comet never returned, the probe would be taken out much farther and much faster than anything that could be designed to do so without the comet's help.
LariAnn
not rated yet Jan 15, 2013
My fanciful idea may be workable if applied to a body moving much slower than this comet, though. A comet or asteroid moving near to or under the speed that is achievable with current technology could enable the acquisition of science data from such bodies without going out very far to find them. For example, recent asteroid flybys have included a few candidates that passed by closer than the distance from Earth to the Moon.
dschlink
not rated yet Jan 15, 2013
The Japanese Hayabusa spacecraft returned with samples in 2010. They have a second mission planned for a 2014 launch. We (USA) have a very preliminary mission planned. I have no great hopes for it to ever be funded.
philw1776
5 / 5 (1) Jan 15, 2013
However, by "funding" I meant that the probe would not need any more propellant once it had made a landing on the comet because the comet's motion alone would carry the probe for the rest of the trip. Contrast this with a probe making such a journey out of and into the Solar System using only propellant it could carry, plus slingshot assists.


What I am trying to tell you is that the probe does NOT get a free ride from the comet nor does it need to.
Simply by matching the comet's orbit no need to land the probe continues on with the comet. It needed all that propellant just to get there.
Skepticus
2.3 / 5 (3) Jan 15, 2013
I wonder if a probe can be fast enough to catch up with the comet, if we launch it to sling shot very close to the Sun? With an ablative heat shield (adequate mass for surviving the close sling shot) that boils away and the gas channeled somehow to give added thrust in the manner of rocket exhaust? When the heat shield job is done, then it is jettisoned and further steering would be done by on board motors. If the probe can not get fast enough, may be we can send it on an impact trajectory. We build it to (mostly) withstand an impact, with a chunk of radioactive material that will act as a heat signature that can be tracked with infrared telescope. If the impact is near enough, a detailed spectral analysis of the makeup of the comet can be make from Earth, or Earth orbiting instruments. Just thinking.
rkolter
5 / 5 (1) Jan 15, 2013
Neat Comet. 118 miles per second when it hits the closest approach, which is only 32,000 miles from the surface of the sun? Sounds like someone's throwing snowballs at us. :)
philw1776
not rated yet Jan 15, 2013
Impacting anything at a rate of many tens of miles per second will leave only vapor. You would get an impact spectra but what would be different from the normal spectra as the comet is outgassing from the surface and internally anyway? This is one fast moving comet once it nears the inner solar system.
Maggnus
4 / 5 (4) Jan 15, 2013
@ Lariann - there is already a comet rendezvous mission headed by ESA called Rosetta. It's supposed to land on a comet(name escapes me) sometime in 2014. If you're interested, the details can be found on the ESA site
TheGhostofOtto1923
1 / 5 (6) Jan 15, 2013
On another note I wonder when the first doomsday (or resurrection of christ) prophecies about the comet will start to surface.
Its all so...prescient...

"Large sun-grazing comets could bring on the sort of global electronics meltdown usually associated with electromagnetic pulse weapons or a full-scale nuclear exchange.

Or so says David Eichler, lead author of a forthcoming Astrophysical Journal Letters paper positing that a sun-grazing comet roughly the size of Hale-Bopp (with a nucleus some 30 kms in diameter), could trigger cosmic ray-generating shockwaves large enough to initiate a global electromagnetic Armageddon."
I wonder if a probe can be fast enough to catch up with the comet
Why bother? Many easier to study objects out there.
RealScience
5 / 5 (4) Jan 15, 2013
@GSwift and AA - we can get something going almost that fast (424,000 mph) just by dropping it that near the sun.
Comet ISON is not going all that fast now. At Jupiter's orbit it will only be going ~√2 times as fast as Jupiter, or just under 20 km/s.
When it crosses earth's orbit it will be going a bit over 40 km/s.

The voyager craft are going faster than ISON did when it was out that far, so if we had put the same energy into grazing the sun at 50,000 km, the voyagers would have been going just slightly faster than ISON will.

The amazing thing about ISON is how close it is coming to the sun's surface without hitting it. 50,000 km is only 7% of the sun's radius, so this is a really close shave for a big comet to have, probably a once in a lifetime experience for us!

But I remember what a disappointment Kahoutek was, so I'm trying not to get too excited yet.
Jeddy_Mctedder
1 / 5 (4) Jan 15, 2013
Dont forget on feb 15in one month from now a 120 foot space rock is projected to fall/pass under our geosynchronous sattelites. At 20000 miles projection and a month away from us...i believe, without knowing astronomy, the margin of error is probably wide enough ( given variations in the solar wind, various yarkovski affects, and possible van allen belt anomalies, and tidal interactions, and all of the mild interaction with the asteroid---itself within the roche limit/hill sphere )these gravitational and energetic phenomena) ........i think there is reasonable doubt to believe this could hit earth. Call me nuts.
antialias_physorg
3.7 / 5 (3) Jan 15, 2013
@GSwift and AA - we can get something going almost that fast (424,000 mph) just by dropping it that near the sun.

Well, I dug around a bit more. We did have probes close to the sun that hold the speed record (the two Helios probes) - which did about 150000mph.

Still off by a factor of three.

And just like the comet: You can speed stuff up by going close to the sun. But once it heads back out it slows down again.
Rydog
1 / 5 (2) Jan 15, 2013
Anyone have a number for the comet's diameter? I've been hunting around but couldnt find any obvious answers.

On another note I wonder when the first doomsday (or resurrection of christ) prophecies about the comet will start to surface.


Perhaps you mean the second coming of Christ? Those making prophecies of Christ likely believe He is already risen.
that_guy
5 / 5 (1) Jan 15, 2013
@Anti-alias - Due to the distance and small size of the comet, our estimates will currently have huge margins of error, but I found these:

Current estimates have the diameter at 3-30 miles across.

http://astrobob.a...s1-ison/
http://remanzacco...son.html

@others - We could not directly design and launch a substantial or reliable mission to the comet on such short notice. However, Space craft in transit have been known to take unexpected visits of opportunity if an object of interest - like this one, crosses paths close enough.

I hope that the comet is fantastic - Lowell Observatory is Very welcoming to visitors, and only a day trip away from where I live (~3 hour drive away)
Anda
1.8 / 5 (5) Jan 15, 2013
a probe making such a journey out of and into the Solar System

So you think the comet goes out of the solar system? No comment
eachus
1 / 5 (1) Jan 16, 2013
Real Science said:
The amazing thing about ISON is how close it is coming to the sun's surface without hitting it. 50,000 km is only 7% of the sun's radius, so this is a really close shave for a big comet to have, probably a once in a lifetime experience for us!


Very possibly a once in a lifetime visit for the comet, at that perhelion distance. ;-)

On the other hand, I've been promised many once in a lifetime comet viewing experiences in my lifetime. Kohoutek and Hally's [in 1986] were definite flops, but some shows worth seeing as well. I guess the trick is to see what other backyard astronomers have to say.
marble89
5 / 5 (2) Jan 16, 2013
"Rendezvous with Rama" ???
antialias_physorg
1 / 5 (1) Jan 16, 2013
we can get something going almost that fast (424,000 mph) just by dropping it that near the sun.

Something has bothered me about that statement for a while - but I couldn't put my finger on it. But I think I figured it out:
Gravity assist maneuvers via planets (slingshots) only change the magnitude of the speed of the probe relative to the sun (it only changes the DIRECTION relative to the planet. But once the probe leaves the gravity field of the planet the magnitude of the speed vector relative to the planet is the same as before)

Ergo: You can't slingshot around the sun and thereby gain speed. (You can drop towards the sun to gain speed. But that speed is all lost once you get back out to the distance you started from)

On further consideration: That's a rather glaring science SNAFU in Star Trek IV.
TheGhostofOtto1923
2.3 / 5 (6) Jan 16, 2013
(it only changes the DIRECTION relative to the planet. But once the probe leaves the gravity field of the planet the magnitude of the speed vector relative to the planet is the same as before)
Are we sure about this? The probe gains momentum and the assisting object loses it by a proportional amount. The planet would slow a little and its orbit would degrade.

This would be more obvious if the object were a moon or comet. From wiki:

"A close terrestrial analogy is provided by a tennis ball bouncing off a moving train. In the cartoon at right, a boy throws a ball at 30 mph toward a train approaching at 50 mph."

-Except that the ball does affect the train but by only a negligible amount yes?

Interactions of this sort dislodge objects from the oort cloud and the asteroid belt all the time dont they?
RealScience
5 / 5 (1) Jan 16, 2013
Agreed on Halley's 1986 visit also being a big disappointment.
By far the best I ever saw was Ikeya Seki in 1965 - well worth the cold pre-dawn viewing conditions!

Agreed that this might be once-in a lifetime for the comet - it will pass much closer to the sun than Ikeya Seki did, or the Great Comet of 1680 did for that matter. But if it survives (even in multiple pieces), it could be glorious.
GSwift7
1 / 5 (1) Jan 16, 2013
The voyager craft are going faster than ISON did when it was out that far, so if we had put the same energy into grazing the sun at 50,000 km, the voyagers would have been going just slightly faster than ISON will


The only reason Voyager is moving so fast is thanks to multiple planetary assists. The timing was 'just right' for getting a boost from nearly all the outer planets, one after another. We couldn't do that right now because they aren't lined up right. When Ison gets back out to 1 AU, it will be moving much faster than the initial speed of either of the Voyager spacecraft.

Additionally, when you use planetary assist it deflects your trajectory in the direction of travel of the planet. The more assist you want, the more deflection you get. After several assists, you get a vector that is severely off axis from being directly radial from the sun. Ison's vector will be almost directly radial from the sun. We can't match that speed and direction at the same time.
RealScience
5 / 5 (1) Jan 16, 2013
Ergo: You can't slingshot around the sun and thereby gain speed. (You can drop towards the sun to gain speed. But that speed is all lost once you get back out to the distance you started from)


Exactly the point. That's what the comet is doing, too, only from way out instead of from earth's orbit. It is only temporarily gaining speed as it falls sunward, and will lose it again on its way out (if it survives).
Getting to the same perihelion distance from earth's orbit would reach 424,000 mph versus the 425,000 mph that the comet will reach from way out.

Since the voyager craft exceed the sun's escape velocity while the comet doesn't, if we had put the same energy into directing the Voyagers sunward to a perihelion that close, they would be going faster than comet ISON. If they survived, that is.

So we COULD (given years warning) get something to match ISON's orbit, even with Voyager-launch-era technology.
GSwift7
3.7 / 5 (3) Jan 16, 2013
I think the most interesting thing about this comet is that this may be the first time it has ever visited the inner solar system.

We'll see what happens, but I think it is safe to assume that a virgin comet should out-gas brilliantly on it's first trip in. It should be loaded with volatiles that are gonna start boiling off like crazy by the time it gets to 1 AU. It should be composed similar to the cosmic abundance.

Assuming that Ison is a virgin object, it would be the first virgin object we've been able to observe. We should be able to learn quite a bit by comparing it to what we know about short period comets, since those short period comets probably started out like this one.

Since it will pass through Earth's orbit, it should create the coolest meteor storm we've ever seen. If it does like I think it's gonna do and sprays a huge tail, we'll end up with all kinds of tiny bits in our path.
Skepticus
1 / 5 (2) Jan 17, 2013
@A.A
I wonder...if you are right, what is the purpose of the sling shot anyway? Just to change direction? True that the speed you gain dropping towards the Sun is offset by the drop off as you move away, but in the whole you gain speed getting out of the system by taking momentum out of it. Otherwise, no stars or planet would be ejected from systems as astronomy news have reported here and there? As for Star Trek IV, they also did use thrusters at perihelion to boost the speed even higher-and scifi wise- they enter "Warp" there so Newtonian nor Einsteinian uphill gravitational drag shouldn't be an issue. They effectively disappeared from normal space-time then and there?
antialias_physorg
1 / 5 (1) Jan 17, 2013
if you are right, what is the purpose of the sling shot anyway? Just to change direction?

The point of a slingshot around a PLANET is to change direction AND speed relative to the SUN.
This is done by adding (or subtracting) orbital velocity from the planet you're slingshotting (is that a word?) around.

But the sun isn't in orbit (around the sun). So there's nothing to get orbital velocity from by using a slingshot maneuver there.

Otherwise, no stars or planet would be ejected from systems as astronomy news have reported here and there?

Planets (and stars) get ejected by interactions with third bodies (e.g. other planets, passing stars, etc.). A planet that is in orbit around the sun cannot get ejected on its own.
To get ejected, additional momentum RELATIVE to the star has to be gathered from somewhere - and the star itself has no momentum relative to itself.
GSwift7
1 / 5 (1) Jan 17, 2013
But the sun isn't in orbit (around the sun). So there's nothing to get orbital velocity from by using a slingshot maneuver there


This is correct.

The whole Star Trek time warp thing is silly. Don't even try to rationalize it. You've gotta break a bunch of laws of physics to do what they do on that show. Just enjoy it as good fiction and call it a day.

The fastest launch speed we've ever done is with New Horizon, which launched with solar escape velocity without planetary assist. It used five external solid boosters, as well as an extra booster third stage. It was a prototype rocket configuration, never used before or since.

So I must correct myself. The launch configuration we used for New Horizon actually could catch Ison, barely.

BTW, New Horizon is supposed to try to visit a Kuiper belt object if it can find one after it passes Pluto. I wonder if there's a difference between Kuiper belt objects and Ort cloud objects, or if they are essentially the same?
Skepticus
2.6 / 5 (5) Jan 17, 2013
To get ejected, additional momentum RELATIVE to the star has to be gathered from somewhere - and the star itself has no momentum relative to itself.

you forget that the sun, central to the local system as it is, is orbiting the galaxy at considerable speed, not standing still. Therefore, i think the probe sling shot round a sun, or The Sun, still works by robbing it of the momentum it possesses orbiting the galaxy center.

Circulator38
not rated yet Jan 19, 2013
Comet C/2012 S1 ISON Facebook Page - http://facebook/C2012S1
antialias_physorg
3 / 5 (2) Jan 19, 2013
you forget that the sun, central to the local system as it is, is orbiting the galaxy at considerable speed, not standing still. Therefore, i think the probe sling shot round a sun, or The Sun, still works by robbing it of the momentum it possesses orbiting the galaxy center.

We're talking about getting some boost for going to other destinations within the solar system (all object ins the solar system are in the same orbit around galactic cebter). You can't get any boost for such a destination by slingshot around the sun.

Slingshot around the sun will only get you a boost for going anywhere else in the galaxy (extra solar). But for THAT kind of trips such a 'boost' is very insignificant.
GSwift7
not rated yet Jan 21, 2013
you forget that the sun, central to the local system as it is, is orbiting the galaxy at considerable speed, not standing still. Therefore, i think the probe sling shot round a sun, or The Sun, still works by robbing it of the momentum it possesses orbiting the galaxy center


Since the Earth is traveling with the Sun, there's nothing to gain from slingshotting around the sun, whether you are headed out of the solar system or not.

As for interstellar travel, any potential speed you might gain by using a gravity assist from another star in order to reach some other star would be inconsequential. The speed you need in order to reach any other star in a reasonable amount of time is so fast compared to the relative speed of nearby stars that you wouldn't even notice the gravity assist. It would be like using a turtle to speed up a bullet.