Ison Comet will be brighter than the moon

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Discussion Overview

The discussion revolves around the visibility and potential brightness of Comet ISON in November 2013, with participants speculating on its appearance compared to the moon, its physical characteristics, and possible interactions with Mars and Earth. The conversation includes theoretical considerations, observational predictions, and historical comparisons to past comets.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants express excitement about Comet ISON being potentially brighter than the moon, with one noting it might be visible during the day near the sun.
  • Others express skepticism about the brightness claim, questioning the comet's albedo, size, and closest approach to Earth.
  • There are discussions about the comet's tail and its visibility, with some suggesting it may be exaggerated while others argue it could be underplayed.
  • One participant mentions the possibility of ISON colliding with Mars, speculating on the consequences of such an event, while another corrects this by referring to a different comet (C/2013 A1 Siding Spring) that is also a potential Mars contender.
  • Concerns are raised about the impact of ISON on Mars' satellites and rovers, with speculation on the potential destruction of communication links.
  • Participants share personal anecdotes and historical references to past comet observations, such as Shoemaker-Levy 9's impacts on Jupiter.
  • There are requests for simulations regarding the potential for fragments from ISON to impact Earth, highlighting the uncertainties in predicting comet behavior.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the brightness of Comet ISON compared to the moon, with multiple competing views and ongoing skepticism about its predicted visibility and impact potential.

Contextual Notes

Participants acknowledge that predictions about comet brightness and behavior are speculative and depend on various factors, including the comet's interaction with the sun and its physical characteristics, which are not fully known at this time.

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could be fun :)

you should have posted this in the astro events section

maybe one of the mods would like to move it to there :)

Dave
 
I sincerely doubt it will be brighter than the moon. What is it's albedo, size, and closest approach to the Earth?
 
During the final stage near the sun the Ison comet will be visible during the day and brighter than the moon.
 
gendou2 said:
I sincerely doubt it will be brighter than the moon. What is it's albedo, size, and closest approach to the Earth?
A comet's brightness doesn't have much to do with albedo and size prior to entering the inner solar system. It's a comet -- what we see is mostly gas and dust, ejected when it nears the sun.

But:
Philosophiae said:
During the final stage near the sun the Ison comet will be visible during the day and brighter than the moon.
May. It may be brighter than the moon. It is still very iffy at this point. We won't even know if it will survive its brush with the sun until it happens and it will change very rapidly. So every day will be like opening a Christmas present for astronomers. I just hope it isn't socks.
 
Can't wait, if it's as good as Hale-Bopp was, I'd be very happy.
 
russ_watters said:
A comet's brightness doesn't have much to do with albedo and size prior to entering the inner solar system. It's a comet -- what we see is mostly gas and dust, ejected when it nears the sun.

But:
May. It may be brighter than the moon. It is still very iffy at this point. We won't even know if it will survive its brush with the sun until it happens and it will change very rapidly. So every day will be like opening a Christmas present for astronomers. I just hope it isn't socks.
I tend to agree with your slight scepticism. Predicting appearance even with good data is nothing but speculation. I remember all the hullabaloo about the return of Halley’s. What a let down!
 
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So I checked it out and found it on Starry Night. Although next to the sun, this is the brightest at an impressive -8.23 magnitude!

ISON_zps4c384dfa.png


This is how close it will be to eclipsing the sun! That would have been incredible, but if its accurate, I bet you could still see it clearly behind a solar filter.

ISON2_zps840d876d.png


And brightest after sunset

ISON3_zps7c709707.png
But, let me just mind you that the tail is exaggerated... a lot... but still worth gazing atevery second.
 
Franco Malgari said:
In November 2013 the comet Ison will be visible , spectacular, brighter than the moon:
Something like 30-60km across. Apparently there is an even chance it will collide with Mars. If so, at 60km/sec it should leave a crater around 300km across. The fireworks will be visible to the naked eye from Earth, for those favourably positioned. Were it to collide with Earth, the result would be similar to the event that wiped out the dinosaurs.

That's a few details I remember from a recent astronomy broadcast.
 
  • #10
NascentOxygen said:
Something like 30-60km across. Apparently there is an even chance it will collide with Mars. If so, at 60km/sec it should leave a crater around 300km across. The fireworks will be visible to the naked eye from Earth, for those favourably positioned. Were it to collide with Earth, the result would be similar to the event that wiped out the dinosaurs.

That's a few details I remember from a recent astronomy broadcast.

no ... wrong comet
This one is the possible Mars contender ...
C/2013 A1 (Siding Spring) is a new discovery by Robert McNaught on January 3. This comet will pass very close to Mars on the 19th of October 2014. There is a small possibility that it may impact the planet! It is not currently observable visually

Dave
 
  • #11
davenn said:
no ... wrong comet
This one is the possible Mars contender ...
C/2013 A1 (Siding Spring) is a new discovery by Robert McNaught on January 3. This comet will pass very close to Mars on the 19th of October 2014. There is a small possibility that it may impact the planet! It is not currently observable visually

Dave
If it did hit, can you imagine the pictures that some of the rovers might get right before they're vaporized?
 
  • #12
CosmicEye said:
But, let me just mind you that the tail is exaggerated... a lot... but still worth gazing atevery second.
It isn't necessarily exaggerated. In fact, it may be under-playing it. The tail could be long enough to stretch nearly from horizon to zenith, but what Starry Night doesn't pick up is that the comet is moving so fast that the tail drags across the sky like a fan. See The Great Comet of 2007:

cometmcnaught.jpg
 
  • #13
Borg said:
If it did hit, can you imagine the pictures that some of the rovers might get right before they're vaporized?

ahhhh indeed :)


D
 
  • #14
I well remember the impact marks on Jupiter of Shoemaker-Levy9 in 1994
WHAT an amazing birthday pressie!

These fragments collided with Jupiter's southern hemisphere between July 16 and July 22, 1994, at a speed of approximately 60 km/s (37 mi/s) or 216,000 km/h (134,000 mph). The prominent scars from the impacts were more easily visible than the Great Red Spot and persisted for many months.

I didnt have the ability to photo the impact sites back then, but seeing those black marks on Jupiter through my own scope was awesome

Dave
 
  • #15
davenn said:
I didnt have the ability to photo the impact sites back then, but seeing those black marks on Jupiter through my own scope was awesome

Dave
I'm buying a new camera for Ison. I would have for SL-9 too, had I not still been in high school and amateur webcam/ccd astrophotography not been invented yet...
 
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  • #16
Borg said:
If it did hit, can you imagine the pictures that some of the rovers might get right before they're vaporized?
Even if there isn't a direct hit, the astronomer said that it could well spell the end of our spotlight on Mars. Our Mars satellite/s that relay data from the Rovers will not fare well. The comet by the time it passes Mars is likely to have broken up into something akin to an expanding swarm of rocks, gravel and smaller particles, and some are sure to head towards Mars. The particles and the cloud they kick up may destroy the satellites, and with that our vital link to the Rovers.
 
  • #17
davenn said:
no ... wrong comet
This one is the possible Mars contender ...
C/2013 A1 (Siding Spring) is a new discovery by Robert McNaught on January 3. This comet will pass very close to Mars on the 19th of October 2014. There is a small possibility that it may impact the planet! It is not currently observable visually

Dave
Oh, I stand corrected. Two big comets in short time.
 
  • #18
It looks unlikely that C/2013 A1 (Siding Spring) is an issue for the rovers and satellites at mars, unless it comes extremely close or hits Mars. See this article for details.

ISON will come close to Mars (0.07 AU) as well, but without a reasonable impact probability.
 
  • #19
How often have we found "dynamically new comets" before this?
 
  • #20
I hope they're wrong. :frown:

http://www.reuters.com/article/2013/07/30/us-space-comet-idUSBRE96S16U20130730
 
  • #21
Exploding fragments from ISON could hit Earth

Can someone show the results of a simulation that has a chunk exploding off of ISON such that it will encounter the sun around twenty degrees offset (counterclockwise) from the original path? This will direct the chunk into the plane of the ecliptic towards a rendezvous with Earth. The chunk could hit Earth if the velocity imparted to it would be around 1000 km/hr- provided the sun does not disintegrate it during perihelion. Your assignment- should you choose to accept it- would be to determine the velocities imparted to such a chunk at different times during its approach to the sun over the next two months or so. You can pick a single time in perhaps a month when solar radiation might be reasonably expected to heat the comet's internal water to create the pressure that might result in an explosion. The velocity would be at right angles to the path and heading north. Note that such a chunk will not be large enough to endanger a certain, extraordinarily destructive species living on the planet, but may give them pause to consider morphing from an infestation to a nurturing habitation. The odds are highly unlikely that anything will happen. But then again, the odds of 60-meter diameter asteroid accompanying 2012 DA14 was on the order of one out of a billion. Enjoy!
 
  • #22
Answer: Turns out that the explosive force needed on the surface of ISON to send a chunk towards Earth is far beyond reasonable limits. At 1000km/hr, The chunk might achieve a separation of a million miles or more around Mercury's orbit, but at perigee when the comet is 30X closer to the sun, the separation distance will likewise be reduced by 30X. This will add less than a degree to the entrance path to perihelion for the chunk- not enough for the sun to whip the chunk down into the ecliptic towards Earth. Dang- another doomsday scenario discredited!
 
  • #23
Time for the ISON,I'll check it tonight,to see if it's visible to the Naked Eye.
Nov 22nd.
 
  • #24
Getting closer. From today's APOD

encke_ison_crop_srem_lr.gif
 
  • #25
Borg said:
Getting closer. From today's APOD

Those are some pretty nifty wiggles in the tail of Comet Encke. Is it to be supposed that the current solar magnetic field reversal will accentuate the motions of the solar wind, and hence the motions of the comet tails?
 
  • #26
The motions in the comets tail are primarily caused by fluctuations in the solar wind and by coronal mass ejections (which is what you are seeing in the above video clip - a CME)
 
  • #27
davenn said:
The motions in the comets tail are primarily caused by fluctuations in the solar wind and by coronal mass ejections (which is what you are seeing in the above video clip - a CME)

Ah ha, a CME! This blog of Karl Battams has a 2007 video of 2P/Encke's tail being completely ripped off by a CME. http://www.isoncampaign.org/karl/comets-in-solar-wind

His colleagues say the stronger magnetic field of the CME caused the tail to reconnect from the IMF.
 
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  • #28
mfb said:
It looks unlikely that C/2013 A1 (Siding Spring) is an issue for the rovers and satellites at mars, unless it comes extremely close or hits Mars. See this article for details.

ISON will come close to Mars (0.07 AU) as well, but without a reasonable impact probability.

The fly-by of Siding Spring to Mars has now come and gone. According to early findings, the rover and satellite operators were very glad they placed their vehicles on the side of the planet facing away from the comet.
http://www.nasa.gov/press/2014/nove...al-comet-flyby-effects-on-martian-atmosphere/
 

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