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0
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1answer
42 views

Calculate the speed of Halley's comet at his perihelion [on hold]

Knowing that Halley's comet orbita the sun every 75,3 years, that the semi-major axes is 17.83 AU, the semi-major axes is 4.53 AU and at his perihelion he is 0.586 AU away from the sun. With these ...
-2
votes
1answer
63 views

What powers a comet? [closed]

I know that a comet is a ball of ice, and I have tried the NASA page. http://spaceplace.nasa.gov/dr-marc-solar-system/en/#/review/dr-marc-solar-system/comet-power.html but they swerve around the ...
2
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0answers
40 views

SOHO solar observatory, comet numbers and composition

SOHO discovered its 3,000th comet, cementing its standing as the greatest comet finder of all time. Prior to the 1995 launch of the observatory, commonly known as SOHO, only a dozen or so comets ...
3
votes
1answer
71 views

How come the Tunguska fireball reached the ground before the shockwave?

In this post on his Bad Astronomy blog, Phil Plait describes the Tunguska event as having had a fireball which was followed by a shock wave: A chunk of rock (or possibly ice) about 30 meters ...
18
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6answers
5k views

Halley's Comet as a “Free Taxi”

Now that the ESA has landed a probe on a comet, namely Rosetta's Philae Probe, could we possibly land a probe on Halley's comet? Fuel seems to be a limiting factor for interstellar expeditions - could ...
4
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1answer
81 views

Shoemaker-Levy 9 impact on Jupiter

When the comet Shoemaker-Levy 9 impacted with Jupiter it created a ball of fire 3000 Km high and it left a mark on the surface of the planet that was visible for weeks (source: Wikipedia). How was the ...
2
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0answers
23 views

How can comets have sand dunes without atmospheric erosion? [duplicate]

This article here talks about dunes visible on comet 67P: In August, the European Space Agency (ESA) achieved a major success when its Rosetta probe rendezvoused with comet 67P. The spacecraft ...
2
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2answers
1k views

What is the weight of the Philae lander on the Churyumov–Gerasimenko comet compared to earth?

We know the payload mass of the Philae lander was 21kg. We know the mass of the Churyumov–Gerasimenko comet is roughly 1 x 10^13kg. We know the mass of Earth is roughly 5.9x10^24kg. I've heard ...
30
votes
9answers
7k views

What is the speed of the fastest moving body in our solar system?

On Wikipedia I saw that the average orbital speed of planet Earth around the Sun is a whopping $29 783\text{ m/s}$, and it made me wonder are there bodies (planets, meteorites, asteroids) that move ...
15
votes
4answers
564 views

What mechanism is responsible for the creation of these dunes on Comet 67P/Churyumov-Gerasimenko?

What mechanism is responsible for the creation of these dunes on Comet 67P/Churyumov-Gerasimenko? The following high resolution picture from ESA's Rosetta mission shows the dunes: At a distance ...
0
votes
1answer
58 views

Regarding the theory of the origin of water on earth through meteorites, why wouldn't the water evaporate on impact?

Water on earth has been theorized to have come through comets trapped inside crystals. But why wouldn't that water evaporate on impact, and wouldn't the atmosphere at that time allow the vapours to ...
1
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0answers
72 views

How do you calculate the radiant for Kreutz Sungrazer comets? where in the sky do I look?

According to wikipedia: All known members of the [Kreutz Sungrazer] group up until 1965 had almost identical orbital inclinations at about 144°, as well as very similar values for the ...
6
votes
1answer
256 views

Why do comets have tails?

There is no atmosphere for comets to get hot and burn and show tails but they still have tails. Why do they? Edit: Isn't the answer "acceleration"?
0
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2answers
51 views

Ways to spot a comet or asteroid?

How do we spot a comet or asteroid if it does not emit light or pass infront of an object which emits light? And if such an object would be on a crash course with our planet how early would we be ...
0
votes
1answer
79 views

List of all past comet passes and area it was visible?

Is there a database/website which shows all comets which have passed Earth and have been viewed? Is there any country specific viewing database as well? I would like to do a search on the lines of : ...
5
votes
1answer
254 views

What is the likelihood of a long-period comet impact?

I always see lots of information about asteroid impacts, but very little is said about comet impacts. As I see, a long period comet impact is much more dangerous because a) we wouldn't have time to ...
6
votes
2answers
182 views

Are comets known to exist in other star systems?

Are comets a feature unique to our Solar System? Or, are comets/cometary clouds detected around discovered/observed extra-solar systems too? If they were detected elsewhere, how do such cometary ...
5
votes
1answer
147 views

How close does a meteorite have to be in order to be heard by the human ear?

...speaking of Perseid meteor showers...How close would a Perseid meteorite have to be in order to be heard by the human ear? Is it even possible to hear a Perseid meteorite? If they come close ...
8
votes
1answer
93 views

Why does the debris from comets and former comets hang around so long?

So tonight's Quatrantids shower got me thinking. Why does the debris from comets and former comets hang around so long? Each year the earth sweeps through the region of space that the comet went ...
1
vote
2answers
93 views

Which direction before dawn to look for Comet Lovejoy (C/2011 W3)? [closed]

Various websites today are reporting with photos and videos of Comet Lovejoy. However, I can't seem to find a definition of which direction to look for it tomorrow morning. I'm in Christchurch, New ...
11
votes
3answers
8k views

What are the facts that allow accepting the Oort cloud theory?

I admit without any fact that the Oort cloud (comet reservoir) should exist, and it seems to be accepted by far by the large majority of astronomers. But it is still a theory without any direct ...
6
votes
2answers
127 views

Why doesn't a close comet like Elenin look like other, famous comets (Hale Bopp, Halley…), which have nice, long trails?

Elenin is a comet that runs very close to the Earth (0.8 times the Earth-Moon separation at its closest point). By naked-eye observation, it doesn't look like the other famous comets (Hale Bopp, ...
6
votes
1answer
133 views

What conditions should an asteroid or comet impact need to meet in order to start an impact winter?

Is there a way to calculate if an impact from a given asteroid (say 5 miles in diameter, solid rock to which we know the mass) would start an impact winter? If yes, I would like to see a real example ...
7
votes
1answer
267 views

Could two colliding comets near Earth cause devastation?

Let's say two comets crashed into each other. If it was 0.1 AU away from the Earth, would the collision cause mass destruction here, or not affect us at all?
2
votes
2answers
403 views

Why can't you see meteors, but you can see comets from the moon?

Why can't you see meteors from the moon and why can you see comets?
12
votes
1answer
9k views

How does a comet form?

As the title explains, How does a comet form? What are the elements, what is a comet composed of? Why didn't they become part of planets, moons or asteroids?