Questions tagged [comets]
41 questions
29
votes
9 answers
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 faster?
My question is not about small photons or…
Willemien
- 381
22
votes
2 answers
Why do the Perseids only happen once per year, not twice or four times?
The Perseid meteor shower is caused by debris left behind Comet Swift-Tutte. My understanding is that the meteor shower occurs once per year because that's when the Earth passes near the orbital path of the comet.
My question is why this shower only…
templatetypedef
- 663
19
votes
6 answers
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 using Halley's comet as a free taxi, shutting…
GoodChessPlayer
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17
votes
4 answers
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 of 7.8 km from the surface, the image scale is about
…
16
votes
2 answers
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 observation. Except the fact that we guess that comets…
Emmanuel Devaux
12
votes
1 answer
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?
user
- 657
8
votes
1 answer
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 through. However, the comet doesn't come by each…
Larian LeQuella
- 7,792
8
votes
1 answer
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?
grassman
8
votes
2 answers
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, Halley, etc.)- its trail is quite invisible.
Why ? Is…
Emmanuel Devaux
7
votes
3 answers
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"?
richard
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7
votes
2 answers
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 clouds affect discovery by perturbation of planets in…
Everyone
- 4,741
7
votes
2 answers
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 of an existing asteroid, if possible some…
Ioan Paul Pirau
6
votes
3 answers
What is the scientific basis for comets vs. main-belt comets being composed of different materials?
Do we observe different events or activities on main-belt comets, or do they behave exactly the same as regular comets?
(Apart from the obvious difference in orbit size/shape.)
The Wikipedia article for main-belt comets currently states the…
Giffyguy
- 458
6
votes
2 answers
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 across—the size of a house—barreled in at a speed…
Emilio Pisanty
- 137,480
6
votes
1 answer
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 ball of fire created in the absence of Oxygen…
Momara
- 63