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98 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

The comet's tail always points away from the Sun. Yes, even when the comet is heading back into the outer solar system. This is because the tail isn't a 'trail' of where the comet has been, like a ...
Ingolifs's user avatar
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55 votes
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Why do many comets & asteroids keep moving through the solar system, but space ships need fuel to do so?

Your assumptions are incorrect. A space ship (once it has escaped Earth) will also continue travelling - in fact it will only need fuel to change its trajectory and velocity outwith gravitational ...
Rory Alsop's user avatar
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26 votes

How hard is it to fly through the tail of a comet? Has it been done?

Ulysses, the shuttle-launched joint NASA/ESA probe to study the sun's polar regions, ran through three comet tails, more or less by chance. Ulysses Catches Record for Catching Comets by Their Tails ....
Organic Marble's user avatar
21 votes

Can a meteor shower have a interval greater than 1 year?

This is really more of a question for Astronomy.SE, in general this doesn't happen, but circumstances can work out that it does, see the updated last few paragraphs. Every meteor shower with an ...
notovny's user avatar
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20 votes

Can a meteor shower have a period of less than 1 year?

Answer: Yes, but only if the debris orbit’s Latus Rectum is in the plane of the ecliptic and the Semi Latus Rectum is 1AU. Meteor showers will be 6 months apart, but have different radiant points so ...
Woody's user avatar
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17 votes

Why do many comets & asteroids keep moving through the solar system, but space ships need fuel to do so?

Spaceships will keep travelling in their orbits just the same as comets or asteroids, without fuel. The exception is that spacecraft in low orbit are affected by the upper fringe of the atmosphere, ...
ikrase's user avatar
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15 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

If you're the comet, the way to hit Earth is not to head directly for it. That's because Earth is orbiting the sun: you need to aim at where Earth will be, not where it is right now. For example: By ...
Phil Frost's user avatar
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15 votes

Does it make any scientific sense that a comet coming to crush Earth would appear "sideways" from a telescope and on the sky (from Earth)?

While those movies probably do it because that's how comets are commonly depicted, it might not be that inaccurate. Remember that the Earth itself is moving around the Sun, so if a comet is heading ...
Pitto's user avatar
  • 1,196
15 votes

How hard is it to fly through the tail of a comet? Has it been done?

Rosetta collected dust from 67P/Churyumov-Gerasimenko and analyzed it under an atomic force microscope, without landing on the cometary body itself; depending on your definitions this would seem to ...
Russell Borogove's user avatar
14 votes
Accepted

How can stellar images be "subtracted" from a sequence of exposures? (difference imaging)

The principles of Difference Image Analysis (DIA) or Difference Imaging, which is very common in modern astronomy for finding new transient sources (e.g. asteroids, variable stars, including ...
astrosnapper's user avatar
  • 2,506
12 votes

How hard is it to fly through the tail of a comet? Has it been done?

The two Vega probes comes to mind, ending their implausible sounding mission of slipping balloons into the atmosphere of Venus with a flyby of Halley's comet in 1986. They took a heavy beating flying ...
SE - stop firing the good guys's user avatar
11 votes
Accepted

Which are the main challenges for sample return mission from an asteroid and a comet?

There is a lot that the two missions you mentioned--Stardust and Hayabusa--have taught us about sample return. Sample Contamination: Serious measures were taken with Stardust to control for the ...
called2voyage's user avatar
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10 votes

How hard is it to fly through the tail of a comet? Has it been done?

The International Cometary Explorer spacecraft passed through the plasma tail of 21P/Giacobini–Zinner in September, 1985, which I think was the first time the human race had engineered such a ...
MadHatter's user avatar
  • 201
8 votes

What forms of water ice have been observed and verified in the solar system?

Actually, Ice VII has been discovered in diamonds on Earth. The water is first trapped in the diamond as the latter is formed deep in the mantle. Then when the diamond cools at the surface its rigid ...
Oscar Lanzi's user avatar
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8 votes
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What speed did the (interstellar) comet C/2017 U1 PANSTARRS have at perihelion?

Taking q = 0.2531011 AU (perihelion radius) and e = 1.1937160 from the latest ephemeris for A/2017 U1, we get a semimajor axis ...
Chris's user avatar
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8 votes

Why do many comets & asteroids keep moving through the solar system, but space ships need fuel to do so?

If there were no forces on an object, then Newton's First Law tells us that a stationary object would remain stationary, and a moving object will keep moving. So a moving comet or asteroid keeps ...
DrSheldon's user avatar
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7 votes
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What exactly is an F-mission?

It is a “Fast Mission” opportunity. These are missions that address an opportunity in the near future that would possibly be missed with the normal mission development timeline. Historically, ESA ...
Ludo's user avatar
  • 14.4k
7 votes

Comet at Mars L1

TL;DR: It wouldn't work, because you wouldn't be able to keep the comet at L1. The collinear Lagrangian points (L1, L2, and L3) are unstable; if a body were to be placed at one of these points, any ...
Vikki's user avatar
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7 votes
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What forms of water ice have been observed and verified in the solar system?

The only form of ice that we see naturally in bulk on Earth is Ice I, all within the sub-h variety. There's no place on Earth that gets cold enough for any other form--but that's not necessarily true ...
Justin Eiler's user avatar
6 votes

Could Rosetta find its way back to Earth?

I used the JPL Horizons database and downloaded the predicted positions (state vectors) of Earth and Comet 67P at 10 day intervals from 1600-Jan-01 to 2500-Dec-01. edit: As @pericynthion pointed out ...
uhoh's user avatar
  • 149k
6 votes

Why is comet deflection so hard (and how does a fusion rocket help)?

Assuming that our vaporization is at least as effective as a rocket engine (ISP 500) that gives 2.5m/s delta v Unlikely - the rocket engine uses a shaped engine bell tuned to give the best thrust (...
Andy's user avatar
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6 votes
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Puzzler; "who" are the members of this family of comet-visiting spacecraft?

These are all space probes that have visited or investigated comets throughout history, mostly from the Halley Armarda, a group of probes launched to investigate Halley's Comet during its 1986 ...
Jack's user avatar
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6 votes
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Are there any specific plans for how to deal with near-Earth comets? If not, should there be?

The threat from comets gets a lot less attention for several reasons: the threat from comets is about 1% of that from asteroids (executive summary of the 2017 Report of the Near-Earth Object Science ...
astrosnapper's user avatar
  • 2,506
6 votes

Why do many comets & asteroids keep moving through the solar system, but space ships need fuel to do so?

As other answers have said, they don't need to for maintaining speed. Back in the 1600s, Isaac Newton discovered maths for the movement of objects which matched observations, especially the movement ...
Graham's user avatar
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5 votes

Why isn't "cylindrical alien derelict spacecraft" more common in theories of Oumuamua as an alien probe?

tl;dr: In order to maintain plausibility they chose something plausible. The abstract includes the following: The observed trajectory is best explained by an excess radial acceleration $\Delta a ∝ r^-...
uhoh's user avatar
  • 149k
5 votes
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Evidence of Water D/H Ratios of Kuiper Belt Comets

I was wondering, are the comets 67P/Churyumov-Gerasimenko and 103P/Hartley 2 the only Kuiper Belt comets to date that have their water D/H ratio measured? Have we determined the water D/H ratio of any ...
Rob's user avatar
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5 votes
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Why not use Halley's Comet as a probe?

There are a number of reasons: When it's near the Sun (anything less than a few AU) a comet evaporates quickly, so it's not a safe place to be in. If you put the probe in the wrong place, ...
Hobbes's user avatar
  • 127k
4 votes

How long could a satellite orbit a comet without any control?

Comet 67P/Churyumov–Gerasimenko has a mass of about 9.982 gigatonnes, a semimajor axis of 3.4630 AU, and an eccentricity of 0.64102. If it was a point mass, it's Hill sphere would be about 221 km. The ...
David Hammen's user avatar
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4 votes

Why is comet deflection so hard (and how does a fusion rocket help)?

I don't have an exact answer but some relevant bits of information: You're looking at how much material is vaporized. That's irrelevant, vaporizing material gets you nothing. To move the comet you ...
Loren Pechtel's user avatar
4 votes

Why is comet deflection so hard (and how does a fusion rocket help)?

The simple fact is that we don't know what the effects of a nuclear blast on a comet would be as it's never been done, and each comet is different. You're thinking of a nuclear explosion next to a ...
GdD's user avatar
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