Hot answers tagged

88

It depends on where in outer space you are. If you simply stick it in orbit around the Earth, it'll sublimate: the mean surface temperature of something at Earth's distance from the Sun is about 220K, which is solidly in the vapor phase for water in a vacuum, and the solid-vapor transition at that temperature doesn't pass through the liquid phase. On the ...


55

There are two forces that can cause the formation of a tail: the solar wind and radiation pressure. The first misconception in your question is "the dust [travels] slower than the nucleus". The tail is not left trailing behind the comet, it is pushed away from the comet by the sun. When the comet is moving away from the sun, the tail is in front of the ...


47

Let's interpret your question to be about whether the conditions would permit blobs of water to remain liquid, whether or not water existed yet. And the answer is No, because the pressure was by then far too low. Basically, space was already a vacuum, just not as hard a vacuum as intergalactic space is now. It is appealing to imagine an era when the universe ...


43

It's more for safety than anything else. Space is a very dangerous place for so many reasons. And making mistakes can very easily cause death. Being weightless does not mean you lose mass, so momentum is just as difficult as ever. But whereas on the ground you can easily use friction to stop, in space if you try to stop against the floor you will just move ...


38

There are three main space weathering processes that will affect the surface of the marble. Cosmic rays, high energy particle from the sun and beyond, will hit the surface. This can change the chemistry of the surface. Solar wind particles, hydrogen and helium, can become implanted in the surface Micrometeoroids will impact the surface, causing small ...


37

It is a matter of exposure and dynamic range. A sensor like a camera can only handle inputs in a certain range of intensities, and much of photographic skill (or smart presets) is about mapping the outside light onto this range so the details you care about show up rather than turn into white or black. If you take a picture of a brightly lit scene, in order ...


35

First, there is not just one tail, it is several, but when traveling far from a star, they are "aligned". When it gets closer the different materials behave differently, both depending on the temperature they start to vaporise and how they are affected by solar winds. I think this picture shows it in a good way. https://community.dur.ac.uk/physics....


29

The outer parts of Neptune are mostly hydrogen and helium. There are small amounts of other gases such as methane, ammonia and water vapour. However, there is no oxygen at all. If you took some of Neptune's outer layer back to earth and mixed it with our air, it could burn. Even very cold hydrogen can burn (it soon heats up!) This couldn't happen on ...


23

You can stick a thermometer in space, and if it is a super-high-tech one, it might show you the temperature of the gas. But since the interstellar medium (ISM) is so dilute, a normal thermometer will radiate energy away faster than it can absorb it, and thus it won't reach thermal equilibrium with the gas. It won't cool all the way to 0 K, though, since the ...


21

As others have mentioned in the comments, there wouldn't have been any oxygen to form water. Soon after the Big Bang, the protons were hot or dense enough to fuse up to helium and some lithium but nothing heavier. Heavier elements were eventually fused in the first stars and partially dispersed in space by their winds and when they exploded as supernovae, ...


16

A self-sufficient orbiting telescope is basically Hubble mkII and would never get off the ground, literally and metaphorically Hubble was expensive because it was state-of-the-art, requiring development of many new systems. The systems it needed to function as a standalone satellite (compared to being attached to the ISS) were cheap by comparison (reaction ...


16

The disadvantages would likely outweight the advantages. It's cold out there. This makes it easier to keep an infra-red telescope cool The sun's just a super-bright star. This means more of the sky is visible and not in the glare of the sun. However you orbit so slowly that there will be a few objects that you won't be able to image because they are behind ...


14

Anders's answer is entirely fine, but I'd like to add some extra information. As evidenced by the transcripts, reflected Earth light is quite strong even at this distance: The earthshine coming through the window is so bright you can read a book by it. That is, even with the lights turned off, it would probably be tricky to see the stars unless you ...


13

Squinting works the same way as a pinhole camera. Ideally, light from a single point source entering your eye anywhere on your pupil will be focused on a single spot on your retina. But this works perfectly only if you have perfect vision; otherwise light entering near the top of your pupil may be directed to a slightly different spot on your retina than ...


13

Key factors: How close is perihelion? Too close and it may be destroyed on its first pass. We know Halley's Comet, which has a perihelion of about 0.6AU, has been orbiting for over 2000 years, passing the sun every 74-76 years and is still going strong. How big is it? Every pass loses material, so a bigger comet could last longer. What is its composition? ...


13

It would sublimate. The frozen mass of water would decrease in size as the water converts from a solid to a gas (without becoming a liquid) and drifts away.


13

Recently NASA has revealed that they have recorded the sound of Sun. They say that it produces a sound like "Om". I can't understand how they can hear it. It's not that recent (it was 2010), it wasn't NASA (it was researchers at the University of Sheffield who used data from a NASA satellite), it wasn't sound per se (it was instead sonified data), and ...


13

Not sure if these kinds of questions are allowed here, but I may as well answer it. Universe Sandbox 2 is mostly realistic. Its accuracy degrades as you increase the flow of time. The slower the time, the more accurate the calculations. This means that if you want to simulate the Solar System over a long period of time, it won't be very accurate. If you ...


12

If so by how much does it "spoil" the view of stars and galaxies etc. There are several very different issues related to your question. Let's tackle them one by one. Atmospheric refraction Yes, the Earth's atmosphere refracts light. One notable effect is that objects near horizon appear higher than they should be. Therefore, the Sun (or any other object) ...


12

When we talk about the universe, we are really talking about one of two things: The observable universe, which is everything we can possibly see. The Universe, which is everything that has ever existed, currently exists, and will exist. The observable universe has its own center, usually the Earth. It is a spherical region of everything that we can see, ...


12

Yes the Sun has an atmosphere. Disclaimer: I'm not sure if you meant this, but your question implies the Sun is a planet. It, of course, is a star and not a planet. Just wanted to make that clear. What is an atmosphere? When you ask if the Sun has an atmosphere, you're actually asking a tricky question. What do you mean by atmosphere? How do you define ...


11

Yes, and no. You will be able to see your hand's silhouette as it blocks incoming light from other sources, but you won't be able to see any features on it. For example, illuminance of starlight overcast moonless night sky is quoted at $0.0001\ lux$ which means that in absence of a brighter light source, human eye simply isn't that sensitive to such low ...


11

There is, believe it or not, a scientific theory regarding this: panspermia. According to the panspermia hypothesis, microbes "hitch" a lift on bodies leaving a planet. They then travel through space and eventually land somewhere else. Panspermia involves three difficult phases of travel: Launch (as well as the impact event) Travel in the harsh environment ...


10

Currently New Horizions is temporarily hibernating; it's last activity was two months ago. So I'm going to post a supplementary answer here because it is "operational" in the sense that it still works and will be used again, even though it is not "active" at the moment. The most recent and farthest-from-earth telescopic observations that ...


9

Any object with mass (even you) has gravity. The mutual attractive force between two objects is given by the formula $$ F = G \frac{M_1 M_2}{R_{12}^2}, $$ where the two mass are $M_1$ and $M_2$ and $R_{12}$ is the separation of their centres of mass. So to answer your question we need to define some sort of parameter that specifies what you mean by "...


9

Yes, space is constantly being created. The new space does not hold any matter (like atoms) or dark matter. This means that the density of normal and dark matter decreases at the same rate as the volume increases. However, dark energy, which is something completely different and thought to be a property of vacuum itself, is being created with the new space, ...


9

Even if a virus came to Earth from space, it would likely be harmless to life on Earth. Let's look at some biology numbers: Life on Earth uses 20 amino acids (out of about 400 considered chemically potential alternatives). The median length of a protein on Earth is about 300 amino acids. That's 20^300 combinations. And some proteins are 30,000 amino acids ...


9

OK, Imagine the stars at distance x block an area of the sky. At a distance of 2x there should be four times as many stars, but they would seem four times smaller in terms of area covered. Thus, the blocking grows linearly until a significant part of the sky is blocked. The stars within 20 light years (excluding the Sun), blocks approximately $4.3 \cdot 10^{-...


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