Why don't black holes suck in everything, everywhere?
Let me begin my answer to your inquiry by using the Sun as an example.
The Sun has a radius of 700,000 km (the Earth's, for comparison, is 3,380 km). This means that no object -- planet, comet, or other kind of satellite -- can get closer to the Sun than 700,000 km from its center, or it would enter the Sun's photosphere.
Now, imagine compressing the Sun into a black hole. To do this, you would have to compress it so that its radius is just three km! If you find yourself at three km or closer, you will never get away (nor will light) because you are in a black hole. If you are 4 km, 10 km, or 100 km distant, you can get away if your spaceship has sufficient engine power. The further away you are, the less power you need to get away. If you are 700,000 km away, the engine power you will need to get away from this imaginary black hole is no different from getting away from the real Sun. In other words, the gravitational field of a solar mass black hole 700,000 km away from its center is no different than the gravitational field 700,000 km away from the Sun. Likewise, the Earth's orbit would be the same around the real Sun and that imaginary black hole because at our distance (150,000,000 km from the Sun) the gravitational field is the same for both objects.
Matter that orbits at sufficient distances around the central core of a galaxy will not be affected by the presence of a black hole there. However, matter that gets close to the black hole will. This typically happens when a galaxy collides with another galaxy or two galaxies have a close encounter. When two galaxies get close to each other, they exert strong tidal forces on each other. That perturbs the motions of gas clouds. Some of them start spiraling toward the galaxies' centers (other gas clouds get pulled out and away from the galaxies). The gas that gets too close to the central black holes of the galaxies will fall into them and emit huge amounts of radiation (including gamma rays, X-rays, and UV radiation) and produce other kinds of violence. Such energetic events are known as quasars.
All quasars are very distant. Perhaps our Milky Way was once a quasar because it may have had a black hole and been involved in collisions with other galaxies. Such collisions would have been quite frequent early in the universe's evolution, when the galaxies were much closer to each other than they are today.
Are the pictures taken by the HST true-color images?
The HST color images are produced by combining three images of the same object taken through different filters. It's quite similar to the way ordinary color film works, which consists of three emulsion layers sensitive to different colors.
If you would like more detailed information on the filters used by HST, please write to the Space Telescope Science Institute Help Desk at help@stsci.edu
You raise the question of whether the HST colors are artificial. If by artificial you mean that the colors are different from those the human eye can see, they are artificial. In fact, by using different filters or increasing the exposure through one or two filters, one can greatly alter the final appearance of an image. The HST images are far more spectacular and beautiful than what our eyes would perceive if we looked through the HST.
A similar process of combining images taken in different wavelength bands exists in X-ray, UV, IR, and radio astronomy (as you note in your message). Here, too, one obtains beautiful images that contain much information. They let us see what the human eye cannot see at all. They, too, are "artificial."
The technical term for such image creation is "false color," meaning the colors do not correspond to what humans would perceive.
Most unlikely. People somehow like to believe in mysteries, in visitations from outer space, in magic, the supernatural, etc. For me there is so much beauty and mystery in nature that lends itself to scientific investigation, I feel no need to believe in the supernatural or hoaxes. But, obviously, different people have different needs and beliefs.
Could life evolve on other planets?
At present, NASA and the rest of the science community have no definitive proof that life exists anywhere in the universe but here on Earth.
However, even though definitive proof is lacking, most biologists, chemists, and astronomers who concern themselves with the origin & evolution of life would agree that it is highly unlikely for Earth to be the only place to have given rise to life.
There are at least two places in our solar system, besides Earth, where conditions might have been right for life to have started -- Mars and Jupiter's moon Europa. Mars shows strong evidence to have had flowing water early in its history and a mild climate. Europa shows evidence of having liquid water even today, possibly under a surface crust of ice. (The assumption most scientists make is that all life requires liquid water, carbon-based chemistry, and suitable sources of energy.)
Furthermore, there is evidence that stars other than the Sun have planets, although no evidence for an Earth-like planet beyond the solar system has yet been found. If other stars have planets, at least some of the 100 billion stars in our own galaxy, the Milky Way, may be assumed to have planets with surface gravity, composition, and temperatures comparable to those of Earth. Life could have -- or, very likely has -- originated on some of these planets. The probability goes up, of course, when considering all the other galaxies in the universe.
Is there really a tenth planet (planet X)?
Probably not, but we don't know for sure.
As you say, there are planets and asteroids. There are also the Sun, interplanetary gas and dust, charged particles that stream out from the Sun (called solar wind), comets, moons of various sizes orbiting most planets, and cosmic rays (charged particles that arrive from far beyond the solar system).
Sound does not travel through planetary space. The gas and dust of interplanetary space are too sparse. Sound requires a denser medium, such as the atmosphere of the Earth, other planets, or the Sun. Sound can also travel through solid material, especially stiff materials like steel. Sound consists of alternating compressions and rarefactions in the medium through which it travels. Those alternating compressions and rarefactions propagate along in a wave-like fashion at what we call the speed of sound. The stiffer the material or the hotter the atmosphere, the greater the speed of sound.
My above comments regarding planets, asteroids, interplanetary gas and dust, etc., apply to the space in the vicinity of the Sun. On a larger scale, there are roughly 100 billion stars that, along with interstellar gas and dust, compose the Milky Way galaxy. There are billions of other galaxies in the universe, the most distant of which are roughly 12 billion light-years away. If you'd spread out evenly all the matter in the stars and other bodies, you would find that in today's universe each cubic meter of space would contain just one proton and one electron. Not very much! (Very approximately, 1 meter = 3 feet.)
You might also ask about light. How does it propagate through space? It does not require a material medium. In fact, gas and dust tend to absorb light and make it hard to see very far (e.g., try looking through fog or clouds). Physicists don't know what makes light propagate. They only know that it moves along at roughly 186,000 miles/second and that it consists of oscillating electric and magnetic fields with wavelengths that range from the microscopic to many feet in length.
Do other planets have an effect on the Earth's tides?
How many satellites do we have in
orbit?
There are hundreds of them and if you count space debris (pieces of broken-up satellites) you'll get tens of thousands. Satellites are launched by many countries -- governments (secret and open) and private corporations (like communications and Earth-observing satellites). It's hard to keep track of them all.
Do you know when the Sun will blow up?
The Sun is about 4.5 billion years old. It will shine much as it does right now for about another 5.5 billion years. It will then become bigger, brighter, and cooler. Such stars are called red giants. The Sun will be a red giant for about 3 to 4 billion years. Finally, it will shed its outer envelope to make a planetary nebula (has nothing to do with planets, planetary nebulae are gaseous shells ejected by red giants). What remains is a hot, burned-out stellar core that cools and becomes a white dwarf, which is one of the end stages in stellar evolution. (Other end stages are neutron stars and black holes.)
In short, it will never blow up.
Not without an artificial life support system. The Moon has no atmosphere, its temperature variations are severe, there is virtually no water (unless the Lunar Prospector mission finds some at the lunar south pole, where an earlier Navy mission reported to have found indications of frozen water), and it's exposed to the Sun's UV radiation and to cosmic ray particles from the universe. On the Moon, people would have to provide their own oxygen to breathe and a pressurized environment. They would also have to protect themselves from cosmic rays and the Sun's UV radiation. They'd have to bring food and water. It would be a tough and expensive problem, especially if people plan to stay on the Moon for prolonged periods.
I'm looking for information about stars and constellations.
There are several places on the Web to find information on stars and constellations.