Galaxies

When the core of a massive star is compressed during a supernova explosion, then collapses into a neutron star, it retains most of its angular momentum.

Since it has only a tiny fraction of its original radius, a neutron star is formed with a very high rotational speed.

A pulsar is a highly magnetised, dense neutron star emitting a beam of electromagnetic radiation.

A few hundred

To gather information using either X-ray, UV rays, and such to further our knowledge on the unknown universes out there.

At it most basic level, the answer is "We DON"T know that all galaxies are moving away from each other." However, IF (indeed) space is expanding as proposed by Georges LeMaitre, then we would see all distant galaxies moving away from our own, and the rate at which they are moving away from us would depend on the distance to those galaxies.

FACT 1) That's exactly what we see.

Note also that, if LeMaitre is correct, then all other observers in our Universe we also see exactly the same thing.

FACT 2) If the expansion we now see has been ongoing since the start of that expansion, then we would ALSO see microwave radiation coming to Earth with almost perfect isotrophy and with a black-body spectrum of about 4 degrees Kelvin. We also see exactly that.

Fact 1 COULD be explained by our Milky Way Galaxy just happening to be the ONE galaxy, out of the 170 billion we know about -- a large fraction of which are pretty much identical to ours -- that was at the point from which all matter started expanding from. That is an EXTRAORDINARY unlikely occurence. It is MUCH simpler to assume that we are NOT at that center, and that all the other tens of billions of galaxies that resemble ours, are no more (or less) special in our Universe.

In addition, Fact 2 can NOT be explained by the assumption of our galaxy being at the point from which matter began to expand.

The assumption that we are NOT at some special place in our Universe both (1) is a more reasonable assumption and (2) explains more of what we see in our Universe.

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The best supporting evidence that the universe is expanding is that galaxies are receding from one another, indicating that the universe is expanding over time. This observation is based on the redshift of galaxies, known as Hubble's Law.

The observable Universe has at least a hundred billion galaxies. The galaxies closest to us are part of the so-called "Local Group" (that is, the group that includes our galaxy); this Local Group includes our own galaxy (i.e., the Milky Way), the Andromeda Galaxy, the Triangulum Galaxy, and about 50 dwarf galaxies such as the Large Magellanic Cloud and the Small Magellanic Cloud. Then, of course, there are hundreds or thousands of galaxies "near-by" as distances between galaxies go, but outside of our Local Group.

We can only speculate on the common paths of advanced civilizations, based on what is required by the universe as we know it. There are certain common obstacles that need to be overcome for any species to become truly advanced.

The common path would need to include these steps:
1) Evolve intelligence
2) Develop tool use
3) Group behavior (language, cooperation)
4) Dominate local environment (dependable survival)
5) Develop technology
6) Create dependable sources for all needs (farming, mining, energy, water)
7) Deal with all local and short term threats (extreme weather, predators)
8) Deal with all global and long term threats (ice ages, asteroids)
9) Deal with threats within the solar system (species on local planets, age of the sun)
10) Deal with threats outside the solar system (super nova, gamma ray burst)
11) At some point it will be necessary to leave the solar system.

At some point during the last four steps, any technology would need to master at least chemistry and energy. It's likely that several other sciences would be mastered as well.

The only way for a civilization to avoid the eventuality of leaving their solar system is for them to develop a technology so advanced that they can survive a local red giant, super nova, or the remaining dwarf sun that remains. Whether they leave or stay, their technology will be so advanced that the normal survival needs that we are familiar with, will no longer apply.

The net result seems to be that any advanced civilization that is not yet able to leave their own solar system will be competitive to some degree, but once they advance to become truly interstellar, they will be so self sufficient that there will be no need to compete for anything.

Stephen Hawking once pointed out that any advanced civilization probably evolved from a predator species. Since any home world would have a limit to it's available space and resources, competition would be required at some point in the evolution of an advanced species. In our case, we competed with other carnivores to get our food and to prevent us from becoming a meal for others. Now that we have dominated the other species, we compete with our own.

Other home worlds could have some differences. A water world might have an intelligent invertebrate species, but in order to become truly advanced, it would still need to dominate it's local environment enough to focus on technology and not just mere survival. A solar system with more than one intelligent species on multiple planets would present different challenges. When the species advance to the point of leaving their home worlds, they will encounter each other and it will end in conquest (Spaniards vs. Mayans), integration (Romans vs. everyone), or blending (Anglo vs. Saxons).

Regardless of how they get there, any advanced civilization will eventually need to confront the long term threats to their survival; Ice ages, super volcanoes, asteroid impacts, and the inevitable death of their sun. We now know how to eliminate these threats, but doing so is another thing. For example, knowing that removing Panama will restore the Pliocene Epoch ocean circulation of 2.5 million years ago and thus stop the cycle of ice ages is quite a far cry from actually doing it. Likewise, knowing how to use the gravitational tug of asteroids to nudge the earth out to the orbit of Mars and thus escape the heat of our dying sun is nothing compared to amassing the will to do it.

Due to the enormous distances between the stars, any advanced civilization that is able to become truly interstellar will have mastered technology and the sciences to such a degree that the things we need for our survival will seem as pointless to them as us needing a sharp rock. In other words, by the time they get here, they won't need anything that we have or can even imagine.

We have no idea and never will.

The 6th biggest planet in the Solar System is Venus.

All types of galaxies have a core with a high star density. All galaxies with "arms" are called Spiral Galaxies, of which there are sub-types related to the shape of the arms.

Recent evidence suggests that the Milky Way is a barred galaxy, and does not have a bulge in the classical sense. One estimate for the thickness of the central part of the Galaxy is ca. 16.000 ly. But if I were you, I would not put too much stock in this answer: astronomers are still learning new things about our galaxy every day, and the figure may well double - or halve - come next month.

A radio galaxy is anactive galaxy that is very luminous at radio wavelengths (between 10 MHz and 100 GHz). The radio emission is due to the "synchrotron process" which is caused by the acceleration of charged particles, near the speed of light) through magnetic fields.

An independent expression, often lacking an antecedent, attached to a sentence as a prepositional phrase. For example, "in any case, I wouldn't care." (Coincidentally, "for example," as used in the previous sentence, is an elliptical phrase.

I am not sure there is one. Galaxies contain stars, gas, dust, black holes and other dead stars, and - above all - dark matter. The dark matter typically makes up 80-90% of a galaxy's mass.

I am not quite sure what you mean by "independent". It is gravitationally bound to our galaxy (the Milky Way); that is, it rotates around the center of the Milky Way.

Yes the black hole can be destroyed. However, man-made objects cannot resist the gravity without getting sucked in. The only thing that can destroy a black hole is time in a process called Hawking Radiation in which the black hole evaporates over time. The smaller the black hole, the faster the process.

The vast distances involved means that the light we see left those galaxies a long time ago.

An irregular galaxy is a galaxy that does not have a regular shape, like a spiral or an elliptical galaxy.[1] The shape of an irregular galaxy is uncommon - they do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.[2] Collectively they are thought to make up about a quarter of all galaxies. Most irregular galaxies were once spiral or elliptical galaxies but were deformed by gravitational action. Irregular galaxies also contain abundant amounts of gas and dust.

Samsung.

No, it is not a 'real' galaxy, merely one that exists inside the movie world. It is based upon Science Fiction, and you will not be able to travel to it.

Based on a conservative estimation of rotational time around the galaxy, the next "cosmic year" will be in about 110 million years.

No. A circle is a 2-dimensional shape, while a galaxy is a 3-dimensional object. The 3D analogue of a circle would be a sphere, and "irregular" galaxies and globular clusters are sort-of spherical, but only if you look at them through fuzzy glasses.

Comment: A spiral galaxy like the Milky Way is a sort of disc and that's "circular" perhaps, in everyday language.

A galaxy is a massive, gravitationally boundsystem that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter.

Leo is a constellation, that is to say, a direction in the sky. Just as in any other constellation, there are lots of galaxies in this constellation.

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