Is galaxy a group of stars bound together by gravity?

Answer 1

Gravity does somewhat hold galaxies together. However, at the current estimated speed of the galaxy, gravity alone is not enough to keep the hundreds of thousands of stars from flying off into space. Therefore, it has been proposed by many cosmologists and astrophysicists that there is an "invisible" matter out there called dark matter which may make up 99% of the universe. This adds enough mass to the galaxy and along with gravity holds the galaxy together.

Answer 2

Yes, a galaxy is a massive system of stars, stellar remnants, interstellar gas, dust, dark matter, and other objects, all bound together by gravity. They can contain millions to billions of stars, and come in various shapes and sizes.

Answer 3

Everything with mass has gravitational attraction to other object with mass.

The Sun pulls on you with its gravity, but you also pull on the, yourself. Not much, understand, but a tiny bit. You and your friend Travis exert a gravitational pull on each other.

Only with massive objects is the gravitational attraction noticeable to us humans. That includes stars.

Answer 4

No. The apparent movement is caused by the rotation of the earth, not by movement in the stars.

On the other hand, yes, the stars DO move, but their apparent motion is so slight many thousands of years would be required to discern significant difference.

Answer 5

Astronomers and physicists know that the stars within a given galaxy move a little relative to one another*, but staying together is part of what makes any group of stars a galaxy. The relative movement is not strongly related to the big bang or to the expansion of space-time initiated at the big bang. The Milky Way is rotating around its center, at which there is believed to be a super-massive black hole. This rotation is relative to the distant galaxies, and we have no way of observing it with the naked eye. The relative stability of the Milky Way as it rotates accounts for the apparent 'fixed' locations of what we call the fixed stars. The stars we see in the night sky arevirtually all members of our Milky Way.

The stars that are moving away from us (an astonishing number compared with the number of stars in our Milky Way) are in the other galaxies. Some galaxies travel in groups, as odd as that sounds. The Milky Way is part of what we call the local group, and one of our group, the Andromeda Galaxy, is moving toward us and not away from us. We are in fact on a collision course with Andromeda, but don't sell the farm just yet. The collision won't happen for 5 billion years or so, and by then the earth itself will be facing its own end, if it has not already ended. Because Andromeda is a member of our local group, its movement toward us does not refute the overwhelming evidence that distant galaxies are moving away from us.

*It is utterly fascinating that one of the movements of the Milky Way's stars relative to each other involves the arms of our galaxy in a most unexpected way. When we see photographs of spiral galaxies, isn't it easy to imagine that the stars within a given arm remain more or less together as an 'arm', and they move around the center intact? The fact (according to our latest knowledge) is that the arms really represent a kind of 'wave'! As you might imagine molecules of air compressing and then separating as a wave of sound travels through, the stars of a given arm are simply in a 'compression' phase, and they will at some point pull away from one another and 're-group' as the wave passes by. Equally curious is the fact that the Milky Way, relative to the distant galaxies, rotates in the direction of the pointing of the arms, counterintuitive to what we would guess based on our earth-bound experience of moving things.

Answer 6

The stars move. Everything in the universe is moving, including our sun. The sun is in one arm of the Milky Way Galaxy that is moving around the center of the galaxy, like everything else that's in it. The galaxies themselves are moving away from each other, and if current analysis is correct, their movement away from each other is accelerating. There is not a single thing in the universe that can be thought of as stationary. Actually, the truth is, Stars actually DO move, but very slowly. See, since they are so far away, you won't see them 'move'. If they were closer, then perhapes you would see them move faster. This is why we see different constellations throught the year. As for the Sun, it does infact move. It moves around the Milky Way in an almost circular orbit. The Sun actually completes one revolution in about 230 million years.

the sun doesn't move but the stars do, very very slowly.

Answer 7

Gravity is determined by mass. EVERYTHING has gravity. The more mass, the more gravity.

Yes

Gravity is a property to be associated with all matter (with mass) in the universe.

Indeed all stars exists in a constant balance of gravity squeezing them smaller and the nuclear reactions in their cores trying to make them explode apart. Gravity eventually wins as stars run out of nuclear fuel to keep them going.

Put this into perspective on Earth if you fall off a 1 meter ladder you would hit the ground at roughly 7mph now if you fall off that same ladder on a neutron star (which is roughly 12km in diameter) you will hit the ground at a whopping 1.5 million mph.

Answer 8

Stars appear to move across the night sky because Earth rotates, so you might see one star on the far left of the sky at dusk, but near dawn it could be far right, or not even visible from your position on earth.

Answer 9

Yes, the stars do change position relative to each other. The effect is most noticeable for those that are fairly close to us.

Answer 10

False. As every "Men In Black" viewer knows, a galaxy is millions and millions of stars.