Milky Way Galaxy

A "day" is basically the time Earth rotates around its axis. Sometimes people talk about a "day" on other planets, which can be anywhere between a few hours and several months. There is no commonly accepted equivalent for the Milky Way.

Astronomy

In the late 1920s, the astronomer Edwin Hubble discovered that most of the galaxies he observed were moving away from Earth.

Pluto is a part of our solar system, and our solar system is a part of the Milky Way Galaxy. Thus: Pluto is a part of the Milky Way.

The Milky Way's diameter is about 100,000 light-years.

No. Our entire solar system is located within the Milky Way Galaxy. The largest object between Mars and Venus is Earth.

No, it is a spiral galaxy.

100,000 light years across

nine

We only know a handfull of planets of all of planets in the Milky Way galaxy, but there are pretty bad planets even in our own solar system.

Mercury is so hot, that all life would die in there, if life would have ever been able to emerge there. Venus is too hot for life too, it's atmosphere is full of corroding acid rains and it's surface covered with numerous volcanoes. Earth is the only planet suitable for life in our solar system. Mars is dry and too cold for living, all of it's water is frozen in its polar caps and under the rocky surface. Mars doesn't have an atmosphere either, so there is no air to breathe and all the dangerous space radiation comes straight to its surface. Jupiter is completely inhabitable, as well as Saturn, Uranus and Neptune. All four are huge gas planets, they don't have a solid surface at all, only gas is surrouding their cores, and they are also so far away from the sun that they are very cold. Those planets many many times bigger than Earth also have immensely heavier gravity, which would crush a human body if it would stand on some surface. Also huge cyclonic storms are wandering on Jupiter and Neptune, the Jupiters "eye" storm is so big, it could swallow three whole Earths.

Pluto which used to be a planet, but is better to categorize as a planetoid since it's so very small, is only a tiny ice ball so far away that the sun doesn't look much different than the other stars on Plutos sky. So it's extremely cold place with eternal night.

There are still worse planets in the Universe and in Milky Way, every planet which doesn't have a sun, if their sun has gone to an end, are completely impossible for life to exist, since they don't have light, which makes all life possible. Also it would be pretty horrible to be on a planet which' sun would die as a red giant turning to a supernova and destroy the whole planet and every life form on it. Everything would burn, oceans boil and mountains melt and the planet would turn into a giant ball of lava until the supernova would blow everything away.

Milk + Space

It condenses and turns into vapour which is known as "steam".

Big. Very big.

Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory

Solar System

The Milky Way probably has billions of planets; only about a thousand are known so far.

cooler particles are slower moving thus more dense. the more dense the material the further it will sink

Perspective

Since our galaxy is about 100,000 light-years side to side and we are about 30,000 light-years from the centre of our galaxy then by dividing 100,000 by 2 making it 50,000 and then minus 30,000 then it estimates we should be 20,000 light-years from the nearest edge of our galaxy.

The Milky Way galaxy will not melt or dissolve; it will continue to exist for billions of years. However, the Milky Way is on a collision course with the Andromeda galaxy, and they are expected to merge in about 4 billion years.

• Milky Way Galaxy
• Galaxy

"The halo primarily contains individual old stars and clusters of old stars ("globular clusters"). It may be over 130,000 light years across. The halo also contains "dark matter," which is material that we cannot see but whose gravitational force can be measured." to shorten the answer - individual stars, clusters, and dark matter.