How long it takes for our planetary system to complete one rotation in the Milky Way?

Answer 1

It will take some time: Period for Solar System (sun,earth, etc.) to circle the Milky Way is about 225,000,000 years

Answer 2

Stars revolve around the center of galaxies at a constant speed over a large range of distances from the center of the galaxy. Thus they revolve much faster than would be expected if they were in a free Newtonian potential. The galaxy rotation problem is this discrepancy between the observed rotation speeds of matter in the disk portions of spiral galaxies and the predictions of Newtonian dynamics considering the visible mass. This discrepancy is currently thought to betray the presence of dark matter that permeates the galaxy and extends into the galaxy's halo.

In 1978, the first observational evidence was reported that spiral galaxies do not spin as expected according to Keplerian dynamics.[1] Based on this model, matter (such as stars and gas) in the disk portion of a spiral should orbit the center of the galaxy similar to the way in which planets in the solar system orbit the sun, that is, according to Newtonian mechanics. Based on this, it would be expected that the average orbital speed of an object at a specified distance away from the majority of the mass distribution would decrease inversely with the square root of the radius of the orbit. At the time of the discovery of the discrepancy, it was thought that most of the mass of the galaxy had to be in the galactic bulge, near the center.

Observations of the rotation curve of spirals, however, do not bear this out. Rather, the curves do not decrease in the expected inverse square root relationship but are "flat" -- outside of the central bulge the speed is nearly a constant function of radius. The explanation that requires the least adjustment to the physical laws of the universe is that there is a substantial amount of matter far from the center of the galaxy that is not emitting light in the mass-to-light ratio of the central bulge. This extra mass is proposed by astronomers to be due to dark matter within the galactic halo, the existence of which was first posited by Fritz Zwicky some 40 years earlier in his studies of the masses of galaxy clusters. Presently, there are a large number of pieces of observational evidence that point to the presence of cold dark matter, and its existence is a major feature of the present Lambda-CDM model that describes the cosmology of the universe.

The nearly imperceptible "sideways" motion of a galaxy has been directly measured for the first time beyond the Milky Way and its immediate galactic neighbours. The observation will improve measurements of astronomical distances and nearby dark matter concentrations.

Astronomers study how a celestial object moves by breaking down its motion into two components - movement along the observer's line of sight, called radial motion, and movement across the sky, called proper motion. The first can be measured by studying changes in the wavelength of light, called Doppler shifts, as objects move toward or away from Earth.

But side-to-side motion does not affect an object's spectrum, so astronomers must track changes in an object's location relative to background stars. This is quite easy for objects in the solar system, such as asteroids, or even for objects in the galaxy, by "triangulating" their observed positions from two different points along Earth's orbit.

But simply tracking an object's visible light cannot reveal movement much beyond the Milky Way - because the objects are so distant, they appear motionless.

To answer your question, The Sun's orbit period about the center of the galaxy (the "galactic year") is currently reckoned to be about 230 million years. and the arm of our local galaxy, the Milky way seems to be traveling at a constant speed.

Rigid structures (like pinwheels) will not last in a rotating disk galaxy because the galaxy is rotating differentially - stars far from the center fall behind stars close to the center because all stars orbit at about the same speed. A pinwheel pattern would completely disappear after a few galactic rotations (a billion years, or so). Galaxies like the Milky Way are about 10 billion years old, so any pattern established when the galaxy came into existence should have long ago disappeared. The pattern in maintained instead by a kind of wave, which never disappears. Spiral arms are 'traced' by objects such as O and B stars, and emission nebulae. O and B stars do not live long so cannot have moved far in the galaxy since their birth. Finding them associated with spiral arms thus suggests they were formed in the arms. Emission nebulae exist only near hot stars (like O and B) stars, so to find them in the spiral arms implied the presence of O and B stars. Again, these O and B stars must be located near their birthplaces - evidently the spiral arms.

Answer 3

Yum, I LOVE Milky Ways!

Answer 4

milky way what is it

Answer 5

what blapath said