Why don't the stars in the sky change?

Answer 1

They do change. Stars go through a life cycle being born, aging, dying (sometimes with the bang of a supernova & sometimes less dramatically). However, they do this so slowly that we rarely see it. (See: http://en.wikipedia.org/wiki/Stellar_evolution)

They also move across the sky. Their actual speed of movement (eg: in mph) is massive but because they're so far away it isn't noticable unless you compare photos taken over several centuries or more. For two stars travelling at the same actual speed the one which is furthest away will appear to us to be travelling more slowly.

There are star maps from 2000 years ago. Comparing these with our modern star maps shows that some of the closer stars have moved. This means that some of the constellations have changed shape since that time.

Answer 2

Boy do they change and how !!!
Everything up there is in constant motion. The sky looks different every minute and every hour, you just have to pay close attention. Not only do the stars move across the sky, but they move in relation to each other as well.
The most obvious example often cited is polaris, the Pole Star. A few thousand years ago the Pole Star was Vega in the constellation Lyra. It is a long distance away from the pole now. It will be the Pole star again in a few thousand years. Individual stars change themselves throughout their lifetime. There are lots of stars that have exploded and we can watch the progress of their explosion even now. Whole Galaxies containing billions of stars collide with each other, throwing billions of stars out into space, pretty well ruining the star's day. Space is a very violent place if you look at it closely. It is by no means the serene and peaceful heaven portrayed in romantic writings.
Star atlases have to be re-published periodically to reflect these changes. Current Star Atlases are labelled "Epoch 2000". That means they were last corrected in that year.
Stars themselves are very violent places too, they are basically continuous Nuclear Explosions and are not as stable as they look.

Adolph

Answer 3

They do change. They are not fixed and eternal. They all have a proper motion i.e. are moving relative to one another

They will all one day exhaust their hydrogen supply and stop fusing hydrogen to make helium, and leave the main sequence when they do so. Blue giants will exhaust their hydrogen much quicker than red dwarfs, but the Grim Reaper will get them all eventually (the universe is only 13.7 bilion years old).

Two changes that are worth noting as people tend to think the North Pole Star is a permanent feature and the nearest star to the Sun is similarly a permanent part of the furniture ... are

(a) Polaris will no longer be the North Pole Star after 3,000 AD. The job will then be Gamma Cephei's until Iota Cephei takes over the role. By 14,000 AD the bright star Vega will become the Pole Star, as it was in 12,000 AD.

This is due to the precession of the Earth's axis. which pccurs over a cycle of 26,000 years in which different stars in turn are nearest to the north celestial pole. Polaris only became the Pole Star in about 500 AD, and before that it was Thuban, Alpha Draconis, that did the job in Biblical times.

(b) the nearest star to the Sun is presently Proxima Centauri. 4.22 light years away. It has been the nearest for the lasf 35,000 years and will be for another 9,800 years.

But by 11,800 AD, Barnard's Star, currently 5.96 light years away, will have approached to within 3.8 light years and taken over as the nearest star to us.

And within 1,400,000 years the red dwarf Gliese 710 currently 63 light years away, will have approached to within 1.1 light years of the solar system and could have an effect on the comets in the Oort Cloud, causing more of them to be dispatched towards the inner solar system.

So there are changes. They need more than a human lfetime to become visible but the Pole Star will change at the start of the next millennium and the nearest star will have changed within ten millennia, and these are but the blink of an eyelid in the timescale of the cosmos ...

Answer 4

The life cycle of a typical star is billions of years, so rate of change on the scale of a human lifetime is infinitesimal. Also, even though the stars are in motion, they are so far away that it takes careful measurements with telescopes to detect the motion. But come back in 100,000 years and many of our familiar constellations will have changed due to the motions of their stars.

However, there are many changes that do happen quickly enough to be observed. There are thousands of variable stars that vary over periods ranging from hours to years. Some of them, like Mira and Algol, undergo dramatic changes in brightness and have been known since man first charted the skies. Stars can also undergo sudden outbursts that change their brightness. In recent years there have been obvious (temporary) changes in Scorpius and Cygnus.

The most dramatic change of course is the supernova. There hasn't been a visible supernova in our galaxy for centuries, but they can be seen (with a telescope) even in far away galaxies, and dozens are detected every year.

With a telescope, you can track changes in variable stars, and also note the orbital motions of some binary systems. Because there are so many of these, this is an area where amateur astronomers with modest equipment can still make a useful contribution to science.

Answer 5

The stars do change over time, but any major changes that are noticeable by the human eye only occur every few billion years or so. Since most stars are far away, changes in hot spots, solar flares, etc... cannot be seen by us or even our telescopes yet. Stars have a very long life and major changes are difficult to come by because they occur every few billion years. They do evolve from yellow stars to red giants to black holes or dwarfs etc... Look for stuff with stellar evolution for more information.

Answer 6

Light from a star travels at the speed of light, so the light of a star in the sky could have been traveling to earth for millions of years before we see it now. it is possible that star no longer exists, its just the light from it that we see

Answer 7

They do, there's a probability that some of the stars visible to us may no longer exist in thier present form, or even at all. What we're seeing is an image thats in some cases is thousands of years old. If I remember correctly, the last supernova visible to the naked eye was in the 19th century (?)

Answer 8

They do. All the time. Stars explode, some are variable, switching from dim to bright, and their positions move very slowly over time, as we orbit the center of the galaxy together. We're only alive for such a short time (compared to the age of the galaxy), that we don't get to see the motion of the stars affect them significantly.

Answer 9

Stars are suns just like our sun. Some are bigger. Some are smaller. Like our sun, all of the other suns are travelling through space. Their vast distance from us makes their movements hard to detect unless you compare their positions today from where they were years ago. Sometimes tens and hundreds of years ago.

Stars, again like our own Sun, go through birth- life- and death. This is a process taking about 10 billion years but we can see the gases which are composed of new stars and we can see the death of stars in red giants, white dwarfs, supernovae, and black holes.

Other fuzzy points of light which you see in the sky at night are entire galaxies. These, like the Milky Way, are also rotating and moving through space (most of them moving away from us).

You will not see the stars in the sky change in one night. But if you took a photograph of the stars tonight and compare it with one that you take 50 years from now, you will see many of them change their positions slightly.

Answer 10

they do all the time, notice how that some are different colors? well the colors indicate there age.. the more orange or red they become the more older they are which means that they will explode and depending on the mass of the star they will become a black whole..