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One star may look brighter to use because:1) It is closer to us, or

2) It is actually brighter.

The real brightness will vary mainly due to the star's mass, as well as the point in the star's development. For example, once a star runs out of hydrogen, and fuses helium into heavier element, it will get brighter.

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7y ago
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14y ago

There are variable stars which alter their rate of fuel burning and flare up regularly

'Cepheid variables' are one type and are known as 'standard candles'. They can help us measure distances to stars.

Another is 'binary stars' where two stars orbit each other and we are in the same plane.

We see the dimming or occultation as one star passes in front of it's twin.

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11y ago

There are two major factors that determine a star's brightness - it's size (red giant, blue dwarf, etc.), and it's distance from the Earth. The numerical designation of a star's magnitude (brightness) will tell you right away if it is visible to the naked eye, or very faint. The lower the number, the greater the brightness; Sirius, the blue-white giant in Orion's sword, has an apparent magnitude of -1.44; while Betelgeuse, the red supergiant in Orion's shoulder, has a magnitude of 0.45. Generally speaking, blue or blue-white stars are the hottest, while those that are black are the coolest. A star's color is also determined by it's predominant elemental makeup - different gases and compounds have different wavelengths that appear to us as different colors. But regardless of a star's size, the light from all of them has been traveling towards us for a very long time - one light year equals six trillion miles, and most stars are many, many light years distant from us. Also,when you are studying the night sky, remember that 'stars twinkle, planets shine'. Planets shine with a much more steady light, due to the fact that they are so much closer to us than any star, and they are merely reflecting the sun's light, not creating their own. Hope this has been of some help to you - happy star gazing!

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11y ago

They don't, the earth moving changes our perspective of the stars, which stay rooted in the same position.

Actually, they DO appear to change position, because each night earth moves one part in 365 around the sun. So the stars appear to shift across the sky from season to season, as well as from evening to morning as the earth rotates.

Finally, the stars also change position with respect to each other. We don't notice because the change seems glacially slow from our vantage point. If you could chart their positions from one century to the next, you would notice small deviations.

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12y ago

The north star does NOT change; it's right there in the sky, a very long way away. It's the Earth that changes, wobbling like a gyroscope in a very slow circle. Right now, the axis of the Earth points toward Polaris, but it didn't always, and WON'T always. In a few thousand years, the Earth's axis will point to some empty spot in the sky, and in 13,000 years or so the Earth's axis will point, sort of, toward Vega. In 26,000 years or so, it will be back to pointing at Polaris.

Due to the precession of the equinoxes (as well as the stars' proper motions), the role of North Star passes from one star to another. Since the precession of the equinoxes is so slow, taking about 26,000 years to complete a cycle, a single star typically holds that title for many centuries.

Polaris' mean position (taking account of precession and proper motion) will reach a maximum declination of +89°32'23", so 1657" or 0.4603° from the celestial north pole, in February 2102. Its maximum apparent declination (taking account of nutation and aberration) will be +89°32'50.62", so 1629" or 0.4526° from the celestial north pole, on 24 March 2100.[1]

Gamma Cephei (also known as Alrai, situated 45 light-years away) will become closer to the northern celestial pole than Polaris around AD 3000. Iota Cephei will become the pole star some time around AD 5200.

The brilliant Vega in the constellation Lyra is often touted as the best North Star (it fulfilled that role around 12000 BC and will do so again around the year AD 14000). However, it never comes closer than 5° to the pole.

When Polaris becomes the North Star again around 27800 AD, due to its proper motion it then will be farther away from the pole than it is now, while in 23600 BC it came closer to the pole.

In 3000 BC the faint star Thuban in the constellation Draco was the North Star. At magnitude 3.67 (fourth magnitude) it is only one-fifth as bright as Polaris, and today it is invisible in light-polluted urban skies.

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14y ago

Stars appear change their locations in the sky in two ways - they rise in the East and set in the West each night just as the sun and moon do, and they change their apparent positions throughout the seasons. These motions are apparent, meaning the stars themselves are fixed and do not actually move1, but we observe them to move due to our frame of reference.

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The two types of apparent motion are explained below.

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  1. Stars rise and the East and set in the West because the Earth, when viewed from the above the North Pole, spins in a counter-clockwise direction, or toward the East. The stars remain in distant fixed positions, but as the Earth rotates, we observe the stars rise on the Eastern horizon as the patch of Earth we are standing upon rotates into view of the stars in question. As the Earth rotates under the stars, we observe them traverse the sky in exactly the same way the sun and moon do, until the stars set again in the Western horizon as our patch of Earth now rotates out of view of the stars.
  2. Stars change their position over the seasons in a manner similar to how a lighthouse sweeps a beam of light in a circle. The stars are observable only at night time, and the area of the sky you can see at night depends upon where the Earth is in relation to the Sun. As the Earth orbits the Sun, and as the seasons change from Spring to Summer to Fall and to Winter, the area of the sky you can see at night sweeps around the sun in a circle.

1 Note that stars do actually move, but for the purposes of this discussion, we assume their positions are fixed.

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10y ago

They vary in size of brightness and colour because it depends on if they are futher or closer to the planet Earth, and also the colour that you see is millions of years old.

There are two types of brightness and they are 'appearent brightness' and 'absolute brightness', the difference between these two are distance and energy output. Astronomers often refer to the total energy emitted by a star as its' "luminosity".

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14y ago

If you were in space looking away from the Sun that star would not vary in brightness The brightness as seen from Earth is dependent on the atmospheric conditions and the angle of viewing. When you view an object in the sky close to the horizon you are looking through more of our atmosphere, reddening the image and dimming the light. Overhead is the short path through our atmosphere, but you are still looking through many shifting layers of "air" that is of different temperatures.

The Hubble Space telescope is small compared to the much larger telescopes found here on Earth, but it's images are sharper because the view is not altered by looking through our atmosphere.

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12y ago

Because you're standing on the earth, and the earth is turning. As it turns, the

direction that your eyes are pointing keeps turning ... pointing at different stars

as time goes on. Since you don't feel the earth turning, and your body feels like

it's standing perfectly still, your brain has only one other way to understand why

your eyes keep pointing at different stars ... the whole sky must be turning!

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14y ago

Size and color are not directly related at all. The color of a star is instead related to it's temperature, with red (class M) stars being the coolest and blue stars (class O) being the hottest.

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