Stars rise in the northeast and set in the northwest, moving in counter-clockwise circles around a point that's high above the northern horizon: Half-hour time exposure facing north and slightly west, from the same location as the previous three photos.
Those stars that were low over the western horizon during the early evening hours would, within a matter of a few weeks, disappear entirely from our view, their places being taken up by groups of stars which, a few weeks earlier, were previously higher up in the sky at sundown.
This apparent westward drift of the stars, incidentally, is a motion that is in addition to the daily rising, circling, and setting. For our Earth does not simply stand in the same spot in space and spins, but is constantly rushing eastward along in its orbit around the Sun.
You’ll see that the star has apparently shifted slightly to the right (west) of the position that it was at the previous night. Had you arrived four minutes earlier, the star would have lined up exactly with the nearby landmark just as you had seen the previous night.
A little quick arithmetic shows that with a difference of two hours per month, that in one year the cycle will come full circle (12 months x 2 hours = 24 hours), since each star completes a full circle around the sky during the course of one year. This can be made clearer by trying an experiment.
This apparent motion is caused by a combination of earth's rotation, and its revolution around the sun. Earth's rotation can make it look like the stars circle the north star from east to west. Groups of stars called constellations also seem to move through the sky over the months.
As seen from the North Pole, over the course of the night the stars move in a parallel motion since all of the stars at this point are circumpolar. From the equator, they move across the sky in a semicircle overhead. Over the night, the stars travel along paths that are perpendicular (vertical) to the horizon.
Objects such as stars appear to move across the sky at night because Earth spins on its axis. This is the same reason that the sun rises in the east and sets in the west. Stars that are low in the east when the night begins are high in the sky halfway through the night and low in the west by daybreak the next day.
At the Earth's equator, the celestial equator passes through the zenith. The Earth rotates from west to east and hence the stars appear to revolve from east to west about the celestial poles on circular paths parallel to the celestial equator once per day.
These apparent star tracks are in fact not due to the stars moving, but to the rotational motion of the Earth. As the Earth rotates with an axis that is pointed in the direction of the North Star, stars appear to move from east to west in the sky.
1:492:52"Do the stars really move?" (Ask an Astronomer) - YouTubeYouTubeStart of suggested clipEnd of suggested clipMore. So the stars really move. Well their motion wending their way across the night sky is anMoreMore. So the stars really move. Well their motion wending their way across the night sky is an illusion caused by the spinning earth just as the Sun is seemed to move during the daytime.
When a star is moving sideways across the sky, astronomers call this “proper motion”. The speed a star moves is typically about 0.1 arc second per year.
The stars are not fixed, but are constantly moving. If you factor out the daily arcing motion of the stars across the sky due to the earth's rotation, you end up with a pattern of stars that seems to never change.
All the stars we see in the night sky are in our own Milky Way Galaxy. Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area. It is very difficult to count the number of stars in the Milky Way from our position inside the galaxy.
As Earth spins on its axis, we, as Earth-bound observers, spin past this background of distant stars. As Earth spins, the stars appear to move across our night sky from east to west, for the same reason that our Sun appears to “rise” in the east and “set” in the west.
The Earth rotates on its axis once every 24 hours. This results in a star appearing to move 1-degree every 4 minutes to the west. 15-degrees each hour. Telescopes that track the stars must be driven at that speed, 15-degrees per hour to the west.
The Earth rotates on its own axis from West to East. Stars, thus appear to move from East to West, due to the relative motion of them with respect to the Earth.
At the earth's north pole, you would see the north celestial pole straight overhead, and the celestial equator would lie along your horizon, so you would never see any stars rise or set; they would just move in counter-clockwise circles if you're facing upward, or horizontally to the right if you're facing the horizon.
From the North Pole, all of the motion of the stars is horizontal. Stars at the horizon skim along the horizon, never rising or setting. The stars higher in the sky also move horizontally, never moving up or down. From the poles, all visible stars are circumpolar.
At the South Pole every direction on the Horizon is North, and the stars move to the left or West while the Earth moves under them, to the East.
Each star orbits its galaxy's center and has a slight random motion on top of this. Each star does not careen randomly about like a drunkard. Rather, each star travels on a smooth, nearly-straight trajectory as dictated by its own momentum and the local gravitational field.
If you were standing at the Earth's north pole, the north celestial pole would lie at the zenith, the imaginary point directly over your head. The star Polaris would lie almost directly at this point.
As Earth rotates around its axis from west to east, the entire sky appears to rotate from east to west. As Earth orbits around the Sun, the darkened part of Earth faces different parts of the sky
During the summer, the sun's rays hit the Earth at a steep angle. The light does not spread out as much, thus increasing the amount of energy hitting any given spot. Also, the long daylight hours allow the Earth plenty of time to reach warm temperatures.
A fellow student tells you that only those stars in Figure 1-3b that are connected by blue lines are part of the constellation Orion. How would you respond?
Earth has seasons because our planet's axis of rotation is tilted at an angle of 23.5 degrees relative to our orbital plane - the plane of Earth's orbit around the sun. ... But the orientation of Earth's tilt with respect to the sun - our source of light and warmth - does change as we orbit the sun.
Constellations: Patterns of stars on the sky, help to identify particular stars. Not true 3-d groupings.
Motion of the moon sort of like sun. Follows celestial sphere each day, but moves relative to stars along a great circle. Differences:
To naked eye, planets look like stars, but they move around in the sky. Greeks called them "wandering stars" ( asterai planetai ).
The point in the sky directly overhead an observer anywhere on Earth is called that observer's zenith. If you were at the Earth's equator, the celestial equator
On the Summer and the Winter Solstice (around June 21 and December 21 respectively), the Sun reaches its most northern and southern declinations. People who live at a latitude of 23.5º north (Tropic of Cancer) and south (Tropic of Capricorn) of the equator will have the Sun at their zenith at noon only on that day of the year (June 21 or December 21 depending upon whether they live at 23.5º north or south).
The ecliptic is inclined to the celestial equator by 23.5 degrees because of the tilt of Earth's axis of rotation. As seen from Earth, the Sun appears to move around the celestial sphere along a circular path called the ecliptic; move along the ecliptic at a rate of about 1 degree per day.
The sidereal year is the orbital period of Earth around the Sun, but it is not the year on which we base our calendar. But most people want annual events to fall on the same date each year. Therefore, to set up a calendar we use the tropical year, which is equal to the time needed for the Sun to return to the vernal equinox. This period is equal to 365.2422 mean solar days. Because of precession, the tropical year is 20 mins and 24 secs shorter than the sidereal year.
Give two reasons why it is warmer in summer than in winter. The sun is high in the midday summer sky, so a shaft of sunlight is concentrated onto a small area, which heats the ground effectively and makes the days warm. Northern hemisphere spends more than 12 hours in sunlight, longer days.
Astronomers now recognize that the celestial sphere is an imaginary object that has no basis in physical reality.
latitude is responsible for the difference in appearance.