Stars And Solar System

As the planet Venus appears in the eastern sky before sunrise or after sunset, therefore, it is known as the morning star or the evening star.

The pole star is commonly known as the North Star. It is located at the northern axis of Earth. Hence, the name North Star.

In option (a), the figure depicts that the star is located above the northern axis, therefore this is the correct answer.

This is because of the phenomenon of relative motion.

The Sun appears to move from east to west from the Earth. Although, we know that Sun remains at rest and only earth rotates, therefore the motion of the Earth with respect to Sun will be opposite to that of the Sun i.e. from west to east.

This is the same case that would have happened if the ball was thrown upwards from the surface of the Earth. The ball would go upwards first and then come back to the surface because of the action of the gravity. In this case, the ball is thrown from the surface of the moon where gravity is less than that on the Earth, but gravity exists and because of its pulling action, the ball will hit the surface of the Moon.

Time period is directly proportional to that of the distance of the planet from the Sun.

As the new planet discovered is in between Uranus and Neptune therefore, the time period of the new planet would be more than as that of Uranus and less than that of Neptune.

The change in seasons is because of the tilt of axis of the Earth. The axis of rotation of the Earth is neither perpendicular nor parallel but tilted and this tilt causes change in the seasons on the Earth. The tilt causes the earth to lean towards or away from Sun as it goes around it.

The new moon means the beginning of the new lunar cycle. It takes thirty days for a moon to complete a cycle that is from new moon to full moon and back to new moon. So, on tbe fifteenth day of the month the moon would be halfway through the lunar phase cycle, and full moon will appear.

No, stars emit their light throughout the day but it is because of the excessive brightness of the Sun during daytime that we are unable to see the light emitted by the stars.

Boojho is correct. Planets do not twinkle. The twinkling of stars is because of the phenomenon of apparent objects. If we observe a small object placed far away from our eyes, it will appear to be twinkling. But planets being bigger in size as they are nearer to our planet as opposed to stars, the twinkling effect does not occur.

(a) False, the given statement is not correct. The planet near to us is not Jupiter. The planets closest to Earth are the Mars and the Venus.

(b)False, the given statement is not correct. All the stars are not at the same distance from us. Different stars are situated at different distances from us.

(c)True, the given statement is correct. The planets do not emit light of their own. Only stars emit light, planets may or may not reflect the light produced by the stars but never emit their own light.

(d)True, the given statement is correct. The planets keep changing their position with respect to stars. All the planets and the stars in this universe are in constant motion so they can never be at a constant position and therefore changes their respective position.

(e)True, the given statement is correct. The planet Venus appears in the eastern sky before sunrise or after sunset. Because of this reason it is also known as the morning star or the evening star.

(f)False, the given statement is incorrect. The plane in which the Earth rotates is called as the orbital plane of the Earth and the equatorial plane is the plane perpendicular to the orbital plane.

A lunar cycle is completed in a month that is the size of the moon from zero to the full moon stage and back to (Since, only a portion of the illuminated moon is visible to us, it appears to be of half size or crescent). John saw a full moon on a particular day then he will be able to see another full moon after approximately 29 days. This is because the size of the full moon will reduce to zero i.e. new moon stage after 15 days and from 16th day onwards new lunar cycle will begin with the waning crescent moon stage and on the 29th day the full moon will once again reappear.

The pole star is always situated at the northern end of the axis of rotation of the Earth. So the given diagram represents the position of the pole star for the above given diagram.

The Sun will be at position C. It can be identified as the side of the Earth near to the position C is illuminated i.e. has day and the phenomena day and night on the Earth occurs according to the direction of Sun. The side of the Earth which faces the Sun will be illuminated and the other portion will remain dark, therefore night will be observed. So using this concept we can identify the position of the Sun.

The diagram given below shows the position of the Sun located at (C).

Day and night on the Earth occurs according to the direction of the Sun. The side of the Earth facing the Sun will have day and the other half will remain dark, hence night. By using this concept we can say that the Sun is situated at the right side and the direction of the rays of the Sun is falling from right to left.

The given diagram shows the rays of the Sun.

Light year is the unit of measurement of distance. 1 light year is equal to the distance travelled by light in one year. So if a star is located ten light years away from the Earth which brightens up today then it will be visible to our eyes after ten years.

The entry of any celestial body in the Earth's atmosphere is known as a meteor. They are also referred to as the shooting star as it glows upon entering the atmosphere due to friction, leaving a streak of light behind. Although, during the daytime the Sun is brighter than the light produced by the meteors due to heating, which is why meteors are not visible during daytime.

Moon is visible to us because of the light produced by the Sun. As the moon revolves around the Earth, only a portion of moon is illuminated by the Sun, consequently only the illuminated portion of the moon is visible. Therefore, it seems like the shape of the moon changes every day.

The Earth keeps rotating on its axis and revolving around the Sun. The same way moon also revolves around the Earth. So, Paheli will not be able to locate the moon at the same positioned marked on the glass because during the period of 8 p.m. till 4 a.m. the moon must have travelled certain distance around the Earth.

Moon is visible to us because the surface of moon reflects the light from the Sun.

If moon starts to emit its own light then it will always glow and be visible like Sun. In that case there would be no phases or change in shape but always a full moon in the night sky.

A heavenly body consisting mainly of ice, dust and gas revolving in an orbit and when it comes near the Sun, a tail produced of dust and gas can be observed pointing away from the Sun. Comets are sometimes also referred to as "dirty snowballs".

The tail of the comets are visible only when it passes through the inner orbit of solar system and 'B' being the closest point from the Sun, will have the longest tail.

The moon do not emit light of its own instead reflects the light coming from the Sun. As the moon rotates on its orbital axis with the same rate with which it revolves around the Earth, we are only able to see one side of the moon always.

(a) Different phases of the moon are observed because of reflection of the Sun. The part of the moon reflecting the Sun's light become visible and hence we can observe different conditions like crescent moon, full moon, new moon etc.

In the given figure the full moon condition in the evening will be observed in the eastern part of the sky. (Assuming North upwards).

(b) When only a small arc-shaped section of the moon is illuminated by the Sun then that stage is known as crescent moon stage. In this case the moon is sickle shaped, that is, broad in the middle but tapering at the edges.

In the given figure, the crescent moon condition in the evening will be observed in the western part of the sky (Assuming North upwards).

There are many planets revolving around the Sun in their own orbits. Our Earth is also one of those planets which sustain life. The names of all the existing planets in order of their distance from the Sun are as follows:

•Mercury

•Venus

•Earth

•Mars

•Jupiter

•Saturn

•Uranus

•Neptune

Even when Earth is present at a sufficient distance from the Sun, the temperature on the surface of the Earth is too high. If the distance between the Sun and the Earth becomes half of the existing distance then the temperature on the Earth would be enormous for us to bear. It would even destroy the vegetation on the Earth. The water may dry up too soon. Seeing these conditions we can definitely say that if the distance between the Earth and the Sun is halved then there would be no life on the Earth.

The great bear also known as the Ursa Major is a constellation present in the northern sky. To find the pole star from the Ursa Major, locate the two end stars of Ursa Major. Draw an imaginary straight line passing through these stars as shown in the figure below. Extend this imaginary line towards the north direction. This line will lead to a star which is not too bright. This is pole star.