Question 1

A constellation is best described as:

Accepted Answer

A recognizable pattern of stars as seen from Earth, whose stars may actually lie at very different distances. Stars in a constellation only appear grouped because they lie along nearly the same direction from Earth. In reality they can be at hugely different distances and are usually not related to one another.

Question 2

The constellation Ursa Major (the Big Dipper, or Saptarishi) is often used by observers to locate which important star?

Accepted Answer

Polaris, the Pole Star. The two stars at the outer edge of the Big Dipper bowl are the pointer stars. A line drawn through them points almost directly to Polaris, the Pole Star, which sits above the northern horizon.

Question 3

According to Kepler, the planets travel around the Sun in orbits that are:

Accepted Answer

Ellipses with the Sun at one focus. Kepler's first law states that each planet moves in an ellipse with the Sun located at one of the two foci, not at the centre. Circular orbits are only an approximation.

Question 4

Which of the following is a NATURAL satellite?

Accepted Answer

The Moon. The Moon orbits Earth without being built or launched by humans, making it a natural satellite. The others are artificial satellites placed in orbit by people.

Question 5

A geostationary satellite seems to hover permanently above one fixed spot on Earth because:

Accepted Answer

Its orbital period equals Earth s rotation period of about 24 hours and it orbits above the equator. A geostationary satellite circles Earth once per day in the same direction as Earth s spin, and directly over the equator. Since it keeps pace with the ground below, it appears fixed in the sky.

Question 6

Stars are born inside vast clouds of gas and dust in space. Such a cloud is called a:

Accepted Answer

Nebula. A nebula is a cloud of gas (mostly hydrogen) and dust. Under gravity, dense regions of a nebula collapse and heat up until nuclear fusion begins, giving birth to a new star.

Question 7

A refracting telescope forms images of distant objects mainly using:

Accepted Answer

Lenses. A refracting telescope uses lenses to bend (refract) and focus light. A reflecting telescope, by contrast, uses curved mirrors to gather and focus the light.

Question 8

The Pole Star (Dhruva Tara) appears almost stationary in the sky because it lies:

Accepted Answer

nearly above the axis of rotation of the Earth. The Pole Star is nearly in line with the Earth's rotational axis, so it barely appears to move.

Question 9

The two "pointer stars" of Ursa Major are useful because they:

Accepted Answer

point towards the Pole Star. A line through the two end stars of the Big Dipper points to the Pole Star, aiding navigation.

Question 10

The stars that make up a constellation are:

Accepted Answer

usually at very different distances and not physically close to one another. Stars in a constellation merely appear together from Earth; they are actually at widely different distances.

Question 11

The asteroid belt of the solar system lies mainly between the orbits of:

Accepted Answer

Mars and Jupiter. The main asteroid belt is located between Mars and Jupiter.

Question 12

A planet closer to the Sun completes one revolution in a shorter time than a distant planet. Therefore, the planet with the shortest year is:

Accepted Answer

Mercury. Being closest, Mercury moves fastest and has the shortest orbital period (year).

Question 13

A geostationary satellite appears to stay fixed above one point on the Earth because its orbital period is:

Accepted Answer

about 24 hours (equal to the Earth's rotation period). A geostationary satellite orbits once every ~24 hours over the equator, matching the Earth's spin, so it appears stationary.

Question 14

A satellite remains in its orbit around the Earth because:

Accepted Answer

the gravitational pull of the Earth provides the required centripetal force. Earth's gravity supplies the centripetal force that keeps the satellite moving in its circular/elliptical orbit.

Question 15

Stars, including the Sun, produce their enormous energy by:

Accepted Answer

nuclear fusion of hydrogen into helium. In the core, hydrogen nuclei fuse into helium, releasing vast energy (nuclear fusion).

Question 16

A medium-sized star like the Sun will, near the end of its life, first swell into a:

Accepted Answer

red giant. A Sun-like star expands into a red giant, then sheds its outer layers to leave a white dwarf.

Question 17

A very massive star ends its life in a huge explosion called a:

Accepted Answer

supernova. Massive stars explode as supernovae, leaving behind a neutron star or a black hole.

Question 18

A refracting telescope forms images using ______, while a reflecting telescope uses ______:

Accepted Answer

lenses; mirrors. Refractors use lenses to bend light; reflectors use curved mirrors to gather and focus it.

Question 19

A telescope with a larger objective (aperture) is better because it:

Accepted Answer

collects more light and can show fainter objects. A bigger aperture gathers more light, allowing fainter and more distant objects to be seen.

Question 20

Every star, including those forming a constellation, drifts slowly across space (proper motion). What does this imply about constellation shapes over very long times?

Accepted Answer

They slowly change shape over tens of thousands of years as the stars shift relative to one another. Proper motions are tiny over a human lifetime, so patterns look fixed to us. But over tens of thousands of years the different individual motions accumulate and the familiar shapes gradually distort.

Observing Space / Astronomy — Homi Bhabha Class 9 Physics MCQs with Solutions

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