Olympiad Test: Stars And The Solar System - 1 - Class 8 MCQ

Pole Star and its Location

 

The pole star, also known as Polaris, is a star that appears very close to the celestial north pole. It is used as a navigational tool and is always visible in the northern hemisphere.

Constellations and the Pole Star

 

 

The pole star is located in the constellation of Ursa Minor. Constellations are groups of stars that form recognizable patterns in the sky. Ursa Minor is a constellation that resembles a small bear and contains the pole star as one of its brightest stars.

Identifying the Correct Answer

 

 

Based on the information provided, we can conclude that the correct answer is:

 

 

• Answer: C. Ursa Minor


 

 

 

Therefore, the pole star is in the constellation of Ursa Minor.

 

The star nearest to the earth is known as the Sun.
Explanation:
The Sun is the star closest to the Earth, located at an average distance of about 93 million miles (150 million kilometers). It is the center of our solar system and provides the Earth with light and heat.
Here are some key points to consider:
- Proxima Centauri: While Proxima Centauri is the closest star to the Sun, it is not the closest star to the Earth. It is located in the Alpha Centauri star system, which is about 4.24 light-years away from us.
- Orion: Orion is not a star but a constellation in the night sky. It contains many stars, including Betelgeuse and Rigel, but none of them are the closest to the Earth.
- Sirius: Sirius, also known as the Dog Star, is one of the brightest stars in the night sky. However, it is not the star nearest to the Earth.
- The Sun: The Sun is a star, and it is the closest one to the Earth. It is a medium-sized star, classified as a G-type main-sequence star. It provides light, heat, and energy to sustain life on Earth.
In conclusion, the star nearest to the Earth is the Sun.

Explanation:
The time taken by a planet to complete one revolution around the sun is called the period of revolution. This is determined by the planet's orbital path and speed. Here's a detailed explanation:
Planet Revolution:
- Planets in our solar system, including Earth, orbit around the sun in elliptical paths.
- The time taken for a planet to complete one revolution is known as its period of revolution.
- This period is measured in Earth days or Earth years, depending on the planet's orbital speed and distance from the sun.
Planet Day:
- The time taken by a planet to complete one rotation on its axis is called a planet day.
- This is the time it takes for a planet to complete one full day and night cycle.
- The duration of a planet day varies from planet to planet. For example, Earth takes about 24 hours to complete one rotation, while other planets have different rotation periods.
Planet Year:
- The time taken by a planet to complete one revolution around the sun is called a planet year.
- This is equivalent to the time it takes for the planet to complete one full orbit around the sun.
- The duration of a planet year varies depending on the distance of the planet from the sun and its orbital speed.
Period of Revolution:
- The term "period of revolution" is commonly used to describe the time taken by a planet to complete one revolution around the sun.
- It is a more general term and can be used for any celestial body that orbits around another object.
- The period of revolution is an important concept in astronomy and is used to study the motion and dynamics of planets and other celestial bodies.
In conclusion, the correct answer is option C: period of revolution, which refers to the time taken by a planet to complete one revolution around the sun.

Explanation:
The correct answer is B: they reflect light from the sun.
Planets do not have their own light source like stars. They appear as bright lights in the night sky because they reflect light from the sun. Here is a detailed explanation:
1. Planets are not self-luminous:
- Unlike stars, which emit their own light through nuclear fusion, planets do not have their own light source.
- Planets are non-luminous objects that rely on external light sources for visibility.
2. Reflection of sunlight:
- Planets are visible to us because they reflect sunlight.
- The Sun is a massive, luminous star that emits a tremendous amount of light in all directions.
- When sunlight reaches a planet, its surface reflects a portion of the light back towards us.
- This reflected light is what makes the planet visible in the night sky.
3. Factors affecting planet visibility:
- The brightness of a planet depends on several factors, including its distance from the Sun, its size, and the composition of its atmosphere.
- Planets closer to the Sun receive more sunlight and appear brighter.
- The size of the planet also plays a role, as larger planets reflect more light.
- The composition of the planet's atmosphere can affect the scattering and reflection of light, further influencing its visibility.
4. Differentiation from stars:
- Stars, on the other hand, emit their own light through nuclear fusion reactions in their cores.
- Stars appear as tiny points of light in the sky, while planets often appear larger and brighter due to their reflected sunlight.
In conclusion, planets appear as bright lights in the night sky because they reflect light from the Sun. Their non-luminous nature and reliance on external light sources distinguish them from stars.

The constellation that resembles a 'question mark' in the sky
Answer: A. Leo
Explanation:
The constellation that resembles a 'question mark' in the sky is Leo.
Reasoning:
Here is a detailed explanation of why Leo is the correct answer:
- Leo is a constellation that is visible in the northern hemisphere during the spring and summer seasons.
- The shape of Leo can be seen as a backward question mark or a sickle, with a bright star called Regulus representing the dot of the question mark.
- The backward question mark shape is formed by the stars that make up the lion's head and mane in the constellation.
- Leo is one of the zodiac constellations and is associated with the astrological sign of the same name.
- Other notable features of Leo include its proximity to the ecliptic, which is the path that the Sun, Moon, and planets appear to travel across the sky, and its inclusion in the Messier catalog as Messier 65, Messier 66, and Messier 95.
In summary:
The constellation that resembles a 'question mark' in the sky is Leo. Its distinctive shape, with a bright star representing the dot, makes it easily recognizable.

To determine the distance of the star Proxima Centauri from the earth, we need to consider the given options and choose the correct one.
A: 4.3 million km
This option represents the distance in kilometers, which is a relatively small unit compared to astronomical distances. Proxima Centauri is much farther away from the earth than 4.3 million km.
B: 8 1/4 light minutes
This option represents the distance in light minutes. However, Proxima Centauri is much farther away from the earth than 8 1/4 light minutes.
C: 3 million light years
This option represents the distance in light years, which is a unit commonly used to measure astronomical distances. However, Proxima Centauri is much closer to the earth than 3 million light years.
D: 4.3 light years
This option represents the distance in light years, which is the correct unit for measuring the distance to Proxima Centauri. A light year is the distance that light travels in one year, and Proxima Centauri is approximately 4.3 light years away from the earth.
Therefore, the correct answer is D: 4.3 light years.

Introduction

In the solar system, the hottest planet is Venus.

Explanation

The temperature of a planet is determined by various factors, such as its proximity to the Sun, its atmosphere, and its greenhouse effect. In the case of Venus, several factors contribute to its extreme heat:

• Proximity to the Sun: Venus is the second planet from the Sun, making it closer to the Sun than Earth. This closer proximity results in higher levels of solar radiation reaching the planet.


• Atmosphere: Venus has a thick atmosphere composed primarily of carbon dioxide, with traces of sulfur dioxide and nitrogen. This dense atmosphere traps heat and creates a strong greenhouse effect, leading to extreme temperatures.


• Runaway Greenhouse Effect: The greenhouse effect on Venus is so intense that it has caused a runaway greenhouse effect, where the heating of the planet's surface leads to the release of more carbon dioxide from its rocks. This further amplifies the greenhouse effect, causing even higher temperatures.

As a result of these factors, Venus has an average surface temperature of about 900 degrees Fahrenheit (475 degrees Celsius), making it the hottest planet in the solar system.

Answer:
The star among the given options is Alpha Centauri.
Here is a detailed explanation:
Explanation:
Definition of a star:
A star is a massive, luminous sphere of plasma held together by gravity. It emits energy, including light and heat, through nuclear fusion reactions occurring at its core.
Identification of the star:
Among the given options:
- Diebos is not a known star.
- Orion is not a star but a constellation in the night sky.
- Phobos is not a star but one of the moons of Mars.
Therefore, the star among the given options is Alpha Centauri.
About Alpha Centauri:
- Alpha Centauri is the closest star system to our solar system.
- It is a triple star system consisting of three stars: Alpha Centauri A, Alpha Centauri B, and Proxima Centauri.
- Alpha Centauri A and Alpha Centauri B are similar to our Sun in size and composition.
- Proxima Centauri is a smaller and cooler star.
Conclusion:
Hence, the correct answer is D: Alpha Centauri.

To determine the correct answer, we need to understand the location of asteroids in our solar system. Here is a detailed explanation:
Asteroids:
- Asteroids are rocky, airless remnants left over from the early formation of our solar system.
- They are primarily found in the asteroid belt, a region of space located between the orbits of Mars and Jupiter.
The Orbits of Planets:
To determine the correct answer, we need to know the orbits of the planets mentioned in each option:
A: Mercury and Venus:
- Mercury is the closest planet to the Sun, and Venus is the second closest.
- The asteroid belt is located beyond the orbits of both Mercury and Venus, so option A is incorrect.
B: Mars and Jupiter:
- Mars is the fourth planet from the Sun, and Jupiter is the fifth.
- The asteroid belt is located between the orbits of Mars and Jupiter, making option B the correct answer.
C: Jupiter and Saturn:
- Jupiter is the fifth planet from the Sun, while Saturn is the sixth.
- The asteroid belt is located before the orbit of Jupiter, so option C is incorrect.
D: Saturn and Uranus:
- Saturn is the sixth planet from the Sun, and Uranus is the seventh.
- The asteroid belt is located before the orbit of Saturn, so option D is also incorrect.
Therefore, the correct answer is option B: Mars and Jupiter.

The stone-like object that appears as a streak of light at night when entering the Earth's atmosphere is called a shooting star.
Explanation:
- Shooting stars, also known as meteors, are small particles of dust or debris from space that enter the Earth's atmosphere.
- As these particles travel through the atmosphere, they experience extreme heating due to the friction with the air molecules.
- The intense heat causes the particles to vaporize and ionize, creating a bright streak of light in the sky.
- These streaks of light are typically seen as a fast-moving, glowing trail that lasts for a few seconds before disappearing.
- Shooting stars are most commonly observed during meteor showers, which occur when the Earth passes through a debris stream left behind by a comet or asteroid.
- The phenomenon of shooting stars is a result of the Earth's gravity attracting and pulling these particles into its atmosphere.
- Despite their name, shooting stars are not stars at all but rather small celestial objects burning up as they enter the Earth's atmosphere.
- Shooting stars can vary in size, with larger ones often producing brighter and more spectacular displays.
- While shooting stars are a common occurrence, they are still a fascinating sight to behold and are often associated with making wishes or fulfilling desires.