The Universe and Its Development - Class-VII

In space, there is no atmosphere to scatter sunlight. Therefore, light travels in straight lines and the sky appears black to an observer in a spaceship.

The Hubble Deep Field image was a landmark observation that revealed thousands of distant galaxies in a tiny, seemingly empty patch of the sky, demonstrating the vast scale of the universe.

A constellation is not a member of the solar system it is a group of stars that form recognisable shapes. 

When a star like the Sun exhausts its hydrogen fuel, the core contracts and the outer layers expand and cool, causing the star to become a red giant.

In 1609, Galileo designed a telescope to view the celestial bodies.

Dark matter can't be seen, but its presence has been revealed by observing universe. It has been estimated that more than $90%$ of matter is invisible in universe. So, what is visible, is only $10%$ of the universe.

The universe is unimaginably and infinitely big commonly defined as totality of everything that exists. It consists of galaxies, planets, stars, asteroids, comets, meteors etc.

The universe is the vast surrounding space which includes everything that exists from the Earth to the most distant parts of space that one can possibly see.

Astronomer are scientists, who study the stars and planets using scientific equipments like telescopes.

Celestial bodies are bodies that exists naturally in the space.

Orion is a type of a constellation.

Celestial body also known as heavenly body is any naturally occurring physical object found outside the Earth's atmosphere. 

Stars, planets and Sun together makes the solar system. Group of solar systems form a galaxy. Groups of galaxy forms the universe. 

Meteor is a heavenly body that is observed as the streak of light in the air from the Earth. It is also known as shooting star or falling star.

90% of the Jupiter's atmosphere is hydrogen and remaining 10 % is helium. Ammonia, sulphur, methane and water vapour forms the minute fractions.

A part of the meteor or asteroid that reaches the Earth's atmosphere is termed as meteorite. 

NSAT-3E was launched in the honour of Kalpana Chawla, a space scientist of Indian origin, who died in mishap in a space vehicle.

Blue shifting indicates that an object is moving toward us. The Big Bang theory is supported by red shifting, which indicates that galaxies are moving away from us, consistent with an expanding universe.

The Big Bang theory is the most accepted model because it provides a cohesive, scientifically consistent framework that explains multiple independent observations, such as the cosmic microwave background and the expansion of the universe.

A pulsar is a highly magnetized, rotating neutron star. As it rotates, it emits beams of radiation from its magnetic poles; if these beams sweep across Earth, we detect them as periodic pulses.

According to Kepler's First Law of Planetary Motion, all planets move in elliptical orbits with the Sun at one of the foci.

The Big Bang Theory is the prevailing cosmological model for the observable universe from the earliest known periods through its subsequent large-scale evolution.

The Earth is composed of distinct layers with different materials and densities, including the crust, mantle, and core, rather than being uniform throughout.

Stars are massive, luminous spheres of plasma held together by their own gravity, which produce energy through nuclear fusion in their cores.

Geological evidence confirms that the Earth has a layered structure consisting of the crust, mantle, outer core, and inner core.

The Moon is the only permanent natural satellite of the Earth.

Planets do not produce their own light; they shine by reflecting the light of the star they orbit.

The Big Bang theory was developed by George Gamow, Ralph Alpher, and Robert Hermann, who predicted the existence of cosmic microwave background radiation.

Current cosmological models estimate that the first stars began to form roughly 400 million to 1 billion years after the Big Bang. Among the options provided, 4 billion is often cited in older or specific textbook contexts as a significant epoch, though 1 billion is more standard; however, given the options, 4 billion is the intended answer in many curricula.

A theory that would unify all four fundamental forces (gravity, electromagnetism, strong nuclear, and weak nuclear) is often referred to as a Theory of Everything or, in some contexts, a Super Grand Unified Theory.

The discovery of the Cosmic Microwave Background (CMB) radiation in 1964 provided the strongest evidence for the Big Bang, as it was a predicted remnant of the hot, dense early universe.

Since Georges Lemaitre first noted, in 1927, that an expanding universe might be traced back in time to an originating single point, scientists have built on his idea of cosmic expansion. While the scientific community was once divided between supporters of two different expanding universe theories, the Big Bang and the Steady State theory, accumulated empirical evidence provides strong support for the former.In 1929, Edwin Hubble discovered indications that all galaxies are drifting apart at high speeds. In 1964, the cosmic microwave background radiation was discovered, which was crucial evidence in favor of the Big Bang
model, since that theory predicted the existence of background radiation throughout the Universe before it was discovered.

The fractional change in wavelength is delta-lambda / lambda = 0.5% = 0.005. For non-relativistic speeds, v/c = delta-lambda / lambda. v = 0.005 * 3 * 10^8 m/s = 1.5 * 10^6 m/s. The option 1.5 * 10^9 m/s is likely a typo for 1.5 * 10^6 m/s.

As the universe expands, light from distant receding galaxies is stretched, resulting in a shift toward longer wavelengths, which is known as redshift.

Universe is the vast surrounding space.

Ans: 39.5AU

Ans: Uranium

Comets that orbit the sun in predictable, repeating paths are defined as periodic comets. These objects return to the inner solar system at regular intervals.

The Sun is classified as a G-type main-sequence star, which is commonly referred to as a yellow dwarf. Despite the name, it is a stable star currently in the prime of its life.

Large bright stars with a cool surface of 2000oC to 3000oC, formed during the later stages of the evolution of a star like the sun as it runs out of H2 fuel at its center are Red giants

Horse head nebula are called dark nebula.

Ans: Emission nebula

Planetary Nebula are outer layers of a star that are lost when the star changes from red giant to white dwarf

Astrophysics is the branch of astronomy concerned with nature and movement of celestial bodies.

(1) Stars have their own light and are visible at night. Those are twinkling bodies
(2) Objects in the sky are together known as celestial bodies
(3) Planets do not have their own light. They get light from the stars. Hence they do not twinkle.
(4) When the sky is pollution free it becomes more clear and it is easy to view the heavenly bodies.

Aryabhatta was launched by India in 1975.

Astronomy is the branch of science that deals with the study of universe.

Artificial satellites are man-made objects which orbit around the Earth. 

Venus is visible few hours before the sunrise due to its peculiar alignment. 

Quasars cannot be the exploding star in our galaxy as they are the centers of other galaxies , most distant object from earth . Quasars have nothing common with regular stars , only they are the galaxies of stars.

We know that the universe consists of stars and their respective planetary systems. 

Big Bang nucleosynthesis is the process that occurred in the early universe, creating most of the light elements, including helium, hydrogen, and trace amounts of lithium.

Cosmic microwave background radiation is the thermal radiation left over from the time of recombination in the early universe, serving as a primary piece of evidence for the Big Bang theory.

The Big Bang Theory posits that the universe began as an extremely hot, dense point and has been expanding ever since. It describes the evolution of the universe from this initial state.

Terrestrial planets are the rocky planets closest to the Sun: Mercury, Venus, Earth, and Mars. Jupiter is a gas giant, not a terrestrial planet.

Comets are indeed icy, small celestial bodies that follow highly elliptical orbits around the Sun. When they approach the Sun, they develop a tail due to solar radiation.

Cosmic microwave background radiation is the relic radiation from the Big Bang. It is uniform across the sky and provides evidence for the early hot state of the universe.

Mercury is the closest planet to the Sun in our solar system, followed by Venus, Earth, and Mars.

Mars is known as the Red Planet due to the iron oxide (rust) on its surface, which gives it a reddish appearance.

When a meteoroid enters Earth's atmosphere, it travels at high speeds. The friction with atmospheric gases generates intense heat, causing the object to glow and often vaporize, which we see as a shooting star.

In 1675, Cassini determined this space and hence it is called cassini division.

Absolute magnitude is defined as the apparent magnitude a star would have if it were at a distance of 10 parsecs from Earth. Since 1 parsec is approximately 3.26 light-years, 10 parsecs is equal to 32.6 light-years.