Universe and Solar System PDF, Structure of Universe, Sun and all the planets of Solar System | Geography Notes PDF in English
The Universe
- Universe includes everything: space, time, matter, energy.- Space is framework, not limited to space alone.
- Universe's fabric: space-time, 4D entity linking space and time.
Age of Universe
- Universe's age found by modern astronomy.
- Age: around 13.7 billion years.
- Universe not infinitely old.
- Age: around 13.7 billion years.
- Universe not infinitely old.
Size of Universe
- Universe size unknown, maybe infinite.- Scientifically unconfirmed, but intriguing concept.
Cosmic Horizon
- Cosmic horizon: farthest we can view, approx. 13.7 billion light years away
- Observable universe = within cosmic horizon.
Structure of Universe
- The shape of space determines the structure of the universe, which is surprisingly curved on a very large scale.- Mathematically, space has a three-dimensional "saddle shape" with negative curvature that spans millions or even billions of light-years
Sun and Solar System
- Sun = star, 109x Earth's diameter, 3.30 lakh x Earth's mass, 99.9% Solar System mass.- Mostly Hydrogen & Helium
- Formed 4.6 billion years ago.
- Future: Hydrogen depletion in 5-6 billion years, becomes red giant.
Structure of the Sun
- Sun's layers:
- Core at center
- Radioactive zone around core
- Convective zone around radiative zone
- Thin photosphere on surface
- Chromosphere and corona beyond photosphere.
Composition of the Sun
- Sun's mass:- 71% hydrogen
- 27% helium
- 2% other elements
- Atom count:
- 91% hydrogen
- 9% helium
- < 0.1% other elements
- Most stars have similar composition.
Big Bang Theory
- Start of universe is as a single point of space-time.- Expanding since then
- Changes:
- Small to big
- Hot to cold
- Young to old
- Developed via Einstein's General Theory of Relativity.
- BY Willem de Sitter, 1977.
Planets
- A planet is a celestial object that orbits around a star and is mostly spherical in shape due to its own gravitational pull.- Currently, there are eight planets in our solar system, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, and several dwarf planets, including Pluto, Charon, Ceres, Eris, etc.
Inner Planets/Terrestrial Planets
The four planets that are part of the inner solar system, namely Mercury, Venus, Earth, and Mars, are called terrestrial planets because they share similar structures, including a metallic core surrounded by a rocky mantle and thin crust.Outer Planets/Gas Giants
Jupiter, Saturn, Uranus, and Neptune are called gas giants because they are much larger than terrestrial planets and have atmospheres that are dominated by gas.They are located in the outer part of the solar system, roughly between the orbits of Jupiter and Pluto, and have numerous moons and rings.
Mercury
- Closest to Sun, 58 million km away.- Orbit elongated due to proximity. (i.e. closeness to sun)
- Orbit time: 88 Earth days.
- Rotation time: 59 Earth days.
- Surface:
- Caloris Basin: ancient crater, huge pit
- Observation challenge: Glare from Sun.
- NASA's Messenger probe:
- Confirmed ice at north pole.
- Insights into composition.
Venus
- Like Earth in size, composition.- Closest to Earth.
- Shorter year, longer day.
- One day on venus is 243 days. (day = time for which sun is up)
NOTE - how long it takes a planet to orbit around its star, is called a year.
- Thick atmosphere:
- Almost 100x denser than Earth's.
- Mostly carbon dioxide.
- Unfit for life:
- No terrestrial life due to atmosphere.
- Poisonous sulphur dioxide in clouds.
- Surface temp = 500°C.
- Telescopic observation:
- Venus phases visible (like Moon).
- Almost 100x denser than Earth's.
- Mostly carbon dioxide.
- Unfit for life:
- No terrestrial life due to atmosphere.
- Poisonous sulphur dioxide in clouds.
- Surface temp = 500°C.
- Telescopic observation:
- Venus phases visible (like Moon).
Mars
- Mars, known as the red planet due to its rusty appearance, has fascinating geologic features on its surface, including mountains, craters, channels, canyons, highlands, lowlands, and even polar ice caps.- Its year is longer than Earth's, but a day on Mars is similar in length.
- Its atmosphere is also much thinner than Earth's, with only about 7000th the density.
Jupiter
- Jupiter is the largest planet in the solar system and rotates faster than any other planet, with a day that lasts only 9 hours and 56 minutes.- Its mass is 1,300 times that of Earth, and it has over 60 known moons, with four of them being similar in size to Earth's Moon or larger.
Saturn
- Saturn is similar to Jupiter, but smaller, with a day that is just over 10 hours long.
- It has a solid core made of rock and ice, covered by a layer of liquid metallic hydrogen and layers of liquid hydrogen and helium.
- These layers conduct strong electric currents that generate Saturn's powerful magnetic field.
- It has a solid core made of rock and ice, covered by a layer of liquid metallic hydrogen and layers of liquid hydrogen and helium.
- These layers conduct strong electric currents that generate Saturn's powerful magnetic field.
Uranus
- Uranus is the seventh planet in our solar system and the third of the four gas giants.- It has a pale blue-green, cloudy atmosphere made mostly of hydrogen and helium, with small amounts of methane and other gases.
- Its color is due to the methane in the atmosphere, which absorbs reddish light and reflects bluish-greenish light.
- Its core is thought to be surrounded by a slushy mixture of ice, ammonia, and methane.
Neptune
- Neptune is the eighth planet in our solar system and the most remote of the gas giants.- It takes 165 Earth years to orbit the Sun once, but a day on Neptune is only 16 Earth hours long.
- Its cloud-top temperature is a frosty -210°C, and it's bluish-green in color, fitting for a planet named after the Roman god of the sea.