UNIVERSE

• The Universe includes everything that exists, from large Galactic Mega clusters to small subatomic particles.
• Scientists believe the Universe is approximately 13.79 billion years old.
• The Universe is comprised of a number of galaxies.
• Studies show that there are about 100 billion galaxies in the visible universe.
• The Big Bang Theory is widely accepted as the origin of the Universe.
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Birth and Death of a Star

• Star starts as Nebula which are clouds of dust and gas.
• Nebula contracts to form a denser region known as ProtoStar.
• ProtoStar becomes a star through nuclear fusion.
• When a star uses all of its Hydrogen, its helium starts fusing into carbon. At a stage helium’s fusion and energy production inside the star stops. As a result, stars core contracts under its own weight to a very high density to make a white Dwarf star.
• White Dwarf star becomes Black Dwarf star on cooling
• White Dwarf star is a dead star and shines by radiating stored heat
• Giant star becomes Red Supergiant, explodes as Supernova or changes into Neutron/Black Hole
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Planets

• Planets are called “wanderers”
• 8 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
• Planets move around the sun in fixed, elliptical orbits
• 5 recognized dwarf planets: Ceres, Pluto, Haumea, Makemake, and Sedan
• Planets grouped into two categories:
  • Terrestrial planets: Earth-like, dense and rocky bodies (Mercury, Venus, Earth, Mars) called inner planets
  • Jovian planets: Outer, gaseous, gigantic planets with large satellites (Jupiter, Saturn, Uranus, Neptune) called Jupiter-like planets

Mercury

• Mercury is the smallest planet in the solar system
• It is closest to the sun, at a distance of 58 million km or 0.39 AU
• A day on Mercury takes 59 Earth days
• Mercury is a rocky planet and is also known as a terrestrial planet
• Its thin atmosphere is mostly composed of oxygen, sodium, hydrogen, helium, and potassium
• Only two missions have visited Mercury: Mariner 10 in 1974-75 and MESSENGER in 2011
• Daytime temperatures can reach 430°C and drop to -180°C at night.

Venus

• Venus is slightly smaller than the Earth.
• It is the second closest planet to the sun at a distance of about 108 million km.
• A day on Venus lasts 243 Earth days.
• Venus is a rocky, terrestrial planet with a volcanic landscape.
• Its thick atmosphere is mostly made up of carbon dioxide and nitrogen, with clouds of sulfuric acid.
• Over 40 spacecraft have explored Venus, and 98% of its surface has been mapped by the Magnellian mission in the 1990s.
• The temperature on Venus is almost 480° Celsius, making it unlikely for life as we know it.
• Venus spins backward compared to other planets, meaning the sun rises in the west and sets in the east. It is known as retrograde rotation.

Earth

• Earth is the third planet from the sun and is located 93 million miles away (1 Astronomical Unit).
• A day on Earth takes 24 hours to complete.
• It’s atmosphere is composed of 78% nitrogen, 21% oxygen, and 1% other ingredients, making it suitable for life.
• Earth has one moon.
• It is a unique planet with a breathable atmosphere and perfect conditions for life.
• Earth’s atmosphere protects it from meteoroids, most of which break up before reaching the surface.

Mars

• Mars is the fourth planet from the sun, at a distance of about 228 million km (142 million miles) or 1.52 AU.
• A day on Mars takes just over 24 hours.
• Mars is a rocky, terrestrial planet with a solid surface altered by various geological processes.
• Mars has a thin atmosphere mostly composed of carbon dioxide (CO2), nitrogen (N2), and argon (Ar).
• Mars has two moons: Phobos and Deimos.
• Several missions have visited Mars, starting with Mariner 4 in 1965. Current missions are exploring Mars’ past and future potential for life.
• Mars is called the “Red Planet” because iron minerals in its soil oxidize, or rust, causing the soil and atmosphere to look red.
• Prelims fact:
  • Jezero Crater is a 45 km wide crater located north of the Martian equator. 
  • It is located on the edge of Isidis Planitia, a flat plain. While the crater itself was created by the impact of meteorites, the flat plain was formed by the impact of an ancient asteroid in an event called Isidis event. 
  • The crater shows evidences of an ancient river system and it even has remnants of a delta. 
  • It is the landing site of NASA’s Perseverance mission
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Jupiter

• Jupiter is the fifth planet from the sun and is much larger than Earth.
• It is located about 778 million km (484 million miles) or 5.2 AU from the sun.
• One day on Jupiter takes about 10 hours.
• Jupiter is a gas-giant planet and therefore doesn’t have a solid surface.
• Its atmosphere is mostly made up of hydrogen (H2) and helium (He).
• Jupiter has 67 known moons, including 50 confirmed and 17 unconfirmed.
• It has a faint ring system and is one of the four giant planets in our solar system with ring systems.
• Many missions have visited Jupiter and its moons, including the Juno mission which arrived in 2016.
• Jupiter itself cannot support life, but some of its moons may have oceans that could support life.

Saturn

• Saturn is the 6th planet from the sun and is 9.5 Astronomical Units (AU) away from the sun.
• One day on Saturn takes 10.7 hours (the time it takes for Saturn to rotate or spin once).
• Saturn is a gas-giant planet and doesn’t have a solid surface.
• Atmosphere of Saturn is mostly made up of hydrogen (H2) and helium (He).
• Saturn has 53 known moons and 9 additional moons pending confirmation of their discovery, for a total of 62 moons.
• Saturn has the most spectacular ring system with 7 rings and gaps and divisions between them.
• Only a few missions have visited Saturn, including Pioneer 11, Voyager 1 and 2, and Cassini-Huygens. Cassini has been exploring Saturn and its system since 2004.
• Galileo Galilei first noticed Saturn’s rings in the 1600s and thought they were “arms” or “handles.”

Uranus

• Uranus is the seventh planet from the sun at a distance of about 2.9 billion km (1.8 billion miles) or 19.19 AU.
• One day on Uranus takes about 17 hours.
• Uranus is an ice giant and most of its mass is made up of a hot dense fluid of water, methane, and ammonia.
• Uranus has an atmosphere mostly made up of hydrogen and helium, with a small amount of methane.
• Uranus has 27 moons named after characters from the works of Shakespeare and Alexander Pope.
• Uranus has 13 known rings, with the inner rings narrow and dark and the outer rings brightly colored.
• Voyager 2 is the only spacecraft to have visited Uranus.
• Uranus cannot support life as we know it.
• Uranus is the only planet which rotates on its side, spinning horizontally.

Neptune

• Neptune is the 8th planet from the sun and is located about 4.5 billion km (2.8 billion miles) away or 30.07 AU.
• One day on Neptune takes 16 hours to complete a rotation.
• Neptune is an ice giant, similar to Uranus.
• Neptune’s atmosphere is mostly made up of hydrogen (H2), helium (He), and methane (CH4).
• Neptune has 13 moons, named after sea gods and nymphs in Greek mythology.
• Neptune has 6 rings.
• Voyager 2 is the only spacecraft to have visited Neptune.
• Neptune cannot support life as we know it.

Kármán Line

• The Kármán line is the boundary between Earth’s atmosphere and outer space.
• It is 100 km (62 miles) high.
• The Kármán line helps define legal and regulatory measures for aircraft and spacecraft.
• Aircraft and spacecraft fall under different jurisdictions and treaties.
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