The universe is filled with fascinating information. Do you know that the Earth-Sun distance is shorter than the Earth-Mars distance? Or that Venus takes longer time to spin on its axis than to orbit the Sun (A day on Venus is longer than a year!). Have you heard about the Escape Velocity, Orbital Velocity and Astronomical Unit. I shall explain about it in this blog.
Celestial bodies include planets, moons, stars, comets,
, asteroids, meteors, meteorites, and galaxies. The Solar System comprises the Sun, its eight planets, moons, comets, asteroids, and meteoroids.
Moons in the Solar System
There are 220 known moons in the Solar System. Here’s the breakdown:
- Mercury & Venus: 0 moons
- Earth: 1 moon
- Mars: 2 moons (Phobos, Deimos)
- Jupiter: 95 moons (including Io, Europa, Ganymede, Callisto)
- Saturn: 146 moons (includes Titan, Enceladus)
- Uranus: 27 moons (e.g., Titania, Oberon, Miranda)
- Neptune: 14 moons (includes Triton)
Largest Moons
Earth\\\'s Moon is relatively large at 3,474 km in diameter, but some moons are larger:
Ancient and Modern Discoveries
Ancient cultures revered Earth’s Moon for its phases and its role in calendars and mythology. The moons of other planets, however, were only discovered after telescopes were invented. Galileo discovered Jupiter’s four largest moons in 1610, and Titan was found by Christiaan Huygens in 1655.
Pluto’s Reclassification
Once the ninth planet, Pluto was reclassified as a dwarf planet in 2006 because it does not have a clear orbit. Other dwarf planets include Eris, Ceres, Haumea, and Makemake.
Comets and Shooting Stars
Comets like Halley’s Comet have fascinated humanity for millennia. Halley’s 76-year orbit brings it close to the Sun before it retreats to the Kuiper Belt, losing mass with each pass. Shooting stars, or meteors, were once seen as bad omens but are now understood as meteoroids burning up in Earth’s atmosphere.
Escape velocity, is the velocity by which a comet escape from the gravitational force of star. It is high when the comet is close to the star(Sun) but low when it is away from the star. Astronomical unit (AU) is defined as the distance between Earth and Sun. Pluto is over 35 AU from sun, which means Earth is very close to the Sun.
Planetary Orbital Speeds
Planetary orbital speeds decrease with distance from the Sun:
- Mercury: 47.87 km/s
- Earth: 29.78 km/s
- Jupiter: 13.07 km/s
Neptune: 5.43 km/s
Distant planets travel slower due to weaker gravitational pull and longer orbital paths.
Dark matter and dark energy make up approximately 95% of the universe. Only 5% is normal matter, we can see. The universe is expanding due to the effect of dark energy,therefore we cannot exactly tell its dimensions. Dark matter is thought to be holding galaxies together. In every galaxy, there is a supermassive black hole. There are billions of rogue planets, rejected by stars float in interstellar space,
Saturn’s largest moon, Titan, is larger than Mercury, with a diameter of 5,149 km, making it 50% larger than Earth’s Moon! (The moon)
Dr.C.J.GEORGE FRCS
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