Astronomy for Kids
Dwarf planets, asteroids, and comets
Published in Creation 44(3):34–37, 2022
The most massive object in our solar system is the sun. By far—it has 99.85% of the total mass. Most of the rest of the mass—0.135%—is the eight planets. Jupiter has by far the most—over 2½ times the mass of the other seven planets combined. But what of the remaining 0.015%? Most of that is the moons around the planets. But the remaining relatively small objects are still interesting.
Dwarf planets
The most famous dwarf planet is 134340 Pluto, or just Pluto. The American astronomer Clyde Tombaugh (1906–1997) discovered it in 1930. He showed that it orbited the sun—once every 248 Earth years. Astronomers declared this the 9th planet of our solar system. It was named by the 11-year-old English schoolgirl Venetia Burney (1918–2009). She chose the name of the Roman god of the underworld (Greek: Hades).
However, in 2006, the International Astronomical Union (IAU) ruled that Pluto was not a planet but a dwarf planet. Pluto is much smaller than the planets; in fact, it’s a fifth of the mass of our moon. There are also other objects of similar size, such as Eris, Haumea, Makemake, Gonggong, Quaoar, and Sedna. Eris is actually 27% more massive than Pluto. So the choice was to name all these objects as planets or demote Pluto to a dwarf planet like them.
In 2015, NASA’s New Horizons space probe flew by Pluto. Evolutionists believe that Pluto is 4.5 billion years old, so they thought it should be ‘cold and dead’. However, New Horizons found that the surface was still active. There was fresh ice with few craters and cliffs and chasms. This means that it must be much younger than evolutionists say. The Bible says that God created the heavenly bodies on Day 4 of Creation Week, about 6,000 years ago.
Pluto has five moons. The biggest by far is Charon, about half the diameter of Pluto.
Asteroids
For centuries, astronomers wondered why there was a big gap between Mars and Jupiter. Why was there no planet? But an object was found in this gap in 1801. The discoverer was Giuseppe Piazzi (1746–1826), a Catholic priest and chair of astronomy at the University of Palermo, Sicily. But this object was so tiny that it appeared point-like, just like the stars (hence the name asteroid, meaning star-like). But it moved like a planet. Piazzi named it Ceres, after the Roman goddess of agriculture. It is only 939.4 km (583.7 mi) in diameter (7% of Earth) and has only 1.3% of the mass of our moon. Soon, other objects in that area were discovered.
By the 1850s, there were so many asteroids discovered that astronomers spoke of an ‘asteroid belt’. Astronomers have now counted over 1.1 million asteroids in this belt. Ceres is by far the largest, now classified as a dwarf planet. The next three largest are Vesta (525.4 km average diameter), Pallas (512 km), and Hygiea (434 km). These four contain 50% of the total mass of the asteroid belt. But the total mass is only 4% of our moon’s.
NASA’s Dawn space probe went to Vesta in 2011, then to Ceres in 2012. The probe’s fuel ran out in 2018, but it’s still orbiting Ceres.
Activity
Draw some planets and asteroids to scale. E.g. choose a scale of 1 cm (10 mm) to 1000 km, or 1:100 million. So draw Ceres 9½ mm in diameter, the moon 3½ cm, and Earth 12.7 cm.
But forget about drawing the Earth’s orbit around the sun. It is 300 million km diameter, so you would need a page 300 km (200 miles) wide! Or, if we used a scale of 1 cm to 10 million km (1:1 trillion), the orbit would be 30 cm (1 foot) wide, and would fit on a large sheet. But the planets would be microscopic. So the solar system—including the asteroid belt—is mostly empty space.
Comets
Comets have fascinated people for thousands of years. They apparently appear out of nowhere, then disappear just as mysteriously. In between, their long tails look far more prominent than anything else in the night sky. Ancients thought they looked like hairy stars—the word ‘comet’ comes from the Greek for ‘long haired’.
However, the comets are really ‘dirty snowballs’, containing dust and ice. They are only a few km in diameter and travel on extremely elliptical orbits around the sun. The most famous comet, Halley’s Comet, is 15 km long, 8 km wide, and 8 km thick, and orbits the sun once every 76 years. Comets shine only when they get close to the sun and part of the ice evaporates. The vapour and dust each form a tail always pointing away from the sun, pushed by the solar wind. The tails reflect sunlight to create the spectacular sight. But while bright, they are extremely thin. Earth passed through the tail of Halley’s Comet in 1910, and it was hardly noticeable.
There are over 4,500 known comets. Some space probes have flown past comets. On 12 November 2014, the European probe Rosetta sent a lander Philae to the surface of Comet Churyumov–Gerasimenko.
Comets are a big problem for evolutionists. Every time we see them, part of them evaporates. If they had been orbiting for more than a few thousand years, they would have disappeared. So they could not have been orbiting for billions of years.
Evolutionists propose that something must be supplying new comets to replace those that evaporated. One source is supposed to be the Kuiper Belt. But the objects in it are far too large and too few. Another is the Oort Cloud, but that has never been detected.
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