Chapter 11: Meteors, Asteroids, Comets and Pluto
Published 3 years ago
Published 3 years ago
- Survey orbitals and pp, of small bodies in the solar system, meteor, meteors and meteorites
- Asteroids minor planets
- Dwarf planets plutoids
- Meteoroids and Meteors
- Meteoroids are objects orbiting the Sun that are too small to observe.
- Sizes are from about 1 m down to less than 1 mm.
- Speeds are >= 10 km/s and faster, much faster than a bullet.
- When they hit Earth the friction with our atmosphere heats and vaporizes them, creating a meteor “shooting star” alerting us to their existence.
- If a meteoroid is large enough to reach the ground without being completely vaporized before it hits the ground.
- Meteorites can be collected and taken into a lab for analysis.
Types of Meteorites
- One type of meteorite is made of silicate compounds “stony” meteorites.
- Some, called “chondrites”, contain small grains indicating they have not been heated very strongly before hitting Earth.
- Some are even more “primitive” and contain matter rich in carbon, indicating they have had almost no heating. Some even contain amino acids that are important to life.
- Some stony meteorites have no chondrules, so they are named “achondrites” which indicated that they have been heated strongly enough to melt the chondrules.
- These probably come from larger objects that got hot enough to melt the rock, and were broken apart by a collision.
- Another type of meteorite is made of iron “irony” meteorites.
- These probably also came from the broken up large objects.
- The iron in these meteorites has avery distinctive crystalline pattern that forms when the iron cools from molten to solid over millions of years.
- The final type of meteorite is a mixture of irony and stony.
- These probably also came from the broken up large objects, but are from the boundary between stone and iron.
- Studying meteorites shows us what can happen inside larger objects, maybe even inside the Earth and other planets.
- Aster (star) oid (body) a rocky body orbiting the Sun that is so small that it looks like a star.
- Another name for these is “minor planets”.
- Discovered by observing that they shift their positions compared to the stars.
- Before photography, they were really hard to find.
Where are Asteroids Located?
- Most asteroids are located in the region between Mars and Jupiter = “asteroid belt”
- A small number of asteroids are located in the orbit of Jupiter, 60 degrees ahead of and 60 degrees behind Jupiter Trojan asteroids.
- The Trojan asteroids orbit with Jupiter because of the combined gravity of the Sun and Jupiter.
- The NEOs have probably had a gravitational interactions with Jupiter.
- In the asteroid belt, Jupiter’s gravity creates gaps.
Are Asteroids Important?
- Yes, because:
- They are samples of the material that built the planets.
- They can collide with planets, even Earth.
- Their impact energy is so great that it can cause tremendous damage even mass extinction of life on Earth such as happened 65 million years ago.
- Such impacts can/will happen again.
- Comets are also small bodies orbiting the Sun in very long, thin orbits.
- They are mostly ice with a mixture of frozen gasses and rocky dust.
- When they come into the inner solar system the sunlight causes the ice to turn to gas, freeing the other gasses and dust to produce a gas tail and a dust tail.
Where do Comets “Live”?
- Because comets have very elliptical orbits, they spend most of their time far from the Sun where their ice doesn’t vaporize.
- One location is called the “Kuiper belt”, which is beyond the orbit of Neptune.
- Their other main location is called the “Oort cloud” at the edge of the solar system.
- Recall (Ch 10) that Neptune was found because it altered the orbit of Uranus.
- Astronomers thought (incorrectly) that Neptune’s orbit was also being altered and this led to a search that just so happened to discover Pluto in 1930. Pluto was discovered by luck.
- Pluto is so far away (39.48 AU from the Sun) and so faint it couldn’t be studied.
- In 1978, it was discovered that Pluto has a moon that has been named Charon.
- Charon made it possible to:
- Measure Pluto’s mass 0.0021 MEarth.
- Measure Pluto’s radius 0.181 REarth.
- Without that moon, we would not know this.
- Surveys have discovered other small bodies beyond Neptune that have physical properties and orbits similar to Pluto.
- They all orbit far beyond Neptune.
- They have very elliptical orbits.
- Orbits tilted to the orbits of the major planets.
- Dwarf planets are a new family of objects in the solar system.
- They probably formed closer to the Sun where the solar nebula was denser.