Unit 2 Comets and Meteors Flashcards
What is a comet?
A comet is a ball of rock and ice that have tow tails.
What are the two tails of a comet?
The ion tail (points away from the Sun) and the dust tail (points in the direction the comet has travelled from).
What are the two categories of comet?
Short period comets (orbital period of less than 200 years and originate from the Kuiper Belt) and long period comets (originate from the Oort Cloud).
Name a famous short period comet.
Eg: Comet Halley.
Is there evidence for the Oort Cloud?
There is no direct evidence but there is very strong evidence that suggests its existence.
What is the Coma of a comet?
The coma is the heated gas and dust that forms around the comet’s nucleus as it approaches the Sun.
What is a meteoroid?
Meteoroids are small rocky irregular sized lumps of rock that can range in size from micrometres to several metres. Some may have some iron-nickel content.
What does the Royal Astronomical Society propose is the difference between a meteoroid and a small asteroid?
It must be over 10 metres in size to be an asteroid.
Give some examples of the origins of a meteoroid.
Broken fragments of colliding asteroids.
Impacts with planets.
Some originate from dust tails of comets forming groups called meteoroid streams.
What is a meteor?
A meteor is a meteoroid that has entered the Earth’s atmosphere and produces a short streak of light as it burns up due to friction.
What is a fireball?
A meteor with a magnitude of -3 or brighter.
What is a meteorite?
A piece of meteor that survives the descent to Earth and lands on the Earth’s surface.
What are the 3 classifications of meteorites?
Stones, irons and stoney-irons. It depends upon the ratio of rock to metal.
What is a meteor shower?
When the Earth passes through the meteoroid stream in the wake of a comet, the debris enters the Earth’s atmosphere and a meteor shower is the burning up of the dust in the atmosphere.
What is the radiant?
The apparent point in the sky that the meteors diverge from during a meteor shower.
How are meteor showers named?
By the constellation in which the radiant appears in. Eg: Perseids shower lies in Perseus.
What is a PHO?
It is a Potentially Hazardous Object.
What is a NEO?
It is a Near Earth Object whose trajectory might bring them within 0.3 AU. In 2008 about 5600 NEOs were known.
How close is a PHO?
Less than 0.05 AU. In 2008 about 1000 had been identified.
Examples of collisions in the Solar System.
The Moon and other planets have craters.
Venus and Uranus rotate on their axis “backwards” and “sideways” respectively; both are thought to be consequences of gigantic collisions early in the Solar System.
Rock samples of the Moon show that it may be the result of a collision with the Earth.
Chicxulub Crater in Mexico.
Barringer Crater Arizona.
True or false, most PHOs have a high chance of inflicting damage on Earth.
False, most PHOs have little chance of inflicting damage. It is PHOs with a diameter greater than 1 km that pose a threat on a global scale.
What is the Torino Scale?
It is the scale that is used to categorise the risk posed by a PHO. 0 to 1 is a near miss whilst 10 is a certain impact that could be capable of world-wide devastation.
