Space Objects
“We live in the middle of a shooting gallery with thousands of asteroids in our path that we haven’t even discovered yet.
Carl Sagan Item 5.45 on the Intro page
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Halley's Comet on 8 March 1986 source
If a meteoroid is more than 10 metres in diameter, it is classified as
an asteroid.
Space Object Differences
When learning about space it can sometimes be difficult to know the difference between all the amazing objects out there.
The following terms are often confused with each other so let’s answer the question:
What’s the difference between a comet, an asteroid, a meteoroid, a meteor and a meteorite?
Although there can sometimes be a blurry line between categories the following definitions should help you understand the difference between comets and asteroids.
Why Halley’s Comet is not a meteorite. etc.
Comet
Comets are relatively small solar system bodies that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail.
The coma is created as the comet gets closer to the Sun, causing water, carbon dioxide and other compounds to sublime (quickly changing from solid to gas) from its surface.
Comets are made of ice, dust and small rocky particles.
The name comet comes from the Greek word meaning ‘hair of the head’, it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair’.
Short term comets (also known as periodic comets) have orbital periods of less than 200 years while long term comets have longer orbital periods.
Asteroid
Asteroids are small solar system bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds which may have brought first life to Earth. Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do.
Asteroids are similar to comets but do not have a visible coma (fuzzy outline and tail) like comets do.
Asteroids are also known as planetoids or minor planets.
Asteroids vary greatly in size, some feature diameters as small as ten metres while others stretch out over hundreds of kilometres. Note that objects under ten metres in diameter are generally regarded as meteoroids.
The first asteroid was discovered in 1801 by Italian astronomer Giuseppe Piazzi. Named Ceres, it features a diameter of around 950 kilometres and is now regarded as a dwarf planet. Ceres was given dwarf planet status in 2006, along with Pluto, Eris, Makemake and Haumea.
The asteroid belt lies roughly between the orbits of Mars and Jupiter in the Solar System. It is home to a large amount of irregular shaped asteroids that range in size from dust through to the dwarf planet Ceres.
"A ‘potentially hazardous’ monster asteroid the size of Hyde Park is heading towards Earth." source
Chandrika said:
Asteroids are a class of small Solar System bodies in orbit around the Sun.
These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System.
When discovered, their volatile-based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids.
Thus the term asteroid has come increasingly to refer specifically to the small rocky and metallic bodies of the inner Solar System out to the orbit of Jupiter.
Meteoroid
A meteoroid is a small rock or particle of debris in our solar system.
They range in size from dust to around 10 metres in diameter (larger objects are usually referred to as asteroids). more
A small percentage of meteoroids fly on a path that goes into the Earth’s atmosphere and then back out again, they are known as Earth grazing fireballs.
A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor.
If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor.
The fastest meteoroids travel through the solar system at a speed of around 42 kilometres per second (26 miles per second). (Light travels at 186000 miles a second more.)
Note that objects under ten metres in diameter are generally regarded as meteoroids.
Meteor
A meteoroid that burns up as it passes through the Earth’s atmosphere is known as a meteor.
If you’ve ever looked up at the sky at night and seen a streak of light or ‘shooting star’ what you are actually seeing is a meteor.
When many meteors occur in a close time frame in the same part of the sky it is called a meteor shower.
The Earth’s atmosphere experiences millions of meteors every day. They are easier to see during the lower light conditions of night.
Meteorite
A meteoroid that survives falling through the Earth’s atmosphere and colliding with the Earth’s surface is known as a meteorite.
Around 500 meteorites reach the Earth’s surface every year but of those only around 5 ever make it to scientists for study. more
The blast caused by the shock waves of a Russian meteorite was picked up by infrasound sensors on the other side of the world.