Asteroid

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[[File:Asteroidsscale.jpg|thumb|right|165px|This composite image shows the comparative sizes of eight asteroids.]]
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An '''asteroid''' is a small astral body (they are typically composed of ice, metal, and rock) that orbits the [[Sun]] (in our [[Solar System]], that is) too small to have reached hydrostatic equilibrium (read: basically to be more-or-less spherical (i.e., spheroidal) and not an irregularly-shaped flying space rock) and that unlike a [[Comet|comet]] suffers no outgassing that causes it to be enveloped in a cloud called a "coma".{{efn|This is just an outline; to read more on this topic, the other Wiki has an {{wpl|Small Solar System body|article}} waiting for you.}} Sizes range from pretty much whatever you want (car-sized rocks or even less) to [[Ceres]]. Ceres is classified as a ''dwarf planet'' because it's spheroidal but resides in the asteroid belt; it is considered to be around 1,000 kilometers in diameter.

==A bit of history==
One of the biggest, Ceres, was discovered back in the 19<sup>th</sup> century and was at first considered to be a [[planet]]. The same happened with those few that were found in the next decades until the astronomer William Herschel proposed to name them asteroids, as most of them appeared star-like and did not resolve into disks unlike real planets in the telescopes of those years.{{efn|And modern ones too unless you use the Hubble, tricks like adaptive optics, non-telescopic methods such as a radar for those close enough, or better yet, mount your scope onto a spacecraft and chase one down.}} Despite that suggestion, the term "asteroid" and "planet" were used interchangeably until someone noticed what a mess it was to have a Solar System with hundreds of planets, as visual observation was replaced by photography to hunt them and the number of asteroids simply exploded (imagine making a diorama of [https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/in-depth/#:~:text=Main%20Asteroid%20Belt%3A%20The%20majority,and%20millions%20of%20smaller%20ones. 1.9 million asteroids]), and "asteroid" was the term used for them until the IAU changed it a bit in 2006 and placed asteroids, comets, and other, similar objects into the category of "small Solar System bodies".

Nomenclature of these bodies uses a number to indicate its order of discovery plus a name (2 Vesta, for example), and began using female names taken from Greco-Roman mythology following the trend used for Solar System bodies. Once the pool was exhausted, astronomers began to use male names transformed into female ones (as 349 Dembowska), male ones mythological or not (eg: 624 Hektor), names female or not from other mythologies (ie: 2715 Mielikki), and even those from deceased people, fictional characters, etc (25924 [[Douglas Adams|Douglasadams]], 2309 [[Star Trek|Mr. Spock]]…)

==Origin and composition==
It is currently thought that asteroids are remnants of the good ol' days when the Solar System was forming and there were rocks galore flying about. The largest of them (Ceres and {{wpl|4 Vesta|Vesta}}) would have been formed like terrestrial planets. That is, by accretion of smaller celestial bodies, being large enough to differentiate into layers of different compositions (core, mantle, crust),{{efn|These ones are also known as {{wpl|Protoplanet|protoplanets|,}} as most of them would have coalesced, forming the rocky planets.}} while the small ones would be the result of impacts that would have shattered those large enough to have been able to acquire internal structure, with later impacts grinding down the results of those collisions and so on until they became small chunks of rock and bits of dust.

Early theories suggested that the asteroids could have been what remains of a planet located in what's now the asteroid belt (see below) between [[Mars]] and [[Jupiter]], that either went boom by itself of was destroyed by a collision with another large body and entering into [[crank]] and bad science-fiction territory, said {{wpl|Phaeton (hypothetical planet)|planet}} would have become history thanks to stuff that include its inhabitants playing too much with nukes, the planet itself going nuclear, or even the very scary demon-planet [[Nibiru]] paying it a visit. However, the combined mass of all the asteroids is just a small fraction of the [[Moon]]'s mass and more than a half is concentrated on the twelve largest ones, so it's instead considered that Jupiter's gravitational influence prevented them from forming a planet during the Solar System's early times and processes as gravitational interactions of the four largest planets, etc. expelled most of them from the belt, sending significant numbers into the inner Solar System where they'd have {{wpl|Late Heavy Bombardment|gone kamikaze|,}} while the dust produced by asteroid collisions would have ended {{wpl|Poynting–Robertson effect|spiralling into the Sun|.}} It is currently thought that without this interference, Ceres would have eventually absorbed the rest of the asteroids until it ended up as a Mars-sized true planet.{{cn}}

Broadly speaking, asteroids can be classified into "carbonaceous" (with [[carbon]] in addition to rock, thus very dark and assumed to come from the crust of those shredded large ones), "stony" ('nuff said, coming from their rocky mantles), "metallic" (also self-explanatory, remnants from their cores), and those of peculiar composition as Vesta. However nature is far more complex than that and numerous {{wpl|Asteroid spectral type|more detailed}} classifications have been developed.

==Where to find them==
As mentioned above, most asteroids live between the orbits of [[Mars]] and [[Jupiter]] in what's known as the "asteroid belt"{{efn|The bodies of the {{wpl|Kuiper belt}} are not discussed here, as they are too far away and mainly composed of ice, even if there's the possibility of Ceres herself as well as other much smaller bodies of similar composition [http://adsabs.harvard.edu/abs/2008DPS....40.3803M coming from there]}} doing what asteroids do all time: rotating, basking on the faint sunlight of those distances, waiting for the day those [[Human|bipedal apes]] who live on the [[Earth|third big rock from the Sun]] will send a probe to study them, even if it {{wpl|Double Asteroid Redirection Test|happens}} in [[kamikaze]] fashion, and extremely rarely crashing among themselves. And no, spacecraft sent there (or the outer Solar System) do not have to dodge them like Han Solo did in ''[[Fun:Star Wars|The Empire Strikes Back]]''  when he was fleeing all those TIE fighters and Darth Vader's fleet. Although there are millions of asteroids, they're all pretty far from each other, so it's practically empty.{{efn|Scatter one or two handfuls of very fine sand along a few square kilometers and you'll be able to picture (in 2-D) how sparse the belt is}} However, as said crashes and/or gravitational interactions with the ''real'' planets can expel them from their orbits, one can find them in places such as Jupiter's orbit {{wpl|Jupiter trojan|(trojan asteroids)}} or especially in {{wpl|Near-Earth object|orbits close to Earth}} which can be ''very'' nasty as discussed below.

But you don't have to go into space to see them. In fact, you don't even need a telescope. You can spot at the very least the two brightest, Ceres and Vesta, with a pair of binoculars if you know where to look.

==Hazards==
That stray asteroids can pass close to Earth means that sooner or later they ''could'' collide with either the former or the [[Moon]] (they simply do not care), which not only is ''bad'' for them, but can also be ''very'' hazardous for the health of planetary inhabitants, as in causing effects that begin from harmless ones (shooting stars) and scale up to the ''very'' bad luck of one making your day by falling into either your house or [[car]] or, worse, ''you'', the equivalent of a [[nuclear weapon]] detonating in the atmosphere and {{wpl|Chelyabinsk meteor|ruining the day of quite a number of people|,}} and finally causing planetary lifeforms [[Extinction|not having to worry anymore]] about their debts (just ask the non-avian [[Dinosaur|dinosaurs]]). Don't panic, as our technology allows us to detect the largest ones and there are {{wpl|Asteroid impact avoidance|many strategies}} discussed to either send dangerous asteroids elsewhere or destroy them — funding, as usual, is another thing.

==Woo==
Since asteroids (and comets) can ruin our day or worse, some [[woo]]-meisters will either exaggerate claims of space agencies about the probability of a given body deciding to go [[kamikaze]] on Earth, claiming to have information that [[They]] hide, or simply [[PIDOOMA|invent]] them — of course the end-result is always that the asteroid/comet crashes into Earth and kills us/causes the [[NWO]] to rise from the ashes/signals the [[Second Coming]]/whatever. Just look for "asteroid" [[List of predictions of the end of the world|here]] and have fun.

== Non-biblicality ==
Since asteroids don't get a mention in the [[biblical]] [[creation]] narratives of the [[Book of Genesis]], they obviously{{cn | joke}} (try [[Occam's razor]]) pre-existed (like the [[planet]]s other than [[Earth]]) and provided the raw materials for populating the [[firmament | heavens]], for reflecting the newly-created [[light woo#Biblical primacy | light]], for performing other sundry cosmogenetic tasks, and for generally shaking things up whenever required.

==Notes==
{{reflist|group=note|2}}

==External links==
*{{wpa|asteroid}} 
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