Asteroid Belt: Facts & Formation Asteroid Belt: Facts & Formation By Nola Taylor Redd, Space.com Contributor | June 11, 2012 05:51pm ET MORE Orbits of inner planets are shown as large circles in this computer-generated snapshot of actual known objects as of July 20, 2002. Green dots represent asteroids in the main belt between Mars and Jupiter. Red dots are asteroids that stray out of the main belt and pose a small but known possible risk of hitting Earth. Credit: MPC, CBAT, Harvard CfA, IAU Scattered in orbits around the sun are bits and pieces of rock left over from the dawn of the solar system. Most of these objects, called planetoids or asteroids — meaning "star-like" — orbit between Mars and Jupiter in a grouping known as the Main Asteroid Belt. The Main Asteroid Belt lies more than two-and-a-half times as far as Earth does from the sun. It contains billions — maybe even trillions — of asteroids . Most of these are relatively small, from the size of boulders to a few thousand feet in diameter. But some are significantly larger.

Origin Early in the life of the solar system , dust and rock circling the sun were pulled together by gravity into planets. But Jupiter , the largest planet, kept a number of the pieces from coalescing into another planet. Instead, its gravity disrupted the formation process, leaving an array of unattached asteroids. The Main Belt once contained enough material to form a planet nearly four times as large as Earth. Jupiter's gravity not only stopped the creation of such a planet, it also swept most of the material clear, leaving far too little behind for a planet of any size to form. Indeed, if the entire mass of the Main Belt could somehow create a single body, it would weigh in at less than half of the mass of the moon. Other solar systems are thought to contain their own asteroid belts . Asteroids, such as Itokawa, pictured here, are thought to be more like piles of rubble loosely clung together, than solid chunks of rock. Credit: ISAS/JAXA Composition Most of the asteroids in the Main Belt are made of rock and stone, but a small portion of them contain iron and nickel metals. The remaining asteroids are made up of a mix of these, along with carbon-rich materials.

Some of the more distant asteroids tend to contain more ices. Although they aren't large enough to maintain an atmosphere, but there is evidence that some asteroids contain water. Built and managed by The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in NASA's Discovery Program of low-cost, small-scale planetary missions. Credit: NASA/JPL/JHUAPL Some asteroids are large, solid bodies — there are more than 16 in the belt with a diameter greater than 150 miles (240 km). The largest asteroids, Vesta , Pallas and Hygiea, are 250 miles (400 km) long and bigger. The region also contains the dwarf planet Ceres . At 590 miles (950 km) in diameter, or about a quarter of the size of our moon, Ceres is round yet is considered too small to be a full-fledged planet. However, it makes up approximately a third of the mass of the asteroid belt. [Gallery: Asteroid Pictures ] Other asteroids are piles of rubble held together by gravity. Most asteroids aren't quite massive enough to have achieved a spherical shape and instead are irregular, often resembling a lumpy potato.

The asteroid 216 Kleopatra resembles a dog bone. In 2007, NASA launched a mission, Dawn , to visit Ceres and Vesta. Dawn reached Vesta in 2011 and remained there for over a year. It should reach Ceres in 2015. [Related: Asteroid Vesta and NASA's Dawn Spacecraft ] Discovery of the asteroid belt The 18th-century astronomer Johann Titius noted a mathematical pattern in the layout of the planets and used it to predict the existence of one between Mars and Jupiter. Astronomers scoured the heavens in search of this missing body. In 1800, 25 astronomers formed a group known as the Celestial Police, each searching 15 degrees of the zodiac for the missing planet. But the discovery of the first body in this region came from a nonmember, Italian astronomer Giuseppe Piazzi: he named it Ceres . A second body, Pallas, was found a little over a year later. For some time, both of these objects were referred to as planets.

But the discovery rate of these objects increased, and by the beginning of the 19th century, more than 100 had been found. Scientists quickly realized that these were too small to be considered planets, and they began to be known as asteroids. Editor's Recommendations The Main Asteroid Belt - How Asteroid Belts Work | HowStuffWorks How Asteroid Belts Work Prev Next 2008 HowStuffWorks So how do we explain the vast distance between Mars and Jupiter ? Some astronomers have suggested that a separate planet or protoplanet actually formed between the two planets, but the impact of a high-speed comet broke up and scattered the newly formed body to create what we now know as the main asteroid belt. While it's possible that comets and other large objects were flying around the solar system and breaking up material during the early stages, most scientists accept a much simpler theory -- asteroids are leftover matter from the solar system's formation that never successfully came together as one planet. But how come nothing came together? Up Next What's an accretion disk? If you look at Jupiter's mass, you'll notice it's extremely large.

People refer to it as a gas giant for good reason -- while the Earth's mass is about 6x10^24 kilograms, Jupiter's mass is estimated to be 2x10^27 kilograms. It's a much closer relative to our sun than to rocky planets like Earth or Mars. Jupiter's massive size would be enough to disturb the rocky matter that fell in between it and Mars -- its strong gravitational pull would cause any potential protoplanets to collide and break apart into smaller bits. We're then left with a large, spread-out collection of asteroids that orbits around the sun in the same direction as Earth -- the main asteroid belt. With its center around 2.7 AU from the sun, the belt separates Mars and the other rocky planets from the massive, cold gas giants like Jupiter and Saturn. For a closer­ look at asteroids within the belt, see the next page. The Kirkwood Gaps The gravitational force of Jupiter still affects the belt to this day -- its giant mass disturbs the path of asteroids and creates large gaps in the main belt known as Kirkwood gaps. This happens due to orbital resonance, which is the point when one body lines up with the orbit of another body and experiences a force.

For example, an asteroid might make two full orbits around the sun in the time it takes Jupiter to make one orbit. Every other orbit, that asteroid would line up with Jupiter, and its orbit would experience a slight change. This causes several different groups of asteroids to cluster together, depending on how frequently they circle the sun -- it also leaves several gaps where there aren't any asteroids. There are also two "clouds" of asteroids in front of and behind Jupiter's path, known as Jupiter Trojans, which act somewhat like bodyguards around the planet. Two similar groups are found along Mars's orbit called Martian Trojans. SAS Solar System Tour Mars --- Home --- Jupiter About 2-4 AU (186-370 million miles) away from the Sun, between the orbits of Mars and Jupiter, is a region called the Asteroid Belt. This region is a ring of tens of thousands of relatively small rocky objects called Asteroids. Asteroids can vary greatly in size. The smallest are the size of small pebbles, while the largest known asteroid, Ceres, is about 600 miles in diameter.

Even Ceres is small compared to the planets of our solar system: about 500 Ceres-sized objects could fit inside the earth! It's important to understand that even though there are millions of asteroids, they are spread out over a large area. It's not like the asteroid field in Star Wars! If you were on an asteroid in our solar system, it would be very difficult to find another one without a telescope. Why does our solar system have an Asteroid Belt? One theory that astronomers have is that 4.6 billion years ago, when our solar system was being formed, a tenth planet tried to form between Mars and Jupiter. However, Jupiter�s gravitational forces were too strong, so the material was unable to form a planet. Even if a planet had formed, it wouldn�t have been anything to write home about. It is estimated that if you put all the asteroids in the solar system together into one body, they would form an object less than half the size of our moon! Most asteroids in the Asteroid Belt have an orbital period of about 3-6 Earth years. This means that it takes these asteroids 3-6 times longer than Earth to make a trip around the sun. Not all asteroids are in the Asteroid Belt.

Sometimes collisions between asteroids, combined with the gravitational effects of Jupiter, can cause asteroids to leave the belt. If an asteroid comes within 1.3 AU (121 million miles) of the Sun, it is called a Near-Earth Asteroid (NEA). With all these asteroids orbiting around the sun near Earth, it is reasonable to expect that, from time to time, the path of our planet and that of an asteroid will cross. In fact, scientists believe that about 65 million years ago, an asteroid about 6 miles across collided with Earth and caused the extinction of the dinosaurs. More recently, in 1989 an asteroid that was a quarter-mile in diameter came within 400,000 miles of Earth. The asteroid weighed 50 million tons and was traveling at 46,000 miles per hour. Astronomers estimate that the asteroid and the earth passed through the same point in space only six hours apart! Here is a picture of the Near Earth Asteroid Eros, which was the destination of the Near Earth Asteroid Rendezvous (NEAR) spacecraft in 2001. This was the first in-depth study of an asteroid.

It collected data on the mass, structure, geology, and compositon of the asteroid. In addition, the spacecraft captured photographs of the surface of Eros during its descent. Astronomers hope that by learning about the origins of asteroids, they may be able to find some clues about the beginnings of our own planet. The arrow points to the final landing site. This is the last picture that NEAR transmitted. It was taken from 394 feet above the asteroid. The big rock at the top of the picture is 12 feet across. The streaks at the bottom are from the signal being lost when the spacecraft touched down on the asteroid. This is a photograph of the asteroid Ida and its moon Dactyl. That's right: this asteroid has its own moon! Dactyl was first photographed by the Galileo spacecraft when it flew by in 1993. There are two main theories about how Ida got its moon. One is that a large asteroid broke into several small pieces due to a collision with another object and that two of these pieces became gravitationally bound to each other. The other theory is that another asteroid collided with Ida, breaking off a small chunk that became Dactyl.

Either way, astronomers are fairly sure that Dactyl is not a captured moon. Why Isn’t the Asteroid Belt a Planet? - Universe Today Universe Today Why Isn’t the Asteroid Belt a Planet? Article Updated: 23 Dec , 2015 by Fraser Cain Video It seems like there’s a strange gap in between Mars and Jupiter filled with rocky rubble. Why didn’t the asteroid belt form into a planet, like the rest of the Solar System? Beyond the orbit of Mars lies the asteroid belt its a vast collection of rocks and ice, leftover from the formation of the solar system. It starts about 2 AU, ends around 4 AU. Objects in the asteroid belt range from tiny pebbles to Ceres at 950 km across. Star Wars and other sci-fi has it all wrong. The objects here are hundreds of thousand of kilometers apart. There’d be absolutely no danger or tactical advantage to flying your spacecraft through it. To begin with, there actually isn’t that much stuff in the asteroid belt. If you were to take the entire asteroid belt and form it into a single mass, it would only be about 4% of the mass of our Moon.

Assuming a similar density, it would be smaller than Pluto’s moon Charon. There’s a popular idea that perhaps there was a planet between Mars and Jupiter that exploded, or even collided with another planet. What if most of the debris was thrown out of the solar system, and the asteroid belt is what remains? We know this isn’t the case for a few of reasons. First, any explosion or collision wouldn’t be powerful enough to throw material out of the Solar System. So if it were a former planet we’d actually see more debris. Second, if all the asteroid belt bits came from a single planetary body, they would all be chemically similar. The chemical composition of Earth, Mars, Venus, etc are all unique because they formed in different regions of the solar system. Likewise, different asteroids have different chemical compositions, which means they must have formed in different regions of the asteroid belt. Artist’s depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra In fact, when we look at the chemical compositions of different asteroids we see that they can be grouped into different families, with each having a common origin. This gives us a clue as to why a planet didn’t form where the asteroid belt is.

If you arrange all the asteroids in order of their average distance from the Sun, you find they aren’t evenly distributed. Instead you find a bunch, then a gap, then a bunch more, then another gap, and so on. These gaps in the asteroid belt are known as Kirkwood gaps, and they occur at distances where an orbit would be in resonance with the orbit of Jupiter. Jupiter’s gravity is so strong, that it makes asteroid orbits within the Kirkwood gaps unstable. It’s these gaps that prevented a single planetary body from forming in that region. So, because of Jupiter, asteroids formed into families of debris, rather than a single planetary body. What do you think? What’s your favorite object in the asteroid belt. Tell us in the comments below. Podcast (audio): Download (Duration: 3:12 — 2.9MB) The Complete History Of Ceres, The Planet (?) Between Mars And Jupiter The Complete History Of Ceres, The Planet (?) Between Mars And Jupiter Go to permalink Over the last couple of weeks, the Dawn Spacecraft has been beaming back spectacular pictures of Ceres – a world, discovered more than a century before Pluto, about which we know very little.

This is the story of its discovery, and humanity's impending visit to one of the last unexplored planetary bodies in the solar system. Above: Two views of Ceres acquired by NASA's Dawn spacecraft on Feb. 12, 2015, from a distance of about 52,000 miles (83,000 kilometers) | Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA Launched in 2007, the Dawn Spacecraft arrived at minor planet 4 Vesta, the solar system's second-most massive asteroid, in 2011, after which it spent over a year mapping its surface . Now, it's headed for the dwarf planet Ceres. With the second half of its mission coming up, we're poised to learn more than ever about an object that can tell us much about the earliest days of the Solar System. Here's everything you need to know about the history of Ceres, and its imminent exploration The Path To Discovery In the beginning, astronomers knew of other planets in the solar system: Mercury, Venus, Mars, Jupiter, and Saturn.

Over centuries, astronomers have directly observed the major planets and their movements, but with the invention of the telescope in Netherlands in the early 1600s, astronomers had a new tool. Shortly after its invention, Galileo Galilei began to study Jupiter and discovered a series of moons, in and of itself a major advance in our understanding of the astronomy. Study began in earnest on the rest of the solar system, and as we began to learn more about our neighbors, astronomers began to formulate theories on the placement and orbits of the planets. Advertisement Advertisement While the notion of other planets had been commented upon, most predicted new planets to be discovered beyond Saturn, but some, such as Scottish mathematician Colin Maclaurin in the late 1730s, theorized that a body might exist in the gap between Mars and Jupiter.

Based on the observations that he had made up to 1766, Johann Daniel Titius came up with a theory that planets orbited at predictable intervals in the solar system, writing in a translation of Charles Bonnet's Contemplation de la Nature, "Take notice of the distances of the planets from one another, and recognize that almost all are separated from one another in a proportion which matches their bodily magnitudes." It was here which he noted a major gap, one between Mars and Jupiter: "From Mars there follows a space of 4+24=28 such parts, but so far no planet was sighted there. But should the Lord Architect have left that space empty? Not at all. Let us therefore assume that this space without doubt belongs to the still undiscovered satellites of Mars, let us also add that perhaps Jupiter still has around itself some smaller ones which have not been sighted yet by any telescope." Several years later, German astronomer Johann Elert Bode paraphrased Titius's theories in his own work, Anleitung zur Kenntniss des gestirnten Himmels, also noting the gap between Mars and Jupiter.

On March 13, 1781, William Herschel discovered a new planet beyond Saturn: Uranus (which he named George). The new planet also fell exactly where Titius and Bode's rules said it would, lending further credibility to the astronomers. Uranus was also the first discovered using mathematics and telescopic observations. Armed with the confirmation of other planets, the search for new worlds in our home system ramped up throughout the rest of the century, particularly where the rule predicted another planet between Mars and Jupiter. The discovery of a new world there would help to satisfy what was referred to as the Titius-Bode Law. Above: Dwarf planet Ceres photographedby NASA's Dawn spacecraft on February 4, 2015, from a distance of about 90,000 miles (145,000 kilometers) | Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA Celestial Police The law gave direction to a number of astronomers who aspired to enter the history books. One such astronomer was Baron Franz Xavier von Zach of Gotha, Germany, the director of the local Gotha Observatory.

He became the leading figure in the charge to discover the unknown planet. As David A. Weintraub noted in his book Is Pluto A Planet: A Historical Journey through the Solar System, this was a more difficult proposition than it seems: "the Titius-Bode rule provided information only about distance from the Sun, not about celestial longitude or latitude. Thus, since the missing planet could be in any direction in the sky, von Zach was unable to predict in which direction observers should point their telescopes to search for the predicted eighth planet." The search was a figurative needle in a large, dark haystack. Sponsored Von Zach was undeterred, and in 1787, he started looking. Nine years later, and with no planet found, he assembled a number of prominent astronomers for a conference in Gotha to figure out how to go about finding it. Weintraub outlined the historical significance of the gathering: "At this meeting, the French astronomer Joseph Jérôme Lefrançois de Lalande suggested that a large number of observers could, together, conduct a systematic, coordinated search for Bode's planet.

Such a search would have been an unprecedented, international collaboration to do what, in modern terms, we call 'big' science." Von Zach followed up on the idea in September of 1800, assembling a super group of Europe's leading astronomers in Germany: Johann Hieronymus Schröter, Karl Ludwig Harding, Heinrich Wilhelm Matthias Olbers, Freiherr von Ende, and Johann Gildemeister. They called themselves the Celestial Police, and invited an additional eighteen astronomers to aid them in their search. Each one took a 15° by 15° section of the sky, and began to watch for any changes that would indicate a planetary movement. It was slow, observational work: stars would remain in their formations above, while a planet orbiting the Sun would change night to night. For the rest of the year, the international group looked for such a movement. Advertisement Advertisement On January 2nd of 1801, Italian priest, mathematician and astronomer Giuseppe Piazzi (depicted at left)was conducting some usual observations from his observatory in Palermo, Italy when he noticed that one bright point had shifted from its position the night before.

Thinking that he had made a mistake, he looked again on January 3rd, and realized that what he was looking at wasn't a star. Initially, he wasn't sure what he was looking at, outlining his uncertainty in his journal: The light was a little faint, and of the colour of Jupiter, but similar to many others which generally are reckoned of the eighth magnitude. Therefore I had no doubt of its being any other than a fixed star. In the evening of the second I repeated my observations, and having found that it did not correspond either in time or in distance from the zenith with the former observation, I began to entertain some doubts of its accuracy. I conceived afterwards a great suspicion that it might be a new star. The evening of the third, my suspicion was converted into certainty, being assured it was not a fixed star. Nevertheless before I made it known, I waited till the evening of the fourth, when I had the satisfaction to see it had moved at the same rate as on the preceding days. At first, Piazzi thought that he was looking at a comet, and continued to observe the object over the remainder of January and into February.

On January 15th, the Journal de Paris printed the first announcement of the object's discovery: On the 1st of this month, a new comet in the shoulder of Taurus, near the 19th star of Mayer, has been discovered from our observatory. It was observed on the 1st, 2nd, 3rd and 4th, as it passed the meridian. Although it is not covered with any kind of nebulous spot, it still cannot be seen with the naked eye. Its movement is retrograde; it goes forward towards the north. Piazzi also sent letters to Bode and Lalande, both of whom were intrigued by the discovery. Bode noted that "I quickly supposed that this small star without nebulosity odd," and began to run some calculations based on what he had learned. What came back was exciting: the object lay right where his own rule had predicted a planet would exist in the solar system, between Mars and Jupiter. Piazza himself seemed to hold a small amount of hope that what he had discovered wasn't a comet, but "something better": the missing planet.

Based on his observations, however, he wasn't sure and by February 11th, however, it passed out of observational range. Piazza named the object Cerere Ferdinandea, after the Roman goddess of Agriculture, and set about trying to determine the object's orbit so that other astronomers could observe it. Advertisement Word and excitement spread throughout the astronomy community at the prospect of discovering the lost planet. In May, von Zach wrote to fellow Italian astronomer Barnaba Oriani, noting that Bode might have been over-zealous in his pronouncement that the planet had been found, especially on such slim observational data: You, my respectable friend, simply told me that Piazzi himself suspected several times that the comet could just as well be a planet. And Piazzi even had a good reason to suspect it since its motion is very slow and he always saw the star without any nebulosity. You, my good friend, immediately calculated the orbital elements in a circular orbit and thus saw that the planet had its place between Mars and Jupiter. You can easily calculate all this since Piazzi had already told you that he considered his comet a planet.

But how could Bode immediately tell from a handful of numbers, even after a calculation, it was a planet? Credet Judaeus Appella, I do not believe it! Over the course of the summer, it seems as though Piazza's actions frustrated his colleagues: von Zach recounted to Oriani in July his irritation: It is truly unpardonable that this Sicilian has made a secret of his discovery for such a long time. If he had notified the astronomers in time, we would have known what to hold on to, for one would have been able to observe his planet, his star, his comet, his chimera during the entire months of March and April, and we would know at present what it is. All the astronomers found his conduct and secrecy very reprehensible. Both Piazza and von Zach's reactions were understandable: Piazza doesn't seem to have been confident in his abilities, and von Zach was impatient over the nature of the object, and upset over missing out on the observational window. Over the course of the summer, various European astronomers tried and failed to rediscover Ceres.

It wasn't until September that a 24 year old mathematician, Carl Friedrich Gauss was able to calculate the orbit of Ceres and passed along his findings to von Zach: Advertisement Advertisement Your important remarks will be made public four weeks later, which means quite a period of time and is relevant in searching for the heavenly body, but I informed some of my astronomical friends, hunting for the planet carefully, that you extended the examination area further and thus might look farther east. I myself will be following this suggestion and send you daily news if I should be so fortunate to find this wanderer again. Find it he did: in January, after a frustrating search in December, von Zach found Ceres in his telescope, along with fellow Celestial Police astronomer, Olbers. Ceres was indeed there, and more importantly, verified by other scientists. In 1802, Piazza published his findings in Della scoperta del nuovo pianeta Cerere Ferdinandea (The Discovery of the New Planet Ceres Ferdinandea). The discovery was a major find for the astronomy world: another planet discovered after Uranus, and one that fit with the Titius-Bode Law.

While the Celestial Police failed in their mission to discover the new planet, they were successful in other ways: Just a year after Oblers and von Zach helped to confirm the discovery of Ceres, Olbers made another discovery on March 28th, 1802: an object similar to that of Ceres in roughly the same orbital area. He named the object Pallas, and sparked a small debate as to the nature of the newly discovered worlds. They knew that each was far smaller than the other planets due to their relatively low brightness. In 1804, Hardling observed another such world which he named Juno. On March 29th, 1807, Olbers discovered a fourth world: Vesta. Advertisement Most astronomers had begun to refer to these new discoveries as planets for the next several decades, until the discovery of Neptune in 1846, prompting the astronomical community to redefine Ceres, Pallas, Juno, Vesta and the recently discovered Astraea.

(Incidentally, the discovery of Neptune spelled the downfall of the Titius-Bode Law) Their orbits and nature were far different from their larger counterparts, and by 1847, the objects were formally designated Asteroids. The Solar System, which had counted thirteen objects as planets, was re-counted to seven in all. Asteroid 1-Ceres Ceres's demotion from planetary status opened up an entirely new designation for solar system objects: asteroids. From 1847 onward, the discovery of the Asteroid Belt brought up new questions about the formation of the planets: the picture was becoming more and more complicated. Initially, astronomers theorized that the belt was the remains of a planet that had occupied the gap between Mars and Jupiter, one destroyed in a major collision. However, this theory has since been discounted: the amount of energy to break up a planetary mass is enormous, while the entire mass of the asteroid belt thus discovered amounts to less than that of Earth's Moon. Up to half of the mass of the asteroid belt is also contained in Ceres, Vesta, Pallas and Hygiea.

(Ceres contains 30%, Vesta 9%, Pallas 7% and Hygiea 2.9%.) Some of that mass has dissipated: each of the rocky planets have evidence of major impacts, while Jupiter has likely also seen its own impacts. Carl Sagan in Cosmos described the Asteroid Belt as "a great grinding mill, producing smaller and smaller pieces down to motes of dust…[and] may be a place where a planet was once prevented from forming because of the gravitational tides of the giant nearby planet Jupiter." It's likely that the asteroid belt formed early on in the solar system's history. According to Thomas B. McCord and Christophe Sotin in their paper Ceres: Evolution and Current State, due to the "spectral reflectance, the low density and the location of the Solar System, it is thought that Ceres was formed mostly of unaltered carbonaceous chondrite source material with water ice. Evidence from these and other meteorite types suggest that Ceres and other asteroids formed very early in the age of the Solar System, probably within a few up to about 10 million years.

Furthermore, the go on to explain that Ceres is orbiting near where it formed, and that it hasn't changed much since that time. This makes the object a highly desirable object to study, as it could be a time capsule to the earliest days of planetary formation. In all likelihood, Ceres could be a representative example of what early planetary formation might have looked like at the start of the solar system. GIF Above: An animation composed of a series of images acquired by NASA's Dawn spacecraft on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles | Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI One of Ceres' most intriguing features is the water that's present on its surface. McCord and Sotin cite prior papers that the planet's mass could be anywhere from 17% to 25% water, which could date back to the object's formation. Advertisement Advertisement On August 16th, 2006, the International Astronomical Union met after two years of work to create new defining rules for bodies in the solar system.

Amidst the variety of proposals was one that concerned Ceres and the system's furthest recognized planet, Pluto. The new observations of bodies in the solar system challenged the original understanding of planets, and they required a new definition. This proposal defined a planet as "A planet is a celestial body that (a) has sufficient mass for its self- gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet", which would reclassify Ceres as a proper planet, as well as Charon and Eris. However, days later, members proposed and voted on a new definition, Resolution 5A: A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". In the fervor which has followed and persisted, Pluto's status was downgraded from Planet to Dwarf Planet, but at the same time, Ceres was upgraded from Asteroid to Dwarf Planet. Three other bodies, Haumea, Makemake, and Eris were also promoted to Dwarf Planet status, although Charon remains classified as a moon. Exploration Over the course of the 20th Century, astronomers began to study the Asteroid Belt in greater detail, and through their efforts, we began to learn a bit more about it: it composed a dominant part of the belt.

Advertisement The large amounts of water likely present on Ceres made the asteroid a high priority, along with 3-Vesta when NASA began selecting targets for the Dawn mission in 2001. Ceres had been observed by astronomers at a distance, but the first close images that were taken of the asteroid came on July 21st, 1992 from the Hubble Telescope, using the telescope's Faint Object Camera, revealing the circular body. Due to Ceres' unique location and predicted makeup, the planet became a priority for unmanned exploration efforts. As early as 2003, NASA began to plan for a new mission, Dawn, which would be used to explore Ceres. However, the project was cancelled in the winter of 2003, only to be reinstated the following spring. However, due to budget issues at NASA, the Dawn mission was "indefinitely postponed" while "Mission managers had been ordered to halt work on Dawn last fall while the project was assessed by an independent review team,". Following the hold, the probe's builder, Orbital Sciences Corporation offered to build probe 'at cost', and the cancellation was reversed.

Above: This image shows the path Dawn took from Earth, past Mars, to enter orbit around Vesta, and the path it is currently tracing on its way to Ceres | Image Credit: JPL/NASA Dawn was equipped with a unique propulsion system: three NSTAR ion engines and monopropellant reaction control system, which would continuously provide a small amount of thrust. The engine is far less powerful than a conventional rocket engine, but utilizes little fuel, instead relying on continual thrust to gather speed over a longer period of time, allowing the mission to visit two bodies in the Asteroid Belt, rather than one. Advertisement Advertisement While preparations for the mission were underway, the Hubble Space Telescope turned its gaze back to Ceres in June, 2007, capturing a number of higher-resolution images. New features could be discerned from the pictures: bright and dark areas on the dwarf planet's surface, as well as dramatic white spots. After a number of delays, a Delta II 7925H launched Dawn into space on September 27th, 2007, carrying with it two framing cameras, a Visible and Infrared Mapping Spectrometer and a Gamma Ray and Neutron Detector.

By February, 2009, Dawn reached Mars, and used the planet for a gravity-assist maneuver, which sent the spacecraft into the asteroid belt. In July 2011, Dawn arrived at Vesta, where it began its scientific mission: first orbiting from 2,750 kilometers, before dropping down to 680 kilometers in September, and 210 kilometers in December. Dawn returned the first detailed pictures of an asteroid to Earth, and enormous amounts of research material about the body. In May, 2012, NASA released a study that theorized that Vesta was the last remaining major asteroid in the belt, as well as preliminary indications that it might contain water. By September 2012, Dawn completed its mission at Vesta and was turned to its next destination: Ceres. It's departure was delayed with a technical issue, when a reaction wheel malfunctioned.

Departing from the asteroid, it faced another problem as it flew closer to Ceres: On September 11th, 2014, the spacecraft went into safe mode when it was struck by a "high-energy particle of radiation, which disabled an electrical component in the ion propulsion system." The shutdown of the ion engine slowed the spacecraft, and affected some of the probe's onboard systems. [Depicted here: Dawn's ion drive undergoing testing. Credit: JPL/NASA] Advertisement Despite the delays, Dawn caught its first glimpse of Ceres on December 1st 2014, and returned new images throughout January 2015. By January 26th, Dawn's images overtook the resolution of all prior pictures taken by the Hubble Space Telescope, and continue to return new, more detailed images each day it comes closer to the dwarf planet. By March 6th, it's expected to reach its first orbit of Ceres at 13,500 kilometers. After its arrival, Dawn will spend the first fifteen days orbiting Ceres, scanning the drawf planet as it passed underneath: Dawn's leisurely pace compared to the spinning world beneath it presents a very convenient way to map it.

It is almost as if the probe hovers in place, progressing only through a short arc of its orbit as Ceres pirouettes helpfully before it. When Dawn is on the lit side of Ceres over a latitude of about 43 degrees north, it will point its scientific instruments at the unknown, exotic surface. As Ceres completes one full rotation, the robot will fill its data buffers with as much as they can hold, storing images and spectra. By then, most of the northern hemisphere will have presented itself, and Dawn will have traveled to about 34 degrees north latitude. The spacecraft will then aim its main antenna to Earth and beam its prized findings back for all those who long to know more about the mysteries of the solar system. When Dawn is between 3 degrees north and 6 degrees south latitude, it will perform the same routine, acquiring more photos and spectra as Ceres turns to reveal its equatorial regions. To gain a thorough view of the southern latitudes, it will follow the same strategy as it orbits from 34 degrees south to 43 degrees south.

Afterwards, the spacecraft will look for water vapor or signs of water, all while it drops its orbit in April and May 2015 for an even closer look at the dwarf planet's surface. Importance Over the coming weeks and months, we will be treated to new and exciting images of one of the last unexplored major bodies in the solar system. Despite its discovery over two centuries ago, we know very little about the nature of Ceres, and by visiting it and Vesta, the Dawn Spacecraft will explore around 40% of the Asteroid belt's mass. Advertisement Advertisement This is an extremely important mission for planetary scientists: as Ceres and Vesta are believed to be some of the oldest objects in the solar system, and even unique within the solar system, they provide a window into the solar system's past that will help provide answers about the creation and nature of our solar neighborhood. Above: An artist's representation of the probe spiraling in from high altitude to low altitude around Ceres.

The gaps represents those regions of Dawn's orbit where it is not thrusting | Photo Credit: NASA/JPL Dawn has also demonstrated its use to the unmanned exploration field by visiting and orbiting two separate bodies, and returning not only its stunning images, but a wealth of information that will keep researchers busy for years to come. In a point in time when the United States has ceased launching its own manned missions, it's important to recognize that space exploration doesn't necessarily require a manned presence: the last couple of years have seen the unprecedented successes of a number of unmanned systems, from the Kepler Space Telescope (still hanging on despite equipment malfunctions), the Curiosity Rover on Mars, the European Space Agency's Rosetta mission to Comet 67P/Churyumov–Gerasimenko and the upcoming mission to Pluto and Charon by New Horizons. Despite the reduced access of American Astronauts to space, we're living in a golden age of solar system exploration, which will exponentially expand our understanding of the worlds around us. Advertisement 214 years ago, the members of the Celestial Police and astronomer Giuseppe Piazzi helped to start humanity's journey into understanding the solar system.

They invented new methods for using group efforts to discover exciting worlds and features beyond the Earth, and completely changed how we looked at the Earth, our fellow planets and everything in between. Two centuries later, we're continuing that journey in ways they never could have imagined, but in ways which they would likely be just as excited as we are. Gear from Kinja Deals Asteroids – Facts and Information about Asteroids Asteroids: Fun Facts and Information About Asteroids By Charles Q. Choi, Space.com Contributor | November 21, 2014 11:38pm ET MORE OSIRIS clear filter image taken during the flyby of the Rosetta spacecraft at asteroid Lutetia on July 10, 2010. Credit: © ESA 2010 MPS/OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA Asteroids are small, airless rocky worlds revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets. In total, the mass of all the asteroids is less than that of Earth's moon. But despite their size, asteroids can be dangerous.

Many have hit Earth in the past, and more will crash into our planet in the future. That's one reason scientists study asteroids and are eager to learn more about their numbers, orbits and physical characteristics. If an asteroid is headed our way, we want to know that. Most asteroids lie in a vast ring between the orbits of Mars and Jupiter . This main asteroid belt holds more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate the asteroid belt also contains more than 750,000 asteroids larger than three-fifths of a mile (1 km) in diameter and millions of smaller ones. Not everything in the main belt is an asteroid — for instance, comets have recently been discovered there, and Ceres , once thought of only as an asteroid, is now also considered a dwarf planet. Many asteroids lie outside the main belt. For instance, a number of asteroids called Trojans lie along Jupiter's orbital path. Three groups — Atens, Amors, and Apollos — known as near-Earth asteroids orbit in the inner solar system and sometimes cross the path of Mars and Earth.

Formation Asteroids are leftovers from the formation of our solar system about 4.6 billion years ago. Early on, the birth of Jupiter prevented any planetary bodies from forming in the gap between Mars and Jupiter, causing the small objects that were there to collide with each other and fragment into the asteroids seen today. Physical characteristics Asteroids can reach as large as Ceres, which is 940 km (about 583 miles) across. On the other hand, one of the smallest, discovered in 1991 and named 1991 BA, is only about 20 feet (6 meters) across. Nearly all asteroids are irregularly shaped, although a few are nearly spherical, such as Ceres. They are often pitted or cratered — for instance, Vesta has a giant crater some 285 miles (460 km) in diameter. The surfaces of most asteroids are thought to be covered in dust . As asteroids revolve around the sun in elliptical orbits, they rotate, sometimes tumbling quite erratically. More than 150 asteroids are also known to have a small companion moon, with some having two moons.

Binary or double asteroids also exist, in which two asteroids of roughly equal size orbit each other, and triple asteroid systems are known as well. Many asteroids seemingly have been captured by a planet's gravity and become moons — likely candidates include among Mars' moons Phobos and Deimos and most of the distant outer moons of Jupiter, Saturn, Uranus and Neptune. The average temperature of the surface of a typical asteroid is minus 100 degrees F (minus 73 degrees C). Asteroids have stayed mostly unchanged for billions of years — as such, research into them could reveal a great deal about the early solar system. Asteroids come in a variety of shapes and sizes. Some are solid bodies, while others are smaller piles of rubble bound together by gravity. One, which orbits the sun between Neptune and Uranus, comes with its own set of rings . Another has not one but six tails . Classification In addition to classifications of asteroids based on their orbits, most asteroids fall into three classes based on composition. The C-type or carbonaceous are greyish in color and are the most common, including more than 75 percent of known asteroids. They probably consist of clay and stony silicate rocks, and inhabit the main belt's outer regions.

The S-type or silicaceous asteroids are greenish to reddish in color, account for about 17 percent of known asteroids, and dominate the inner asteroid belt. They appear to be made of silicate materials and nickel-iron. The M-type or metallic asteroids are reddish in color, make up most of the rest of the asteroids, and dwell in the middle region of the main belt. They seem to be made up of nickle-iron. There are many other rare types based on composition as well — for instance, V-type asteroids typified by Vesta have a basaltic, volcanic crust. Earth impacts Ever since Earth formed about 4.5 billion years ago, asteroids and comets have routinely slammed into the planet. The most dangerous asteroids are extremely rare, according to NASA. An asteroid capable of global disaster would have to be more than a quarter-mile wide. Researchers have estimated that such an impact would raise enough dust into the atmosphere to effectively create a "nuclear winter," severely disrupting agriculture around the world. Asteroids that large strike Earth only once every 1,000 centuries on average, NASA officials say.

Smaller asteroids that are believed to strike Earth every 1,000 to 10,000 years could destroy a city or cause devastating tsunamis. On Feb. 15, 2013, an asteroid slammed into the atmosphere over the Russian city of Chelyabinsk, creating a shock wave that injured 1,200 people. The space rock is thought to have measured about 65 feet (20 meters) wide when it entered Earth's atmosphere. Dozens of asteroids have been classified as " potentially hazardous " by the scientists who track them. Some of these, whose orbits come close enough to Earth, could potentially be perturbed in the distant future and sent on a collision course with our planet. Scientists point out that if an asteroid is found to be on a collision course with Earth 30 or 40 years down the road, there is time to react. Though the technology would have to be developed, possibilities include exploding the object or diverting it. [ Image Gallery: Potentially Dangerous Asteroids ] For every known asteroid, however, there are many that have not been spotted, and shorter reaction times could prove more threatening.

When an asteroid, or a part of it, crashes into Earth, it's called a meteorite. Here are typical compositions: Iron meteorites Asteroid Belt Facts - Interesting Facts about the Asteroid Belt Asteroid Belt Facts Facts Asteroids What is the asteroid belt? The vast majority of asteroids in the solar system are found in a region of the solar system out beyond Mars. They form the Asteroid Belt. Others orbit in near-Earth space and a few migrate or are thrown out to the outer solar system by gravitational interactions. The four largest asteroids in the belt are Ceres, Vesta, Pallas, and Hygiea. They contain half the mass of the entire belt. The rest of the mass is contained in countless smaller bodies. There was a theory once that if you combined all the asteroids they would make up the missing “Fifth” rocky planet. Planetary scientists estimate that if you could put all that material together that exists there today, it would make a tiny world smaller than Earth’s moon. Where is the asteroid belt located? The Asteroid Belt is located in an area of space between the orbits of Mars and Jupiter. That places it between 2.2 and 3.2 astronomical units (AU) from the Sun.

The belt is about 1 AU thick. The average distance between objects in the Asteroid Belt is quite large. If you could stand on an asteroid and look around, the next one would be too far away to see very well. Various Asteroids – Asteroid Mining The solar system contains many different types of asteroids, grouped by the minerals they contain. The abundances of precious metals such as nickel, iron, and titanium (to name a few), and water make asteroids an attractive target for mining operations when humans decide to expand their presence through interplanetary space. For example, water from asteroids could serve colonies in space, while the minerals and metals would be used to build habitats and grow food for future space colony inhabitants. Beginning 2013, companies interested in asteroid mining began announcing their plans for future operations on distant planetoids. In addition, NASA is looking into similar missions. The biggest obstacles to asteroid mining are the need to develop affordable spaceflight technology that would allow humans to get to the asteroids of interest. Facts about the Asteroid Belt What other fascinating things do we know about the Asteroid Belt? Asteroid Belt objects are made of rock and stone. Some are solid objects, while others are orbiting “rubble piles”.

The Asteroid Belt contains billions and billions of asteroids. Some asteroids in the Belt are quite large, but most range in size down to pebbles. The asteroid 1/Ceres is also designated as a dwarf planet, the largest one in the inner solar system. We know of at least 7,000 asteroids. The Asteroid Belt may contain many objects, but they are spread out over a huge area of space. This has allowed spacecraft to move through this region without hitting anything. Asteroids get their names from suggestions by their discoverers and are also given a number. The formation of Jupiter disrupted the formation of any worlds in the Asteroid Belt region by scattering asteroids away. This caused them to collide and break into smaller pieces. Gravitational influences can move asteroids out of the Belt. The Asteroid Belt is often referred to as the “Main Belt” to distinguish it from other groups of asteroids such as the Lagrangians and Centaurs.

The planet between Mars and Jupiter that you’ve probably never heard of | FOX2now.com The planet between Mars and Jupiter that you’ve probably never heard of Posted 9:43 pm, February 21, 2015, by CNN Wires Email This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated. ATLANTA, GA – Way out beyond Mars, but before you get to Jupiter, is a planet. You read that right. There’s a planet between Mars and Jupiter. You may not have heard of it, but it was discovered in 1801 — 129 years before Pluto. It originally was called a planet, then later an asteroid and now it’s called a dwarf planet. Its name is Ceres (pronounced like series) and you’ll likely be hearing a lot more about it in the coming weeks. Ceres is one of five named dwarf planets recognized by NASA and the International Astronomical Union (IAU). The other four are Eris, Pluto, Makemake and Haumea.

But Ceres is the first of these worlds to get a visitor from Earth: NASA’s Dawn spacecraft is arriving on March 6. “Ceres is a ‘planet’ that you’ve probably never heard of,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. Ceres may be considered a dwarf planet, but it’s “the giant of the main asteroid belt,” Dr. Marc Rayman, chief engineer and mission director of the Dawn mission, told CNN. “It is not only the largest object between Mars and Jupiter, it is the largest object between the sun and Pluto that a spacecraft has not yet visited.” “We are tremendously excited,” Rayman said. “We have guided this robotic probe for well over seven years on an interplanetary journey of more than 3 billion miles. Along the way we sailed past Mars. We spent 14 months orbiting and scrutinizing the giant protoplanet Vesta.

… Now, finally, we are on the verge of conducting the first exploration ever of the first dwarf planet.” New images from Dawn, taken when the probe was about 52,000 miles (83,000 kilometers) from Ceres, show craters and what NASA calls mysterious bright spots. Rayman said its surface is pretty beaten up and that the craters that are “scars from life in the rough and tumble asteroid belt.” Why study a beaten-up space rock? Rayman said because it’s a survivor — and a mysterious one. Made up of rock and ice, Ceres may even have liquid water deep beneath its surface — “perhaps as ponds or lakes or even oceans,” Rayman said. He said Ceres “appears to have been in the process of growing to become a full-sized planet when Jupiter terminated its growth nearly 4.6 billion years ago.” So by studying Ceres, scientists learn more about how the rest of the solar system formed. And he said, we should study Ceres because it’s there — and we need to understand the universe we live in. “We should study it because we hunger for knowledge and understanding. Grand undertakings like this nurture our spirit,” Rayman said.

Rayman said that if you had learned about the solar system 200 years ago, “you would have learned that Ceres was a planet, just as people who learned about the solar system in more recent generations learned that Pluto is.” Speaking of Pluto, the most famous of the dwarf planets gets its own visitor in July. The New Horizons spacecraft is closing in for a flyby of Pluto and its moons. This talk of planets and dwarf planets is still a little confusing, so here’s the most recent tally: NASA currently recognizes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, and the five named dwarf planets we listed earlier. But a sixth possible dwarf planet already is on NASA’s watch list. Called 2012 VP113, it’s believed to be one of the most distant objects in our solar system. On its Solar System Exploration website, NASA says the object was nicknamed “Biden” after Vice President Joseph Biden because of the VP in its initial designation. It will be up to the IAU to decide whether i2012 VP113 is a dwarf planet and whether it gets an official name.

But expect the numbers for planets in our solar system to keep changing. Mike Brown, the CalTech astronomy professor who helped discover dwarf planet Eris and who takes responsibility for killing off Pluto as a full-fledged planet, has his own tally listing more than 360 possible dwarf planets. And NASA has said there may be many more dwarf planets that we haven’t found yet. So Ceres, and its cousins, may soon outnumber the traditional planets you learned about in grade school. Missing asteroids reveal planet-sized mystery - Technology & science - Space - Space.com | NBC News Missing asteroids reveal planet-sized mystery Giant planets would have disturbed many asteroids as they migrated Below: Minor Planet Center/NASA/Johns Hopkins University Applied Physics Laboratory The main belt is between the orbits of Mars and Jupiter, and contains countless asteroids. By Jeremy Hsu + - Missing asteroids in our solar system may be the handiwork of rampaging giant planets as they migrated to their current positions, according to a new computer simulation. Scientists have known that planets such as Jupiter , Saturn, Uranus and Neptune migrated during the first several million years of early existence.

The new simulation showed that the giant planets would have disturbed many asteroids as they fled the scene, leaving behind "footprints" that match the real-life patterns in the main asteroid belt. "It really showed evidence that the footprints of planet migration are visible today in asteroid distribution," said David Minton, a planetary sciences researcher at the University of Arizona in Tucson. Patterns of planet migration Previous evidence has suggested that the giant planets once formed a more compact huddle. But their gravitational interactions with the then-larger Kuiper Belt, an icy region beyond Neptune filled with comet-like bodies , ended up fueling a migration. "Each time the planets tossed these Kuiper Belt objects around, they would move a little," Minton told SPACE.com. Jupiter ended up moving slightly closer to the sun, while the other giant planets moved farther apart from both the sun and each other. Minton and Renu Malhotra, another planetary scientist at the University of Arizona, wanted to examine possible aftereffects of that unstable period. Gaps as evidence They first looked at the current configuration of the main asteroid belt between Mars and Jupiter, which has remained largely stable for 4 billion years.

Astronomers had discovered a series of gaps in the main belt known as Kirkwood gaps back in the 1860s. These unstable regions are relatively empty of asteroids because of Jupiter's and Saturn's current gravitational influence.

Question: The main asteroid belt is between Jupiter and which other planet?
Answer: MARS