How Many Planets are in the Solar System? - Universe Today Universe Today How Many Planets are in the Solar System? Article Updated: 16 Oct , 2016 I’m just going to warn you, this is a controversial topic. Some people get pretty grumpy when you ask: how many planets are in the Solar System? Is it eight, ten, or more? I promise you this, though, we’re never going back to nine planets… ever. When many of us grew up, there were nine planets in the Solar System. It was like a fixed point in our brains. As kids, memorizing this list was an early right of passage of nerd pride: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. But then in 2005, Mike Brown discovered Eris, an icy object thought to be about the same size as Pluto, out beyond its orbit. That would bring the total number of planets to ten. Right? There’s no turning back, textbooks would need to be changed. In order to settle the dispute, the International Astronomical Union met in 2006, and argued for, and against Pluto’s planethood.

Some astronomers advocated widening the number of planets to twelve, including Pluto, its moon Charon, the Asteroid Ceres, and the newly discovered Eris. In the end, they changed the definition of what makes a planet, and sadly, Pluto doesn’t make the cut: Here are the new requirements of planethood status: A planet has to orbit the Sun. Okay fine, Pluto does that. A planet needs enough gravity to pull itself into a sphere. Okay, spherical. Pluto’s fine there too. A planet needs to have cleared out its orbit of other objects. Uh oh, Pluto hasn’t done that. For example, planet Earth accounts for a million times the rest of the material in its orbit, while Pluto is just a fraction of the icy objects in its realm. The final decision was to demote Pluto from planet to dwarf planet. But don’t despair, Pluto is in good company. Ceres. Image credit: NASA There’s Ceres, the first asteroid ever discovered, and the smallest of the dwarf planets. The surface of Ceres is made of ice and rock, and it might even have a liquid ocean under its surface. NASA’s Dawn mission is flying there right now to give us close up pictures for the first time.

Haumea, named after the Hawaiian goddess of fertility, is about a third the mass of Pluto, and has just enough gravity to pull itself into an ellipsoid, or egg shape. Even though it’s smaller, it’s got moons of its own. Makemake. Credit: NASA Makemake, a much larger Kuiper belt object, has a diameter about two-thirds the size of Pluto. It was discovered in 2005 by Mike Brown and his team. So far, Makemake doesn’t seem to have any moons. Eris is the most massive known dwarf planet, and the one that helped turn our definition of a planet upside-down. It’s 27% more massive than Pluto and the ninth most massive body that orbits the Sun. It even has a moon: Dysnomia. Pluto. Credit: ESO And of course, Pluto. The founding member of the dwarf family. Want an easy way to remember the eight planets, in order? Just remember this mnemonic: my very excellent mother just served us noodles. For all you currently writing angry tweets to Mike Brown , hold on a sec. Changing Pluto’s categorization is an important step that really needed to happen.

The more we discover about our Universe, the more we realize just how strange and wonderful it is. When Pluto was discovered 80 years ago, we never could have expected the variety of objects in the Solar System. Categorizing Pluto as a dwarf planet helps us better describe our celestial home. So, our Solar System now has eight planets, and five dwarf planets. Podcast (audio): Download (Duration: 3:35 — 3.3MB) July 18, 2008 at 8:57 PM There are 12 planets in the solar system–Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, MakeMake, and Eris. It’s not the International Astronomical Union but four percent of that group that voted on excluding Pluto in a sloppy, nonsensical definition that states a dwarf planet is not a planet at all. The requirement that an object clear its orbit to be considered a planet is vague and if applied literally, could exclude all the planets because none has fully cleared its orbital field of nearby asteroids, and Neptune has not cleared its orbit of Pluto.

Most of the 424 IAU members who voted on this are not planetary scientists. No absentee voting was allowed. Also, many planetary scientists are not members of the IAU and therefore had no say in this matter. Interestingly, almost as many astronomers as those who voted at the IAU General Assembly in 2006 signed a petition saying they will not use the new definition, and a better one is needed. The lead scientist rejecting the IAU decision is Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission and one of the foremost experts in the world on Pluto and the Kuiper Belt. An object orbiting the sun with enough self-gravity to pull itself into a round shape (a condition known as hydrostatic equilibrim) is a planet. With this definition, we keep the term planet as broad as possible while allowing for multiple subcategories such as terrestrial planet, gas giant, ice giant, dwarf planet, hot Jupiters, super Earths, etc. There is no problem with defining a dwarf planet as an object that does not dominate the neighborhood of its orbit. The problem comes in stating that a dwarf planet is not a subtype of planet.

This is where the IAU decision falls short and needs to be revised. This matter will be further discussed in August 2008 at the Great Planet Debate in Laurel, Maryland. More information on this conference, which is open to the public, is available at It is a disservice to readers to portray the planet question as a done deal as opposed to an ongoing debate. I urge you to present both sides of this debate as opposed to choosing one view and presenting it as a foregone conclusion. patience September 4, 2008 at 7:32 AM The explanation based on the nine planet:but i suggest that there was jst nine planet in the solar system.how come the eight now in the solar system.joining the three dwarf planet that is the ceres,eris,and the makemake plus the pluto which is not part of the planet agin making twelve planet in the solar system.can u pls give more explanation based on that.send any information to my email box provided below. M.

Afzal for me its easy if it orbits the sun and it is in are planetary system making it a planet just because its past the Kuiper belt or in it and small does not make it less of a planet so for me Pluto Haumea, Makemake, and Eris. Ceres are planets Dmitri Yatsenko January 12, 2009 at 5:02 PM Laurel Kornfeld I couldn’t agree more. However, what you are calling a planet is actually termed a ‘planemo’, meaning PLANEtary Mass Object. This includes perfect planets AND dwarf planets, as well as moons the size of planets and even interstellar ‘planets’. Pluto, Eris, Haumea, and other dwarf planets, including Ceres, are planemos. You are right; the ‘clearing the neighboorhood’ thing is ABSURD, and I refuse to use the IAU definition of a planet, I will use my own definition (see my second latest comment on ‘why is pluto not a planet/universe today). And I do not agree that a dwarf planet is not a planet even though it is called a dwarf PLANET!

Since both planets and dwarf planets are planemos, then they are. Dwarf planets are not between planets and planetoids, they are closer to planets! However, I do believe that perfect planets and dwarf planets are different things. But, as I said, they are two of several subclasses of planemos. And also, I will just add one thing to your definition of planet/planemo: it needs to be massive enough and typically big enough to get into the planetary span (which, however, needs to be defined roughly). All bodies fullfilling this condition would be in hydrostatic equilibrium. Also, I disagree with you that it is OK to define dwarf planet by whether it has cleared its orbit. Didn’t you mention yourself that it is stupid to determine a planet by that criteria (or, rather, the opposite of it)? caca head January 28, 2009 at 7:37 PM Laurel Kornfeld I couldn’t agree more. However, what you are calling a planet is actually termed a ‘planemo’, meaning PLANEtary Mass Object. This includes perfect planets AND dwarf planets, as well as moons the size of planets and even interstellar ‘planets’.

Pluto, Eris, Haumea, and other dwarf planets, including Ceres, are planemos. You are right; the ‘clearing the neighboorhood’ thing is ABSURD, and I refuse to use the IAU definition of a planet, I will use my own definition (see my second latest comment on ‘why is pluto not a planet/universe today). And I do not agree that a dwarf planet is not a planet even though it is called a dwarf PLANET! Since both planets and dwarf planets are planemos, then they are. Dwarf planets are not between planets and planetoids, they are closer to planets! However, I do believe that perfect planets and dwarf planets are different things. But, as I said, they are two of several subclasses of planemos. And also, I will just add one thing to your definition of planet/planemo: it needs to be massive enough and typically big enough to get into the planetary span (which, however, needs to be defined roughly). All bodies fullfilling this condition would be in hydrostatic equilibrium. Also, I disagree with you that it is OK to define dwarf planet by whether it has cleared its orbit.

Didn’t you mention yourself that it is stupid to determine a planet by that criteria (or, rather, the opposite of it)? caca head January 28, 2009 at 7:38 PM Laurel Kornfeld I couldn’t agree more. However, what you are calling a planet is actually termed a ‘planemo’, meaning PLANEtary Mass Object. This includes perfect planets AND dwarf planets, as well as moons the size of planets and even interstellar ‘planets’. Pluto, Eris, Haumea, and other dwarf planets, including Ceres, are planemos. You are right; the ‘clearing the neighboorhood’ thing is ABSURD, and I refuse to use the IAU definition of a planet, I will use my own definition (see my second latest comment on ‘why is pluto not a planet/universe today). And I do not agree that a dwarf planet is not a planet even though it is called a dwarf PLANET! Since both planets and dwarf planets are planemos, then they are. Dwarf planets are not between planets and planetoids, they are closer to planets! However, I do believe that perfect planets and dwarf planets are different things.

But, as I said, they are two of several subclasses of planemos. And also, I will just add one thing to your definition of planet/planemo: it needs to be massive enough and typically big enough to get into the planetary span (which, however, needs to be defined roughly). All bodies fullfilling this condition would be in hydrostatic equilibrium. Also, I disagree with you that it is OK to define dwarf planet by whether it has cleared its orbit. Didn’t you mention yourself that it is stupid to determine a planet by that criteria (or, rather, the opposite of it)?Laurel Kornfeld I couldn’t agree more. However, what you are calling a planet is actually termed a ‘planemo’, meaning PLANEtary Mass Object. This includes perfect planets AND dwarf planets, as well as moons the size of planets and even interstellar ‘planets’. Pluto, Eris, Haumea, and other dwarf planets, including Ceres, are planemos.

You are right; the ‘clearing the neighboorhood’ thing is ABSURD, and I refuse to use the IAU definition of a planet, I will use my own definition (see my second latest comment on ‘why is pluto not a planet/universe today). And I do not agree that a dwarf planet is not a planet even though it is called a dwarf PLANET! Since both planets and dwarf planets are planemos, then they are. Dwarf planets are not between planets and planetoids, they are closer to planets! However, I do believe that perfect planets and dwarf planets are different things. But, as I said, they are two of several subclasses of planemos. And also, I will just add one thing to your definition of planet/planemo: it needs to be massive enough and typically big enough to get into the planetary span (which, however, needs to be defined roughly). All bodies fullfilling this condition would be in hydrostatic equilibrium. Also, I disagree with you that it is OK to define dwarf planet by whether it has cleared its orbit.

Didn’t you mention yourself that it is stupid to determine a planet by that criteria (or, rather, the opposite of it)?Laurel Kornfeld I couldn’t agree more. However, what you are calling a planet is actually termed a ‘planemo’, meaning PLANEtary Mass Object. This includes perfect planets AND dwarf planets, as well as moons the size of planets and even interstellar ‘planets’. Pluto, Eris, Haumea, and other dwarf planets, including Ceres, are planemos. You are right; the ‘clearing the neighboorhood’ thing is ABSURD, and I refuse to use the IAU definition of a planet, I will use my own definition (see my second latest comment on ‘why is pluto not a planet/universe today). And I do not agree that a dwarf planet is not a planet even though it is called a dwarf PLANET! Since both planets and dwarf planets are planemos, then they are. Dwarf planets are not between planets and planetoids, they are closer to planets! However, I do believe that perfect planets and dwarf planets are different things. But, as I said, they are two of several subclasses of planemos.

And also, I will just add one thing to your definition of planet/planemo: it needs to be massive enough and typically big enough to get into the planetary span (which, however, needs to be defined roughly). All bodies fullfilling this condition would be in hydrostatic equilibrium. Also, I disagree with you that it is OK to define dwarf planet by whether it has cleared its orbit. Didn’t you mention yourself that it is stupid to determine a planet by that criteria (or, rather, the opposite of it)? pluto lover I didnt know that pluto was a dwarf planet I thoght it was normal planet.What else is about pluto? Anonymous May 17, 2011 at 2:44 PM In my opinion, however, I beleieve that there are more that 8 planets and 3 dwarf planets. I think that there are thousands of other planets out there, just that scientists haven’t gotten all the information they need, and we can’t give them all the money that they need to research these planets. I don’t know if I believe aliens or not, but I do believe that there is some sort of life up there.

Solar System Planets: Order of the 8 (or 9) Planets Solar System Planets: Order of the 8 (or 9) Planets By Robert Roy Britt | January 22, 2016 12:35pm ET MORE The planets of the solar system as depicted by a NASA computer illustration. Orbits and sizes are not shown to scale. Credit: NASA Ever since the discovery of Pluto in 1930, kids grew up learning about the nine planets of our solar system. That all changed starting in the late 1990s, when astronomers began to argue about whether Pluto was a planet. In a highly controversial decision , the International Astronomical Union ultimately decided in 2006 to call Pluto a “dwarf planet,” reducing the list of “real planets” in our solar system to eight. However, astronomers are now hunting for another planet in our solar system, a true ninth planet , after evidence of its existence was unveiled on Jan. 20, 2016. The so-called "Planet Nine," as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto.

[ Solar System Pictures: A Photo Tour ] If you insist on including Pluto , then that world would come after Neptune on the list; Pluto is truly way out there, and on a wildly tilted, elliptical orbit (two of the several reasons it got demoted). Interestingly, Pluto used to be the eighth planet, actually. More on that below. Terrestrial planets The inner four worlds are called “ terrestrial planets ,” because, like Earth, their surfaces are all rocky. Pluto, too, has a solid surface (and a very frozen one) but has never been grouped with the four terrestrials. Jovian planets The four large outer worlds — Jupiter, Saturn, Uranus, and Neptune — are known as the “Jovian planets” (meaning “Jupiter-like”) because they are all huge compared to the terrestrial planets, and because they are gaseous in nature rather than having rocky surfaces (though some or all of them may have solid cores, astronomers say).

According to NASA , "two of the outer planets beyond the orbit of Mars — Jupiter and Saturn — are known as gas giants; the more distant Uranus and Neptune are called ice giants." This is because, while the first two are dominated by gas, while the last two have more ice. All four contain mostly hydrogen and helium. Dwarf planets The IAU definition of a full-fledged planet goes like this: A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has "cleared its neighborhood" of most other orbiting bodies. Yeah, that’s a mouthful. The problem for Pluto, besides its small size and offbeat orbit, is that it shares its space with lots of other objects in the Kuiper Belt , beyond Neptune. Still, the demotion of Pluto remains controversial . The IAU planet definition puts other small, round worlds in the dwarf planet category, including the Kuiper Belt objects Eris , Haumea , and Makemake . Also now a dwarf planet is Ceres , a round object in the Asteroid Belt between Mars and Jupiter.

Ceres was actually considered a planet when discovered in 1801 and then later deemed to be an asteroid. Some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X ), but that line of thinking opens up the possibility of there being 13 planets, with more bound to be discovered. The planets Below is a brief overview of the eight primary planets in our solar system , in order from the inner solar system outward: Mercury The closest planet to the sun, Mercury is only a bit larger than Earth's moon. Its day side is scorched by the sun and can reach 840 degrees Fahrenheit (450 Celsius), but on the night side, temperatures drop to hundreds of degrees below freezing. Mercury has virtually no atmosphere to absorb meteor impacts, so its surface is pockmarked with craters, just like the moon. Over its four-year mission, NASA's MESSENGER spacecraft has revealed views of the planet that have challenged astronomers' expectations.

Discovery: Known to the ancients and visible to the naked eye Named for: Messenger of the Roman gods Diameter: 3,031 miles (4,878 km) Orbit: 88 Earth days Venus' southern hemisphere, as seen in the ultraviolet. Credit: ESA Venus The second planet from the sun, Venus is terribly hot, even hotter than Mercury. The atmosphere is toxic. The pressure at the surface would crush and kill you. Scientists describe Venus’ situation as a runaway greenhouse effect. Its size and structure are similar to Earth, Venus' thick, toxic atmosphere traps heat in a runaway "greenhouse effect." Oddly, Venus spins slowly in the opposite direction of most planets. The Greeks believed Venus was two different objects — one in the morning sky and another in the evening. Because it is often brighter than any other object in the sky — except for the sun and moon — Venus has generated many UFO reports.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman goddess of love and beauty Diameter: 7,521 miles (12,104 km) Orbit: 225 Earth days An image of the Earth taken by the Russian weather satellite Elektro-L No.1. Credit: NTsOMZ Earth The third planet from the sun, Earth is a waterworld, with two-thirds of the planet covered by ocean. It’s the only world known to harbor life. Earth’s atmosphere is rich in life-sustaining nitrogen and oxygen. Earth's surface rotates about its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second).

Diameter: 7,926 miles (12,760 km) Orbit: 365.24 days Day: 23 hours, 56 minutes Related: Mars researchers are focusing both Earth-based and planet orbiting sensors to better understand sources of methane on the red planet. Image Credit: Space Telescope Science Institute Mars The fourth planet from the sun, is a cold, dusty place. The dust, an iron oxide, gives the planet its reddish cast. Mars shares similarities with Earth: It is rocky, has mountains and valleys, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. It snows on Mars. And Mars harbors water ice. Scientists think it was once wet and warm, though today it’s cold and desert-like. Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time. Scientists think ancient Mars would have had the conditions to support life, and there is hope that signs of past life — possibly even present biology — may exist on the Red Planet.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of war Diameter: 4,217 miles (6,787 km) Orbit: 687 Earth days Day: Just more than one Earth day (24 hours, 37 minutes) Related: Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft. Credit: NASA/JPL-Caltech Jupiter The fifth planet from the sun, Jupiter is huge and is the most massive planet in our solar system. It’s a mostly gaseous world, mostly hydrogen and helium. Its swirling clouds are colorful due to different types of trace gases. A big feature is the Great Red Spot, a giant storm which has raged for hundreds of years. Jupiter has a strong magnetic field, and with dozens of moons, it looks a bit like a miniature solar system.

Discovery: Known to the ancients and visible to the naked eye Named for: Ruler of the Roman gods Diameter: 86,881 miles (139,822 km) Orbit: 11.9 Earth years The shadow of Saturn's moon Mimas dips onto the planet's rings and straddles the Cassini Division in this natural color image taken as Saturn approaches its August 2009 equinox. Credit: NASA/JPL/Space Science Institute Saturn The sixth planet from the sun is known most for its rings . When Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings. The rings are made of ice and rock. Scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium. It has numerous moons .

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of agriculture Diameter: 74,900 miles (120,500 km) Orbit: 29.5 Earth years Day: About 10.5 Earth hours Related: Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which the planet is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory Uranus The seventh planet from the sun, Uranus is an oddball. It’s the only giant planet whose equator is nearly at right angles to its orbit — it basically orbits on its side. Astronomers think the planet collided with some other planet-size object long ago, causing the tilt. The tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years. Uranus is about the same size as Neptune. Methane in the atmosphere gives Uranus its blue-green tint. It has numerous moons and faint rings.

Discovery: 1781 by William Herschel (was thought previously to be a star) Named for: Personification of heaven in ancient myth Diameter: 31,763 miles (51,120 km) Orbit: 84 Earth years Neptune’s winds travel at more than 1,500 mph, and are the fastest planetary winds in the solar system. Credit: NASA/JPL Neptune The eighth planet from the sun, Neptune is known for strong winds — sometimes faster than the speed of sound. Neptune is far out and cold. The planet is more than 30 times as far from the sun as Earth. It has a rocky core. Neptune was the first planet to be predicted to exist by using math, before it was detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth. Discovery: 1846 Pluto and its moons orbit the sun near the edge of our solar system.

Learn all about Pluto's weirdly eccentric orbit, four moons and more in this Space.com infographic . Credit: SPACE.com/Karl Tate Pluto (Dwarf Planet) Once the ninth planet from the sun, Pluto is unlike other planets in many respects. It is smaller than Earth's moon. Its orbit carries it inside the orbit of Neptune and then way out beyond that orbit. From 1979 until early 1999, Pluto had actually been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet — until it was demoted to dwarf planet status. Pluto will stay beyond Neptune for 228 years. Pluto’s orbit is tilted to the main plane of the solar system — where the other planets orbit — by 17.1 degrees. It’s a cold, rocky world with only a very ephemeral atmosphere. NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015.

[Related: New Horizons' Pluto Flyby: Latest News, Images and Video ] Discovery: 1930 by Clyde Tombaugh Named for: Roman god of the underworld, Hades Diameter: 1,430 miles (2,301 km) Orbit: 248 Earth years NASA Solar System Exploration: Dwarf Planets Planet Nine Planet Nine orbits the sun at a distance that is 20 times farther out than the orbit of Neptune. (The orbit of Neptune is 2.7 billion miles from the sun at its closest point.) The strange world's orbit is about 600 times farther from the sun than the Earth's orbit is from the star. Scientists have not actually seen Planet Nine directly . Its existence was inferred by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy objects left over from the birth of the sun and planets. How many planets are in the solar system? How many planets are in the solar system? May 28, 2013 by Fraser Cain, Universe Today The Solar System. Image Credit: NASA I'm just going to warn you, this is a controversial topic.

Some people get pretty grumpy when you ask: how many planets are in the Solar System? Is it eight, ten, or more? I promise you this, though, we're never going back to nine planets … ever. When many of us grew up, there were nine planets in the Solar System. It was like a fixed point in our brains. As kids, memorizing this list was an early right of passage of nerd pride: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto . But then in 2005, Mike Brown discovered Eris, an icy object thought to be about the same size as Pluto, out beyond its orbit. That would bring the total number of planets to ten. Right? There's no turning back, textbooks would need to be changed. In order to settle the dispute, the International Astronomical Union met in 2006, and argued for, and against Pluto's planethood. Some astronomers advocated widening the number of planets to twelve, including Pluto, its moon Charon, the Asteroid Ceres, and the newly discovered Eris.

In the end, they changed the definition of what makes a planet, and sadly, Pluto doesn't make the cut: Makemake. Credit: NASA Here are the new requirements of planethood status: 1. A planet has to orbit the Sun. Okay fine, Pluto does that. 2. A planet needs enough gravity to pull itself into a sphere. Okay, spherical. Pluto's fine there too. 3. A planet needs to have cleared out its orbit of other objects. Uh oh, Pluto hasn't done that. For example, planet Earth accounts for a million times the rest of the material in its orbit, while Pluto is just a fraction of the icy objects in its realm. The final decision was to demote Pluto from planet to dwarf planet. But don't despair, Pluto is in good company. The video will load shortly There's Ceres, the first asteroid ever discovered, and the smallest of the dwarf planets. The surface of Ceres is made of ice and rock, and it might even have a liquid ocean under its surface. NASA 's Dawn mission is flying there right now to give us close up pictures for the first time.

Haumea, named after the Hawaiian goddess of fertility, is about a third the mass of Pluto, and has just enough gravity to pull itself into an ellipsoid, or egg shape. Even though it's smaller, it's got moons of its own. Makemake, a much larger Kuiper belt object, has a diameter about two-thirds the size of Pluto. It was discovered in 2005 by Mike Brown and his team. So far, Makemake doesn't seem to have any moons. Makemake. Credit: NASA Eris is the most massive known dwarf planet, and the one that helped turn our definition of a planet upside-down. It's 27% more massive than Pluto and the ninth most massive body that orbits the Sun. It even has a moon: Dysnomia. And of course, Pluto. The founding member of the dwarf family. Want an easy way to remember the eight planets, in order? Just remember this mnemonic: my very excellent mother just served us noodles. Pluto. Credit: ESO For all you currently writing angry tweets to Mike Brown, hold on a sec. Changing Pluto's categorization is an important step that really needed to happen.

The more we discover about our Universe, the more we realize just how strange and wonderful it is. When Pluto was discovered 80 years ago, we never could have expected the variety of objects in the Solar System. Categorizing Pluto as a dwarf planet helps us better describe our celestial home. So, our Solar System now has eight planets, and five dwarf planets. Astronomers Measured Mass of Largest Dwarf Planet June 18, 2007 Aptly named after the Greek goddess of conflict, the icy dwarf planet, Eris, has rattled the general model of our solar system. The object was discovered by astronomer Mike Brown of Caltech in the outer reaches of the Kuiper ... Recent news on the debate over Pluto's planethood November 29, 2010 Earlier this month, Eris -- the distant world first discovered by Caltech's Mike Brown and colleagues back in 2005, paving the way for the eventual demotion of Pluto from planet to dwarf planet -- passed fortuitously in front ... The Kuiper Belt at 20 September 3, 2012 Planetary science is celebrating the 20th anniversary of the discovery of the Kuiper Belt.

That came in 1992, when the first Kuiper Belt Object (KBO) was discovered. Dwarf planet Makemake reveals its secrets for the first time November 21, 2012 Astronomers have used three telescopes at ESO's observatories in Chile to observe the dwarf planet Makemake as it drifted in front of a distant star and blocked its light. The new observations have allowed them to check for ... Dwarf planet mysteries beckon to New Horizons September 5, 2011 (PhysOrg.com) -- At this very moment one of the fastest spacecraft ever launched -- NASA's New Horizons -- is hurtling through the void at nearly one million miles per day. Launched in 2006, it has been in flight longer ... Picking Planets from Potatoes April 26, 2010 New research indicates that there may be many more dwarf planets similar to Pluto in our solar system than previously thought. Studying these distant objects can help astrobiologists understand the basic properties of our ...

Recommended for you The evolution of massive galaxy clusters January 20, 2017 Galaxy clusters have long been recognized as important laboratories for the study of galaxy formation and evolution. The advent of the new generation of millimeter and submillimeter wave survey telescopes, like the South ... Image: Wavemaker moon Daphnis January 20, 2017 The wavemaker moon, Daphnis, is featured in this view, taken as NASA's Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn's rings on Jan. 16, 2017. This is the closest view of the small ... Observations of Ceres indicate that asteroids might be camouflaged January 20, 2017 The appearance of small bodies in the outer solar system could be deceiving. Asteroids and dwarf planets may be camouflaged with an outer layer of material that actually comes from somewhere else.

Freeze-dried food and one bathroom: Six simulate Mars in dome January 20, 2017 Crammed into a dome with one bathroom, six scientists will spend eight months munching on mostly freeze-dried foods—with a rare treat of Spam—and have only their small sleeping quarters to retreat to for solace. Astronomers search for signs of life on Wolf 1061 exoplanet January 19, 2017 Is there anybody out there? The question of whether Earthlings are alone in the universe has puzzled everyone from biologists and physicists to philosophers and filmmakers. It's also the driving force behind San Francisco ... NASA study in Hawaii paving way for human travel to Mars January 19, 2017 A group of NASA-funded researchers is poised to enter an isolated geodesic dome on a remote Hawaii volcano to study human behavior in long-term space exploration, including a planned voyage to Mars. How Many Planets Are There in the Solar System? How Many Planets Are There in the Solar System?

Home Science Howmanyarethere 03 April 2011 33383 Views There are 8 major planets in our solar system .There were 9 planets which including Pluto too.International Astronomical Union decided that Pluto is no longer a planet , it is a dwarf planet.There are 5 dwarf planets .

Planets from 2006 to present (8) : Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Dwarf planets from 2006 to present (5) : Ceres Pluto Makemake Haumea Eris Planets from 1930 to 2006 (9) : Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Planets from late 19th century to 1930(8) : Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Planets in early 19th century (11) : Mercury Venus Earth Mars Vesta Juno Ceres Pallas Jupiter Saturn Uranus Planets and Dwarf Planets in the Solary System April 5, 2011 at 8:54 pm Our solar system does NOT have only eight planets, and it is far more than a minority of scientists who still view Pluto as a planet and a Kuiper Belt Object. The same is true for Haumea, Makemake, and Eris. Only four percent of the IAU voted on this, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr.

Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. Stern and like-minded scientists favor a broader planet definition that includes any non-self-luminous spheroidal body in orbit around a star. The spherical part is important because objects become spherical when they attain a state known as hydrostatic equilibrium, meaning they are large enough for their own gravity to pull them into a round shape. This is a characteristic of planets and not of shapeless asteroids and Kuiper Belt Objects. Pluto meets this criterion and is therefore a planet. Under this definition, our solar system has 13 planets and counting: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, and Eris. April 21, 2013 at 10:35 pm 11? First of all thats not even correct, second the sun is a star, and the moon is…a fucking moon. Arabs also said the earth is flat in 1993, and said man will never go to outer space, right before we went to outer space.

In no calculation of addition, subtraction, or obsoletion can you arrive at the number 11 for the planets in the Milky Way Galaxy. Please do not bring religion into science, fairy tales and facts do not mix. And before you go jihad on me I’m not just attacking your religion, or attacking religion at all. The Christian bible says god made the sun and the stars on the 4th day. Well how do you have 4 days without a sun to orbit around? I side with several other people that there are still 9 planets, since the reasoning discounting Pluto was essentially just on it’s size and orbitational pattern. The fact is it is still a sphere, it does not light itself, and it orbits a star. Not that I am the expert but switching it to a Dwarf planet was so strongly opposed in the science field, and so many scientists still stand by it as a planet, that I do not find enough evidence or reasoning to consider it a dwarf. But again, my opinion doesn’t really matter. Just dont count them based on a book written by cattle sacrificing primitive’s that believe the earth was made in seven days, or that man is to practice religious conversion at the point of a sword.

If you want to believe something that has been shown to be fundamentally false time and again, that is your right, and noone is going to stop you. But please stop trying to get the rest of us to buy in to fiction, when we have plenty of facts to the contrary. January 31, 2012 at 10:19 pm Pluto should be a planet. I’m just amateur astronomer, but there should be no reason why Pluto should not be included along with the other planets. Pluto has an orbit just like any other planet, however eliptical it may be. yes I agree it is very small but it should not be disqualified as a planet just simply because it does not look like on the other planets and it’s not completely round. if were going to get that technical about planets, then I suggest that we consider the gas giants, which we’re not even sure have any definite planeit structure on the inside, should they be disqualified as planets too? Besides it would confuse all of the first-graders when they are trying to memorize the nine planets. Should we change the rhyme to say my very excellent mother just served us nuts?!!

February 4, 2012 at 5:10 pm Hey V Bellator, Ali Harb IS in the right place. I am not sure about the rest of you though. The Quran says there are 10 planets (11 only in Abraham’s dream – Sura 12, the 11th is imaginery). If you guys are really serious about astronomy, planetary systems, inter stellar material,creation of the worlds (yes, plural), the process of the formation of the universe, read Quran. But before you do that, just to get intellectually ready for it, read “The Bible, The Quran and Science” written by Dr. Maurice Bucaille. The book was originally written in French, but translated by Alastair D. Panell. It will take you to a completely different level, scientifically speaking. March 17, 2014 at 3:25 pm I have an idea to rid the solar system of some planets. Add a 4th criteria. A planet must have or at one point in time had an atmosphere. That goes for dwarf planets. Saying an asteroid, Ceres, is any kind of planet is just ridiculous.

Thats like calling Halley’s Comet a dwarf planet. It goes around the sun, has a rotation on its axis, and its self illuminating. Just for fun, the gas giants have a solid core of at least carbon. If Jupiter didn’t have a solid core we would be a two star system. Now to discredit myself. I have been studying the solar system since I was a kid, watch the moons of Saturn go from 16 to 62+ hundreds of moonlets. I have no credentials in schooling or otherwise. Just that when you see a light in the sky, don’t assume its a star. I might be a planet. Peace Mercury In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky. Mercury has been known since at least the time of the Sumerians (3rd millennium BC). The IAU changed the definition of "planet" so that Pluto no longer qualifies. There are officially only eight planets in our solar system. Of course this change in terminology does not affect what's actually out there.

In the end, it's not very important how we classify the various objects in our solar system. What is important is to learn about their physical nature and their histories. Planet Order from the Sun; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Our knowledge of our solar system is extensive but it is far from complete. Some of the worlds have never even been photographed up close. The Nine Planets is an overview of what we know today. We are still exploring, much more is still to come: We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time. -- T. S. Eliot Dwarf Planets of Our Solar System (Infographic) Dwarf Planets of Our Solar System (Infographic) By Karl Tate, SPACE.com Infographics Artist | November 21, 2012 01:00pm ET MORE Pluto was demoted to dwarf planet status in 2006, joining Eris, Haumea, Makemake and Ceres.

Credit: Karl Tate, SPACE.com contributor In 2006 the organization responsible for classifying celestial bodies, the International Astronomical Union, decided that a new class of objects was needed. The solar system's erratic ninth planet, Pluto, was assigned to the new “ dwarf planet ” category along with four other bodies, all tinier than Earth’s moon. Some astronomers expect there may be as many as 50 dwarf planets in the solar system. Eris , the largest dwarf planet, is only slightly bigger than Pluto, at 1,445 miles in diameter (2,326 km). Discovered in 2003, Eris orbits at an average distance of 68 AU (that is, 68 times the Earth’s distance from the sun) and takes 561.4 Earth years to circle the sun. Eris has the orbit that is most highly inclined of all the dwarf planets, tilted nearly 47 degrees from the plane of the planets’ orbits. A day on Eris takes 25.9 hours. Eris has one moon, Dysnomia.

Pluto , discovered in 1930, orbits the sun at an average of 39.5 times the Earth’s distance. Its diameter is 1,430 miles (2,302 km). Pluto takes 247.9 Earth years to orbit the sun, and its day is 6.39 times as long as Earth’s. Pluto has five known moons: Charon, Nix, Hydra and two that were recently discovered and have not yet been named. Haumea was discovered in 2003. This dwarf planet has an extremely elongated shape, with its longest dimension being about 1,218 miles long (1,960 km). Haumea rotates very rapidly and has the shortest day of all the dwarf planets, only 3.9 hours. Orbiting 43.1 times farther from the sun than Earth does, Haumea takes nearly 282 Earth years to complete one orbit. Haumea has two moons, Hi’iaka and Namaka. Makemake , discovered in 2005, has no known moons.

Makemake orbits at 45.3 times Earth’s distance and takes more than 305 years to complete a circuit of the sun. Its day is 22.5 hours. Makemake’s average diameter is 882 miles (1,420 km). Ceres , first spotted by astronomers in 1801, was first called a planet and later an asteroid. In 2006 it was reclassified as a dwarf planet. Ceres is the closest dwarf planet to Earth, orbiting at only 2.8 times Earth’s distance from the sun. Its year takes 4.6 Earth years and its day is 9.1 hours. Ceres has no known moons. Astronomer Mike Brown (Jump to full table below) In 2006, when the vote on the definition of "planet" was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined.

The "dwarf planets" are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. In other words, a dwarf planet is something that looks like a planet, but is not a planet. Specifically this means that dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction. Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object without and with interesting geological and planetary processes occuring (there are many many other transitions that are equally important, however, a fact that tends to be overlooked in these discussions). How many dwarf planets are there? Ceres is the only asteroid that is known to be round. After that it gets complicated.

All of the rest of the new dwarf planets are in the distant region of the Kuiper belt, where we can't actually see them well enough to know for sure if they are round or not. While we can't see most of the objects in the Kuiper belt well enough to determine whether they are round or not, we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Most Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round. The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn's satellite Mimas, which has a diameter of about 400 km. Several satellites which have diameters around 200 km are not round.

So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round, and thus a dwarf planet. How many objects do we know in the Kuiper belt that are 400 km or larger? That question is harder to answer, because we don't actually know how big most of the objects in the Kuiper belt are. While we can see how bright there are, we don't know if they are bright because they are larger or are highly reflective. In the past, we had to just throw our hands up in the air and say we don't know enough to even make reasonable guesses. But in the past few years, systematic measurements of the sizes of objects from the Spitzer Space Telescope and now the Herschel Space Telescope have taught us enought that we can make some reasonable estimates of how reflective objects are.

(It's complicated: read the details here ) These reasonable estimates, combined with all available actually measurements, give us the list of the largest Kuiper belt objects, sorted by diameter, below. Carefully note the lack of any error bars. Every single measurement or estimate below is uncertain to some extent or another. I don't include the individual uncertainties in the table, but instead use the ensemble uncertainties to inform classification below. In other words: take the sizes of specific objects with bigger or smaller grains of salt. I subjectively divide this list into a few categories, taking into account both the uncertainties in the sizes and the uncertainties in the size where an object becomes round. Near certainty: We are confident enough in the size estimate to know that each one of these must be a dwarf planet even if predominantly rocky. Highly likely Anything larger than 600 km is all but certainly round. Even objects significantly smaller are likely round. The predicted and/or measured size of an object in this category would have to be grossly in error or the composition would have to be primarily rocky in order for it not to be a dwarf planet. Likely: Anything icy larger than 500 km is highly likely to be round.

But the size uncertainties are large enough that some of these objects could, in reality, be small enough to be less certain. Probably: All icy satellite larger than 400 km are round, so we expect these objects to be round if the size estimate is correct. Possibly: We don't know where the transition from non-round to round occurs, but in icy satellites it is between 200 and 400 km. Objects this size in the Kuiper belt could thus possible be round, but we don't know. Probably not: Below 200 km no icy satellite are round. We expect the same in the Kuiper belt. A few of these object could be bigger than expected, however, and could turn out to be large enough to round themselves. The table also lists the estimated albedo used to determine the size or the calculated albedo from the measured size. Also listed is the absolute magnitude, which in this case refers to how bright the object would be if you were looking at it while you were standing on the surface of the sun and the object were at the distance of the earth. As in the rest of astronomy, smaller magnitudes are brighter and every 5 magnitudes represents a factor of 100.

In the comments section I list the source of the size or albedo as described here and add subjective comments when required. As of Thu Jan 5 2017 there are: 10 objects which are nearly certainly dwarf planets, 30 objects which are highly likely to be dwarf planets, 75 objects which are likely to be dwarf planets, 148 objects which are probably dwarf planets, and 703 objects which are possibly dwarf planets. rank

Question: How many planets are there in the solar system?
Answer: Nine