{"id":29176,"date":"2022-04-05T01:54:00","date_gmt":"2022-04-05T01:54:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=29176"},"modified":"2022-05-01T13:53:26","modified_gmt":"2022-05-01T13:53:26","slug":"what-is-a-dwarf-planet","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/what-is-a-dwarf-planet\/","title":{"rendered":"What is a dwarf planet?"},"content":{"rendered":"\n

Vahe Peroomian<\/a>, USC Dornsife College of Letters, Arts and Sciences<\/a><\/em><\/p>\n\n\n\n

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Curious Kids<\/a> is a series for children of all ages. If you have a question you\u2019d like an expert to answer, send it to curiouskidsus@theconversation.com<\/a>.<\/em><\/p>\n\n\n\n

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What is a dwarf planet? \u2013 Myranda, age 8, Knoxville, Tennessee<\/strong><\/p><\/blockquote>\n\n\n\n

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The word \u201cplanet\u201d came from the ancient Greek words that mean \u201cwandering star.\u201d That makes sense, because for thousands of years, people have watched planets change position in the night sky \u2013 unlike stars, which appear fixed and unmoving to the naked eye.<\/p>\n\n\n\n

That\u2019s how the ancients discovered five of the planets: Mercury<\/a>, Venus<\/a>, Mars<\/a>, Jupiter<\/a> and Saturn<\/a>. Astronomers using telescopes found Uranus<\/a> in 1781, Neptune<\/a> in 1846, and Pluto<\/a> in 1930.<\/p>\n\n\n\n

\"Artist's
Artist\u2019s impression of the dwarf planet Eris. ESO\/L.Cal\u00e7ada and Nick Risinger<\/a><\/figcaption><\/figure>\n\n\n\n

Solar system leftovers<\/h2>\n\n\n\n

I\u2019m a space scientist<\/a> with a passion for astronomy and the exploration of the Solar System. I received my Ph.D. in physics in 1994, about the time astronomers began to find more and more objects beyond Neptune, in the Kuiper belt<\/a>. That\u2019s a place in space that holds the \u201cleftovers\u201d of the solar system \u2013 particularly small icy bodies.<\/p>\n\n\n\n

Three of those icy bodies \u2013 Eris<\/a>, Haumea<\/a> and Makemake<\/a> \u2013 were discovered in the early to mid 2000s. They seemed large enough to be planets; all of them are roughly the same size as Pluto.<\/p>\n\n\n\n

Astronomers then surmised that there were likely many more of these icy bodies in the Kuiper belt. They began to wonder: How many planets might we end up identifying in our solar system? Twenty? Thirty? A hundred? More?<\/p>\n\n\n\n

\"An
An artist\u2019s illustration of the dwarf planet Haumea, surrounded by its ring. Instituto de Asrof\u00edsica de Andaluc\u00eda<\/a><\/figcaption><\/figure>\n\n\n\n

Dwarf planet defined<\/h2>\n\n\n\n

In 2006, and after much debate, the International Astronomical Union<\/a> came up with a new definition for a planet. And for the first time, the term \u201cdwarf planet\u201d was used.<\/p>\n\n\n\n

Here\u2019s what the IAU said: A planet has to orbit the Sun directly. It also must be large enough to have a round, or spherical, physical shape.<\/p>\n\n\n\n

And the planet must \u201cclear its neighborhood<\/a>.\u201d That means, aside from any moons it might have, the planet can\u2019t share its orbit with other objects of comparable size.<\/p>\n\n\n\n

An object that satisfies only the first two criteria \u2013 but not the last \u2013 is now called a dwarf planet.<\/p>\n\n\n\n

\"Artist's
Artist\u2019s illustration of Makemake, a dwarf planet in the Kuiper belt. Nearby is its moon, MK 2. Off in the distance: the Sun. NASA\/ESA\/A. Parker\/Southwest Research Institute<\/a><\/figcaption><\/figure>\n\n\n\n

Pluto is demoted<\/h2>\n\n\n\n

That\u2019s why Pluto lost its status as a planet<\/a> and is now classified as a dwarf planet. It failed the final item on the checklist \u2013 other icy Kuiper belt bodies are within its orbital path. The decision, a controversial one to be sure, is debated by scientists to this very day<\/a>.<\/p>\n\n\n\n

At the same time Pluto got demoted, another solar system object was promoted. Ceres<\/a>, once considered an asteroid, is now classified as a dwarf planet. It\u2019s nowhere near the Kuiper belt; instead, Ceres is in the main asteroid belt<\/a>, orbiting between Mars and Jupiter.<\/p>\n\n\n\n

Add them up \u2013 Pluto, Ceres, Eris, Haumea and Makemake \u2013 and that brings the number of dwarf planets in our solar system to five. But that list is sure to grow. Already, hundreds of candidates, nearly all in the Kuiper belt, potentially satisfy the criteria to be a dwarf planet.<\/p>\n\n\n\n

\"A
This photograph of Ceres, a dwarf planet in the main asteroid belt, was taken by NASA\u2019s Dawn spacecraft. NASA\/JPL-Caltech\/UCLA\/MPS\/DLR\/IDA<\/a><\/figcaption><\/figure>\n\n\n\n

About the dwarf planets<\/h2>\n\n\n\n

Dwarf planets are nothing like Earth.<\/p>\n\n\n\n

As their name implies, they are much smaller. Pluto and Eris, the largest of the dwarfs, have less than one-fifth the diameter of the Earth.<\/p>\n\n\n\n

They have less mass, too<\/a>. For example, Earth has about 6,400 times more mass<\/a> than Ceres. That\u2019s like comparing two killer whales<\/a> to a guinea pig<\/a>.<\/p>\n\n\n\n

And dwarf planets are cold. Pluto\u2019s average temperature<\/a> is around minus 400 degrees Fahrenheit (minus 240 Celsius).<\/p>\n\n\n\n

\"A
A photograph of Pluto and one of its five moons, Charon. Except for Ceres, all the dwarf planets have at least one moon. Charon is nearly half Pluto\u2019s size. NASA\/Johns Hopkins University Applied Physics Laboratory\/Southwest Research Institute<\/a><\/figcaption><\/figure>\n\n\n\n

Could life exist on a dwarf planet?<\/h2>\n\n\n\n

Three things are needed for life: liquid water, an energy source and organic molecules \u2013 that is, molecules containing carbon.<\/p>\n\n\n\n

More than 100 miles (161 kilometers) below Pluto\u2019s surface, an enormous ocean of liquid water may exist; this might also be true for other Kuiper belt worlds. Ceres also has subsurface water<\/a>, remnants of what might have been an ancient global ocean.<\/p>\n\n\n\n

Organic molecules, in abundance everywhere in our solar system<\/a>, have been found on Ceres and Pluto.<\/p>\n\n\n\n

But the one missing ingredient for all the dwarf planets is a source of energy.<\/p>\n\n\n\n

Sunlight won\u2019t work, particularly for the Kuiper belt dwarfs; they are simply too far away from the Sun. To reach the belt, the light must travel more than 2.7 billion miles<\/a> (4.4 billion km). By the time the sunshine arrives at these distant worlds, it\u2019s too weak to significantly heat<\/a> any of them.<\/p>\n\n\n\n

And all the dwarf planets are too small to hold the inner heat that remains from the solar system\u2019s formation<\/a>.<\/p>\n\n\n\n

Yet scientists have discovered life on Earth in the most hostile places imaginable \u2013 near the bottom of the ocean, miles deep in the soil and even inside an active volcano. When it comes to life in our solar system, never say never. https:\/\/www.youtube.com\/embed\/nJiw2NxqoBU?wmode=transparent&start=0 Take a tour of the dwarf planet Ceres.<\/p>\n\n\n\n

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Hello, curious kids! Do you have a question you\u2019d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com<\/a>. Please tell us your name, age and the city where you live.<\/em><\/p>\n\n\n\n

And since curiosity has no age limit \u2013 adults, let us know what you\u2019re wondering, too. We won\u2019t be able to answer every question, but we will do our best.<\/em><\/p>\n\n\n\n

Vahe Peroomian<\/a>, Professor of Physics and Astronomy, USC Dornsife College of Letters, Arts and Sciences<\/a><\/em><\/p>\n\n\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Vahe Peroomian, USC Dornsife College of Letters, Arts and Sciences Curious Kids is a series for children of all ages. If you have a question you\u2019d like an expert to answer, send it to curiouskidsus@theconversation.com. What is a dwarf planet? \u2013 Myranda, age 8, Knoxville, Tennessee The word \u201cplanet\u201d came from the ancient Greek words […]<\/p>\n","protected":false},"author":44,"featured_media":29177,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3410],"tags":[11610,6689,6786,11609,6683,11611,10224,2911,11608,343,187],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/29176"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/44"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=29176"}],"version-history":[{"count":2,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/29176\/revisions"}],"predecessor-version":[{"id":29434,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/29176\/revisions\/29434"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/29177"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=29176"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=29176"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=29176"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}