{"id":25320,"date":"2021-10-21T00:00:00","date_gmt":"2021-10-21T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=25320"},"modified":"2021-10-21T12:30:55","modified_gmt":"2021-10-21T12:30:55","slug":"explainer","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2021\/10\/21\/explainer\/","title":{"rendered":"Explainer"},"content":{"rendered":"\n
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Ceres, the planet that never was<\/h4>\n\n

From \u2018comet\u2019 to \u2018planet\u2019, then \u2018asteroid\u2019 to \u2018dwarf planet\u2019, Jane Green looks at the ever-changing classifications of Ceres, which reaches opposition this month<\/p>\n\n

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An image of Ceres taken from a distance of just 13,600km by NASA\u2019s Dawn mission in May 2015 reveals mysterious bright patches<\/figcaption><\/figure><\/div>\n\n

Ask anyone to name a dwarf planet and the answer is likely to be Pluto. Since its discovery in 1930, Pluto had been classed as a classical planet and it wasn\u2019t \u2018demoted\u2019 to its dwarf status until 2006. But it wasn\u2019t the first planet to be reclassified. That honour belongs to the lesser-known dwarf planet Ceres, which happens to reach opposition \u2013 when it will be on the opposite side of Earth to the Sun \u2013 on 27 November. So, it\u2019s a fitting time to shine more than sunlight on this 940km-wide world which has proven to pack a pretty good cryogenic punch.<\/p>\n\n

Ceres is named after the Roman goddess of corn and harvests (she also gives us the word cereal). It was discovered on New Year\u2019s Day 1801, by Catholic priest Giuseppe Piazzi at the Palermo Astronomical Observatory, Sicily. Piazzi\u2019s discovery was the result of a methodical search using the now discredited Titius-Bode Law, named in 1766 after German astronomer Johann Daniel Titius and popularised from 1772 by his countryman Johann Elert Bode.<\/span> This law formulaically predicted a pattern in the size of orbits of the planets and mathematically suggested that another planet existed in the gap between the orbits of Mars and Jupiter.<\/p>\n\n

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One of the dwarf planet\u2019s brightest areas was spotted in the crater Occator \u2013 leading to speculation
of an underground salty reservoir<\/figcaption><\/figure><\/div>\n\n

When Piazzi discovered this \u2018missing planet\u2019 he thought the new \u2018moving star\u2019 was a comet. He observed its \u2018slow\u2019 and \u2018rather uniform\u2019 movement a further 24 times before becoming convinced it was not one. He announced his sighting on 24 January 1801. At the time, it was the only known object between Mars and Jupiter yet it soon became lost in the Sun\u2019s glare and impossible to see. Nevertheless, its orbit was mathematically predicted by the 24-year-old German mathematician Carl Friedrich Gauss, one of the \u2018Celestial Police\u2019 \u2013 an elite group of planet-hunting astronomers who were also making observations of Ceres. However, they kept discovering other objects in similar orbits, and slowly the realisation dawned that they were dealing with an entirely new class of bodies.<\/p>\n\n

In 1802, with the discovery of Pallas, German-born British astronomer William Herschel dubbed this new class of bodies \u2018asteroids\u2019. In 1851<\/span> Ceres was reclassified as an asteroid and designated 1 Ceres, since it had been the first to be discovered. We know now it is the largest of many planetary leftovers forming the asteroid belt between Mars and Jupiter, and accounts for a third of the belt\u2019s mass.<\/p>\n\n

Name changes<\/strong><\/h5>\n\n

There Ceres remained, classified as an asteroid, until August 2006, when the International Astronomical Union (IAU) \u2013 the body responsible for astronomical nomenclature and classification \u2013 determined the three criteria necessary for an object to be defined as a planet. These are: to have enough mass to be nearly rounded by its own gravity \u2013 known as hydrostatic equilibrium; to be in orbit around a star, not be a star itself nor a satellite of a planet; and, crucially, to have cleared the neighbourhood around its orbit. Pluto failed to meet these new criteria and was demoted from being a classical planet to a dwarf planet \u2013 amid some controversy. Ceres, however, was large enough to be rounded by its own gravity and was, therefore, officially upgraded from asteroid to dwarf planet \u2013 the only one inside Neptune\u2019s orbit. Vesta, once second to Ceres, took on the mantle of the largest asteroid.<\/span><\/p>\n\n

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A comparison of sizes between each of the five confirmed dwarf planets in our Solar System and the Moon<\/figcaption><\/figure><\/div>\n\n

Ceres has proven to be an exciting object to explore. NASA\u2019s Dawn spacecraft \u2013 launched 2007 \u2013 arrived at Ceres in 2015, making it the first dwarf planet visited by a spacecraft. As it flew over its cratered surface, Dawn discovered 130 mysterious \u2018bright spots\u2019, the brightest nestling within the recently formed 92km-wide Occator crater. Variations in the gravitational field of Ceres led astronomers to believe they were seeing signs of an underground reservoir of salty water, possibly stretching for hundreds of kilometres and reaching depths of some 40km.<\/span><\/p>\n\n

It\u2019s speculated that many millions of years ago a space rock impacted the area, and elsewhere, puncturing the icy crust of Ceres to release briny fluid from below. The salty crust then froze over, sealing beneath it a chamber of meltwater and a cocktail of chemicals. This later erupted \u2013 perhaps as recently as two million years ago \u2013 in the form of an icy volcano disgorging its frozen contents to splatter and dazzle the shadowy world. Indeed, before Dawn, ESA\u2019s Herschel Space Telescope had detected water vapour in this area. Ceres could be composed of as much as 25 per cent water \u2013 more than Earth \u2013 so who knows what exciting revelations future missions will reveal? Until they do, let\u2019s enjoy this month\u2019s optimum views!<\/p>\n\n

<\/div>
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HOW TO OBSERVE CERES AT OPPOSITION<\/h4>\n\n\n\n

Enjoy the dwarf planet as it appears at its brightest in the night sky<\/strong><\/p>\n\n\n\n

\"\"
Catch Ceres with binoculars at opposition in Taurus on 27 November<\/figcaption><\/figure><\/div>\n\n\n\n

Ceres reaches opposition \u2013a position in space on the opposite side of Earth to the Sun \u2013 in the constellation of Taurus, the Bull, on 27 November. Catch it at its closest approach to Earth when it\u2019s visible at its highest point in the sky around midnight. Its star-like point of light will shine at mag. +7.2, within the range of 10×50 binoculars.<\/p>\n\n\n\n

A binocular object throughout the month, the best times to view Ceres will be from midnight UT on 1 November, 23:00 UT on the 15th and 22:00 UT on 30 November.<\/p>\n\n\n\n

Between 1\/2 and 3\/4 November the dwarf planet passes just south of the red giant star Aldebaran (alpha \u03b1 Tauri) with the pair closest on the night of 2\/3, separated by only 7 arcminutes.<\/p>\n\n\n\n

Thereafter, Ceres crosses the Hyades open cluster, before exiting mid-month towards the constellation of Aries, the Ram.<\/p>\n<\/div><\/section>\n\n

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\"\"<\/figure><\/div>\n<\/div>\n\n\n\n
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Jane Green is an astronomy writer and author of the Haynes Astronomy Manual<\/em><\/p>\n<\/div>\n<\/div>\n\n

Photos: NASA\/JPL-CALTECH\/UCLA\/MPS\/DLR\/IDA, MELETIOS VERRAS\/ISTOCK\/GETTY IMAGES, CHART BY PETE LAWRENCE<\/p>\n","protected":false},"excerpt":{"rendered":"

Ceres, the planet that never was<\/p>\n","protected":false},"author":24,"featured_media":25315,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"72","purple_custom_meta_purple_page_number":"72","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_72-1.xml","purple_custom_meta_purple_source_article":"article_72-1.xml","purple_source_issue":"November-2021","purple_custom_meta_purple_source_issue":"November-2021","purple_external_id":"November-2021-72-1","purple_custom_meta_purple_external_id":"November-2021-72-1","purple_issue_code":"|0000086546||","purple_custom_meta_purple_issue_code":"|0000086546||","purple_android_product":"com.im.skyatnight.198","purple_custom_meta_purple_android_product":"com.im.skyatnight.198","purple_ios_product":"com.im.skyatnight.198","purple_custom_meta_purple_ios_product":"com.im.skyatnight.198","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[21],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"6","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6.jpg",1397,1154,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6-300x248.jpg",300,248,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6-768x634.jpg",768,634,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6-1024x846.jpg",800,661,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6.jpg",1397,1154,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2021\/10\/f99a3fad-9431-400b-9f6a-df18f3219de6.jpg",1397,1154,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"Ceres, the planet that never was","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25320"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=25320"}],"version-history":[{"count":13,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25320\/revisions"}],"predecessor-version":[{"id":26485,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/25320\/revisions\/26485"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/25315"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=25320"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=25320"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=25320"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}