{"id":1786,"date":"2024-12-01T09:31:19","date_gmt":"2024-12-01T06:31:19","guid":{"rendered":"https:\/\/planeta21vek.ru\/eng\/?p=1786"},"modified":"2025-11-20T12:38:25","modified_gmt":"2025-11-20T09:38:25","slug":"phaethon-is-an-asteroid-that-thinks-its-a-comet","status":"publish","type":"post","link":"https:\/\/planeta21vek.ru\/eng\/2024\/12\/01\/phaethon-is-an-asteroid-that-thinks-its-a-comet\/","title":{"rendered":"Phaethon is an asteroid that thinks it’s a comet"},"content":{"rendered":"

What is the difference between an asteroid and a comet? A comet is essentially a dirty ball of ice, made up of rock and ice. The classic image is of a bright \u201cstar\u201d in the night sky with a long, curving tail stretching into space as it approaches the sun and begins to release gases and dust. This usually continues until there is nothing left but rock, or until the comet disintegrates into dust.<\/span><\/p>\n

<\/p>\n

Asteroids, on the other hand, are primarily just rocks. They may conjure up images of Hans Solo piloting the Millennium Falcon through an incredibly dense \u201casteroid field\u201d to escape a swarm of TIE fighters, but mostly they just orbit the sun quietly, minding their own business, The Conversation reports.<\/span><\/p>\n

However, these two cosmic objects are not always as mutually exclusive as one might assume. Phaethon is a \u201crock comet\u201d that blurs the lines between asteroid and comet. Phaethon was discovered by accident in 1983 by two astronomers from the University of Leicester, Simon Green and John Davies. They stumbled upon it orbiting the Sun while analysing images taken by a space telescope called the Infrared Astronomical Satellite (Iras). Soon after, other astronomers recognised Phaethon as the source of the annual Geminid meteor shower, one of the brightest meteor displays on Earth\u2019s calendar.<\/span><\/p>\n

Every December, when our planet crosses the dust trail left by Phaeton, we witness a spectacular spectacle as its dust particles burn up in our atmosphere. However, Phaeton’s behavior is not like that of other objects responsible for meteor showers.<\/span><\/p>\n

Unlike typical comets, which shed significant amounts of dust as they heat up near the Sun, Phaethon does not appear to be releasing enough dust today to account for the Geminids. This lack of significant dust emissions raises an interesting problem.<\/span><\/p>\n

\"\"
\nPhaeton. University of Arizona\/Heather Roper<\/span><\/em><\/p>\n

Phaeton’s orbit brings it very close to the Sun, much closer than Mercury, the innermost planet in the Solar System. At its closest approach (called perihelion), its surface temperature reaches extreme values \u200b\u200bof about 730\u00b0C.<\/span><\/p>\n

One would expect such intense heat to strip away any volatile material that exists on Phaethon’s surface. This would either expose fresh, unheated layers and shed huge amounts of dust and gas every time it passes close to the sun, or form a barren crust that protects the volatile-rich interior from further heating, resulting in no emissions of gas or dust.<\/span><\/p>\n

However, neither of these processes seems to be happening. Instead, Phaethon continues to exhibit comet-like activity, emitting gas but not the accompanying dust cloud. It is therefore not shedding layers, leaving the mystery of why the same crust can still emit volatile gases every time it is heated by the sun.<\/span><\/p>\n

The scientists used fragments of a rare group of meteorites called CM chondrites, which contain clays thought to be similar in composition to Phaethon, and heated them in an oxygen-free environment several times, simulating the hot-cold\/day-night cycles that Phaethon experiences when it is close to the sun.<\/span><\/p>\n

The results were surprising. Unlike other volatiles, which typically disappear after a few heating cycles, the small amounts of sulfur gases contained in meteorites were released slowly, over many cycles.<\/span><\/p>\n

This suggests that even after numerous close passes of the Sun, Phaethon still has enough gas left to generate comet-like activity during each perihelion.<\/span><\/p>\n

The theory is that when Phaethon’s surface heats up, the iron sulfide minerals in its interior break down into gases like sulfur dioxide. However, because Phaethon’s surface layers are relatively impermeable, these gases cannot escape quickly. Instead, they accumulate beneath the surface, such as in pores and cracks.<\/span><\/p>\n

\"\"
\nGeminid Stream<\/span><\/em><\/p>\n

As Phaethon rotates, which takes just under four hours, day turns to night and the interior cools. Some of the trapped gases are able to “react back” to form a new generation of compounds. When night turns to day again and heating resumes, they decompose and the cycle repeats.<\/span><\/p>\n

These results are not just academic, but also have implications for the Japanese Space Agency’s (Jaxa) Destiny+ mission, scheduled to launch later this decade. The spacecraft will fly past Phaethon and study it with two multispectral cameras and a dust analyzer, which will hopefully collect particles that will provide further clues about the composition of this mysterious object.<\/span><\/p>\n

In any case, the research team’s theory about Phaethon’s outgassing processes will be crucial to interpreting the data. It will change the way scientists think about solar heating as a geological process, making it relevant not only to comets but also to asteroids.<\/span><\/p>\n

The important thing is that Phaethon is not alone. About 95 asteroids pass within 0.20 astronomical units (almost 19 million miles) of the Sun. Everything we learn about Phaethon can give us insight into their behavior and long-term stability.<\/span><\/p>\n

What does all this have to do with the Geminid meteor shower? Most likely, Phaethon emitted dust many years ago. This would have created the debris stream that creates the Geminid shower every time the particles come into contact with Earth’s atmosphere. When it comes to the gifts that keep on giving, it’s hard to think of a better example.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

What is the difference between an asteroid and a comet? A comet is essentially a dirty ball of ice, made up of rock and ice. The classic image is of a bright \u201cstar\u201d in the night sky with a long, curving tail stretching into space as it approaches the sun and begins to release gases and dust. This usually continues until there is nothing left but rock, or until the comet disintegrates into dust.<\/p>\n","protected":false},"author":1,"featured_media":1787,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[543,40],"tags":[315,828,848,807,847],"class_list":{"0":"post-1786","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-solar-system","8":"category-kosmos","9":"tag-asteroid","10":"tag-comet","11":"tag-geminids-shower","12":"tag-meteor","13":"tag-phaeton"},"_links":{"self":[{"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/posts\/1786","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/comments?post=1786"}],"version-history":[{"count":1,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/posts\/1786\/revisions"}],"predecessor-version":[{"id":1788,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/posts\/1786\/revisions\/1788"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/media\/1787"}],"wp:attachment":[{"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/media?parent=1786"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/categories?post=1786"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planeta21vek.ru\/eng\/wp-json\/wp\/v2\/tags?post=1786"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}