{"id":45439,"date":"2023-06-03T07:34:14","date_gmt":"2023-06-03T07:34:14","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=118844"},"modified":"2023-06-03T08:32:32","modified_gmt":"2023-06-03T08:32:32","slug":"can-a-star-be-smaller-than-a-planet","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/can-a-star-be-smaller-than-a-planet\/","title":{"rendered":"Can a star be smaller than a planet?"},"content":{"rendered":"

What makes an object large enough to be a star? Can a planet be larger? <\/p>

By Lewis Dartnell\n \t\t<\/p>

Published: Saturday, 03 June 2023 at 12:00 am<\/p>

\n\n

Stars must be massive enough to sustain nuclear fusion in their cores, crushing together hydrogen nuclei to forge helium and then other elements up to iron.<\/p>\n

Planets, on the other hand, can be small and rocky like Earth, or large with a bloated hydrogen and helium atmosphere like Jupiter<\/a>.<\/p>\n

However, a planet can never burn with its own light like a star.<\/p>\n

Jupiter is over 300 times heavier than Earth, but this is still less than 0.1% the mass of the Sun.<\/p>\n

The biggest a planet can grow is 13 times larger than Jupiter.<\/p>\n

It then becomes a sub-stellar object capable of limited fusion known as a \u2018brown dwarf\u2019.<\/p>\n

\""Brown\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Artist\u2019s impression of a brown dwarf<\/span><\/figcaption><\/div>\n

It takes an object larger than about 80 Jupiter-masses to begin burning as a star in its own right.<\/p>\n

Despite the plot of the sci-fi book, 2001: A Space Odyssey<\/i>, Jupiter could never be \u2018switched-on\u2019 to burn as a star.<\/p>\n

The search for extra-solar planets \u2013 known as exoplanets<\/a> \u2013 has unearthed some truly massive worlds, some more than 20 times that of Jupiter.<\/p>\n

But a planet can never be bigger than its star without bursting into light as a star itself and forming a binary star system.<\/p> <\/body><\/html>\n

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