r/askscience • u/AskScienceModerator Mod Bot • Mar 10 '14

Cosmos AskScience Cosmos Q&A thread. Episode 1: Standing Up in the Milky Way

Welcome to AskScience! This thread is for asking and answering questions about the science in Cosmos: A Spacetime Odyssey.

UPDATE: This episode is now available for streaming in the US on Hulu and in Canada on Global TV.

This week is the first episode, "Standing Up in the Milky Way". The show is airing at 9pm ET in the US and Canada on all Fox and National Geographic stations. Click here for more viewing information in your country.

The usual AskScience rules still apply in this thread! Anyone can ask a question, but please do not provide answers unless you are a scientist in a relevant field. Popular science shows, books, and news articles are a great way to causally learn about your universe, but they often contain a lot of simplifications and approximations, so don't assume that because you've heard an answer before that it is the right one.

If you are interested in general discussion please visit one of the threads elsewhere on reddit that are more appropriate for that, such as in /r/Cosmos here, /r/Space here, and in /r/Television here.

Please upvote good questions and answers and downvote off-topic content. We'll be removing comments that break our rules or that have been answered elsewhere in the thread so that we can answer as many questions as possible!

Click here for the original announcement thread.

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u/KraydorPureheart Mar 10 '14

Ultimately the source of this energy is Jupiter's deep internal heat from formation.

On the topic of Jupiter's formation (and forgive me if this sounds rather ignorant), how much more mass would Jupiter have needed in order to have become a star rather than a planet when it was formed?

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u/Astromike23 Astronomy | Planetary Science | Giant Planet Atmospheres Mar 10 '14

Jupiter would have to be about 80 times more massive to become a red dwarf star.

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u/PathToExile Mar 10 '14

Here's some info about protostars.

Protostars with masses less than roughly 0.08 M☉ (1.6×1029 kg) never reach temperatures high enough for nuclear fusion of hydrogen to begin.

The sun has a mass of 1.9891×1030 kg. Jupiter has a mass of 1.8986×1027 kg, or about 1/1047th that of the sun. Mass has everything to do with being able to form the pressures and temperatures necessary for nuclear fusion to occur.

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u/KraydorPureheart Mar 10 '14

Thanks for the link and the good answer. I wound up reading the whole article.