A fine line - Astronomy Magazine

Published: June 27, 2011

The distinction between gas giant planets and brown dwarfs ("failed stars") is a vague one. To separate these objects into different groups, astronomers focus on their temperatures and masses. Astronomy: Roen Kelly

Maybe. It depends on what gas giant you’re looking at and how you distinguish a “planet” from a “failed star.” A gas giant found in orbit around a star might be considered a planet like Jupiter around the Sun. An isolated gas giant is probably a failed star. A failed star has such a low mass that its core never gets hot enough to fuse hydrogen, although it might fuse other elements like lithium and deuterium. A planet has an even lower mass and thus never fuses anything.

Subscriber-Only Content

You are currently not logged in. This article is only available to Astronomy magazine subscribers.

Already a subscriber to Astronomy magazine?

If you are already a subscriber to Astronomy magazine you must log into your account to view this article. If you do not have an account you will need to regsiter for one. Registration is FREE and only takes a couple minutes.

Non-subscribers, Subscribe TODAY and save!

Get instant access to subscriber content on Astronomy.com!

Access our interactive Atlas of the Stars
Get full access to StarDome PLUS
Columnist articles
Search and view our equipment review archive
Receive full access to our Ask Astro answers
BONUS web extras not included in the magazine
Much more!

	Sun	Sun	Moon
RISE	—		—	PHASE	—
SET	—		—	DISK	—

	Mercury	Mercury	Venus	Venus
RISE	—		—
SET	—		—
		—		—

	Mars	Mars	Jupiter	Jupiter	Saturn	Saturn
RISE	—		—		—
SET	—		—		—
		—		—		—