Lecture7 - Stellar lifetimes Stars remain close to...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Stellar lifetimes Stars remain close to equilibrium as long as they can fuse hydrogen to make helium, in their core. More massive stars are much more luminous, and use up their fuel more quickly than low mass stars Thus, massive stars have much shorter lifetimes. Typically, the most massive stars only live a few million years. Thus, they must have formed within the last 0.01% of the lifetime of the Universe (13.7 billion years) Low-mass stars have lifetimes longer than the age of the Universe. Stellar energy transport Energy is transported to the surface via either radiation or convection. The Sun has a convective envelope and radiative interior. Low mass main-sequence stars are entirely convective. Convection is poorly understood theoretically, but can be observed as bubbling at the Suns surface The Solar atmosphere The light we see from the Sun is emitted from the photosphere. The atmosphere extends thousands of kilometers above this. In general the atmosphere is very low density, but much higher temperature. Different parts of the Sun are visible at different wavelengths: X-ray: All emitted from the million-degree corona Show a very stormy and dynamic atmosphere, the source of the solar wind Ultraviolet : UV radiation comes from the chromosphere, between the photosphere and corona Infrared: Long-wavelength radiation from the chromosphere and corona Dark spots caused by absorption of light due to denser gas in the atmosphere. Radio : Emitted near the transition region between the chromosphere and corona The Solar Wind Small particles in comet tails are being accelerated away from the Sun faster than can be accounted for by radiation pressure....
View Full Document

This note was uploaded on 04/15/2009 for the course PHYS 275 taught by Professor Harris during the Winter '09 term at Waterloo.

Page1 / 13

Lecture7 - Stellar lifetimes Stars remain close to...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online