ASTR Chap 16 - Evolution of Low Mass Stars

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The Sun will likely stop being a main-sequence star in:

5 billion years

When a star depletes its core supply of hydrogen, _________ causes the core to collapse while increased gas _________ is exerted on the atmosphere.

gravity; pressure

The evolutionary cutoff between low- and high-mass stars occurs at approximately:

As a main-sequence star burns its core supply of hydrogen, what happens?

Helium builds up as ash in the core.

When a spectral-type G2 star like the Sun leaves the main sequence:

its luminosity increases and its surface temperature decreases

Place the following evolutionary stages in order from youngest to oldest.

Small, Big, Medium

The percentage of hydrogen in the Sun's core today is roughly half of what it was originally.

The Sun will become a red giant star in about 5 billion years.

Using the data in the table below, identify the spectral type of a star that has a main-sequence lifetime of about 10 billion years.

Stars evolve primarily because they use up the fuel in their cores.

If a main-sequence star were gaining mass by being in an interacting binary system, what would happen to that star's luminosity and why?

The luminosity would increase because the star's central pressure would rise and the rate of nuclear reactions would increase.

If the Milky Way formed stars at approximately a constant rate over the last 14 billion years, what fraction of the M-type stars that ever formed in it can still be found as main-sequence stars today? Note that M-type stars have a mass of approximately 0.5 M.

Helium burns in the core of a horizontal branch star via _________ and produces _________.

the triple-alpha reaction; carbon

For low-mass main-sequence stars in hydrostatic equilibrium, at any interior radius there exists a balance between the downward gravitational force at that radius and:

the outward gas pressure from the material inside that radius

The more massive a star is, the more hydrogen it has to burn, and the longer its main-sequence lifetime lasts.

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