Exam 9: The Formation and Structure of Stars

Explain what keeps the nuclear reactions in a star under control; i.e., what would happen if too large an amount of energy is released in the center?

Bok globules are small, dark fragments of the interstellar medium.

The Sun makes most of its energy by the proton-proton cycle.

A star on the ____________________ generates enough energy from nuclear fusion to halt gravitational collapse.

You would like to see through the dust in a cloud to find protostars. Which band of the electromagnetic spectrum would you need to look in?

The free-fall contraction of a molecular cloud

Some young star clusters contain large numbers of T Tauri stars.

How long a star can remain on the main sequence depends upon its __________.

What observations demonstrate the existence of an interstellar medium?

Which is the correct evolutionary order?

The Sun has a core in which energy travels outward primarily by radiation.

What is hydrostatic equilibrium and how is it used to explain the internal stability of a star?

Energy flows by radiation or convection inside stars but almost never by conduction.

________ are star-like objects that contain less than 0.08 solar masses and will never raise their core temperatures high enough that the proton-proton chain can begin. Other minor fusion reactions do occur in these objects. They fall in a gap between the low-mass M dwarf stars and the massive planets in which nuclear fusion never occurs.

The Orion region contains young main-sequence stars and an emission nebula, but the original molecular cloud they formed out of has been dispersed.

___________ associations and ___________ associations are groups of stars born together but not gravitationally bound to one another.

A ZAMS star is located _______________________.

To initiate star formation in a cloud, you need a __________.

_________ are small luminous nebulae excited by nearby young stars.

Protostars are in hydrostatic equilibrium.