According to modern science, approximately how old is the Sun
4 1/2 billion years
The Sun will exhaust its nuclear fuel in about ______.
5 billion years
Which of the following correctly describes how the process of gravitational contraction can make a star hot?
When a star contracts in size, gravitational potential energy is converted to thermal energy.
What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
gravitational force and outward pressure
The source of energy that keeps the Sun shining today is _________.
When we say that the Sun is a ball of plasma, we mean that _________.
the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)
what is the Sun made of (by mass)?
70% hydrogen, 28% helium, 2% other elements
From center outward, which of the following lists the "layers" of the Sun in the correct order?
Core, radiation zone, convection zone, photosphere, chromosphere, corona
What are the appropriate units for the Sun's luminosity?
The Sun's surface, as we see it with our eyes, is called the _________.
The Sun's average surface (photosphere) temperature is about ______.
What is the solar wind?
a stream of charged particles flowing outward from the surface of the Sun
The fundamental nuclear reaction occurring in the core of the Sun is _________.
nuclear fusion of hydrogen into helium
The proton-proton chain is _________.
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
The overall result of the proton-proton chain is:
4 H becomes 1 He + energy
To estimate the central temperature of the Sun, scientists _________.
use computer models to predict interior conditions
Why are neutrinos so difficult to detect?
They have a tendency to pass through just about any material without any interactions.
Which statement best describes what was called the solar neutrino problem?
Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected.
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about _________.
a few hundred thousand years ago
What happens to energy in the Sun's convection zone?
Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
What do sunspots, solar prominences, and solar flares all have in common?
They are all strongly influenced by magnetic fields on the Sun.
Which of the following is not a characteristic of the 11-year sunspot cycle?
The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
How is the sunspot cycle directly relevant to us here on Earth?
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.