## Life Cycles of Stars (Grades 9-12) - Page 15

Blackbody Radiation and Wien's Law

1. Solve Wien's Law for T, substitute in the values for wavelength. With the temperature you obtain, look on the H-R diagram for the corresponding spectral class.

(a) 9656 K Class A; (b) 19,313 K Class B; (c) 5267.2 K Class G; (d) 2317 K Class M

2. Substitute the temperatures into Wien's Law and obtain the wavelengths of the peak emission. Look up on a chart of the EM spectrum which region the wavelength falls into.

(a) 289.7 cm radio; (b) 3.62x10^{-4} cm infrared; (c)
1.93x10^{-5} cm ultraviolet;

(d) 1.65x10^{-7} cm X-ray

Extension:

No astronomical objects are as cold as 0.001 Kelvin. The radio emission we observe is produced by electrons moving in magnetic fields (this is called synchrotron radiation).

Bigger than a Breadbox?

Using the equation: distance = velocity x time,

Cygnus: 9.14x10^{14} km; Crab: 4.46x10^{13} km; Tycho:
6.96x10^{13} km; SN1006: 9.37x10^{13} km

The supernova occurred in the year 1604 and is known as Kepler's supernova. It was observed and documented by the astronomer Johannes Kepler.

A Teaspoonful of Starstuff

Using the equation: mass = density x volume,

We are given that the volume of interest is 5 cm^{3}. So what
is the density of each of the objects? Density equals mass/volume, and the
volume of a sphere is ^{4}/_{3} πr^{3}, where r is the radius of the sphere.
Plugging in the values for each of the types of stars, we find that our
teaspoon of the Sun would contain 7.0 grams; of the white dwarf would
contain 9.5x10^{6} grams; of the neutron star would contain
3.3x10^{15} grams. By looking up the density of water, air, and
iron, you can calculate that each would be 5.0 grams,
6.5x10^{-3} grams, and
39.4 grams, respectively.

Crossing the Event Horizon

1. Using the Schwarzschild equation, we input the mass of
Jupiter (1.9x10^{27} kg), the Gravitational constant (G =
6.67x10^{-11} m^{3}/kg-sec) and the velocity of light
(3x10^{8} m/sec) to see that the event horizon of a Jupiter-mass
black hole would occur at 2.96 meters.