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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: 9.14x1014 km; Crab: 4.46x1013 km; Tycho:
6.96x1013 km; SN1006: 9.37x1013 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 1.5 cm3. So what
is the density of each of the objects? Density equals mass/volume, and the
volume of a sphere is 4/3 p r3, 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 2.1 grams; of the white dwarf would
contain 2.85x106 grams; of the neutron star would contain
9.75x1014 grams. By looking up the density of water, air, and
iron, you can calculate that each would be 1.5 grams,
1.935x10-3 grams, and
11.7 grams, respectively.
Crossing the Event Horizon
1. Using the Schwarzschild equation, we input the mass of
Jupiter (1.9x1027 kg), the Gravitational constant (G =
6.67x10-11 m3/kg-sec) and the velocity of light
(3x108 m/sec) to see that the event horizon of a Jupiter-mass
black hole would occur at 2.96 meters.
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