Introductory Astronomy Animations (and Figures)

Planetary Orbits and Kepler's Laws

Integrate the orbits of two planets around a star, neglecting the gravitational force between the planets themselves. This is useful for demonstrating Kepler's third law. We work in units of AU, years, and solar masses. The semi-major axes are picked such that one planet has an orbital period of 1 year and the other of 2 years. This routine dumps out frames that can be assembled into a movie.

source code: orbit2.py

Movie of orbits: orbit.avi

Kepler's Second Law

Show equal areas in equal times, by shading the area swept out by a planet in equal time intervals.

source code: second_law.py

second law animation: second_law.avi

Solar System Harmonic Law Figure

A simple figure plotting the period of planets (+ pluto) in our solar system vs. semi-major axis on a log-log plot, showing the P² ~ a³ relation.

source code: harmonic_law.py

Harmonic law figure: harmonic_law.png

Retrograde Motion

Integrate Earth and Mars in their orbits around the Sun, starting a bit before opposition, and draw a line indicating the line-of-sight to Mars from Earth against some background stars to show the change in apparent motion.

Note: the orbits are simplified here -- the semi-major axis and eccentricity are correct, but it is assumed that both ellipses are oriented the same way. For demonstration purposes, this is not all that critical.

source code: retrograde.py

Movie of retrograde motion: retrograde.avi

Parallax Animation

A simple animation showing how parallax works.

source code: parallax.py

Parallax animation: parallax.avi

Mercury's rotation

Illustrate a 3:2 resonance between the rotation period and orbital period of Mercury. The semi-major axis and eccentricity for the planet drawn match Mercury. The black dot on the surface of the planet represents a person standing initially directly under the Sun at perihelion.

source code: mercury_rotation.py

Mercury rotation animation: mercury.avi

Orbital Energy

A simple showing the orbit of a planet around the Sun, outputting the kinetic energy / unit mass, the potential energy / unit mass, and the total energy / unit mass along the way.

source code: orbitalenergy.py

Orbital energy animation: orbitalenergy.avi

Ellipse Geometry Figure

A simple figure used to illustrate the geometry of an ellipse

source code: ellipse_geom.py

Ellipse geometry figure: ellipse_geom.png

Eccentricity of Ellipses

A demonstration of how varying the eccentricity of an ellipse changes the shape.

source code: eccentricity.py

Ellipse eccentricity animation: eccentricity.avi

How to Draw an Ellipse

A demonstration of how to draw an ellipse. Here we show the distance from each foci to the position on the ellipse, and show that their sum is constant. changes the shape.

source code: ellipsedraw.py

Drawing and ellipse animation: ellipsedraw.avi

Achieving an Orbit

A simple animation that shows a projectile with increasing horizontal velocity, working up to the circular velocity.

source code: achievingorbit.py
(This script uses the image earth.png; image credit: NASA/Apollo 17)

Achieving orbit animation: achieveorbit.avi

Circular vs. Escape Velocity Animation

A simple animation showing how the orbit of a projectile around Earth changes as we increase the change the tangential velocity from less than the circular velocity to greater than the escape velocity.

source code: escapevelocity.py
(This script uses the image earth.png; image credit: NASA/Apollo 17)

Escape velocity animation: escape.avi

Blackbody Spectrum

Show how the Planck function varies as temperature is changed. A "thermometer" on the right keeps track of the temperature. Some reference Planck function curves are plotted every 2 orders-of-magnitude in temperature to illustrate the shift in the location of peak intensity with increasing temperature. Also, the visible frequencies are highlighted with a blue shading.

source code: blackbody.py

Blackbody spectrum animation: blackbody.avi

Random Walk

A demonstration of a random walk process.

source code: random_walk.py

Random walk animation: random_walk.avi

Wave Propagation

Show two waves of different wavelengths to illustrate the difference between wavelength and frequency. The propagation speed of the two waves is the same. The wavelengths are 1 and 1/4 cm, and the velocity is 2.0 cm/s.

source code: waves.py

Wave propagation animation: waves.avi

Doppler Effect

Show a moving source emitting waves. The wavefronts are plotted as red circles. The source has a speed of 1 m/s and the waves have a propagation speed of 2 m/s. The wave frequency is 3 Hz.

source code: doppler.py

Doppler effect animation: doppler.avi

Doppler Effect 2

Show two moving sources emitting waves. The top source has a speed of 1 m/s and the bottom source has a speed of 0.5 m/s. The waves have a propagation speed of 2 m/s and frequency of 3 Hz. This version shows how the compression of wave fronts depends on the line of sight velocity.

source code: doppler2.py

Doppler effect 2 animation: doppler2.avi

Binary Star Orbits

Animation of a binary pair orbiting their common center of mass. The case of e = 0 and e = 0.4 are shown, with a mass ratio of 2.

source code: binary_stars.py

binary star animation (mass ratio = 1; e = 0.0): binary_mratio=1_e=0.0.avi

binary star animation (mass ratio = 1; e = 0.4): binary_mratio=1_e=0.4.avi

binary star animation (mass ratio = 2; e = 0.0): binary_mratio=2_e=0.0.avi

binary star animation (mass ratio = 2; e = 0.4): binary_mratio=2_e=0.4.avi

Radial Velocity Planet Detection (circular orbit)

Illustrate the radial velocity of a star with an unseen planet over the course of a period. Here, the planet's mass was greatly exaggerated to enhance the effect. We also restrict ourselves to being in the plane of the orbits.

source code: radial_velocity.py

radial velocity animation: radial_velocity.avi

Radial Velocity Planet Detection (elliptical orbit)

Illustrate the radial velocity of a star with an unseen planet over the course of a period. Here, the planet's mass was greatly exaggerated to enhance the effect. We use an elliptical orbit but restrict ourselves to being in the plane of the orbits. The semi-major axis is not perpendicular to the observer.

source code: radial_velocity_ell.py

radial velocity animation: radial_velocity_ell.avi

H-R diagram figure

A simple H-R diagram. The main sequence properties are found from Carroll and Ostlie, Appendix G. Lines of constant radius are drawn in, as well as the location of the white dwarfs.

source code: HR_radius.py

H-R diagram figure: HR_radius_wd.png

Radioactive decay figures

A sequence of figures (each represent 1 half life) illustrating the radioactive decay of a sample. Initially 2500 markers are "parents". Each half life, there is a 50% chance a marker decays. After a number of half lifes, no parents remain. A plot showing the exponential decay follows.

source code: radioactive_decay.py

radioactive decay figures:
radioactive_decay_0000.png
radioactive_decay_0001.png
radioactive_decay_0002.png
radioactive_decay_0003.png
radioactive_decay_0004.png
radioactive_decay_0005.png
radioactive_decay_0006.png
radioactive_decay_0007.png
radioactive_decay_0008.png
radioactive_decay_0009.png
radioactive_decay_0010.png
radioactive_decay_0011.png
radioactive_decay_0012.png
radioactive_decay_0013.png
radioactive_decay_0014.png