Orbital Motions
General Description of the Simulation
In this module, we can provide three sets of related simulations to teach students the following topics.
- Shapes of orbits:
- For a given gravity (hence the mass of the central star), based on the velocity of the secondary, various shapes of orbits are determined: elliptical (including circular), parabolic, and hyperbolic). Simulate these shapes with a range of $V$. Also, scale the Period and Size of the orbit relationship from the Solar System (Earth) ←- Kepler's 3rd Law.
- Orbital motions and planets: Describe the dependency of the reflex motion (of the primary) on the mass of the secondary. Start with a mass ratio of 1:1 and gradually decrease the mass ratio into the planetary range. Magnitude of reflex motions' dependency on masses of primary and secondary. How to measure the reflex motion (astrometry and Doppler).
- Orbital Elements: To know the precise position of a planet at a specific time, we need to know 6 parameters known as
orbital elements. Explain each term with a simulation (i.e., semi-major axis: show a range of orbits with different $a$). This topic (orbital elements) is a difficult and challenging concepts, but from the 6 sets of simulations (for each orbital element), students can understand easily why we need all 6 parameters.
Pending Tasks
We can also add another mode: “Compare the calculation against NASA's predictions”.
A user can type in orbital elements of a choice (select one from a list of pre-populated entries) and observation time. Then, calculate the predicted location of the planet at that time and compare it against NASA JPL horizon predictions. Explain any possible discrepancy (ignorance of other planets in the calculation).
Technical Aspects
Prerequisites
- Textured host star (e.g., Sun) and orbiting body (e.g., planet)
- night sky background
Newly created components from this simulation
- Rendering of planetary motion on an orbit with user adjustable orbital elements sliders.
Comparison against NASA JPL Horizon Ephemeris
- Using the setup and by entering 7 parameters for an orbit (e.g., Mars; 6 orbital elements + time of observation), we can predict the planet's position. Then, we can compare our prediction against precisely calculated NASA's planetary positions which account for gravitational effects among planets as well. The NASA JPL Horizon ephemeris can be calculated from JPL Horizon: (1) select a planet, (2) choose a date, (3) select the output type of “Osculating Orbital Elements” (focus on the true anomaly value).
Astro Concepts
These are underlying astronomical concepts to teach with this simulated topic.
- Concept 1
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Key Scenes
An app in action made by a high school intern (Opeoluwa Oyerinde, GSMST student) using Unity.
We want to create a model in Unity with user interfaces that can do the following demonstration. This example is from pyorb. We can improve this demonstration by adding (1) a background nightsky map, (2) textured host star and a planet, (3) the semi-parent reference plane, (4) some annotations on the screen such as chosen a, e, i, Omega, omega, and nu, and (5) animation of the planetary motion.
These are key scenes of the simulation; based on storyboard files.
- Scene 1
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