Physical Characteristics of Planets

The planets of the Solar System can be divided into two major classes, terrestrial and Jovian planets, but each planet has their own interesting characteristics. With the Stellarium planetarium software, you can get a close up view of the planets and see their features for yourself.

Background Question – Describe three characteristics of a planet that you think you could measure from visual observations.

Object: Explain the purpose of this laboratory assignment in your own words. What do you think you will accomplish or learn from this exercise?

Hypothesis: Write a simple hypothesis connected to planetary features that you will be able to test using the Stellarium software (for example, Jovian planets have faster rotation period than terrestrial planets)


1)      Open the Stellarium software. Open the location window (F6) and change the planet to the Sun. This will change our observing location to the center of our Solar System.

2)      Open the Sky and Viewing options window (F4). Under the “Sky” tab, uncheck the Atmosphere, Stars, and Dynamic eye adaption. Check “Show planet markers” and “Show planet orbits”.

3)      Select the Landscape tab and uncheck “Show ground”.

4)      Open the Search window (F3) and enter in Mercury. The view should shift such that the Mercury is in the center of the screen. As long as Mercury is actively select, it will remain in your field of view as you advance time.

5)      In the table below, make note of the visible features of Mercury. This can include over color, surface features such as craters or ice caps, presence of an atmosphere and cloud structure, and any visible moons orbiting the planet. You can also advance time and try to observe in the planet has a faster or slow rotation.

6)      Repeat your observer with each of the eight planets. You can use the Search window (F3) to shift your view to each planet.



Atmosphere (yes/no)

Surface Features

Rotation Speed

Any Moons

Q1 In your opinion, which planet had the most distinct appearance?

Q2: Which group of planets (terrestrial or Jovian) appear to have the most moons?

Q3: Which group of planets (terrestrial or Jovian) appear to have the fastest rotation?

Q4: Did you have any problem observing the rotation of any planet? If so, why do you think this was the case?

7)       We can use the small angle formula to find the physical diameter of a planet. Select one planet and record its angular size in arcseconds and distance from the observer (Distance displayed in units of millions of km). The physical size of an astronomical object is equal to the angular size times the object’s distance divided by 206, 265 ( similar formula can be found in the textbook on page 29).


Q5: Compare your calculation with the planet radius information in the textbook (Chapter 6 or Appendix E). Is your calculated radius close to the known value?

9)      Continue using Stellarium to test your individual hypothesis. If you need further direction, please ask your instructor.

Conclusion: In 1-2 paragraphs, explain if your observations and data support or conflict with your hypothesis and if you have met your assignment objective. Was there any portion of the assignment that was particularly interesting or difficult?