- Practical Exercise 1 DEMONSTRATION OF A SOLAR ECLIPSE
- Practical Exercise 2 SOLAR ECLIPSE MODEL IN THE FIELD
- Practical Exercise 3 APPARENT SIZE OF THE SUN AND MOON IN THE SKY – TYPES OF SOLAR ECLIPSES
- Practical Exercise 4 OBSERVATION OF A TOTAL SOLAR ECLIPSE FROM OTHER PLANETS
- Practical Exercise 5 THE NEAREST SOLAR ECLIPSES
Practical Exercise 4: OBSERVATION OF A TOTAL SOLAR ECLIPSE FROM OTHER PLANETS
Decide whether it is possible to observe a total solar eclipse from other planets in our solar system. Find the necessary data about the planets and their moons on the Internet. Recommended sources: http://astronomia.zcu.cz or https://cs.wikipedia.org.
Objective of Practical Exercise
The aim of this activity is to deepen the idea of the mechanism of solar eclipse and to emphasise as a necessary condition for the occurrence of a total eclipse the existence of another body with the same or larger angular size, which can completely cover the Sun. Furthermore, the aim of this activity is to recall further information about the composition of the solar system, the planets, their moons and the distances between them.
Methodical notes for the teacher
• To successfully complete this activity, pupils must have mastered the basic knowledge of the planets in the solar system and their moons. Alternatively, they must be able to find the necessary information independently on the Internet.
• Some situations can be solved unambiguously only on the basis of qualitative reasoning, others must be calculated quantitatively = compare the angular size of the Sun and the body, which could possibly cover the solar disk.
• It is not necessary to consider the inclination of the trajectory of the covering body relative to the ecliptic plane. This only affects the number of eclipses.
• It is worth mentioning to pupils that there is a total solar eclipse on distant planets, given that at the distance in which these planets move, the sunlight is significantly fainter than on Earth, the solar eclipse will not be as fascinating on these planets as on our planet.
• For each planet, we further indicate whether the reasoning is trivial, standard, or appropriate only for gifted students. According to this, only some planets can be selected.
Sample answer
Mercury: The planet has no moon and is closest to the Sun. There is no body that could cause a total solar eclipse observable from the surface of Mercury. NO (trivial)
Venus: The planet has no moon. The only body that can be located between Venus and the Sun is Mercury. When observed from Venus, the angular size of Mercury is certainly smaller than the angular size of the Sun. (Verification by calculation – diameter of the Sun: 1.4·106 km, distance of the Sun: 108·106 km, angular size 0.013 rad; diameter of Mercury: 5·103 km, minimum distance of Mercury: 50·106 km (half-axis difference), angular size 0.000 1 rad -> the Sun is not covered.) There is no body that could cause a total solar eclipse observable from the surface of Venus. NO (standard)
Mars: The planet has two miniature moons – Phobos and Deimos, and it is necessary to consider the eclipse of the Sun by the Earth. The assumption is that neither body is large enough to cause a total solar eclipse on the surface of Mars. If the Sun does not cover the Earth, it is no longer necessary to consider the inner planets of Venus and Mercury, because they are smaller and further away. (Verification by calculation – diameter of the Sun: 1.4·106 km, distance of the Sun 228·106 km, angular size 0.0061 rad; Phobos diameter 10 km, distance from the surface of Mars 6,000 km (the radius of the orbit minus the radius of Mars), angular size 0.0017 rad -> the Sun is not covered; Deimos is smaller and further away -> does not cover as well; Earth diameter 13 000 km, minimum distance from Mars 54.5·106 km, angular size 0.00024 rad -> the Sun is not covered.) There is no body that could cause a total solar eclipse observable from the surface of Mars. NO (difficult)
Jupiter: The planet has many large moons and is far from the Sun, which already appears very small. Complete eclipses of the Sun may occur caused by the moons of Jupiter. (Verification by calculation for the inner moon Io – diameter of the Sun: 1.4·106 km, distance of the Sun 779·106 km, angular size 0.001 8 rad; Io diameter 3 600 km, distance from the surface of Jupiter 352 000 km (the radius of the orbit minus the radius of Jupiter), angular size 0.01 rad -> the Sun is covered.) A total solar eclipse can occur on the surface of Jupiter. YES (standard)
Saturn: The planet has many large moons and is far from the Sun, which already appears very small. Complete eclipses of the Sun may occur caused by the moons of Saturn. (Verification by calculation for the biggest moon Titan – diameter of the Sun: 1.4·106 km, distance of the Sun 1.43·109 km, angular size 0.000 98 rad; Titan diameter 5 100 km, distance from the surface of Saturn 1.16·106 km (the radius of the orbit minus the radius of Saturn), angular size 0.004 4 rad -> the Sun is covered.) A total solar eclipse can occur on the surface of Saturn. YES (standard)
Uranus: It is many times farther from the Sun than Saturn and has large moons at a short distance. The angular size of the moons is larger than the angular size of the Sun. (Can be supplemented by calculation, see above.) A total solar eclipse can occur on the surface of Uranus. YES (trivial based on previous ones)
Neptune: It is even further from the Sun than Uranus and has the great moon Triton at a short distance. The angular size of Triton is larger than the angular size of the Sun. (Can be supplemented by calculation, see above.) A total solar eclipse can occur on the surface of Neptune. YES (trivial based on previous ones)