Maximum Elongation of Inner Planets
Maximum Elongation of Inner Planets From the Earth’s perspective, the inner planets seem to stay near the sun. This is because it orbits the inside of the earth. So We cannot see the inner planets in … more
Astronomy Simulation
Stellar Parallax
Parallax When an object is close to me, you can use a ruler to measure the distance. But, it isn’t easy to measure when the object is away from me. In this case, how can you … more
Horizontal Coordinate System
Celestial coordinate system A celestial sphere is an abstract sphere centered on an observer. All objects in the sky can be conceived as projected upon the celestial sphere’s inner surface. Horizontal Coordinate System The horizontal Coordinate … more
Equatorial Coordinate System
Celestial coordinate system A celestial sphere is an abstract sphere centered on an observer. All objects in the sky can be conceived as projected upon the celestial sphere’s inner surface. Equatorial system The equatorial coordinate system … more
Constellations
Constellations If you look at the sky where there is no light on a clear night, there are so many stars that can not count. Thousands of years ago, the ancients linked stars to create constellations … more
Celestial Equator and the Ecliptic
The tilt relationship of the celestial sphere and ecliptic The celestial equator is the enlargement of the earth’s equator to the celestial sphere. Therefore, the celestial equator can be represented by a line fixed on the … more
Apparent Motion of Mars
Apparent Motion of Mars If you observe the motion of Mars, you can see that you go forward and go backward. This procession of Mars has been regarded as mysterious since ancient times. In the past, … more
Eratosthenes’ Calculation of Earth’s Circumference
Eratosthenes’ Calculation of Earth’s Circumference The first person to measure the earth’s size was Eratosthenes, an ancient Greek scientist about 2,000 years ago. Eratosthenes lived in Alexandria, near the Nile River’s mouth by the Mediterranean coast, … more
Tidal Force
Tidal force Earth is not an object like a point (· ), but a rigid body (●) with a certain volume, so the gravity applied to each part is slightly different. This difference in gravity applies … more
Galilean Moons
* This simulation refered the link below for Jupiter’s satellite data. https://en.wikipedia.org/wiki/Galilean_satellite Galilean satellite Jupiter, the largest planet in the solar system, has many moons. Jupiter’s representative moons include Io, Europa, Ganymede, and Calisto. These four … more