How do astronomers determine planets orbit?
For a long time astronomers thought that the planets orbited in a perfect circular shape but Johannes Kepler revealed that their path were not perfect circle. Most planetary orbits are nearly circular but when Kelper carefully observed and calculated he had established that they are not all perfectly circular. From Kepler’s work which was published between 1609 and 1619, he has improved the heliocentric theory of Nicolaus Copernicus, explaining how the planets speed varies. The planets orbit in an oval shape called ellipse with having the sun be in the middle of it all. Nearly all the planets orbit in the same direction which is counter clockwise except for Venus, Uranus and Pluto, astronomers believe this happens because of the sun’s strong pull of those planets.
With the earth being the third planet from the sun with a radius of 6370 kilometers which is 100 times smaller then the suns radius and the distance of 149 million kilometers away. The earth orbits around the sun once per year with the orbit being slightly elliptical in shape, the orbit defines a plane containing the sun. Since the earth orbits around the sun in a elliptical shape, the earth becomes closes to the sun calling it perihelion which happened during the month of January and the earth being the farthest away from the sun during the month of July called aphelion. The earth takes 23.439 hours to completely rotate on its own axis and take nearly 365.266 days to complete an orbit around the sun which is one calendar year.
In conclusion I really enjoyed learning about the planets in orbit. My questions that I have from after doing this project is how do planets in other galaxies orbit? It is the same orbit path as our galaxies?
http://nineplanets.org/overview.html, https://www.space.com/37054-we-dont-planet-different-orbit-types.html, http://funnel.sfsu.edu/courses/gm310/handouts/orbit_facts.html, https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion