Kepler

What is Kepler’s first law?

All orbits are elliptical with the Sun at one focus.

What does perihelion mean? What does aphelion mean?

Perihelion refers to the point in an orbit where an object is closest to the Sun, while aphelion is the point where it is farthest from the Sun.

How do you calculate eccentricity? What is c? What is a?

Eccentricity is calculated using the formula e = c/a, where c is the distance from the center of the ellipse to a focus, and a is the semi-major axis length.

What is the semi-major axis?

Half the circle and the full circle is the major axis

In ellipses what is the range? What do they mean?

The range is from 0-1, with 0 meaning the orbit is circular and 1 meaning the orbit is very stretched out

How eccentric is Earth’s orbit?

0.01 which is almost circular

When is the Earth closest to the sun? When is it the farthest?

The Earth is closest to the sun during perihelion (147 million km), which occurs around January 3rd, and farthest during aphelion (152 million km), around July 4th.

What objects are 90% eccentric?

Comets and the Halley Comet is the most, with it being 0.97

What is the most eccentric planet?

Mercury at 0.21

How to measure eccentricity

Take the focal points (dots) and make another dot in the middle of them, measure from that dot to a focal point which will be C, and then measure the distance from C to the edge of the orbit (A) → e = c/a

What is Kepler’s second law?

An orbiting object varies in speed and distance, the area swept out by an orbiting object over a given time is always the same

What is the formula for Kepler’s second law?

PiAB/total days

How to calculate Kepler’s second law

Take the semi minor axis (half the width) and multiply it by the semi major axis times Pi and divide it by the total number of days in the rotation

What is Kepler’s third law?

Orbital period increases with distance

What is the orbital period?

The time it takes for a celestial body to complete one full orbit around another body, typically measured in days, years, or other time units.

What is the formula for Kepler’s third law?

The formula for Kepler's third law is P² = a³, where P is the orbital period in years and a is the semi-major axis of the orbit in astronomical units.

How do we find the AU of a celestial object?

The astronomical unit (AU) of a celestial object can be found by measuring the object's distance from the Sun, typically using parallax methods or radar ranging for closer objects.