Task 1: Determining the Distance of Venus from the Sun

 If this mission is about exoplanets, why are we starting with the Solar System? Click the box below to find out.

Why are we starting with Venus?

Studying our own Solar System helps scientists figure out how best to study planets outside of the Solar System. Think of Johannes Kepler. He used data from planets that he could observe directly to formulate general laws that describe the motion of all planets, including some that hadn’t even been discovered at the time of his original observations! Observing the transit of Venus allowed scientists to practice studying transits.

image of Venus’ transit of our Sun. Appears orange and yellow.

Hover your cursor over this image to reveal a hint.

image of a scientist

Modern scientists study the motion of planets in our Solar System to figure out ways to find and study planets around other stars. In the same way, you will first find the distance of Venus from the Sun using a light curve.

To find the distance of Venus from the Sun, you will need to use Kepler’s Third Law.

Kepler's Third Law Equation. The average distance from the planet to the star equals the mass of the star multiplied by the period of the planet. Pointed to and circled in the image is the period of the planet, p

Look confusing? Don’t worry, you don’t have to do this math by hand! Input your numbers into the google sheet as directed below and the equations will be automatically calculated for you.

Below is the simulated light curve of the Sun when Venus transits.

Simulated Light Curve graph. Flux on the y axis and days on the x axis. Markings at 230 days 450 days and 675 days.

 Using the simulated light curve above, fill in the values for three transits of Venus in cells B2, B3, and B4 of the Google Sheet below. The mid-transit points are indicated by the red lines on the light curve. The period of Venus will be automatically calculated for you in units of Earth years in cell B5.

The google sheet support

Let’s go back to Kepler’s Third Law to figure out what we need to do next.

In this case, Venus’ star is the Sun, so the mass of the star is 1 solar mass (M☉
).

Now, we are ready to calculate the distance of Venus from the Sun.
Write the mass of the star in cell B6 of the Google Sheet. The distance of Venus from the Sun (a) will be automatically calculated in units of AU in cell B7of the Google Sheet.

What are au?

Astronomical Units, AU diagram. Defines AU as the distance between the Earth and the sun with an arrow in between an image of the sun and the Earth.

gif of different planet orbits. Image reads: Distance from the host star helps determine if the planet is in its star's habitable zone.

image of a yield sign with a question mark

Hover your cursor over this image to check your work.

Great job following along with the example! Now, it’s time to put your skills to the test and analyze the light curve for the star, Kepler 452, to get the period of your planet.

continue to period