Dr. Aaron Titus | Department of Physics, High Point University PHY1050      Astronomy of Stars, Galaxies, and the Cosmos home | WebAssign | textbook | course calendar

## lab--astrometry of asteroids

How do we find solar system objects such as asteroids and KBOs, and how do we determine their orbits?

The answer is that we take pictures (perhaps minutes or hours apart) of a region of the night sky and look for any objects that move relative to the background stars.

Using the background stars as a reference, we measure the RA and DEC of the moving object. By calculating the change in the angular position of the object per second, we can determine how fast it moves across our sky (in degrees per second).

If we know the distance to the object, then we can measure how fast it moves across our sky in km/s. By measuring the distance to the object at different times, we can calculate how fast the object moves toward or away from us; this is called radial velocity. After doing these calculations repeatedly for many months or years, we can determine the object's orbit.

In this experiment, you will determine the angular speed of an asteroid and the distance to the asteroid.

### Procedure

We will use the CLEA program called Astrometry of Asteroids. You should have already installed it.

1. Download two files: (1) the handout that describes what to do for this experiment; and (2) the spreadsheet used to do the calculations. Read the handout briefly before continuing.

2. Watch the following instructional videos that show you how to use the Astrometry of Asteroids simulation.

CLEA: Astrometry of Asteroids -- Part 1. This video describes how to load images and blink the images to see the asteroid.

CLEA: Astrometry of Asteroids -- Part 2. This video describes how to measure the RA and DEC for the asteroid and how to calculate the angular speed of the asteroid.

CLEA: Astrometry of Asteroids -- Part 3. This video describes how to measure to measure the parallax angle for the asteroid and how to use this to calculate distance to the asteroid.

3. Make the measurements described in the handout and enter your data in the spreadsheet.

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