AST111 HW11 Exo Planets PDF

Preview

Summary

hw 11 exo planets...

Description

Name:

Garret Kyle Braden Lauder

AST 111: Homework #11 Exoplanets Purpose To simulate how astronomers search for exoplanets

Objectives     

To describe how transits help us discover exoplanets To determine the orbital characteristics of an exoplanet To estimate the physical characteristics of an exoplanet’s parent star To estimate the physical characteristics of an exoplanet To see if an exoplanet resides in the habitable zone of its parent star

Materials/Resources 

How Kepler Discovers Planets animation and Exoplanet Transit Hunt simulation at the home page of the Kepler Spacecraft mission at http://kepler.nasa.gov/index.cfm

Introduction The first planet discovered orbiting another star was 51 Pegasi B, in 1996. Since then, hundreds of planets (“exoplanets” or “extrasolar planets”) in orbit about other stars have been found, most of them by the Kepler Spacecraft. Kepler was launched in 2009, and specifically searches for planets that transit their parent stars. While only a few percent of planets will be aligned (from our point of view) for this to occur, there are so many stars that this still allows for a large number of possible detections. To date, Kepler has discovered hundreds of exoplanets and has several thousand awaiting confirmation. Transits allow us to determine not only specific values of the orbital properties of exoplanets, but also physical properties of the exoplanet, such as its surface temperature, and even if the planet resides in the star’s “habitable” zone, where life may be possible. This activity uses animations and simulations from the Kepler Spacecraft’s official web site to search for a transiting exoplanet and estimate several of its properties.

Part #1: Discovery of Exoplanets Go to the official web site for Kepler, http://kepler.nasa.gov/index.cfm. Click on the section titled “How Does Kepler Find Planets?” and then click on the How Kepler Discovers Planets link. Finally, click on the image to run the animation. 1. Drag the mouse over the Sun. Briefly describe how Kepler gets its energy.

2. Drag the mouse over the star (with planet orbiting). Briefly describe the purpose of the Kepler mission.

3. Drag the mouse over the Kepler spacecraft. Briefly describe how Kepler searches for exoplanets. Specifically, (a) What type of instrument does it use?

(b) How many stars can Kepler observe at once?

(c) How long can Kepler observe these stars?

4. Finally, drag the mouse over the technician. Briefly describe the kind of observations used to confirm the presence of an exoplanet.

Part #2: Simulations of an Exoplanet Now, go back and click on the link Kepler Exoplanet Transit Hunt. Then click on the image to activate the simulation. 1. The first screen shows a blinking star. Click and drag the telescope over the star. (a) Briefly describe what you see – and why the star is blinking:

(b) Which of the following describes a transit? i. ii. iii.

When a large object cuts in front of a small object When an object cuts in front of a similar-sized object When a small object cuts in front of a large object

2. Go to the next page and select a star. It should not matter which one. Then continue to the next page and record its properties below12 (also record in the sim’s note bar):

Spectral Type: _____

Star’s Mass = __________ Mʘ

Star’s Radius = __________ Rʘ

Star’s Temperature = __________ K

3. Click and drag each property to its proper place (you will do this several times). Then proceed to the next page in order to record observations of the exoplanet’s transits: (a) Click on “Start” to begin. Watch the star itself carefully. Whenever it blinks, click on the “Record Blink” button. You can run this several times to get sufficient numbers of observations. (b) Measure the period of the transit. Record the result in the sim’s note bar. Note you can move the scale. It will be more accurate to take several measurements and calculate an average. (c) Measure the dips in brightness. Record the result in the sim’s note bar. Note the lines that appear when you click are the dips in brightness. 1 “Spectral Type” is an astronomer’s method of categorizing stars according to their surface temperatures 2 Note that the symbol “ʘ” refers to the Sun – so, for example, Mʘ expresses the mass of a star compared to the mass of the Sun. Such comparisons are often done because (a) the Sun is our star and (b) the Sun is more or less an average star.

(d) Record the values of the transit below:

Orbital period = __________ days

Change in brightness = __________ %

4. Go to the next page. Follow the directions in order to determine the distance from the exoplanet to its star in terms of astronomical units (AU).

Distance from exoplanet to star = __________ AU 5. Go to the next page. Determine if your exoplanet lies within the star’s habitable zone.3 Does your planet live in its star’s habitable zone?

Is the exoplanet in its star’s habitable zone? _____ 6. Go to the next page. Estimate the surface temperature of your exoplanet. Is your planet much hotter, about the same temperature, or much colder than the Earth? Note the Earth’s average temperature is about 288 K.

Exoplanet’s temperature = __________ K Comparison to Earth: Hotter? Similar? Colder?

7.

Go to the next page. Estimate the size of your exoplanet and whether or not it can retain an atmosphere:

Exoplanet’s radius = __________ Earth radii Does it have an atmosphere? _____

8. Go to the final page. Was this an example of an actual Kepler discovery? (If so, what is its name?)

3 The habitable zone is typically described as the region of space surrounding a star where water can exist as liquid. This does not mean, of course, that life is actually present, merely that it is possible....