Stars Exploration Lab

Overview
In Module 2, we saw the Hertzsprung-Russell diagram (H-R diagram). This diagram plots temperature by spectral types with the true brightness as shown by absolute magnitude.
In this lab, working through a series of web-based interactives, you will see this relationship clearly by viewing the life cycles of stars and the effects of dark matter.

Objective
Complete online interactives exploring the Hertzsprung-Russell Diagram to understand the life cycle of stars and the effects of Dark Matter on stellar systems.

Materials
Computer with internet access and screen-shot capabilities.

Pre-Lab Review
Read and understand the concepts presented in Module 2.

Instructions
Complete Parts I and II (below).
Copy all of your work for both procedures into your Lab Report and submit it as a single document file, preferably PDF, to the Stars Exploration dropbox.
Don’t forget the Claim, Evidence, and Reflection sections.
Be sure to include your 3 Sources as well.

You’ll also need to take screen captures of your work as you go; one way is to use your cellphone to take photos and then transfer them to your computer for insertion into the lab report.
A second way is to use the Alt-PrtScn key combination—this combination allows you to capture your screen display and then Paste (Ctrl-V) into your lab report document.

PART 1: EXPLORING THE H-R DIAGRAM & LIFE CYCLES OF STARS
In your browser, open this link: https://starinabox.lco.global/

This is a simulation called Star In A Box, and will allow us to explore the H-R diagram and how our Sun fits into it. Remember that on the H-R diagram, the y-axis gets brighter as you go up (increase), and the x-axis gets hotter as you go from right to left (not an obvious thing to notice).

Your display should look like this:
If not, make sure you have clicked on the “Open the Lid” option on the lower right of the image. This first screen will show how our Sun looks on the H-R diagram. Click on the
Information option at the top right of the image to see how it all works.
Then, look at the symbols located above the Play button area:

These will tell you, any time you stop the simulation, what the size (in comparison to our Sun), temperature, brightness, stage, and mass of the star you’re looking at.

Instructions:
1. Click on the speed option and choose ‘Slow” at the lower right area. This will slow down the life cycle of our Sun so you can answer our questions.
2. Click the Play button to start the simulation, and answer the following questions.
3. Take screen captures as you go—you’ll need at least 1 for each Part we do.

Questions: Working with the Sun
1. At the beginning of the simulation, locate our Sun; is it on the Main Sequence? If yes, look at the symbols above the ‘Play’ button and click on those; what are it’s temperature (x-axis), brightness (y-axis), stage, and mass? Make sure you use the correct units, for example, temperature is measured in degrees Kelvin (ºK).

2. How long does it take our Sun to just barely move off the Main Sequence (for example, 5000 million years is 5 billion years, 10,000 would be 10 billion years)? At this point, what are the measurements of temperature, brightness, stage, and mass?

3. Stop the simulation or click on the dotted line at the highest temperature (farthest left of the path)–what is the temperature here? Why?

4. At the end of the life cycle path, what how old is the Sun and what are its measurements (as listed in previous questions)?

 

Questions: Working with a star twice our Sun’s mass
(Remember that mass is the physical space an object occupies, the density is how much mass per volume is present there—two different but related terms). An example is Sirius, the dog star, is a nearby star (8.6 light years away) that is about twice our Sun’s mass.

5. On the lower left of the simulation is the option to set the mass to 2 times our Sun’s; temperature (x-axis), brightness (y-axis), stage, and mass?

6. How long does it take Sirius to just barely move off the Main Sequence (for example, 5000 million years is 5 billion years, 10,000 would be 10 billion years)? At this point, what are the measurements of temperature, brightness, stage, and mass?

7. Stop the simulation or click on the dotted line at the highest temperature (farthest left of the path)–what is the temperature here? Why?

8. At the end of the life cycle path, what how old is Sirius and what are its measurements (as listed in previous questions)?

Part II: Gravity & Orbits
In this section, we’ll explore the relationship between gravity and orbits using our Sun and the Earth as examples.
Gravity is a distortion force exerted by objects with mass on other objects with mass.
For example, stars like our Sun pull on planets and moons, causing them to be attracted, but the velocity (speed) of the planets and moons causes them to be forced away at the same time. This will result in stable orbits (or will it?).
Link for activity:https://phet.colorado.edu/en/simulations/gravity-and-orbits Click on the link above to begin the simulation; follow the directions to answer the
questions below.

Instructions:
1. Go to the link above; it should look something like this: There are many controls we can use to manipulate how gravity affects orbits. In the first part, we’ll use 1 planet and see how that works out—then, later on, we’ll use these options to answer questions.
Go ahead and play with the options until you’re comfortable with the simulation—then Ready for the activity? Let’s start.

A. Using 1 Earth-sized planet and 1 Sun-sized star, make sure you have the options “Path”, “Velocity”, and “Gravity Force” clicked. Answer the questions below.
1. Click the Play button .
What does the orbit shape look like? How long did it take the planet to orbit the star?
2. On the options, click Gravity to turn it off (not Gravity Force, the Gravity option above that)–what happened? Why?

B. Reset the simulation. This time, make the star twice as massive as our Earth and run the simulation again.
3. What does the orbit shape look like? How long did it take the planet to orbit the star?

C. Reset the simulation, with the star size back to 1 and the planet size to Earth- sized. This time, choose the upper right option that adds a moon to the planet. Run the simulation.
5. What does the moon’s orbit shape look like? How long did it take the planet to orbit the star this time? Is this different than in the first time we ran the simulation in part A?
6. Change the planet’s mass to 2 and run the simulation—what happened to the moon?