Lab: Exoplanets

PHY 121: The Solar System                                      Name____________________________________
Portland Community College
Grade = __________/53 = __________%
Lab: Exoplanets
Purpose:    The purpose of this lab is explore the vast quantities of data NASA has accumulated on exoplanets and to draw some conclusions about habitable worlds.

  1. Go to the following website:

Once there, examine the data presented and fill-in the following table: (7 points)

All exoplanets 3972
Number of planets found by the transit Method 3061
Number of planets found by the radial velocity method 751
Number of planets actually imaged 45
Number of planets found that are less than 3 Earth masses 28 are less than 3 earth masses
Number of planets greater than 300 Earth masses 331 are greater than 300 earth masses
Total candidates and confirmed planets 4771


  1. Go to the following website:
The NASA Exoplanet Archive has a policy that determines which worlds will be included.  Answer each of the following questions based on that criteria. (8 points)

  • What are the mass requirements?

The mass (or minimum mass) is equal to or less than 30 Jupiter masses.

  • Does the planet have to belong to a star system?

Yes, the planet should belong to a star system as the criteria says that the planet should not be free floating.

  • How do scientists decide that the planet is not a false positive?

After initial data and analysis, sufficient follow-up observations and validation are undertaken to deem the possibility of the object being a false positive unlikely.

  • What is an example of a world not included in the archive? Why is it not included?

An example of an object that has not been included is the companion to SCR 1845. This object was detected via imaging and has an estimated mass larger than the 30 Jupiter mass criteria stated above.

  1. Now you will get to explore some planetary data.  Go to the following website:

The planets in this archive are sorted by various criteria.  One of them is “Planet Mass or M*sin(i) [Jupiter Mass].”  Jupiter’s mass is 318 times that of Earth.  That means Earth like planets will have a mass of approximately 0.003 Jupiter masses. 
Find three such planets and fill-in the following table.  Hint: You can sort the archive by “Planet Mass” by clicking on the up or down arrow in that column.  You will then have to scroll until the mass you’re looking for is present.  You can also insert a range (e.g. [0.002, 0.004]) into the box at the top of the mass column.  That will give you about ten planets. (0.5 points per box, 4 points per table = 12 points total)
Planet #1

Planet Name Proxima Cen b
Planet’s Mass 0.004
Discovery Method Radial velocity
Number of planets in system 1
Orbital period 11.186
Distance in parsecs 1.29
Star’s effective temperature (Kelvins) 3050 K
Stellar mass (solar masses) 0.120

Planet #2

Planet Name GJ 273 c
Planet’s Mass 0.00371
Discovery Method Radial velocity
Number of planets in system 2
Orbital period 4.7234
Distance in parsecs 3.8026
Star’s effective temperature Kelvins) 3382 K
Stellar mass (solar masses) 0.29

Planet #3

Planet Name YZ Cet d
Planet’s Mass 0.00359
Discovery Method Radial velocity
Number of planets in system 3
Orbital period 4.65627
Distance in parsecs 3.6
Star’s effective temperature (Kelvins) 3056 K
Stellar mass (solar masses) 0.130


  1. Earth’s numbers (to compare with the three planets you found) are as follows:

Mass = 1, Planets = 8, Orbital period = 365, Sun’s effective temperature = 5,777 K, and stellar mass = 1.  With that in mind, answer the following questions.
(2 points each = 12 points total)

  • Of the three planets you chose, which is most Earth-like? Explain your reasoning.

GJ 273 c – It has the highest temperature which is close to that of the earth.

  • What is true of the host star masses of all three planets you chose?

All of them has a mass of less than 1.

  • What types of stars are these? Our Sun has an effective temperature of 5,777 K.  How do the temperatures of these parent stars compare?

These are red dwarfs types of stars because of their effective temperature (3000k – 4000k).
The temperatures of these parent stars are less compared to the temperature of the earth by a significant value.

  • All of these planets orbit their parent stars with a very short period. What may these short periods cause?

The change in temperature might not be big enough to notice

  • Which uncertainties are still present despite all of the data acquired?

Most of the acquired data is merely approximations but not exact values so deducing conclusions is not very accurate as per say.

  • Do you think life is likely to exist on any of these worlds? Explain your reasoning.

No. The temperatures are not conducive plus oxygen gas levels might not be enough to support life.

  1. Most exoplanets found are much more massive than Earth, and some are much more massive than Jupiter.  With that in mind, answer the following questions? (4 points total)


  • What challenges might a large (Jupiter like) planet present to life? Cite at least three such challenges.

Life is not possible at Jupiter due to following reasons
(i) Jupiter is a gaseous planet so it has no surface for life to propagate
(ii) There is no H2O (water) present on this planet.
(iii)The atmospheric pressure of this planet is extremely high for any life to develop.

  • Why do you think we have discovered so many large, Jupiter-like, planets?

Due to their large size and large gravitational pull they are easy to discover.
Also the moons of these giant planets are proposed to harbor extraterrestrial life they are of great importance.

  1. Of the exoplanetary discovery methods available to scientists, which do you think is most likely to find Earth-like worlds?  See this link for information on the five ways to find a planet.

Give a “likely” or “not likely” to each method and explain your reasoning behind each method.
(5 points each = 10 points total)

Method Likely or Not Likely and Reason(s)
Radial Velocity Likely. A star’s ‘wobble’ can tell us if a star has planets, how many there are, and how big they are.
Transit Likely. Just like a solar eclipse occurrence this method can be used to find planets like earth.
Direct Imaging Not likely. Light and heat radiation are likely to be an issue in the execution of this method.
Gravitational Microlensing Not Likely. Astronomers can’t predict when or where these lensing events will happen so it’s hard to use this method.
Astrometry Not likely. It’s difficult to detect and that’s why only one planet has been discovered this way.


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