12 Chapter 12 – Are there aliens and can we find them?
OpenStax Astronomy Chapter 30: Life in the Universe
Chemistry of Life
I.
A. on primarily made of elements: (CHNOPS)
1. made of CHONP
B. Life is on , because it’s
C. Carbon is : spots for other
1. Can form easily and make molecules like
D. is also tetravalent, so might be a for life
1. than Carbon at , so good for planets
2. than Carbon, so chains that are as
3. Likes bonding with (SiO2 is sand), so in
Which one of the following is NOT one of the six chemical elements commonly found in living organisms?
A. Helium
B. Phosphorus
C. Hydrogen
D. Nitrogen
Life in the Solar System?
II. for Life in the
A. Look for things for life:
B. : candidate of
1. Has an and , had on surface in the
2. current for of any kind
3. Missions still for or under surface
C. of the Planets
1. : Jupiter’s moon
a. Layer of on top of an (up to 100 miles deep)
b. Evidence of warming the ocean
2. : Saturn’s largest moon
a. and rock on surface
b. Rich in (carbon-based) and other good chemistry
c. Has nitrogen-rich and liquid lakes
3. : small moon of Saturn
a. Water ice and ocean
b. Internal causing cryovolcanoes, geysers that spew water
c. Some found in geyser plumes
Most of these statements are reasons to look for life in the Solar System. Which one is NOT?
A. Mars had a warmer and wetter past.
B. Enceladus is too far from the Sun for water to be liquid.
C. Europa has oceans under its surface.
D. Titan has organic material.
Life on Exoplanets?
III. : extrasolar planets around
A. for should:
1. Have (small eccentricity): very orbits cause big
2. Be in the (Goldilocks Zone): from star (semimajor axis) where is for on a planet
a. Estimate of stars have planets in Habitable Zone
3. Be the (mass and radius): planet with an
a. Too , planet is likely a
b. Too , likely
c. : size , but than Earth, if gas or rocky
4. Have the right : with a and a good size zone
a. hotter stars: habitable zone, but so enough for life to develop
b. cooler stars: smaller, habitable zone, , better place to look for planets with life
Which of these planets is most likely to have life?
A. A planet very far from a cool red star
B. A planet very close to a Sun-like star
C. A planet near a hot blue star
D. A planet near a star somewhat cooler than the Sun
Search for Extraterrestrial Intelligence
IV. for and from Life
A. spacecrafts explored the carrying a depicting (1970s)
B. Two spacecraft carry of greetings, music, messages, and animal sounds (1970s)
1. Now in space beyond the Solar System
C. The Arecibo to the star cluster M13 in 1974
1. Will take years to get an answer because stars are so far away
D. (Search for Extraterrestrial Intelligence) and the Allen Telescope Array in California for from technologically advanced civilizations
What is the best reason there may be many advanced civilizations in the Universe according to current science?
A. There are billions and billions of stars in the universe.
B. Any planet with life will also have intelligent life.
C. We have found lots of planets that are exactly like Earth.
V. The (Frank Drake, 1960)
A. Estimates the of advanced in the
B. List of in finding
1. First are based on well-known , so have a good idea of numbers
2. Last are based on life and some
C. Multiply the following factors together:
1. Number of that each (2 – 7)
2. of stars (0.5 – 1)
a. stars have planets
3. Number of per star (1 – 4)
a. Solar System has , but exoplanet systems may have more
4. Fraction of planets with (0.1 – 1)
5. Fraction of planets with (0.01 – 1)
6. Fraction of intelligent that develop (0.1 – 1)
a. Can send into
7. Number of such advanced (1000 – 1 million years)
D. is the likelihood advanced in that we might be able to
1. (low) estimates give N =
a. We are in the Milky Way
b. Have to go light years or more to other to find life
2. (high) estimates give N =
a. One advanced civilization in every stars
a. Nearest would be only light years away
If the most pessimistic assumptions in the Drake equation were true, we would:
A. be able to find life in the Solar System
B. have to wait for approximately 100 years to get a message back from the nearest intelligent life.
C. be the only intelligent life in the Milky Way.
D. be one of millions of intelligent civilizations in the Milky Way.
Resources
Exoplanet Catalogs: https://science.nasa.gov/exoplanets/exoplanet-catalog/ and https://exoplanet.eu/home/
Alien Civilization Calculator – Drake Equation Calculator: https://www.omnicalculator.com/physics/alien-civilization
Tutorial Activity – Life on an Exoplanet?
Use the following data about a known exoplanet, 55 Cancri f, and Earth to answer the questions and determine if the exoplanet might host life.
| Exoplanet: 55 Cancri f | Earth | |
| Mass | 0.173 Jupiter Masses | 0.00315 Jupiter Masses |
| Distance to star | 0.774 AU | 1.0 AU |
| Time to orbit star | 261.2 days | 365 days |
| Orbit eccentricity | 0.32 | 0.017 |
| Mass of star | 0.905 Solar Masses | 1.0 Solar Masses |
| Temperature of star | 5196 K | 5778 K |
1. (a) How does the temperature of the exoplanet’s star compare to the Sun?
(b) Do you think the habitable zone is closer or farther away from the star than in our Solar System?
2. (a) How does the exoplanet’s distance from its star compare to Earth’s distance from the Sun?
(b) Do you think this exoplanet is in the habitable zone?
3. (a) How does the exoplanet’s orbit eccentricity compare to Earth’s? What does this mean?
(b) Do you think this planet’s climate and weather are affected by its eccentricity? Why or why not?
4. (a) How does the exoplanet’s mass compare to Earth’s?
(b) What type of planet do you think it is?
5. Based on what you have learned, would you expect to find life on this planet? Why or why not?
Tutorial Activity – Fermi Paradox
Consider the Fermi paradox: If they are out there, why aren’t they here? (or why haven’t they contacted us?)
Brainstorm some possible solutions to the paradox. Write at least 5 sentences discussing possible solutions and which solution is most likely in your opinion.
