final Flashcards
(20 cards)
State the 3 factors you consider most important in determining if an exoplanet is earthlike, and
3 additional factors that you consider less important.
Most important: size and composition, presence of liquid water on surface, and location within star’s habitable zone
Less important: atmosphere, magnetic field, and activity leve of the star
List the steps involved in determining the mass of an exoplanet by the Doppler method, using
words and/or equations.
1) Observe the star’s radial velocity
2) Determine the Velocity Amplitude
3) Find the orbital period
4) Apply Kepler’s Third Law a³ = (GM*/4π²)(P²)
5) Calculate the semi-major axis
6) Calculate the minmum mass of the planet - bc it is edge-on this is close the actual mass
Draw a light curve of a star that indicates an orbiting exoplanet with an orbiting moon, including a time interval for 3 planetary orbits
Answer in other tab
Draw 1 or 2 diagrams of a star, an exoplanet orbiting it, and an exomoon orbiting the exoplanet,
that illustrate how the exoplanet transit can be advanced or delayed in time
Describe how the 21cm spectral line is emitted, and why we often search in that
wavelength for extraterrestrial intelligence.
The 21cm spectral line is emitted when a hydrogen atom transitions between two energy states due to the “flipping” of an electron’s spin. This transition releases a photon with a specific wavelength of 21 cm. Scientists search for extraterrestrial intelligence (SETI) at this wavelength because it’s a prominent radio frequency, ubiquitous in the universe, and easily detectable
Describe 1 reason why signal “BLC1” suggested an intelligent origin, and 2 reasons why it
eventually did not
Yes: initially suggested an intelligent origin because it was a narrowband emission, extremely sharp at a specific frequency, and exhibited a shift in frequency consistent with a moving source.
No: later found that the signal could be explained by natural phenomena, including terrestrial interference or non-terrestrial sources like Proxima Centauri.
If there is a Planet 9, why would it most likely not be detectable in existing imagery, and
how have we eliminated sections of its presumed orbit for its present location?
its extreme distance and expected faintness make it difficult to detect with current telescopes. Additionally, much of its potential orbital path has been ruled out through analysis of Kuiper Belt object dynamics.
State 1 observation suggesting that ‘Oumuamua is controlled by alien intelligence, and one
suggesting it is not.
Yes: its accelerated motion away from the sun without evidence of a gaseous emission
No: it could just be a comet and the acceleration is ecplained by hydrogen outgassing
In 2 brief sentences, what would cause the presumed solar bow shock?
The solar bow shock is caused by the solar wind colliding with the Earth’s magnetosphere. The magnetosphere, acting as an obstacle, causes the solar wind to compress and form a shock wave in front of it.
State 2 observations that were expected, and 1 that was not, from the Voyagers as they left the solar
system
Expected: the dramatic drop in the solar wind particles and the increase in galactic cosmic rays
Unexpected: alignment of the magnetic field beyond the heliopause with the field inside the heliosphere
State 3 proposals for terraforming the Martian atmosphere, and for each, state what parameters it
would “fix”, and roughly how long it might take
1) Creating artificial magnetosphere: shield from solar wind to prevent atmospheric loss. Likely take multiple centuries and advancements in fusion power
2) Seeding Mars with comets: impacts of large comets would inject volatile materials into the atmosphere increasing pressure and releasing other gasses. Also multi-centuries
3) Altering polar albedo: covering portions of the polar ice caps with dark material would increase absorption of solar energy, raising the temperature. Likely faster, multi-decade to a few centuries depending on scale.
You plan to design blimps for human habitation in the atmosphere of Venus. State your 3 most
important factors to consider
1) Pressure resistance (extremely high pressure)
2) Thermal insulation (extremely hot)
3) Materials compatibility with Venusian atmosphere (so it doesn’t explode)
China blew up one of its own weather satellites in 2007 as a test of its antisatellite systems.
Discuss why this may or may not have been a violation of the 1967 Outer Space Treaty.
This may or may not have been a violation of the treaty, depending on how the treaty’s language is interpreted and what aspects of the test are considered. The treaty primarily prohibits the placement of weapons of mass destruction in space and the stationing of such weapons on celestial bodies. While ASATs are not weapons of mass destruction, the test raised concerns about the proliferation of space debris, which could be seen as a threat to future space activities.
Discuss the purpose and current status of the OSIRIS-REx, Dart and Psyche missions.
All focus on the understnanding of asteroids in some way. The OSIRIS-REx mission successfully returned a sample from asteroid Bennu to Earth and is now heading to asteroid Apophis. DART’s primary objective was to test a planetary defense technique by impacting an asteroid to change its trajectory. The Psyche mission aims to study a metal-rich asteroid named Psyche to understand planet formation and interior dynamics.
Draw a horizontal line to represent a linear time axis, with the formation of Earth at the 0-yard
line and the present at the 100. Mark and label the positions of: the first life forms, the first mammals,
the end-Ordovician extinction, the K-T extinction and the appearance of Homo Sapiens.
Describe the Milankovic (Milankovitch in English) cycles with the approximate period for each
1) Eccentricity: shape of Earth’s orbit, flucuating between circular and slightly elliptical. Approximately 100,000 years
2) Obliquity: tilt of Earth’s axis relative to orbital plane. Approximately 41,000 years
3) Precession: wobble of Earth on its axis. Approximately 26,000 years.
During a rocky exoplanet’s transit of its parent star, you see the star appear slightly bluer as well
as darker. What does that tell us about the exoplanet or its atmosphere?
The planet’s atmosphere is absorbing more blue light than other colors, or that the planet itself is absorbing or reflecting more light than initially anticipated.
Name 3 atmospheric molecular constituents that we have already detected on exoplanets
H20 (water vapor), CO2 (carbon dioxide), CO (carbon monoxide)
Many programs are devoted to finding and tracking asteroids. State 2 reasons we are still
concerned that one that could destroy an urban area might collide with earth.
1) The possibility of undiscovered, potentially hazardous objects. While we have likely discovered most of the large, hazardous objects, there is still a lot left to the unknown.
2) The difficulty of deflecting or destoying large asteroids. There are ideas floating around on how to stop large asteroids from hitting Earth, but they are largely untested and still mostly just ideas.
Suppose a 100-meter diameter asteroid is predicted to strike Earth in 2 weeks. Describe what you
think is the best way to avoid Terrestrial damage, and state the major pros and cons of that procedure.
I think we could possibly utilize some of the information from NASA’s DART mission and deflect it using a kinetic impactor; sending a spacecraft to collide with it to change it’s trajectory.
Pros: minimal disruption, DART has already tested small scale similar tech, scalable, environmentally friendly.
Cons: short time frame (only two weeks!), uncertainty of trajectory and compostion, limitations to technology, fragmentation of asteroid into multiple slightly smaller but still large impactors
