Spectroscopic search for life Flashcards
When is a star in ‘red shift’ and when is it in ‘blue shift’?
red shift - moving away
blue shift - moving towards
What are the 3 types of habitable zones?
- Circumstellar
- Galactic
- Cosmological
Why does metallicity dictate the galactic habitable zone and what is it influenced by?
- Metal elements (higher than H and He because astronomers are weird like that) necessary to form planets with molten cores which produce plate tectonics, magnetic fields, and can retain an atmosphere to shield from UV
- Too little metals and you get hot jupiters which may clean out habitable planets in migration (assholes)
- Determined by star formation and supernovae rates
State the 4 areas for star formation in the galaxy and their metallicity properties
- Halo - oldest and metal poor
- Bulge - large ranges of metallicity but there’s a lot of disruptive events, radiation and close encounters
- Thin disk - Plenty of star formations and hence high metallicity
- Thick disk - more metal poor than thin disk
What are 3 sources of danger in the galaxy and their rate
- Supernovae (deadly increase in radiation) - 1.5 Gyr
- Gamma Ray Bursts (could cause DNA damage) - 2-4 Myr (but short lived)
- Active Galactic Nuclei outbursts could damage ozone through higher particle and UV radiation, no frequency given
What is the Galactic Habitable Age range?
Must be above 2 Gyr - time needed to have enough metals to build terrestrial planets
Must be below 20 Gyr - growth of structure ceases, slow star formation and lower internal heat from radioactive isotopes
What is the strongest biosignature?
The presence of an oxidising and a reducing gas (e.g O2 and CO2)
What are the pros and cons of using N2O, CH3Cl and DMS (dimethylchloride) as biosignatures?
pros: no known abiotic source of these gases
cons: are produced in really small abundances because they are from highly specialized evolutionary pathways like a specific signaling mechanism for one single organism
What is a type I biosignature?
redox grandient energy extraction by-products based on thermodynamics such as CH4 or NH3
High possibility of a false positive as they are equally favourable for Geology
What is a type II biosignature?
biomass building biproducts such as O2/O3 which require outside energy
What is a type III biosignature?
secondary metabolic byproducts which are produced by life for functions such as defense, signaling or physiological control that do not require energy from the environment
low possibility for false positive but also low abundance
What are the 2 habitability markers?
H2O (can produce O2 abiotically) and CO2 (greenhouse gas and food)
What effect does near UV (NUV) and far UV (FUV) have on O3?
NUV - destroys ozone
FUV - creates ozone
Name the star classifications in order of largest to smallest
F, G, K, M
What are the levels of NUV and FUV on F stars and M stars?
F - High NUV low FUV
M - Low NUV high FUV