Spectroscopic search for life Flashcards

1
Q

When is a star in ‘red shift’ and when is it in ‘blue shift’?

A

red shift - moving away

blue shift - moving towards

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2
Q

What are the 3 types of habitable zones?

A
  1. Circumstellar
  2. Galactic
  3. Cosmological
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3
Q

Why does metallicity dictate the galactic habitable zone and what is it influenced by?

A
  • 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
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4
Q

State the 4 areas for star formation in the galaxy and their metallicity properties

A
  1. Halo - oldest and metal poor
  2. Bulge - large ranges of metallicity but there’s a lot of disruptive events, radiation and close encounters
  3. Thin disk - Plenty of star formations and hence high metallicity
  4. Thick disk - more metal poor than thin disk
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5
Q

What are 3 sources of danger in the galaxy and their rate

A
  1. Supernovae (deadly increase in radiation) - 1.5 Gyr
  2. Gamma Ray Bursts (could cause DNA damage) - 2-4 Myr (but short lived)
  3. Active Galactic Nuclei outbursts could damage ozone through higher particle and UV radiation, no frequency given
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6
Q

What is the Galactic Habitable Age range?

A

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

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7
Q

What is the strongest biosignature?

A

The presence of an oxidising and a reducing gas (e.g O2 and CO2)

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8
Q

What are the pros and cons of using N2O, CH3Cl and DMS (dimethylchloride) as biosignatures?

A

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

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9
Q

What is a type I biosignature?

A

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

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10
Q

What is a type II biosignature?

A

biomass building biproducts such as O2/O3 which require outside energy

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11
Q

What is a type III biosignature?

A

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

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12
Q

What are the 2 habitability markers?

A

H2O (can produce O2 abiotically) and CO2 (greenhouse gas and food)

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13
Q

What effect does near UV (NUV) and far UV (FUV) have on O3?

A

NUV - destroys ozone

FUV - creates ozone

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14
Q

Name the star classifications in order of largest to smallest

A

F, G, K, M

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15
Q

What are the levels of NUV and FUV on F stars and M stars?

A

F - High NUV low FUV

M - Low NUV high FUV

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16
Q

Why may plants orbiting an M star be black and plants orbiting a F star be blue?

A

M - black to absorb as much light as possible

F - too much light, adapted to reflect a lot

17
Q

Which part of the global heat flow is IR and UV?

A

IR - Outgoing Longwave radiation

UV - Incoming solar radiation

18
Q

What percentage of the stars in our galaxy are M dwarfs? How many of them have a planet in the habitable zone?

A

75%

1 in 4 estimated to have a habitable zone planet

19
Q

Why are small M stars at an ‘advantage’ for transit data?

A
  • Planets will make a deeper transit depth by percent

- Planets orbit more closely and so have a more frequent transit

20
Q

How long do M stars remain active?

A

Hot M stars - 1-2 Gyr

Cool M stars - 6-8 Gyr (note: Sun was active for 0.5 Gyr)

21
Q

List 6 common false positives O2/O3? Which are common in M dwarfs?

A
  1. Desiccated planets
  2. Super luminous pre-MS dwarf
  3. Lack of cold trap
  4. CO2 photolysis
  5. Inner edge of the habitable zone
  6. CO2 rich/H2 poor planets
    Common for M stars: 1, 2, 4, 6
22
Q

Describe the Super-luminous pre-MS M dwarf false positive scenario

A
  • Extreme UV radiations breaks H2O down into H2 and O
  • O2 atmosphere and H2 escapes to space leaving the planet permanently dry
    Note: similar for inner HZ scenario