Exam 1

Fictional portrayal of extraterrestrial life

similar to terrestrial life

How we define extraterrestrial life

ongoing challenge, could be single-celled, multicellular, or unknown

What we are looking for

liquid water, possible debris of other civilizations, occurrence of life elsewhere, conditions and context conducive to life

fields of astrobiology

astronomy, biology, planetary science

role of astronomy

reason what is going on in the night sky, figure out humanity’s place in the universe

is the universe a rational place?

astronomy presents evidence that nature acts rationally and uniformly throughout the universe, making terrestrial observations universally applicable

are there worlds beyond the solar system?

yes, astronomy allows planetary data to apply to extrasolar planets, exoplanets

how do we define a habitable world?

has liquid water, energy, and nutrients, can sustain life for a significant period of time

geocentrism

1st scientific model of universe, earth is surrounded by celestial sphere, sun and stars are placed on the sphere moving around the earth in their own spheres

1st model is successful and unsuccessful at

explaining most astrophenomenon, except planets

what does the first model assume?

earth centered, circular orbits, constant/uniform speeds

about how long is the geocentric model accepted for?

1500 years

heliocentrism

if the smaller moon orbits earth, then smaller earth likely orbits the sun. indicated as correct theory by absence of parallax. simpler heliocentric model produced by Aristorchus of Samus

who/what movement revived heliocentricity?

Copernicus, Copernican Revolution

who helped prove heliocentricity and how?

Brahe observed planetary positions, Kepler used Brahe’s data and discovered heliocentric model worked best

What prevented heliocentrism from being quickly accepted?

proponents could not explain why relative positions of stars seemed to remain the same despite Earth’s changing viewpoints as it orbits the sun (parallax?)

pros of geocentrism

successful at explaining everything except planets

cons of geocentrism

planets undergo retrograde motion, which isn’t reflected in the geocentric model

cons of heliocentrism

needs to be explained, difficult to prove as planets undergo retrograde motion, which is not simple

parallax and how it works

the apparent shift in an object’s position when viewed from different angles or positions

Kepler’s Laws (3 laws of planetary motion)

1) planets orbit in ellipses, not circles

2) planet orbital speeds vary

3) larger orbits have slower speeds and therefore longer orbital periods

aphelion

the point in an orbiting body's path when it is farthest from the sun

perihelion

the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun

light speed

distance light will cover in 1 year

lookback time

The time taken for light from a distant object to reach the Earth

atomic number

number of protons in an atoms nucleus

mass number

the total number of protons and neutrons in an atomic nucleus (equal to atomic mass)

element

atoms with the same number of p+

isotope

same number of p+ but different number of n

ion

atom with non zero net charge (gains or loses electrons)

molecule

two or more atoms bonded together

compound

molecule made from atoms of multiple different elements

energy=

mass x speed of light squared

three types of energy: (+ bonus)

kinetic, radiative, potential (and thermal)

kinetic energy

energy of motion

radiative energy

energy carried by “light”

potential energy

stored energy that can become one of the other kinds

thermal energy

kinetic energy of the particles within the matter

light

type of radiative energy called an electromagnetic wave

radiation

energy that moves from one place to another in a form that can be described as waves or particles

frequency

how many waves would pass through an object per second, frequency and wavelength are used to describe electromagnetic waves

three types of spectra

continuous/continuum, absorption, emission

how a continuous spectrum is produced

directly observe a hot, dense object emitting all wavelengths of light

how an absorption spectrum is produced

observe a hot object through a cooler object, emitting specific wavelengths of light

how an emission spectrum is produced

observe a cool object directly, light from a continuous source passes through a cooler gas, causing certain wavelengths to be absorbed by the gas atoms, leaving dark lines in the spectrum

what can spectral features tell us?

the element and its temperature and density (hotter objects give off shorter wavelengths at peak but are overall more intense

characteristics of a planet

orbit around a star (not another planet), be large enough gravity has forced into a spherical shape, cleared setting of debris

characteristics of an asteroid

small, rocky objects that orbit the Sun elliptically

characteristics of a meteor

visible streaks of light that occur when meteoroids burn up as they enter Earth's atmosphere, many contain iron or nickel (a meteoroid is a small piece of an asteroid or comet, and a meteorite is a fragment of a meteoroid that survives its journey and lands on Earth)

How is the universe “moving?”

dark energy is causing universe to expand, “observable universe” possible expanding at light speed

How do stellar lifetimes change vs stellar mass?

A star's lifetime is inversely proportional to its mass, meaning that more massive stars have shorter lifespans

3 rock types

igneous, sedimentary, metamorphic

igneous

solidified lava

sedimentary

compressed silt

metamorphic

things that have changed into something else based on heat and pressure

how can rocks change types?

the rock cycle, driven by heat, pressure, and tectonic activity

radiometric dating

radioactive parents try to decay themselves down into stable daughters, decay rates are known for many isotopes

half-life

time for half of parent to decay into daughter

age of the oldest intact earth rocks

4.02 Gyr (earth’s crust has been formed by this time)

age of the oldest meteorites, also considered the age of the solar system

4.57 Gyr

age of oldest earth rock fragments and what they are

4.38 Gyr old zircon crystals

characteristics of the Hadean Earth

constant volcanic eruptions, Earth’s crust being opened and re-opened, atmosphere arises from volcanic out-gassing of trapped gas, surface undergoing bombardment by leftover planetesimals

atmosphere of the Hadean Earth

many of the gases released from eruptions are greenhouse gases, and Earth’s atmosphere allows it to hold onto heat and provides surface pressure, allowing for liquids to exist, atmosphere starts to build up and water vapor condenses and rains down to the surface, filling the lakes and oceans

gases released from eruptions during Hadean Earth

H20, CO2, N2, H2S, SO2

surface of the earth was constantly changing, being reshaped by____, driven by _____

volcanism, plate tectonics, erosion, driven by the planet’s internal heat

relative ages of regions such as continents vs ocean floor

continental crust (granite) is much older than the “young” material of the seafloor crust (igneous basalt)

how the magnetic field is made

the rotating, electrically-conducting, convecting liquid outer core of Earth generates magnetic field (powered by solidification of planet’s liquid iron core, creating powerful electric currents that extend 1000s, of miles into space

what does the magnetic field do for us and the planet?

forms a protective barrier, protecting the atmosphere from erosion by solar wind particles, and the surface against bombardment by high energy particles

Solar wind stripping

the process by which the sun's solar wind removes gas from a planet's atmosphere, earth doesn’t experience solar wind stripping due to our strong magnetic field, which deflects most of the sun’s charged particles (northern lights are charged particles hitting earth’s magnetic field)

Different lunar surface regions and what they tell us

-highlands= lighter colored, heavily cratered, older than maria

-maria= dark-colored areas are impact basins that were filled with lava, lower in altitude, younger, have fewer craters

original heat sources

gravitational energy, radioactivity, impacts (impart extra energy to Earth)

ongoing heat sources

radioactivity, good insulation (residual heat drives geological activity)

thermal escape

gas molecules become too hot to be held onto by the planet's gravitational pull, causing them to escape into the vacuum of space— ^ temperatures, ^ evaporation, ^ precipitation, v CO2 in atmosphere, v greenhouse effect, v temperatures

how does the Earth keep its atmosphere?

the Earth keeps its atmosphere due to the force of gravity, which pulls the gasses that comprise the earths atmosphere toward the planet’s surface, more planet’s mass>stronger gravity, atmospheric pressure

does the earth experience thermal escape? why or why not?

yes, thermal escape helps earth to maintain a stable temperature. when temperatures increase too much, evaporation increases, precipitation increases, more CO2 is removed from the atmosphere, the greenhouse effect weakens, and temperatures drop