ast1002 help me

Asteroids

Composed of rocks and metals

> 300m

Most are in the ____ belt

Comets

Dirty Snowballs

A few tens of kilometers

Kuiper belt and Oort Cloud

Asteroid Density

like grains of sand separated by kilometers

DART

Asteroid Deflection Mission

Kirkwood Gaps

orbital resonances of asteroids from Jupiter

Comet tails

Always point away from the sun

Plasma Comet Tails

Straight, affected by solar wind

Dust comet tails

Curved, caused by solar radiation pressure

Reason plasma tails are straight

Solar wind pushes harder than radiation

Shoemaker Levy 9

Comet that was discovered shortly before it broke apart and crashed into Jupiter

Meteroid

Approaching rocks in orbit

Meteors

rocks burning up in the atmosphere

Meteorites

Rocks that make it to the ground

Methods for discovering extrasolar planets

Direct Imaging

Transit

Radial Velocity

Direct Imaging

a technique that captures actual images and spectra of planets orbiting other stars

Advantages of Direct Imaging

The only method that allows direct study of the planets themselves

Limitations of Direct imaging

Requires large telescopes and some means of blocking light from star planet is orbiting

Transit

Infer planet’s existence from slight changes in star’s brightness as planets passes in front of (or behind) the star.

Advantages of Transit

• Allows many stars to be observed at once

• Can detect very small planets

• Is feasible with small telescopes

• Can provide some atmospheric data in cases of measurable eclipsesThis method enables the detection of exoplanets as they pass in front of their host stars, causing a temporary dimming that can be measured.

Limitations of Transit

• Is possible only for plants with edge-on orbits as viewd from earth

  • For small planets, requires sensitivity possible only from a space observatory

Radial Velocity/Doppler Method

Infer the planet’s existence from the star’s motion toward/away from us as revealed by Doppler shifts in its spectrum

Advantages of doppler method

• is possible from ground-based telescopes

  • Detects planets in all orbit orientations except face-on

Limitations of Doppler Method

• is biased toward finding massive planets with close-in orbits

• Underestimates star’s true motion excerpt when system is viewed edge-on

• Requires stellar spectra, which means large telescopes and long observation times

The Habitable Zone

Temperature right of liquid water, larger/hotter stars = bigger zone

Hot Jupiters

The first type of exoplanets to be discovered

• Orbits close to the host star

• Larger Radius- blocking a larger fraction of the light makes a deeper transit

• Larger Mass- heavier planet tugs more on the star, shifting the lines more

• Shorter period- closer to the star repeats the patterns more, making it more likely to notice

Vicous Torques

The orbiting planet nudges gas and particles in the disk causing material to bunch up. These dense regions in turn tug on the planet, causing it to migrate inward

Flyby Kicks

New evidence indicates that the outer planets may have migrated to their present orbits

Plasma

A fluid-like state of ions and electrons

• the sun is not on fire

Fusion`

Lighter elements fused to make heavier elements

Isotopes

a different version of the same element, meaning it has the same number of protons but a different number of neutrons.

The Proton-Proton Chain

The process of converting hydrogen to helium

How is fusion stable?

The outward push of pressure precisely balances the inward pull of gravity.

• Hydrostatic/gravitational equilibrium

Solar thermostat

The sun is constantly fighting against gravity

Core

place in the sun where fusion occurs

Radiation Zone

Energy is transported/diffused outward by photons scattering off free electrons as they slowly make their way outward

• Photons take a random walk over 100,000 years

• make the sun opaque

Convection Zone

Energy is more efficiently transported by bubbling up instead of by photons doing their random walk

Photosphere

The “surface” of the Sun (the point at which the Sun transitions from opaque to transparent)

• the blackbody we see

Photosphere Granulation

Bubbles (convection) finally making it to the surface

Sunspots

• located in the photosphere

• cooler regions of intense magnetic field

• the magnetic pressure is greather than the thermal pressurethat appear as dark spots due to lower temperatures compared to surrounding areas, often associated with solar magnetic activity.

Prominence

Hot gas following magnetic field lines in the shape of arcs

Spicule

The thin tubes or columns of gas tracing the Sun’s magnetic field line

Chromosphere

a thin layer of the Sun's atmosphere located above the photosphere and below the corona, characterized by its reddish color and solar prominences.

• the suns lore atmosphere

Fraunhofer Lines

These are the same lines used to find planets with radial velocity

Corona

The Sun’s Outer Atmosphere

• temperature rapidly increases\

• believed to be heated by magnetic waves

Differential rotation

• magnetic field lines are like rubber bands

• the variation in rotation speed of different parts of the Sun, where the equator rotates faster than the poles, affecting solar phenomena like sunspots and solar flares.

Aurora Borealis/Australis

When solar wind hits Earth’s Magnetic field

• they spiral around field lines

• move down towards poles

  • Hit atoms in atmosphere

What type of specturm does an aurora produce?

Excited atoms in the transparent gas produce emission lines

Carrington event (1859)

The largest observed geomagnetic storms

large aurorae, telegraohs failed

The 11 year solar cycle

The butterfly diagram

• the number and locations of sunspots

Stellar lifetimes

Millions to trillions of years

Luminosity

How bright a star is

The inverse square law

the intensity of light decreases with the square of the distance from the source

Magnitude Scale

A ranked Brightness Scale

• 1 is the brightess (backward scales)

  • Based on the human eye

Stellar Parallax

The apparent shift in position of a star against a distant background when observed from different points in Earth's orbit. It is used to measure the distance to nearby stars.

Parsecm (parallax arc second)

a unit of length used to measure the large distances to astronomical objects outside the Solar System

• approx. 3.26 lightyears

How do stars emit lights?

As black bodies

Bluer stars mean

higher temperatures

Redder stars mean

lower temperatures

Spectral Types

a classification system based on the temperature and chemical composition of a star's surface

Binary Star System

a system consisting of two stars that are gravitationally bound to each other, orbiting a common center of mass

Visual Binary

we see both stars

Spectroscopic Binary

We get the mass from the velocity curve but we don’t know the inclination

• measures doppler shift

Eclipsing binary

One star blocks out the light of the other

Main Sequence

When stars are fusing H to He

• Lifetime decreases and mass increases with increasing temperature and luminosity

Hydrostatic equilibrium

More mass means more pressure is needed

Clusters

Stars born from the same large gas clouds, same distance, same age

Open Cluster

located in the disk, younger, more metal, bluer

Globular Clusters

Globe-shaped, older, fewer metals, redder

Bulge

Bright central sphere

Disk

Containing spiral arms

Halo

very faint sphere containing globular clusters

Density waves

The arms and disks are blue because stars form out of compressed and collapsing gas clouds under gravity.

The galactic fountain mode

theory that hot, ionized gas blown out of the galactic disk and into the halo by superbubbles cools down and falls back into the disk`

Olbers’ Paradox

the night sky is dark

Cosmic Microwave Background

the remnant radiation from the Big Bang, observable in all directions in space, providing evidence for the universe's origin. The universe’s photosphere

Halo orbits and bulge orbits

Scrambled and spherical

Disk orbit

ordered and fairly flat but undulating up and down and in and out, like a merry-go-round

Elliptical galaxies

of galaxy characterized by their smooth, ellipsoidal or spherical shape, with little internal structure or spiral arms

• Dead galaxies with only older, red stars and little cold dust/gas

Spiral galaxies

feature a flat, disc-shaped structure with arms spiraling out from a central bulge

• bluer, younger stars

the more galaxies interact

the redder they get