astrophysics and paper 3

what characteristic makes an image virtual

the rays focus on the same side of the lens that they enter

define a black hole

an object with escape velocity greater then the speed of light

what are some features of a refracting telescope (positive and negatives)

chromatic abberation, hard to make the lenses, magnification proportional to focus length

what are some features of a reflecting telescope (positive and negatives)

less distortion as mirrors can be supported better, spherical abberation

what is a CCD - what does it do?

a small chip divided into light sensitive pixels, when photons hit the face, they trigger the photoelectric effect, causing electrons to be emitted creating a digital signal

Why are CCD’s better then the human eye at detecting planets

they have greater quantum efficiency and resolution

what is quantum efficiency?

the ratio of incident to detected photons

what is collecting power proportional to

the diameter squared

the one formula for intensity and magnitude

i2/i1 = 2.51^m1-m2

In the acronym OBAFGKM, what are the temperature ranges for each letter

50-25 25-11 11-7.5 7.5-6 6-5 5-3.5

In the acronym OBAFGKM, what are the colours for each letter

blue blue blue-white white yellow-white orange red

on the HR diagram, what goes on the vertical axis (give name of it and numbers from bottom to top)

apparent magnitude 15 -10

on the HR diagram, what goes on the horizontal axis (give name of it and numbers from start to finish)

temperature 50000 2500

give the formation of a star

1. an interstellar dust cloud collapses under gravity

2. the gpe decreases and kinetic energy increases increasing temperature

3. at 10 million kelvin, hydrogen nuclei fuse into helium

4. radiation and gas pressure cause gravity

give the life of a star like the sun

protostar/gas cloud, main sequence, red giant, white dwarf

whats one big characteristic of a neutron star

very high density very small size

state hubbles law in words

recession speed of a galaxy is proportional to its distance from earth

whats an astronomical unit

the distance from the earth to the sun

whats a parsec

the distance when 1 astronomical unit subtends a parallax angle of 1 arcsecond

define absolute magnitude

the apparent magnitude an object would have if viewed from 10 parsecs away from earth

define apparent magnitude

a stars brightness as measured from earth, it depends on the luminosity of the star and how far away it is from earth

state an advantage of a large diameter telescope

minimum angular resolution

state the rayleigh criterion

the minimum angle required for the maximum of one diffraction pattern to coincide with the first minimum of the other, allowing for two sources to be just resolved.

whats spherical abberation

when two rays dont converge onto a single point

whats chromatic abberation

when different colours are refracted by different amounts

how do you take an uncertainty for a measurement

you take + or - the smallest unit in the measurement

how do you calculate uncertainty of a gradient

(gradient of best line - gradient of worst line)/best gradient (gradient of worst line could be steepest or shallowest gradient)

when taking the log of a data value, what does the number of sigificant figures of the data value represent

the number of decimal places in the logged values answer

what does this diagram represent

the parsec

when do gamma ray bursts occur and what forms soon after

when a big star runs out of fuel and collapses under gravity forming a black hole and a neutron star

what is meant by normal adjustment on an astronomical telescope

the image is formed at infinity

what combo gives largest angular magnification (eg. large converging objective lens, small diverging eyepiece lens etc)

large converging objective lens and small converging eyepiece lens

give a quick definition of the transit method

detects a dip in a stars brightness as a planet passes infront of it

give a quick definition of the radial velocity method

as a planet orbits, it moves towards and away from the observer, causing a doppler shift

what does this graph represent

a supernova

what does this graph represent

a transit light curve

what does this graph represent

a black body radiation curve

why are some telescopes located in space

because the wavelengths it aims to detect are smaller then visible light and so are absorbed by the ozone layer

how does a quasar form

when a giant black hole is feeding on nearby matter

what is collecting power proportional to

area

give some benefits and negatives of a reflecting telescope

spherical abberation, shorter so easier to transport

give some benefits and negatives of a refracting telescope

chromatic abberation, magnification proportional to focal length

define a standared candle

a distant object with known absolute magnitude

give percentage of quantum efficiency of a CCD and an eye

80 percent, 1 percent

define a supernova

an object that produces a rapid increase in brightness

whats dangerous about supernovas

they emit gamma ray bursts

how can i use a mirror to avoid parallax errors (errors caused by the angle your viewing something like a needle)

move position until needle is aligned with its position in the mirror

why are quasars easily discovered

they are high power radio emitters