BGSU . Modern Astronomy . ASTR 2010 . Exam 1

Biggest to smallest:

. one thousand

. one trillion

. one million

. one billion

. one trillion

. one billion

. one million

. one thousand

How do you say:

345,000,000,000

three hundred forty-five billion

definition:

meter

standard metric unit of length

meter distance ... biggest to smallest:

. nanometer

. kilometer

. gigameter

. centimeter

. gigameter

. kilometer

. centimeter

. nanometer

scientific notation:

nanometer

10^-9

scientific notation:

centimeter

10^-2

scientific notation:

kilometer

10^3

scientific notation:

gigameter

10^9

true or false:

metric prefixes can be used with any unit

true

metric prefixes ... shortest to longest length of time

. 1 yr

. 1 Gyr

. 1 Kyr

. 1 Myr

. 1 yr

. 1 Kyr

. 1 Myr

. 1 Gyr

scientific notation:

630,000,000,000

6.3 x 10^11

which is the smallest number:

... 5.1 x 10^2

... 7.2 x 10^-2

... 8.5 x 10^0

... 1.7 x 10^5

7.2 x 10^-2

scientific notation:

how many meters in 700nm?

7 x 10^-7 m

... 1 nm = 10^-9

... 700nm = 700 x 10^-9

scientific notation:

1.3 x 10^10

thirteen billion

solve:

4.0 x 10^12 / 3.0 x 10^4

1.3 x 10^8

solve:

2 x 10^8m / 5 x 10^3s

4 x 10^4 m/s

solve:

3.26 x 10^24m / 5.81 x 10^6m

5.6 x 10^17

m's cancel out

solve:

4.0 x 10^30 kg + 2.1 x 10^24 kg

4.0 x 10^30 kg

solve:

3.86 (4.57 x 10^16) / 8.71 x 10^8

2.03 x 10^8

solve:

x = 12

a = 3

x / a = ?

4

solve:

c = 2.9979 x 10^8

y = 3.21 x 10^-7

c / y = ?

9.34 x 10 ^14

what is the relationship between distance (d), time (t), and velocity (v)?

hint: ? = ??

d = vt

solve:

distance . 120mi

velocity . 60 mph

time . ?

hint: d = vt

120 = 60t

t = 2

2 hours

solve:

distance . 120mi

velocity . 45 mph

time . ?

hint: d = vt

120 = 45t

t = 2.7

2.7 hours

pressure of a gas (P) depends on _ and _.

density (p) and temperature (T)

what is k in:

P = pkT

constant that allows us to choose what units we want to use for pressure, density, and temperature

solve:

. temperature (T) of gas increases by factor of 10

. density (p) does not change

what happens to pressure (P)?

increases by a factor of 10

solve:

. temperature (T) of gas increases by factor of 10

. density (p) decreases by factor of 5

what happens to pressure (P)?

doubles

(increases by a factor of 2)

solve:

. if d = vt

. if v = Hd

. v > 0

. d > 0

solve for t in terms of H

replace (d) in second relationship with he first

v = Hvt

cancel out v

1 = Ht

divide by H

1/H = t

t = 1/H

The solar system is mostly _.

empty space

No star has ever crashed into our Sun because _.

unlikely to happen in lifetime of Sun

What is science?

self-correcting

scientists are always retesting established ideas

numbers larger than ~10,000 are _.

incomprehensible to the human mind

constellations

arbitrary patterns of stars

the color of a star is related to _.

the star's surface temperature

1 light year =

that distance that light travels in one year

yellow light

. wavelength = 500nm

. frequency = ?

hint: v = c/y

. y = wavelength

. c = speed of light

. v = frequency

v = c/y

substitute

(2.9979 x 10^8 m/s) / (5 x 10^-7 m)

cancel m

(2.9979 x 10^8 s) / (5 x 10^-7)

*calculate)

6 x 10^14 1/s

how far is the nearest star?

_ ly

4.3 ly

solve:

. spacecraft travels at 0.1 the speed of light

. nearest star 4.3 ly away

how long would it take to travel to the nearest star?

light travels 1 ly in one year

4.3 years to travel 4.3 ly

spacecraft travels 10x slower than light

0.1

takes ten years longer to travel

4.3 x 10

answer

43 years

what is the brightest star

Sirius

How far is Sirius (the brightest star)?

_ ly

8.6 ly

solve:

. Sirius is the brightest star

. Sirius is 8.6 ly away

. (hypothetical) radio message is sent to base on a planet orbiting Sirius

. astronaut on said planet takes a day to read message and send a reply

how long would it be from the time the message was sent until we received the reply?

radio waves travel the speed of light through space

calculate ly --> yr

8.6 lys = 8.6 yrs

calculate to and from base planet

8.6 + 8.6 = 17.2

answer

17.2 years

Radio is a form of _

light

Is radiation dangerous to humans?

Why?

No

humans give of radiation

only high energy electromagnetic radiation and high energy particle radiation are dangerous to humans

(ultraviolet, x-rays, gamma rays, nuclear)

what do the number of protons in an atom's nucleus determine?

chemical element

how do electrons in an atom's electron cloud exist?

exists at discrete distances from the nucleus of the atom

how many times more energy does 400nm violet photon have than a 600nm yellow-orange photon?

hint: E(phot) = hc / y

set up ratio

(E 400nm / E 600nm) = (hc/400nm)/(hc/600nm)

cancel hc

(E 400nm / E 600nm) = (400nm)/(600nm)

confused?

600nm / 400nm

cancel nm

600 / 400 = 1.5

answer

1.5 times

draw energy-level diagram for an atom that has only 4 possible electron orbits

How many absorption lines of different wavelength could this atom make?

6

draw energy-level diagram for an atom that is fully ionized

How many absorption lines of different wavelength could this atom make?

0

fully ionized means all electrons have been removed ... no electrons to absorb any photons

hottest to coldest temperature

. 0 K

. 0 F

. 0 C

Why?

. 0 F

. 0 C

. 0 K

0 K is absolute 0 ... all heat energy has been removed

. human body temp is 98.6 F = 310 K

calculate wavelength of light at which humans radiate the most light

hint: Wein's Law

law

y(max) = b / T

. y(max) = wavelength peak

. b = constant of proportionality

. T = absolute temperature

set up

y(max) = (2.9 x 10^6 nmK) / (T)

sub T

y(max) = (2.9 x 10^6 nmK) / (310 K)

cancel K

y(max) = (2.9 x 10^6 nm) / (310)

answer

9400 nm

why can't humans see light radiating from ourselves?

the wavelength of the light is too long to be visible

If we see an emission line spectrum coming from an object in space, we know it is composed of a _,_ _ _.

hint: Kirkoff's Law

hot, low density gas

a normal, incandescent light bulb emits light because _.

the filament inside the bulb is heated until it radiates a significant amount of visible light

a neon light emits light because _.

the electrons in the gas inside the bulb are excited into upper orbits, and then fall back down emitting an emission line spectra

The Doppler effect allows us to measure the __ of any object in the Universe that is bright enough for us to measure its spectrum

radial velocity

If we observe an emission line in a laboratory and measure its wavelength to be 400 nm, and then we see the same line in a star but it is at 404 nm, this shows us that the _____.

star's spectrum is "red shifted"

the star is moving away from us

extra info

. shifted by the radial velocity of the star

. redshift because the observed wavelength is longer than the rest wavelength --> shifted toward red end of spectrum

How fast is the star moving?

. emission line wavelength = 400nm

. star wavelength = 404

determine Δ λ

Δ λ = 404 nm - 400 nm

= 4 nm

convert to λem

λem = 400nm

sub in v -- c = speed of light

v = c(Δλ / λ)

sub with numbers

c (4 nm / 400 nm)

= c (0.01)

convert c

c(0.01)

= 300,000 km/sec (0.01)

= 3,000 km/sec

answer

3,000 km/sec

The sun is ~_ times the size of the earth

100

why does the sun not collapse under its own weight?

its held up by gas pressure

which part of the Sun looks like its surface in a visible light photograph?

the photosphere

Most of the surface features seen on the Sun are caused by _.

the Sun's magnetic field

Solar flares are dangerous because

they can cause problems on Earth

depth perception

. based on parallax

. uses distance between two eyes as baseline to judge distances out to about 30 feet

In astronomy, we measure the distances to stars using stellar parallax and _____ as our baseline.

distance between Earth and Sun

The farthest distance we can measure using stellar parallax is determined by _____.

the smallest angle we can measure

the smaller the parallax angle the further away the star is

Parallax of star = 0.15 arc seconds

star distance = ?

6.7 pc

math

dpc = 1 / Parcsec

1 / Parcsec = 1 /0.15arcsec

1 / 0.15arcsec = 6.7 pc

to measure velocity of star _, _, and _ need to be determined

. radial velocity

. proper motion

. distance

definition:

space velocity

. star velocity through space

. sum of radial velocity + tangential velocity

Doppler shift determines _ _

radial velocity

what does it mean if two stars have the same brightness as seen from Earth

we don't know

the brightness of a star depends on 2 things

the amount of energy it produces per second (AKA luminosity)

how far away it is

what is luminosity determined by?

. star surface

. temperature and radius

2 stars radiate the same amount of light per second

one star is 10 times further away

will they look different?

yes

the closer star will be 100 times brighter

inverse square law of brightness

B ~ 1/d^2

we see 2 stars

one has a 10th magnitude

one has a 5th magnitude

which is brighter?

5th magnitude is 100 times brighter than 10th magnitude

a difference of 5 magnitudes is always a factor of _.

100

luminosity equation

L = 4 π R^2 σ T^4

hottest to coldest spectral type of star

. K3 I

. G2 V

. A1 III

. M5 V

. A1 III

. G2 V

. K3 I

. M5 V

smallest to largest radius of spectral type of star

. K3 I

. G2 V

. A1 III

. M5 V

. M5 V

. G2 V

. A1 III

. K3 I

weakest to strongest force

. electromagnetic force

. strong force

. gravitational force

. weak force

. weak / strong

. electromagnetic

. gravitational

why were most of Aristotle's idea incorrect?

he used no experimentation to support or refute his ideas

why were Aristotle's ideas correct for so long (until proven)

western culture Dark Ages

. ideas preserved by christian monks

. entangled in theological teaching

galileo's inclined plane experiments proved that...

all objects fall at the same rate regardless of mass

what Law does this fit?

once a spacecraft is up to speed no more fuel is required to keep it moving

Newton's first law of Motion

What law does this fit?

if an object is not moving it will sit un moving unless / until something exerts force on it

Newton's first law of Motion

where does the equation come from?

F=ma

Newton's Second Law

solve:

. 2 masses

. 1 mass is 5 times bigger than the other

. what happens when both are pushed with the same amount

the lower mass object will accelerate 5 times as much as the higher mass object

What law supports the statement:

lighter things require less force to accelerate than heavier things

Newton's second law

F=ma

What is Newton's third law of motion demonstrated by?

the reveal of a gun when it fires a bullet

What realization did Newton have when he discovered gravity?

the same force that holds us to the surface of the Earth also attracts the Moon toward the center of the Earth

1000

. name

. abbreviation

kilo

k

1,000,000

. name

. abbreviation

mega

M

1,000,000,000

. name

. abbreviation

giga

G

AU

. name

. 1 AU = _ mi

Astronomical Unit

1 AU = 93 million miles

ly

. name

. 1 ly = _ mi

light year

1 ly = 5.9 trillion miles

definition:

solar system

elements bound together by mutual gravity

. stars

. planets

. satellites

. asteroids

. comets

. meteoroids

. dust

definition:

galaxy

elements bound together by mutual gravity

10^7 - 10^12 group of...

. stars

. gas

. dust

definition:

universe

everything

. galaxies

. stars

. planets

. light

. energy

everything science can study

how many constellations?

88

language of constellations

Babylonian / greek