Ch 2 The Night Sky Flashcards
Magnitude
what is the 0.0 point
what is the max magnitude of the sun?
Of neptune?
Measures brightness and works on a logarithmic scale.
- 0= Vega
- 26.7 - 6
if something is 100x dimmer than vega, what is its magnitude?
approx 5
What magnitude can humans see with a naked eye?
With a telescope?
m= 6.5 ( so we can see approx <10k stars) m= 31
What planets are visible to the naked eye?
Mercury, venus, mars, jupiter, saturn.
(T/F) The scale of apparent visual magnitudes extends into negative numbers to represent the faintest objects in the sky.
False.
neg numbers = brighter objects
How many constellations are there?
88
Are stars too far away for depth perception
yes.
Hence why the ancient people called it the celestial sphere.
TRUE/FALSE FOR DA SPHERE OF CELESTIAL
Does earth’s northpole point towards the celestial north pole?
The earth’s equator expands out to the celestial equator
The sun follows a uniform pattern on the celestial sphere.
Dumb happenstance, but yes.
true af
FALSE. It does not
What are the tropics?
The tropics are the point at which the sun’s path is the most north and most south. ( cancer and Capricorn)
The stars in a constellation are named based on their apparent magnitudes. list top three brightest
alpha
beta
gamma
What is the alpha in orion? The beta?
A= betelgeuse
B=Rigel
What is an asterism?
Well known shapes that are not actually constellations (ex big dipper)
How many zodiac constellations are there?
13.
Ophiuchus
What determines what month a zodiac constellation is associated with?
The time the constellation is behind the sun.
Why is winter colder in the northern hemisphere?
Because of earth’s tilted axis.
Define solar day
note, earth moves 1 degree a day.
The time it takes forthe sun to retur to the same position overhead
24h=361 degrees
Define Sidereal Day
The time it takes for the stars to return to the same position in the sky;
23hr 56 min = 360 degrees.
T/F the sun follows a uniform path
T——-FALSE!!!!
Changes over the seasons due to the tilt of the earth’s axis.
How much is earth’s axis tilted?
23.5 degrees
Draw axial tilt diagram. include: ecliptic, celestial equator celestial north and south pole ecliptic axis
see diagram
see desktop
When do equinoxes occur?
When the axial tilt is perpendicular to the line connecting earth to the sun
If earth rotated about an axis perpendicular to its orbit, what would we fail to experience?
365 days a year
Which axes points towards the celestial poles?
earth’s rotational axis
What would happen if the axial tilt of earth were larger than it currently is?
The seasons would be more extreme
If earth rotated twice as fast as it currently does, but it’s orbital period was the same, which of the following would occur?
a. The solar day would be shorter than the sidereal
b. Everything would remain unchanged
c. The night would be half as long
d. The sidereal day would be twice as long
e. The solar year would be twice as long
The night would be half as long.
If the sun rises in Aquarius in the morning, where will it set that night?
Aquarius.
T/F
Stars at the celestial equator take the same amount of time to rotate about the earth as stars closer to the celestial poles.
True.
What is the primary scientific reason for identifying constellations?
To provide a relational map of the night sky
What time of year does the vernal equinox occur in if you live in north america?
Spring! In march.
T/F science can be used to prove the earth is round.
FALSE.
Daddy travy taught you better.
The zodiac constellations & corresponding dates are: Jan 21 - Capricorn, Feb 21 - Aquarius, Mar 21 - Pisces, Apr 21 - Aries, May 21 - Taurus, June 21 - Gemini, July 21 - Cancer, Aug 21 - Leo, Sept 21 - Virgo, Oct 21 - Libra, Nov 21 - Scorpio, Dec 21 - Sagittarius. At midnight, July 21, which constellations would be prominent in the night sky?
Sagittarius, Capricorn, Aquarius
The zodiac constellations & corresponding dates are: Jan 21 - Capricorn, Feb 21 - Aquarius, Mar 21 - Pisces, Apr 21 - Aries, May 21 - Taurus, June 21 - Gemini, July 21 - Cancer, Aug 21 - Leo, Sept 21 - Virgo, Oct 21 - Libra, Nov 21 - Scorpio, Dec 21 - Sagittarius. At midnight, Mar 21, which constellations would be prominent in the night sky?
Virgo, Leo, Libra.
The moon’s orbit crosses the ecliptic twice per month. (T/F)
TRUE AF BBY
Christmas occurs around the same time that the earth is furthest away from the sun.. (T/F)
FALSE MOFO
furthest away during summer.
also, the southern hemisphere being warmer has more to do with how the large bodies of water moderate the temperature than the distance from the sun at any given point.
A lunar eclipse can only occur during which lunar phase?
Fullmoon
Define Precession
what is the period of precession?
The change in earth’s rotational axis.
our precessional period is about 26 000 years
3000 years ago, polaris was not the north star
what do we call an degree in astronomy?
1/60th of a degree?
1/3600 of a degree?
hour.
arcminute
arcsecond
How many hours in 360 degrees?
how many degrees are in 1 hr?
how many many minutes are in 1 degree
360 degree= 25hr
1hr= 15degree
1 degree =4 min
What is a Zenith?
Nadir?
point directly overhead
Point directly underneath
What is one of the earliest ways to communicate the location of celestial objects?
Using azimuth (angle relative t north (latitude) ) and altitude (angle above the horizon (verticle) ). must also include your Zenith or Nadir because the earth is round.
Describe the modern mapping system.
what’s the 0.0 point?
draw a picture.
Vernal equinox= 0.0, which is at the interscetion of our celestial equator and the ecliptic. Right ascension (0h to 24 h). measures east/west Declination; +90 to -90 degrees. Measures north south.
Parallax*. What is it?
how far can we measure?
What is the highest precision angle?
When we use triangulation to measure distances of objects in our sky, the parallax is the angular distance between the two positions. We need to measure the angle positons very accurately for this method to work. It’s called paralax when we use the diameter of earth’s orbit to
using just the diameter of the earth, we can measure approx .28 ly.
highest precision angle= .001”
When is using triangulation to find a bodies distance from us a good idea?
why is there a limit?
What, other than than example above, can we use triangulation for?
When the body is within our solar system
The larger the R, the smaller the parallax angle. outside our solar system, the parallax is too small to measure accurately.
to measure the size of objects within a range.
We measure the parallax of two stars. One of them has twice the
parallax of the other. How do their distances compare?
distance is halved?*
How long is a sidereal month?
sidereal orbital period of the moon
27.3 days.
related to time it takes the moon to orbit the earth once.
Why is the orbital period of the moon different from the period of its phases?
Because the moon is orbiting the earth, which orbits the sun.
How long does it take the moon to complete all of it’s phase cycles?
29.5 days
draw the moon phases.
refer to slide 47
Lunar Eclipse. what happens?
The moon passes behind earth, eath’s shadow is cast on the moon-> moon looks reddish.
What is the reddish colour of the lunar eclipse caused by?
Earth’s atmosphere acts as a lens and causes the reddish colour.
Draw a diagram of a lunar eclipse. Include umbra and penumbra
sees slide 50
Do earth’s and the moon’s orbital tilt line up?
No. only at certain times.
What are favourable eclipse conditions?
Moon must be full.
what allows solar eclipses to occur?
The angular size of the sun is approx the same size as the moon
what part of the sun can be seen during a solar eclipse?
The corona (with the right equipment
During a solar eclipse, what’s the difference between being in the area in the penumbra versus the umbra?
Penumrba= partial eclipse, can't really tell that anything is happening. Umbra= full eclipse
Does a solar or lunar eclipse last longer?
Lunar
define rocky
define ices
rocky= solid at room temperature (metals and nonmetals)
ice= solid matter that would be liquid or gas at room temperature. Not just water in astr.
Why are they called Gas Giants?
Because of their thick atmospheres
