1110AST-lab2
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Feb 20, 2024
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AST 1110: Planetary Astronomy
Spring 2024
Lab 2 (30 points)
Name: Jenna McCarthy
Observing from the Northern Hemisphere
Learning Goals
Measure positions of astronomical objects on the sky
Explain why some stars are circumpolar as seen from Colorado
Describe some of the astronomical events that occur in January 2024
Show your work on all math problems this semester (including today)!
Part 1: Positions on the Sky
Below is an example of the Horizon System
, a way of measuring an object’s current location on the sky using altitude
and azimuth.
Altitude
measures an object’s position above the horizon, from 0
°
at the horizon to 90
°
at zenith. Azimuth
measures an object’s position along the horizon, starting at North (
0
°
) going to 90
°
at East, 180
°
at South, 270
°
at West, and through 359
°
back around to North. We’re going to be creative and use some virtual tools to measure the position of Polaris from Colorado Springs. Go to Solar System Scope
and click start. Click in the animation
and then select Night Sky view from the menu along the left. Then click Settings (middle option on the left hand menu) and within settings, scroll down to Star Names and change to on, then scroll to Azimutal and select Grid.
Find Polaris on your screen. Each of the major grid lines represents 10 degrees. 1.
Estimate the Altitude _
40º
____ and Azimuth ___
0º
__ of Polaris on the sky. This does not need to be perfect; it is just an estimate. 2.
Find the percent error between the known Altitude of 38.8 degrees for Polaris and your Altitude (“data”). Remember that absolute values are always positive.
3.09%
=
|
(
(
40
−
38.8
)
38.8
)
|
×
100
3.
Find the percent error between the known Azimuth of 359.2 degrees and your
Azimuth (“data”). (If you used 0 degrees please enter it as 360 degrees, 1 degree becomes 361 degrees)
22.3%
=
|
(
(
360
−
359.2
)
359.2
)
|
×
100
Part 2: The Circumpolar Zone
Use this online planisphere
to answer the following questions.
4.
Click and drag on the top of the planisphere until the end of January lines up with 6 PM. Then drag late January from 6 PM to 6 AM and list four constellations on the planisphere that will set over the course of a night
in January.
Draco, Cepheus, Cassiopeia, and Ursa Minor. 5.
Click and drag on the planisphere to move late January from 6 PM to 6 AM and list four constellations on the planisphere that will rise over the course of a night
in January.
Andromeda, Aquila, Aquarius, and Pegasus. 6.
Click and drag the planisphere all the way around several times. List four constellations on the planisphere that are visible all the time. 2
Ursa Minor, Cassiopeia, Ursa Major, and Draco. 7.
Explain why some constellations are circumpolar for observers in Colorado. Some constellations are in the southern hemisphere (38º below the southern horizon) and some are in the northern hemisphere (38º of the North Pole) and we are in the northern hemisphere in Colorado. Part 3: January Night Sky for the Northern Hemisphere
Download the Sky Map for this month’s Night Sky
(northern hemisphere). Answer the following questions using the January sky map for the Northern hemisphere.
Remember that asterisms are not the same thing as constellations.
8.
What constellation is closest to zenith on this sky map?
PERSEUS
9.
What named star is closest to zenith on this sky map?
Algol
10.What constellation contains the north pole star, Polaris?
URSA MINOR
11.Why is Polaris not located at the zenith as seen from Colorado Springs?
Because Polaris is at the zenith at the North Pole. 12.List five of the brightest stars visible on this sky map (larger size indicates greater brightness): Sirius, Rigel, Vega, Capella, and Betelgeuse. 13.List five of the constellations that the Milky Way passes through this month.
Monoceros, Auriga, Perseus, Cassiopeia, and Cygnus.
3
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14.Can you find any constellations or asterisms yourself in the night sky? If so, which ones? (Not just in January, but any time of year)
Ursa Minor and Ursa Major. 15.Explain what the ecliptic represents on the sky.
It is the path of the Sun’s center on the celestial sphere as seen from Earth. 16.List any planets that are visible in the morning this month. Use the Calendar on the left side of the Sky Map. Venus, Mercury, and Mars.
17.List any planets that are visible at night this month.
Saturn and Jupiter.
18.List any planetary alignments (such as elongations or conjunctions) that happen this month.
Mercury.
19.What is the phase of the Moon today? List the date also.
01/22/2024, waxing gibbous. 20.Fill in the table below using the calendar on the left side of the Sky Map. After you have angular size in arcminutes, convert to angular size in arcseconds, remembering that 1 arcminute = 60 arcseconds. Use only the 1
st
Perigee listed.
For the Moon at Perigee
:
For the Moon at Apogee
:
Angular size (arcmin): 33.0’
Angular size (arcmin): 29.5’
Angular size (arcsec): 1,980’’
Angular size (arcsec): 1,770’’
Distance (km): 362,267 km
Distance (km): 404,909 km
4
21.For the Moon at Perigee (d is distance), determine the linear size D of the Moon (in kilometers) using the equation below. Plug in angular size in arcseconds. Show your work.
3477.5
km
=
(
1980
×
362267
)
206265
22.For the Moon at Apogee (d is distance), determine the linear size D of the Moon (in kilometers) using the equation below. Plug in angular size in arcseconds. Show your work.
3474.6
km
=
(
1770
×
404909
)
206265
23.Average together your two values for the linear size of the Moon.
3477.5 + 3474.6 = 6952.1/2 = 3476.05 km
24.The true value for the linear size of the Moon is 3474 km. Determine the percent error in your calculation for the moon.
|
(
3476.05
−
3474
¿¿¿
3474
)
|
×
100
=
0.059%
5
Image from APOD
25. Why does the angular size of a full moon vary from month to month? Because that is when the Moon is its closest to the Earth in its elliptical orbit.
26.The distance to the Andromeda Galaxy (M31) is 2.537
×
10
6
light-years and its angular size on the sky is 10,800 arcseconds. Use these numbers to determine the diameter D of Andromeda. Your answer will be in light-years. Show your work.
13.96
=
(
10800
×
(
2.537
×
10
6
))
206265
27.The accepted value for the diameter of Andromeda is 220,000 light-years. Determine the percent error in your calculated diameter for Andromeda. Show
your work.
|
(
(
D
calculated
−
220000
)
220000
)
|
×
100
=
¿
6
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28.The accepted distance to the Andromeda Galaxy has quite a bit of uncertainty. The distance can be expressed as (
2.54
±
0.11
)
×
10
6
light-years. This is an uncertainty of 110,000 light years! Why is there so much uncertainty in measuring the distance to objects outside of our galaxy?
Due to objects outside of our galaxy being light-years away, assumptions are the best form of measuring. Image from APOD
29.Explain why we are not able to see the Andromeda Galaxy this clearly from Colorado Springs. The Andromeda Galaxy can only be seen from the southern hemisphere and we are in the northern. 7