Lab_Sun_solar_rotation
docx
keyboard_arrow_up
School
Montgomery College *
*We aren’t endorsed by this school
Course
101
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
Pages
6
Uploaded by bethelyared
MONTGOMERY COLLEGE – ROCKVILLE
ASTRONOMY 101 ASTR101
[Rearranged as a Word Document by Emmanuel D. Smith]
Laboratory 7 - The Period of
Rotation of the Sun
Name:
The rotation period of an object is the time it takes for it to spin on its axis once. On
Earth we know this to be close to 24 hours. In this lab you will measure the rotation rate
of the Sun at different latitudes.
The first reliable observation of the Sun’s rotation was made in 1613 by Galileo Galilei
who watched the motion of sunspots across the solar disk over the course of several
days.
Sunspots are dark, cooler areas on the Sun’s surface that indicate areas of strong
magnetic activity. They appear dark only because they are not as hot or bright as the
area surrounding them. They can last for just hours to several months.
They usually appear in groups and
they can grow to many times the
size of Earth.
It was not until the 1860’s that the
Sun’s differential rotation was
observed: the Sun, being a gaseous
body, does not rotate as a solid
body. Instead, its rotation rate varies
with latitude. In this lab we will
observe and track sunspots across
the Sun using real images from
SOHO (Solar and Heliospheric
Observatory), a project of
international cooperation between
ESA and NASA. From these high
resolution images of the Sun we will
determine the rate at which sunspots, and thus the photosphere of the Sun, rotate. We
will do this by measuring the longitude of each sunspot as the Sun’s rotation carries it
across the face of the Sun.
1
ASTR101
L
ABORATORY
7
Examine the images of the sunspots on the Sun’s surface and how they change in a
couple of days (Images from NASA & ESA SOHO spacecraft file Images_Sun.pdf). We
will make measurements for the four A, B, C, and D sunspots marked on the images.
Record in the table for each sunspot the longitude at each different date.
2
ASTR101
L
ABORATORY
7
Sunspot A
Sunspot B
Date
Longitude
(degrees)
Date
Longitud
e
(degrees
)
June 22
-59
June 22
-
June 23
-45
June 23
-62
June 24
-32
June 24
-50
June 25
-17
June 25
-38
June 26
-11
June 26
-28
June 27
7
June 27
-11
June 28
24
June 28
5
June 29
34
June 29
17
June 30
44
June 30
27
July 1
61
July 1
43
July 2
74
July 2
58
July 3
-
July 3
73
Sunspot C
Sunspot D
Date
Longitude
(degrees)
Date
Longitude
(degrees)
June 22
-59
June 22
2
June 23
-46
June 23
13
June 24
-34
June 24
25
June 25
-18
June 25
25
June 26
-12
June 26
-
June 27
4
June 27
-
June 28
18
June 28
-
June 29
31
June 29
-
June 30
40
June 30
-
July 1
57
July 1
-
July 2
72
July 2
-
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
ASTR101
L
ABORATORY
7
July 3
-
July 3
-
4
ASTR101
L
ABORATORY
7
In the next table record the first and last date you see each sunspot and also the
corresponding longitude and latitude.
Sunspot
Latitude
Initial
Date
Initial
Long.
Final
Date
Final
Long.
Long. Motion
(degrees/day)
Long. Motion
+1degree/day
Period
of
Rotation
(days)
A
-15
June
22
-59
July 2
74
13.3
14.3
25.5
B
13
June
23
-62
July 3
73
13.5
14.5
25.2
C
18
June
22
-59
July 2
72
13.1
14.1
25.9
D
-40
June
22
2
June
26
25
7.7
8.7
41.9
To get the average degrees of longitude the sunspot moved per day, subtract the first
from the last to determine the total degrees of change. (Note that you have to consider
the sign of the longitude. For example, if the last longitude measured was +30 and the
first was -15 then: total degrees of change = +30 - (-15) = 45 degrees). Then divide this
number by the number of days it was observed. Because Earth is moving around the
Sun about 1 degree per day (it takes about 365 days to circle the Sun in a year), in the
same direction the Sun is spinning, you need to add one degree per day to compensate
for this movement.
The period of rotation is the time it takes for the Sun to make a complete rotation. Since
there are 360 degrees in a full rotation, if we divide 360 by the daily longitude motion
(degrees/day) +1, we will get the Sidereal Period (how long does it take for the sun to
make a full rotation with respect to the stars). Calculate the Sidereal Period for the
different latitudes. (Show all your calculations)
5
ASTR101
L
ABORATORY
7
1)
The Sun rotates in the same direction as the Earth does. What direction is that as
you face an image of the Sun, left to right or right to left?
Left to Right
2)
Do some sunspots change in size or/and shape as they move around the Sun?
The sunspots do seem to change in size and shape as they move around the Sun. As
the sunspots move towards the right they seem to get smaller in size and the shaping
does change a little bit as well along the way.
3)
Does Earth period of rotation vary between polar and equatorial regions? Why do
you think the Sun has differential rotation and Earth does not?
Earths period of rotation does not vary between polar and equatorial regions. This is
because Earth rotates faster at the Equator than it would at the polar locations.
The sun has differential rotation because it is a ball of gas/plasma which means it does
not rotate the way other solid planets do.
4)
Now consider the latitudes of your sunspots and their periods. Which sunspots
move faster, the ones with lower latitude (closer to the equator) of the ones with
higher latitude (closer to the poles)?
Based on your results, which part of the
Sun appears to rotate fastest?
According to my data the sunspots in the lower in latitude (closer to the
equator) move the fastest. This means the equatorial region of the sun
rotates the fastest.
6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help