Sunspots! let us introduce ourselves…

20
Sunspots! Let us introduce ourselves…

Transcript of Sunspots! let us introduce ourselves…

Page 2: Sunspots! let us introduce ourselves…

Introductory section and preparatory phase

• Short Description: On Sun’s surface we can see sunspots. What actually

are the sunspots? Why are they black? The spots are moving, as the Sun

revolves around himself. Can we calculate the rotation period of the Sun?

Can we study the topography around the spot? Can we calculate the

temperature of the spot peaks? We will try to answer to all these

questions, by studying images freely provided by the Astronomical

Observatory of Coimbra, the National Schools Observatory and the

Faulkes Telescope Project during last month.

• Keywords: Sun, sunspots, rotation period of sun, sunspots

temperature, sunspots topography, umbra, penumbra.

• Target audience: Students studying Natural Sciences (especially

Physics and Astronomy)

• Age range: 14-18 years old

• Context: Natural Sciences School Lab, Computer School Lab, internet

connection.

• Time required: 6 hours

Page 3: Sunspots! let us introduce ourselves…

Introductory section and preparatory phase

• Technical Requirements: Internet connection, appropriate software: Salsa

J, Microsoft Office, Microsoft Windows, Computers, video projector could be

useful.

• Author’s background: Knowledge of Physics: equations of movement, simply

harmonic oscillation and thermodynamics (basics), knowledge of Astronomy

sun, sun physics (basics). Salsa J, image processing

software, internet, software related to Astronomical Observatory of Coimbra, the

National Schools Observatory and the Faulkes Telescope Projects.

• Connection with the curriculum: Strongly related with Astronomy (Second

Class of Greek High School), Physics (First, Second and Third Class of Greek

High School). Partly related with Mathematics (Trigonometry, Second Class of

Greek High School).

• Learning Objectives: Hands on learning, Inquiry based learning, connection

between Universities-Institutes and Schools, use of Open Science

Resources, learn students to cooperate and act as researchers.

• Guidance for preparation: Download images from internet (Astronomical

Observatory of Coimbra, the National Schools Observatory and the Faulkes

Telescope Project), videos about sunspots (e.g. NASA), Sun

Physics, applications for smart phones about Solar activity.

Page 4: Sunspots! let us introduce ourselves…

Pre-Experiment / Observation– Teaching Phase 1:

Questions Eliciting Activities – PROVOKE CURIOSITY

Teacher presents the following video from

NASA concerning 3 years activity of Sun:

http://www.nasa.gov/multimedia/videogallery/i

ndex.html?collection_id=13587&media_id=16

2085261 asking them about Sun.

Teacher also presents to students the

following video concerning solar sunspots:

https://www.youtube.com/watch?v=rWYpy1y-

leM asking them about sunspots.

Finally teacher asks from students to find and

collect images of Sun (like those beside) from

the Astronomical Observatory of Coimbra, the

National Schools Observatory and the

Faulkes Telescope Project

Page 5: Sunspots! let us introduce ourselves…

Pre-Experiment / Observation– Teaching Phase 1:

Questions Eliciting Activities – DEFINE QUESTIONS FROM

CURRENT KNOWLEDGE

• Does Sun rotates?

(Reference:https://www.youtube.com/watch?v=rW

Ypy1y-leM)

• How can we evidence the rotation of Sun?

(Reference:http://www.nasa.gov/multimedia/video

gallery/index.html?collection_id=13587&media_id=

162085261)

• Sun rotates as a solid sphere or

differentially? *

• Is the speed in the Equator of Sun equal

to the speed at the Poles? *

• Why Sunspots appear to be black?**

• Can we calculate the temperature at the

peaks (umbra) of the sunspots? **

**https://docs.google.com/viewer?url=http://www.odysseus-contest.eu/wp-content/uploads/contest/SUNSPOTS+ENGLISH_en.pdf

*https://docs.google.com/viewer?url=http://www.odysseus-contest.eu/wp-

content/uploads/contest/2%CE%BF+%CE%93%CE%B5%CE%BD%CE%B9%CE%BA%CF%8C+%CE%9B%CF%8D%CE%BA%C

E%B5%CE%B9%CE%BF+%CE%9A%CE%B1%CF%81%CE%B4%CE%AF%CF%84%CF%83%CE%B1%CF%82_PRWS_Odysse

us_el.doc

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Pre-Experiment / Observation– Teaching Phase 2: Active

Investigation – PROPOSE PRELIMINARY EXPLANATION OR

HYPOTHESES

• Students must gather and print a

sufficient number of Sun photos.

Then, they asked to mark the

successive positions of sunspot by help

of transparency, as shown in the

picture.

• They observe that the orbits of the

spots are nearly straight lines. Then

they must transform the linear shifts

into bow shifts.

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Pre-Experiment / Observation– Teaching Phase 2:

Active Investigation – PLAN AND CONDUCT SIMPLE

INVESTIGATION

• After recording the successive positions

of spots, students plot the entire arc of

the circle (see solar sphere) and find the

midpoint of the arc. Once they identify

the midline of the arc they measure the

distance from the edges. This distance

essentially corresponds to the radius R

of the orbit of the sunspot to the

concrete heliographic altitude.

• They calculate the distances x1 and x2 of

the initial and final position of the spot

from the middle, respectively. The angle

φ shall be given by the relationship:

φ= arcsin(x1/R) + arcsin(x2/R)

with arcsin the inverse sin.

Page 8: Sunspots! let us introduce ourselves…

Pre-Experiment / Observation– Teaching Phase 2:

Active Investigation – PLAN AND CONDUCT SIMPLE

INVESTIGATION

• As soon as students determine

the angle φ, the rotation period of

the Sun will be given by the

relationship:

T= Δt*360/φ

where Δt the time period the

sunspot required to be moved

from the initial to the final position

(in days).

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Experiment / Observation– Teaching Phase 3:

Creation – GATHER EVIDENCE FROM OBSERVATION

• Students are collecting observation data, such as those in the Table

below:Number of

solar sunspot

Recording dates Measuring datest: number of measuring

days (d)1635 18-26 Dec 2012 20-26 Dec 2012 61633 15-22 Dec 2012 15-22 Dec 2012 71634 15-23 Dec 2012 15-23 Dec 2012 81486 19-27 May 2012 19-27 May 2012 81575 19-29 Sept 2012 22-26 Sept 2012 41579 24 Sept-02 Oct 2012 27 Sept- 2 Oct 2012 5

• Then, they calculate the rotation period based on equations:

φ= arcsin(x1/R) + arcsin(x2/R) and T= Δt*360/φ as shown in Table:

Number of solar sunspot

R: orbital radius (cm)

x1 (cm) x 2 (cm)φ

(degrees )T:

Period (d)

1635 4.00 3.05 2.20 83.05 26.01

1633 4.15 4.00 1.40 94.25 26.73

1634 4.00 3.80 2.55 111.4 25.85

1486 4.00 3.15 3.05 101.6 28.34

1575 4.15 1.45 2.30 54.11 26.61

1579 4.00 2.20 2.30 68.47 26.29

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Experiment / Observation– Teaching Phase 4:

Discussion – EXPLANATION BASED ON EVIDENCE

• Students are asked to confirm or revise their initial ideas about

Sun rotation.

• They asked to calculate the heliographic latitude of each solar

sunspot as in follow Table:

Number of solar sunspot Heliographic latitude Rotational Period (1st method) (days)

1635 17,5 26,01

1633 5 26,73

1634 16 25,85

1486 26 28,34

1575 2 26,61

1579 28,5 26,29

• Then, students must try to explain the association between

heliographic latitude and rotational period.

• We help students to examine if the rotational period differences

are due to the differential movement of the Sun.

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Experiment / Observation– Teaching Phase 4:

Discussion – CONSIDER OTHER EXPLANATIONS

• Additionally students can

calculate the rotation period of

Sun assuming the spots

performing simple harmonic

oscillation. To make the method

easier to understand it is

illustrated in the figure beside.

• Essentially, we are projecting

the successive positions of

curve motion of sunspots on a

straight line.

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Experiment / Observation– Teaching Phase 4:

Discussion – CONSIDER OTHER EXPLANATIONS

• By applying the principles of

simple harmonic oscillation we

have:

x = Asin(ω t + φ)

x/A = sin(ω t + φ)

arcsin(x / A) = ω t + φ

because of ω = 2π / T finally we

have:

arcsin(x / A) = (2π / T)t + φ

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Experiment / Observation– Teaching Phase 4:

Discussion – CONSIDER OTHER EXPLANATIONS

arcsin(x / A) = (2π / T)t + φ

• Knowing every time the position x of a sunspot from the middle

of the arc and the radius of the orbit we can design the

following graph arcsin(x)=f(t), as shown in the figure:

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Post-Experiment / Observation– Teaching Phase 5:

Reflection – COMMUNICATE EXPLANATION

• Students can now

compare the two

different methods. They

can create Table with

values as beside:

Number of spot

Rotational Period (Days)

1st Method 2nd Method

1635 26.01 25,45

1633 26.73 21,16

1634 25.85 26,08

1486 28.34 29,52

1575 26.61 27,05

1579 26.29 27,02

• Furthermore, students can

plot the rotational periods

in same graph, verifying

similarities and

differences, as shown

beside:20

21

22

23

24

25

26

27

28

29

30

1450 1500 1550 1600 1650

Ro

tati

on

al P

eri

od

(D

ays)

Number of solar sunspot

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Post-Experiment / Observation– Teaching Phase 5:

Reflection – COMMUNICATE EXPLANATION

• Students can also

compare the

experimentally

calculated values with

values predicted

theoretically.

• Teachers can provide

students with necessary

information, encouraging

them to create a value

Table as beside:

THEORETICALLY PREDICTED VALUES

Heliographic

latitudeRotational Period (Days)

0 26,710 27,120 27,530 28,340 29,3

EXPERIMENTALLY CALCULATED VALUES

Number of

solar

sunspot

Heliographic

latitude

Average

rotational period

(days)

1635 17,5 25,73

1633 5 23,94

1634 16 25,96

1486 26 28,93

1575 2 26,83

1579 28,5 26,66

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Post-Experiment / Observation– Teaching Phase 5:

Reflection – COMMUNICATE EXPLANATION

• Finally, students can plot graphs of the experimentally

calculated and theoretically predicted values, comparing the

equation parameters after linear fit to the plot points, as follow:

y = 0.064x + 26.5R² = 0.955

26

27

28

29

30

0 10 20 30 40 50

Su

n r

ota

tio

na

l p

eri

od

(da

ys)

Heliographic latitude

y = 0.084x + 25.01R² = 0.306

23

24

25

26

27

28

29

0 5 10 15 20 25 30

Su

n r

ota

tio

na

l p

eri

od

(da

ys)

Heliographic latitude

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• As follow up activities, students can continue collecting photos

of Sun every day.

• Furthermore, we can additionally suggest the calculation of the

temperature at the peak (umbra) of the sunspots.

• By help of Salsa J, we obtain plot profiles of sunspots, as seen

in the following figures:

Post-Experiment / Observation– Teaching Phase 5:

Reflection – FOLLOW UP ACTIVITIES AND MATERIALS

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• According to Stefan-Boltzmann’s law:

(where F the total emitted radiation, σ the Stefan-Boltzmann

constant and the effective temperature) we can calculate the

temperature at the top (umbra) or at penumbra of sunspot, if we

know the photosphere’s temperature.

• Indicative ratio values:

Post-Experiment / Observation– Teaching Phase 5:

Reflection – FOLLOW UP ACTIVITIES AND MATERIALS

Students are asked to determine the temperature of the spots

based on cross-sections profiles, knowing that the photosphere’s

temperature is almost 5800οΚ.

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• We encourage students to fill in a Value Table, as follow:

Post-Experiment / Observation– Teaching Phase 5:

Reflection – FOLLOW UP ACTIVITIES AND MATERIALS

Number of

spot

Ratio of radiation

intensity from the

shadow by

photosphere

Ratio of radiation

intensity from the

penumbra by

photosphere

Temperature at

the shadow of the

solar sunspot (oK)

Temperature at

the penumbra of

the solar

sunspot (oK)

1575 0,157 0,686 3635 5258

1635 0,289 0,647 4237 5181

1633 0,192 0,846 3822 5540

1634 0,325 0,722 4361 5326

1486 0,163 0,536 3665 4944

1635 0,183 0,662 3779 5211

1582 0,271 0,681 4168 5247

1484 0,248 0,745 4078 5368

• Calculating thus, the relevant temperatures on umbra and

penumbra of the Solar sunspots.

• After these calculations we ask students why do they think the

spots are black?

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Contact Information

• Name Surname: Chiotelis Ioannis

• Affiliation: www.pelopio-lykeio.gr

• Address: Arakinthou 20, 26226, Patras, Greece

• Telephone: +306948372341

• Email: [email protected]

[email protected]

[email protected]