apparent magnitude winter spring name yuanfeng date 3 25 20 background one of the many characteristics that determine the visibility of a celestial object as seen by the eye is its apparent magnitude this is the brightness a star has a

APPARENT MAGNITUDE-WINTER/SPRING

Name: YUANFENG Date:__3/25/20___________

Background: One of the many characteristics that determine the visibility of a celestial object as seen by the eye, is its apparent magnitude. This is the brightness a star has, as seen by an observer on Earth. It is a numeric value and originally ranged from 1 to 6. Important note: The lower the number, the brighter the star. Betelgeuse, having a magnitude of 0.43, is brighter than Bellatrix, with a magnitude of 1.62. The early Greek astronomer, Hipparchus, is credited with this concept. The range has been extended so that the sun’s apparent magnitude is -26.7. The brightest star is Sirius, at -1.6. The faintest, as seen in a very dark sky is ~ 6th magnitude. Each magnitude is fainter or brighter than the previous one by 2.512, on a logarithmic scale. Therefore, a 1st magnitude star is (2.512)5 = 100 times brighter than a 6thmagnitude star. What you are going to do is tabulate the apparent magnitudes of a number of stars within certain constellations and determine their visibility in a city, the suburbs and the country.

Magnitude Scale

Magnitude

Range

-1

-1.50 to -0.51

0

-0.50 to +0.49

1

+0.50 to +1.49

2

+1.50 to +2.49

3

+2.50 to +3.49

4

+3.50 to +4.49

Procedure:

Go to the web and download the web version of Stellarium. This version works on your browser, you are not downloading anything. To set the time, look at the box on the lower right. When you click on it, you can see a sliding blue dot, that you can use to set the time, which is in 24 hour format. Slide it to the right, until you 21:00:00, corresponding to 9 PM. At bottom center, click on the far left Constellations tab. This turns on the constellation names and draws the constellation lines. To see the data on the stars, just click on the respective stars to see the data appear in a box on the lefthand side. The top property is Magnitude. The lower the magnitude, the brighter the star.

Orion

Click on the bright stars in Orion and list their magnitudes on the Magnitude column. You just need to go along the constellation lines.

Star’s name Magnitude

Betelgeuse

Rigel

Bellatrix

Alnitak

Alnilam

Mintaka

Saiph

Lambda Orionis

What is the brightest star in Orion and what is its magnitude?

After you are done with Orion, go to Canis Major. Record only the magnitudes of the named stars along the constellation lines as shown below in the table.

Canis Major

Star’s name Magnitude

Sirius

Mirzam

Adhara

Aludra

Wezen

Furud

What is the brightest star in Canis Major and what is its magnitude?

After you are done with Canis Major, scroll leftward, until you see Leo. Proceed the same as you did for Orion and Canis Major, going only along the constellation lines.

Leo

Star’s name Magnitude

Regulus

Zosma

Algenubi (epsilon Leonis)

Rasalas (mu Leonis)

Adhafera (zeta Leonis)

Algieba

Denebola

Al’dzhabkhakh (eta Leonis)

Chertan (theta Leonis)

What is the brightest star in Leo and what is its magnitude?

Analysis:

In the chart below, indicate the number of 1st magnitude and brighter, 2nd magnitude, and 3rdmagnitude and fainter stars in Orion. To do this, look at the magnitude scale at the beginning of the lab and see how many 1st magnitude stars, 2nd magnitude stars, etc.

Orion

How many 1st mag stars How many 2nd How many 3rd or brighter magnitude stars mag stars or fainter

What was the total number of stars in Orion? _____________

In the chart below, indicate the number of 1st, 2nd, 3rd magnitude and fainter stars in Canis Major.

Canis Major

How many 1st mag stars How many 2nd How many 3rd

or brighter magnitude stars mag stars or fainter

What was the total number of stars in Canis Major? _____________

Lastly, in the chart below, indicate the number of 1st, 2nd, and 3rd magnitude and fainter stars in Leo.

Leo

How many 1st mag stars. How many 2nd How many 3rd

or brighter magnitude stars mag stars or fainter

What was the total number of stars in Leo? _____________

Consider these three locations:

  • downtown city – only the 1st magnitude stars and brighter and 2nd magnitude stars can be seen. Anything fainter is not visible.
  • suburban – only 3rd magnitude stars and brighter are visible
  • very dark, country site – all of the stars can be seen

A. Consider that, in order for a constellation to be recognizable, at least 1/5 or 20% of the stars must be visible. Based on this criterion which, if any, of these constellations are visible in downtown San Mateo? (Show your ratios to explain your answer. For example, add up all the stars for Orion that are 1st and 2nd magnitude, and divide that number by the total number of stars in Orion. That is your ratio and see how it compares to 1/5 or 20%.)

Orion ratio:

Canis Major ratio:

Leo ratio:

B. Which, if any, of these constellations are visible in the suburbs? (Show your ratios to explain your answer.)

Orion ratio:

Canis Major ratio:

Leo ratio:

C. You can assume that all three constellations are visible in a country sky.

In what city do you live?

a) Which, if any of these constellations would be visible where you live?

b) What role does light pollution play in the visibility of constellations where you live?

c) Are there any other factors, that would affect the visibility of constellations where you live?

What you have learned in this experiment?

 
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