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Q: Astronomical questions ( Answered,   1 Comment )
Question  
Subject: Astronomical questions
Category: Science > Astronomy
Asked by: danieldubbs-ga
List Price: $5.00
Posted: 01 Mar 2005 18:23 PST
Expires: 31 Mar 2005 18:23 PST
Question ID: 483229
12. What is light and Why are stars white? 
or 
14. What is the temperature on the Moon? and how do we know? 
What ever question you can answer best
Answer  
Subject: Re: Astronomical questions
Answered By: skermit-ga on 01 Mar 2005 18:41 PST
 
I'll answer the 2nd question:
Here are some temperatures of the Moon that I've found for you:

Mean surface temperature (day)		+107C  	
Mean surface temperature (night)	-153C  	
Maximum surface temperature		+123C  	
Minimum surface temperature		-233C 

The temperatures are measured using infrared radiation, either by
satellites in space, or by sensors on Earth. Believe it or not, the
first measurement was made in 1870.

Here are some links with more information:

http://www.solarviews.com/eng/moon.htm
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/timeline/timeline_onepage.html

Thank you for your question,

skermit-ga

Request for Answer Clarification by danieldubbs-ga on 02 Mar 2005 18:44 PST
How do scientists use infrared radiation to measure the temp? What kind of sensors?

Clarification of Answer by skermit-ga on 22 Mar 2005 12:45 PST
You should rate this question, and then ask your followup question as
a new question altogether since it does not fall within the original
scope of this one. Thank you for your question, and glad I could
answer the question.

skermit-ga
Comments  
Subject: Re: Astronomical questions
From: quantumdot-ga on 07 Mar 2005 18:41 PST
 
Not all stars are white. Look in the constellation orion, and you can
clearly see Rigel is blue, and betelgeuse is quite red. Our own sun is
quite yellow, as you may have noticed. The color of the star is
dependant upon its temperature. The hotter the star, the bluer the
color. Stars generally behave like black body radiators.

However, if a star is moving towards us, its color will be blue
shifted. Like wise, if it is moving away from us, it will appear
redder. This change in observed frequency is called Doppler shift.

Light is either a particle (called a photon) or an electro-magnetic
wave (with the electrical component oscillating orthogonally to the
magnetic component) depeding on which is more convienent at the time.

Infra-red light is light with a wavelength greater ~700-800 nm.
Typical detectors for IR light include semiconductor materials
(Indium-gallium-arisnide, INGAS, charded coupled device (CCD
detectors, like in high end digital cameras) and even IR sensitive
film (primarily used in medical applications).

IR can be used to measure temperature because most objects behave as
black body radiators.

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