Determine body properties by visual spectrum?

In summary, the conversation is about using astronomical spectroscopy to gather information about Sirius A and Sirius B. The speaker is wondering if there are methods to accurately determine the temperature of a star using only its visual spectrum, as using Wien's law can result in incorrect temperatures. The conversation also touches on fitting the spectrum to a black-body curve and extrapolating data from the visual spectrum. The speaker mentions being new to astronomy and asks if there is any way to determine a star's temperature from its visual spectrum, regardless of its color.
  • #1
bhoom
15
0
Hello,
I'v been taking an interest to astronomical spectroscopy lately and I have some questions about that.

In order to get myself going I wanted to get as much information about Sirius A and Sirius B using the distance, obtained by using parallax(I didn't do that but imagine I did) , and their visual spectra(nor did I obtain the spectra by myself, but again imagine that I did).

If I used the information in the visual spectra to put in Wien's law, then the temperatures of the stars would be incorrect. Are there methods to get accurate information by using only the visual spectra, or does it only work for stars that have their lambda max in the visual spectra?

Could I do something with the info in the visual spectra, i.e. an integral, and compare it to 'B-V color index', bolometric/apparent/absolute magnitude or something else?

Thanks in advance, and I'm sorry if I´v understood astronomical spectrography completely wrong.
 
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  • #2
Hrmm, I wish I could help you. Maybe someone else can? I'd like to know also.
 
  • #3
What are the temperatures you come up with if you use Wien's laws? How is the real star different?
 
  • #4
A slightly more sophisticated thing to do would be to fit the spectrum to the black-body curve and get a best-fit value for temperature.
 
  • #5
Drakkith said:
What are the temperatures you come up with if you use Wien's laws? How is the real star different?
If I use Wien's law of displacement(λmax=b/T) I get the temperature to be ~6,000K. That is because the λmax of the visual spectrum is ~4,800Å.
However, the actual temperature of Sirius A is ~10,000K and so according to λmax=b/T the λmax should be ~2,800Å

Nabeshin said:
A slightly more sophisticated thing to do would be to fit the spectrum to the black-body curve and get a best-fit value for temperature.
I read something like that on a site that I found whilst I goggled "determine temperature from visual spectrum" http://mysite.du.edu/~jcalvert/astro/magnitud.htm"

Do I perform some sort of extrapolating operation on the curve of the visual spectrum, compared to the black body curve?

Again I must stress that I´m quite new to astronomy so there might be something fundamental that I have yet to understand.

But all in all, Is there a way* to determine the temperature of a star from it's visual spectrum(even if the star is of a blue-white color, so it's spectrum is in the UV area) ??

*That means any way what so ever; Calculus, algebra, comparing to whatnot and etc etc.
 
Last edited by a moderator:

1. How does the visual spectrum help determine body properties?

The visual spectrum, also known as the visible light spectrum, is the range of wavelengths of electromagnetic radiation that can be detected by the human eye. By analyzing the colors and patterns of light reflected from an object, scientists can gather information about its physical properties such as size, shape, texture, and color.

2. What is the role of light in determining body properties?

Light plays a crucial role in determining body properties through the visual spectrum. As light strikes an object, it is either absorbed, transmitted, or reflected. The reflected light is what we see, and the properties of the object can be inferred from the characteristics of the reflected light, such as its color, intensity, and polarization.

3. Can the visual spectrum be used to determine the chemical composition of a body?

Yes, the visual spectrum can provide information about the chemical composition of a body. Different substances absorb and reflect light in unique ways, resulting in distinct colors and patterns. By analyzing the reflected light, scientists can identify the presence of specific chemicals in a body.

4. Are there limitations to using the visual spectrum to determine body properties?

While the visual spectrum is a useful tool for determining body properties, it does have its limitations. Some materials may not reflect or interact with light in a way that is easily detectable by the human eye. Additionally, the visual spectrum can only provide information about surface properties and may not be able to penetrate deeper layers of an object.

5. How is the visual spectrum used in practical applications to determine body properties?

The visual spectrum is used in a variety of practical applications to determine body properties. For example, in medical imaging, doctors use different wavelengths of light to create images of internal body structures. In forensic science, investigators use the visual spectrum to analyze evidence such as fingerprints and fibers. In agriculture, the visual spectrum is used to assess the health and growth of plants. Overall, the visual spectrum is a valuable tool for non-invasive and non-destructive analysis of body properties.

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