Question

Question #eb38d

Answer 1

A) Type M Star with a red color.
B) A Type A star with a temperature of 9200’K would have an emission of `3.15 xx 10^3` angstroms.

Explanation:

Stars are classified according to the wavelength(s) (energy) of light that they produce. When astronomers first observed these differences in the 19th century they devised a classification system that assigned letters to various spectral types. (These letters are arbitrary and don't stand for anything.)

The system used by astronomers today has seven categories, each of which is associated with a temperature. From hottest to coolest these categories are O, B, A, F, G, K, and M. These categories are each divided into 10 numbered subclasses, so an astronomer might speak of an A7 star or an M3 star. The sun is a G2 star. A traditional mnemonic for the sequence is Oh, Be, A Fine Girl/Guy, Kiss Me!
Details and graphics are here:
http://astro.unl.edu/naap/ebs/spectraltype.html

Classification of Star Types is detailed here:
http://www.atlasoftheuniverse.com/startype.html

The spectrum of a star is close enough to the standard blackbody spectrum that we can use Wien's Law to get an estimate of its surface temperature.
`lambda_max = (0.29 cm*K)/T`
That is, if you observe the spectrum of a star and can determine the wavelength where the emission peaks (`lambda_max`), you can calculate that star’s temperature.
(Ref.: https://www.e-education.psu.edu/astro801/content/l4_p2.html)

`8900 angstroms = 8900 xx 10^(-10)m * 100(cm)/m`
`= 8.9 xx 10^(-5)cm`

`8.9 xx 10^(-5) = (0.29 cm*K)/T`
`T = 3258 ‘K`

A star with a peak wavelength of 8900 angstroms corresponds to a temperature of 3258’K and thus a Type M Star with a red color. A Type A star with a temperature of 9200’K would have an emission of
`lambda_max = (0.29 cm*K)/9200 = 3.15 xx 10^(-5)` cm,
or `3.15 xx 10^3` angstroms.

An interactive display of color, wavelength and temperature is here (may not work in all browsers):
http://cas.sdss.org/dr6/en/proj/basic/color/fromstars.asp

Answer 2

If you could see this star at all, it would appear to be reddish, closer towards brown. It is in the infrared range of wavelengths. It could be a red giant or brown dwarf.

Explanation:

Information on the relation of wavelengths to color and the visible spectrum is here:
http://www.livephysics.com/physical-constants/optics-pc/wavelength-colors/

A type A star with a temperature of 9200 K would have a mostly hydrogen content. The peak wavelength in Angstroms would occur at 6600 for `Halpha`, 4800 for `Hbeta`, and 4350 for `Hgamma`.

You can see the stars classified by their color temperatures here:
http://cas.sdss.org/dr7/en/proj/advanced/spectraltypes/lines.asp