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SYRACUSE / Astronomy / ASTR 104 / Which is the brightest star?

Which is the brightest star?

Which is the brightest star?

Description

School: Syracuse University
Department: Astronomy
Course: Stars, Galaxies & Universe
Professor: Saulson
Term: Spring 2019
Tags: ast104, astronomy, emission spectrum, and space
Cost: 50
Name: AST 104 Study Guide MIDTERM 1 2/11
Description: These notes cover the first AST 104 unit. Everything from Absolute brightness (etc) to spectra.
Uploaded: 02/07/2019
3 Pages 124 Views 14 Unlocks
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AST 104


Which is the brightest star?



Feb 11 Exam #1 Study Guide

Study Guide © Alyeska Dronsfield 2019. For personal use only, not for redistribution.

Apparent Brightness: how bright a star appears from Earth

Absolute brightness (also called absolute magnitude): how bright a star is from 10 parsecs  away

1 parsec = 3.26 light years

___1___ = distance

Parallax (in arcsec)

1° = 60 arcmin = 3600 arcsec

Angular size = physical size (diameter) 

 360° 2πdistance

Sun = .53° angular size We also discuss several other topics like What is depressants?

Moon = .52° angular size

Angular size is measured in degrees!

__.5°__= ______1______ <-- Equation filled in with the Sun's angular size & distance  360° 2π(150,000,000)


What is emission spectrum?



The lower the number in the scale of brightness, the brighter the star.

The brightest star, SIRIUS, has an Absolute Magnitude of -1.46

The brightest star in our sky, the Sun, has an Apparent Brightness of -26.7, but an Absolute Magnitude of  4.8, meaning it is a medium-bright star.

Absolute Magnitude = Luminosity

Apparent Brightness = (watt/square meter)

Luminosity - (watt = energy/second)

Apparent Brightness = _Luminosity_ 

 4π(distance)2  

Luminosity = Apparent Brightness(4π(distance)2 

Sun = 3.86 x 1026 = AB x 4π(150,000,000)2  

3.86 x 1026 W = LSun


What is wien's law?



[10-4 LSun -- 101 LSun -- 106 Lsun] <----- luminosity scale, 101 being the luminosity of the Sun Light is a disturbance in space.  We also discuss several other topics like What is chevron doctrine?

Ultraviolet [ Visible light ] Infrared  

Shorter wavelengths, more energy <-- ---> longer wavelengths, less energy Hotter stars Cooler stars

 400 nm = violet 700 nm = red We also discuss several other topics like What is behaviorism theory?

Shorter wavelengths have more energy.

Wien's Law: hotter stars emit light with shorter waves.

Stefan-Boltzmann Law: each square meter of a hotter object's surface emits  more light across the spectrum.

Even though the red star glows red, the blue star is emitting more red light overall. The color is determined by where the graph peaks.

Continuous Spectrum: the full-color spectrum related to blackbody/thermal radiation. Example would  be the incandescent light bulb demo in class.

Emission spectrum: a color spectrum that is mostly black except for a few specific colored lines. The  lines' position correlates to the gas giving off the light (ex helium, hydrogen, etc)

Absorption spectrum: a mix between the continuous and emission spectrums. Appears as a continuous,  full color spectrum with black lines placed in certain positions. Those black lines are the "photo  negatives" to their corresponding emission spectrum. (ex where helium would have a blue line in an  emission spectrum, it has a black line in the same place in an absorption spectrum) If you want to learn more check out What is the formula of mirror equation?
If you want to learn more check out The plus end directed on cytoplasmic microtubules is what?
If you want to learn more check out What is elasticity of demand?

Stars have an absorption line spectrum because they have a hot opaque inner part (blackbody radiation)  and are surrounded by a cloud of gas.

The moon has its own absorption line spectrum, and it's identical to the Sun's!

Study Guide © Alyeska Dronsfield 2019. For personal use only, not for redistribution.

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