Using radiation to investigate the stars Flashcards
What is the layer of gas that stars emit light from called?
The photosphere.
What is a black body?
A body or surface which absorbs all the electromagnetic radiation that falls upon it (eg stars).
What is the line emission spectrum?
Observed for a low pressure atomic gas
An atom absorbs energy which excites an electron to a higher level. The electron then falls back down to the lowest possible energy level and emits a photon of em radiation
Each electron gives out a particular wavelength photon which forms the line spectrum
Appears as a few lines of colour on a black background when viewed through a diffraction grating
What is the continuous emission spectrum?
All wavelengths of light are present from red to violet.
What is the line absorption spectrum?
When white light is passed through a cool atomic gas, dark lines are observed in the continuous spectrum. The atoms of the gas absorb certain wavelength photons. Appears as dark lines on a continous spectrum background when viewed through a diffraction grating.
What is Wiens law?
λmax (m) = W (mK) / T (K)
What is spectral intensity?
The amount of light energy striking each metre squared per second (Wm-2).
What is the inverse square law of light?
The intensity of light observed from a source is inversely proportional to the square of the distance from the source.
What is the equation for intensity?
I (Wm-2) = P (W) / 4πx2 (m)
What is Stefans law?
P (W) = σAT4
What is the wavelength for gamma rays?
10^-12m
What is the wavelength for X-rays?
10^-10m
What is the wavelength for ultraviolet light?
10^-8m
What is the wavelength for visible light?
4 to 7x10^-7m
What is the wavelength for infrared light?
10^-5m
What is the wavelength for microwaves?
10^-2m
What is the wavelength for radio waves?
10^2m
What is the general trend across the electromagnetic spectrum from gamma to radio?
Decreasing frequency, increasing wavelength.
What is the general trend across the electromagnetic spectrum from radio to gamma?
Decreasing wavelength, increasing frequency.
What is multi wavelength astronomy?
Observing different objects in space by studying them with telescopes that detect different regions of the EM spectrum.
What is the use of X-rays in multi wavelength astronomy?
Observing very hot matter heated up as it spirals towards a black hole (10^6 to 10^8 K).
What is the use of ultraviolet light in multi wavelength astronomy?
Observing supernova remnants and hot stars (10^4 to 10^6 K).
What is the use of visible light in multi wavelength astronomy?
Observing planets, stars and some satellites (10^3 to 10^4 K).
What is the use of infrared light in multi wavelength astronomy?
Observing cool clouds of dust and gas (10 to 10^3 K).
What is the use of microwaves in multi wavelength astronomy?
Observing the cosmic microwave background radiation (1 to 10 K).
Describe the main features of the spectrum of a star and state where in the star they arise
Continuous spectrum is due to all radiation of all wavelengths being emitted from the surface of the star.
Line absorption spectrum is due to the passage of radiation through the stars atmosphere.
