Spectrum and temperature of the stars


Martin and Yoana
present Spectrum and temperature
of the stars Stars are enormous gas clouds
with core made of heavier elements People have always
been asking themselves How far away are they? Can we measure them? Can we see what they’re made of
and how hot they are? We can’t just go to them. Voyager would need 76,000 years
to reach the nearest star – Proxima Centauri Then how can we explore them? They seem so tiny. Scientist have succeeded in using
the only thing coming from the stars – their light,
to learn more about them. Using spectral analysis,
one can discover what a star is made of. By finding the most intense light colour,
scientist can measure its temperature. But how is it all done? If an element gets hot enough,
it starts emitting light. If we disperse that light using a prism,
we could observe bright fringes at some places Because those spots are uniquely spaced every single one must be due to
a specific energy level inside the atom If we look at a slice of an atom
we will notice unique energy levels Electrons move to a higher level
when they receive extra energy When electrons fall to a lower level,
they loose energy in form of light which in turn creates a characteristic
spectrum of an atom Because each element has a different atom structure,
each one has a unique spectrum. Historically, Isaac Newton is the first
to use the term “spectrum” in 1671 He noticed that when a light beam
goes through a glass prism, part of the beam is reflected by the glass,
and what remains goes through splitting into different colours. He speculated that light consisted
of differently coloured particles and differently coloured light
must have different speed. Modern day spectrometers
still use a prism to produce the spectrum
of a light beam. Sir William Huggins was the first to attempt to disperse light from
celestial bodies by using a spectroscope. He built the first spectroscope,
capable of decomposing light from distant stars. Huggins expected a continuous spectrum
just like the one produced by white light instead he noticed dark lines. He concluded that this absorption spectrum
is produced by gases inside stars which block certain colours These dark fringes can be used
to calculate what an object is made of. That’s how in 1868
Helium was discovered by the French astronomer
Pierre Janssen He observed the emission spectrum
of our sun then he discovered a bright fringe
with wavelength 587.49 nm Later that year an English
astronomer Norman Lockyer concluded that this fringe
is due to an element still unknown on Earth later named Helium
after the Greek word for sun – Helios. But stars are telling
us even more. Spectrum analysis can be used to discover
the largest intensity wavelength Using Wien’s laws we can deduce
even the temperature of a cosmic body. That’s how they measured that
the sun’s temperature is 4,000 °C because green light coming
from it has the brightest intensity. That’s why plants are green
down on Earth. Using the Doppler shift,
we can deduce the speed of celestial bodies. Waves travel in air. When a plane moves, waves in front
of it compress creating high pitched sound. Waves behind the plane stretch
creating low pitched sound. When the plane passes
near you you’ll hear the famous
Doppler shift Same applies for light. When an object approaches,
light before it contracts we call that a blue shift
since objects look blueish When an object is moving away,
light stretches making the object look reddish.
This is called a red shift. When a planet orbits a star a characteristic wobble occurs about
the common centre of masses Observing the star using Doppler shift
scientists can deduce the speed of that motion and thus discover
new planets Some of them may be
teeming with alien life So far about 400 planets
have been discovered None of them is expected to have life due to bad conditions such as being too close to the star
or too far away from it. Doppler shift has been used
to discover how matter was created. Astronomers observed that galaxies
looked redder than they should That only meant that
they were getting away from us. That’s how they realized
that long time ago everything was confined in a tiny spot
from which the Big Bang was produced. Since then the universe
is expanding and scientists have different
opinions about its future. And we know all that
thanks to light the only thing we
get from the stars. Martin Marinov & Yoana Sandinska Produced for
Science and Mathematical school
“Akademik Ivan Tsenov” Vratsa, Bulgaria
2009

4 thoughts on “Spectrum and temperature of the stars

  1. 3DS Max за началото, Sony Vegas за сглабянето, Particle Illusion за големия взрив 🙂

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