Transcript Questions to answer - high school teachers at CERN

High School Teachers
2006
Questions to answer
1.How can we understand if what we see is a
star or a planet?(or something else…..)
2.Can you imagine an easy way to find how far a
star is from the earth?
3.Can you understand what the materials are in
the star from that distance?
4.If there are stars like our sun is it possible to
have planets like our planet? Are We Alone?
1.How can we understand if what we see is
a star or a planet?(or something else…..)
Planets
If we consider the Earth as the
centre of the solar system
then the sun and the planets
are in the same plane.
So the planets during the
night must be in the same
trajectory as the sun in the
day.
But…..
How can we distinguish
the planets from the stars
even in this narrow
plane?
Stars
In the case of a planet the
cone of light in the surface of
the upper atmosphere is about
a few hundred meters but in
the case of a star is only a few
cm. So the atmospheric
turbulence may affect the
image of the stars but not
those of the planets. That is
why the stars twinkle at night
but the planets do not.
2.Can you imagine an easy way to find
how far a star is from the earth?
practically
For the Sun
Intensity of light
Distance
I 0  1000W / m2
8 min  108 Km  105 yl
For a star (like our sun)
We can imagine that a star
looks like a light of 100W at a
distance of 10Km
Intensity of light
I
P
7
2

10
W
/
m
r2
Io
Io r 2
P P
 2 / 2   2  r  yl
Distance
I
ro r
I
ro
Exact methods of finding distances
Exact but only for
near objects
Parallax
sin  
1AU
 r  1AU / sin 
r
Only for distances up to
200 light years
Star distance
Astronomical
unit =1AU
r
Other methods……..
As far as we can see
•Standard Candles
Novae
6 million light years
Supernovae
30 million light years
Cepheid
60 million light years
M  m  5(log 10 D  1)
•Hubble's Law
v =H D
1billion light years
Example For this
type of stars we
can evaluate with
great accuracy
the absolute
magnitude by
change of the
period of
luminosity
3.Can you understand what the materials are
in the star from that distance?
The analysis of light is a common phenomenon
Spectroscopy
Continuous spectrum
Hot gas
Emission spectrum
Cold gas
Absorption spectrum
Each element is responsible for a different set of
absorption lines in the spectrum so the spectrum
indentifies the element like the fingerprint indentifies
the human.
Spectroscopy mechanism
Cold gas
The absorption spectrum of the sun
4.If there are stars like our sun is it possible to
have planets like our planet? Are We Alone?
What is this;
UFO Sightings Map:
Western Hemisphere
If you don’t believe….
THEORIES
panspermia
Exogenesis
MATHEMATIC CALCULATION
DRAKE EQUATION
N is the number of civilizations in our galaxy with which we might expect to be able to communicate at
any given time
and
R* is the rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is average number of planets that can potentially support life per star
fl is the fraction of the above that actually go on to develop life
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of the above that are willing and able to communicate
L is the expected lifetime of such a civilization
Current estimates of the Drake equation parameters N=0,000008
Direct search
Arecibo message
SETI (Search for ExtraTerrestrial Intelligence)
OBSERVATIONS OF EXTRASOLAR
PLANETS
Multiple planet systems
There are currently 45 known
planets in 19 multiple planet
systems
Single planet systems
There are currently 144
known planets in single-planet
systems
GQ Lupi on 25 June 2004 with the
adaptive optics instrument
MISSIONS FOR EXTRASOLAR PLANETS
SEARCHING
NASA Kepler Mission (2008)
Kepler spacecraft
ESA
Darwin (2015)
Darwin