Transcript PowerPoint-presentatie - Maastricht University

Introduction
to
Astrophysics
Ronald L. Westra
Department Mathematics
Maastricht University
Introduction
to
Astrophysics
1.
Astronomic Scales in
Space and Time
Earth
Sun
Jupiter.
Galaxy M31, known as the Andromeda nebula
Collection of galaxies. The three fuzzy galaxies left merging,
The crisp galaxy in the center is on the background
Large-scale map of
the
observable
universe showing
the the largest
structures visible in
the universe.
Each point in this
diagram represents
one single galaxy
The Universe at
the young age of
300,000 years. The
colors represent
temperature
fluctuations in the
Cosmic
Background
Radiation
Wilkinson
Microwave
Anisotropy Probe
Subtle variations in the CBR.
The Giant Impact
Theory suggests
that a Mars-sized
object crashed into
the early Earth.
Most of the debris
thrown into space
fell back on Earth,
but a fraction
aggregated into the
Moon. This theory
is supported by the
similar
composition of
rocks on the Earth
and Moon.
2.
Stellar Evolution
Some characteristics of the sun
radius (R)
7 1010 cm
mass (M)
2 1033 g
mean density ()
1.4 g/cm3
total energy output (L)
3.82.1026 Joule/sec
age
1.5 1017 sec
core temperature
5 106 K
surface temperature
5 103 K
distance to earth
1.5 1013 cm
Nuclear fusion in centre of sun
1
4
0
41 H  2 He  2 1 e      26.7 MeV
Spectral Types
O –B–A–F–G –
K–M–R–N–S
Absolute and Relative
Luminosity
Lrel 
Labs
4r
2
Original Hertzsprung-Russell Diagram ( HRD)
Binding energy per nucleon as function of mass number A.
Glowing gaseous streamers of an extinct titanic supernova explosion of a massive star
in Cassiopeia A (Cas A)
Composite image
of the
Crab Nebula
showing
superimposed
images of X-ray
(blue) (by
Chandra X-ray
space telescope),
and optical (red)
(by the Hubble
space telescope).
First published registration of a pulsar, Hewish et al., Nature 217, p. 710, 1968.
log L/ L
log Teff in K
Path of the stellar evolution of a main sequence star of one solar mass
in the Hertzsprung-Russell diagram
L/ L
sun
surface temperature (K)
The HRD for 10 stellar clusters. At right ordinate the age in billion
years of the bifurcation point from the main sequence.
Abundances of chemical elements in the neighbourhood of our
sun. The marks are from the intensities from spectral
absorption lines in the sun’s atmosphere, the lines from
meteorite and terrestrial data.
An example of an unstable – but notperiodic – star is this massive ‘WolfRayet star’ NGC2359, that irregularly
ejects large parts of its own outer
envelope in gargantuan explosions. The
star itself is in the central bubble, the
clouds are remnants of previous
ejections.
instability strip
Cepheids
RR Lyrae
main sequence
long period variables
Luminosity
surface temperature
Variable stars in the HRD. Pulsating variable stars are found in
the instability strip connecting the main sequence and the redgiant region.
Cepheid Luminosity-Period Law
5
log(L/Lsun)
4.5
Relation between luminosity and
oscillation period for Cepheid type 1
variable stars.
4
3.5
3
2.5
0
20
40
60
Period [days]
80
100
Ronald L. Westra
Systems Theory Group
Department Mathematics
Maastricht University
[email protected]