Download Hertzsprung Rusell Diagram KLT

HERTZ SPRUNG - RUSSELL
DIAGRAM
HR DIAGRAM
Recall how a HR diagram is constructed
Use a HR diagram to describe the life cycle
of stars
Understand and explain the characteristics
of stars
HR DIAGRAM
Stars can have a range of characteristics, such as
mass, diameter, temperature and luminosity
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
HR DIAGRAM
Stars that look to us as though
they are near each other, may
intact be very far away from each
other. Distant but very bright stars
look similar to close but dim stars.
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
MAGNITUDE
AQA Only
On a star chart, stars are given an apparent magnitude
value, the lower the value the brighter the star appears
The true magnitude (absolute magnitude) can be
calculated. This is the apparent magnitude of the star if
you were 10 parsecs away.
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
MAGNITUDE
Magnitude is a logarithmic scale
apparent magnitude m = -2.51 log (I / 2.56 x 10-6)
I = intensity
2.56 x 10-6 lux = intensity for magnitude 0 star
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
MAGNITUDE
m - M = 5log (d/10)
M = absolute magnitude
d = distance in parsecs
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
WEIN’S DISPLACEMENT
LAW
T = temperature of
star in K
λmax T = constant
= 2.9 x 10-3 mK
A black body is one
that absorbs all the
EM radiation that
falls incident on it
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
STEFAN’S LAW
P =σAT4
P = power
A = surface area
T = temperature (K)
σ = stefan’s constant = 5.67 x 10-8 Wm-2K-4
Sometimes referred to as Stefan-Boltzman Law
(Stefan arrived at it experimentally, Boltzman did it
theoretically)
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
STEFAN’S LAW
The ratio of the power output of two stars can be used
to calculate the ratio of the diameters of the stars. (If
one of those starts has a known diameter e.g the Sun
the diameters of the other star can be determined)
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
HR DIAGRAM
Plotting the luminosity of stars against the
temperature reveals a pattern
Spectral class and absolute magnitude can
also be plotted to reveal the same pattern.
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
LUMINOSITY
Luminosity is the total radiant power
output of the star and so is measured in
Watts
It can also be measured in lux
(1 lux = 1 lumen per metre squared )
(1 lumen = measure of total visible light
emitted in a defined beam)
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
LUMINOSITY
me times HR diagrams plot luminosity as a factor of solar luminos
As a result, the scale is usually logarithmic
(Temperature is also plotted logarithmically)
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
Main sequence
Sun
Questions
Describe, briefly the sequence of events which occur in
the formation of a star, such as our Sun, from interstellar
dust and gas clouds.
In your answer, you should make it clear how the steps in
the process and sequenced.
OCR G485 Jan 2013
[4 marks]
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
Questions
Any three from:
1. (Interstellar dust and gas) cloud is drawn together by
gravitational force / colapse / gravity
2. Loss in (gravitational) PE / KE increases / temperature
increases
3. Fusion (of protons / hydrogen nuclei) takes place
4. Energy is released in fusion reactions
5. A stable star is formed when gravitational pressure is
equal to internal / gas / radiation pressure
QWC: The steps in the process are correctly sequenced
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
B1 x3
B1
Understand and
explain the
characteristics of stars
Questions
The final evolutionary stage of the star is a white
dwarf. Describe some of the characteristics of a white
dwarf.
[2 marks]
Explain why, in its evolution, the star is brightest
when at its coolest.
[2 marks]
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars
Questions
Any two from:
• (extremely) dense / (very) hot / low luminosity
• no fusion reactions occur
• it is a remnant of a low-mass star
• correct reference to Fermi pressure / elec
B1 x 2
Red giant identified
B1
(It is cooler but has) large surface area (and therefore
radiates large amounts of energy)
B1
Recall how a HR
diagram is constructed
Use a HR diagram to
describe the life cycle
of stars
Understand and
explain the
characteristics of stars