Fundamentals of Astronomy:

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Fundamental Questions In Astronomy
Dr Martin Hendry Dept of Physics and Astronomy
Fundamentals of Astronomy Jan 2005
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Fundamental Questions in Astronomy
10 meetings, beginning 11/01/05 Course Aims To
review recent progress in research at the
forefront of astronomy and preview some of the
exciting discoveries which might lie in store
over the next decade - helping us to answer such
questions as

• Is there life on other planets?
• How did the Universe begin?
• How did the first stars and galaxies form?
• Will the Universe expand forever?
• Was Einstein right about gravity waves?
• Are we under threat from asteroids and comets?

Fundamentals of Astronomy Jan 2005
3
Fundamental Questions in Astronomy
Course Lecturers (provisional) Dr Martin
Hendry Dept of Physics and Astronomy Dr Luis
Teodoro University of Glasgow Dr Josef Khan Ms
Kirsty Selway Mr Matt Pitkin Dr Bonnie
Steves School of Mathematics Glasgow
Caledonian University Contact Details martin_at_a
stro.gla.ac.uk Tel [phone]
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Extra-terrestrial life Is there anybody out
there?
Dr Martin Hendry University of Glasgow
Fundamentals of Astronomy Jan 2005
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Is there Anybody Out There?
Life in the Solar System
The search for Extra-Solar Planets
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Its life, Jim, but not as we know it
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Its life, Jim, and just as we know it
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Life in the Solar System
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Venus Vital Statistics
Surface temperature 450K Atmosphere almost 100
CO Pressure 90 times Earths Sulphuric Acid
Rain Thick crust leads to regular volcanic
resurfacing
2
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Venus Vital Statistics
Surface temperature 450K Atmosphere almost 100
CO Pressure 90 times Earths Sulphuric Acid
Rain Thick crust leads to regular volcanic
resurfacing
2
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Venus Vital Statistics
Surface temperature 450K Atmosphere almost 100
CO Pressure 90 times Earths Sulphuric Acid
Rain Thick crust leads to regular volcanic
resurfacing
2
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Venus Vital Statistics
Surface temperature 450K Atmosphere almost 100
CO Pressure 90 times Earths Sulphuric Acid
Rain Thick crust leads to regular volcanic
resurfacing
2
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Venus Vital Statistics
Surface temperature 450K Atmosphere almost 100
CO Pressure 90 times Earths Sulphuric Acid
Rain Thick crust leads to regular volcanic
resurfacing
2
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Runaway Greenhouse Effect
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Our nearest neighbour Venus
Since Venus formed in approximately the same part
of the solar system as Earth, why did it end up
with so little water? Water enters atmosphere by
outgassing or arrival of comets.
Most likely possibility because Venus is nearer
Sun, and hotter, water never condensed from
atmosphere
Water molecules were then broken up by sunlight
hydrogen escaped into space
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Formation of the Moon Impact from Mars-sized
planetesimal during first billion years.
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Simulations of Lunar formation
Alistair Cameron Harvard College Observatory
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Simulations of Lunar formation
Alistair Cameron Harvard College Observatory
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Impact energy 1 million million megatons
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Impact energy 1 million million megatons
20 billion cubic kilometres of the crust sprayed
into space
Atmosphere ejected into space
Ring of material coalesces into Moon
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Is there life on Mars?
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Is there life on Mars?
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Life on Mars?

• The planet Mars lies tantalisingly close to the
  habitable zone. Could it harbour life? First
  look for water.

• Early observations (from the end of the 19th
  century) showed
• polar caps, whose size varies through the Martian
  year.

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• Schiaparelli, in 1877, described channels or
  canali on Mars

• Percival Lowell, a famous 19th century
  astronomer, claimed to
• have observed canals on Mars - a claim
  which was later proved
• wrong by spacecraft observations

Any life on Mars (at the present at any rate) is
not the canal-building type
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Martian Meteorites
Of the 22,000 or so meteorites that have been
discovered on Earth, only 26 have been
identified as originating from the planet Mars
These rare meteorites created a stir throughout
the world when NASA announced in August 1996
that evidence of microfossils may be present in
one of these Mars meteorites, found in Antarctica
The team found unusual compounds - iron
sulphides and magnetite - that can be produced by
anaerobic bacteria and other organisms on Earth
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The possible evidence of life in ALH 84001 was
all found in and around carbonate mineral
globules
0.5mm
Scanning electron microscope image, showing
bacteria-like structures
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• Mars 2004
• Mars Express ( Beagle 2)
• Spirit Opportunity

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Jan 23rd 2004 Mars Express Orbiter detects
water ice at the South Pole of Mars.
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Jan 23rd 2004 Mars Express Orbiter detects
water ice at the South Pole of Mars.
CO2
Visible light
H2O
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Water on Mars
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2mm
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Fundamental Questions in Astronomy
10 meetings, beginning 11/01/05 Course Aims To
review recent progress in research at the
forefront of astronomy and preview some of the
exciting discoveries which might lie in store
over the next decade - helping us to answer such
questions as

• Is there life on other planets?
• How did the Universe begin?
• How did the first stars and galaxies form?
• Will the Universe expand forever?
• Was Einstein right about gravity waves?
• Are we under threat from asteroids and comets?

Fundamentals of Astronomy Jan 2005
Course website http//www.astro.gla.ac.uk/users
/martin/teaching/fundamentals/
50
Detecting signs of life on other planets

• Many space exploration missions have been
  launched, with a main
• goal being to look for signs of life on other
  planets in the solar system

• One obvious question to ask - if one such
  mission flew past Earth,
• would it detect signs of life here?

• The instruments analysed Earth as if it were an
  unknown planet

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Results of Galileo flyby of Earth

• Infrared images suggested large pools of water.
  Temperature
• measurements showed that this was liquid,
  not ice

• Large oxygen content found in atmosphere.
  Dissociation of
• water by sunlight not enough to explain this
  ? biological action

• Large concentration of methane gas (CH4), also
  suggesting
• biological activity

• Non- natural radio emissions, best evidence of
  intelligent life

None of these signatures were seen from any other
planetary flyby
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The moons of Jupiter
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The moons of Jupiter
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Tidal forces have a major influence on
Europa The icy crust of the moon is covered in
cracks due to tidal stresses, and beneath the
crust it is believed that frictional heating may
result in a thin ocean layer
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Inside Europa
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Corroborative evidence from Galileo Magnetometer
measurements Magnetic field from subsurface
shell Salty Ocean?
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From Science (2002)
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JIMO Jupiter Icy Moons Orbiter
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ICEPICK Europa lander mission
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Inside Europa
Could there be life?..
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How do stars form?
from Nebulae
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How do stars form?
from Nebulae
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The Orion Nebula
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Forming stars (and planets.)
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Forming stars (and planets.)
Pressure
versus
Gravity
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Forming stars (and planets.)
Gas pressure trying to expand the cloud
Pressure
versus
Gravity
Collapse may be caused by shock waves from a
dying star a Supernova
Gravity trying to collapse the cloud
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Starlight is electromagnetic radiation
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Stars of different colours have different
temperatures
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Surface temperature (K)
25000 10000 8000 6000 5000 4000
3000
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-10
100 RS
1000 RS
When we plot the temperature and luminosity of
stars on a diagram most are found on the Main
Sequence
10 RS
Supergiants
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-5
1 RS
102
0
Giants
0.1 RS
Luminosity (Sun1)
Absolute Magnitude
Main Sequence
1
5
0.01 RS
10-2
10
0.001 RS
White dwarfs
10-4
15
O5 B0 A0 F0 G0 K0
M0 M8
Spectral Type
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Surface temperature (K)
25000 10000 8000 6000 5000 4000
3000
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-10
100 RS
1000 RS
Stars on the Main Sequence turn hydrogen into
helium. Stars like the Sun can do this for about
ten billion years
10 RS
Supergiants
104
-5
1 RS
102
0
Giants
0.1 RS
Luminosity (Sun1)
Absolute Magnitude
Main Sequence
1
5
0.01 RS
10-2
10
0.001 RS
White dwarfs
10-4
15
O5 B0 A0 F0 G0 K0
M0 M8
Spectral Type
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Hydrogen fusion fuelling a stars nuclear
furnace
H Hydrogen He Helium
E mc
2
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Surface temperature (K)
25000 10000 8000 6000 5000 4000
3000
.
.
.
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-10
.
.
Deneb
.
.
.
.
Stars on the Main Sequence turn hydrogen into
helium. Stars like the Sun can do this for about
ten billion years
Rigel
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Betelgeuse
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Antares
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-5
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Arcturus
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Aldebaran
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Regulus
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102
0
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Vega
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Mira
Sirius A
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Pollux
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Procyon A
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Luminosity (Sun1)
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Altair
Sun
Absolute Magnitude
1
5
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10-2
10
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Barnards Star
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Sirius B
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10-4
15
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Procyon B
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.
O5 B0 A0 F0 G0 K0
M0 M8
Spectral Type
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Surface temperature (K)
25000 10000 8000 6000 5000 4000
3000
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-10
100 RS
1000 RS
Stars on the Main Sequence turn hydrogen into
helium. Stars like the Sun can do this for about
ten billion years
10 RS
Supergiants
104
-5
1 RS
102
0
Giants
0.1 RS
Luminosity (Sun1)
Absolute Magnitude
Main Sequence
1
5
0.01 RS
10-2
10
0.001 RS
White dwarfs
10-4
15
O5 B0 A0 F0 G0 K0
M0 M8
Spectral Type
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When the fuel runs out formation of a red giant
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The Search for Extra-Solar Planets
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The search for extra-solar planets
The stars are VERY far away. The nearest star
(after the Sun) is about 40 million million km
from the Earth. It takes light more than 4 years
to travel this distance..
If the distance from the Earth to the Sun were
the width of this screen, the nearest star would
be in Paris !!!!
114
Exoplanets are drowned out by their parent
star. Impossible to image directly with current
telescopes (10m mirrors)
Keck telescopes on Mauna Kea, Hawaii
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Exoplanets are drowned out by their parent
star. Impossible to image directly with current
telescopes (10m mirrors) Need OWL
telescope 100m mirror Completed 2020
100m
Jupiter at 30 l.y.
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• 1. How can we detect extra-solar planets?
• They cause their parent star to wobble, as
• they orbit their common centre of gravity

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• 1. How can we detect extra-solar planets?
• They cause their parent star to wobble, as
• they orbit their common centre of gravity

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Star planet in circular orbit about centre of
mass
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Star planet in circular orbit about centre of
mass
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Star planet in circular orbit about centre of
mass Can see star wobble, even when planet is
unseen. But how large is the wobble?
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Star planet in circular orbit about centre of
mass Can see star wobble, even when planet is
unseen. But how large is the wobble?
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Star planet in circular orbit about centre of
mass Can see star wobble, even when planet is
unseen. But how large is the wobble?
e.g. Jupiter at 30 l.y. one three millionth
of the width of the Full Moon !!!
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Detectable routinely with SIM (launch date 2009)
but not currently
The Suns wobble, mainly due to Jupiter, seen
from 30 light years away
width of a 5p piece in Baghdad!
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Suppose line of sight is in orbital plane
Direction to Earth
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Suppose line of sight is in orbital plane Star
has a periodic motion towards and away from Earth
Direction to Earth
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Suppose line of sight is in orbital plane Star
has a periodic motion towards and away from Earth
Detectable via the Doppler Effect
Can detect motion from shifts in spectral lines
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Absorption
Electron absorbs photon of the precise energy
required to jump to higher level. Light of this
energy (wavelength) is missing from the
continuous spectrum from a cool gas
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Emission
Electron jumps down to lower energy level, and
emits photon of energy equal to the difference
between the energy levels. Light of this energy
(wavelength) appears in the spectrum from a hot
gas
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Star
Laboratory
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Stellar spectra are observed using prisms or
diffraction gratings, which disperse starlight
into its constituent colours
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Stellar spectra are observed using prisms or
diffraction gratings, which disperse starlight
into its constituent colours
Doppler formula
Radial velocity
Change in wavelength
Wavelength of light as measured in the laboratory
Speed of light
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Stellar spectra are observed using prisms or
diffraction gratings, which disperse starlight
into its constituent colours
Doppler formula
Radial velocity
Change in wavelength
Limits of current technology
Wavelength of light as measured in the laboratory
Speed of light
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51 Peg the first new planet
Discovered in 1995 Doppler wobble
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51 Peg the first new planet
Discovered in 1995 Doppler wobble
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What have we learned about exoplanets?
Highly active, and rapidly changing, field
Aug 2000 29 exoplanets
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What have we learned about exoplanets?
Highly active, and rapidly changing, field
Aug 2000 29 exoplanets
Sep 2004 136 exoplanets
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What have we learned about exoplanets?
Highly active, and rapidly changing, field
Aug 2000 29 exoplanets
Up-to-date summary at http//www.exoplanets.org
Now finding less massive planets further from
their parent star
Sep 2004 136 exoplanets
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Sep 2004 Two Neptune-mass planets Gliese
436 55 Cancri
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What have we learned about exoplanets?
Discovery of many Hot Jupiters Massive
planets with orbits closer to their star than
Mercury is to the Sun Very likely to be gas
giants, but with surface temperatures of several
thousand degrees.
Mercury
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What have we learned about exoplanets?
Discovery of many Hot Jupiters Massive
planets with orbits closer to their star than
Mercury is to the Sun Very likely to be gas
giants, but with surface temperatures of several
thousand degrees.
Mercury
Hot Jupiters produce very big Doppler wobbles,
but are a big challenge for theories of how
planets form
Artists impression of Hot Jupiter orbiting
HD195019
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Looking to the Future

• The Doppler wobble technique will not be
  sensitive enough to
• detect Earth-type planets, but will
  continue to detect more
• massive planets

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Looking to the Future

• The Doppler wobble technique will not be
  sensitive enough to
• detect Earth-type planets, but will
  continue to detect more
• massive planets
• The position wobble (astrometric) technique
  will detect
• Earth-type planets Space Interferometry
  Mission in 2009
• (already done with HST in Dec 2002 for a 2 x
  Jupiter-mass planet)

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Looking to the Future

• The Doppler wobble technique will not be
  sensitive enough to
• detect Earth-type planets, but will
  continue to detect more
• massive planets
• The position wobble (astrometric) technique
  will detect
• Earth-type planets Space Interferometry
  Mission in 2009
• (already done with HST in Dec 2002 for a 2 x
  Jupiter-mass planet)
• The Kepler mission (launch 2007?) will detect
  transits of
• Earth-type planets, by observing the
  brightness dip of stars
• (already done routinely for much more
  massive planets)

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Looking to the Future

• The Doppler wobble technique will not be
  sensitive enough to
• detect Earth-type planets, but will
  continue to detect more
• massive planets
• The position wobble (astrometric) technique
  will detect
• Earth-type planets Space Interferometry
  Mission in 2009
• (already done with HST in Dec 2002 for a 2 x
  Jupiter-mass planet)
• The Kepler mission (launch 2007?) will detect
  transits of
• Earth-type planets, by observing the
  brightness dip of stars
• (already done routinely for much more
  massive planets)

There was a transit of Mercury on May 7th 2003,
and a transit of Venus on June 8th 2004
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Transit Detection by OGLE III program in 2003
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Looking to the Future

• NASA Terrestrial Planet Finder
• ESA Darwin

2015 launch
These missions plan to use nulling interferometry
to blot out the light of the parent star,
revealing Earth-mass planets
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Looking to the Future
ESP

• NASA Terrestrial Planet Finder
• ESA Darwin

2015 launch
These missions plan to use nulling interferometry
to blot out the light of the parent star,
revealing Earth-mass planets Follow-up
spectroscopy will search for signatures of life-
Spectral lines of oxygen, water carbon dioxide in
atmosphere
Simulated Earth from 30 light years
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• The Search for Extra-Solar Planets
• The field is still in its infancy, but there
  are exciting times ahead
• In only 9 years more than 140 planets have
  already been discovered
• The Doppler method ultimately will not
  discover Earth-like
• planets, but other techniques planned for the
  next 15 years will
• Search methods are solidly based on
• well-understood fundamental physics-
• By 2020, there is a real prospect not
• only of finding Earth-like planets,
• but of detecting signs of life on them.

• Newtons laws of motion and gravity
• Atomic spectroscopy
• Stellar radiation

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• The Search for Extra-Solar Planets
• The field is still in its infancy, but there
  are exciting times ahead
• In only 9 years more than 120 planets have
  already been discovered
• The Doppler method ultimately will not
  discover Earth-like
• planets, but other techniques planned for the
  next 15 years will
• Search methods are solidly based on
• well-understood fundamental physics-
• By 2020, there is a real prospect not
• only of finding Earth-like planets,
• but of detecting signs of life on them.

• Newtons laws of motion and gravity
• Atomic spectroscopy
• Stellar radiation

What (or who) will we find?
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This leads us to another big question The Milky
Way is about 10 billion years old, and contains
around 100 billion stars If the Galaxy is so
big, and so old, shouldnt it already be teeming
with intelligent life? Why havent we found
any yet?
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This leads us to another big question If the
Galaxy is so big, and so old, shouldnt it
already be teeming with intelligent life? Why
havent we found any yet? Fermis
Paradox Where is Everybody?
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• They are here and are meddling in Human
  affairs

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• They were here, and left evidence of their
  presence

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• They exist but have not yet communicated
• The stars are very far away / they have not
  
• had time to reach us

Voyager 1 would take 75000 years to reach
Proxima Centauri
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• They exist but have not yet communicated
• The stars are very far away / they have not
  
• had time to reach us

Voyager 1 would take 75000 years to reach
Proxima Centauri but this is less than
100,000th of the age of the Galaxy
159

• They exist but have not yet communicated
• They stay at home

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• They exist but have not yet communicated
• They stay at home

and surf the net
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• They exist but have not yet communicated
• They are signalling but we dont know how to
  listen

The Waterhole strong H and OH emission
between 1.42 GHz and 1.64 GHz
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• They do not exist
• Rocky planets are rare

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• They do not exist
• Rocky planets are rare

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• They do not exist
• Jupiters are rare

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• They do not exist
• Jupiters are rare

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Are we alone in the Universe? Is life
on Earth an extraordinary accident?
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On the Infinite Universe and worlds (1584)
there is not merely one world, one earth, one
sun, but as many worlds as we see bright lights
around us.
all those worlds contain animals and
inhabitants no less than can our own earth, since
those worlds have no less virtue nor a nature
different from that of our earth.
Giordano Bruno (1548 1600)