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Planets Beyond
the Solar
System
(EXOPLANETS)
SUDUM/Duy
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THE GOAL
The ultimate goal is to find
earth-like planets in earth-like orbits around sun-like
stars - as potentialhabitats for life.
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Introductory questions
1. a. Are we alone in the Universe?
b. Give reasons for your answer
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. 2. (a) Do you think that there could be
other planets outside our solar system?
(b). Give reasons for your answer
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3. (a). Is the Earth the only planet
with life on it?
(b). Give reasons for your answer
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4.(a) Do you think it is possible to
find other planets if they exist?
(b) Give reasons for your answer
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5. (a) What makes up a Rocky/Terrestrial planet?
(b) What makes up a gaseous planet?
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What is the IAU Definition of a
Planet?
A planet is a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes
a hydrostatic equilibrium (nearly round) shape,
and
(c) has cleared the neighborhood around its
orbit.
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What is the IAU Definition of a Dwarf
Planet?
A dwarf planet is a celestial body that:
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity toovercome rigid body forces so that itassumes a hydrostatic equilibrium (nearlyround) shape,
(c) has not cleared the neighborhood aroundits orbit, and
(d) is not a satellite.
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Our Solar System
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Two Types of Planets
Gas GiantsRocky
Planets
These differ in mass, size, composition, &
distance from the Sun.
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Formation of planetary systems
Collapse of gasCloud
Spins up, flattensinto a disk
Solids condense,
forming seeds
Collisions form
large bodiesImage: Tarbuck & Lutgens (2000)
Wh i th U i ?
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Where are we in the Universe?
Our galaxy alone likely contains
hundreds of billions of new worlds
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Our Theory
If we assume all stars form
Similarly, what is your prediction
about planetary systems in and
beyond the milky way?
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we expect many planetary
systems in and beyond the
Milky Way!
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Exoplanets are sometimes called
extrasolar planet.
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What is an exoplanet?
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Exoplanets are planets
that orbit stars otherthan our Sun
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What is the IAU Definition of an Exoplanet?
Objects with true masses below the limiting mass
for thermonuclear fusion of deuterium (currently
calculated to be 13 Jupiter masses for objects of
solar metallicity) that orbit stars or stellar remnantsare "planets" (no matter how they formed).
The minimum mass/size required for an extrasolar
object to be considered a planet should be thesame as that used in the Solar System.
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What is the IAU Definition of a
Substellar object?
Substellar objects with true masses above the
limiting mass for thermonuclear fusion of
deuterium are "brown dwarfs", no matter how
they formed or where they are located.
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What is the IAU Definition of a Free
floating Object?
Free-floating objects in young star clusters
with masses below the limiting mass forthermonuclear fusion of deuterium are not
"planets", but are "sub-brown dwarfs" (or
whatever name is most appropriate).
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Exoplanets vs. Brown Dwarfs
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In order to sustain hydrogen fusion, a stars
mass must be approximately 0.08 solar
masses or above.The mass of a Brown dwarf is below this
limit.
In fact, Brown dwarf sizes are comparable tothe size of Jupiter.
About Brown Dwarfs
Searching for exoplanets
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Are Brown Dwarfs stars or planets?
Searching for exoplanets
According to the IAU (International Astronomical
Union) a brown dwarf has a mass above that
needed for fusion of deuterium (approximately
13 Jupiter masses). An object lower than that
mass and orbiting a star (or star remnant) is said
to be a planet.
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Why study Brown Dwarfs?
Searching for exoplanets
They have characteristics of both stars and
planets.
They provide the chance to study planet-like
atmospheres which are hot.
There are most likely as many brown dwarfsas there are stars.
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Classifications of Habitable planets
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Planet habitable zones are found
around Sun-like star systems
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Planet habitable zone
is the region around a star within which planetary-
mass objects with sufficient atmospheric pressure
can support liquid water at their surfaces
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Earth is in the Goldilocks zone.ooking for life
The Earth is the only planet in our solar system
that we know has life, but
It is not too hot and not too cold.It has liquid water.
http://science.nasa.gov
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What is our definition of life?
ooking for life
As we know it here on EarthLiquid water is needed for life
Might be subsurface
Life is carbon-based
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Looking for life
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How Will We Know A Planet
Supports Life?Look for evidence
of oxygenLook for liquid
water
Analyze the reflected
light from the planet
to see if the planet
has an atmosphere
Look for signs of
biological activity
(methane)
And Rule Out Other Explanations?17
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Scientists are using the
methods discussed to find anexoplanet with the right stuff.
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ooking for life
And they are searching elsewhere in our
Solar System.
Eight planets (and five dwarf planets)
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Jupiters moon Europa?
ooking for life
Evidence for liquid water ocean under ice
The water may be in contact with rocks
The Voyager and Galileo spacecrafts have
given some information about Europa, but
NASA is hoping to launch the Europa orbiter
in 2020.
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On the surface, it is a frozen desert
There may be subsurface water
There is evidence of methane in the
atmosphere
It is not too cold or too hot
Gravity on mars is about 38% that of earth
It has an atmosphere that offers protection
from cosmic and Suns radiation
The day and Night Rhythm is similar to that of
earth
ooking for life
How about Mars?
http://science.nasa.gov
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For centuries, people have been
searching for other worlds like our own.
We now know that there are many
exoplanets. Also, life (extremophiles)
can withstand very harsh conditions.
The challenge now is to find terrestrial
planets, similar in size and conditions to
our Earth, where liquid water and life
might exist.
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Extrasolar Planets Encyclopediahttp://exoplanet.eu/catalog.php
New Worlds Atlashttp://planetquest.jpl.nasa.gov/atlas/atlas_index.cfm
Current Planet Count Widgethttp://planetquest.jpl.nasa.gov/widget.cfm
Current exoplanets counts
http://exoplanet.eu/http://planetquest.jpl.nasa.gov/atlas/atlas_index.cfmhttp://planetquest.jpl.nasa.gov/widget.cfmhttp://planetquest.jpl.nasa.gov/widget.cfmhttp://planetquest.jpl.nasa.gov/atlas/atlas_index.cfmhttp://exoplanet.eu/7/24/2019 Planets Beyond the Solar System1
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Mass? Size? Length of year?
Temperature? Composition?
Atmosphere?
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Questions to consider
One of Jupitersmoons, Callisto, orbits Jupiter
in a path of radius 1,880,000 km. Given that
Callisto has an orbital period of 16.7 days,what is Jupitersmass?
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Solution
One version of KeplersThird Law is M=a3/P2
where P is the orbital period in years, a is in
AU, and M is in solar masses. Converting to
the appropriate units gives P = 0.046 years,a = 0.127 AU, and M = 0.00098 solar
masses or 1.9 x 1027kg.
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Questions to consider
A typical comet contains about 1 x 1013 kg of
ice (water). There are approximately 2 x 1021
kg of water on Earth. Assuming this watercame from asteroid impacts with the Earth,
how many comets would have to hit the Earth
in a time of 500 million years in order toaccount for this water.
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Solution
2 x 1021kg/1013kg water per comet = 2 x
108comets. This is about 1 comet every 2.5
years!
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When using the radial velocity method, it is
easier to detect planets around low mass
stars. Explain why.
When using the radial velocity method,
planets with smaller orbits are easier to detect.
Explain why.
Questions to consider
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Solution
Considering the conservation of momentum,the smaller the star compared to the planet, themore effect the planet will have on it.Therefore, the changes in the stars radial
velocity will be larger and easier to observe.
Planets with smaller orbits have highervelocities than planets further away. Again,
considering conservation of momentum, if theplanets velocity is larger, the stars radialvelocity will also be larger and easier toobserve.
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A planet transits in front of a star. As it does,
the observed brightness of the star dims by a
factor of 0.002. Approximating the planet and
the star as circles, and given that the radius of
the star is 400,000 km, what is the radius of
the planet (in km)? Compare this to the
diameter of the Earth. Compare this to thediameter of Jupiter.
Questions to consider
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Solution
The factor of dimming is the ratio of the disk
area of the planet to that of the star.
Therefore, 0.002 = (pi)r2/(pi) (400,000)2.
r=17,889 km. Since the Earthsdiameterisapproximately 13,000 km, this is about 2.75
times that of the Earth. Since Jupiters
diameter is approximately 143,000 km,Jupiter is about 4 times larger.
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Do you believe that extraterrestrial life exists?
Why?
Questions to consider
Q i id
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What do you think would be the effect on
Earth if life was found elsewhere in the
Universe? Write down at least three answers.
Questions to consider
Wh th fir t l t
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When was the first exoplanet
discovered?
Wikipedia adopts the exoplanet gamma
Cephei b as the first-discovered exoplanet,
citing the date 1988, which is the date of the
claim, not of confirmation (scientific paper:Campbell et al. 1988.)
Officially, the accepted date of the
confirmation is 2003 (scientific paper:Hatzes et al. 2003).
How many planets in other solar
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How many planets in other solar
systems have been found?
Since the latest number of confirmed
exoplanets changes almost daily, here I will
show you the most reliable way to find the
number of extrasolar planet.
Go to the Extrasolar Planets Encyclopedia
catalog page and read the line immediately
above the data table.
How many alien solar systems have
http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/7/24/2019 Planets Beyond the Solar System1
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How many alien solar systems have
been found?
The number of alien solar systems found
changes by the week, almost daily.
Go to the Extrasolar Planets Encyclopedia
catalog page and near the top of the page
you will see, right above the table, three
numbers
What is the nearest exoplanet to
http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/http://exoplanet.eu/catalog/7/24/2019 Planets Beyond the Solar System1
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What is the nearest exoplanet to
Earth?
Currently, the nearest claimed exoplanet to
Earth is alpha Centauri B b, and as its name
suggests, it resides in the nearest star
system to Earth (which is a binary). Thedistance to Earth is about 4.24 light years,
and the planet orbits with a period of 3.2357
Earth days, very close in to the star alphaCentauri B (only 4% of the Earth-Sun
distance).
What is the farthest exoplanet from
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What is the farthest exoplanet from
Earth?
Currently there are two exoplanets that qualifyas being the farthest from Earth. They are intwo different star systems and go by the rathertedious names of SWEEPS-04and SWEEPS-11.
They are both located at about 27,700 lightyears from Earth, which means that it wouldtake light about 27,700 years to travel fromEarth to either planet. For a spacecraft travelingat 20,000 miles per hour (which is achievablealready), it would take about over 930 millionyears to get to the planets from Earth.
What telescopes and space missions
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p p
are used to observe exoplanets?
NASA mission Kepler
European mission CoRoT,
(Co
nvection,Ro
tation, andTransits.)
Hubble Space Telescope (HST),
Infrared missions Spitzer and
Herschel.
Numerous ground-based telescopes
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What is a transiting exoplanet?
A transiting exoplanet is a planet (outside
our solar system) whose orbital motion is
oriented in such a way that observers on
Earth will see the planet periodicly eclipseit's parent star, blocking a tiny fraction of the
light from the star.
Summary
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Summary
more than 1000 extrasolar planetsknown
today the smallest one has about 100 timesthe
mass of the Earth
only planets with orbital periods of a few dayshave circular orbitslike in the Solar System
additional detection methodsmight reveal a
more diverse population of planets, among
them potentially also systems that moreclosely resemble our Solar System(or not!)
at least small planetsseem to be verycommon around solar-like stars
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THANKS