planets beyond the solar system1

7/24/2019 Planets Beyond the Solar System1

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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?


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?


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/


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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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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.



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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.



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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?


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.


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/


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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/


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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

planets beyond the solar system1

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