ASTR-1010ASTR-1010Planetary AstronomyPlanetary Astronomy

Day - 39

Course AnnouncementsCourse AnnouncementsHomework Chapter 12: Due Wednesday April 28.

Homework Chapter 21: Due Wednesday April 28.

-this is extra credit.

Observatory Visit and Virtual Observations reports are due Wednesday - 4/28/2010

Exam 4 and “Final”: Friday, April 30 – 1030 am

Next Spring (2011) ASTR-3040 Astrobiology

Extrasolar PlanetsExtrasolar Planets

Most of the extrasolar planets discovered to date are quite massive and have orbits that are very different from planets in our solar system

Astronomers have discovered planets orbitingAstronomers have discovered planets orbitingother starsother stars

• Geoff Marcy is using the 10-meter Keck telescope in Hawaii to measure the Doppler effect in stars that wobble because of planets orbiting around them

• So far, he and other teams have found more than 100 extrasolar planets

How do you Find Exo-Planets?How do you Find Exo-Planets?

• 3 Methods– Radial velocity shifts of the parent star– Direct Imaging– Transits

Finding Extrasolar PlanetsFinding Extrasolar Planets

• The planets themselves are not visible; their presence is detected by the “wobble” of the stars around which they orbit

Radial VelocityRadial Velocity

11stst Direct IR Images Direct IR Images

11stst direct Optical Image direct Optical Image

A TransitA Transit

13

UUSINGSING P PHOTOMETRYHOTOMETRY TOTO D DETECTETECT P PLANETSLANETS

• TransitsPlanet crosses line of sight between observer and star and blocks a small amount of light from the star

Transit of Mercury in 2003

Transit of HD 209458 observed with HST

Eras in the UniverseEras in the UniverseIn the standard model, there are several steps

from early times to the modern universe:• Physical forces established.• Era of photons, electrons, positrons.• Antimatter annihilates matter, leaving many

photons and a little normal matter.• Matter and photons cooled. Atomic nuclei

formed (Big Bang nucleosynthesis).• Recombination: atoms, galaxies, stars.

Future of the UniverseFuture of the Universe

• The universe will probably expand forever.

• In 1014 yr, stars die out, leaving white dwarfs, brown dwarfs, neutron stars.

• In 1039 yr, normal matter decays, leaving only black holes.

• In 10100 years, even largest black holes will evaporate.

Searching for Extrasolar PlanetsSearching for Extrasolar Planets

• This chapter primarily deals with searching for extrasolar planets and the techniques for finding them.

Most of this information is available in the text and various sites on-line, such as:

http://en.wikipedia.org/wiki/Extrasolar_planet

Motion of Extrasolar PlanetsMotion of Extrasolar PlanetsLecture Tutorial Lecture Tutorial pg. 117pg. 117

• Work with a partner!

• Read the instructions and questions carefully.

• Discuss the concepts and your answers with one another. Take time to understand it now!!!!

• Come to a consensus answer you both agree on and write complete thoughts into your LT.

• If you get stuck or are not sure of your answer, ask another group.

Main Sequence Lifetimes

2900.0110.21

530.150.67

101.01.0

1.1142.0

0.0152,50017.5

Lifetime inbillion years

Luminosity (L)Mass (M)

Life, the Universe, & EverythingLife, the Universe, & Everything

• Evolution is a normal consequence of physics.

• If a self-replicating molecule ever forms, then complex structures will arise.

• Reproduction via heredity is not perfect; there are always mutations.

• Natural selection: well-adapted molecules (or organisms) will have more surviving offspring than less well-adapted ones.

Are We Alone?Are We Alone?Estimate the number of advanced civilizations

using the Drake Equation. Multiply:

• number of stars in our galaxy

• fraction of stars with planets

• average number of planets per star

• fraction of planets with life

• fraction that develop advanced technology

• Result is the likelihood such planets exist today.

The Drake EquationThe Drake Equation

• We know several numbers in the Drake equation, particularly the astronomical ones.

• For others, we have to guess.• Optimistic values: nearest civilization only 40

light-years away.• Pessimistic values: distance is 30 million ly.

The Drake EquationThe Drake Equation

• 1961 – 1st SETI conference, Green Bank, WV

• Number of civilizations in our galaxy (or the Universe at large) from which we could potentially get a signal.

• Does NOT give a definitive answer.

• Rather, it lays out the factors that are important in determining this number.

The Drake EquationThe Drake Equation

• Number of Civilizations = NHP

X flife

X fciv

X fnow

• NHP

-Number of habitable planets in galaxy

• flife

-Number of habitable planets that have life

• fciv

-Fraction of life-bearing planets where a

civilization capable of IS communication at some time has arisen.

• fnow

-Fraction of habitable planets with civilization

now, not in the past.

Concept Quiz –Concept Quiz –Life in the UniverseLife in the Universe

Even if there’s a very low chance that any one planet has life on it, there may be many advanced civilizations because …

A. There are billions of billions of stars in the universe.

B. Simple life inevitably leads to complex life.

C. We know that Earth-like planets are common in our galaxy.

4 Metabolic Classifications 4 Metabolic Classifications

• Based on energy and carbon acquisition.

• 1. Photoautotrophs

• 2. Chemoautotrophs

• 3. Photoheterotrophs

• 4. Chemoheterotrophs

Is Intelligence Widespread?Is Intelligence Widespread?• If life is widespread, what about intelligence?

• SETI is only successful if THEY communicate.

• Homo sapiens have only started to understand the environment and explore the cosmos in the last <500 years.– Suggests a long period of evolution is required to

produce technologically intelligent creatures.– Chance events

• body plans in Cambrian explosion• K-T extinctor

Convergent EvolutionConvergent Evolution

• The tendency of organisms of different evolutionary backgrounds that occupy similar ecological niches to resemble each other.– Large marine predators – dolphins & sharks– Eyesight (eyes evolved eight times).

Encephalization Quotient (EQ)Encephalization Quotient (EQ)

• Raw brain power based on brain mass.

• Simple measure

• EQ = 1 line – general intelligence

• Above line – capable of elaborate behavior

• Below line – less mentally agile

Evolution of IntelligenceEvolution of Intelligence• Humans don't have the largest brains.

• Is the largest in relation to body mass.

Early SETIEarly SETI

• Marconi (1874-1937)

• Tesla (1856-1943)

• Both claimed to have heard aliens on the radio.– Probably “whistlers”

• Low frequencies which don't penetrate atmosphere.

Modern SETI - OriginsModern SETI - Origins

• 1959 – Cocconi & Morrison – Cornell Univ.

• Galaxy is older than solar system, so could be civilizations around linger than ours.

• Band –Frequencies receiver is sensitive to.

• Bandwidth – a particular freq. in the band.

• Governed by how much information is transmitted.

SETI - TodaySETI - TodayCategories of Signals

1. Local communications on other world.

2. Communications between home world & other site.

3. Intentional signal beacons. (Project Ozma)

In theory, SETI can detect all three types.

26m dish at NRAO-Green Bank

Our Own SignalsOur Own Signals

• Broadcast in ~1950, just past 50 ly distance.– High power, high-frequency TV– > 2000 stars in this volume.– Star map

A SignalA Signal

Look for: repetition, prime numbers …1974 – signal sent to M13 (bad choice in hind sight). – 21,000 ly distant.

SETI - TodaySETI - Today

• Current SETI projects

Radio –vs.– OpticalRadio –vs.– Optical• Radio is a logical choice since we developed

radio capability early (didn’t everyone?)

• Dust blocks light in the denser parts of the Galactic plane.– Limits our view to a few hundred parsecs.– Not as big an issue today.

• But how?– Laser pulses - doesn’t everyone know Morse code?– Lick – 500 ly search distance– Harvard also has a project going.

ArtifactsArtifacts• 2001: A Space Odyssey

• The TMA is clearly not natural.

ArtifactsArtifacts• Parking

spaces – Lagrange points

• Manufacturing plants.

Types of CivilizationsTypes of CivilizationsNikolai Kardashev – 20th century

Planetary (Type I) – use resources of home planet.

Stellar (Type II) – corral resources of home star.

Galactic (Type III) – employ resources of entire galaxy.

We’re in the first category.What would be the hallmark of the third?

“Any sufficiently advanced technology is indistinguishable from magic.”

– Sir Arthur C. Clarke

Type II CivilizationsType II Civilizations• Dyson Sphere

Freeman Dyson

• Could detect the IR radiation

Big QuestionBig Question• What if we succeed in finding another civilization?

– Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence

Jill Tarter at Arecibo

Sistilli NASA experience

UFOsUFOs

• Project Bluebook

• Day the Earth Stood Still• War of the Worlds• Mars Attacks

Evidence of VisitationEvidence of Visitation

• Roswell, NM• July 8, 1947• 2009 Conference

Evidence of VisitationEvidence of Visitation• Crop Circles• Abductions

“Extraordinary claims

require extraordinary

evidence.”

- Carl Sagan

Ancient Visitations?Ancient Visitations?• Nazca Line Drawings in

Peru, ~2000 years ago.• Mayan pyramids• Easter Island heads

Fermi ParadoxFermi Paradox• If we're not special, then there should be older

civilizations in the galaxy. Where are they?

• Von Neumann machines – self replicating.

• Would other civilizations try to colonize the galaxy?– Coral model– 10% c, 150 years to 5ly– Entire galaxy in 10 Myr– 100 Myr at 1% c

Motives to ColonizeMotives to Colonize

• Humans want to explore. Are we unique?• Extinction-proof civilization• Population control? - Not likely.

Fermi Paradox - SolutionsFermi Paradox - Solutions1. We are alone, therefore we are it.

2. Civilizations are common – but no one has colonized the galaxy.A. Technological difficulties.

B. Sociological considerations.

C. Self-destruction.

3. There is a galactic civilization – they just don't want to deal with us.Zoo hypothesis

Sentinel hypothesis