This document discusses exoplanets and the search for extraterrestrial life. It describes how over 1800 exoplanets have been discovered orbiting stars other than the sun. It explains several methods used to detect exoplanets, including direct imaging, the transit method, astrometry, and radial velocity. It also discusses characteristics of potentially habitable exoplanets and provides details about Gliese 667 Cc, one of the most Earth-like exoplanets discovered. The document then reviews the history of exoplanet detection and outlines some of the earliest projects in the search for extraterrestrial intelligence, such as Projects Ozma and Phoenix.

1. Exoplanets and extraterrestrial life
Silvana Buscemi
Camilo Díaz
Ruth Pérez
Aitor Gallego

2. EXOPLANETS
• Exoplanet: planet that doesn’t orbit the sun,
instead orbits a different star.
• 1800 exoplanets have been discovered.
• Nearest exoplanet to the Earth: Alpha Centauri
Bb.

3. DETECTION METHODS
Direct methods:
1. Direct imaging:
• It is extremely difficult, and in most cases impossible.
• Being small and dim planets are easily lost in the brilliant glare
of the giant stars they orbit.
• It works best for planets that orbit at a great distance from
their stars.
Indirect methods:
1. Transit method.
• When a planet crosses in front of its star as viewed by an
observer, the event is called a transit.
• It can determine the radius of a planet.
• Transits by terrestrial planets produce a small change in a
star's brightness .

5. DETECTION METHODS
2. Astrometry:
• It involves precise measurements of the positions and
movements of stars and other celestial bodies.
• It provides information on the kinematics and physical
origin of our Solar System and our galaxy, the Milky Way.
3. Radial velocity:
• It is based on the detection of variations in the velocity of
the central star
• When the star moves towards us, its spectrum is blue
shifted, while it is red shifted when it moves away from
us.

6. Habitable exoplanets
• The circumstellar habitable zone
• 12 confirmed habitable planets
• Habitable exoplanets are ranked trough their size: terran,
subterran and superterran.
• They are also classified according to their temperature:
hypopsychroplanet if they are below -50c, psychroplanet 0c/-
50c, mesoplanet which is the ideal from 0 to 50c and
thermoplanets which are very hot.

7. Gliese 667 Cc
Gliese 667 cc is the most similar planet to earth that is
scientifically proved to be a possible planet with live as
we know it.
• This planet has about 4 and a half times the mass of
the earth.
• It orbits around the star Gliese 667 C which is a
member of the Gliese 667 triple star system.
• The star Gliese 667 C hosts at least 7 planets and 3 of
those, all rocky planets , are within the habitable zone.
• It is a bit warmer than the earth but complex life could
exist at that temperature.

9. HISTORY OF DETECTION
• Early speculations.
• Confirmed discoveries.
• Unconfirmed Kepler
Candidates.(candidate planets)
• Total planets.

10. EARLY ESPECULATIONS
• Guiordano Bruno. (16th century)
• Isaac newton. (18th century)
• Otto struve. (20th century)

11. CONFIRMED DISCOVERIES
• First published by Bruce Campbell, G.H.A
Walker and Stephenson Yang in 1988. (Gamma
Cephei)

12. CONFIRMED DISCOVERIES
• First definitive detection of an exoplanet orbiting
51 Pegasi star by Michel Mayor and Didier
Queloz. (1995)

13. UNCONFIRMED KEPLER
CANDIDATES
• Alpha Centuri Bb planet in 17 October 2012.

14. What is the SETI? When and how did
this idea began?
• It is the science used to search
the skies for signals from alien
civilizations.
• The idea of SETI began in 1959.
• Giuseppe Cocconi and Philip
Morrison published a paper
discussing the possibility of the
existence of alien civilizations.
• Method of detection: Radio
waves. Why? because they are
capable of traveling the vast
distances between stars
• First search: Project Ozma in
1960.

15. PROJECT OZMA
• It started in 1960, by a young
astronomer named Frank
Drake.
• It was the humanity's first
attempt to detect interstellar
radio transmissions.
• Stars chosen for the project:
• - Tau Ceti in the Constellation
Cetus (the Whale)
• -Epsilon Eridani in the
Constellation Eridanus (the
River).

16. PROJECT PHOENIX
• It was the most ambitious
search for extraterrestrial
intelligence ever undertaken.
• From February 1995 to
March 2004.
• Project Phoenix observed
about 800 stars.
• Where did the project take
place?
-Australia
-West Virginia
-Puerto Rico.
• No ET signals were detected.

17. FERMI PARADOX
• It is the apparent contradiction between high estimates
of the probability of the existence of extraterrestrial
civilization and humanity's lack contact with.
Arguments:
• The Sun is a typical star, and relatively young.
• some of these stars will have Earth-like planets, some of
these planets may develop intelligent life.
• Some of these civilizations may develop interstellar
travel.
• The galaxy can be completely colonized in a few tens of
millions of years.
• Hence Fermi's question, "Where is everybody?"

18. QUIZ for the audience.
Rules:
• First of all the class is divided into the groups
assigned for the PPTs.
• In each group there will be a speaker and
questions will be asked randomly between
the speakers of each group so be prepared!!
• Mr. Cuesta can of course ask questions to
any of you even if you are not speakers if you
are not paying attention.

19. QUIZ.
• 1 What is the SETI?
• 2 Can you explain how it works any of the
detection methods we explained?
• 3 What is the circumstellar habitable zone?
• 4 So according with our explanations is Gliese 667
Cc a terran, subterran or superterran planet?

20. QUIZ
• 5 Did project Ozma or project Phoenix proved
something about extraterrestrial life?
• 6 When was the first exoplanet discovered?
• 7 How many stars did project phoenix observed?
• 8 Do you think it could be anybody out there
after this PPT?