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Unformatted text preview: Recap Extraterrestrial Life Recap Extraterrestrial Life Give 4 characteristics of life. What are the extremophiles ? What is the habitable zone ? Where could life exist in our solar system ? Extraterrestrial Life (II) Extraterrestrial Life (II) ExtraSolar Planets SETI and Drake’s Equation Extraterrestrial Life Colonizing the Universe Introduction Introduction SETI Search for ExtraTerrestrial Intelligence, a project launched by the late Carl Sagan. Drake’s Equation quantifies the chances of success for SETI. ExtraSolar Planets (I) ExtraSolar Planets (I) In the recent years 527 extrasolar planets have been detected. The nearest are about 10 lightyears away. They cannot be seen directly with the current telescopes because their light (actually the star light that they reflect) is outshone by the stars they orbit. Direct measurements were made possible through IR observations: 2008 Fomalhaut b (2 or 3 others) Indirect observations include: Astrometrics (deviations from the normal movement), wobbling around the path detection, use of Doppler measurements Transit photometry (minimum in brightness as planet passes in front of the star), or the addition of planetary reflected component Habitable Zone for Various Stars Habitable Zone for Various Stars As the mass of the star increases the habitable zone moves further from the star. ExtraSolar Planets (II) ExtraSolar Planets (II) Kepler satellite in 2010 produced indirect evidence for 1235 new planets, of which 54 were in the habitable zones and 68 of Earth size. At least one (Gliese 581 d) was Earth size and in the habitable zone. These results have to be confirmed. But these observations allowed for speculations that there are about 50 billion planets in our galaxy and probably millions are in the habitable zone. In the current observations most planets were within the Jupiter orbit and larger than Jupiter (there are at least two models to explain the drift towards the star of these planets). Current technology allows the observation of only about 10% of the planets, which means that 90% of the extrasolar planetary systems are more like our own. SETI SETI SETI has been emitting radio messages out into the Universe for decades in the hope of communicating with extraterrestrial intelligence. The absence of responses make us wonder about the chances of success. Arecibo SETI Details SETI Details What types of communication ? What to communicate in the beacons ? Radio and TV programs, signals used for communications with spaceships (last 60 years) Intentional signal beacons (strong, narrow bands) Binary Numbers (two wavelengths) Arecibo Allen Telescope Array (up to 350 dishes each 6 meters in diameter) Radiotelescopes used by SETI Drake’s Equation Drake’s Equation Drake’s equation determines the number of civilizations in the galaxy which might be capable of insterstellar radio communication. The equation is: N=R*fp*ne*fl*fi*fc*L, where R is the average rate of star formation, fp is the fraction of stars with planetary systems, ne is the number of planets that have environments suitable for life, fl is the fraction of planets that have life, fi is the fraction that have intelligent life (on Earth it took millions of years of evolution and it created one out of a billion of species), fc is the fraction that developed the technology L is the average lifetime of a technological civilization. The Fermi Paradox The Fermi Paradox Where is everybody ? The need for heavy elements to create life and the danger of supernova radiation may reduce the galactic habitable zone Colonization of the galaxy is difficult (technology, sociological considerations) The “zoo hypothesis” – advanced civilizations do not interfere with our evolution Intelligent Life Intelligent Life Defining intelligence is a difficult task. Dolphins, horses and even insects possess some degree of intelligence. But only humans acquire and apply knowledge in building technologies. Intelligence evolved because it was favored by natural selection. It took millions of years to create one intelligent specie out of a billion and that makes some biologists (like G.Clayford of Harvard) say that the repeat in other planets is very improbable. Conclusions on ET Life Conclusions on ET Life SETItype work is very slow. The chances of intelligent ET life in our galaxy are probably good but we do not have the value of Drake’s N. Hard to speculate on how ET life looks like. Apart from frequent and dubious claims (such as UFOs photos) there is little evidence that ET life exists. We do know that the chances of finding primitive forms of life in our solar system are good. Colonizing our planetary system Colonizing our planetary system (I) Even if we find no life out there, we could colonize the Universe, or at least our galaxy. Our Moon was already visited, but it does not contain the elements and the chemicals to sustain life. If a colony is setup on our Moon it would be completely dependent on Earth supplies. Mars, on the other hand, has all the elements to build a colony and bred plants. Colonizing our planetary system (II) Colonizing our planetary system (II)
Many scientists favor the colonization of some asteroids, such as Ceres which has a diameter of 967 km (half of Pluto). These asteroids can be mined for valuable metals and chemicals. The NASA animation on the right shows a probe orbiting Eros, the second largest asteroid. The colonization needs solutions to the physiological effects of zerogravity, or the creation of artificial gravity. Terraformation Terraformation Terraformation is the science of making another planet/asteroid habitable. For Mars it would imply increasing the atmospheric pressure by 200 times (to be thicker than our due to its lower gravity) and the temperature by 60 degrees. NASA concluded that this is not only feasible but also plausible. Venus is the only other candidate. But with its 482 degrees at the surface and an atmosphere 92 times thicker than Earth, this task will be much more difficult than with Mars. Jupiter is a gas giant type planet (no surface for life to grow on), but its moons (such as Europa) are interesting candidates for terraformation. Colonizing our galaxy Colonizing our galaxy In our galaxy there are about 200 billion stars and if one travels at about 25% of the speed of light it would take about 300,000 years to go across the galaxy. Can it be done ? According to Einstein’s relativity, if one travels at close to the speed of light time will slow down for the traveler Today the travel speeds are very low. New technologies are needed to speed up the interstellar travel. The colonization could be done through small “jumps” (of a few lightyears), which would then selfreplicate ships using local sources of helium3. Nuclear fusion with helium3 isotopes could power the spaceships. For instance our Moon and Uranus have large quantities of helium 3. Colonizing other galaxies Colonizing other galaxies Today this is hard to imagine because it involves flights over distances of millions of lightyears. Science fiction invented the “warp speed”, ie the creation of mini black holes used for spacetime travel. Theoretically this is possible but technically far from our capabilities. ...
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This note was uploaded on 05/03/2011 for the course NATS 1740 taught by Professor Hall during the Spring '10 term at York University.
- Spring '10