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Dark Matter Dark Energy The History of the Universe More of the History of the Universe Life on Earth and Beyond More life on Earth and Beyond $100 $100 $100 $100 $100 $100 $200 $200 $200 $200 $200 $200 $400 $400 $400 $400 $400 $400 $600 $600 $600 $600 $600 $600 $800 $800 $800 $800 $800 $800 $1000 $1000 $1000 $1000 $1000 $1000 $2000 $2000 $2000 $2000 $2000 $2000 Does observational evidence suggest there is more dark matter than visible matter in the Universe? YES What does MACHO stand for? Massive Astrophysical Compact Halo Object What are some examples of MACHOs? Black holes, brown dwarfs, rogue planets, black dwarfs, basically anything made of normal matter that is not emitting light What does WIMP stand for? Weakly Interacting Massive Particle What are some examples of evidence for dark matter? Rotation curves of spiral galaxies, confinement of hot gas in clusters, motions of galaxies in clusters, gravitational lensing What percentage of the Universe is made of WIMPS? About 22% MACHOS make up 4% and ordinary matter makes up 1% Why did dark matter form structures before ordinary matter in the early Universe? Because it is not affected by radiation (light) that prevented other matter from clumping Does dark energy makes up most of the Universe YES Evidence for dark energy primarily comes from Type Ia supernovae The effect of dark energy on the expansion of the Universe is that the expansion is _____ Accelerating (getting faster and faster) What percentage of the Universe is dark energy? 73% is dark energy The rest is 26 % dark matter (4% MACHOS, 22% WIMPS) and 1% ordinary matter Do scientists know the source of dark energy No! This is an active area of research Did the Hubble Space Telescope play a key role in the discovery of dark energy? Yes! It was observations of distant Type Ia Supernovae with Hubble that helped show the accelerating expansion of the Universe What open question about Type Ia Supernovae might change some of the predictions about dark energy? Whether all Type Ia Supernovae have the same cause. This matters because it would change the assumptions about the luminosity of the supernovae which are used to get distances. All Type Ia Supernovae definitely come from white dwarfs but it is not known whether all involve accretion from a nearby star, merging with another white dwarf, or either/or! What is the age of the Universe? 13.8 billion years old What are the four fundamental forces? Gravity, weak, strong, electromagnetism What forces are united in the Grand Unified Theory? Electromagnetism. strong, and weak forces What was the percentage of elements after the era of nucleosynthesis? 25% He, 75% H, with trace amounts of Li, Be, and B What is the Cosmic Microwave Background and what NASA mission most recently studied it? The Cosmic Microwave Background is the light from hot gas in the earliest moment when light could travel through the Universe, 380,000 years after the Big Bang. The NASA Mission was called WMAP. Why couldn’t light travel before the era of atoms? The light was scattered by particles, mostly free electrons When did the first stars form? About 300 million years after the Big Bang Why didn’t heavy elements like oxygen form in the early Universe? Because collisions with photons and atoms prevented the formation of the heavier elements Light can be converted into mass by the process of _____. Particle/antiparticle production Why is the Universe made of matter, rather than antimatter? There was a slight excess of matter over antimatter. The amount of excess was very small, less than 1%. When did cosmic inflation happen? Between the GUT and electroweak eras, roughly 10-35 s after the Big Bang Why does the cosmic microwave background show up in microwave wavelengths Because it is redshifted by the expansion of the Universe How is dark matter responsible for structure in the Universe? In the early Universe, radiation smoothed out clumps of matter, but dark matter was not affected and clumped together before ordinary matter. Later, these dark matter clumps attracted ordinary matter, leading to today’s structure. The early Universe’s mass density was predominated by matter or by light? Which one? Light What are three basic needs of life? Liquid (like water but could be something else), materials for complex chemistry (like carbon but could be something else), energy (from a star or geothermal or other source) How long did life take to begin on Earth? Less than 1 billion years, as little as 300 million years! What is a habitable zone? The region around a star where liquid water can exist? Which of these is not a basic property of life? Organization Using energy, Growth Adaptation Reproduction Higher Intelligence Homeostasis Responding to stimuli Higher Intelligence Is Earth the only place with liquid water in the Solar System? No! Mars shows signs of liquid water (seasonally probably), and Enceladus has water below a frozen surface. It is also possible that Europa, Ganymede, and Callisto have liquid oceans below their surface. What would be the source of Europa’s warmth to keep a liquid ocean? Tidal forces from Jupiter’s strong gravitational pull. Why have we found more Earth-like planets in the habitable zone around small cool stars? Because the habitable zone is closer to these stars and our methods of detecting planets (changes in luminosity and motion of the star) make it easier to detect small planets around stars like this compared to small planets around bigger stars Would Europa have a larger planetary habitability index or Earth Similarity Index? Planetary Habitability Index. This depends on chemistry, an energy source, and the ability to hold a liquid solvent like water. The Earth Similarity Index only depends on physical similarity to Earth. The meteor ALH84001 is special because ____ This is a meteor from Mars (found in Antarctica) that has rod-shaped structures that could be nanobacteria. These are not living organisms but structures that suggest the ingredients for life once existed on Mars. Why are extremophiles important for the study of life beyond Earth? Because they show how life might exist in conditions very different from Earth. For example Antarctic sub-glacial lakes could show what life (if it exists) in Europa’s oceans might be like Which mission carries a plaque showing information about Earth in case aliens find it? Pioneer 11 What is SETI and is anyone encouraged to help? The Search for Extraterrestrial Intelligence. Everyone is encouraged to help, including amateur astronomers. How does the Drake equation answer the Fermi Paradox? It provides a way of measuring the number of civilizations in the galaxy. If the equation comes out with a low number, than the reason that we haven’t found/heard from aliens is that there aren’t any…if the number is high, the paradox still exists. Which values in the Drake equation do astronomers have a decent grasp of? R*: The number of stars that form in the galaxy (5-7) Fp: the fraction of stars with planets (0.5-1) Ne: the number of stars with habitable places is still not known too well All the other numbers are open questions!