Life in the Universe. Key Concepts: Lecture 35: Admin. 11/21/17. All Formulae (for final):

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1 Admin. 11/21/17 Key Concepts: Lecture 35: 1. Class website 2. Optional Discussion sections: Tue. ~11.30am (period 5), Bryant 3; Thur. ~12.30pm (end of period 5 and period 6), start in Pugh 170, then Bryant 3 [if just a small group we move to my office Bryant]. 3. Office hr: today only: Tuesday pm; Wed pm, Bryant 302 (but me if coming on Wed.). 4. Homework 11: is due Wed. Nov. 29th 11.59pm via Canvas e-learning under Quizzes 5. Reading this week: Ch. 0-3, , 5-16, 17, 18, Observing project deadline was Thur. Nov. 2nd Final exam - Tue. 5th Dec., in class. (about 1/2 the questions on material since midterm 2).You are NOT allowed calculators: questions will only require simple arithmetic. You will be given a list of all formulae used in the class (see next slide). Exam is multiple choice format on a scantron so bring a pencil. Bring your UF ID. In class review session on Thur. 30th Nov. - bring questions for discussion. 8. me Astro-news, jokes, tunes, images: ast1002_tan-l@lists.ufl.edu 9. Printed class notes? Name tags? Life in the Universe: Origin of Life The Drake Equation Speed = distance / time Angular size: θ = size / distance Kepler s 3rd Law: P 2 = a 3 [ Newton s version of Kepler s 3rd: P 2 a 3 /(m 1 +m 2 ) ] Newton s 2nd Law: F = m a Newton s Law of Gravity: F m 1 m 2 / r 2 Density = mass / volume Volume of a sphere = (4/3)πr 3 Surface area of sphere = 4πr 2 Angular momentum mass x rotation rate x size 2 Frequency: f = 1/Period Speed of wave (light) = frequency x wavelength: c = f λ Energy of Photon: E = h f Wien s Law: λ max = 0.29cm / T(K) Parallax distance: d = 1/ p Flux: F = L / (4πd 2 ) Stellar Luminosity: L = 4πr 2 σt 4 Doppler Shift: Δ λ / λ = v / c Main Sequence Luminosity: L M 4 Light Gathering Power = Area x Exposure time Resolving Power (angular resolution) = 0.25 λ (microns) / diameter (m) Stellar lifetime M / L M -3 Mass-Energy Equivalence E = m c 2 Orbits in Galaxies: M galaxy + M sun a 3 /P 2 a v 2 Hubble s Law: v = H 0 d Drake Equation: N tc = R sf f wp N sfl f lb f il f ts L t All Formulae (for final): Life in the Universe What is life? How did life arise on Earth? Are we alone? The Drake Equation How common are habitable environments? How do we find Extrasolar Planets? The number of technological civilizations in the Galaxy Practicalities of communication and interstellar travel

Definition of Life It can react to its environment It can grow and take nourishment from its surroundings It reproduces - passing along some of its characteristic to its offspring: HEREDITY It has

8 billion years old Earth Sterilizing impacts every ~100,000 years ending about 3.

2 Definition of Life It can react to its environment It can grow and take nourishment from its surroundings It reproduces - passing along some of its characteristic to its offspring: HEREDITY It has the capacity for genetic change, allowing evolution from generation to generation, mediated by Darwinian selection pressures. The Origin of Life on Earth Oldest surface rocks found - ~3.8 billion years old Earth Sterilizing impacts every ~100,000 years ending about 3.8 billion years ago Rock vapor from impact circles Earth for months Oceans are evaporated with each impact First fossils: billion years ago Archaea - cyanobacteria which can live in extreme conditions Archaea today in hot springs & salt ponds Life seems to have started in <100 Million years under poor conditions Unity of Life on Earth All living things on Earth are composed of organic material (C, H, O, N, P, S) Carbon is abundant and can form complex string molecules All life on Earth uses replicating strings of DNA (deoxyribonucleic acid) (& RNA [Ribonucleic acid]) These are used to construct amino acids, which link together to form more complex molecules of proteins. Can Life Form this Fast? Miller-Urey experiment (1953) Primordial soup (Water, Methane, CO 2 & Ammonia) Energize it with a spark (simulates lightning) or UV light (used in later versions of the experiment) After a few days contained many amino acids Not a living organism, but on the right road

living cells but not living Cell-like structures can form History of Life on Earth Panspermia History of Life on Earth Controversial

3 Can Life Form this Fast? Amino acids arrange into blobs Walls pass small molecules More complex ones are formed inside which cannot leave Structures similar to living cells but not living Cell-like structures can form History of Life on Earth Panspermia History of Life on Earth Controversial (most scientists don t believe it is correct) idea that life may have originated elsewhere and was brought to Earth Gets around problem of having life form in a hostile environment But life must survive in space for long periods High gamma ray flux

$fraction of stars with planetary systems N sfl = average number of planets suitable for life f lb = fraction of habitable planets where life arises f il = fraction of life-bearing planets where$

4 The Drake Equation N tc = R sf f wp N sfl f lb f il f ts L t N tc = number of technological civilizations now present in Milky Way R sf = rate of star formation over lifetime of the Galaxy f wp = fraction of stars with planetary systems N sfl = average number of planets suitable for life f lb = fraction of habitable planets where life arises f il = fraction of life-bearing planets where intelligence evolves f ts = fraction of intelligent-life planets that develop technology L t = average life time of a technological civilization Further reading: The Ancestor s Tale - Richard Dawkins

Star Formation Rate of the Galaxy In the Milky Way galaxy stars form at the average rate of 10 stars per year This average is determined over

$young stars 50% - 100% of solar-type stars have enough mass in their disks to form planets what fraction actually forms planets is uncertain$ from just these data Need direct search (see next lecture) Fraction of stars with planets Theoretically we expect all stars to form with

from just these data Need direct search (see next lecture) Fraction of stars with planets Theoretically we expect all stars to form with

5 Star Formation Rate of the Galaxy In the Milky Way galaxy stars form at the average rate of 10 stars per year This average is determined over the lifetime of the Milky Way: about stars have formed over the last years. Planets in Formation Planetary systems are easier to detect in formation rather than after material has gathered into planets disks around young stars 50% - 100% of solar-type stars have enough mass in their disks to form planets what fraction actually forms planets is uncertain from just these data Need direct search (see next lecture) Fraction of stars with planets Theoretically we expect all stars to form with disks, where planets may form. However, star and planet formation are complicated processes and we do not yet have a way to predict how often planetary systems form. Therefore, we need to look for the planets!

Why is it hard to find planets?

Why is it hard to find planets? Admin. 11/28/17 1. Class website http://www.astro.ufl.edu/~jt/teaching/ast1002/ 2. Optional Discussion sections: Tue. ~11.30am in Bryant 3; Thur. ~12.35pm, start in Pugh 170, then Bryant 3 3. Office hr: