Other Interesting Aspects of Astronomy

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Other Interesting Aspects of Astronomy. I. Formation of the Earth. Around 4.7 billion years ago, a young nebula in the middle of a Milky Way spiral arm existed Nebulae are full of gas and dust, the birthplace of stars - PowerPoint PPT Presentation


Other Interesting Aspects of Astronomy

Other Interesting Aspects of Astronomy1

I. Formation of the EarthAround 4.7 billion years ago, a young nebula in the middle of a Milky Way spiral arm existedNebulae are full of gas and dust, the birthplace of starsA large clump of gas and dust coalesced in the nebula and accreted more mass over timeIt began spinning, and pulled some matter around it in a disk2

Formation of the EarthThe matter in the disk began accreting into clumpsVery large clumps attracted a lot of matter to them and gained massThey became planetsLess successful (smaller objects) included comets and asteroidsEventually, as most of the mass went to the sun, it spun up even faster and the objects in the disk sped up and rotated too quickly for mass to accrete. Then, collisions and ejection occurred.3

Formation of the EarthThe Earth became one of the inner (terrestrial) planets that escaped ejectionIt formed around 4.6 billion years agoWe estimate its age from meteorites, which are largely unchanged from formation, as plate tectonics on the Earth destroy most older rocksThe Early earth was molten, with hydrogen and helium in its atmosphereMoon formed by a Mars-sized object (Theia) hitting earth 4.5 billion years ago and flinging a lot of the mantle into space


Formation of the EarthThe Earth had cooled since its formation and was able to develop oceans beginning during the heavy bombardment (3.8 4.1 billion years ago) Lighter gases (hydrogen and helium) had already escaped Earths gravity and were lost to spaceWater vapor in the atmosphere from volcanic outgassing and water vapor coming from asteroid and comet impacts condensed in the atmosphereIt precipitated very heavily and eventually the Earth had oceans5

II. Earth is UniqueBasically, Earth has kept water in three phases (not too hot like Venus or too small to keep it like Mars) for most of the past 4 billion years, particularly most of the past 1.5 billion yearsThe sun is a single, very stable star, with a long lifeThe moon has helped stabilize Earths axial tilt, which greatly reduces climate fluctuationsJupiter is at just the right distance to deflect the vast majority of comets and asteroids from earth-approaching orbits, and no gas giants have made it more dangerous since the period of heavy bombardment, and Jupiter is far enough that it doesnt disrupt Earths orbit6

Earth is UniqueWater can dissolve organic (carbon-based) compounds, necessary for lifeWater has one of the highest specific heats of any known substance and also high value of latent heat, and this stabilizes climateLiquid water expands as it cools (rare occurrence), which greatly reduces the speed of freezingCarbonic molecules can dissolve or stay intact in a water solution; carbon can create covalent bonds with many nonmetals, and, with water, can form carbohydrates, import for other biochemical reactionsNo one has been able to think of a substance which can support life nearly as well as water7

Earth is UniqueWe are situated in a relatively calm part of the galaxy, with minimal violence subjecting Earth from outside sourcesNo nearby supernovae or close solar-system directed ray bursts have roasted our planet for at least 4 billion yearsAs such, the Earth has had an incredibly ideal period for producing carbon-based life the past 4 billion yearsMassive enough planet to retain atmosphere and for iron and heavy metals needed for skeletal structure and support/protection of head and large brainsEarth was able to store carbon dioxide in rocks, while sufficient plants allow for adequate oxygen and ozone production needed for cellular respirationWe do not know exactly how rare Earths situation is in the universe.8

Earth is UniqueIn addition, assuming that life would try to occur in any halfway conducive environment (big assumption), evolution does not necessarily have a goal regarding what type of life it createsSurvival of the fittest does not mean that intelligent beings capable of manual dexterity (ability to use hands) to form technology is a goal; there are a lot of intelligent vertebrates, and remember vertebrate life is EXTREMELY fragileSo, if life does exist on other planets (probably quite likely), they are not necessarily beings able to ponder and think in an objective, rational, moral, transcendent manner and also utilize tools for advanced technology9

III. The Drake EquationThe past few decades, attempts have been made to quantify the likelihood of life with technology, such as ourselves, capable of contacting other planets, or being detectedN = R x Fp x Ne x Fl x Fi x Fc x LN = number of civilizations in Milky Way that are capable of communicatingR = average rate of star formation in the Milky WayFp = fraction of stars with planetsNe = average number of planets with potential to support life per star having planets (Fp)Fl = Fraction of Ne that develop lifeFi = Fraction of Fl that develop intelligent lifeFc = Fraction of Fl that can release signals of their life into spaceL = length of time Fc actually release such signalswikipedia.org10

The Drake equationN = R x Fp x Ne x Fl x Fi x Fc x LR ~ 10 stars per year formed in our galaxyFp ~ 0.5 ? (half of stars will have planets)Ne ~ ?? (0.1?) planets capable for lifeFl ~ 0.5? Capable planets that develop lifeFi ~ ???? Life becomes intelligent (very small)Fc ~ ???? Life able to communicate (very small)L ~ 10,000 years (communication last for 10,000 years)Fc and especially Fi are probably tiny, just that we dont know how small (.001 each, or 1 x 10-12 each??) wikipedia.org11

What to take awayBeings with technological capabilities similar to humans are a very rare occurrence in the galaxy (and universe)Its not what you see in science fiction!!Most planets certainly do not have themIn fact, it may be possible that we are the only such type of beings which exist on any planet in the universe12

IV. Meteor ShowersMeteors are typically the size of sand grainsThey originate from comets and asteroids, whose orbits happen to cross near Earths orbit and have debris which burns into atmosphereThe small particles burn up in the ionosphere and leave a brightly ionized trail that we seeMore particles earlier on in the solar system, when it was a lot messier13


Meteor ShowersFavor Northern Hemisphere currently by chanceMost activity from mid-October through the first week of JanuaryInterference of clouds or moon can be ruinousParticularly intense displays (> 1000/hour) are called meteor storms-- rare15

Meteor ShowersMeteors visible every clear nightSporadic meteors from random sources and meteors from distinct sourcesConsistent high rates of meteors from distinct sources create the most popular meteor showersMeteor showers have meteoroids with different ages, orbital periods, brightness distributions, rates, angles of hitting earth, speeds, mass distributions, total durations16

Meteor ShowersShower namePeak datesPeak RateBrightnessEver storm?QuadrantidsJan 3~120/hrBrightNoLyridsApr 22~15/hrFaintBarelyEta AquaridsMay 4-6~60/hrBrightNoSouthern Delta AquaridsJuly 27-29~18/hrFaintNoPerseidsAug 12~100/hrBrightNo, but may laterDraconidsOct 9~2/hrFaintYesOrionidsOct 20-22~25/hrBrightNoTauridsNov 2-7~7/hrBrightNoLeonidsNov 18~20/hrBrightYesAlpha MonocerotidsNov 22~2/hrBrightYesGeminidsDec 13~130/hrBrightNoUrsidsDec 22~8/hrFaintPossiblyCombination of IMO rates, P. Jenniskens, E. Lyytinen, and my opinion17

Meteor ShowerTo see a meteor shower well, get well away from a city and its suburbsDo not want any clouds or moon in sky (crescent moon is alright)Typically peak in darkness just before morning twilight begins, when we are face-first in our orbitRadiant must be high in order to see most of meteors18

Meteor ShowersBest four overall for seeing lots of numbers in St Louis area and Northern Hemisphere midlatitudes are the Geminids, Perseids, Quadrantids, and OrionidsGeminid radiant is ideally placed in the sky and the best bet of seeing a high rateRadiant is nearly overhead (maximum number of meteors visible) and is highest well before dawnAlso, a bright shower with fairly long maximum19


V. Meteor StormsSome meteor showers can have intense outbursts called meteor stormsMost storms last typically 1/2 hour or so. Occasionally longer-lived (Leonids and Draconids at times). High density comet trails are typically quite thin.The Leonids, Draconids, Alpha Monocerotids, and Lyrids are all definitely capable. The Ursids, Alpha Aurigids, and June Bootids may be.The Leonids and Draconids are the best known and most consistent (frequent, regular) meteor showers that produce meteor storms.21

Possible upcoming meteor storms for U.S. and Europe.ShowerDatesLikelihoodWhere VisibleMoonBrightnessDraconids10/8/2011GoodEuropeBadFaintDraconids10/9/2018Fairly goodE US and W AtlGoodFaintA. Monocerotids11/22/2019DoubtfulE US and W AtlGoodBrightUrsids12/22/2020DoubtfulE US and W AtlGoodFaintLeonids11/19/2022DoubtfulE US and W AtlBadBrightPerseids8/12/2028MaybeE US and W AtlBadFaintLeonids11/18/2034GoodEuropeGoodFaintLeonids11/19/2034Maybe Europe & E USGoodBrightLeonids11/20/2035MaybeE Us and W AtlBadNot sureDraconids10/10/2037UncertainW AtlGoodFaintLeonids11/20/2037GoodEurope & AsiaBadFaintA. Monocerotids11/22/2043MaybeW. & Cent U.S.BadBrightJune Bootids6/22/2045DoubtfulW U.S.GoodVery brightPredictions based on P. Jenniskens, E. Lyytinen, J. Vaubaillon, M. Maslov, and S. Molau22

Possible Future Meteor StormsBest Bets: 2011 Draconids, 2034 Leonids (moonless), and 2037 LeonidsOther decent chances: 2018 Draconids (moonless), 2028 Perseids, 2035 Leonids, 2037 Draconids (moonless), and 2043 Alpha MonocerotidsAll in table worth a shot if youre in the areaOther storms possible, with some lesser likelihood predictions (not shown) and unknown sources the cause23

Hope you enjoyed this special session!!2425