Exoplanets AST 111
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This 0 page Class Notes was uploaded by Ashley Childers on Thursday December 3, 2015. The Class Notes belongs to AST 111 at University of Southern Mississippi taught by Christopher Sirola in Summer 2015. Since its upload, it has received 20 views. For similar materials see General Astronomy in Physics 2 at University of Southern Mississippi.
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Date Created: 12/03/15
Dao the Dragon Most cultures have seen these stars as a dragon or crocodile This is a Babylonian myth about 5000 years old 0 This are the gurines of the god Enlil and his consort Nin Ill 0 O o The original Draco is a creature called Tiamat she is the great great grandmother of Marduk o Tiamat represents the original chaos that gives birth to gods and monsters both Tiamat maks a brief appearance in the book ofJob as the monsters Behemoth and Leviathan o The con ict between Marduk and Taimat is the oldest know written creation story Tiamat and her monster children are at war with the gods Everyone besides Marduk is frightened by Tiamat Marduk offers to slay Tiamat if in return the other gods make him king 0 The others agree 0 He is a sky god so he sends hurricaneforce winds down Tiamat throat 0 Then marduk shoots Taimat with arrows as she Marduk uses Tiamat s body to fashion the Earth 0 To form the celestial poles he nails her skin to the sky Dracto the Dragon is a quotcircumpolarquot constellation for observers in the northern hemisphere Today s North Star is Polaris but a star named Thuban in Draco was the North Star 5000 years ago quotlPrecessj on gotthe 39 l ai f N Pole 1 A 4 I a m quot I I 39 5 I I o The Eart wobles lke a toy top its axis makin a colte circe oce every 26000 years o 39 o This effect is called precession is due mostly to the tides gravity of the sun and Moon 0 Thus the direction of the Earth s axis is slowly but continuously changing o The north pole of the Earth now points near Polaris 5000 years ago the north pole pointed to Thuban 0 14000 years ago the North Star was Vega in Lyra the Harp and will be again 12000 years from now 0 There is some evidence that the ancient Egyptians also acknowledged Thuban as the North Star can be seen in the direction of some of the prymids Thuban 0 this is a close up picture of Thuban its size indicates brightness not its physical diameter the star does not actually have rings or spikes this is an optical illusion 0 Basic properties of Thuban Mass 385x sun Brightness 300x sun Type AC lll Giant 303 light years away magnitude 385 Means quotsnakequot in Arabic The Cat s Eye Nebulas o Is found in the constellation of Draco o It is too dim to see with the naked eye but can be seen with a small telescope o This nebula gas cloud was discovered by William Herschel Same man who discovered Uranus o This picture was taken in 1994 by the Hubble Space Telescope o The Cat s Eye is as a planetary nebula so called because of its colors 0 The star at the core is shedding its outer layer at a rate of 20 trillion tons per second 0 The twisting of the various bubbles may be due to a companion star or to its own rotation o HST observations have aed astronomers to nd its distance amp age 0 This nebula is about 3300 light years away amp about 1000 years old 0 At the center of this nebula is a WolfRayetquot star 0 The core is slowly being exposed as its outer layer ow away 0 The central star is 5 times the mass of the sun but now is slightly lighter It as fated to become a white dwarf Exoplanets 0 One of the most active areas of current research in astronomy is the search for planets in other star systems 0 People have wondered for centuries if planets orbit other stars but the rst exoplanet was discovered only in 1995 51 Pegasi b r3quotrpr 39 39III hEE39qu 2ni39iq 31quot quot i I E3Efi39rq EEhEIEiT39FJ girl i E39Em lg 39 0 One obvios method for ndin an exlanet wuld be to take a picture of it This turns out to be dif cult not impossible since a planet is a million or more times dimmer that its parent star 0 Here is an infrared image of the HD 8799 system The stars image has been electronically removed in order to bring out its 3 or 4 exoplanets July 21 201p l39alnd July 13 2mm Ksbancl Cquot AU 05 November l 2009 L39bond o Exoplanets discovery 0 How are they found Spectroscopy most popular method Astrometry 0 To say a planet orbits a star is really an approximation Rather the planet and star orbit a common center of mass 0 Even if the planet isn t visible the effect on the star its wobble can be observed via spectroscopy Echses Microlensing using gravity to magnify images like an optical lens 0 Tested but not con rmed method to work magnification lensed images source star 39 quotdarkquot lens o 51 Pegasi b o Is a single star much like the sun in the constellation of Pegasus 0 French astronomers noticed a wobble for the star back in 1995 this is a graph showing its back and forth motion 0 The planet is only 005 AU from its star with an orbital period of 42 days it is likely a gas giant with 12 the mass of Jupiter 51 Fug ti mend re moved 2 Iii mg i es 2 Radial Velocity M13531 i 11 l5 3l i n E lql n 4352 ail 12 M1 35 J3 11 LE WELSH 47 Ursae Majoris b o The second exoplanet discovery was announced in early 1996 by American astronomers ls orbital period is nearly 3 years long 0 Since then other planets have been found in 47 Uma two planets are Jupiter sized but closer to the star than Jupiter to the sun 0 When star systems have two or more stars they are distinguished by capital letters Sirius A or Sirius B o Exoplanets use lower case letters and start with the letter quotbquot 51 Pegasi b Kepler Spacecraft o The most proli c discoverer of exoplanets has been the kepler spacecraft which operated from 2009 to 2013 o The spacecraft is being refurbished remotely in order to extend its mission lt originally targeted stars in constellations such as Cygnus Lyra and Draco it will next look toward Leo and Virgo Exoplanet Statistics 0 Several hundred planets have been con rmed so far this graph shows the numbers found per calendar year 3 D 39 E F 1 13 13 EU 25 3 33 23 El E4 32 ii E EE i993 39 E IQEE l g l994 ig b lggtv 1E9 39HEE 255 E3 ESEW 2952 IDES 333i 2335 EKJE Ef E E 3E1 o This graph shows the orbital periods of exoplanets vs their masses periods tend to be short and masses large kng y 1 O This is possibly an observational effect it is easier to nd planets with shorter periods and larger masses 0 So most exoplanets found so far look like Jovian s but often very close to their stars 0 We are not quite yet able to con rm Earthsized planets though there are hints 0 Giant exoplanets are often found near their parent stars but they couldn39t have formed there i i3 1 war 3 an 1 EU l l i KICI l 7 i Eu I I I g l 1 g39 i I r s H E E i lT 2amp3 313 TEE hi L Gas is too volatile to gather near a star There not enough room and therefor material to make giant planets there This is true also for our solar system Jupiter and Saturn were originally further from the Sun as they interact with debris their orbits slowly migrated inward In the process Uranus Neptune and much or the remaining debris was ung outward This process took hundreds of millions of years
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