Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20. Tom Burbine

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1 Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine

2 Course Course Website: Textbook: Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

3 Office Hours Mine Tuesday, Thursday - 1:15-2:15pm Lederle Graduate Research Tower C 632 Neil Tuesday, Thursday - 11 am-noon Lederle Graduate Research Tower B 619-O

4 Homework We will use Spark owebct Homework will be due approximately twice a week

5 Astronomy Information Astronomy Help Desk Mon-Thurs 7-9pm Hasbrouck 205 The Observatory should be open on clear Thursdays Students should check the observatory website at: for updated information There's a map to the observatory on the website.

6 Final Monday - 12/14 4:00 pm Hasbrouck 20

7 Due today HW #10

8 Next Tuesday HW #11

9 If you want to find life outside our solar system You need to find planets

10 Extrasolar Planets Today, there are over 400 known extrasolar planets

11 Star Names A few hundred have names from ancient times Betelgeuse, Algol, etc. Another system: A star gets name depending on what constellation it is in With a Greek letter at the beginning Alpha Andromeda, Beta Andromeda, etc. Only works for 24 brightest star

12 Star Names now Stars are usually named after the catalog they were first listed in HD is listed in the Henry Draper (HD) Catalog and is number HD209458a is the star HD209458b is the first objects discovered orbiting the star

13 Our Solar System has basically two types of planets Small terrestrial planets Made of Oxygen, Silicon, etc. Large gaseous giants Made primarily of hydrogen and a little helium Jupiter - 90% Hydrogen, 10% Helium Saturn 96% Hydrogen, 3% Helium Uranus 83% Hydrogen, 15% Helium Neptune 80% Hydrogen, 20% Helium

14 Things to Remember The Milky Way has at least 200 billion other stars and maybe as many as 400 billion stars Jupiter s mass is 318 times than the mass of the Earth

15 Question: How many of these stars have planets?

16 What is the problem when looking for planets?

17 What is the problem when looking for planets? The stars they orbit are much, much brighter than the planets

18 Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. GQ Lupi is 400 light years from our Solar System and the star itself has approximately 70% of our Sun's mass. Planet is estimated to be between 1 and 42 times the mass of Jupiter.

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20 So what characteristics of the planets may allow you to see the planet

21 So what characteristics of the planets may allow you to see the planet Planets have mass Planets have a diameter Planets orbit the star

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23 Jupiter H, He 5.2 AU from Sun Cloud top temperatures of ~130 K Density of 1.33 g/cm 3 Hot Jupiters H, He As close as 0.03 AU to a star Cloud top temperatures of ~1,300 K Radius up to 1.3 Jupiter radii Mass from 0.2 to 2 Jupiter masses Average density as low as 0.3 g/cm 3

24 ,000 (lightyears)

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26 Some Possible Ways to detect Planets Pulsar Timing Radial Velocity (Doppler Method) Transit Method Direct Observation

27 Pulsars Rotating Neutron Stars Have densities of to g/cm³

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30 Would you want to live on a pulsar planet?

31 Center of Mass Distance from center of first body = distance between the bodies*[m2/(m1+m2)]

32 Radial Velocity (Doppler Method)

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34 Wavelength

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36 Bias Why will the Doppler method will preferentially discover large planets close to the Star?

37 Bias Why will the Doppler method will preferentially discover large planets close to the Star? The gravitational force will be higher Larger Doppler Shift

38 Transit Method When one celestial body appears to move across the face of another celestial body

39 When the planet crosses the star's disk, the visual brightness of the star drops a small amount The amount the star dims depends on its size and the size of the planet. For example, in the case of HD , the star dims 1.7%.

40 Orbit has to be edge on One major problem

41 Eclipse Planet passes in back of a star Because the star is so much brighter than a planet, the dip in brightness is smaller during an eclipse than a transit Usually to maximize the effects of an eclipse, astronomers observe these eclipses at infrared wavelengths

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43 Infrared Image Direct Observation

44 Visible Infrared

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47 How did these Hot Jupiters get orbits so close to their stars?

48 How did these Hot Jupiters get orbits so close to their stars? Formed there but most scientists feel that Jovian planets formed far from farther out Migrated there - planet interacts with a disk of gas or planetesimals, gravitational forces cause the planet to spiral inward Flung there gravitational interactions between large planets

49 Kepler Mission Kepler Mission is a NASA space telescope designed to discover Earth-like planets orbiting other stars. Using a space photometer, it will observe the brightness of over 100,000 stars over 3.5 years to detect periodic transits of a star by its planets (the transit method of detecting planets) as it orbits our Sun. Launched March 6, 2009

50 Kepler Mission

51 Kepler Mission The Kepler Mission has a much higher probability of detecting Earth-like planets than the Hubble Space Telescope, since it has a much larger field of view (approximately 10 degrees square), and will be dedicated for detecting planetary transits. There will a slight reduction in the star's apparent magnitude, on the order of 0.01% for an Earthsized planet.

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54 KEY D

55 What Planet do we know the most about?

56 Earth

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58 Earth s Interior

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60 46.6% O 27.7% Si 8.1% Al 5.0% Fe 3.6% Ca 2.8% Na 2.6% K 2.1% Mg Earth s crust

61 Earth is made of minerals

62 Mineral A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystal structure

63 Olivine (Mg, Fe) 2 SiO 4 Fayalite (Fa) - Fe 2 SiO 4 Forsterite (Fo) - Mg 2 SiO 4

64 Pyroxenes XY(Si, Al) 2 O 6 X can be Ca, Na, Fe +2, Mg, Zn, Mn, and Li Y can be Cr, Al, Fe +3, Mg, Mn, Sc, Ti, V, and Fe +2 Augite Ferrosilite

65 How do we know what s in the interior of the Earth?

66 How do we know what s in the interior of the Earth? Seismic Waves vibrations created by earthquakes

67 Seismic Waves P waves primary waves (pushing) travel faster can travel through anything S waves secondary (side to side) travel slower only through solids

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69 Surface Waves Travel on the surface of the Earth Love Wave side by side mation.gif Rayleigh Wave rolling movement _animation.gif Most of the shaking felt from an earthquake is due to the Rayleigh waves

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71 P (primary) waves S (secondary) waves Surface waves: Rayleigh and Love waves

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77 Richter Scale Measures the magnitude of an earthquake Single number to quantify the amount of seismic energy released by an earthquake. Amplitude of largest displacement Under At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings Can be destructive in areas up to about 100 kilometers across where people live Major earthquake. Can cause serious damage over larger areas. 8 or greater - Great earthquake. Can cause serious damage in areas several hundred kilometers across.

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81 How do we get information? The precise speed and direction of the waves depends on the composition, density, pressure, temperature, and phase (solid or liquid)

82 Which of these bodies have they used seismic waves to study?

83 Earth Moon Apollo missions brought seismometers to Moon to study moonquakes

84 How can you study the interior of a planet from space?

85 Density Density = mass/volume If the density is higher than the surface rock, there must be denser material in the interior

86 Gravity If you can measure gravity (force) with a spacecraft as it rotates around a body, you can determine how mass is distributed on the body

87 Magnetic Field Tells if a planet has a molten metal interior

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89 Earth s magnetic field is believed to be caused by the convection of molten iron, within the outer liquid core along with the rotation of the planet Electrons flow

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91 Magnetic pole moves

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93 North Magnetic Pole However, the "north pole" of a magnet is defined as the one attracted to the Earth's North Magnetic Pole By this definition, the Earth's North Magnetic Pole is physically a magnetic south pole

94 Glatzmeier and Roberts simulations:

95 Geomagnetic Reversals Based upon the study of lava flows of basalt throughout the world, it has been proposed that the Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years The average interval is ~250,000 years. The last such event, called the Brunhes- Matuyama reversal is theorized to have occurred some 780,000 years ago.

96 The present strong deterioration corresponds to a 10 15% decline over the last 150 years and has accelerated in the past several years Geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value, which was achieved approximately 2000 years ago. At this rate, the dipole field will temporarily collapse by AD

97 What may happen during the reversal? There may be a slight rise in the per capita cancer rate due to a weaker magnetic field. We may also be able to see the northern lights at lower latitudes If you own a compass, it will have difficulty finding north until the magnetosphere settles.

98 Van Allen Belts The Van Allen radiation belts are rings of energetic charged particles around Earth, held in place by Earth's magnetic field Outer belt primarily electrons Inner belt primarily protons

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100 Van Allen Belts

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102 James Van Allen Sent a Geiger Counter on the first US satellite Explorer 1 The Geiger counter began clicking madly as soon as it reached orbit

103 Auroras Auroras natural light displays Collision of charged particles from Earth's magnetosphere with atoms and molecules of Earth's upper atmosphere The collisions in the atmosphere electronically excite atoms and molecules in the upper atmosphere. The excitation energy can be lost by light emission or collisions.

104 Any Questions?