1. Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine tomburbine@astro.umass.edu

2. Course Course Website: –http://blogs.umass.edu/astron101-tburbine/http://blogs.umass.edu/astron101-tburbine/ Textbook: –Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

3. Final May 7 th Friday 4 pm Totman Gym Cumulative Review Session –Hasbrouck 20, 6:15 pm, Wednesday (May 5 th )

4. Formulas p 2 = a 3 F = GMm/r 2 F = ma T (K) = T ( o C) + 273.15 c = f* E = h*f KE = 1/2mv 2 E = mc 2 Density = mass/volume Volume = 4/3  r 3

5. HW Homeworks #21, #22, #23, and #24

6. Uranus

7. Discovered by William Herschel in 1781 In 1977, the first nine rings of Uranus were discovered

9. Atmosphere The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, 2% methane and small amounts of acetylene and other hydrocarbons. Methane in the upper atmosphere absorbs red light, giving Uranus its blue-green color.

10. Unusual Tipped on its side Why?

11. Probably Due to a collision

12. Uranus’ Satellites Cordelia Ophelia Bianca Cressida Desdemona Juliet Portia Rosalind 2003U2 Belinda 1986U10 Puck 2003U1 Miranda Ariel Umbriel Titania Oberon 2001U3 Caliban Stephano Trinculo Sycorax 2003U3 Prospero Setebos 2002U2

13. Instead of being named after people from classical mythology, Uranus' moons take their names from the writings of William Shakespeare and Alexander Pope.

14. Neptune

15. After the discovery of Uranus, it was noticed that its orbit was not as it should be in accordance with Newton's laws. It was therefore predicted that another more distant planet must be perturbing Uranus' orbit. Neptune was first observed by Johan Galle and Heinrich d'Arrest on 1846 Sept 23 very near to the locations predicted from theoretical calculations based on the observed positions of Jupiter, Saturn, and Uranus.

16. Galileo Galileo's astronomical drawings show that he had first observed Neptune on December 27, 1612, and again on January 27, 1613; On both occasions Galileo had mistaken Neptune for a fixed star

17. Neptune's blue color is largely the result of absorption of red light by methane in the atmosphere

18. Great Dark Spot Thought to be a hole Scooter Small dark spot

19. Great Dark Spot has disappeared

20. Neptune’s Rings

21. Triton Largest moon of Neptune Has retrograde orbit (orbits the planet in the opposite direction as the planet is rotating) May be captured Kuiper Belt Object

22. Pluto Pluto is a Dwarf Planet Smallest planet Diameter = 2306 ± 20 km (18% of Earth) Mass = (1.305±0.007)×10 22 kg (0.0021 Earths)

24. In the late 19th century, astronomers started speculating that Neptune's orbit was being disturbed by another planet.

25. Pluto was discovered after an extensive search by Clyde Tombaugh at the Lowell Observatory in Arizona in 1930

26. Pluto Venetia Burney (born 1919) was the first person to suggest the name Pluto for the 9 th planet

27. However Pluto is far too small to have the effect on Neptune's orbit that initiated the search. The discrepancies in Neptune's orbit observed by 19th century astronomers were due instead to an inaccurate estimate of Neptune's mass.

28. Pluto’s orbit is exceptional among the planets –high inclination (>17 °) and eccentricity (~0.25). –Only Mercury's orbit shows a significant inclination (~7°) and eccentricity (~0.2) Other planets follow quasi-circular, near–ecliptic orbits

30. Density 2.03 g/cm 3 What does this mean?

32. Satellites Charon –discovered in 1978 by astronomer James Christy Two smaller, provisionally designated ones –Nix –Hydra

36. Barycenter (center of mass) lies above the planet's surface. Charon is large relative to Pluto –Diameter is half of Pluto Some astronomers label it a double planet system

39. Pluto's icy surface is 98% nitrogen (N2). Methane (CH4) and traces of carbon monoxide (CO) are also present. The solid methane indicates that Pluto is colder than 70 Kelvin.

40. Pluto

42. Kuiper Belt Pluto is thought to be one of the largest Kuiper Belt Objects (KBOs)

43. Kuiper Belt is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun Over 1,000 Kuiper Belt Objects (1,130) are known

45. Eris It has a moon - Dysnomia Larger than Pluto

46. Eris

47. New Horizons

49. Mission Will characterize the global geology and morphology of Pluto and its moon Charon Map their surface composition and characterize Pluto's neutral atmosphere and its escape rate Will also photograph the surfaces of Pluto and Charon.

50. Earth Is the only planet known to have life

51. SETI Search for Extra-Terrestrial Intelligence SETI programs tend to survey the sky to detect the existence of transmissions from a civilization on a faraway planet

52. Intelligent Life You have to be able to build a radio telescope Of electromagnetic radiation, only radio and gamma can cross the Milky Way Galaxy It takes far less energy to produce radio waves than gamma rays

53. Europa Moon of Jupiter Has an outer layer of ice http://en.wikipedia.org/wiki/Image:Europa-moon.jpg

54. Europa Is thought to have a liquid ocean beneath an icy surface Energy source provided by tidal heating (keeps ocean from freezing) Proposed as possibly as possibly having extraterrestrial life

55. www.physics.brandeis.edu/powerpoint/Charbonneau.ppt

57. The only star we know that has Earth-Like Planets is the Sun Sun is sometimes called Sol

58. Galactic Habitable Zone It is the area in the galaxy whose boundaries are set by its calm and safe environment, and access to the chemical materials necessary for building terrestrial planets similar to the Earth. http://astronomy.swin.edu.au/GHZ/ green is habitable zone

59. Habitable Zones http://en.wikipedia.org/wiki/Image:Habzonethinkquest.gif

60. HabCat Catalog of Nearby Habitable Systems made by Jill Tarter and Margaret Turnbull These Sun-like, habitable stars have just the right distance, constancy, and temperature to qualify in a forthcoming enlarged radio search.

61. What do else do you need? You need “metals” to make planets –Metals are elements heavier in mass than helium

62. For simple life You need a planet with an atmosphere and some water

63. Stars must remain nearly constant in brightness over billions of years for complex life to have time to develop. –On Earth, single cells may have developed after only 800 million years or so, but the fossil record indicates that it took another 3 to 4 billion years before multi-cellular life flourished.

64. The number of HabCat stars, as a function of distance M-type stars (solid red histogram) K stars (dark-hatched green histogram) G stars (light-hatched violet histogram) F stars (horizontal-lined yellow histogram) all stars (open blue histogram). http://www.astrobio.net/news/article436.html

65. Drake Equation The Drake Equation is an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

66. Number of habitable planets 100 billion?

67. Fraction of Planets that have life in the Galaxy ?

68. Fraction of the Life-Bearing Planets in the Galaxy upon which a Civilization capable of interstellar communication has at some time arisen ?

69. Intelligent Life Intelligent life that we can detect is usually defined as life that can build a radio telescope

70. Radio Transmitting information over radio waves is very cheap uses equipment that is easy to build has the information-carrying capacity necessary for the task The information also travels at the speed of light.

71. Fraction of all civilizations that have existed in the galaxy that exist now ?

73. Fermi’s Paradox Where are they?

74. Fermi’s Paradox Why have we not observed alien civilizations even though simple arguments would suggest that some of these civilizations ought to have spread throughout the galaxy by now?

75. Reason for question Straightforward calculations show that a technological race capable of interstellar travel at (a modest) one tenth the speed of light ought to be able to colonize the entire Galaxy within a period of one to 10 million years.

76. Explanation Interested in us but do not want us (yet) to be aware of their presence (sentinel hypothesis or zoo hypothesis)

77. Explanation Not interested in us because they are by nature xenophobic or not curious

78. Explanation Not interested in us because they are so much further ahead of us

79. Explanation Prone to annihilation before they achieve a significant level of interstellar colonization, because: (a) they self-destruct (b) are destroyed by external effects, such as: (i) the collision of an asteroid or comet with their home world (ii) a galaxy-wide sterilization phenomenon (e.g. a gamma-ray burster (iii) cultural or technological stagnation

80. Explanation Capable of only interplanetary or limited interstellar travel because of fundamental physical, biological, or economic restraints

81. Fermi’s paradox The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations. http://en.wikipedia.org/wiki/Fermi_paradox

82. Any Questions?