Astronomy 101 The Solar System Tuesday Thursday Tom

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

Course • Course Website: – http: //blogs. umass. edu/astron 101 -tburbine/ • Textbook: – Pathways to Astronomy (2 nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator.

• There is an Astronomy Help Desk that is open Monday -Thursday evenings from 7 -9 pm in Hasbrouck 205. • There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http: //www. astro. umass. edu/~orchardhill/index. html.

Exam #4 • April 22 nd • Mercury, Venus, and Mars • Review Session at 6 pm on April 21 st in Hasbrouck 20

HW #16, #17, #18, #19, and #20 • Homework #21 and #22 is due by May 4 th at 1 pm

Shaping Planetary Surfaces • • Impact Cratering Volcanism Tectonics Erosion

Cratering Meteor Crater, Arizona http: //www. solarviews. com/eng/tercrate. htm

Galle Crater, Mars

Mercury http: //geologyindy. byu. edu/eplanet/chapter_5. htm

Callisto (Moon of Jupiter) http: //ase. tufts. edu/cosmos/view_picture. asp? id=726

Earth’s atmosphere • Small asteroids burn up in the Earth’s atmosphere before they hit the ground • Any craters that do form are quickly eroded by weather generated in the atmosphere

Volcanism

Erosion • Processes that break down or transport rock through the action of ice, liquid, or gas • Movement of glaciers • Formation of canyons by running water • Shifting of sand dunes by wind

• Erosion, volcanism, and plate tectonics destroy craters

Energy of Impact (K-T) • • • v = 17 km/s = 17, 000 m/s Density = 3, 000 kg/m 3 Diameter = 2*radius =10 km Volume = 4/3*π*r 3 = 5. 23 x 1011 m 3 Mass = density*volume Mass = 1. 57 x 1015 kg Kinetic energy = ½ mv 2 Kinetic energy = 2. 27 x 1023 Joules Kinetic Energy = 5. 42 x 107 Megatons of TNT Largest Nuclear Bomb is 100 Megatons of TNT

Result of all this Energy • Rock melts • Cools quickly to form glass

Gene Shoemaker Parts taken from talk of Bridget Mahoney

Meteor Crater, Flagstaff, Arizona • Shoemaker wrote his Ph. D thesis on Meteor Crater • Shoemaker did seminal research in the mechanics of meteorite impacts

Meteor Crater and Shoemaker • In 1952, Shoemaker hypothesized that Meteor Crater as well as lunar craters were created by asteroidal impacts • USGS sent Shoemaker to the Yucca flats to investigate small nuclear events to compare with Meteor Crater, Shoemaker at Meteor Crater, 1960’s

Coesite • While doing research in the Yucca flats on meteorite impact with David Chao, the pair discovered Coesite • Coesite (Si. O 2) is a mineral that is produced during violent impact earth. leeds. ac. uk

Chicxulub Crater Taken from presentation by Amanda Baker

K-T Boundary • 65 million years ago • Boundary in the rock record separating the Cretaceous and Tertiary Periods • Corresponds to one of the greatest mass extinctions in history • Global layer of clay separating the two periods • First proposed by Walter Alvarez

We know it happened but where? • A Circular geophysical anomaly, now known to define the Chicxulub structure, was originally identified on the northern edge of the Yucatan Peninsula during oil surveys in the 1950's.

Chicxulub • Translates to “tail of the devil” in Mayan • The meteorite's estimated size was about 10 km (6 mi) in diameter, releasing an estimated 4. 3× 1023 joules of energy (equivalent to 191, 793 gigatons of TNT) on impact.

Chicxulub Impact

Data • Seismic, gravity and magnetic data define a structure ~180 km in diameter.

What happened? • An asteroid roughly 10 km (6 miles) across hit Earth about 65 million years ago. • This impact made a huge explosion and a crater about 180 km (roughly 110 miles) across. • Debris from the explosion was thrown into the atmosphere, severely altering the climate, and leading to the extinction of roughly 60% of species that existed at that time, including the dinosaurs.

Environmental Damage • http: //www 4. tpgi. com. au/users/horsts/climate. htm

• The worst hit organisms were those in the oceans. • On land, the Dinosauria of course went extinct, along with the Pterosauria. • Mammals and most non- dinosaurian reptiles seemed to be relatively unaffected. • The terrestrial plants suffered to a large extent, except for the ferns, which show an apparently dramatic increase in diversity at the K-T boundary, a phenomenon known as the fern spike.

• Pterosaurs were flying reptiles

• Dinosaurs lived during the Mesozoic Era, from late in the Triassic period (about 225 million years ago) until the end of the Cretaceous (about 65 million years ago).

• Modern birds are considered to be the direct descendants of dinosaurs

Tunguska • Occurred in 1908 • Huge explosion in the atmosphere • Thought to be asteroid or comet that exploded in mid-air 6 to 10 kilometers above the Earth's surface • Energy of 10 and 15 megatons of TNT • Equivalent to the most powerful nuclear bomb detonated in the USA • There wasn’t a large expedition to the site until 1927

http: //en. wikipedia. org/wiki/Image: Tunguska_event_fallen_trees. jpg

http: //thunderbolts. info/tpod/2006/image 06/060203 tunguska 2. jpg

• http: //geophysics. ou. edu/impacts/tunguska_dc. gif

Evidence for extraterrestrial impact • No large meteorite fragments were found • Found were microscopic glass spheres that contained high proportions of nickel and iridium

Other ideas • http: //en. wikipedia. org/wiki/Tunguska_event

Craters • Tend to be round unless it is an oblique impact Tycho crater on Moon Diameter 85 km Depth 4. 8 km http: //en. wikipedia. org/wiki/Impact_crater

Moon (180 x 65 km). Mars (380 x 140 km) http: //www. boulder. swri. edu/~bottke/Oblique_craters/oblique. html

Craters

• Complex craters tend to be larger than simple craters

• Complex Craters – gravity causes the steep crater walls to collapse, which makes complex craters very shallow – Central uplift where the earth rebounds from the impact

Peak Ring Central peak Collapses Complex (Melosh, 1989)

Different types of craters • http: //www. classzone. com/books/earth_science/te rc/content/investigations/es 2506 page 07. cf m

• Small craters are usually much more common than larger ones http: //mars. jpl. nasa. gov/gallery/craters/hires/Gusev(plain). jpg

• More craters at smaller sizes - older

Late Heavy Bombardment • A period of time approximately 3. 8 to 4. 1 billion years ago during which a large number of impact craters are believed to have formed on the Moon • Determined from the formation ages of impact melt rocks that were collected during the Apollo missions. • Earth must have also been affected • (The age dates when the rock formed. )

Dating through crater counting (Things to bear in mind) • Impact rate and size distribution of impacting bodies • Temporal and spatial variations in impactor population • Temporal variation in the target • Crater degradation • Secondary impacts • Need for measured surface ages to calibrate counting

Calibration • Moon – we have samples from specific places • Other planets – no samples

http: //www. psi. edu/projects/mgs/chron 04 c. html

• Cratering rate will be different on Mars compared to the Moon – Mars has larger mass so larger flux (gravitational focusing) – Mars closer to asteroid belt (more possible impactors)

What’s the difference? • Asteroids • Comets • Meteorites

What’s the difference? • Asteroids - small, solid objects in the Solar System • Comets - small bodies in the Solar System that (at least occasionally) exhibit a coma (or atmosphere) and/or a tail • Meteorites - small extraterrestrial body that reaches the Earth's surface

Why are these things important?

Why are these things important? • These things can hit us (and possibly kill us) • They are records of the early solar system • They could be sources of material for mining

Moon

Record of Early Solar System • Meteorites usually have ages of ~4. 6 billion years • Asteroids and comets are thought to be the building blocks of the terrestrial planets

Resources • In outer space, it may be easier (and less expensive) to extract raw materials from asteroids or comets then to bring them from Earth • Raw materials include water, iron, aluminum, chromium

Why we should worry about asteroids and comets?

2009 DD 45 Over 36 minutes • On March 2, 2009: • NEA 2009 DD 45 came within ~70, 000 km of the surface of the Earth • Diameter between 21 -47 m http: //www. skyandtelescope. com/observing/highlights/40504617. html

Tunguska • This object is believed to be the same size as the object that exploded over Siberia in 1908 • About 1, 000 times as powerful as the bomb dropped on Hiroshima http: //dustyloft. wordpress. com/2008/06/ http: //geophysics. ou. edu/impacts/tunguska_dc. gif

2008 TC 3 • 2 -3 m object that entered the atmosphere over Sudan on October 7, 2008 • Burned up before it reached the ground • Fragments found http: //en. wikipedia. org/wiki/File: 2008 TC 3 -groundpath-rev. png http: //i 176. photobucket. com/albums/w 189/walcom 77/2008 TC 3_fragments. jpg

99942 Apophis • Initially thought to have a high probability (up to 2. 7%) of hitting Earth in 2029 • ~270 meters in diameter • Impact probability with Earth for April 13, 2036 is calculated as 1 in 45, 000 2029 http: //en. wikipedia. org/wiki/File: Apophis_pass_zoom. svg

Meaning of Asteroid • Asteroid means “star-like” • Called vermin of the sky by astronomers

216 Kleopatra

Asteroid Flyby • • Movie Images of 2002 NY 40 on August 15 -16 Asteroid has diameter of 700 meters 524, 000 kilometers from Earth (1. 3 times the distance of the Earth to the Moon) • Movie over 2 hour time period

Titius-Bode Law • The mean distance a (AU) of the planet from the Sun: • a = 0. 4 + 0. 3 x k • where k=0, 1, 2, 4, 8, 16, 32, 64, 128 (0 followed by the powers of two) • 1 astronomical unit (AU) is the average distance from the Earth to the Sun

Planet (when discovered) Mercury Venus k 0 1 Titius-Bode Distance 0. 4 0. 7 Actual Distance 0. 39 0. 72 Earth Mars ? Jupiter Saturn Uranus (1781) Neptune (1846) Pluto (1930) 2 4 8 16 32 64 128 1. 0 1. 6 2. 8 5. 2 10. 0 19. 6 38. 8 1. 00 1. 52 ? 5. 20 9. 54 19. 2 30. 1 39. 5

So … • Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the "missing planet" • But the first asteroid, 1 Ceres, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi

But … • Three other asteroids (2 Pallas, 3 Juno, 4 Vesta) were discovered over the next few years (18021807) • After eight more years of fruitless searches, most astronomers assumed that there were no more • However, Karl Ludwig Hencke persisted, and began searching for more asteroids in 1830. • Fifteen years later, he found 5 Astraea, the first new asteroid in 38 years. He also found 6 Hebe less than two years later.

all known asteroids

ecliptic

Currently • Over 400, 000 – number of known asteroids • Over 6, 000 – number of Near-Earth asteroids

Asteroid Families

Asteroid Families • Clumpings of asteroids with similar orbits • Thought to be due to the breakup of a larger parent body

How are these objects named? • Asteroids – After being observed on two consecutive nights, the object is given a provisional designation – a 4 -digit number indicating the year – a space – a letter to show the half-month – another letter to show the order within the half-month – And an optional number to indicate the number of times the second letter has been repeated in that halfmonth period. • For example, 1977 RG

Half Month Discovery • • • • Letter Dates Letter A Jan. 1 -15 B C Feb. 1 -15 D E Mar. 1 -15 F G Apr. 1 -15 H J May 1 -15 K L June 1 -15 M N July 1 -15 O P Aug. 1 -15 Q R Sept. 1 -15 S T Oct. 1 -15 U V Nov. 1 -15 W X Dec. 1 -15 Y I is omitted and Z is unused Dates Jan. 16 -31 Feb. 16 -29 Mar. 16 -31 Apr. 16 -30 May 16 -31 June 16 -30 July 16 -31 Aug. 16 -31 Sept. 16 -30 Oct. 16 -31 Nov. 16 -30 Dec. 16 -31

Order within Month • • • A = 1 st B = 2 nd C = 3 rd F = 6 th G = 7 th H = 8 th L = 11 th M = 12 th N = 13 th Q = 16 th R = 17 th S = 18 th V = 21 st W = 22 nd X = 23 rd I is omitted D = 4 th J = 9 th O = 14 th T = 19 th Y = 24 th E = 5 th K = 10 th P = 15 th U = 20 th Z = 25 th

Asteroids discovered between Sept 16 -30 of 1995 • • • 1995 SA 1 1995 SB 2. . . 1995 SY 24 1995 SZ 25 1995 SA 1 26 … 1995 SZ 1 50 1995 SA 2 51. . . 1995 SZ 9 250 1995 SA 10 251

Asteroid Numbers and Names • When well-observed, asteroid is given a number • 5159 1977 RG • When was it discovered?

Asteroid Numbers • When well-observed, asteroid is given a number • 5159 1977 RG • When was it discovered? – 1977 – R Sept. 1 -15 – G 7 th asteroid

Asteroid Names • Then the discover gets to name it for period of 10 years or so • 5159 1977 RG • Was named

Asteroid Names • Then the discover gets to name it for period of 10 years or so • 5159 1977 RG • Was named – 5159 Burbine

• ~6, 000 objects are considered near-Earth asteroids – Their orbits come close to the Earth’s orbit • More discovered every day

Object Name 1 AU = ~150 million kilometers 1 LD = Lunar Distance = ~384, 000 kilometers Relative Close Miss Estimated H Velocity Approach Distance Diameter (mag) (km/s) Date (AU) (LD) (2001 UZ 16) 2008 -Sep-16 0. 1523 59. 3 350 m - 780 m 19. 4 9. 19 (2008 SR 1) 2008 -Sep-16 0. 0400 15. 6 240 m - 540 m 20. 2 17. 96 (2001 SQ 3) 2008 -Sep-17 0. 0556 21. 6 130 m - 280 m 21. 6 15. 27 (2008 RE 1) 2008 -Sep-17 0. 0736 28. 7 68 m - 150 m 23. 0 6. 72 (2003 SW 130) 2008 -Sep-19 0. 0220 8. 6 4. 0 m - 8. 9 m 29. 1 8. 17 (2008 SZ 1) 2008 -Sep-19 0. 0308 12. 0 32 m - 70 m 24. 6 7. 14 (2008 ST 1) 2008 -Sep-20 0. 0038 1. 5 11 m - 25 m 26. 9 7. 78 (2008 RT 24) 2008 -Sep-22 0. 0739 28. 7 35 m - 79 m 24. 4 6. 12 (2008 RW 24) 2008 -Sep-23 0. 0129 5. 0 71 m - 160 m 22. 9 11. 03 (2008 SA) 2008 -Sep-23 0. 0061 2. 4 26 m - 58 m 25. 0 7. 79

Energy of an impact • • • E = ½mv 2 v = 10 km/s = 10, 000 m/s m = ρV V = 4/3πr 3 100 m object – V = 4/3π(50)3 = 5. 2 x 105 m 3 • 1, 000 m object – V = 4/3π(500)3 = 5. 2 x 108 m 3 • 10, 000 m object – V = 4/3π(5000)3 = 5. 2 x 1011 m 3

Energy of an impact • E = ½ ρVv 2 • v = 10 km/s = 10, 000 m/s • 100 m diameter object – E = ½*5. 2 x 105 m 3*(1 x 108)*ρ • 1, 000 m diameter object – E = ½*5. 2 x 108 m 3*(1 x 108)*ρ • 10, 000 m diameter object – E = ½*5. 2 x 1011 m 3*(1 x 108)*ρ

Energy of Nuclear Bombs • Usually given in Megatons of TNT • The bomb that destroyed Hiroshima yielded ~0. 015 Megatons (~15 kilotons) of TNT • Largest nuclear bomb ever was ~50 Megatons (~3, 400 Hiroshimas) http: //images. encarta. msn. com/xrefmedia/sharemed/targets/images/pho/t 039/T 039873 A. jpg

Energy of an Impact • ρ = 7, 500 kg/m 3 for an iron meteorite • 100 m diameter object – E = 2 x 1017 J = 47 MT of TNT ≈ 3, 100 Hiroshimas • 1, 000 m diameter object – E = 2 x 1020 J = 4. 7 x 104 MT of TNT ≈ 3, 100, 000 Hiroshimas • 10, 000 m diameter object – E = 2 x 1023 J = 4. 7 x 107 MT of TNT ≈ 3, 100, 000 Hiroshima

Energy of an Impact • ρ = 3, 500 kg/m 3 for an ordinary chondrite • 100 m diameter object – E = 9. 2 x 1016 J = 22 MT of TNT ≈ 1, 500 Hiroshimas • 1, 000 m diameter object – E = 9. 2 x 1019 J = 2. 2 x 104 MT of TNT ≈ 1, 500, 000 Hiroshimas • 10, 000 m diameter object – E = 9. 2 x 1022 J = 2. 2 x 107 MT of TNT ≈ 1, 500, 000 Hiroshimas

The Effects • If an 100 -meter iron asteroid hit Hartford at 10 km/s: • 2. 3 km crater forms • Here: • Richter Scale Magnitude: 5. 7 • Shaking felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing cars rocked noticeably. • Shaking felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. • At your position there is a fine dusting of ejecta with occasional larger fragments • Sound intensity will be as loud as heavy traffic.

The Effects • If an 1 -kilometer iron asteroid hit Hartford at 10 km/s: • 15. 7 km crater forms • Here: • Richter Scale Magnitude: 7. 7 • Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built structures; some chimneys broken. • The ejecta will arrive ~130 seconds after the impact. • The air blast will arrive at approximately 245 seconds. Multistory wallbearing buildings will collapse. Wood frame buildings will almost completely collapse. Highway truss bridges will collapse. Glass windows will shatter. Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

The Effects • If an 10 -kilometer iron asteroid hit Hartford at 10 km/s: • 74. 1 km crater forms • Asteroid that killed off the dinosaurs was ~10 km in diameter • Here: • Richter Scale Magnitude: 9. 7 (greater than any impact in recorded history) • UMASS-Amherst is in the region which collapses into the final crater.

Effects are worse in this chart because a higher impact velocity is assumed. http: //www. aerospaceweb. org/question/astronomy/impact/torino-scale. jpg

http: //comp. uark. edu/~sboss/torinoscale. jpg

http: //www. nature. com/nature/journal/v 418/n 6897/images/418468 b-i 1. 0. jpg

What is important to know about possible incoming asteroids? • Will it hit the Earth? • Size? • Where will it hit? – ocean? (You might get a tsunami) – uninhabited area? – major population center? • What is it made out of? – That is what I work on – I try to determine the mineralogy of asteroids using meteorites as a guide. • What will be its impacting velocity?

How could you deflect an asteroid? • First a spacecraft could be crashed directly into the asteroid. • Then a second spacecraft, a gravity tractor, would be used. – It would weigh around a ton and hovering about 150 meters away from the asteroid. – It would exert a gentle gravitational force, changing the asteroid's velocity by only 0. 22 microns per second each day. http: //space. newscientist. com/article/dn 14414 -gravity-tractor-could-deflect-asteroids-nasa-study-says. html

Any Questions?