04/19/23 AST 248, Spring 2007 1

Habitable Terrestrial Exoplanet

• Search for terrestrial planets around M dwarfs → larger reflex motion– Smaller stellar mass– Habitable zone closer (<0.1 AU): does not mean

planet is there– Circularization: eccentricity may be small

• Gliese 581: previously known to have Neptune-mass planet

• 2 new planets: one with no eccentricity• Deduced mean planetary temperature: 0–40 C

(depends on reflectivity)

04/19/23 AST 248, Spring 2007 2

04/19/23 AST 248, Spring 2007 3

Gliese 581 Parameters

Parameter Gl 581 b Gl 581 c Gl 581d

P [days] 5.3684

0.0004

12.93 0.008

84.4

0.6

e 0 (fixed) 0 (fixed) 0.20

0.09

a [AU] 0.041 0.073 0.25

m sin i [M] 15.7 5.1 8.2

04/19/23 AST 248, Spring 2007 4

Search for Life in the Universe

Chapters 12 (Part 2)

Unidentified Flying Objects (UFOs)

04/19/23 AST 248, Spring 2007 5

Outline• UFOs

– Crashed Aliens in Roswell, NM– Crop Circles, Abductions, etc.– Ancient Visitations– Cover-Up & Scientific Disinterest

04/19/23 AST 248, Spring 2007 6

UFOs

• Appearance– Jet planes first introduced at the end of World War II

public aware of fast-moving aircrafts– First UFO claim in June 1947– “Flew erratic, like a saucer” flying saucer– ~50% of the public believe in the existence of UFOs

• Air Force Investigation– 20-year investigation– 90% of claims discarded– Remaining 10% indeterminate– Lack of proof is no proof

04/19/23 AST 248, Spring 2007 7

04/19/23 AST 248, Spring 2007 8

Crashed Aliens in Roswell, NM

• Known facts– Rancher found crash remnants July 1947– Military personnel picked up the debris– Remains shown next day in Fort Worth, TX– Claimed to be remains of a weather balloon

• Claims by Stanton Friedman (1978)– Crash an alien spacecraft– Alien bodies also recovered– Story hushed up by military

• Analysis– Project Mogul: balloon used for secret monitoring of Soviet tests– Witness accounts in seventies contradicted or discounted– Motive for secrecy not clear– Ability to keep secret highly doubtful

04/19/23 AST 248, Spring 2007 9

04/19/23 AST 248, Spring 2007 10

Crop Circles, Abductions, etc.

• Crop circles:– Claim: too accurate and too quick to be done

by humans– Shown to be possible– Some admitted to be pranks

• Abductions:– Sleep paralysis: common dream during rapid

eye movement (REM)– Also known during day dreaming

04/19/23 AST 248, Spring 2007 11

04/19/23 AST 248, Spring 2007 12

Ancient Visitations

• Ancient drawings– Claim: pictures of aliens– Counterclaim: other possibilities abound

• Nazca markings– Claim: needed unavailable knowledge– Counterclaim: did not need unavailable knowledge– Claim: could only be seen from space– Counterclaim: could be form of worship

• Egyptian pyramids– Claim: Egyptians could not build the pyramids by themselves– Counterclaim: it was shown that the pyramids could be

constructed with tools available then

04/19/23 AST 248, Spring 2007 13

04/19/23 AST 248, Spring 2007 14

04/19/23 AST 248, Spring 2007 15

Cover-Up & Scientific Disinterest

• Cover-up– Motive to avoid alarm: 50% already think that aliens

have landed– U.S. Government notoriously unable to keep secrets

known by many for a long time– All other governments need to participate in the

conspiracy

• Scientific disinterest– Stems from lack of evidence, not disinterest– If there was serious evidence, or the chance to obtain

serious evidence, scientists would jump at it