Pluto and Extrasolar PlanetsPublic Lecture - October 12, 2012

Dr. Mike MacCallumLong Beach City Collegemmaccallum@lbcc.edu

Definition of a Planet

✤ August 2006, the International Astronomical Union passed a new definition for planet✤ Must orbit the sun✤ Must have been pulled into a spherical shape by its gravity--a

process called differentiation✤ Must have cleared its neighborhood of other bodies

✤ http://www.iau.org

Dwarf Planets

✤ Must orbit the sun✤ Must have been pulled into a spherical shape by its gravity--

differentiation✤ Did NOT clear its neighborhood of other bodies

✤ http://www.iau.org

Dwarf Planets

✤ Five currently accepted✤ Ceres (asteroid)✤ Pluto✤ Haumea✤ Makemake✤ Eris

✤ Four more to be accepted soon✤ Another 40 known candidates in the solar system

✤ Maybe 2 or 3 more asteroids✤ Trans Neptunian objects (TNOs) or Plutoids

✤ Could be 200 to 2,000 more in the Kuiper belt and surrounding area✤ http://en.wikipedia.org/wiki/Dwarf_planet

Dwarf Planets

✤ Mass compared to the moon✤ Ceres! 1.3%✤ Pluto! 17.8%✤ Haumea! 5.5%✤ Eris! 22.7%

✤ Mercury is about four times the mass of the moon

The Kuiper Belt

✤ http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs&Display=OverviewLong✤ http://www2.ess.ucla.edu/~jewitt/kb.html

Triton

✤ Neptune’s largest moon✤ Orbits in retrograde motion✤ 15-35% water ice✤ Mean density: 2.06 g/cm3

✤ Diameter: 2700 km (Moon: 3500 km)✤ Probably a captured Kuiper belt object (KBO)

✤ http://en.wikipedia.org/wiki/Triton_(moon)

Taken by Voyager 2

The Dawn Mission

✤ Launched 9/27/07✤ Ion engine✤ Went into orbit around 4 Vesta on 7/17/11✤ Studied Vesta for more than a year✤ Left Vesta for 1 Ceres on 9/4/2012✤ Will go into orbit around Ceres in February 2015✤ End of primary mission, July 2015

✤ http://dawn.jpl.nasa.gov/mission/

Ceres as seen by Hubble

New Horizons

✤ More than half way there✤ Launched January 19, 2006✤ Gravity assist from Jupiter in February 2007✤ Will arrive flyby Pluto and Charon in July 2015✤ Will then continue on into the Kuiper belt

✤ http://pluto.jhuapl.edu

New Horizons

✤ The fastest spacecraft to date✤ Will take nine years to reach Pluto✤ Distance to Pluto = 40 AU✤ One light year = 63,240 AU✤ Distance to nearest star = 4.22 light years or 267,000 AU✤ It will take about 60,000 years to get to Proxima Centauri

✤ http://en.wikipedia.org/wiki/List_of_nearest_stars

Astronomer of the Week

✤ Jane Luu✤ Vietnamese refugee--1975

✤ BS Stanford University 1984✤ PhD UC Berkeley and MIT✤ Taught at Harvard and in Europe

✤ Credits and awards✤ Discovered the first Kuiper Belt object with David Jewitt--after a 5-

year search✤ Discovered 20 asteroids, has an asteroid named after her✤ Received the Annie Jump Cannon Award in Astronomy

✤ Currently at the Lincoln Laboratory at MIT✤ http://www.imagiverse.org/interviews/janeluu/jane_luu_21_03_03.htm

Extrasolar Planets

✤ How many have been discovered to date?

Extrasolar Planets

✤ How many have been discovered to date? 841 as of 10/12/12

Extrasolar Planets

✤ Most are about Jupiter size or larger✤ Mostly orbit very close to their stars

✤ Known as hot Jupiters✤ http://exoplanet.eu/

Extrasolar Planets

✤ Discovery methods✤ Transits (287 + 2321 candidates)✤ Spectroscopic radial velocity (490)✤ Gravitational lensing (16)✤ Direct imaging (31)✤ Pulse measurements of pulsars (17)

Kepler Mission

✤ Launched March 6, 2009✤ Continuously observing 170,000 stars✤ Looking for planet transits✤ Relays information to Earth for more detailed study✤ Found 2321 candidates, 287 confirmed planets so far

✤ One six-planet system✤ Planets around double star systems

✤ http://kepler.nasa.gov✤ http://www.planethunters.org

Spectroscopic Radial Velocity

✤ Spectroscopic radial velocity✤ http://en.wikipedia.org/wiki/Doppler_spectroscopy✤ http://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html

Extrasolar Planets

✤ Gliese 581g✤ Three to four times mass of the Earth✤ Orbits around Gliese 581 in just under 37 days✤ Has enough mass to retain an atmosphere✤ Is right in the middle of its star’s habitable zone ✤ Probably tidally locked to its star

✤ Gliese 581✤ 20 light years from Earth in the constellation Libra✤ http://www.nasa.gov/home/hqnews/2010/sep/HQ_10-237_Exoplanet_Findings.html

Habitable Zone

✤ The place in a galaxy away from excessive radiation✤ The range of orbits around a star where liquid water can exist on a

planet✤ In our solar system, the habitable zone is about centered on Earth’s

orbit✤ Venus too hot✤ Mars too cold

✤ http://en.wikipedia.org/wiki/Habitable_zone

Earth-like Extrasolar Planets

✤ Mass of the planet✤ Mass and temperature of the star✤ Metallicity of the star✤ Planet’s distance from star✤ Eccentricity of the planet’s orbit

How Many Planets Out There?

✤ From the rate of discovery, perhaps 10s to 100s of billions of planets in the Milky Way alone

✤ The presence of at least one planet around a star appears to be the rule, rather than the exception

✤ Discovery methods to date favor large planets in close orbits✤ http://en.wikipedia.org/wiki/Extrasolar_planet

Will We Ever Communicate?

✤ Gliese 581g! 20 light years away✤ Gliese 667C c! 22 light years away✤ Kepler 22b! 600 light years away✤ HD 40307 g! 42 light years away✤ HD 85512 b! 36 light years away✤ Gliese 163c! 49 light years away

Kepler 22b

Image Credits

✤ Slide 2: NASA, Hubble Space Telescope✤ Slide 3: Discover Magazine

✤ http://blogs.discovermagazine.com/intersection/2011/02/04/the-pluto-wars-continue/#.UUHzbKWic7U

✤ Slide 4: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Dwarf_planet

✤ Slide 5: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Dwarf_planet

✤ Slide 6: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Kuiper_belt

✤ Slide 6: Don Dixon, cosmographics.com

Image Credits

✤ Slide 7: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Triton_(moon)

✤ Slide 8: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)

✤ Slide 9: Wikimedia Commons✤ http://en.wikipedia.org/wiki/New_Horizons

✤ Slide 10: Wikimedia Commons✤ http://en.wikipedia.org/wiki/New_Horizons

✤ Slide 11: Imagiverse✤ http://www.imagiverse.org/interviews/janeluu/jane_luu_21_03_03.htm

Image Credits

✤ Slide 11: East Coast Asian American Student Union✤ http://www.ecaasu.org/site/2012/03/march-7-womens-history-month-profile-jane-luu/

✤ Slide 14: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Extrasolar_planet

✤ Slide 15: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Fomalhaut_b

✤ Slide 16: NASA✤ http://kepler.nasa.gov/multimedia/photos/

✤ Slide 17: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Extrasolar_planet

Image Credits

✤ Slide 18: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Gliese_581

✤ Slide 19: Wikimedia Commons✤ http://en.wikipedia.org/wiki/Gliese_581

✤ Slide 20: Planetary Habitability Laboratory✤ http://phl.upr.edu/projects/habitable-exoplanets-catalog

✤ Slide 21: NASA, ESA, and A. Schaller✤ Slide 17: Wikimedia Commons

✤ http://en.wikipedia.org/wiki/Extrasolar_planet

Thank You for ComingWe will have a short break and then a planetarium show--the fall sky