The New Age of Discovery PLANETS

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The New Age of DiscoveryPLANETS

• College Park Observatory Open House
• October 4 2006
• Daniel Jontof-Hutter
• University of Maryland Astronomy

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Saturn
Jupiter
Mars

• With the telescope, planets were first seen as
  worlds in their own right
• However, not much more could be seen

Venus
Galileos telescope (1610)
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Uranus 1787The first planet discovered since
ancient times
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Neptune 1846

• Neptunes position was predicted by astronomers
  studying the motion of Uranus
• Britain and France both claimed the discovery,
  and disputed over names for the new planet.

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Pluto 1930

• With photography came the opportunity to record
  and compare star fields
• Neptunes motion seemed to hint at another unseen
  planet further out in the solar system
• Clyde Tombaugh in Flagstaff Arizona discovers
  Pluto

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Telescopes have improved
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Space probes have been sent
Mariner 2 Venus 1962 The first interplanetary
space probe
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Voyager I and Voyager II
Jupiter 1979
Launched 1977
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Saturn 1981
Voyager I flew by Titan
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Voyager II Uranus 1986
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Voyager II Neptune 1989
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Space probes have been sent throughout the solar
system.
Mercury Mariner 10 (1974)
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Venus
Venera 1983
Magellan 1993
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Mars Spirit (2004- ), Opportunity (2004-),
Pathfinder (1997), Viking I (1976) Viking II
(1977) ... plus many other flyby missions, and
orbiters
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Jupiter and its moons Galileo (1995-2003)
Io (1996)
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Saturn and its moons Cassini (2004 -) Surface
of Titan, Huygens (2005)
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Pluto and Charon
New Horizons launched Jan 2006 due to arrive
2015 Pluto reclassified as a dwarf planet Aug
2006 There are probably no more true planets yet
to be discovered in our solar system
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Planets around other stars

• It is unknown how common it is for stars like the
  sun to have planets
• Discovering extra-solar planets brings us one
  step closer to finding out if there is any other
  life out there

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It is very, very difficult to see planets around
other stars
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Why is it so difficult to see planets around
other stars?

• From the nearest star outside the solar system,
  the sun would be 10 billion times brighter than
  the Earth, a billion times brighter than Jupiter

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Dust in our solar system causes Zodiacal light
Other stars also have disks of orbiting dust
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• Beta Pictoris disk of gas and dust (1984)
• The star is blocked out of the image, making the
  disk visible
• Our own solar system would look similar from far
  away

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Brown Dwarf Gliese 229B (1995) The Brown Dwarf is
larger than a planet, and is about the
smallest thing one can see whilst trying to block
out the starlight
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How to discover a planet?1 Doppler Shift (1995-
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• Although the planet orbits the star, the star
  also moves a little bit due to the planets
  gravity
• When the star moves away from us, its light is
  redshifted
• When it moves towards us, the light is blueshifted

We cannot see any change in the stars light in
this case
The star appears to wobble, because of an unseen
planet
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Bouchy et al (2005)
2 Transit events
The star appears fainter for a short period as a
planet passes in front of it
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3. Microlensing Events

• The gravity of the star and planet acts like a
  lens, magnifying the light from a distant
  background star in the same direction
• Although the alignments are rare, 4 planets have
  been discovered since 2002

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4 Watching the stars position

• Instead of measuring the Doppler shift in the
  stars light, rather measure the stars position
  very accurately.
• The star should wobble due to a planets gravity
  over time
• This method is beginning 2006

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Extra-solar Planet Discovery
208 planets discovered as of October 2006
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Dynamical Effect of Planets

• Sometimes the dust we can observe gives hints
  about possible planets which we cant detect by
  the other methods.

Formalhaut dust ring (2005) Why is the star not
at the center of the dust ring?
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Beta Pictoris
1984
Golimowski et al (2006)

• The dust disk appears warped, possibly due to the
  gravitational effect of planets on the dust

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The future of planet discovery

• Future space telescopes will be able to detect
  smaller planets than ever before
• The goal of discovering an Earth-like planets
  around a Sun-like star should be achieved
  sometime in the next decade

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