Protoplanetary Disk found Encircling Mira B

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Protoplanetary Disk found Encircling Mira B

• Michael Ireland - Caltech
• Co-authors John Monnier (U. Michigan), Peter
  Tuthill (U. Sydney), Richard Cohen (Keck
  Observatory)

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Summary

• Planets form in dusty protoplanetary disks
  around young stars.
• What we found Evidence for a large dusty disk
  around the companion to Mira, a dying star.
• This is a new type of protoplanetary disk a
  planetary system that can be reborn when its
  companion star dies.

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Mira the Miracle Star

• In the constellation Cetus, Mira was discovered
  as a variable star in 1596, demonstrating that
  the stars were not invariable as Aristotle had
  thought.
• Visible to the naked eye for a month at a time,
  Mira periodically becomes 1000 times fainter,
  re-appearing in 11 months.
• We now know that Mira is a star like the sun in
  its death throes, pulsating and ejecting its
  outer layers on its way to becoming an
  earth-sized white dwarf.

Mira
Credit AAVSO Website
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Miras Companion, Mira B What we knew before
While Mira A was at its faintest, Mira B has been
detected in blue and ultraviolet light. So
astronomers have generally thought that Mira B
was only a hot, compact object (not the kind of
place youd form planets!).
Credit NASA/CXC/M.Weiss
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The Keck Long-Wavelength-Spectrometer (LWS)
Segment-tilting Experiment
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Programming the Mirror
One star is split into four images (blue image
falls off detector)
Richard Cohen (WMKO) wrote low-level ACS Software
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Short-Exposure Images on Keck-LWS at 10.7 microns
10 arcseconds
10 arcseconds
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Mira A and B A colorful conundrum.
Blue Hubble Space Telescope (actually blue),
Green Infrared 10 microns (silicate), Red
Infrared 12 microns
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Solution A large side-illuminated disk around
Mira B
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Protoplanetary disks usually located where stars
are born
Image credit NASA/HST
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Mira B A born-again protoplanetary disk.
By comparing the measured size of the disk to
predictions, and by re-analysing Hubble Space
Telescope spectra, we can show that Mira B is an
ordinary star 0.5-0.7 times as massive as the sun.
Image credit NASA Origins
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Mira B A once-off weird system, or something
common?

• Two out of three stars systems are actually
  double-stars. One in four will end up like Mira A
  and B.
• Today in our neighborhood, stars die 4 times
  more often than they are born.
• If we turn our telescopes to overlooked nearby
  stars with white dwarf companions (like Mira A
  when it dies), we should be able to find many
  systems that formed like Mira B.
• So We discovered that around Mira B is a new
  kind of protoplanetary disk, formed from the wind
  of a dying star. This is the first detection of
  this kind of disk.

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Mira A and B Confirm with ISI and Gemini
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Mira A and B Confirm with ISI and Gemini
Infrared Spatial Interferometer (Charlie Townes)
early 1990s measurement. Confirms that the
clump is moving against the wind - so must be
connected to Mira B.