Download Calibration of Non-Spatially-Filtered Data in Optical

Protoplanetary Disk found Encircling
Mira B
Michael Ireland - Caltech
Co-authors: John Monnier (U. Michigan),
Peter Tuthill (U. Sydney), Richard Cohen
(Keck Observatory)
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.
Mira the ‘Miracle’ Star
Mira
Credit AAVSO Website
• 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, reappearing 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’s 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 you’d form
planets!).
Credit: NASA/CXC/M.Weiss
The Keck Long-Wavelength-Spectrometer
(LWS) “Segment-tilting” Experiment
Programming the Mirror
Richard Cohen (WMKO) wrote low-level ACS Software
One star is split into four images
(blue image falls off detector)
Short-Exposure Images on
Keck-LWS at 10.7 microns
10 arcseconds
10 arcseconds
Mira A and B: A colorful conundrum.
Blue: Hubble Space Telescope (actually blue), Green:
Infrared 10 microns (silicate), Red: Infrared 12 microns
Solution: A large side-illuminated disk around Mira B
Protoplanetary disks usually located where stars are born
Image credit: NASA/HST
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
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.
Mira A and B: Confirm with ISI and Gemini
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.