The Smallest Planet Orbiting the Smallest Star
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Transcript of The Smallest Planet Orbiting the Smallest Star
The Smallest Planet Orbiting the Smallest Star
David BennettUniversity of Notre Dame
for the MOA & OGLE Collaborationsmobile phone: 574-315-6621
Summary of Finding
• MOA-2007-BLG-192Lb is a ~3 Earth-mass planet– this is the smallest discovered to date
• Its host star has a mass of 6 3% of the mass of the Sun– Most likely, it is < 8% of a Solar mass, which is too
small to sustain nuclear reactions - a brown dwarf• The system is at a distance of 3000 light years• The planet’s orbital radius is about the same as
that of Venus (70% of the Earth-Sun distance)
David Bennett - Smallest Planet Orbits Smallest Star
Host Color Is Probably Magenta
• “Brown” Dwarfs are magenta
• Adam Burrows et al (2001) (520-603-3297)
• due to atmospheric absorption by Sodium and Potassium
David Bennett - Smallest Planet Orbits Smallest Star
Possibly a Low-Mass Red-Dwarf Star
Future observations with the Hubble Space Telescope or the European Southern Observatory’s Very Large Telescope will decide this issue.
David Bennett - Smallest Planet Orbits Smallest Star
The Microlensing Method
• Uses a background star as a source of light
• Gravitational field of star and planet act as a lens
• requires no light from the planetary host
• Observed signal is changing magnification
• Required alignment is very rare, so the very dense Galactic bulge fields are observed
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Source Star Moves Across Lens Magnification Pattern
Observed brightness changes as source star crosses lens system magnification pattern. (credit: Fumio Abe, MOA Collaboration)
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Observed Light Curve
• planetary signal captured by MOA
• due to new wide field-of-view telescope and camera
David Bennett - Smallest Planet Orbits Smallest Star
New MOA Telescope Enabled Discovery
• 1.8m MOA-2 telescope– Mt. John Observatory, NZ
• MOA-cam3 CCD Camera– Images 2.2 sq. deg.– 13 times the area of the full
moon• Entire Galactic Bulge
imaged every hour– All microlensing events
monitored for planets• Similar telescopes are
needed in Chile (OGLE-IV) and South Africa
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Comparison to Other Exoplanets
Microlensing discoveries in red, transit discoveries in blue and Doppler discoveries in black. Letters indicate Solar System planets. The snow-line relates to the conditions
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snow at t = 1 Myr
steam at t = 1 Myr
Credits & Further Info
for further info, contact David Bennett (cell phone: 574-315-6621) or go to http://www.nd.edu/~bennett/moa07blg192/
Scientific Paper to be published in the Astrophysical Journal (arXiv:0806.0025)Authors:D.P. Bennett1, I.A. Bond1, A. Udalski2, T. Sumi1, F. Abe1, A. Fukui1, K. Furusawa1, J.B. Hearnshaw1, S. Holderness1, Y. Itow1, K. Kamiya1, A.V. Korpela1, P.M. Kilmartin1, W. Lin1, C.H. Ling1, K. Masuda1, Y. Matsubara1, N. Miyake1, Y. Muraki1, M. Nagaya1, T. Okumura1, K. Ohnishi1, Y.C. Perrott1, N.J. Rattenbury1, T. Sako1, To. Saito1, S. Sato1, L. Skuljan1, D.J. Sullivan1, W.L. Sweatman1, P.J. Tristram1, P.C.M. Yock1, M. Kubiak2, M.K. Szymanski2, G. Pietrzynski2, I. Soszynski2, O. Szewczyk2, L. Wyrzykowski2, K. Ulaczyk2, V. Batista3, J.P. Beaulieu3, S. Brillant3, A. Cassan3, P. Fouque3, P. Kervella, D. Kubas3, and J.B. Marquette3
1MOA Collaboration2OGLE Collaboration3PLANET CollaborationUS effort funded by the NSF and NASA
David Bennett - Smallest Planet Orbits Smallest Star