Something’s Fishy in Fomalhaut
Something’s Fishy in Fomalhaut
Allegheny Observatory Public Lecture Series
Dave Nero, Ph.D. Department of Physics and Astronomy
1/30 Something’s Fishy in Fomalhaut Outline
1 Discovery of Planet Fomalhaut b Fomalhaut the star How to Find a Planet The First Photograph of a Planet Around Another Star
2 Controversy and Doubt How Did Fomalhaut b Form? Why is it so Bright? Why is it Invisible?
3 The “Zombie Planet” So What’s in the Pictures?
2/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b Fomalhaut
The Fish’s Mouth The Southern Fish
3/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b Fomalhaut
17th brightest star in the sky 25 light-years away Type A star
4/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b What Makes Fomalhaut Interesting?
Images of the Fomalhaut Debris Disk
5/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b Debris Disks and Planets
The Sun’s Debris Disk
6/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b How to Find a Planet
From Easiest to Hardest Transits (video) Doppler Shift (demo) Direct Imaging
7/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b Space Searched So Far
See Exoplanet Encyclopedia (http://exoplanet.eu) for the current list. 8/30 Something’s Fishy in Fomalhaut Discovery of Planet Fomalhaut b First Directly Imaged Exoplanet
9/30 Something’s Fishy in Fomalhaut Controversy and Doubt Outline
1 Discovery of Planet Fomalhaut b Fomalhaut the star How to Find a Planet The First Photograph of a Planet Around Another Star
2 Controversy and Doubt How Did Fomalhaut b Form? Why is it so Bright? Why is it Invisible?
3 The “Zombie Planet” So What’s in the Pictures?
10/30 Something’s Fishy in Fomalhaut Controversy and Doubt Planet Formation in the Solar System
11/30 Something’s Fishy in Fomalhaut Controversy and Doubt Core Accretion
Timeline
12/30 Something’s Fishy in Fomalhaut Controversy and Doubt Problem: Protoplanetary Disk Lifetimes
It takes about 10 Myrs to form Jupiter This time INCREASES with distance from the star
13/30 Something’s Fishy in Fomalhaut Controversy and Doubt Solution 1: Gravitational Instability
14/30 Something’s Fishy in Fomalhaut Controversy and Doubt Disk Fragmentation
15/30 Something’s Fishy in Fomalhaut Controversy and Doubt Disk Fragmentation
16/30 Something’s Fishy in Fomalhaut Controversy and Doubt Disk Fragmentation
17/30 Something’s Fishy in Fomalhaut Controversy and Doubt Disk Fragmentation
18/30 Something’s Fishy in Fomalhaut Controversy and Doubt Disk Fragmentation
19/30 Something’s Fishy in Fomalhaut Controversy and Doubt Taking it Further: Dust Settling
How Close to the Star? Star 10 K Background
20 0.5 Myr 5 Myr 1 Myr 10 Myr 18 Gas Only τ (Optically Thin) g 16
14
Gas + Dust τ0 12
10 [AU] frag r 8 Gas Only
6
4 Star 10 K Background 0.1 0.2 0.5 1 2 5 M⋆ [M⊙]
20/30 Something’s Fishy in Fomalhaut Controversy and Doubt Solution 2: Planet Migration
Type 1 (< 10 Earth-Masses) Type 2 (> 10 Earth-Masses)
21/30 Something’s Fishy in Fomalhaut Controversy and Doubt Solution 3: Planet-Planet Scattering
Nice Model: Maybe Uranus and Neptune switched places
Explains: Kuiper belt orbital resonances with Neptune Lack of small objects in outer Solar System Late heavy bombardment (video) 22/30 Something’s Fishy in Fomalhaut Controversy and Doubt Problem: Why is Fomalhaut b so Bright?
The Hubble image shows visible light Must be reflected from the star Fomalhaut b must be big (radius)
The debris disk is intact If Fomalhaut b was too big, it would disrupt the debris disk Fomalhaut b must be small (mass)
23/30 Something’s Fishy in Fomalhaut Controversy and Doubt Solution: Rings
24/30 Something’s Fishy in Fomalhaut Controversy and Doubt Problem: Fomalhaut b Should be Bright in IR Light
25/30 Something’s Fishy in Fomalhaut Controversy and Doubt BIG Problem: Fomalhaut b is Missing in IR Light
It Should be at Arrow 1
26/30 Something’s Fishy in Fomalhaut The “Zombie Planet” Outline
1 Discovery of Planet Fomalhaut b Fomalhaut the star How to Find a Planet The First Photograph of a Planet Around Another Star
2 Controversy and Doubt How Did Fomalhaut b Form? Why is it so Bright? Why is it Invisible?
3 The “Zombie Planet” So What’s in the Pictures?
27/30 Something’s Fishy in Fomalhaut The “Zombie Planet” New Observations
28/30 Something’s Fishy in Fomalhaut The “Zombie Planet” What is it?
Three Related Possibilities A planet with a huge ring? A planet surrounded by a cloud of debris? The remnants of a catastrophic collision?
Fomalhaut c? There must be at least one more planet to explain the debris disk We never found the planet that we went looking for in the first place!
29/30 Something’s Fishy in Fomalhaut The “Zombie Planet” Questions?
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