ArXiv recap

by

Chris Ormel

(favorite planet: TRAPPIST 1e)

  1. Barclay et al. (2109.14608):
    Stellar surface inhomogeneities as a potential source of the atmospheric signal detected in the K2-18 b transmission spectrum
  2. Millholland & Winn (2110.01466):
    Split Peas in a Pod: Intra-System Uniformity of Super-Earths and Sub-Neptunes
  3. Yamachuchi et al. (2110.00974):
    ALMA Super-resolution Imaging of T Tau: r = 12 au Gap in the Compact Dust Disk around T Tau N
  4. Asphaug et al. (2110.00222)
    Collision Chains among the Terrestrial Planets. III. Formation of the Moon
  5. Kobayashi & Tanaka (2110.00919)
    Rapid formation of Gas Giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores

Barclay et al. — water in the K2-18 system?

K2-18
M2.8 dwarf star
K2-18 c
~6ME planet at P=9d
(non-transiting)
K2-18 b
~9ME, 2.7 RE transiting planet at P=33d
Detection of H2O! by transmission spectroscopy
artist sketch of K2-18 (c) — ESA/Hubble/M. Kornmesser

transmission spectroscopy

(c) scientist live
"
Best fit
atmosphere model
HST data points
H2O vibrational feature
Benneke et al. (2019). See also Tsiaras et al. (2019)
 

Barclay et al. (2019) claim that the H2O feature could be created by starspots alone!

Barclay et al. — spot spectrum differs from photosphere
Barclay et al. — starspots+transit simulations

Barclay et al. claim that the limited (8) number of transits may mimic the H2O transmission signal.

"Extraordinary claims require extraordinary evidence" (Carl Sagan)

Millholland & Winn

Split Peas in a Pod

pea
pod
split
pea

Split peas in a pod

Kepler database
super-Earth
sub-Neptune
Sample of Np >= 4-planet systems

Millholland & Winn argue that intra-system uniformity is stronger among the super-Earths (SE) and sub-Neptune (SN) subgroups

Split peas in a pod

Rp,i is the radius of planet i with Pi < Pj

Millholland & Winn argue that intra-system uniformity is stronger among the super-Earths (SE) and sub-Neptune (SN) subgroups

However are these correlations stronger than those arising from the null hypothesis?

The authors construct a (custom) randomized sample while preserving the so-called "evaporation valley"

Split peas in a pod

width is large, MAD=0.42
more narrow
distribution, MAD=0.19

Millholland & Winn argue that intra-system uniformity is stronger among the super-Earths (SE) and sub-Neptune (SN) subgroups

Split peas in a pod

Millholland & Winn argue that intra-system uniformity is stronger among the super-Earths (SE) and sub-Neptune (SN) subgroups


Is theirs convincing?

  • M&W argue that correlation becomes 2x as strong after splitting the peas
  • It makes sense that MAD (~spread) decreases if you cut the sample
  • The significance of their result rather decreases

Yamaguchi et al — "Let there be rings"

T Tau N
T Tau system using traditional CLEAN algorithm

Yamaguchi et al — "Let there be rings"

T Tau N
T Tau system using traditional CLEAN algorithm
T Tau N
T Tau Sa+Sb
beam
superresolution magic using Sparse Modelling (SpM) image reconstruction

Yamaguchi et al — "Let there be rings"

T Tau N
T Tau Sa+Sb
beam
superresolution magic using Sparse Modelling (SpM) image reconstruction
zoom in: a ring is born

...let there be planets!

zoom in: a ring is born
ring modelled due to a Saturn-mass planet

Asphaug et al.: origin of the Moon

Canup (2012). You see here an SPH simulation of proto-Earth colliding with Theia

Asphaug et al.: origin of the Moon

Canup (2012). You see here an SPH simulation of proto-Earth colliding with Theia

This is the giant impact model for the formation of the Moon-Earth system.

It explains many properties very well, e.g.:
  • evidence for Lunar Magma Ocean (LMO)
  • similar orientations of Earth and Moon spin
  • high A.M. in Earth-Moon system
  • Moon has a small iron core
  • Moon is depleted in volatiles

Asphaug et al. highlight two key drawbacks of the standard model:

  1. the giant impact model only works at very specific combinations of (low) impact velocities and impact angles
  2. the composition of Earth and Moon is too similar (e.g., 17O, Ti, Cr, W isotopes)

Asphaug et al.'s new idea: two collisions

First a "hit-and-run" collision at moderate velocity, followed by a later merger

Asphaug et al.'s new idea: two collisions

o
o
"graze-and-merge"
standard model
"
"
"hit-and-run" model
works for a wider
parameter space

Asphaug et al.'s new idea: two collisions

Is it more likely and a better model?

  • May better mix material better
  • 2nd collision can happen at lower velocity

but:

  • 2nd collision does not always occur; Theia may end up in Venus
  • still need much tuning for 2nd collision (I guess)...
o
o
"
"

Kobayashi & Tanaka: (Pebble-free) Jupiter formation

They perform a (rather classical) planet-formation simulations, solving for

The model includes:

  • coagulation (but no fragmentation)
  • planetesimal formation (by crossing St=1 barrier!)
  • migration of pebbles (drift), planetesimals, and planets (Type I)
  • gravitational focusing (runway growth)
  • atmosphere enhancement of Rp
560 yr
2.1 kyr
15 kyr
56 kyr
0.12 Myr
0.21 Myr
10 ME
1 ME
0.1 ME
drifting/growing
(fluffy) pebbles)
560 yr
2.1 kyr
15 kyr
56 kyr
0.12 Myr
0.21 Myr
10 ME
1 ME
0.1 ME
drifting/growing
(fluffy) pebbles)
drifting dust
planetesimals
St=1 is
crossed
560 yr
2.1 kyr
15 kyr
56 kyr
0.12 Myr
0.21 Myr
10 ME
1 ME
0.1 ME
drifting/growing
(fluffy) pebbles)
drifting dust
planetesimals
St=1 is
crossed
planetesimals
protoplanets
runaway growth
oligarchic
growth

Better than Pebble Accretion?

Accretion
efficiency
Pebble accretion (Ormel & Liu)
"Big Pebble accretion"
(Okamura & Kobayashi)
?

the end