58 research outputs found
Was Planet 9 captured in the Sun’s natal star-forming region?
The presence of an unseen ‘Planet 9’ on the outskirts of the Solar system has been invoked
to explain the unexpected clustering of the orbits of several Edgeworth–Kuiper Belt Objects.
We use N-body simulations to investigate the probability that Planet 9 was a free-floating
planet (FFLOP) that was captured by the Sun in its birth star formation environment. We find
that only 1–6 per cent of FFLOPs are ensnared by stars, even with the most optimal initial
conditions for capture in star-forming regions (one FFLOP per star, and highly correlated
stellar velocities to facilitate capture). Depending on the initial conditions of the star-forming
regions, only 5–10 of 10 000 planets are captured on to orbits that lie within the constraints for
Planet 9. When we apply an additional environmental constraint for Solar system formation
– namely the injection of short-lived radioisotopes into the Sun’s protoplanetary disc from
supernovae – we find the probability for the capture of Planet 9 to be almost zero
Mass segregation in star clusters is not energy equipartition
Mass segregation in star clusters is often thought to indicate the onset of energy equipartition, where the most massive stars impart kinetic energy to the lower-mass stars and brown dwarfs/free floating planets. The predicted net result of this is that the centrally concentrated massive stars should have significantly lower velocities than fast-moving low-mass objects on the periphery of the cluster. We search for energy equipartition in initially spatially and kinematically substructured N-body simulations of star clusters with N = 1500 stars, evolved for 100 Myr. In clusters that show significant mass segregation we find no differences in the proper motions or radial velocities as a function of mass. The kinetic energies of all stars decrease as the clusters relax, but the kinetic energies of the most massive stars do not decrease faster than those of lower-mass stars. These results suggest that dynamical mass segregation -- which is observed in many star clusters -- is not a signature of energy equipartition from two-body relaxation
Atmosphere Retrieval of Planetary Mass Companions with the APOLLO Code:A Case Study of HD 106906b and Prospects for JWST
Disks around T Tauri Stars with SPHERE (DARTTS-S):I. SPHERE/IRDIS Polarimetric Imaging of Eight Prominent T Tauri Disks
Disks around T Tauri Stars with SPHERE (DARTTS-S):I. SPHERE/IRDIS Polarimetric Imaging of Eight Prominent T Tauri Disks
We present the first part of our DARTTS-S (Disks ARound TTauri Stars with
SPHERE) survey: Observations of 8 TTauri stars which were selected based on
their strong (sub-)mm excesses using SPHERE / IRDIS polarimetric differential
imaging (PDI) in the J and H bands. All observations successfully detect the
disks, which appear vastly different in size, from 80 au in scattered
light to 400 au, and display total polarized disk fluxes between 0.06% and
0.89% of the stellar flux. For five of these disks, we are able to determine
the three-dimensional structure and the flaring of the disk surface, which
appears to be relatively consistent across the different disks, with flaring
exponents between 1.1 and 1.6. We also confirm
literature results w.r.t. the inclination and position angle of several of our
disk, and are able to determine which side is the near side of the disk in most
cases. While there is a clear trend of disk mass with stellar ages (1
Myr to 10 Myr), no correlations of disk structures with age were found.
There are also no correlations with either stellar mass or sub-mm flux. We do
not detect significant differences between the J and H bands. However, we note
that while a high fraction (7/8) of the disks in our sample show ring-shaped
sub-structures, none of them display spirals, in contrast to the disks around
more massive Herbig Ae/Be stars, where spiral features are common.Comment: 31 pages, 12 figure
High-contrast imaging constraints on gas giant planet formation - The Herbig Ae/Be star opportunity
Planet formation studies are often focused on solar-type stars, implicitly
considering our Sun as reference point. This approach overlooks, however, that
Herbig Ae/Be stars are in some sense much better targets to study planet
formation processes empirically, with their disks generally being larger,
brighter and simply easier to observe across a large wavelength range. In
addition, massive gas giant planets have been found on wide orbits around early
type stars, triggering the question if these objects did indeed form there and,
if so, by what process. In the following I briefly review what we currently
know about the occurrence rate of planets around intermediate mass stars,
before discussing recent results from Herbig Ae/Be stars in the context of
planet formation. The main emphasis is put on spatially resolved polarized
light images of potentially planet forming disks and how these images - in
combination with other data - can be used to empirically constrain (parts of)
the planet formation process. Of particular interest are two objects, HD100546
and HD169142, where, in addition to intriguing morphological structures in the
disks, direct observational evidence for (very) young planets has been
reported. I conclude with an outlook, what further progress we can expect in
the very near future with the next generation of high-contrast imagers at 8-m
class telescopes and their synergies with ALMA.Comment: Accepted by Astrophysics and Space Science as invited short review in
special issue about Herbig Ae/Be stars; 12 pages incl. 5 figures, 2 tables
and reference
Mid-infrared interferometry of massive young stellar objects. I. VLTI and Subaru observations of the enigmatic object M8E-IR
Evolution of protoplanetary disks from their taxonomy in scattered light: Group I vs. Group II
Large interferometer for exoplanets: VIII. Where is the phosphine? Observing exoplanetary PH3 with a space-based mid-infrared nulling interferometer
Stars and planetary system
Azimuthal asymmetries in the debris disk around HD 61005:A massive collision of planetesimals?
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