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The dynamics of a rigid cometary nucleus is described by the evolutions of its center-of-mass and of its rotation state. Solar irradiation that reaches the surface of a cometary nucleus causes the sublimation of volatiles that form the coma…
Using multi-wavelength observations from the Solar Dynamics Observatory (SDO), we investigated the six-month decay process of the solar active region NOAA AR 12738 from April to October 2019. We systematically analyzed the region's…
EX Lup is the prototype of a class of pre-main sequence eruptive stars defined by their repetitive outbursts lasting several months. In 2008 January-September EX Lup underwent its historically largest outburst, brightening by about 4…
The present obliquity of Mercury is very low (less than 0.1 degree), which led previous studies to always adopt a nearly zero obliquity during the planet's past evolution. However, the initial orientation of Mercury's rotation axis is…
(abridged) We aim to derive a robust estimate of the most important parameters describing the physical nature of T CrB, trace the accretion history onto its white dwarf, and account for the unexpected delay in the occurrence of the new…
Solar filaments/prominences exhibit rotational motion during different phases of their evolution from their formation to eruption. We have observed the rotational/vortical motion in the photosphere near the ends of ten filaments during…
Young stars are expected to gain most of their mass by accretion from a disk that forms around them as a result of angular momentum conservation in the collapsing protostellar cloud. Accretion initially proceeds at high rates of…
The unpredictability of solar filament eruptions presents major challenges for forecasting space weather, as such eruptions frequently drive coronal mass ejections (CMEs) that impact the heliosphere. While nearby flux emergence is often…
The present work reports on the discovery of three stars that we have identified to be rotating Sun-like stars, based on rotational modulation signatures inferred from light curves from the CoRoT mission's Public Archives. In our analysis,…
Solar filaments/prominences are common features in the Sun's atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their…
The radio tracking apparatus of the New Horizons spacecraft, currently traveling to the Pluto system where its arrival is scheduled for July 2015, should be able to reach an accuracy of 10 m (range) and 0.1 mm s^-1 (range-rate) over…
The presence of distant protoplanets may explain the observed gaps in the dust emission of protoplanetary disks. Here, we derive a novel analytical model to describe the temporal decay of the pebble flux through a protoplanetary disk as the…
The Sun is believed to have been the recipient of a substantial amount of metal-rich material over the course of its evolution, particularly in the early stages of the Solar System. With a long diffusion timescale, the majority of this…
A significant fraction of hot Jupiters have orbital axes misaligned with their host stars' spin axes. The large stellar obliquities of these giants have long been considered potential signatures of high-eccentricity migration, which is…
We report on the first bird's-eye view of the innermost accretion disk around the high-mass protostellar object G353.273+0.641, taken by Atacama Large Millimter/submillimeter Array long-baselines. The disk traced by dust continuum emission…
Prestellar cores are generally spheroidal, some of which appear oblate while others appear prolate. Very few of them appear circular in projection. Little, however, is understood about the processes or the physical conditions under which…
SMC X-1 is a high-mass X-ray binary showing superorbital modulation with an unstable period. Previous monitoring shows three excursion events in 1996--1998, 2005--2007, and 2014--2016. The superorbital period drifts from >60 days to <40…
We study the formation and long-term evolution of primordial protostellar disks harbored by first stars using numerical hydrodynamics simulations in the thin-disk limit. The initial conditions are specified by pre-stellar cores with…
In the early universe, substantial relative "stream" velocities between the gas and dark matter arise due to radiation pressure and persist after recombination. To asses the impact of these velocities on high-redshift structure formation,…
We studied the creep motion of granular materials in a gradient potential field that is created using a slow spin-up experiment device. Natural sand confined in the acrylic box is spun up by a controlled turntable and the surface flows are…