Related papers: Empirical Limits on the Russell Conjecture
As the only dark matter candidate that does not invoke a new particle that survives to the present day, primordial black holes (PBHs) have drawn increasing attention recently. Up to now, various observations have strongly constrained most…
The population of the Kuiper Belt within 50 AU of the Sun has likely been severely depleted by gravitational perturbations from the giant planets, particularly Neptune. The density of Kuiper Belt objects is expected to be two orders of…
Observations of Pluto and its solar-tidal stability zone were made using the Advanced Camera for Surveys' (ACS) Wide Field Channel (WFC) on the Hubble Space Telescope on UT 2005 May 15 and UT 2005 May 18. Two small satellites of Pluto,…
The nature of "Little Red Dots" and their relation to other forms of accreting supermassive black holes remain an open question. Here we report the discovery of a Little Red Dot at $z=7.3$. It is attenuated by moderate amounts of dust, $A_V…
The outer solar system provides a unique, quiet vantage point from which to observe the universe around us, where measurements could enable several niche astrophysical science cases that are too difficult to perform near Earth. NASA's New…
Space missions to NEOs are being planned at all major space agencies, and recently a manned mission to an NEO was announced as a NASA goal. Efforts to find and select suitable targets (plus backup targets) are severely hampered by our lack…
Using a large suite of n-body simulations, we explore the discovery space for new satellites in the Pluto-Charon system. For the adopted masses and orbits of the known satellites, there are few stable prograde or polar orbits with semimajor…
We searched the Sloan Digital Sky Survey for outer halo globular clusters (GCs) around M31. Our search of non-stellar objects, within the limits 0.3 < (g-i)o < 1.5 and 14.0 < ro < 19.0 concentrated in some remote areas of the extended halo,…
We report new precision measurements of the properties of our Galaxy's supermassive black hole. Based on astrometric (1995-2007) and radial velocity (2000-2007) measurements from the W. M. Keck 10-meter telescopes, a fully unconstrained…
We aim to illustrate the potentiality of the Advanced Large, Homogeneous Area, Medium-Band Redshift Astronomical (ALHAMBRA) survey to investigate the high redshift universe through the detection of quasi stellar objects (QSOs) at redshifts…
We report the results of Keck L'-band non-redundant aperture masking of HR 8799, a system with four confirmed planetary mass companions at projected orbital separations of 14 to 68 AU. We use these observations to place constraints on the…
Using the global 21-cm signal measurement by the EDGES collaboration, we derive constraints on the fraction of the dark matter that is in the form of primordial black holes (PBHs) with masses in the range $10^{15}$-$10^{17}\,$g. Improving…
The Habitable Zone (HZ) is defined by the possibility of sustaining liquid water on a planetary surface. In the Solar System, the HZ for a conservative climate model extends approximately between the orbits of Earth and Mars. We elaborate…
Comet Hale--Bopp (C/1995 O1) has been the single most significant comet encountered by modern astronomy, still having displayed significant activity at 25.7 AU solar distance in late 2007. It is a puzzling question when and where this…
We present a new space mission concept that is capable of finding, detecting, and tracking 90% of near-Earth objects (NEO) with H magnitude of $\rm H\leq22$ (i.e., $\sim$140 m in size) that are potentially hazardous to the Earth. The new…
Many asteroids show indications they have undergone impacts with meteoroid particles having radii between 0.01 m and 1 m. During such impacts, small dust grains will be ejected at the impact site. The possibility of these dust grains (with…
The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based,…
We consider the Roche critical density (rho_Roche), the minimum density of an orbiting object that, at a given distance from its planet, is able to hold itself together by self-gravity. It is directly related to the more familiar "Roche…
We conducted a satellite search around the dwarf planet 1 Ceres using Hubble Space Telescope and ground-based Palomar data. No candidate objects were found orbiting Ceres in its entire stability region down to ~500km from the surface of…
The study of small ($<$300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent.…