Extragalactic radio sources as lighthouses for SETI

The search for extraterrestrial intelligence (SETI) is one of the most ambitious scientific endeavors. It aims at detecting signals produced intentionally or unintentionally by extraterrestrial civilizations ([Siemion et al., 2013](http://arxiv.org/abs/1412.4867)). The Galaxy, however, is vast a...

By Jorge I. Zuluaga

Sulfur-Bearing Polycyclic Aromatic Hydrocarbons in Interstellar Environments

Polycyclic aromatic hydrocarbons (PAHs) are widely studied in an astrophysical context. Studies have also been performed on nitrogen-bearing PAH species ([Hudgins+2005](http://adsabs.harvard.edu/abs/2005ApJ...632..316H)) and unsuccessful searches have been performed for interstellar nitrogen-bea...

By Mark Hammonds

Shovel-ready for Gaia DR2: Find hypervelocity stars from M31/LMC

Hypervelocity stars move with extremely large Galactocentric velocities (~1000 km/s) and are found from their anomalous velocities, ages, and metallicities. These stars are thought to have interacted with the supermassive black hole at the center of the Milky Way, given that they are seen moving...

By Adrian Price-Whelan

Searching for "Tabby's Star" Analogs in Stripe 82

["Tabby's Star"](http://adsabs.harvard.edu/abs/2016MNRAS.457.3988B) is an anomalous F star with repeated short-term variability, and a steady [3% dimming over 4-years](http://adsabs.harvard.edu/abs/2016arXiv160801316M). The star spent [~8%](https://twitter.com/Nighthawk_Black/status/762410345411...

By James Davenport, John Ruan

The NASA K2 Mission has yet to observe an analog of Tabby's Star

Tabby's Star is a main sequence F-class star ([KIC 8462852](https://en.wikipedia.org/wiki/KIC_8462852)) observed by the NASA Kepler spacecraft to undergo significant aperiodic dimming activity across a four year baseline. The light curve was noted as novel amongst a pool of ~150,000 targets thro...

By Daryll LaCourse

The Galactic Astigmatism: Constraining the Milky Way Dark Matter Halo Using Ultra-Weak Lensing

An astigmatism is defined as an asymmetry of the front of the eye, causing light to not focus on a single point. Because the Sun is located ~8kpc off-center in the Milky Way, the integrated mass density of galactic dark matter varies significantly along different lines of sight. As a result, the...

By James Davenport

Supercritical Exoplanetary Atmospheres as Potential Habitats for Extraterrestrial Aeroplankton

An increasingly familiar class of exoplanets amongst those being continually discovered is the "Super-Earth" ([Valencia+2007](http://iopscience.iop.org/0004-637X/656/1/545/)), with a mass intermediate between Earth and Neptune. These have been found inside habitable zones ([Udry+2007](http://www...

By Mark Hammonds

On the Impossibility of Aggregating Individual Cloud Accretion Rates

The rate of accretion onto the Milky Way (MW) by an individual cloud (or satellite) can be written as dM/dt = M v / R, where M is the cloud mass, v the cloud velocity toward the MW, and R is the distance from the cloud to the MW. Over the time t = R / v a mass M will accrete. This rate can be ev...

By Joshua Peek

Beyond Gaia: A Deep-Space Astrometric Mission To Obtain ~1% Parallax Distances at 10 kiloparsecs

The [Gaia space telescope](https://arxiv.org/abs/1609.04153) is currently measuring parallax distances for Galactic stars with ~1% precision out to ~1kpc. This will be a revolutionary data set, but order-of-magnitude improvements are possible with a next-generation mission that is already achiev...

By Khee-Gan Lee