Ancestors of the Milky Way

Ancestors of the Milky Way

What were the first galaxies in the Universe like? Current observations can only access a handful of these ancients. However, a new simulation has synthesized millions to better understand the galaxies of 13 billion years ago.

Exploring the Planetary Graveyard

Over the past decade the study of planetary debris at white dwarfs has become an increasingly exciting area. Observations of this debris have allowed us to make unique discoveries about the chemical composition of extrasolar rocky planets, as well as revealing the endpoints of the evolution of planetary systems very similar to our own…

A New Galactic Yardstick

A New Galactic Yardstick

We can measure the expansion of the universe with velocities and distances of extragalactic objects. But measuring distances is tough! The authors of this paper have developed a new technique for measure the distances of AGN using the “echo” of light from heated dust.

Searching for doppelgangers of “Stellar Reionizers”

Searching for doppelgangers of “Stellar Reionizers”

Any photon with a wavelength shorter than 912 angstroms (the Lyman limit) will ionize neutral hydrogen by raising the atom’s electron from the ground state to an unbound state at infinity. From measurements of quasar absorption spectra, we know that the reionization of the intergalactic medium from its previously neutral state (at redshifts greater than 7) to the highly ionized state we observe today was complete by redshift of ~7. However, we still do not know which sources were responsible for producing the ionizing photons.