Ripples in gas at the outer disc of our galaxy have puzzled astronomers since they were first revealed by radio observations a decade ago. Now, astronomers believe they have found the culprit — a dwarf galaxy, containing dark, unseen material, which skimmed the outskirts of the Milky Way a few hundred million years ago. This method to characterise dark matter marks first real application of galactoseismology.
A team of astronomers, using the Gemini Planet Imager (GPI) on the Gemini South telescope in Chile, has given us our best view yet of an exoplanet moving in its orbit around a distant star. A series of images captured between November 2013 and April 2015 shows the exoplanet β Pictoris b as it moves through 1½ years of its 22-year orbital period.