An international team of researchers have found a new way to measure the pull of gravity at the surface of a star. The new method allows scientists to measure surface gravity with an accuracy of about four percent, for stars too distant and too faint to apply current techniques. For remote stars with planets orbiting them, this information is key in determining whether any of those planets can harbour life.
While 2014 was the year the Rosetta spacecraft celebrated making it into orbit around a comet, 2015 was the year it got down to some serious hard work. Its comet, with the tongue-twisting name 67P/Churyumov–Gerasimenko, made its closest approach (186 million kilometres) to the Sun, a period known as perihelion when the comet would be expected to be at its most active. Rosetta was there to witness this.
At number 10 in our top stories of the year: one of the most perplexing problems of modern cosmology and astrophysics was solved. For decades scientists had puzzled over where all the lithium in stars had disappeared to. Fortunately for the Big Bang model, Italian scientists at the International School for Advanced Studies in Trieste discovered that it was the stars that were to blame.