There’s been so much important news pouring in this month that it’s hard to keep up with it. But despite the flood of information, there’ve been a few especially significant discoveries that I think shouldn’t be overlooked. There are three that I thought deserve special notice:
• On February 13, astronomers announced the discovery of a new solar system that resembles our own more closely than any exoplanetary system that was previously known. The new system, given the unlovely designation of OGLE-2006-BLG-109, is about 5,000 light-years from Earth in the direction of the constellation Scorpius. The home star of this system is about half the mass of the Sun, and thus cooler. It’s orbited by at least two planets, both gas giants, one 0.71 times the mass of Jupiter orbiting at a distance of 2.3 astronomical units (1 AU = 93 million miles), and one that’s 0.27 times Jupiter’s mass and orbiting at a distance of 4.6 AU – both of which now join the nearly 230 exoplanets previously known.
This marvelously specific discovery was made using a new method, called gravitational microlensing. Many exoplanets have been detected by looking for the Doppler shift in a star’s light as an orbiting planet tugs it back and forth. But this method is most sensitive to large Jupiter-like planets in close-in orbits, not the best analogues of our own solar system. The new method relies on a chance alignment of stars from our vantage point, in which the light of the background star is bent and magnified in a telltale way by the gravity of the foreground star. Although not yet sensitive enough to detect terrestrial planets like our Earth, the possibility of such planets in this system hasn’t been ruled out. Since this star is cooler than our Sun, there could be a habitable zone further in than the orbits of the two giant planets.
• On to biology: The peerless Carl Zimmer tells us about a new transitional species in the increasingly complete fossil series that documents the evolution of whales. The 25-million-year-old Aetiocetus provides a key piece in what was a vexing puzzle: how did baleen whales evolve from toothed ancestors?
In the paper, the authors report that Aetiocetus had both teeth and baleen, based on the fossil evidence. Its skull had teeth as well as special bone troughs called nutrient foramina, which supply baleen tissue with blood in modern baleen whales and are not present in modern toothed whales.
• And another transitional fossil – this one a step in the evolution of bats. Named Onychonycteris finneyi, it comes from 52-million-year-old rocks of the Green River formation in Wyoming and is nested more deeply in the bat family tree than any bat species previously known. Although it was capable of flight, it also had several primitive characteristics not found in any living bat, including five well-formed claws on each wing, and an unusual, half-gliding/half-fluttering flying style seen in few modern bats. Based on its inner ear, it also lacked the ability to echolocate. Carl Zimmer, again, writes that it reminds him of Archaeopteryx, another electrifying specimen that gave us a glimpse into the progress of evolution over deep time.