Asteroseismic studies, chromospheric activity, and stellar rotation (gyrochronology) are all consistent with the Alpha Centauri system being similar in age to, or slightly older than, the Sun. Asteroseismic analyses that incorporate tight observational constraints on the stellar parameters for the Alpha Centauri stars have yielded age estimates of 4. 85±0. 5 Gyr, 5. 0±0. 5 Gyr, 5. 2 ± 1. 9 Gyr, 6. 4 Gyr, and 6. 52±0. 3 Gyr. Age estimates for the stars based on chromospheric activity (Calcium H & K emission) yield 4. 4 ± 2. 1 Gyr, whereas gyrochronology yields 5. 0±0. 3 Gyr. Stellar evolution theory implies both stars are slightly older than the Sun at 5 to 6 billion years, as derived by their mass and spectral characteristics.
The largest, shining object in Earth's starlit night sky, our Moon has long been the source of mystery, myth, and poetry--a captivating inspiration for those who stare at the sky in wonder. But Earth's Moon is a very real object--the only body beyond our own planet that we have actually set foot upon, leaving our lingering footprints in its distant, alien dust. Earth's Moon has been with us almost from the very beginning, and even though it is our planet's closest companion in space, it has nonetheless managed to keep some of its ancient secrets very well. In September 2015, astronomers released a new study that shed light on Earth's bewitching companion's ancient and secretive past. Although our Moon now appears to be unchanging, as if it has always been exactly the same as it appears now--going through its beautiful and, yet, familiar phases, and controlling our ocean tides--in the distant past, things were actually very different. "Since time immemorial, humanity has looked up and wondered what made the man in the Moon. We know the dark splotches are large, lava-filled, impact basins that were created by asteroid impacts about four billion years ago. GRAIL data indicate that both the near side and the far side of the Moon were bombarded by similarly large impactors, but they reacted to them much differently," noted Dr. Maria Zuber, GRAIL principal investigator, in a November 7, 2013 NASA Jet Propulsion Laboratory (JPL) Press Release. Dr. Zuber is of the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts. The JPL is located in Pasadena, California. It is not a very expensive stone and is made into necklaces or bigger pieces for jewelry purposes. I especially like the deep, dark blue version with golden pyrite sprinkles creating very unique patterns mined only in Afghanistan. The lighter blue, grayish variety is found in Chile.