An M-class dwarf star such as Gliese 581 has a much lower mass than the Sun, causing the core region of the star to fuse hydrogen at a significantly lower rate. From the apparent magnitude and distance, astronomers have estimated an effective temperature of 3200 K and a visual luminosity of 0. 2% of that of the Sun. However, a red dwarf such as Gliese 581 radiates primarily in the near infrared, with peak emission at a wavelength of roughly 830 nm (estimated using Wien’s displacement law, which assumes the star radiates as a black body), so such an estimate will underestimate the star’s total luminosity. (For comparison, the peak emission of the Sun is roughly 530 nm, in the middle of the visible part of the spectrum. ) When radiation over the entire spectrum is taken into account (not just the part that humans are able to see), something known as the bolometric correction, this star has a bolometric luminosity 1. 3% of the Sun’s total luminosity. A planet would need to be situated much closer to this star in order to receive a comparable amount of energy as the Earth. The region of space around a star where a planet would receive roughly the same energy as the Earth is sometimes termed the “Goldilocks Zone”, or, more prosaically, the habitable zone. The extent of such a zone is not fixed and is highly specific for each planetary system. Gliese 581 is a very old star. Its slow rotation makes it very inactive, making it better suited than most red dwarfs for having habitable planets.
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. Only recently have space missions begun to solve this beguiling Solar System mystery--that a small number of distant moons have been successfully hiding, from the curious eyes of astronomers, life-sustaining liquid water beneath secretive shells of ice. The moon plays a large role in astrology and astrological phenomena. The position and phase of the moon influences the other aspects of astrology, including sun signs and planetary movements. In fact, the moon influences other aspects of astrology as a whole.