Wednesday, August 29, 2012

Democritus Guesses Again!

"He [Democritus] said that the ordered worlds are boundless and differ in size, and that in some there is neither sun nor moon, but that in others, both are greater than with us, and yet with others more in number. And that the intervals between the ordered worlds are unequal, here more and there less, and that some increase, others flourish and others decay, and here they come into being and there they are eclipsed. But that they are destroyed by colliding with one another. And that some ordered worlds are bare of animals and plants and all water." -- Hippolytus, priest, 2nd century

NASA discovers first two-planet system orbiting twin suns.
It's been almost a year ago since we made our first discovery of an exoplanet orbiting two suns, prompting everyone to compare it to the planet Tattooine in the "Star Wars" universe. A handful of other planets orbiting two stars have been found since then, but the Kepler-47 system is special: It's the first twin star system discovered that has not one but two planets in orbit. This unusual system was discovered using data from the Kepler telescope that's responsible for numerous exoplanet finds. According to Kepler mission principal investigator William Borucki, "Unlike our sun, many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been — do they have planets and planetary systems? This Kepler discovery proves that they do." The first star in the system is comparable to our sun in size, although only 84% as bright. The other is a dim star, measuring a third of the sun's size and only 1% as bright. Kepler-47b, one of the two planets that most probably has a blazing hot atmosphere due to its proximity to the stars, completes its orbit within 50 days. With a radius three times larger than Earth's, it's currently the smallest planet known to orbit two stars. The other planet, called Kepler-47c, is located much farther away and completes its orbit around the stars in 303 days. But even though it's located in the system's habitable zone, it's unlikely to support life — the planet is a gas giant that's slightly larger than Neptune. Kepler-47's discovery means exoplanet hunters now have to pay special attention to clusters of stars that may be hiding more than one planet. As Borucki said: "In our search for habitable planets, we have found more opportunities for life to exist."

Friday, August 17, 2012

Augustine of Hippo: On Changes of Venus

From the book of Marcus Varro, entitled, Of the Race of the Roman People, I cite word for word the following instance: "There occurred a remarkable celestial portent; for Castor records that, in the brilliant star Venus, called Vesperugo by Plautus, and the lovely Hesperus by Homer, there occurred so strange a prodigy, that it changed its color, size, form, course, which never happened before nor since. Adrastus of Cyzicus, and Dion of Naples, famous mathematicians, said that this occurred in the reign of Ogyges." So great an author as Varro would certainly not have called this a portent had it not seemed to be contrary to nature. For we say that all portents are contrary to nature; but they are not so. For how is that contrary to nature which happens by the will of God, since the will of so mighty a Creator is certainly the nature of each created thing? A portent, therefore, happens not contrary to nature, but contrary to what we know as nature. But who can number the multitude of portents recorded in profane histories? Let us then at present fix our attention on this one only which concerns the matter in hand. What is there so arranged by the Author of nature of heaven and earth as the exactly ordered course of the stars? What is there established by laws so sure and inflexible? And yet, when it pleased Him who with sovereignty and supreme power regulates all He has created, a star conspicuous among the rest by its size and splendor changed its color, size, form, and, most wonderful of all, the order and law of its course! Certainly that phenomenon disturbed the canons of the astronomers, if there were any then, by which they tabulate, as by unerring computation, the past and future movements of the stars, so as to take upon them to affirm that this which happened to the morning star (Venus) never happened before nor since. ... But possibly, though Varro is a heathen historian, and a very learned one, they may disbelieve that what I have cited from him truly occurred; or they may say the example is invalid, because the star did not for any length of time continue to follow its new course, but returned to its ordinary orbit.