Most asteroids look like stars in nearly every telescope because they’re too small and too far away to register as anything more than dots. Radio waves work better. Given a close pass, NASA’s 230-foot-wide Deep Space Network radio telescope at Goldstone, Calif. can synthesize an image of an Earth-approaching asteroid by bouncing radio waves off it and recording the “echo” of the returning waves. The pictures it provides are surprisingly detailed given how small most of these objects are.
The mile-wide 2007 PA8 flew only 5.6 million miles from Earth on Oct. 30 and got its portrait taken on Oct. 28, 29 and 30. Pictures show a rough-looking, elongated “boulder” with ridges and possible craters. JPL scientists chose to image asteroid due to a favorable combination of size and relative proximity to Earth at the point of closest approach.
The date also indicate that 2007 PA8 is rotating rather slowly, spinning just once approximately every 3-4 days. Good thing NASA made the most of this opportunity – this flyby was the closest Earth approach by this asteroid for at least the next 200 years.
Earth-approaching asteroid discoveries are fairly common nowadays thanks to the many surveys underway at observatories around the world. In the next week alone, four recently-discovered tiny asteroids – 2012 VB5, 2012 UV136, 2012 VQ6 and 2012 UY68 – ranging in size from 56 to 144 feet will zip by Earth between 432,000 and 1.6 million miles away. None poses any danger to the planet.
Like watching stars blow up? A recently discovered supernova in the southern galaxy NGC 1365 is now bright enough for amateur astronomers to spot in small to medium-sized telescopes. The galaxy, nicknamed the Great Barred Spiral Galaxy, is one of the most beautiful in the sky with sharply-etched spiral arms winding about its bar-like center. Droves of youthful stars populate the blue-tinted arms, while older stars illuminate the bar a warm yellow.
I only wish this gorgeous galaxy were higher in the sky from the northern U.S. As it is, it never climbs more than 7 degrees (less than one fist held at arm’s length) high in the southern sky. Skywatchers across the central and southern part of the country will find it both higher and easier to see.
The new supernova, dubbed SN2012 fr, was discovered by the automated La Silla TAROT telescope in Chile on Oct. 27, 2012 at 15th magnitude (dim!). It’s since rocketed to about 12th magnitude which puts into the range of a 6-inch telescope, especially for southern observers. It’s still brightening at this time so may become an easier target yet.
SN2012 fr is the end of the line for a planet-sized but superdense white dwarf star that put on too much weight from munching on a nearby companion star. The material collected on the dwarf’s surface, increasing the pressure on the star’s core and initiating runaway burning. Like an uncontrolled wildfire, the energy released as carbon and oxygen in the core were set aflame blew the star to bits. Astronomers call a white dwarf detonation a Type Ia supernova.
For more information and pictures of supernova 2012fr please check out Dave Bishop’s Latest Supernovae site.