Saturday, May 25, 2013
By BERNIE REIM
February is named after februa, which are rites of purification. We will be halfway through winter on the second of the month – Groundhog Day.
Sky Guide: This chart represents the sky as it appears over Maine during February. The stars are shown as they appear at 9:30 p.m. early in the month, at 8:30 p.m. at midmonth and at 7:30 p.m. at month’s end. Jupiter is shown in its midmonth position.
Prepared by George Ayers
Like most months, this month will have its share of good conjunctions. But something much more unusual also will happen.
On the 15th, a little asteroid will make big news. At least it won't make a big impact or a big splash.
Named 2012DA14, this asteroid is about 150 feet across and the size of a gymnasium. It will pass within just 18,000 miles of our surface, which is 13 times closer than the average Earth-moon distance. At our escape velocity, that is only one hour away. At our orbiting speed of 67,000 miles per hour, that is only about 15 minutes away. That means that if that asteroid were to get here just 15 minutes earlier, it would actually crash into the earth.
As it is, this marks the closest approach of a natural object ever predicted far in advance. It will zip across our sky from the South Pole to the North Pole in just 12 hours that night, but it will be too faint to see without a telescope, and even then will be very hard to find because it's moving so fast.
If this little asteroid hit us, it would only release about 3 megatons of energy, or about a quarter of the energy that the comet or asteroid that exploded in the air just above Tunguska, Siberia, on June 30, 1908. That would be nearly harmless unless you were within a close radius. It would probably not even create much of a tidal wave.
That reminds me of a potentially much more dangerous asteroid that came close to us on Nov. 8, 2011. That one was named 2005YU55 and was about 10 times larger, but also passed us at about 10 times farther away than the little one on the 15th.
That one was also moving very fast, about 30,000 miles per hour, but we did manage to find and photograph it through one of our big telescopes at the Starfield Observatory in Kennebunk after several hours of effort.
The size of an aircraft carrier, this nearly round primordial rock was spinning lazily and effortlessly once every 20 hours. By comparison, the huge planet Jupiter, which is 10 times the diameter of Earth, spins around madly once every 10 hours.
It was very eerie to think carefully about what we were really watching that night for several hours. This dark and dangerous chunk of ancient rock had great potential power to harm us, yet it was totally harmless as it drifted along unfettered through space. Scientists got some great pictures by bouncing radio echoes of it with the Gladstone and Arecibo radio telescopes. If it had hit us, it would have caused some real damage by releasing 4,000 megatons of energy and creating a 70-foot tidal wave if it hit the ocean.
There are two comets that might become fairly bright this year. Comet PanSTARRS, discovered in June 2011 by the PanSTARRS sky survey project in Hawaii, could get as bright as second magnitude by the middle of next month. It is already visible in the southern hemisphere.
Then there is Comet ISON discovered in Russia in September of last year. It's still out past Jupiter and visible only in good telescopes now at 15th magnitude in Gemini. It could brighten to 11th magnitude by the middle of August and reach seventh magnitude, which would bring it within reach of binoculars by late October.
Then it should become visible without binoculars by early November and even sport a 10 degree-long tail just before it plunges in toward the sun on Nov. 28. This will be a sun grazer, getting within the radius of the sun. Many comets burn up when they get that close, like Comet Elenin last year, but others survive the perilous journey and emerge on the other side, like Comet Lovejoy. Comet ISON will probably survive. Just before dawn by the middle of December, this comet could become nearly as bright as the full moon and have a tail spanning over 45 degrees of the sky!
Since it has a very similar orbit to the great Comet of 1680, Comet ISON actually may have been a part of that comet, which was even visible in the daytime.
M&M SEEM NEAR
Mercury and Mars can be seen close together low in the western evening sky 45 minutes after sunset during the first half of this month. Watch as a slender waxing crescent moon passes just above the pair on Monday night, the 11th.
When you look at the faint orange dot that is Mars, remember that we have had a giant remote-controlled robot up there for three months. The Curiosity Rover has traveled about a quarter of a mile and performed flawlessly so far. It has just discovered more evidence of water in some veined rocks below the surface. This water once flowed and percolated through this fractured terrain. Curiosity is now preparing for its biggest challenge, drilling into one of those rocks and analyzing its powder, which never has been done.
Jupiter still rules the night, high and bright in Taurus as soon as it gets dark. The king of the planets just ended its retrograde or westward motion, and is heading back eastward toward Gemini for the next eight months. The moon will again pass just below Jupiter around midnight on Sunday the 17th. You can see the four largest of its 62 moons through a good pair of binoculars. We even saw what looked like a fifth moon the other night, but it was slightly orange and slightly out of line with the four Galilean moons. The fifth one was just a star in Taurus.
Saturn rises around midnight in the constellation of Libra. Look for a last quarter moon just below the ringed planet one hour before sunrise on Sunday morning the third.
Venus can still be seen very low in the eastern morning sky just before sunrise for the early part of this month.
• Feb. 3: Apollo 14 landed on the moon on this day in 1971. Alan Shepard and Edgar Mitchell were the two astronauts that walked on the lunar surface for that mission. Edgar Mitchell had many great insights on that trip, as did all the astronauts. He said, "We left the earth as technicians, we returned as humanitarians." Last quarter moon is at 8:56 a.m. EST.
• Feb. 4: Clyde Tombaugh was born on this day in 1906. He discovered Pluto on Feb. 18 when he was just 24 years old.
• Feb. 7: On this day in 1984, Bruce McCandless made the first untethered spacewalk.
• Feb. 8: Jules Verne was born on this day in 1828.
• Feb. 10: The new moon is at 2:20 a.m.
• Feb. 11: On this day in 1970, Japan became the fourth country in the world to launch its own satellite.
• Feb. 15: On this day in 1564, Galileo Galilei was born.
• Feb. 16: On this day in 1948, Gerard Kuiper discovered Miranda, a moon of Uranus that is about the size of Texas. Sporting a giant chevron, Miranda looks like a patchwork quilt of features from many different moons.
• Feb. 17: First quarter moon is at 3:31 p.m.
• Feb: 19. Nicholas Copernicus was born on this day in 1473. He first theorized that we actually live in a heliocentric solar system and not a geocentric one. The Russian MIR space station was launched on this day in 1986. It survived for 15 years until March 2001.
• Feb. 23: On this day in 1987, Supernova 1987a exploded in the Large Magellanic Cloud.
• Feb. 25: Full moon is at 3:26 p.m. This is also known as the Snow, Hunger or Wolf Moon.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.