The sky's two brightest planets stand poised to pass each other in evening twilight. A slim crescent Moon will join the pair December 1. Keep your eyes on the early evening sky for the next week, and you will witness the most dramatic planetary alignment of 2008. The southwestern sky provides the stage as Venus and Jupiter - the two brightest points of light in the sky - begin their celestial dance. The two appear closest November 30, but it's worth watching for several days on either side as they make a beeline for each other and then back off.
Throughout this period, Venus appears 7 times brighter than Jupiter. Even so, Jupiter easily outshines every other starlike object in the sky. To add to the drama, a slender crescent Moon passes the planet pair after sunset December 1. "Although all three objects shine bright enough to see just 30 minutes after sunset, the scene grows more spectacular as twilight deepens," says Astronomy magazine Senior Editor Richard Talcott. The trio doesn't set until 3 hours after the Sun.
The gap between the two planets has been closing all month. In early November, Jupiter appeared some 30° to Venus' upper left. By November 30, the separation drops to just 2° - four times the Moon's apparent diameter. That same evening, a waxing crescent Moon lies 8° to Venus' lower right. One night later, the Moon hangs just 2.5° to Venus' upper left. The Moon then appears 15 percent lit, although the "dark" side should glow faintly from earthshine - sunlight that reflects off Earth, reaches the Moon, and then bounces back to us.
Such close encounters between Venus and Jupiter happen fairly often. Frequently, however, these conjunctions occur close enough to the Sun that the planets appear in a bright sky. The two last met in February's predawn sky, although their altitude then was less than half of what it is now. Viewers will have to wait until March 2012 for Venus and Jupiter to have another nice evening conjunction.
Picture of the moon taken by the Moon Impact Probe
What was extraordinary about the historic event of Chandrayaan-1’s probe landing on the moon on Friday night was that the spacecraft was built in India, it was put into orbit by the Indian rocket, PSLV-C11, and the launch took place from Indian soil, said a jubilant M. Annadurai, Project Director, Chandrayaan-1. Mr. Annadurai led the team that integrated the 11 scientific instruments, including the Moon Impact Probe (MIP) into the Chandrayaan-1 bus at the ISRO Satelllite Centre, Bangalore. The MIP was built by the Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram. “We have got all the data. We are working on the data and processing them,” Mr. Annadurai said.
S. Ramakrishnan, Director (Projects), VSSC, called it “a momentous occasion for ISRO and India because it is for the first time that we have sent a spacecraft to an extra-terrestrial body and its MIP with the logo of the Indian flag has reached the moon soil.”
Everything went as per schedule right from the separation of the MIP at 8.06.54 p.m. IST from Chandrayaan-1 to the MIP impacting on the Shackleton crater 25 minutes later, Mr. Annadurai said. The entire sequence of events began at 7.15 p.m. at the Spacecraft Control Centre (SCC), which was the nerve-centre of the operations, at the ISRO Telemetry, Tracking and Command Network (ISTRAC), Bangalore, headed by its Director S.K. Shivakumar.
The spacecraft got oriented in the right attitude before the command went from the SCC for the MIP to separate. The MIP separated as per plan and “we got the positive signal that it had separated,” Mr. Annadurai said. Then the data link from the cable to the radio frequency got changed as per plan. “For 25 minutes of its descent towards the lunar soil, we received continuous radio frequency signal from the MIP,” he added. About 300 seconds after the separation of the MIP, the SCC received signals of a reduction in the velocity of the descent of the MIP indicating that the retro-rocket had fired.
Twenty-five minutes after the separation began, “the receiver went on unlock, indicating that the MIP had impacted on the Shackleton crater on the moon,” said Mr. Annadurai. “The trajectory of the MIP was excellent,” he said.
As the MIP crashed on the lunar surface, it self-destructed.
Earlier, data from the video-camera of the MIP, its radar altimeter and mass spectrometer kept pouring in simultaneously throughout the 25 minutes of the MIP’s descent. The video-camera had taken a number of pictures of the moon’s surface.
As this sequence was being enacted, Chandrayaan-1, the mother-spacecraft, had gone behind the moon.
“We have had a good success and everything went as per our aim. What is important is that the former President, A.P.J. Abdul Kalam (a rocket technologist himself) was present at the SCC during the occasion,” said Mr. Annadurai.
Mr. Ramakrishnan called it “a precision mission” in which the MIP was in communication with the mother-spacecraft during all the 25 minutes. The MIP separation was indicated by a disturbance in the Chandrayaan-1. Its gyros and sensors sensed the separation. “We could see the spin-up and de-orbit motors work [on the plot-board],” he said.
“Everything went precisely in this mission. Right from the PSLV-C11 launch on October 22, the Chandrayaan-1 being safely inserted into the lunar orbit on November 8, the MIP separating from Chandrayaan-1 and its impacting on the moon, everything performed with clock-work precision,” Mr. Ramakrishnan said.
High overhead around the 8 p.m. local standard time is a bright configuration of stars that people unfamiliar with the sky often mistake for the Big Dipper. Big it is, but – at least in an official sense – a dipper it is not.
This large figure is not usually described as a dipper in most stargazing guides; you shouldn't expect to find any recognized authority for this Autumn Dipper. Truth be told, when starry dippers are mentioned, most people immediately think of the Big Dipper and the Little Dipper in the northern sky, and perhaps even the inverted Milk Dipper in Sagittarius.
The Autumn Dipper, in fact, looks like a much larger and brighter version of the Little Dipper.
The "bowl" is composed of the Great Square of Pegasus, the Flying Horse. The Great Square is one of the unmistakable landmarks of the night sky. The Square is not a constellation in itself but belongs partially to Pegasus and partially to Andromeda, the Princess, and helps find both. It is not a perfect square, appearing slightly battered out of true square shape.
Pegasus actually supplies only three stars of the Great Square: Markab, Scheat and Algenib. The fourth is Alpheratz, the brightest star of Andromeda.
The "handle" of our Autumn Dipper is composed of stars belonging to the constellations Andromeda and Perseus. Alpheratz, Mirach and Almach are almost evenly spaced toward the northeast and are the brightest stars in Andromeda. The next bright star, located along the same line, Marfak (sometimes spelled Mirfak), is the brightest star of Perseus. Two of these four stars (Alpheratz and Markab) are valuable navigational stars and the nose of the mythical horse contains yet another in Enif.
Pegasus is, of course, the famed winged horse of Greek mythology. He's been found on ancient tablets from the Euphrates Valley, and on Greek coins that were minted during the fourth century B.C. In legend, he was born from the blood of the gorgon Medusa when that monster was slain by Perseus. When Pegasus was brought to Mount Helicon, one kick of his hoof caused the spring of Hippocrene to flow – a source of inspiration for poets. In another tradition he carried the thunder and lightning for Zeus.
The old star atlases that used allegorical drawings depicted Pegasus turned over on his back with his body outlined by the Square. Some years ago I was giving a lecture under the dome of the Space Theater at New York's Hayden Planetarium when, using my electric pointer I tried tracing out Pegasus. "So that's Pegasus . . ." I started to say, when suddenly, from out of the darkness I was interrupted by a voice that spontaneously exclaimed: "I see it!"
I then finished my sentence: ". . . but for people today to honestly claim that they can actually visualize the upside-down front half of a flying horse is a masterpiece of imagination!"