by Kim Malville
Venus is low in the evening sky, setting about 1½ hours after sunset. The planet starts the month at the western side of Virgo, moving rapidly toward Spice throughout the month. At the beginning of August Saturn becomes visible about 45 minutes after sunset some 30° above the southwestern horizon, at the eastern edge of Virgo. Jupiter and Mars rises about 3:30am at the start of the month. Mars appears 20 minutes later. Both become higher in the eastern sky as the month progresses. Both are in Gemini at the beginning of August. Jupiter stays in Gemini, but Mars races eastward, reaching Cancer at the end of the month.
August 6: New moon
August 9: Thin crescent moon is visible below Venus above the western sky about 30 minutes after sunset.
August 11-13: The Perseid meteor showers return in full glory.
August 12: Look for Saturn above the moon.
August 20: Full moon
Great nights for watching the Perseids (August 12-13)
This year is an outstanding opportunity for watching these meteors since the waxing moon will set in mid-evening. The best time for observing these meteors is from 11 onward to the first light of dawn. The radiant out of which the meteors pour lies near the head of Perseus, which appears above the horizon around 11pm in the northeastern sky. The earth passes through the thickest part of the meteor stream around 1pm local time of August 12. For us in Crestone, the shower splits itself between the early morning hours of August 12 and 13. Last year at the peak of the Perseid shower people were counting up to 100 meteors per hour. We may see fewer than that in North America but surprises can happen if the earth encounters dense blobs. In any case you can expect to see a meteor every minute. These meteors are produced by tiny bits of debris from Comet Swift-Tuttle, moving at 37 miles per second.
Drama, death, and uncertainty in the center of our galaxy
It is fair to say that many astronomers are agog over a gas cloud that is having a close encounter with the huge black hole at the center of the Milky Way. In December 2011, the orbit of the gas cloud in Sagittarius, called G2, was first determined to come perilously close to the Milky Way’s central black hole by mid-2013. Nineteen months ago, the immense gravity of the black hole, which is 4.3 million times the mass of the sun, was already squeezing and stretching the gas cloud as if it were pasta dough or taffy.
Images obtained in April with the Very Large Telescope in Chile show that the leading edge of G2 has already whipped around the black hole’s far side and is actually moving toward us, like a train rounding a corner. The end of the gas cloud is still moving away from us at speeds up to 3,000 kilometers per second, 100 times the speed at which Earth orbits the sun, or one percent the speed of light. Since its discovery the gas cloud has been stretched to twice its initial length. This kind of stretching is what humans would experience when falling into a black hole. Because the front and rear end of the gas cloud have grown so far apart, it appears that most of the cloud won’t make its closest approach to the black hole until early next year. Never before in human history have we been able to view the play-by-play destruction of an object when captured by a black hole.
There are complications. Light waves get stretched in the strong gravity of the black hole. The cloud may fade from view in coming months as its light gets stretched into the infra-red. Its remnants might gradually get funneled into the black hole culminating in a rare bright display as they approach the point of no return. The large telescopes of the world will be waiting. Stay tuned.
Signals from beyond the galaxy
For the first time a series of extremely powerful ultra-short radio bursts have been detected that apparently originate from outside the Milky Way Galaxy. Lasting for only a few thousandths of a second, these mysterious bursts appear to be a previously unknown class of radio-emitting phenomenon. These are being described as one of the most important radio discoveries in the last couple of decades.
Although radio signals that vary over days to months have been recorded from distant galaxies, such short signals from beyond the Milky Way have never been previously detected.
Using data from the 210 foot diameter Parkes Radio Telescope in Australia, astronomers have found four such bursts. All seem to have come from outside the galaxy, from distances of between 6 to 10 billion light years.
The brevity and brightness of the bursts suggests they were emitted by an extraordinary object known as a magnetar, which is a neutron star with an extremely powerful magnetic field. Neutron stars are the remnants of supernova explosions, in which a large star destroys itself, but leaves a dense core. As that core collapses its magnetic field is enormously enhanced. Solar flares, the most powerful explosions sunspots. These magnetars have magnetic fields that are a million-billion times stronger than those of sunspots.
Each of these four bursts has come from a different region of the universe, suggesting they are such cataclysmic events that they must have destroyed the objects that produced them. It seems unlikely that they are signals coming from distant extraterrestrial intelligent life. The energy involved is equal to the total output of the sun during for 300,000 years compressed into a period of milliseconds. Life could not survive such intense radiation. But, who knows?