Friday, December 6, 2013
By BERNIE REIM
This will be a good month to continue to develop a larger cosmic perspective of our home planet. As we become more aware of our place in space and how small the earth really is in the context of our sun and just our own family of planets, we will work more effectively together to preserve and increase our quality of life unto distant future generations instead of just continuing to degrade it as we have been doing in the past.
This chart represents the sky as it appears over Maine during August. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month’s end. Saturn is shown in its midmonth position.
Sky chart prepared by George Ayers
On July 19, a very rare event took place that will definitely help us to attain and sustain this much-needed new perspective, if we really stop and think about what this image reveals about our individual and collective lives.
A robotic camera on the Cassini spacecraft took a picture of Saturn and Earth backlit by the sun. Scientifically this image will tell us a lot of interesting things about the dynamic and ever-changing nature of Saturn's extremely thin and dynamic ring system, and its interactions with some of Saturn's moons, but philosophically this image is much more important.
Similar images like this one were only taken twice before in the whole million-year history of humans on Earth.
The first one was on June 6, 1990 by the Voyager 1 mission from nearly 4 billion miles away, which remains the farthest image ever taken of Earth. Only about 5 billion people were living on Earth then, and now we have more than 7 billion. From that distance the whole earth was reduced to one pixel on that iconic Voyager image, which inspired Carl Sagan's book, "Pale Blue Dot."
I will quote a few words from his book to help us get a better sense of the real meaning of this image and why it was so important to recently take a similar image to remind us of what we should have learned and put into practice 23 years ago: "Every saint and sinner in the history of our species lived there on a mote of dust, suspended in a sunbeam. The earth is a very small stage in a vast cosmic arena. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity -- in all this vastness -- there is no hint that help will come from elsewhere to save us from ourselves. It is up to us. It's been said that astronomy is a humbling, and I might add, character-building experience. To my mind there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we've ever known."
The second such image was taken Sept. 15, 2006 with the robotic camera on the Cassini mission, from about 1 billion miles away, similar to the one just taken. It also showed the earth as just one pixel, but this time a very dramatic, glowing Saturn in all of its glory, brilliantly backlit by the sun, with its dynamic rings nearly dancing off the image, dominated the scene.
The current image is similar to the last one, but it will give us more scientific knowledge and we knew ahead exactly when it would be taken, which allowed people on earth to participate. It was taken in the late afternoon when Saturn had not yet risen for us in the east. I knew that our part of the country and part of the Atlantic Ocean would be in the sunlight from the view of this robotic camera when the image was taken. From that great distance there is no sign of any human life on Earth. It is very humbling, but also inspiring at the same time because it starts to show us how much more there is beyond the Earth and how we are related to the other planets in our solar system and the nearly 1,000 planets we have already discovered in other solar systems in just the past 18 years.
It is fitting that Saturn is now the only bright evening planet after Venus sets in the west just one and a half hours after sunset. Notice that Venus will appear to be rapidly catching up with Saturn in our evening sky this month. They will start 53 degrees apart and end up just 18 degrees apart, or less than two fists at arm's length, by the end of this month.
To add to the drama, a slender waxing crescent moon will show up just below Venus on Aug. 9 about half an hour after sunset, low in the west-southwestern sky. Then keep watching as the moon drifts close to Spica by the 11th and near Saturn on the 12th, when the Perseid meteor shower will peak.
This will be a good year for this famous meteor shower caused by the earth passing through debris from Comet Swift-Tuttle, zipping into our upper atmosphere at nearly 40 miles per second. This is basically comet dust, about the size of a grain of sand. The moon will have set a few hours before midnight, so it will not interfere with the best part of the shower, which is usually between midnight and dawn. You could see up to 100 meteors per hour this year from a dark sky site. Look northeast towards Perseus to see where these meteors will come from, but you could see them anywhere in the sky, although you will always be able to trace them back to their radiant in Perseus. Be aware that you may also see some late Delta Aquarids and Kappa Cygnids, along with some stray meteors that are not part of any of these showers. The best mornings this year will be Monday the 12th and Tuesday the 13th.
Look for Mercury, Mars and Jupiter in the eastern morning sky 45 minutes before sunrise for the first half of this month. Then keep watching as Mercury drops out of the picture, and Mars and Jupiter get a little higher and brighter in our sky.
• Aug. 3. A waning crescent moon will be near Jupiter this morning. The Messenger spacecraft was launched to Mercury on this day in 2004.
• Aug. 4. The moon will be near Mars this morning.
• Aug. 5. The moon will be below Mercury in Gemini this morning, 45 minutes before sunrise.
• Aug. 6. New moon at 5:51 p.m.
• Aug, 9. The waxing crescent moon will be near Venus this evening half an hour after sunset low in the west-southwestern sky.
• Aug. 10. On this day in 1990, the Magellan spacecraft entered orbit around Venus.
• Aug. 11. On this day in 1877, Asaph Hall discovered Deimos, the smaller of the two moons of Mars at about eight miles in diameter. He would discover Phobos, at about 14 miles in diameter, just 6 days later. They are thought to be captured asteroids and they are just temporary moons since they will crash into the red planet in a few million years.
• Aug. 12. The Perseid meteor shower peaks this morning and the next.
• Aug. 14. First quarter moon is at 6:56 a.m.
• Aug. 20. Full moon is at 9:45 p.m. This is also known as the Sturgeon, Green Corn or Grain Moon.
• Aug. 22. On this day in 1963, the X-15 set a world altitude record of 354,000 feet, or 67 miles high. That is about the altitude where the northern lights take place and most of the meteors burn up as our upper atmosphere starts to get a little denser at that height.
• Aug. 24. On this day in 1989, Voyager 2 flew past Neptune. I remember that they had live commentary from scientists at JPL during a program called "Neptune All Night."
• Aug. 28. On this day in 1789, William Herschel discovered Enceladus, which is the sixth-largest of Saturn's 62 moons. Since then it was discovered that this moon has cryovolcanoes that shoot large jets of water ice into space, some of which falls back as snow and some of which adds to and interacts with the rings of Saturn. Last-quarter moon is at 5:35 a.m.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.