International Year of Astronomy 2009 I often ponder what Galileo would make of our world today, four centuries on from the time when the Italian astronomer and natural philosopher commenced his observations of the heavens with an optical telescope. Leaving aside for the present modern cosmology and space exploration, I am sure the most striking impression would come from the state of our environment—a massive explosion in world populations, the consequences of the industrial and technological revolutions leading to global pollution on the grand scale. I am not deliberately setting out to paint a gloomy picture of the present and the immediate future (forget the next 400 years before we start, only a fantasist would look that far ahead!), but as someone whose eye has been keenly focused on world events I have to conclude mankind’s husbandry of the planet over the past 100 years or so has been woefully cavalier. The optical astronomer (and those in other fields, radio astronomy for example) has constantly to battle against the ever-growing intrusion into our environment of activities that not only mar observations but in some cases rule them out all together. Both light pollution and cloud seeding from aviation can mask the sky rendering it impossible to image faint objects at night and obliterating others (Sun, Mercury, Venus Mars) by day. When I commenced intensive observations from Orkney just twenty years back there was nothing like the traffic in aircraft (civilian and military) that we experience today. And so what can be said for this year, 2009? First I want to apologise to all those who were promised Galilean basic telescope kits, and who have found it impossible to get their hands on them. I can only say the preparation for this year has been lacking in some respects. At local level one witnesses ever-growing pressures on the rural environment to provide sources of energy resulting in large vessels being moored close offshore and lit to high heaven through the night hours. As the British Astronomical Association's Campaign for Dark Skies representative in Orkney, I feel like a Canute attempting to hold back an un-stoppable light surge! The Sun As to the astronomy itself, then the most significant naturally occurring event (or non-event, depending upon how you look at it) has been the Sun’s continuing low activity. In visual light the dearth in spots has provided little of interest to observe on the photosphere. There have been a few encouraging signs recently with some spot groups of modest dimensions hanging on for several days but for the most part smaller features have come and gone in a matter of hours.
The Planets Mercury Both Mercury and Venus offer a challenge during daylight hours when there is little of interest happening on the Sun itself. In the case of Mercury ground based observations are seriously limited so that the great majority of our understanding of the planet comes from space-mounted telescopes and space probes. But for the ordinary, earthbound watcher of the skies using modest telescopes, Mercury is a fascinating object since phase and brightness change rapidly with time. Mercury shows the greatest range in apparent brightness of all the planets of the Solar System when seen from Earth. Mercury’s apparent visual magnitude at its brightest is –2.3 close to some superior conjunctions, and around magnitude 6 when approaching inferior conjunction. At these extremes Mercury is only visible using optical aid when great caution has to be exercised so as not to have the Sun in the same field. Of course, close to inferior conjunction Mercury is a difficult object even with very large telescopes.
Venus Whereas Mercury makes several circuits of the Sun during the span of one Earth year of 365.25 days, Venus is more leisurely in orbiting the Sun. In 2009 Venus was conspicuous in our evening skies for the first three months, but then in early April left the scene only to appear much later (August) in the early morning sky where she has been, until recently, a conspicuous object for early risers. There was an interesting conjunction between Mercury and Saturn on October 8th at 06h 34m UT when the two planets were separated by a little over 18 arc-minutes (about 2/3 the apparent diameter of a full moon). Here in Orkney the days leading up to and following this event presented the usual frustrations with a great deal of cloud on blustery mornings. Also in the sky were Venus and Mars making a splendid ecliptic line-up of all the naked-eye planets omitting Jupiter. Here on Rousay we were able to image the conjunction in the early dawn sky and a little later after sunrise both planets were seen and imaged in the 180 mm Maksutov. Mars Mars is rapidly approaching opposition. At present the red planet is the brightest object (apart from the Moon and Sirius) in the eastern night sky. Close to the sickle of Leo, the constellation is also host to Saturn. See Dia 2 & Fig 4.
Jupiter & Neptune We featured both planets in sky notes early in 2009. Jupiter remains conspicuous in the early evening right up to the end of December. Jupiter is now in fast forward motion and was in conjunction with Neptune on December 20th. Those interested in “seeing” the Galilean satellites (this is the year in which we honour the great man, after all) without using a telescope or large binocular, may do so by imaging the planet with the telephoto setting on a digital camera. Mount the camera on a tripod if possible and use manual settings for exposure, since auto-settings tend to be unreliable. The resulting image can then be processed and enlarged on the computer to show the satellites close to Jupiter, whose image will be over exposed of course. Be patient and experiment with exposure times using the largest aperture available. An example of this practice is given using the Queen of lenses (Nikkor 200 mm f/2) with an exposure of 1 second (Fig 3). This interesting image was taken with a static camera and shows stars to magnitude 11. (Magnified the images are seen to “trail”.) It not only includes the satellites (L to R) Callisto, Ganymede and Europa, but Neptune also is clearly visible.
Using a little imagination, the asteroid Psyche (mag. 11.2, and a particular favourite of mine) is in the field a little to the right of mu Capricorni (mag. 5.08) top left. Uranus is in the constellation Aquarius below the Square of Pegasus, about 30 arc-degrees east of Jupiter and Neptune. Noctilucent Clouds The most striking aspect to 2009 from the perspective of the Northern Isles was the quality of our summer weather. It proved to be one of the warmest and driest on record, in sharp contrast to the remainder of the British Isles. Days in June and July would be clear (apart from the condensation trails of course!) one after the other with a complete absence of haar—most unusual. The noctilucent clouds were observed from southern latitudes some days before they became a feature in our northern skies. From Orkney the finest displays took place on July 23rd and 25th.
Another consequence of the fine summer was that late August skies at night were clear, just as all-night twilight started to fade. As a result we were able to image the Milky Way close to the meridian. Normally we have to wait for early autumn to see the Milky Way at its best. The image (Fig 6) shows the effects of light scatter from Kirkwall and Rousay in the region of the pier.
Finally for 2009 On a wider front there have been a number of advances in astronomical endeavour, not least the newly functional Herschel Infrared telescope. The results have already started to challenge our understanding of the physical “world”, and as more information accrues we may predict with certainty that our ingenuity will be taxed to the full. I suggest “ingenuity” is the important word here especially in the field of theoretical astronomy in which cosmology is a major player. In science we seek to verify our hypotheses built from painstaking observation and experiment. Some areas of science have taken a bit of a bashing this year where the fate of planet Earth has been in much debate. In my own work I have always stressed the importance of an all-round approach to understanding. When I was a young physicist revelling in the use of mathematics I too thought in terms of definitive answers to the deeper questions thrown up in astrophysics and cosmology. Today, as I teeter into old age, I am more cautious.
In the all and everything there is no all and everything: there is no beginning there is no end, there is only what is happening. I would draw attention to the final images of the Orion Nebula M42, and the Andromeda Galaxy M31, in the sequence of images and to have these few lines in mind:
Good wishes to all our attentive, Sky Notes readers. JV 21/12/09 |
 |
