Astronomy  Part 3

We’ve already discussed the immense distances even to the nearest star, and the extent of the night sky across the Heavens.  If someone flies across the Atlantic and back weekly throughout a working lifetime, or drives 80 miles (128 Km) daily again for a working lifetime, in each case the total distance travelled is still 1 million times less than our Earth to nearest star distance!

Our own star the Sun is much closer, but still requires approximately 3720 Earth circumnavigations, or 11,733 Earth diameters to traverse. Our own Moon is 10 Earth circumnavigations away or about 31 Earth diameters away.

Given the extent even of our local star group, let alone other parts of our own galaxy, it is no wonder that we haven’t found any evidence of intelligent life elsewhere in the Universe. It is extremely likely to exist, but at distances beyond comprehension. The chance of them finding us or us finding them is practically nil. It is comforting to think we almost certainly aren’t alone in the Universe. It is also very comforting as they might not resemble us at all, and some could well have benign intentions against us!

If there is intelligent life within 5,000 light years of us, it would take 5,000 years for any intelligible signal to be sent or to reach us, and another 5,000 years to reply! Obviously, even if such intelligent life is eventually found, physically meeting them will be completely out of the question! As for approaching speed of light travel, even if a suitable means to accelerate is found, there is the problem of possible interstellar black holes, or possible gas giant planets existing in space, perhaps where the mass has been insufficient to form a star. These could only be detected by radar and by the time the signal is sent and returned, and interpreted, there could be very large G forces involved in slowing down and/ or changing course to avoid them! This limits the speed humans could travel to well well below sub-light speeds. There is also the possible problem of smaller meteoroid size particles that would pierce a spacecraft or the people on board, and the problem with any prolonged exposure to cosmic rays.

One theory in Astronomy, the Big Bang theory of Creation is just that, a theory, though there is some evidence that could be interpreted in this way. We simply don’t know. There is no known law of Physics to explain more distant galaxies supposedly accelerating away from us at increasing rates. If the assumed/estimated figure for intergalactic dust is wrong, then this alone could explain the observed increasing red shift. We also don’t know what effect there is on light over immensely vast distances and billions of light years, whether the photons could lose energy (eg by lengthy exposure to high energy cosmic rays) and hence appear redder over these distances and this length of time span. Red light has less energy than blue light, but assumptions have been made without any means of proof that this is due to speed and acceleration, and not due to other factors, which may actually be more likely!

Basically, any astronomy theory comes down to our interpreting what is observed. We can’t send light out into intergalactic space and observe what happens to it over billions of years!!!!

Looking at the night sky is slightly easier than the 129,600 directions to point a telescope would suggest. Many directions with an amateur telescope have little of interest except very feint stars or empty sky. There are maybe 500 - 600 deep sky objects worth investigating plus binary or multiple star systems, some variable stars, the planets and the occasional comet that can reasonably be seen by amateur astronomers with average equipment.

There’s about 1 in a hundred chance of happening on any of these objects by pointing the telescope at random at the night sky. So a night sky atlas, maps of constellations and a red torch are very necessary to find anything worthwhile, apart from the few easily visible objects such as the Pleiades, the Orion Nebula or the brighter planets. Or, of course, you have an auto-pointing telescope such as GOTO or AutoStar mount (with fresh batteries!!). You might also want a compass if you are at a location when the North Star isn’t visible, and you’re not sure of your bearings!

Incidentally, it is possible on rare occasions for Mars to outshine Jupiter. All the planets vary in brightness depending on their distance from us and their orientation respective to the Sun. All except Venus have orbits that markedly differ from circular and hence their distance from us and the Sun varies sometimes quite considerably. As their orbital period is different from our own, their motion about the night sky, and their time to move from constellation to constellation along the Ecliptic is variable, from days to years even. Because of the combined effect of their orbits with our own orbit they also show retrograde motion for some of the time. They are sometimes visible in the evening sky then for other parts of the year in the early morning sky, and sometimes aren’t visible while close to the Sun or behind the Sun. There are charts available to show when and where you can see the planets. Saturn is rapidly approaching having it’s rings edge-on or nearly edge-on to us which will occur through late 2008 and 2009. Mars is some way from nearest approach to us which will again occur in 2018. The Moon is of course visible for most of each month though there are about 5 days each month when it isn’t lit by the Sun. It can also be quite a challenge to find it when it is a very slim crescent for several days each side of this. For viewing with binoculars or a telescope, the best views are when the Moon is crescent in aspect, each side of the New Moon or gibbous, each side of the Full Moon, as craters on the partly lit edge show shadow and relief aspects, from the Sun’s low angle to this part of the Moon’s surface. It is also more comfortable to view the Moon as a crescent in a telescope as it is much less bright than at Full Moon. A simple guide is that saucer way up is a new moon!

Objects that are fairly near brighter stars in major constellations should be fairly easy to locate. Those that are among fainter stars in minor constellations can be much trickier to find, and those away from constellations are much more difficult, unless you can use setting circles on Equatorial mounts, and read a known star or have the local Sidereal time available. Binoculars can certainly assist in finding some of the brighter objects of interest.

The quoted magnitude of Galaxies and Nebula can be deceptive, as their surface brightness might be quite dim, if spread over a larger area, making finding some of them quite a challenge, even in dark skies.

But unless you are living in areas with substantial numbers of clear nights, the weather can be the biggest factor affecting ability to view the Heavens.  In a bad month in our part of the UK, there can be up to 28 nights or more with a large amount or total cloud cover. Of remaining nights with some or plenty of clear sky, many will be affected by higher cloud layers, mist, fog or unsteady seeing conditions. In the Winter it can get very cold, with even wearing thick coats, hats, scarves and gloves making more than 20 minutes of viewing very uncomfortable.

Fortunately, there are astronomy planetarium programs that run on PCs or laptops (notebook computers) for home research in comfort and to help learning the night sky.

Stellarium is excellent, and free.

Starry Night Pro 6.2 is a bought program that is also excellent and has further setting options!

The Universe is cohesive, in the sense that even at the most vast distances viewable, light and gravity operate similarly to us here on Earth, and the elements are the same, even across the Universe. We know this from spectroscopic analysis of light from distant reaches. The laws of physics are the same here as in distant reaches of the Universe! As will be explained in part four, this doesn't mean we know nearly everything about various phenomena in some distant and not so distant parts of the Cosmos! Sometimes we know very little!