Astrology Quarterly - Astronomy - Heavens Above

A S Morton

Heavens Above - July 2007

Our ‘magic roundabout’, planet Earth, arrives at aphelion (furthest distance in its orbit from the Sun) on the 7th July at a distance of 152 million km. Perihelion (closest to the Sun) occurred at the beginning of the year on January 3rd at a distance of 147 million km. Which if you stop and think about it is rather odd. We’re well into our northern hemisphere summer, the temperatures are generally moving upwards towards their highest, and yet the source of that heat, the Sun, is currently at its furthest away from us all year. And isn’t January in the middle of our northern hemisphere winter when we were actually closest to the Sun? How can this be? Although it’s a little puzzling to fathom out this apparently strange quirk of nature the answer relates to the tilt of the Earth’s rotational axis and, of course, that old favourite the ‘angle of obliquity’.

Earth’s rotational polar axis is not perpendicular and at right angles to the Earth/Sun plane (the ecliptic), it’s tilted over by about 23.5°, which gives us our earthly seasons, so there is a part of the year when the northern hemisphere is tilted towards the Sun and a part of the year when the southern hemisphere is tilted towards the Sun. And because the orbit of the Earth around the Sun is not a perfect circle (despite all attempts by those Aristotelian disciples who came before us to maintain the concept of that particular ‘perfection’, although more precisely they maintained that the orbit of the Sun around the Earth was a perfect circle), the summers and winters of the northern and southern hemispheres are not exactly equal and opposite, there is very small difference between the two. The difference, however, between Earth’s perihelion and aphelion is less than 3% and the effect of this on temperature change between both hemispheres is almost negligible. Variation in temperature has more to do with the angle at which the Sun’s rays arrive at various parts of Earth and the amount of the Earth’s atmosphere they have to pass through before reaching the surface of the planet along with the time needed to establish equilibrium through the heat losses and gains between land masses and the oceans.

The seasons would be regular and the temperatures and the climate would be stable if everything remained constant in Earth’s orbital cycle around the Sun. However nothing in our universe remains forever the same as such as Galileo Galilei were persecuted for trying to point out some four centuries ago. Everything is in state of flux and our planet, Earth, is certainly no exception to this with many aspects of our orbit evolving and changing through a variety of cycles over long and differing periods of time.

The ‘tropical year’ is the length of our year from Spring Equinox to Spring Equinox (or Solstice to Solstice), a complete cycle of seasons, and is the basis of our calendar. The ‘precession of the equinoxes’, the wobble of the Earth’s rotational axis, causes the equinoctial points to shift backwards through the zodiac over a period of approximately 25 - 26,000 years to complete a full cycle. Often referred to as the ‘Great Year’ and related by some to the ‘Astrological Ages’ it is in fact only one of many ‘great years’ and is more properly termed the ‘Platonic year’. The length of the year from Earth’s perihelion to perihelion is called the ‘anomalistic year’ and is, on average, 25 minutes longer than the ‘tropical year’. This causes the date of perihelion, relative to the ‘tropical year’, to regress (move later in the calendar) by about a day every 58 years and to complete one cycle through the ‘tropical year’ in about 21,000 years. Although this causes the date of perihelion, when the Earth is at its closest to the Sun, to slowly move through the seasons it does not of itself cause seasonal variations.

However, there are further long term cycles simultaneously unfolding. Our Earth’s orbit itself is not quite a circle but an ellipse (as determined by one Johannes Kepler and his laws of planetary motion) and the eccentricity of the orbit (how elliptical it is) varies over time between being almost exactly a circle to being anything up to three times more elliptical than it currently is today. This ‘cycle of eccentricity’ moves through all these variations of eccentricity in roughly a 100,000 year period. Coupled with the 21,000 year ‘perihelion cycle’ this might cause some dramatic changes in our climate to occur during extended periods of extreme eccentricity.

Additionally, there is another important long term cycle which potentially can contribute to some far-reaching effects on our climate being the 41, 000 year cycle in the change of the ‘angle of obliquity’. Currently around 23.5°, which is roughly in the middle area of its range, it can vary by up to a few degrees either side of this figure during this ‘obliquity cycle’. This particular cycle has a direct effect on seasonal extremes as it is the ‘angle of obliquity’ itself which gives rise to our seasons in the first instance. Any significant change to the ‘angle of obliquity’ will therefore have a direct effect on the severity or otherwise of both northern and southern hemisphere seasons and seasonal variations. If we were upright relative to our orbit around the Sun there would be no seasons (and no western ‘tropical’ astrology either).

Collectively these cycles are referred to as the ‘Milankovitch cycles’ after the Serbian scientist Milutin Milankovitch who carried out extensive research and produced detailed theories on the potential effect of these cycles on climate change in the 1920’s, particularly related to our planet’s cycles of ice ages, which in the current ecologically more aware era that we seem to be entering into have once more become a reference point for discussion and debate around our current perceptions of climate change on planet Earth and what, if indeed anything, man’s contribution to that accelerating process might be.

If perihelion is when we are closest to the Sun and aphelion is when we are at our furthest then the basic unit of astronomical measurement (1AU = 1 astronomical unit), which is used to measure distances between objects in space, within our own solar system particularly, is determined as being the average distance of the Earth from the Sun in its orbit around the Sun. The currently accepted equivalent distance approximates to 150,000 km. Unfortunately, because the average distance from the Earth to the Sun during the course of one cycle to the next is subject to small variations (as detailed above) the definition and measurement have been modified for greater precision and accuracy to a rather technical scientific formula that I won’t bother you with here. Suffice it to say that the number hasn’t really changed, and the principle essentially remains, it just got made more complicated (surprise, surprise!).

On the 7th July, at aphelion (furthest from the Sun), the Earth’s distance from the Sun is equivalent to 1.0167 AU. Back on 3rd January 2007, at perihelion (closest to the Sun), Earth’s distance from the Sun was 0.9833 AU which shows the ellipticity of Earth’s current orbit to be 0.967 where 1.00 would describe a perfect circle. So near and yet so far from man’s idealised state of perfection.

Planetwatch

Back to the here and now and a look at what’s happening up in the night skies of our ‘heavens above’ and what cycles we can see unfolding before our own unaided eyes. The Sun reached its northernmost peak last month on the 21st of June (the ‘Summer Solstice’) announcing the official start of summer, the bright orange star Arcturus in the constellation Boötes having heralded the warm days to come some few months back has since drifted to the western part of the night time skies making way overhead for the arrival of the summer constellations and the annual reappearance of the so-called ‘summer triangle’ of bright stars, comprised of: Vega in Lyra (the ‘lyre’ or ‘harp’), Altair in Aquila (the ‘eagle’) and Deneb in Cygnus (the ‘swan’). Ah, those balmy (or should that be ‘sticky’) days of summer are fast approaching.

One or two of our solar system planets are beginning to wilt in the increasing heat of the Sun, whilst one or two others seem to be basking in the rising temperatures. Some planets, like some people, do like it hot. Others may not.

MERCURY, having raced through inferior conjunction with the Sun at the end of June, appearing to us on our ‘magic roundabout’ to be going backwards as is always the case with an inferior conjunction, is still retrograde as July commences. He’s obviously not looking where he’s going, perhaps temporarily blinded by the light of his recent combustion, because he slips further south of the ecliptic than intended and ends up in the upper part of the constellation of Orion, the ancient Greek ‘hunter’, in the vicinity of the up-stretched arm holding a club to be precise. Realising the error of his ways he very quickly turns about-face, going stationary direct on the 10th of the month, and rather rapidly arrives at greatest western elongation (furthest distance west of the Sun as viewed from Earth) by the 20th, but only manages to stretch out as far as 20° W on this particular cycle and is a somewhat reluctant if not lazy morning star low down to the horizon in the second half of the month. Clearly he’s not in the frame of mind to exert too much effort at the moment, perhaps due to his earlier and somewhat unexpected encounter with a ‘big man with a club’ which seemed to knock a little of the ‘wind out of his sails’. Better days will come no doubt.

Our ‘angel of the night’, VENUS, has been overdoing it a bit herself recently. She’s been up ‘till late for months on end now, bewitching us with her dazzling night time routine, whilst at the same time striving for many a week to catch up with sulky SATURN who had previously moved off in a huff (goodness knows why? Although Saturn is perhaps a lot more sensitive than we ever imagine him to be or give him credit for). Well, here we are, the BIG DAY has finally arrived! Roll out the red carpet, strike up the band, announce it to the world, VENUS and SATURN make that close-up connection at long last. Not to be missed, the major happening of the month occurs on its very first day. But, oh dear, what a disappointment, the moment of meeting takes place during our daylight hours and we won’t be able to clearly witness the coming together of these two bodies. Will it be a warm embrace or more of the cold shoulder treatment?

There’s only one thing to do, watch the night skies on the evening before on the 30th June for any clues and tell-tale signs of how things are shaping up between them and then check again on the following evening of the 1st July to see what sort of reaction there’s been. It’ll only be a few hours after the very closest moment and we might possibly be able to tell from the body language how it’s all going. Do they seem to be lingering, hanging about a bit, reluctant to separate or has a gap opened up between them already? Because this conjunction is quite a close one, to be sure. Not all are, just because there’s a conjunction shown in the ephemeris or in a chart doesn’t really tell you how close the bodies actually get to each other because wherever they are physically located against the celestial sphere around the path of the ecliptic is then projected onto the ecliptic to give us their tropical position in celestial longitude.

For example, only last month MERCURY came to an apparent exact conjunction with the Sun, in celestial longitude that is, at 18:40 GMT on the 28th June and ostensibly went through the various classical astrological aspects of ‘under the beams’ (within 17° to 8° 30’ of the Sun), ‘combustion’ (within 8° 30’ to 17’ of the Sun) and ‘cazimi’ (within 17’ of the Sun). However, in the sky the very closest that Mercury came to the Sun was in fact only 4° 18’ as he dipped underneath the Sun in his orbit as viewed from Earth. No ‘cazimi’ here, only as close as ‘combustion’. Look how far apart the apparent ‘conjunctions’ and ‘oppositions’ between the Moon and Pluto really are, you might be astonished to see the angular distances, many not even within what we might deem to be a reasonable ‘orb’ of each other. So, when is a ‘conjunction’ really to be considered a ‘conjunction’ and when is it not?

As it happens, on this occasion, the particular conjunction in question between VENUS and SATURN on the 1st July is quite a close one, not so overlaid and intertwined as to be an occultation but certainly an intimate brushing together of planetary bodies at a mere 38’, just over a moonwidth, apart as VENUS gently slides her body beneath that of SATURN. Many sparks given off and much mingling of auras out there it would seem. All of this taking place under the stars of the nose of the regal lion, the constellation Leo.

Now we could just say what’s all the fuss about, as so could they, and simply move on about our collective business. But this encounter’s been arriving from a long way off, since last summer in fact, and we’ve been the silent witnesses to the many twists and turns of this coming together over many a month now. And as if to prove the point VENUS, having briefly drifted further on, turns herself around at the end of the month and heads back in the direction from which she’s just come towards yet another get-together with the ageing ex-monarch. Something’s surely cooking up there and there’s more unfolding of this tale still to come. This time around, however, there will be no stone left unturned in the desire to find a resolution to whatever question had been left hanging in the heavens these past ten months, so far without a satisfactory answer.

VENUS even manages to add a final touch of extra brightness, peaking at her maximum on the 14th of the month, but she is now being drawn towards the twilight zone, setting some two hours after the Sun at the beginning of the month (which was anything up to four hours only a few months back) but is down to only a few minutes by the end of the month. Within the constellation of Leo, and directly beneath Regulus on the 13th, but in the confused state she gets herself into in turning herself around at the end of the month she manages to somehow drift southwards across the constellation boundary lines and wanders into the constellation of Sextans, of all places!

SATURN, also within the constellation of Leo, but keeping to the straight and narrow as you might expect, he too ends the month dropping like a stone over the western horizon only a few minutes after the Sun as both he and Venus close in towards their respective conjunctions with the Sun next month. Methinks tiredness (as well as a little over-excitement perhaps) is setting in after a long hard winter of ‘catch me if you can!’ and both are long overdue a relaxing summer holiday. Together, perchance?

Well, so much for our trio of wilting planets: MERCURY, VENUS and SATURN. There are two planets who might well revel in a bit of sunshine: MARS and JUPITER, except that neither are anywhere near the Sun at the moment.

Hello, something is stirring out there in the darkness of those ‘cinderella’ hours around midnight. Would you believe it, MARS is at long last taking his courage in both hands and putting in that long-awaited reappearance, raising his ruddy head above the parapet of the horizon in the wee small hours of the night. And whereabouts in the firmament of stars might this long-overdue happenstance be taking place? Why, none other than in the stars of the constellation of Aries, where else might it be? He may be tropically in the sign of Taurus but up there in the ‘heavens above’ he knows where he can truly call ‘home’. He’s arrived safe and sound at ‘go’ and now it’s time to make his move. He’s been discreetly gaining in strength for some months and his apparent diameter is now twice the size it was at the beginning of the year and expanding all the while. He’s coming closer. Time to put on Holzt’s ‘Planet Suite’ and listen to the music. The planet of war is on the march once more. The time of reckoning is fast approaching. Let battle commence.

The giant gas planet of our solar system, JUPITER, arises in the early evening and is visible as soon as twilight allows. Commanding the night skies as only Jupiter can, he is located low down to the south in the constellation of Ophiuchus in that area of the night sky shrouded in the wispy, white clouds of the Milky Way which spill around the southern constellations of Scorpius and Sagittarius towards the galactic centre. He’s slowly sliding down the back of the Scorpion still trying to find the most comfortable position from which to ride this beast off into the night. By the end of the month he’s almost exactly above the bright red Antares and by then he’s off and over our western horizon shortly after midnight. What adventures await over yon distant horizon we wonder? Next month we’ll take a closer look at what’s going on in this section of the sky and why perhaps PLUTO has been lurking for some time in the vicinity.

Meanwhile, URANUS, amongst the stars of Aquarius, and NEPTUNE, in the stars of Capricorn, are both rising shortly before midnight and slowly drifting backwards towards their forthcoming oppositions to the Sun and possibly their best viewing opportunities of this year. Optical aid is probably needed to spot Uranus, although some now claim to have seen him with their unaided eyes, and is most certainly needed to catch sight of Neptune.

© A.S.Morton – June 2007