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NIGHT SKY FOR SEPTEMBER: Fading summer days herald bright nights for star-gazers; 150 years ago controversy surrounding the discovery of the planet Neptune threatened to divide the astronomical community, says Birmingham Astronomical Society.

Astronomy is no stranger to controversy - witness the current debate about the discovery of a so-called tenth planet. Orbiting within the Kuiper Belt, it is larger than Pluto and further away.

It joins the steadily growing ranks of distant Kuiper Belt Objects (KBOs) and previously unidentified asteroids discovered over the last few years - so many, in fact, that naming each one is becoming more bizarre.

Suggestions for this latest include "Xena" after the TV Warrior Princess character.

Kuiper Belt objects are icy planetary bodies that inhabit the far reaches of our solar system and are believed to be remnants left over from the formation of the planets.

Some astronomers consider Pluto to be such an object and that it should never have been designated a planet.

Now that another larger body has been found 97 times further away from the sun than is the Earth and nearly one and a half times the size of Pluto - well, the news for Pluto's continuing planetary status isn't good . . .

Over 150 years ago, it was the controversy surrounding the discovery of the planet Neptune that threatened to divide the astronomical community.

On September 23, 1846, J G Galle of the Berlin Observatory officially confirmed the existence of an eighth planet using a set of co-ordinates passed to him by the French astronomer Urbain Jean Le Verrier. (Up until then, Uranus was the latest planet to have been discovered.) Nineteenth century astronomers had suspected the presence of another, unknown planet, for some time. Observations of Uranus appeared to show small, otherwise unexplained departures from its predicted orbit.

These wobbles, or perturbations, were assumed to be due to the gravitational pull of an unseen planetary companion relatively near by. Le Verrier had calculated the area of sky most likely to contain this new planet but failed to persuade a French Observatory to take up the search, so applied to the Berlin Observatory instead.

A year earlier, Englishman John Couch Adams had also been analysing the strange "wobbles" in the orbit of Uranus. His computations had led him to pinpoint Neptune as being in virtually the same position as Le Verrier was to find.

Armed with a letter of introduction from Professor Challis in Cambridge, Adams attempted to see the Astronomer Royal, Professor George Biddell Airy. He was hoping Airy would use his influence to organise a search using the co-ordinates he had worked out.

Having called at an inconvenient time, Adams was unable to see Airey in person although he did leave his figures for the great man to look at. History has it that Airy appeared uninterested and advised Adams to get Challis, at Cambridge, to do the search instead. Thus, Adams and our national pride were beaten to the punch by Le Verrier and the French (aided by the Germans).

But to lay the blame entirely at Airy's door would be unfair as he was intrigued enough by Adams' work to write to him requesting more details. Unfortunately, he received no response.

Added to this, back in Cambridge, Challis had actually found the new planet using the Northumberland telescope but failed to recognise it. Had he re-checked his observations of the particularly bright object he had noted that evening of August 4, he and Adams would have pipped Le Verrier and Galle to the post.

At first, Le Verrier was given sole recognition for discovering Neptune but a year or so later, Adams was awarded joint credit.

Perhaps this was due to the fact that, despite events, the two men had a mutual respect for each other's work and, after meeting in 1847, became good friends.

The subject of this historical furore may be seen in the evening sky on the 15th of this month when it will be 5 degrees north of the moon. Its sister planet, Uranus, is at opposition on 1st (opposite side of the Earth from the sun).

Jupiter is rapidly sinking into the horizon and will be all but lost in solar glare by the end of the month. On 2nd though, it will be close to Venus in the evening sky. Look to the west just after sunset to see these two bright planets.

A few days later on 7th, the new crescent moon will join them together with first magnitude star, Spica in Virgo, making a pleasing little group and a good photo opportunity.

On 18th, Mercury is in superior conjunction. It passes behind the sun and is then pretty well out of view all month. Saturn emerges further into the eastern morning sky, now in the constellation of Cancer. It will be five degrees south of the moon on 28th.

Mars is becoming ever more prominent in the early hours and will be 6 degrees south of the moon on 22nd in the constellation Taurus. Look to the east after midnight. A telescope should show the polar ice cap and other discernible features on the Red Planet.

Autumnal equinox takes place on 22nd - the time the sun moves into the southern celestial hemisphere. At this point, there should be equal hours of daylight and darkness with the days shortening steadily from then on.

Shorter days mean longer nights and that is good news for astronomers.

Joining the Plough, Cassiopeia, and Pegasus after midnight, some of the traditional winter star groupings begin to appear in the east. Look out for the glittering Pleiades (Seven sisters), followed by bright Aldebaran in the V-shaped cluster, Hyades. Heralds of the winter constellations, they signify the true passing of summer.

If you would like to learn more about the night sky, contact us through our website:


This image of Neptune was made using pictures taken by Voyager 2
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Title Annotation:Features
Publication:The Birmingham Post (England)
Date:Aug 27, 2005
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