Viewing southern skies in February

FREIDL HALE
Last updated 09:33 05/02/2014

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Jupiter still shines brightly in our night sky, at its zenith before midnight at the beginning of the month. Mars and Saturn follow its path across the sky, but much later in the night, Mars rising about 4 1/2 hours after Jupiter, and Saturn over an hour after Mars.

I finally spotted Mars last week, for the first time since it moved into our morning sky last April. On the 24th it was near the waning Moon, and below (north of) the bright star Spica. Then last night (the 28th) the electricity failed here, and there were no town lights. The Moon had been in our daytime sky and was also gone for the night. It was the best night sky I have seen in Lake Tekapo in my decade living here. It seemed that an order of magnitude more stars were visible to the naked eye. Orange Mars and blue-white Spica were brilliant and steady in the dark sky at 4.30 in the morning.

The Milky Way, our edge on view of our own galaxy from inside the galaxy, was bright and wide and cluttered with stars. Our close neighbours, the Magellanic Clouds, in the south were impossible to miss, like chunks drifted apart from the Milky Way.

In January I missed out informing you all that the Moon would be new twice in the month, just after midnight the morning of the 2nd, and again in the morning of the 31st. The next one won't be until March 1st, so February misses out. However February 1st is the beginning of the 9th Maori month, Hui- tanguru. The Moon will be fullest at midday two weeks later on the 15th so will be at its best on both the nights of the 14th and 15th.

The Moon also will feature near three planets this month. After 10.30pm on the 19th a waning but still large Moon will rise in the east and again be close to Mars. Mars will appear dim in the bright light of the still near-full Moon, but you should be able to spot it by its distinct orange tint when compared to the star Spica which will be above it. Two days later around midnight a slightly smaller Moon will be near Saturn which has a slight golden tinge. Then, if you are up either very late on the 25th or very early on the 26th, you may see Venus together with a slim crescent of Moon above the eastern horizon sometime around 3.30am.

The part of the solar system containing the Sun and the planets in orbit around it is almost flat. This plane is called the ecliptic. If our Earth's axis of rotation was perpendicular to the ecliptic, the paths of the Sun and other planets through our sky would be pretty much directly over the equator. We also wouldn't have much in the way of annual changes of season.

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But we are tilted, 23 degrees off the perpendicular, and we call the path of the Sun and planets around our sky the ecliptic. As it turns out, the Moon orbits the Earth close to the ecliptic as well, and not around our equator. So the Moon roughly follows the same path across the sky as the planets. That is why we get these lovely conjunctions of the Moon with the planets. The Moon completes its cycle around us approximately every 29-and-a-half days giving it lots of opportunities to be seen near a bright planet.

Speaking of planets being in the ecliptic, on February 18 in 1930 a young researcher, Clyde Tombaugh, discovered Pluto using the 13-inch Astrograph telescope at Lowell Observatory in Arizona.

The lad's university plans were foiled by bad weather that ruined his family's crops, but he had a good resume having always been a keen amateur astronomer and observer, and having built his own telescopes, grinding the lenses and mirrors himself.

So Lowell Observatory hired him specifically to search the sky for the predicted 9th planet, Planet X, thought to exist beyond Neptune because of pertubations to the orbit of Uranus that were not fully explained by the discovery of Neptune. Pluto's existence was confirmed by comparing photos of a section of sky taken on different dates, looking for an object that changed position from one to the other. This low-tech technique is called "blink" comparison, and still has a place in hunting asteroids, comets, and supernovae.

Pluto's orbit is inclined 17 degrees to the ecliptic and is quite eccentric in other ways as well. In 2006 it was given the new category of dwarf planet, which it shares with several other solar system objects.

Meanwhile, Clyde Tombaugh died at the age of 90, having completed his university studies a few years after his most famous discovery, and earned his Masters degree in Astronomy. The New Horizons spacecraft, launched in 2006 to explore Pluto and scheduled to arrive there next year, carries a portion of Clyde Tombaugh's ashes, suitably interred. He is credited with the discovery of nearly 800 asteroids, periodic comet 274P/Tombaugh- Tenagra, hundreds of variable stars, star clusters, galaxy clusters and a galaxy supercluster.

If you have a question or would like to receive or share information, please write to me at PO Box 152, Lake Tekapo 7945, or contact me by email: stars@tekapostarlight.co.nz

Clear skies at night,

Freidl Hale at Tekapo Starlight

- The Timaru Herald

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