The Night Sky

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Current Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during March 2017.

Highlights of the Month

1st-4th March - after sunset: Three planets and (on the 1st) a very thin crescent Moon. On these nights, Venus is 12 degrees down to the lower right of Mars, both in the southwest, and between them lies Uranus. On the 1st of March, they will be joined by a very thin waxing crescent Moon.

March 4th, following 10pm: The Full Moon occults Gamma Tauri in the Hyades cluster. During the late evening, the first quarter Moon will occult the star Gamma Tauri, which forms the peak of the triangular shaped Hyades Cluster. In North America, the Moon can be seen occulting Aldebaran.

10th March - all evening: The Moon, two days before full, passes just below Regulus in Leo.

March 15th - before dawn: The Moon lies close to Jupiter and Spica. Before dawn, Jupiter appears between the Moon to its upper left and Spica, Alpha Virginis, down to its lower left.

March 20th - before dawn: Saturn near the third quarter Moon. Before dawn on the 20th and looking South, Saturn will be seen over to the right of the third quarter Moon.

March 6th and 19th: The Alpine Valley. These are two good nights to observe an interesting feature on the Moon with a small telescope. Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end is a cleft called the Alpine Valley. The dark crater Plato will also be visible nearby.

The Planets

  • Jupiter, moving towards opposition on April 7th, lies in Virgo initially some 4 degrees above its brightest star, Spica. With a small telescope, it should be easy to see the equatorial bands in the atmosphere, sometimes the Great Red Spot, and up to four of the Gallilean moons.

  • Saturn rises well after midnight and will be highest in the pre-dawn sky. It will be high enough to make out the beautiful ring system which, at over 26 degrees to the line of sight, are as open as they ever become. Its elevation this year never gets above 18 degrees, so the atmosphere will hinder our view of this planet.

  • Mercury passes through superior conjunction on March 7th and becomes visible around the 15th in bright twilight just above the western horizon. On the 19th, on its way up, it passes Venus, on its way down, some 9 degrees to its right.

  • At the beginning of March, Mars can be found in Pisces up and to the left of Venus. As the month progresses, Mars continues to move eastwards (moving into Aries on the 8th) whilst Venus falls back towards the western horizon.

  • Venus starts the month dominating the western sky, shining virtually at its brightest with a magnitude -4.8. It lies due south in mid-afternoon and can even by seen with the unaided eye. After dark in a very dark location, it can even form shadows. On the 1st of February, it has its highest elevation at sunset during the month at ~30 degrees. But then, as the month progresses, it falls back towards the Sun and passes in front of it on the 25th. Very unusually, Venus is far enough north of the Sun that it will start rising before dawn on March 15th, some 10 days before inferior conjunction. Thus it could be seen both at nightfall and at dawn for a few days.


Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during March 2017.

As we approach the autumn equinox on the 20th of March, our evenings are quickly drawing in, we have more time to get outside observing our beautiful Southern skies. The Milky Way, or te Ika Roa arches high across the sky from north-northwest to south-southeast after dark.

Canopus, the second brightest star in our night time sky, is just to the southwest of overhead. Canopus is circumpolar from our position here and is considered to be a tapu, or sacred to Maori. Around halfway from Canopus to the southwest horizon is Achernar, a blue main sequence star around 7 times more massive than the Sun but over 3000 times more luminous. Achernar is part of a binary system, with a fainter, less massive A type companion. Achernar and Canopus form a roughly equilateral triangle with the Southern Celestial Pole. Unlike the northern hemisphere, we have no nearby bright star to mark this point, so we have to estimate it from the surrounding stars.

Not far from the southern celestial pole towards Achernar, you may be able to spot two small fuzzy patches of light, easily seen with the naked eye on a dark, moonless night. These are the Large and Small Magellanic Clouds, two small irregular dwarf galaxies that neighbour our own. Whilst these galaxies are much smaller than the Milky Way, combined they still contain billions of stars. The best time to look out for these galaxies is around the new moon on the 28th of the month, when they will be high in the south after dark.

Alpha and Beta Centauri are the first and second brightest stars in the constellation of Centaurus. The constellation, which is currently the 9th largest in the sky, once incorporated the constellations of Lupus and Crux. The globular cluster Omega Centauri, sits just to the east of the bright band of our Galaxy. This is by far the largest and brightest globular cluster in the Milky Way. The cluster is relatively easy to find even with the naked eye, appearing as a fuzzy star around 13 degrees northeast of Gamma Crucis at the top of the Southern Cross. With a small telescope the cluster becomes a glowing, shimmering ball of stars.

Further east and low on the horizon after dark is the constellation of Virgo, with its brightest star Spica rising just as twilight ends at the start of the month. Spica is actually a particular type of binary system called a rotating ellipsoidal variable, where its two components orbit so close together that they become egg-shaped rather than spherical. Virgo is also home to the Virgo Cluster of galaxies, containing perhaps as many as 2000 members. Just below and to the left of Spica this month is bright, golden Jupiter. With a decent pair of binoculars, you should be able to pick out Jupiter's four largest moons. The nearly full moon will pass close by on the 14th and 15th of the month.

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