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The night sky for April 2015

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during April 2015.

Orion is sinking in the west as darkness falls, followed by Gemini and its bright stars Castor and Pollux. Further towards the south is the faint constellation of Cancer. It contains the Beehive Cluster, an open star cluster visible in binoculars, and currently plays host to the planet Jupiter as well. Leo is due south in the evening, with its bright star Regulus. Nearby, in Virgo and Coma Bernices, is an area called the Realm of the Galaxies. In this region, an 8" telescope can pick out a number of galaxies that are part of the Virgo Cluster, the largest cluster of galaxies in our local universe and itself part of a much bigger supercluster. Higher up is Bootes, with its bright star Arcturus, and overhead is Ursa Major. Later in the night, Lyra and its bright star Vega rise in the north-east.

The Planets

Highlights

Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during April 2015

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The night of the 4th-5th sees the first lunar eclipse of the year, and also the backward move of the clocks in parts of the southern hemisphere. In Wellington, New Zealand, the penumbral phase begins at 22:03 NZDT (New Zealand Daylight Time, 13 hours ahead of Universal Time) as the Earth begins to obscure sunlight from the Moon's surface. The umbral phase, when sunlight is fully blocked from part of the Moon, starts at 23:17. The Moon is cast into total shadow for 7 minutes, from 00:57 to 01:04. The umbral phase ends at 02:44, while the penumbral phase finishes at 02:58 NZST (New Zealand Standard Time, 12 hours ahead of Universal Time).

The Moon is in Virgo during the eclipse, about halfway between Jupiter in the north-west and Saturn in the east. Venus appears brightly in the evening, and sets 2 hours after the Sun by the end of the month. Saturn is in Scorpius, a little below the red star Antares. It rises around 22:00 NZDT at the beginning of the month and 19:00 NZST at the end.

The constellation of Centaurus is high in the east after dark, with its two brightest stars, Alpha and Beta Centauri, pointing towards Crux, the Southern Cross. Centaurus is one of the largest constellations and contains many bright stars, clusters and nebulae. The globular cluster Omega Centauri, the largest and brightest in the Milky Way Galaxy, appears similar in size to the full Moon when seen with the naked eye at magnitude +3.7. Binoculars reveal individual stars and a dense core. With a population of stars that are around 12 billion years old, it is a relic of the early Universe and may be the remnant of a dwarf galaxy that merged with the Milky Way. NGC 3766 and NGC 5460 are two open star clusters in Centaurus, both just visible to the naked eye. The planetary nebula NGC 3918, the 'Blue Planetary', is also located there, and, at magnitude +8, its blue oval shape can be seen with a small telescope. Centaurus hosts one of the closest galaxy clusters to Earth. Separately, it is home to NGC 5128, the galaxy known as Centaurus A. Centaurus A is elliptical, but has a dark dust lane across the middle, and the supermassive black hole at its heart is thought to be consuming a spiral galaxy with which it has merged. As a result, it emits relativistic jets that can be detected at radio and X-ray wavelengths. Located less than 5 degrees from Omega Centauri, Centaurus A is the fifth-brightest galaxy in our sky (excluding the Milky Way) and is easily visible in binoculars. The bright central bulge and dark lane may be viewed with larger binoculars, while a telescope reveals more of the galaxy's structure.

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The Night Sky This Month is one part of the Jodcast. The full show contains the latest news, interviews with astronomers, answers to listener questions and more.

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