Starguide: April

By Jenny Winder

Astronomy-Amateur Author: Halfblue via Wikimedia-Commons

What to look out for in the April night sky

The constellation Leo dominates the Southern sky this month. Look for the ‘Sickle’ asterism  like a back to front question mark with the bright star Regulus at the base. On April 3rd look for Mars near Regulus above the almost full Moon. On April 15th Mars reaches its stationary point, halting in its westward journey across the sky, before moving back eastward from April 16th.

Venus and Jupiter are going their separate ways after giving us a spectacular conjunction last month and we will lose Jupiter from the night skies by the end of the month. Venus is still brilliant enough at magnitude -4.4 to be seen in daylight, setting in the northwest after midnight. On April 2nd to 4th it will pass through the Pleiades in Taurus. By April13th it will form a triangle with the Pleiades & Hyades & they will be joined by the waxing crescent Moon on April 23rd.

Saturn, near Spica in Virgo to the left of Leo, reaches opposition to the Sun, as seen from Earth, on April 15th. This means it will be visible all night. It is also closest to Earth in its orbit so bigger & brighter. The rings are currently at a favourable tilt to Earth and appear brighter during opposition due to the Seeliger effect: usually the particles that make up Saturn’s rings cast shadows on the particles behind, making them darker, but during opposition the shadowed particles are hidden behind the fully illuminated particles with the net effect that the rings appear at their brightest.

Also in Virgo,  below the main pattern of stars, lies the Sombrero Galaxy, M104. This unbarred spiral galaxy is a magnitude 9.5 and  28 million Light Years from Earth. It contains one of the most massive, supermassive black holes ever measured in a nearby galaxy.

The Moon this month will be Full on April 6th and New on April 21st. Luckily this New Moon coincides with the peak of the Lyrid meteor shower, giving the best conditions (clear skies permitting) to view the typically bright trails of this shower. The Lyrids were first noted by the Chinese in 687BC which makes them the oldest meteor shower recorded. They are caused by the debris from Thatcher’s comet and usually have a Zenithal Hourly Rate (ZHR) of 10 to 20, this is the typical number of meteors seen per hour, under the ideal conditions of a dark sky, if the radiant were directly overhead. The lyrids have been known to produce unexpected peaks of up to 100 meteors per hour so is worth making the effort to see. The radiant lies in the constellation of Lyra which rises at about 10pm in the Northeast. Wrap up warm & either lie on the ground or in a reclining garden chair. Look about 45 degrees from the radiant or most meteors will pass either side of  your head.  As with all meteor showers the best time to view them is after midnight, the hours before dawn being best as the Earth’s rotation brings the observer to a position where the meteors are striking our atmosphere head on.

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