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Mercury was well placed for early birds in the tropics and southern hemisphere during the first half of last month before been lost to the Suns glare as it headed towards superior conjunction. Moving into June, Mercury is now past superior conjunction and reappears later this month in the evening sky.
Once again, it is southern hemisphere and tropics observers who have all the luck. From Sydney, Australia (35S), Mercury is visible for a few weeks from the middle of June. At its highest, Mercury will be more than 10 degrees above the horizon at the end of June / beginning of July. Unfortunately, as the planet moves higher in the sky it also dims in brightness, fading from mag. –1.8 to 0.4 as the month goes by. For northern hemisphere observers the planet is visible for a shorter time and located much lower in the sky; at best only 5 degrees or so north of the horizon when seen from London, England (51.5N).
Easily the celestial highlight of the month or even the year takes place on June 5/6 when Venus reaches inferior conjunction and transits the Sun. This extremely rare, only twice in a lifetime event, occur in pairs of 8 years with a gap of more than 100 years between them. For the current cycle, first performance took place on June 8, 2004 when the entire transit was visible from Europe, most of Asia, and almost all of Africa. The second show is on June 5/6 with the complete transit or at least part of it visible from most of the world including Europe, Asia, North America, Central America and Australasia. Missing that, you will have to wait until 2117 to catch this spectacle once more!! The diagram below shows the path of Venus as it moves across the Suns disk.
The Sun will turn into a spectacular ring of fire and light up the sky on May 20th when an annular solar eclipse is visible over the Pacific Ocean, China, southern Japan, and western US.
This type of eclipse – the first one in the US for almost 18 years – occurs when the lunar disk is not quite large enough to fully cover the Sun. At the time of maximum eclipse, the Moon forms a black hole in the centre of the Sun surrounded by a sensational bright ring - the ring of fire.
The latest data obtained from NASA's DAWN spacecraft - currently orbiting Vesta - suggests that the asteroid closely resembles a small planet or the moon rather than other asteroids. Results published in the journal Science on Thursday May 13, 2012 reveal that the 4.56 billion year old asteroid is believed to be a remnant intact proto-planet from the earliest time of solar system formation. This is based on an assessment of data obtained from DAWN during the 10 months in which it has been orbiting the giant asteroid.
From the information obtained, scientists confirmed Vesta has a metal-rich core, just like rocky planets Mercury, Venus, Earth and Mars. The core has been calculated to be about 220 kilometres (135 miles) across, equivalent to approx. 40% of the radius of Vesta, or roughly 18% of its total mass.
Mercury remains well placed in the morning sky during the first half of May for observers in the tropics and Southern Hemisphere. It is visible towards the east-north-east just before sunrise. The planet increases in brightness from mag. 0.0 on May 1st to mag. –1.0 on May 17th as it moves closer to the Sun in the sky.
For Northern Hemisphere observers, Mercury is poorly positioned in May. Despite a reasonable separation from the Sun at the start of the month, it rises only about half an hour before the Sun from London, England. For the remainder of the month, it remains close to the Sun and difficult to observe.
The planet reaches superior conjunction on May 27th and perihelion on May 29th. At perihelion it is located only 0.307495 AU (approx. 46 million km or 28.6 million miles) from the Sun.
Venus begins the month as a brilliant evening star, shining at mag. –4.7, setting four hours after the Sun in Northern temperate latitudes and nearly 2 hours for observers in the tropics and the Southern Hemisphere. On May 6th, a nice conjunction occurs when Venus passes only 49 arcminutes from mag. 1.7 star Elnath (beta Tauri). With a mag. difference of about 6, Venus appears more than 250 times brighter than Elnath!
The planet then draws rapidly towards the Sun as the month progresses and by the last week of May will be difficult to pick out against the bright evening twilight.
Mars has now completed its latest retrograde motion and is now moving direct in Leo. It is visible as soon as night falls and sets in the early hours of the morning. The planet has been moving back and forth in Leo for some time, but now its again moving eastwards the motion of the Red planet against the background stars is noticeably quick. At the beginning of the month Mars is only a few degrees from Regulus, the brightest star in Leo, by the end of the month the distance has more than doubled.
Last year was not a great year for meteor observers with the Moon interfering badly with most of the great annual showers. But this year promises to be much better and in April the Lyrids return, this time under favourable moonless skies.
Shower activity for the Lyrids begins around April 16th and lasts for about 10 days, peaking on April 22nd at 05:30UT. Since a certain element of unpredictability is attached to all meteor showers, it is well worth looking not only on the night of peak activity but also on the preceding and following nights.
Last month Mercury reached greatest eastern elongation of the Sun and for a few days was an easy evening target for the northern hemisphere, but not well placed for southern hemisphere observers. This month the roles are reversed. The elusive planet, which moves so fast that it orbits the Sun once every 88 days, recently passed inferior conjunction and reaches greatest elongation west on April 18th (27 degrees).
For southern hemisphere sky watchers this is the best morning display of the year. For most of the month, observers will be able to follow Mercury in the eastern sky before sunrise. At greatest elongation on the April 18th, Mercury rises two hours before the Sun and at magnitude 0.3 should stand out against the faint background stars of Pisces. A thin crescent Moon will be nearby. On April 23rd, look 2 degrees to the north of Mercury with binoculars and you may be able to spot magnitude 5.9 Uranus.
Recent analyses of data from the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) space probe orbiting the planet Mercury suggest that that the nearest planet to the Sun was once an active and dynamic planet.
The data shows that some geological process distorted impact craters on the planet's surface after they formed. The new findings challenge the long held view by many that Mercury for most of its existence has been a dead planet.
For the last 6 months or so, Comet Garradd (C/2009 P1) has put on a good show for observers. During this time, the distant comet never came within 1.27 AU (188 million kilometers or 118 million miles) of Earth and hovered around magnitude 7 for a long time before peaking at magnitude 6.3 in late February 2012.
One notable event occurred on the 3rd February when observers and imagers scrambled for their scopes and cameras to record Garradd as it passed just one third of a degree from bright globular cluster M92. Both visually and photographically the two objects appeared superb, sitting side-by-side, almost equal in brightness despite the massive difference in distance between them.
Flying in formation only 55km (34 miles) above the lunar surface, NASA's twin GRAIL (Gravity Recovery and Interior Laboratory) space probes have now officially begun mapping the lunar gravitational field. This science collection phase of the mission began late on Tuesday 6th March 2012 and will over the next 84 days produce a high-resolution map of the lunar gravitational field in unprecedented detail.