Discovered last August by Terry Lovejoy, comet C/2014 Q2 (Lovejoy) is the object in the sky currently attracting most attention from astro­nomers all over the world. The comet, the fifth discovery of this expert Australian comet hunter, has gotten brighter as it approached the Earth last month and as it moved closer to the sun last Friday.

Comets are fascinating minor objects in our solar system, consisting primarily of a dust and ice mixture. When these boulders start getting close to the sun, the heat acts on the frozen elements to create a huge gaseous atmosphere (coma) around the comet nucleus. This usually has a diameter of around 10,000 to 100,000 kilometres.

Solar wind, that is, the stream of high-velocity particles emitted by the sun, interacts with the coma and pushes the gas and dust in the opposite direction to the sun, thus forming the comet’s long tail. Comets’ tails can become millions of kilometres long, even reaching the Earth.

Giant planet Jupiter gets closest to the Earth this month. Even a common pair of binoculars, held steadily, will show the changing motion of its four largest moons

Lovejoy discovered the comet which now bears his name by scanning the morning sky before sunrise and the evening sky after sunset, using a camera attached to his telescope. By taking a series of photographs of the same area of sky, Lovejoy was able to detect the motion of this comet among the stars when it was still very far away from the sun.

He also discovered another very bright comet in 2011 which survived a very close encounter with the sun, which usually disintegrates most other so-called sun-grazing comets. Only few manage to survive the extreme heat and radiation, including the Great Comet of 1843 and Lovejoy’s C/2011 W3. It will now become very difficult to observe as it goes farther and farther away (and fainter) as it moves back into the depths of space. However, astro­nomers in Malta were lucky as a few days of good weather around its closest approach to the Earth allowed it to be seen with the naked eye and observed very well through binoculars and small telescopes.

But the comet was not the only thing to be seen last month – tiny planet Mercury managed to make itself visible as it passed close to brighter Venus, which still shines brightly in the west-southwest during evening twilight. It will get higher and brighter as we get closer to spring. But Mercury has now disappeared deep into the glow of sunset. Close to Venus is planet Mars, which now is far from the Earth, setting at around 8pm.

Giant planet Jupiter, on the other hand, gets closest to the Earth this month, so it is big and bright. Even a common pair of binoculars, held steadily, will show the changing motion of its four largest moons, which are first thought to have been seen by Galileo Galilei.

www.maltastro.org/blog

Astronomical events during February

Alexei Pace is president of the Astronomical Society of Malta.