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Best time of year to look at the stars and planets

The Great Winter Triangle is formed in the cold winter nights by the three stars Procyon, Sirius (the brightest star of all) and Betelgeuse in the constellation Orion. Try to identify this triangle in the night sky and use it to assist you in finding the other constellations. Image: Stellarium

The Great Winter Triangle is formed in the cold winter nights by the three stars Procyon, Sirius (the brightest star of all) and Betelgeuse in the constellation Orion. Try to identify this triangle in the night sky and use it to assist you in finding the other constellations. Image: Stellarium

This month we are presented with some of the best evening skies for this year. The planet Venus blazes in the west and continues to dominate the evening sky in February, while Orion hangs high above it. The cold dark nights offer splendid views of the stars, especially after a thunderstorm passes and the air is very clear with lots of twinkling stars.

Sirius, the brightest star in the sky, lies low on the meridian, due south, below and to the left of Orion. On the other side we find Taurus, the bull, with the Pleiades star cluster close by.

On February 16, Venus reaches its brightest at a magnitude of -4.6. This is a scale that determines the brightness of objects in the sky. A faint star from an urban area would be of a magnitude of around 4 while Sirius has a magnitude of -1.5.

Venus is much brighter – in fact, sharp-eyed people might be able to spot this planet during broad daylight with the naked eye. Knowing exactly where to look helps, of course!

In a moonless dark sky, Venus is bright enough to cast a shadow, especially on light-coloured ground. Venus becomes brighter as it gets closer to the Earth, and through a telescope its crescent thins out while its size grows larger and larger. By the end of this month the crescent shape should be apparent even through a normal pair of binoculars.

Galileo (1564-1642) was the first to view the phases of Venus through his telescope in November 1610. He saw its crescent shape come and go, he saw it disappear behind or in front of the sun and reappear shortly afterwards, gradually forming a full phase as it went round one orbit every seven months. He realised that this could only occur if Venus orbited the sun, and his observations proved that the Earth was not at the centre. This was when the inquisitors in Rome pronounced this view heretical and he was forced to denounce his findings. Other astronomers, however, began to rethink the model of the universe and finally Copernicus and Galileo were proved right.

Venus shines brilliant white due to its reflective atmosphere. What lies beneath the thick atmosphere remained a mystery until the first space probes were sent in the early 1960s.

Mars is much fainter and lies above-left of Venus. Their separation increases towards the end of the month when they are joined by the moon on the evening of February 28.

Jupiter is the next planet to rise during the night, at around 11pm in the east, in the constellation Virgo. The giant planet, over 1,320 times the size of the Earth, continues to brighten as it reaches its closest point to our planet in April.

As the Earth rotates and faces different directions out into the vastness of space, Saturn rises around three hours before sunrise, in the southeast.

The full moon skirts into the Earth’s penumbral shadow between 11.30pm this Friday and 4am on Saturday. Only a slight darkening of the surface of the moon will be seen.

Two weeks later the new moon moves in front of the Earth to create a solar eclipse which sadly will not be visible from Malta. It will only be visible from South America, across the southern Atlantic and up to southwestern Africa.

Highlights this month

■ Brilliant planet Venus dominates the evening sky.

■ Orion – a big constellation representing an ancient hunter – is visible to the naked eye from most locations.

■ Moonless, dark nights reveal the faint winter Milky Way.

Astronomical events happening during February

Feb 5: Moon close to the star Aldebaran in Taurus
10: Full moon and penumbral lunar eclipse
15: Moon close to Jupiter
18: Last quarter moon
20: Moon close to Saturn
26: New moon and annular solar eclipse (not visible from Malta)

Alexei Pace is a member of the Astronomical Society of Malta.

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