SkyMatters: How to spot Venus in the sky on Valentine's Day

Romance is in the sky in February – and Venus is the hottest planet in the solar system, writes Niall Smith
SkyMatters: How to spot Venus in the sky on Valentine's Day

Romance is in the air in February as we welcome (or perhaps merely acknowledge!) Valentine’s Day on the 14th. Venus is the mythological Greek Goddess of Love and this year you can impress your valentine by pointing out the planet Venus as it shines brilliantly in the southern sky from dusk until about 9pm (depending on your local horizon). Find a restaurant with a south-west facing window and you can even watch it as it gradually dips below the horizon while you sip a glass of bubbly. You can impress your Valentine further by explaining that Venus is the hottest planet in the solar system, not because it is the closest to the Sun – that honour going to Mercury – but because it is undergoing a runaway greenhouse effect. Venus’ atmosphere is composed of 96% carbon dioxide that acts as a heat-trapping blanket, raising the surface temperature to over 450 degrees C, or hot enough to melt lead.

To make matters worse the clouds which permanently obscure its surface from view are composed of sulfuric acid, so if the heat doesn’t get you the sulfuric acid rain certainly will. For adventurous valentines with a pair of binoculars or small telescope, and do think carefully about bringing either on a first date, you can see that in February Venus is about 30% illuminated and will appear as a small crescent.

The first observation of the crescent Venus was by Galileo in 1610 and it had major implications for our understanding of the solar system as it could most easily be explained if one assumed the Sun, not the Earth, is at the centre with the planets revolving about the Sun, overturning almost 2000 years of perceived wisdom. Technically, Venus is at its brightest on 17th in February and it remains visible in the evening throughout the month. To the upper left of Venus, a couple of Moon diameters away, is Mars – the Greek God of War.

While nowhere near as bright, it does have a distinct red hue, reminiscent of blood and hence the association with war. 2017 is not a particularly good year for observing Mars due to its considerable distance, but that will change in 2018. In any case, pointing out two planets to your valentine has the potential to win you major brownie points.

The morning sky is lit up by the giant planet Jupiter throughout the month. Though not as visually bright as Venus it is still a spectacular object and it actually rises around midnight.

Throughout February it can be found close to the bright star Spica, or Alpha Virginis, the “alpha” meaning the brightest star in the constellation of Virgo. Spica is not one, but two stars, separated by a mere 18 million km that orbit each other in only 4 days. The two stars are not directly visible with a telescope and a technique called spectroscopy is needed to infer there are actually two stars.

On Feb 10/11th there is a “penumbral” eclipse of the Moon, when our nearest neighbout passes into the Earth’s partial shadow (penumbra). Careful skywatchers will notice a slight dimming of the Moon, with the greatest effect at 00:43 on Saturday 11th. A penumbral eclipse is not the same as a partial eclipse, however, where you will see a definite “bite” taken out of the Moon.

DID YOU KNOW?

The temperature on the night side of Mercury plunges to -173 degrees C even though the planet is only 1/3 of the Earth-Sun distance.

The reason is that without an atmosphere there is no way for the heat from the hot side to be effectively transported to the cold side.

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