Stargazing in May: Is there life on Mercury? – The Independent

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f youve always harboured a yen to spot the innermost planet of the Solar System, then this is the month to tick it off your bucket list. Shy Mercury is putting on its best evening display of the year, and we even have a signpost to help you find it, in the shape of Venus, the brilliant Evening Star.

Look west after sunset and you cant miss glorious Venus. Wait until the sky gets almost dark, around 9pm, and youll spot another star above it, about ten times fainter. Thats your quarry. And you can rightly feel smug. Its rumoured that the sixteenth-century Polish astronomer Nicolaus Copernicus, who said that the Sun rather than the Earth is the centre of the Solar System, wasnt able to observe Mercury because of the mists rising from the nearby River Vistula.

Even a powerful telescope isnt going to reveal much on this tiny planet, hardly larger than our Moon. Fortunately, its surface has been scanned in close-up by two visiting Nasa spacecraft, Mariner 10 and Messenger. They have revealed a barren surface, almost completely disfigured by craters of all sizes.

Mercury has scarcely any atmosphere. Its surface is blasted by solar radiation and by the Suns heat during the daytime, at least. The nightside is exposed to the total chill of space, so temperatures at the equator swing from 430C during the day 170C at the dead of night. Mercury rotates so slowly that its day from noon to noon is actually twice as long as its year.

Another oddity is Mercurys extreme density. Unlike the Earth, it cant be made mainly of rock. Instead, almost the whole planet consists of a huge iron core, with just a veneer of rocky crust over its surface. Astronomers dont why. According to one theory, most of the crust was stripped away by a giant cosmic impact early in the planets history. Or it may just have been born so close to the young Suns intense heat that rocks remained as a gas while iron condensed into a giant metallic blob.

Scientists hope to learn the answer when the European BepiColombo arrives in 2025 and slips into orbit around Mercury to investigate the planets remaining mysteries. Even more intriguing than its birth is that fact that, at its poles, this scorched planet has craters harbouring vast amounts of ice.

Yes, frozen water on the closest planet to the Sun! Its hidden in the depths of craters at Mercurys poles, where the Sun never rises and conditions are perpetually dark and cold. Astronomers first detected the ice in 1991, using powerful radar based on the Earth, and the Messenger spacecraft has revealed theres up to a trillion tonnes of ice, in places possibly 20m deep.

This discovery opens up the possibility of astronauts voyaging to the innermost planet, and living on Mercury. Theres water aplenty for drinking, and for growing crops in pressurised domes. More than that, colonists could use the power of the intense sunlight to split the water into oxygen for breathing, and to burn with hydrogen as a rocket fuel.

With Venus far too hot for habitation, and the outer planets so remote and cold, some space scientists are saying that after Mars Mercury is mankinds next natural home in space.

Whats up

The brilliant Evening Star, Venus, hangs low in the northwest as the sky grows dark, outshining all the stars.

As Ive mentioned above, near Venus you can locate Mercury. The innermost planet never strays far from the Sun in the sky and this month provides our best opportunity for seeing this elusive world in 2021: after Venus has set, we have the unusual treat of seeing Mercury so long after dusk that the sky is dark.

The night sky at around 11pm this month

(Nigel Henbest)

At the beginning of May, Mercury lies to the left of the famous Seven Sisters star cluster, the Pleiades. By 9 May, this little world has moved upwards and Venus is close to the Pleiades. Mars, shining a distinctive ochre hue, lies to the upper left of Mercury, and considerably fainter.

Were in for a lovely sight on 13-15 May, as the crescent Moon moves in turn past Venus, Mercury and Mars.

If youre up in the wee small hours, look out for the bright giant Jupiter and its fainter sibling Saturn, rising in the southeast around 3 am.

Well all certainly be looking towards the sky on the evening of 26 May, for the biggest and brightest full moon of the year. Its just 357,314km away from the Earth, and appears 30 per cent more brilliant than the faintest full moon. People around the Pacific Ocean will experience a total lunar eclipse.

Diary

9 May: Venus near the Pleiades

11 May, 7.59pm: new moon

13 May: Moon near Mercury and Venus

14 May: Moon between Mars and Mercury

15 May: Moon near Mars

16 May: Moon near Castor and Pollux

17 May: Mercury at greatest elongation east

19 May, 8.12pm: first quarter moon near Regulus

23 May: Moon near Spica

26 May, 12.14pm: full moon near Antares; supermoon; lunar eclipse

28 May: Mercury near Venus

Philips 2021 Stargazing (Philips 6.99) by Heather Couper and Nigel Henbest reveals everything thats going on in the sky this year

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Stargazing in May: Is there life on Mercury? - The Independent