Science: Seven silver-blue sisters wreathed in cloud: Star clusters will vie for attention next month, but the loveliest is still the Pleiades, say Nigel Henbest and Heather Couper

ALFRED Lord Tennyson could not have put it better: 'Many a night I saw the Pleiads, rising through the mellow shade, / Glitter like a swarm of fireflies, tangled in a silver braid.' His poem 'Locksley Hall' contains the most beautiful - and accurate - description of the Pleiades star cluster so far achieved.

This tiny clutch of blue-white stars, clearly visible now for most of the night, really does look like a glittering, silver swarm; and while the Pleiades (the 'Seven Sisters') are undoubtedly the most lovely of all, they have some competition in February. Several rivals are on view, and are worth more than a second glance, particularly if you have binoculars.

Unlike the constellation patterns, made of unrelated stars that lie in roughly the same direction in space, clusters are genuine star groups. They consist of stars born relatively recently in cosmic terms: tens of millions of years ago.

Since stars are born in tight clumps (as you can see in the centre of huge gas clouds such as the Orion Nebula) their closeness in a cluster is a reflection of their youth. As stars grow older, they shuffle off the gravitational bonds of their neighbours and plot a solo course around the galaxy.

The youngest star clusters visible in February ride high in the sky between the constellations of Perseus and Cassiopeia. The 'double cluster' makes a glorious sight through binoculars; each of its parts is about the size of the full Moon, and they look identical - except that, at 3 million years old, 'chi Persei', the left-hand cluster, is 2 million years younger than its neighbour, h Persei.

Each cluster contains thousands of fiercely burning young stars, of which a couple of hundred can be seen through a moderate telescope. They are so luminous that they can easily be picked out at 7,000 light years away.

On the other side of the sky lie two older clusters. Age mellows them: their stars modify their energy output, and they begin to pursue their own paths. Middle- aged clusters, such as the Hyades in Taurus and Praesepe in Cancer, lose the 'jewels on black velvet' look of their younger cousins.

Both clusters were born 630 million years ago, and are heading away from the Sun. In fact, the motion of the V-shaped Hyades - at 149 light years away, the closest to the Sun - offers astronomers a means of measuring distances in space. Praesepe, 520 light years away, appears fainter and more compact; it is a fine sight through binoculars.

But, at last, to the Pleiades: 410 light years away and 70 million years old, the cluster has just the right combination of age and distance to create a bright, compact appearance. First logged by Chinese astronomers in 2357 BC, it has played a big part in the beliefs and rituals of many cultures. The Aztecs used to time their most gory human sacrifices to coincide with the highest rising of the Pleiades at midnight.

To the naked eye, the Seven Sisters look more like six, although the keen-eyed have reported seeing up to 13. With binoculars or a small telescope you can see dozens of sparkling bluish stars (a sign of their high temperatures) among the 200 or so. Long-exposure photographs reveal all the stars, and the soft nebulosity that surrounds the cluster.

Until recently, the nebulosity was a puzzle. Unlike the gas wreathing Orion Nebula, it could not be left-over 'natal' gas; the Pleiades are far too old for that. Research at infrared wavelengths, which examines the distribution of lukewarm gas and dust in space, has revealed that the Pleiades are ploughing into a completely unrelated gas cloud. But where did it come from?

The Pleiades themselves can shed some light. As they travel through space, the stars create a 'wake' where they have tunnelled through the gas, and this helps astronomers trace the origin of the cloud itself. At present they believe a gigantic gas cloud, located more than 1,000 light years away, is responsible. Fifteen million years ago it underwent a massive burst of star formation. Its most energetic stars quickly exploded as supernovae, scattering the relics of the original gas cloud. One clump hit the Pleiades, filling the cluster with the nebulosity that enhances its stunning appearance.

The planets

If you have never seen Mercury, now's your chance. It is an 'evening star' this February, and draws steadily away from the Sun during the second and third weeks to set an hour and a half after sunset (at 7pm) on the 24th. You will be able to spot it as a bright, untwinkling star, below and to the right of Venus, which continues to dominate the evening sky. Setting four hours after the Sun for the whole month, Venus becomes even brighter - increasing in magnitude from -4.1 to -4.5 - as it draws closer to Earth. On the 24th, the planet will be at its brightest, and situated just north of a crescent Moon.

Mars, which has been making up a striking trio with Gemini's bright twins, Castor and Pollux, is moving away from Earth and fading. Because Earth has just overtaken Mars in its orbit, the latter appears to move backwards. On the 15th, however, Mars will resume its 'direct' motion and drift back towards Castor and Pollux.

Jupiter, which rises at 9pm mid-month, is poised to become the planet for the spring. At magnitude -2.3, it is considerably brighter than Mars, although it is still low in the sky in the evenings.

Saturn passes behind the Sun ('undergoes superior conjunction') and will not be visible.

The stars

Sirius, the brightest star, stands at its highest point. It never looks as spectacular from our high northerly latitudes as it does from farther south, where it rises higher. But its low altitude, combined with its brightness, leads to some scintillating atmospheric effects.

Because of the continual shifting of Earth's atmosphere, the stars appear to twinkle: we see them through different, moving thicknesses of air. The shifting air cells, each about 50cm in diameter, act as lenses to band the starlight, too.

This refraction splits the starlight into its constituent colours, from red through blue. As a result, the brightest stars appear to flash all the colours of the rainbow when we see them low in the sky and through the greatest thickness of the atmosphere.

Diary

6 11.55pm Full Moon

9 Saturn at superior conjunction

13 2.57pm Moon at last quarter

21 1.05pm New Moon; Mercury at greatest elongation

(Graphic omitted)

Suggested Topics
PROMOTED VIDEO
Arts and Entertainment
Christian Grey cradles Ana in the Fifty Shades of Grey film
filmFifty Shades of Grey trailer provokes moral outrage in US
Life and Style
The veteran poverty campaigner Sir Bob Geldof issues a stark challenge to emerging economies at the Melbourne HIV/Aids conference
health
Arts and Entertainment
Benedict Cumberbatch and John Malkovich talk Penguins of Madagascar at Comic-Con
comic-con 2014Cumberbatch fans banned from asking about Sherlock at Comic-Con
Arts and Entertainment
Chris Pratt stars in Guardians of the Galaxy
filmGuardians Of The Galaxy should have taken itself a bit more seriously, writes Geoffrey Macnab
News
Sir Chris Hoy won six Olympic golds - in which four events?
news
Life and Style
People may feel that they're procrastinating by watching TV in the evening
life
News
ebookA unique anthology of reporting and analysis of a crucial period of history
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Trainee Recruitment Consultants - Banking & Finance

£20000 - £25000 per annum + OTE £40,000: SThree: SThree Group have been well e...

Graduate Recruitment Resourcers - Banking Technologies

£18000 - £25000 per annum + OTE £40,000: SThree: Huxley Associates are looking...

Implementation Engineer

£150 - £200 per day: Orgtel: Implementation Engineer Hampshire / London (Gre...

Trainee Recruitment Consultant - Pharmacuetical

£20000 - £25000 per annum + OTE £40,000: SThree: Real Staffing, one of the UK'...

Day In a Page

Backhanders, bribery and abuses of power have soared in China as economy surges

Bribery and abuses of power soar in China

The bribery is fuelled by the surge in China's economy but the rules of corruption are subtle and unspoken, finds Evan Osnos, as he learns the dark arts from a master
Commonwealth Games 2014: Highland terriers stole the show at the opening ceremony

Highland terriers steal the show at opening ceremony

Gillian Orr explores why a dog loved by film stars and presidents is finally having its day
German art world rocked as artists use renowned fat sculpture to distil schnapps

Brewing the fat from artwork angers widow of sculptor

Part of Joseph Beuys' 1982 sculpture 'Fettecke' used to distil schnapps
BBC's The Secret History of Our Streets reveals a fascinating window into Britain's past

BBC takes viewers back down memory lane

The Secret History of Our Streets, which returns with three films looking at Scottish streets, is the inverse of Benefits Street - delivering warmth instead of cynicism
Joe, film review: Nicolas Cage delivers an astonishing performance in low budget drama

Nicolas Cage shines in low-budget drama Joe

Cage plays an ex-con in David Gordon Green's independent drama, which has been adapted from a novel by Larry Brown
How to make your own gourmet ice lollies, granitas, slushy cocktails and frozen yoghurt

Make your own ice lollies and frozen yoghurt

Think outside the cool box for this summer's tempting frozen treats
Ford Fiesta is UK's most popular car of all-time, with sales topping 4.1 million since 1976

Fiesta is UK's most popular car of all-time

Sales have topped 4.1 million since 1976. To celebrate this milestone, four Independent writers recall their Fiestas with pride
10 best reed diffusers

Heaven scent: 10 best reed diffusers

Keep your rooms smelling summery and fresh with one of these subtle but distinctive home fragrances that’ll last you months
Commonwealth Games 2014: Female boxers set to compete for first time

Female boxers set to compete at Commonwealth Games for first time

There’s no favourites and with no headguards anything could happen
Five things we’ve learned so far about Manchester United under Louis van Gaal

Five things we’ve learned so far about United under Van Gaal

It’s impossible to avoid the impression that the Dutch manager is playing to the gallery a little
Screwing your way to the top? Good for Lana Del Rey for helping kill that myth

Screwing your way to the top?

Good for Lana Del Rey for helping kill that myth, says Grace Dent
Will the young Britons fighting in Syria be allowed to return home and resume their lives?

Will Britons fighting in Syria be able to resume their lives?

Tony Blair's Terrorism Act 2006 has made it an offence to take part in military action abroad with a "political, ideological, religious or racial motive"
Beyoncé poses as Rosie the Riveter, the wartime poster girl who became a feminist pin-up

Beyoncé poses as Rosie the Riveter

The wartime poster girl became the ultimate American symbol of female empowerment
The quest to find the perfect pair of earphones: Are custom, 3D printed earbuds the solution?

The quest to find the perfect pair of earphones

Earphones don't fit properly, offer mediocre audio quality and can even be painful. So the quest to design the perfect pair is music to Seth Stevenson's ears
US Army's shooting star: Lt-Col Steven Cole is the man Hollywood calls when it wants to borrow a tank or check a military uniform

Meet the US Army's shooting star

Lt-Col Steven Cole is the man Hollywood calls when it wants to borrow a tank or check a military uniform