The Pleiades and Orion’s Return

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The Seven Sisters

The lovely Pleiades star cluster (Seven Sisters) is becoming a viable late night stargazing target for observers in northern Europe again.  Look up in the East after 11pm to see the distinct jewel like arrangement of stars.  Note the red supergiant Aldebaran (Abarbic for “The Follower”) trailing just behind and to the left.  Pick out a pair of binoculars to see the Pleiades at their best – telescopes reduce the field of view too much for objects like this.

The Pleiades is an excellent example of an open cluster.  These are relatively younger energetic stars still in close proximity to their siblings having all emerged from the same region of intestellar dust and gas.  Eventually these stars will move apart and join the general distribution of more widely dispersed stars.

If you’re awake after that, the hunter Orion will begin rising from the East around 1am. Grab your binos again and marvel at the star forming emmission nebula below the main three stars in the belt.  This is an active star forming region over 1000 light years away, where new stars are being born from dense clouds of hydrogen.  Train a telescope at moderate magnification on the Orion nebula and you’ll be blow away by the majesty of the extended dust clouds, energised and glowing due to the nearby influence of young hot stars.

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The Orion Nebula

Planet wise, Neptune and Uranus can be observed almost all evening after darkness, but you’ll need a reasonably powerful telescope to resolve them as tiny blue-green disks.

All the best and clear skies!

Elsilon Lyrae

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Epsilon Lyrae is a nice easy double star you can view in binoculars all year round in northern latitudes. It sits high in the southern sky very close to the bright star Vega, so is relatively easy to find.

Viewed with the naked eye, it’s just a normal looking 5th magnitude star, but point some binoculars at it and it splits into two clearly separated stars. Things get even more interesting if you train a telescope on the pair, as they’ll split again, revealing a pair of double stars!

The main pair are gravitationally bound and orbit each other every 1200 years with a separation of 160AU (or 160 times the distance from Earth to our Sun). The system is approximately 170 light years away.

Double star systems are the norm in our galaxy with over 60% of star systems containing double or multiple stars orbiting each other at various distances. Our Sun, so far as we know, is a lone wanderer.

Simulations of quadruple star systems suggest they’re relatively unstable, and easily disturbed from their rotating reels by the passing tug of galactic neighbours.

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Neptune at Opposition

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Neptune reaches opposition on September 2nd meaning it’s at its closest approach to Earth over the next while. It’s up almost all night in the southern sky within the constellation Aquarius, below and right of Pegasus.

You’ll need a good horizon to see it however as it’s very low on the horizon this far north, never getting higher than 27 degrees.

During opposition Neptune will be at a distance of 28.94 AU with a disk size of 2.4 arcsec. In a good telescope of 6 inches or more you should be able to see a tiny blue disk and perhaps its companion Triton.

Neptune was first observed in a telescope in 1846.  It’s existence was implied from solar system models rather than from direct observation.  Like Saturn and Jupiter, it’s a gas giant with an atmosphere largely composed of hydrogen and helium, but this far out it also contains some “ices” such as water, ammonia, and methane.  

Neptune also has some of the weirdest and wildest weather in the solar system, with recorded wind speeds as high as 2,100 kilometres per hour!  This is what drives some of the mesmerising cloud streaking witnessed during Voyager 2’s flyby.  It’s also an extremely cold place – its cloud tops have recorded temperatures as low as -220 C.  Not surprising given how far it is from the sun.

The Andromeda Galaxy

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Why not try looking at another galaxy? M31, our nearest companion galaxy, is well placed in northern skies, sitting in the East between the W shape of Cassiopeia and the great square of Pegasus.

Under dark skies and away from significant street lighting, you might just be able to see an oval smudge unaided, but pull up a good pair of binoculars and you’ll see much more. A definite central core and perhaps suggestions of surrounding gas and dust lanes.

Although fuzzy and indistinct the appeal of viewing an object like this is the sheer enormity of the distances and time involved. Andromeda is over 2.5 million light years away, and home to billions and billions of stars and companion worlds.

To find it follow the chart below. From the star Mirak in the constellation Andromeda, simply follow a line upwards in the direction of Cassiopeia. As you sweep this area of the sky in binoculars a bright fuzzy patch should glide into view – that’s M31.

Andromeda_galaxy_via_Cassiopeia

Spotting it for the first time can be tricky, so don’t get too frustrated. It might take you a few attempts over several nights.

 

Astronomical darkness and the northern gem ‘Vega’

We’re finally emerging into some periods of significant darkness in the north of Scotland. Tonight marks approximately 1.5 hours of true astronomical darkness at latitudes 57 degrees north.

Astronomical darkness is defined as the sun being more than 18 degrees below the horizon, which it will tonight between 12.30am and 2.13am. Notwithstanding the waning crescent moon rising after midnight, conditions should be pretty good for general observing. Local weather reports indicate clear skies from about 7pm too.

Star profile: Vega (Arabic for “the swooping Eagle”)

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Vega sits above the little diamond of starts in Lyra

After midnight look south west and directly up, almost towards the zenith. The bright blue-white gem you might see shining above will be Vega – the 5th brightest star in northern skies. Vega sits above a lovely little diamond shaped constellation comprised of four moderately bright stars (within the constellation Lyra).

Vega has been studied comprehensively by astronomers and has some unusual properties. One is its incredibly rapid rotation which causes its mid drifts to bulge out fantastically, yielding very large equitorial radius measurements. If Vega rotated only another 7% faster its would rip itself apart due to incredible centrifugal forces.

Vega is also big and young as far as stars go – with a mass of 2.3 Suns and 37 times more bright. Because of its size and energy Vega won’t survive as long as our Sun and will remain in a stable state for only a fraction as long as our home star (perhaps 500 million years).

The rule of the Cosmos as far as stars are concerned appears to be “burn bright and die young…”