Exoplanet Excursions: June 2014

Holy hot Jupiters Batman – it’s a multiple planetary system around a main-sequence star.

My excursions tend to evoke one of two moods in me: a fascination with violent extremes or a thirst to see peaceful alien vistas of breathtaking beauty.

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Credit: Illustration by Mark Garlick

I’m on my way to a destination that will cause both this time. Within the constellation of Andromeda lies the binary star system Upsilon Andromedae. It was while looking up at the system’s bright main star – Upsilon Andromedae A – with the naked eye back on Earth that I got the inspiration for this latest voyage. This white, F-class star is younger than our Sun and shines with a magnitude of +4.1.

The Upsilon Andromedae planetary system was discovered in 1996 by Marcy and Butler. They may sound like detective rivals of Cagney and Lacey, or makers of scented candles, but their discovery was the first multiple planetary system around a main-sequence star ever found by the human race. As of 2010, four worlds have been uncovered around this star.

The first planet, Upsilon Andromedae b, is one of the so called ‘hot Jupiters’, orbiting closer to its star than Mercury does to ours; in fact it takes just four days to whip around Upsilon Andromedae A. I remember Dr Alan Fitzsimmons talking about these on the 700th episode of The Sky at Night, and how they end up so close to their star due to some kind of planetary migration. Up until then I’d thought that ‘hot Jupiter’ was something Adam West’s Batman might have said.

Next planet out is Upsilon Andromedae c. It has a very peculiar orbit, probably caused by the gravity of its neighbour, gas giant Upsilon Andromedae d. I’ve set a course to one of the plethora of moons orbiting this third planet, which is within the star’s habitable zone, where I will absorb the spectacular sights of this diverse and busy system.

Soon after landing there’s a chance to behold a view that has always been my ambition to witness. An almighty gas giant – complete with awesome ring system – ascends dramatically above the alien horizon. As Upsilon Andromedae d rises it practically fills the sky, a sky that has a marvellously alien greenish hue, part way between the aqua of the Caribbean Sea and a bottle of pine fresh cleaner.

This colossal planet has Jupiter-style bands looping and swirling into one another with interlocked intensity, as if they’d been knitted. The silence here on the moon belies the hurricane force violence that must be playing out within the giant’s cloud decks.

These bands remind me of stripes of interference that would dart across the screens of early colour televisions, but coloured burnt ochre orange and laced with graphite black, luminescent white and lighter salmon shades associated with Mars. It’s the colouring of a tiger swathed across the entire disc of the gas giant, while the ring system glows a silvery white, with the stark clarity of snow-capped Himalayan peaks.

The ambient light cast onto the surface of this moon has a peachy crimson glow, a darker version of shades seen on Earth before a thunderstorm. It’s a truly incredible collective view: the ferocious gas giant and its neighbouring planets, the ice blue and iridescent orange of the two stars, and the scattering of innumerable Moons travelling their orbits. Surely a vision you could never tire of.


Jon Culshaw is a comedian, impressionist and guest on The Sky at Night

This column appeared in the June 2014 issue of BBC Sky at Night Magazine

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