Exoplanet Excursions: July 2015

Jon contends with the clouds as he journeys to a Titanic gas giant in Centaurus.

On 20 March I left my spaceship, the Perihelion, in the garage and boarded an ocean-going vessel, MS Boudicca, to see the total eclipse of the Sun from the surface of planet Earth. But as the morning began under leaden skies with stinging wind and sleet, I couldn’t help feeling that I’d chosen the wrong craft.

A
a
-
Image Credit: 
Mark Garlick
Credit: Illustration by Mark Garlick

Thankfully, the collaboration of Pete Lawrence and Captain Lars Kjeldsen, who meticulously pooled their knowledge, guided us to clear skies at precisely the right moment.

We viewed the partial phases through stubborn, narrow cloud breaks resembling cracks in dried mud flats. It felt like we were fighting a toe-to-toe war of attrition with awkward clouds, reluctant to allow more than fleeting glimpses to be seen. Nerve-shreddingly exhausting as this was, it was worth every fragment of anxious hope when the clouds parted, allowing the majesty of totality to be seen. It felt like a miracle.

Enthused by the experience, I’m setting off to view far more distant objects through tantalising gaps in the cloud formations wrapped around exoplanetary worlds. There’s a good chance of witnessing just such an evocative scene in Centaurus, around the star HD 113538, a sub red dwarf 65 per cent the mass of the Sun and 51 lightyears from Earth. Two confirmed planets orbit this star, with the tidy names HD 113538 b and HD 113538 c. I’m taking the Perihelion to the farthest of these, planet ‘c’ on the edge of the habitable zone.

HD 113538 c is a gas giant around 70 per cent the mass of Jupiter, orbited by numerous moons. As the planet is so Saturnesque I’m going to choose the satellite that is most Titanesque as our place to view the planetary neighbourhood. Evocative of our battle to glimpse as much of the eclipse through a barrel roll of uncooperative clouds, there’s a similar situation here on the surface of this moon. Noxious clouds with patchy backlit regions loop and whirl across the alien sky, drawing a veil over the world. Hanging there like the bronze-coloured cigarette fog in a 1960s jazz club, these clouds create a tantalising sense of anticipation as I wonder what might end up being revealed.

Suddenly a family of five moons, all in a crescent phase, break through. Their sizes reduce like satellite Russian dolls. Through a suddenly thinning blanket of cloud there’s a breathtaking view of the parent planet, HD 113538 c. It glows with the same crescent as the moons, occupying the sky like a planetary mother duck with her ducklings close by.

Then the most staggering feature of all snaps into view. This moon’s very own ring system is revealed. A stark set of parallel lines like four silvered racetrack lanes slice upwards and loop back down after reaching their peak. There’s surely no more astonishing way to view a ring system than from the surface of the object they surround. Seeing the rings backlit after the star sets is going to be a most ethereal sight. I’m grateful that the clouds are parting and the view of these remarkable objects won’t be squandered all at once.


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

This column originally appeared in the June 2015 issue of BBC Sky at Night Magazine.

Like this article? Why not:
Astrophotography With A Smartphone: Timelapses
previous feature Article
How to star test a telescope
next feature Article
We use cookies to improve your experience of our website. Cookies perform functions like recognising you each time you visit and delivering advertising messages that are relevant to you. Read more here