Science

The Sky Above You: October 2022

By Duncan Lunan

The Moon will be Full on October 9th, and New on October 25th, when there will be a partial solar eclipse between 10 a.m. and 11.45 a.m., with 30% of the Sun obscured as seen from Scotland.  As always, use caution in looking at the Sun, do not stare at it and above all, don’t look at it directly with any optical instrument.  British Summer Time ends this year on October 30th.

After last month’s optimistic news items, NASA’s Moon programme is encountering setbacks.  Launch of Artemis 1, the biggest rocket ever, had to be postponed due to a fuel leak and that has been contained, rather than eliminated.  The rocket will have to pass a further fuelling test before launch.  A further issue was that repeated waivers had to be issued, otherwise it would have had to be withdrawn from the pad for inspection and recharging of crucial batteries in the emergency destruct system, which have a limited lifetime – they’re not supposed to be out on the pad for weeks on end.  Hurricane Ian has forced the issue by requiring the rocket to be rolled back in any case, and the launch of SpaceX Crew 5 to the International Space Station has likewise had to be postponed.

The CAPSTONE probe, on a slow path to the Moon, suffered an ‘anomaly’ and went into a tumble at the end of its latest rocket burn.  Controllers have re-established contact and solar power, but it remains to be seen whether full control can be regained in time for lunar arrival in November, where it’s due to test the navigational system for future manned missions.     

The planet Mercury will be in the morning sky in October, at its greatest elongation from the Sun on October 8th,  and at peak altitude the following day, becoming more visible in the following week as it briefly becomes brighter than Mars, though much nearer the horizon.  As always, beware of the Sun if looking for Mercury around dawn.  The Moon is near Mercury on October 24th.

Venus has disappeared from the morning sky by October, and is at superior conjunction on the far side of the Sun on the 22nd.  On October 25th it’s occulted by the Moon, but remains out of sight until December. 

Mars is in Taurus, between the horns of the Bull, and rises at 9.30 p.m. in October, growing ever brighter as it approaches opposition on December 8th.  Mars is near the Moon on October 15th, and on October 30th it reaches an apparent ‘stationary point’, after which it will move westward against the stars as the Earth overtakes it.

Jupiter rules the night sky meantime, after passing opposition in Pisces in the last week of September.  Jupiter sets at 5.30 a.m. as October progresses, with the Moon nearby on October 8th.  On the night of October 2nd, Jupiter’s innermost large moon Io will be directly between the Earth, Jupiter and the Sun, occulting its own shadow on the face of the planet.  That previously happened on the night of 25th/26th September, but this time the viewpoint will be different and Io will approach the shadow from the right instead of the left.  On October 26th only Callisto will be visible off the planet, with Io hidden behind it, and Ganymede and Europa with their shadows in transit across it.

Saturn in Capricornus sets at 1.30 a.m. in October, reversing direction on October 23rd as the Earth draws ahead of it.  The Moon appears nearby on October 5th.

Uranus in Aries rises at 7 a.m. in October, near the Moon on October 12th, when it will be occulted as seen from much of the USA, Canada and Scandinavia.

Neptune, between Aquarius and Pisces, sets at 4.30 a.m. in October.  Neptune appears near the Moon on October 8th.

The Orionid meteors from Halley’s Comet will peak on October 21st, unspoiled by moonlight.  As usual, more meteors can be expected after 1 a.m. BST as the Earth turns to face the oncoming dust stream.  The Taurid meteors from Encke’s Comet continue throughout October, with the Southern Taurids reaching their peak on October 10th.  They may produce more fireballs than usual because this year the Earth may encounter a denser stream of dust than usual.

NASA’s DART mission to the asteroid Didymos has been a complete success so far, impacting the moon Dimorphos after taking closeup pictures, and being tracked by the Italian Liciacube, which is already returning images of the impact and aftermath, also watched by several space telescopes and hundreds of observatories around the world.  The intention was to test the impact deflection method as a means of protecting the Earth from incoming asteroids, advocated for example by Prof. Colin McInnes of Glasgow University.  There is a serious question to resolve which I have not seen discussed in the run-up to the event.

In the discussion group which generated the material for my book Incoming Asteroid!  What Could We Do About It?, we discussed several deflection methods including solar sails, mass drivers, nuclear weapons, high-energy lasers, kinetic impactors and gravity tractors.  For all of these except the last, one big question concerned the threatening asteroid’s composition.  Space missions to the asteroids Eros and Itokawa had established that both were at least partly covered in thick blankets of fine regolith (broken rock), and it was seriously suggested that some asteroids might actually be ‘junk piles’, loose aggregations of rock particles with no coherent structure.  Microgravity experiments on ESA’s parabolic flight aircraft had suggested that with all the above methods except gravity tractor, the effect on the asteroid might be to generate a ‘rock tsunami’.  Since then, missions to the asteroids Ryugu and Bennu have suggested that both of them are rock piles, and at first sight Didymos and Dimorphos appear to be the same.  If we impart kinetic energy to such a body, or even to a regolith crust, the energy has to go somewhere – but my question is, does it move the asteroid as a whole or simply ‘shoogle’ it, rearranging the component rocks, possibly heating up the interior a bit, but making no change to the asteroid’s orbit?

Dimorphos is only the size of the Washington Monument, and if the intended deflection is successful, within a week we should see it on the other side of Didymos from where its previous orbit would have taken it.  Whether I’m right or wrong about the shoogle effect, we will know very shortly, so I’m putting the question back on record now.  Watch this space…   

Duncan Lunan’s book Incoming Asteroid!  What Could We Do About It? was published by Springer in 2013 and isavailable through Amazon or through bookshops, or from the publishers, as are his more recent fiction books, The Elements of Time, From the Moon to the Stars and The Other Side of the Interface, published in 2016, 2019 and 2021, respectively.  For details and for his other books see Duncan’s website, www.duncanlunan.com.

You can download a copy of the October Star Map here:

Categories: Science

Tagged as: , , , ,