This looping animation represents a computer simulation of the occultation of magnitude +3.6 double star lambda (λ) Geminorum as seen from Edinburgh on the morning of Sunday, 29 November 2015. From the Scottish capital, the star — also known by its proper name of Alkibash — disappears at the southern lunar limb just before 4:58am GMT and reappears by 5:21am GMT. As described in the text, this event is visible as a grazing lunar occultation further south in the British Isles. AN animation by Ade Ashford.Early risers in the northeast of England and Scotland blessed with clear skies will see naked-eye star lambda (λ) Geminorum, otherwise known as Alkibash (α=07h18.1m δ=+16°32′ J2000), slip behind the southern polar regions of an 18-day-old waning gibbous Moon close to 5am GMT on Sunday, 29 November. The occultation will take place some 40 degrees above the southwest horizon in a dark sky for the north of the UK.
If one is situated exactly on the graze line, the telescopic view of a moderately bright star winking in and out of sight as it is alternately hidden by mountains on the southern limb of the Moon then exposed again as it shines through a lunar valley affords an awesome demonstration of the orbital motion of the Moon. If a star happens to be a double — as lambda (λ) Geminorum is — the spectacle is enhanced as you have two points of light flickering on and off!
The grazing occultation time and line is predicted to run through south Campbeltown (5:07am), Galloway Forest Park (5:09am), Penrith (5:12am), Thirsk (5:14am) and Driffield (5:16am; all times GMT).
For some large centres of population north of the graze line, the full occultation disappearance (D) and reappearance (R) times for the star are: Glasgow (D 4:59am, R 5:18am); Edinburgh (D 4:57am, R 5:20am); Berwick-upon-Tweed (D 4:59am, R 5:23am); Newcastle upon Tyne (D 5:04am, R 5:21am); Stockton-on-Tees (D 5:07am, R 5:19am) and Scarborough (D 5:09am, R 5:20am).
As always, with any sort of occultation observation, ensure that you are setup and viewing a few minutes before the predicted time(s) so as not to miss anything. Clear skies!
Inside the magazine
You can find out more about this month’s lunar and stellar events in the November edition of Astronomy Now in addition to a full guide to the night sky.
As dusk fades to dark on Sunday, 17 April, observers in the British Isles should look up to the southern sky to see the 10-day-old waxing gibbous Moon and Jupiter just four degrees apart, within the same binocular field of view. Jupiter’s largest moon, Ganymede, and second Galilean moon, Europa, provide some events for telescope owners to view at higher magnifications.
Now two months past opposition, the solar system’s largest planet, Jupiter, is highest in the UK sky before sunset and is already descending in the southwest by the time the sky is dark enough to observe it. However, there is still phenomena of the Galilean moons to see and the planet’s Great Red Spot, so make the most of your Jovian observations while you can during May.
Tiny beads of volcanic glass found on the lunar surface during the Apollo missions are a sign that fire fountain eruptions took place on the Moon’s surface. Now, scientists have identified the volatile gas that drove those eruptions. If volatile reservoirs on the Earth and Moon do indeed share a common source, it has implications for understanding the Moon’s origin.
