Early risers in the British Isles blessed with clear skies will see naked-eye star lambda (λ) Geminorum, otherwise known as Kebash or Alkibash (α=7h18.1m δ=+16°32′ J2000), slip behind the 92% illuminated waning gibbous Moon close to 6 am on Tuesday, 9th December. The occultation will take place some 33° above the west-southwest horizon in a dark sky for the centre of the country. The disappearance of magnitude-3.6 λ Geminorum occurs close to 6:01 am on 9th December for mid-UK observers. This computer simulation shows a powerful binocular view with north up and east to the left. Image credit: Ade Ashford/SKy Safari ProAlthough λ Geminorum is normally an easy naked-eye star, the proximity of a dazzling Moon will mean that powerful binoculars or a small telescope will be required, especially since the star’s disappearance will occur at the Moon’s bright limb. For telescope users, what’s noteworthy about an occultation of Alkibash is that it’s a 9.6-arcsecond double star; the westernmost component will disappear first, closely followed by the companion star.
For an observer in the heart of the British Isles, the star is occulted by the Moon close to 6:01 am in a dark sky. As a rule of thumb, the further west you live, the earlier the event will occur, and vice versa to the east. So, be prepared with your telescope and sitting at the eyepiece about 10 minutes before the event to watch the approaching limb of the Moon. Twilight is starting to brighten the sky in readiness for the reappearance of λ Geminorum (Alkibash) close to 6:56 am for an observer in the central British Isles. The star flashes into view at the Moon’s dark limb just north of the prominent circular Mare Crisium. Image credit: Ade Ashford/Sky Safari ProThe reappearance of a star from occultation is somewhat harder to prepare for as you don’t know precisely when it will happen! For the mid-British Isles this will occur close to 6:56 am. As before, the further west you live, the earlier reappearance will occur, and vice versa to the east. Be prepared at least ten minutes beforehand and study the graphic to familiarise yourself with the lunar features and orientation. (Note: users of refractors or catadioptrics with a star diagonal will need to mentally flip the chart left-right, whereas Newtonian users should rotate the view 180°.)
Fortunately, we can take advantage of the fact that Alkibash is a double star, extending what would normally be a virtually instantaneous reapparance into one lasting a second or two for both stars. This occurs at the Moon’s dark limb just north of the prominent Mare Crisium. Bear in mind that twilight will be lightening the sky and the Moon will be about 25° above the western horizon. Clear skies and good luck!
For the first time, astroarchaeologists have statistically proven that the earliest standing stone monuments of Britain — the great circles — were constructed specifically in line with the movements of the Sun and Moon, 5000 years ago. University of Adelaide researchers used innovative 2-D and 3-D technology to test the patterns of alignment in the standing stones.
From the most powerful telescope orbiting Mars comes a new view of Earth and its moon, showing continent-size detail on the planet and the relative size of the Moon.
Phenomenally durable crystals called zircons are used to date some of the earliest and most dramatic cataclysms of the solar system, such as the late heavy bombardment that created hellish surface conditions on the young Earth and Moon about 4 billion years ago. Now a study of zircons from a gigantic meteorite impact in South Africa casts doubt on the methods used to date lunar impacts.
