Now that the Moon is a waning crescent rising after midnight, observers in the British Isles can take advantage of at least three hours of darkness from 9pm BST to track down Comet Africano (C/2018 W2) at its closest and brightest as it speeds through the constellations of Pegasus, Pisces and Aquarius.
At 10:56 UT on 27 September, C/2018 W2 (Africano) passes just 0.494 astronomical units, or 74 million kilometres (46 million miles) from Earth. At this time the comet is moving against the stars of Pegasus at a rate of 3⅔ degrees per day, equivalent to the width of the full Moon every 3¼ hours.
Discovered almost simultaneously on 27 November 2018 by B. M. Africano with the Mount Lemmon 1.5-metre reflector and H. Groeller with the Catalina Sky Survey’s 0.68-metre Schmidt telescope (Africano’s report was submitted just 21 minutes earlier), C/2018 W2’s integrated magnitude is currently about +9 and may peak at about +8.5 over the coming week. Note that Comet Africano lies within a binocular field of view of outermost planet Neptune on the night of 3–4 October.
Having passed perihelion (closest point to the Sun) on 5 September, don’t miss any opportunities to view C/2018 W2 because it’s visiting the inner planets on a hyperbolic trajectory, meaning that it will never return to the Sun – unless its orbit is perturbed by the gravitational influence of a body in the outer Solar System in the distant future.
More than 100 confirmed exoplanets — the biggest haul of worlds uncovered by the stabilised and repurposed Kepler space telescope in its K2 mission — is reported by an international science team led by the University of Arizona. Excitingly, the new population includes many worlds that could be rocky and cool enough to potentially support life.
Mercury is poised to put on a fine evening show for Northern Hemisphere observers at dusk, attaining a greatest elongation 18.2 degrees east of the Sun on Monday, 10 February 2020. For ten evenings starting 3 February, the innermost planet and its brightest sibling, Venus, maintain an almost constant angular separation low in the west-southwest 40 minutes after UK sunset.
As shooting-star devotees prepare for the naked-eye spectacle of the Geminid meteor shower in mid-December, owners of small telescopes can also witness the close passage of the meteors’ parent body — a curious “rock comet” known as 3200 Phaethon, galloping through the constellations of Auriga, Perseus, Andromeda, Pisces and Pegasus at a rate of up to 15 degrees/day.