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.
Like buses, you can wait ages for a near-Earth asteroid – then two come along in quick succession. This weekend you also have the opportunity to view a 70-metre-wide space rock known as 2018 RC in backyard telescopes of 6-inch (15-cm) aperture and larger as its hurtles past Earth closer than the Moon.
An international team of scientists has solved an age-old scientific riddle by discovering that planetary rings, such as those orbiting Saturn, have a universally similar particle distribution. The study also suggests that Saturn’s rings are essentially in a steady state that does not depend on their history.
In the race towards the discovery of Planet Nine, scientists from around the world strive to calculate its orbit using the tracks left by the small bodies that move well beyond Neptune. Now, astronomers from Spain and Cambridge University have confirmed that the orbits of the six extreme trans-Neptunian objects that served as a reference to announce the existence of Planet Nine are not as stable as originally thought.