You could be forgiven for thinking that we’re currently in the midst of a swarm of near-Earth asteroids. Since the start of this year, at least a dozen of these space rocks have already whizzed by our planet closer than the Moon. That’s in our backyard astronomically speaking, but not near enough to get worried about. None of these newly-discovered objects poses an immediate threat to Earth, their large number and frequency merely the result of better detection methods.
But if you wish to see a particularly close approach from one of these asteroids, you only have to wait until Friday, 9 February at 22:27 UT (10:27pm GMT) when 2018 CB passes just 0.000466 astronomical units from Earth, or slightly less than one-fifth of the Moon’s distance – that’s a mere 69,700 kilometres (43,300 miles), or twice the distance of our belt of geosynchronous communication satellites.
Apollo-class asteroid 2018 CB was only discovered by the Catalina Sky Survey on 4 February. Believed to be 20 to 40 metres in size, it orbits the Sun every 611 days. Looking ahead somewhat, this asteroid passes even closer to the Moon (0.000196 astronomical units, or 29,400 kilometres) at 3h UT on 8 February 2090.
Observing highlights for the UK on 9 February
At 19:12 UT (7:12pm GMT), the asteroid passes just 15 arcminutes (one-quarter degree) southeast of magnitude +3 double star delta (δ) Persei when 2018 CB is moving against the background stars at a rate equivalent to the width of a full Moon every three minutes. At this time the star and asteroid are virtually overhead as darkness falls as seen from the heart of the British Isles. If you have an 8-inch (20-cm) or larger telescope with δ Persei centred in an eyepiece magnifying 50x or less between 7:10 and 7:15pm GMT, you’re likely to see 2018 CB’s motion realtime if the predicted magnitude of +12.7 holds true.At 20:10 UT (8:10pm GMT), 2018 CB passes 1⅔ degrees southeast of open cluster Messier 34 when the apparent motion of the asteroid against the background stars of Perseus has increased to almost 15 degrees/hour, or the apparent width of a full Moon every two minutes!
Shortly before 8:35pm GMT finds 2018 CB crossing the constellation border into Triangulum where the asteroid passes ⅓ degree northwest of magnitude +3 binary star beta (β) Trianguli at 20:45 UT (8:45pm GMT). If the magnitude predictions hold true, this is another opportunity to see a conspicuous star and 2018 CB in the same field of view of 8-inch telescopes and larger at a magnification around 100x.
Finally, 2018 CB passes 1.9 degrees southeast of magnitude +5.7 Local Group galaxy Messier 33 at 9:12pm GMT (21:12 UT). By this time the asteroid’s motion against the background stars of Triangulum has increased to a whopping 20 degrees/hour, a rate equivalent to the width of a full Moon every 1½ minutes.