Before the waxing crescent Moon of the next lunation gets too bright, Northern Hemisphere observers get the chance to track a relatively bright and recently discovered Amor-type asteroid that passes just 0.02037 astronomical units (1.893 million miles, or 7.93 lunar distances) from Earth at 15:43 UT (4:43pm BST) on Monday 29 May 2017.
Believed to be between 350 metres and 780 metres in diameter and orbiting the Sun every 4.21 years, near-Earth asteroid 2017 CS was discovered by Pan-STARRS 1 on 2 February 2017. Photometric results indicate a rotation period of about 40⅓ hours with a lightcurve amplitude of 0.18.Given its size and proximity, 2017 CS could attain magnitude +13.5 at closest approach if the predictions tabulated at the bottom of this page hold true. This means that the asteroid is a viable target for 6-inch (15-cm) and larger telescopes as it moves against the background stars at a rate equivalent to the apparent width of the full Moon every hour.Astronomical twilight now lasts all night for observers in the British Isles, except for those in the southernmost counties of England, so the darkest skies are found between midnight and 2am BST. The light of the waxing cresent Moon will also start to interfere from 31 May.
For observers in Western Europe, the following four detailed finder charts for successive nights around the time of closest approach should help you track down this fascinating small world.
Chart 1: 29 May — covering 11pm BST on 28 May to 3am BST on 29 May
Chart 2: 30 May — covering 11pm BST on 29 May to 3am BST on 30 May
Chart 3: 31 May — covering 11pm BST on 30 May to 3am BST on 31 May
Chart 4: 1 June — covering 11pm BST on 31 May to 3am BST on 1 June
Astronomers at Goldstone (and possibly Arecibo) plan to make radar observations of 2017 CS in late May that could yield a surface resolution of 3¾ metres if the signal-to-noise ratios are strong enough.
If you miss 2017 CS this time around, its next close encounter with Earth occurs on 17 May 2038 when the asteroid passes 0.0249 astronomical units, or 2.3 million miles (9.7 lunar distances) from our planet.
The Minor Planet Center classifies 2017 CS as a “Potentially Hazardous Asteroid.”
At 6:42am BST on Thursday, 12 October our best orbit prediction for a 20-metre-wide space rock designated 2012 TC4 indicates that it will hurtle by Earth just 43,800 kilometres (27,215 miles) above the ocean between Australia and Antarctica. If UK skies are clear on 11 October and you have an 8-inch or larger telescope, you might just see it too.
A small, recently discovered asteroid — or perhaps a comet — appears to have originated from outside the Solar System, coming from somewhere else in our galaxy. If so, it would be the first “interstellar object” to be observed and confirmed by astronomers.
NASA has formalised its ongoing program for detecting and tracking near-Earth objects (NEOs) as the Planetary Defense Coordination Office (PDCO). The office will be responsible for supervision of all NASA-funded projects to find and characterise asteroids and comets that pass near Earth. It will also take a leading role in coordinating efforts in response to any potential impact threats.