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.”
Owls may be scarce near your favourite viewing spot, but the Northern Hemisphere spring sky contains one celestial owl that you can track down in small telescopes – Messier 97 (NGC 3587). Commonly called the Owl Nebula, M97 is a planetary nebula discovered by Pierre Méchain in 1781 that is currently ideally placed for observation almost overhead at nightfall in the constellation of Ursa Major, the Great Bear.
Astronomers have uncovered evidence for a vast collection of young galaxies 12 billion light years away. The newly discovered “proto-cluster” of galaxies, observed when the universe was only 1.7 billion years old (12 percent of its present age), is one of the most massive structures known at that distance.
Markarian 820, also known as Mrk 820, LEDA 52404 or IRAS F14379+3142, is a lenticular galaxy in the constellation Boötes, about 300 million light-years from Earth. Galaxies like this one are in the transition zone between ellipticals and spirals and lie right where the fork divides in American astronomer Edwin Hubble’s classification scheme of galaxies from 1926.