Asteroid (1566) 1949 MA Icarus passed by the Earth at a distance of 8 054 000 km (20.9 times the average distance between the Earth and the Moon, or 5.38 % of the average distance between the Earth and the Sun), slightly before 3.40 pm GMT on Tuesday 16 June 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. (1566) 1949 MA Icarus has known diameter of 1.276 km, and an object of this size would pass through the atmosphere and directly impact the ground with a force of about 55 000 megatons (about 3 230 000 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater about 15 kilometers across, and resulting in global climatic problems that could last for decades or even centuries.
Image of (1566) 1949 MA Icarus on 15 June 2015 from Ceccano in Italy. The asteroid is the point in the center of the picture. The longer lines are stars, their elongation being caused by the telescope tracking the asteroid over the length of the exposure, in this case 60 seconds. Gianluca Masi/Virtual Telescope.
(1566) 1949 MA Icarus was discovered on 27 June 1949 by astronomer Walter Baade at the Palomar Observatory in California, and was given the name 'Icarus' by its discoverer in reference to the figure in Greek mythology who made wax and feather wings to escape from an island prison, but flew to close to the Sun and was burned; at the time of its discovery Icarus passed closer to the Sun than any other known asteroid, a status that lasted till the discovery of (3200) 1983 TB Phaethon in 1983 (the discoverers of Asteroids have the right to give them a proper name of their own choosing, though in the twenty-first century, with large scale astronomical surveys discovering hundreds of asteroids each week, this right is seldom exercised). The designation 1949 MA indicates that it was the first asteroid (asteroid A) discovered in the second half of June 1949 (period 1949 M), while the numeral 1566 indicates that it was the 1566th asteroid ever discovered; asteroids are not given this numeric designation immediately, to avoid false or double sightings being given numbers, but rather wait until the existence of the body has been confirmed by multiple observations.
The calculated orbit of (1566) 1949 MA Icarus. JPL Small Body Database.
(1566) 1949 MA Icarus has a 409 day orbital period and an eccentric orbit tilted at an angle of 22.8° to the plane of the Solar System, which takes it from 0.19 AU from the Sun (i.e. 19% of the average distance at which the Earth orbits the Sun, and less than half the average distance between Mercury and the Sun) to 1.97 AU from the Sun (i.e. 197% of the average distance at which the Earth orbits the Sun, and considerably outside the orbit of the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in August 2009 this year and the next predicted in September 2019. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (1566) 1949 MA Icarus is also classified as a Potentially Hazardous Asteroid. (1566) 1949 MA Icarus also has frequent close encounters with the planets Mercury (which it last came close to in May 1987 and is predicted to pass again in May 2025), Venus (which it last came close to in September 1989 and is predicted to pass again in April 2033) and Mars (which it last came close to in June 1986 and is predicted to pass again in November 2074). Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.
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