On April 19, 2017 the orbit of 1 km wide asteroid 2014 JO25 will pass 4.6 LD ( 1,768,239 km ) from Earth. In astronomical terms anything within 100 LD is considered a PHA (Potentially Hazardous Asteroid ) 1 LD = distance from Earth to the Moon ( 384,400 km ). Stacked against vastness of the cosmos, 4.6 LD miss by a behemoth projectile amounts to humanity winning the lottery.
2014 JO25 will pass without consequence, no harm no foul. From NASA –
“There are no known future encounters by 2014 JO25 as close as the one in 2017 through 2500. It will be among the strongest asteroid radar targets of the year. The 2017 flyby is the closest by an asteroid at least this large since the encounter by 4179 Toutatis at four lunar distances in September 2004. The next known flyby by an object with a comparable or larger diameter will occur when 800-m-diameter asteroid 1999 AN10 approaches within one lunar distance in August 2027.”
From Earthsky –
“For backyard observers, the exciting news is that asteroid 2014 JO25 might be be visible moving across the stars though 8″-diameter and bigger telescopes. Can it be seen with smaller telescopes? Maybe, but in order to be able to detect its motion across the stars, at least an 8″ scope will be required. The asteroid will not be visible to the unaided eye, as it may show a brightness or magnitude between 10 and 11.
The asteroid is currently located in the direction of the sun, but – during the first hours of April 19 – the space rock will come into view for telescopes as it crosses the constellation of Draco. Then, during the night of April 19, asteroid 2014 JO25 will seem to move across the skies covering the distance equivalent to the moon’s diameter in about 18 minutes.
The asteroid will be close to star 41 Comae, which is very close to Beta Comae. This star is magnitude 4 and thus visible to the unaided eye. Illustration by Eddie Irizarry using Stellarium.
That’s fast enough for its motion to be detected though an amateur telescope. The best strategy to catch the space rock in your telescope is to observe a star known to be in the asteroid’s path, and wait for it.
If you are looking at the correct time and direction, the asteroid will appear as a very slowly moving “star.” Although its distance from us will make the space rock appear to move slowly, it is in fact traveling though space at a speed of 75,072 mph (120,816 km/h)!
Because it will appear to move very slowly, observers should take a good look at a reference star for a few minutes (not seconds) to detect the moving object.
Although asteroid 2014 JO25 will be closest to Earth on the morning of Wednesday, April 19, 2017, (around 7:24 a.m. Central Time / 12:24 UTC) the space rock may look a bit brighter (but still only visible in telescopes) during the night of April 19, because the asteroid will be at a higher elevation in our skies.”