The asteroid "Florence" that visited us last week missed our planet at a distance of 7 million kilometers. For Earth, this lump is not a threat, but it is the largest asteroid that has come so close to our planet in more than a hundred years.
The asteroid is so big that it turns out that it has two tiny moons, if you believe the images received by the NASA aerospace agency from the 31st to the 1st of September, when the "Florence" approached the Earth as close as possible.
"Despite the fact that a lot of asteroids before the" Florence "were approaching much closer to the Earth, they were all much smaller in size. "Florence" is the largest asteroid that has approached our planet since NASA launched a program to detect dangerous near-Earth objects, "commented Paul Chodas of the NASA Laboratory of Reactive Movement, the manager of the Center for Near-Earth Objects Studies).
So how big should an asteroid be for him to even have satellites? The size of "Florence" is 4.4 in diameter. Satellites themselves are much smaller – something between 100-300 meters. One of them is closer to the asteroid, the other is further away from it. The time of the orbital period of rotation of the inner satellite is about 8 hours, the outer one is something between 22 and 27 hours.
Having satellites for an asteroid is a very unusual property. In all, about 60 of the 16,400 known near-Earth objects have at least one satellite. Triple asteroids, that is, asteroids that have two moons at once, are much less common. "Florence" is only one of three known near-Earth objects, which possess this feature. The other two are the 1994 asteroid SS, which had satellites in 2009, as well as the 2001 SN263 asteroid, whose satellites were discovered in 2008.
But none of them are so close as "Florence" did not approach our planet, which was an excellent opportunity to observe such a rare visitor at a closer distance. The asteroid itself continued its movement around the Sun.
The asteroid not only "boasted" of the presence of satellites. The images obtained by NASA provided a little more information about the stone itself. It turns out that it is almost round, but has a somewhat flattened shape in the equatorial part. There is at least one large crater on the asteroid.
The American aerospace agency is going to continue to monitor "Florence" within the next few days, as the possibility of another visit of this huge, apparently, will not come soon. The last time that "Florence" was approaching the Earth, was in 1890. According to the calculations of astronomers of the new so close visit of this giant, one should not wait until at least 2500 years.