Asteroid (488453) 1994 XD will approach the Earth to a distance of 3 million km on June 12, 2023

Nothing bad will happen. It won’t collide, it won’t fall, it won’t even move the Moon out of the lunar orbit.

It would seem that this is all that could be written about the upcoming – quite ordinary – approach of the Earth with a not very large asteroid. But – no – not all.

As follows from the notation – (488453) 1994XD – an asteroid discovered in 1994 (December 1, to be exact). It belongs to the Apollo family – these are asteroids that penetrate the earth’s orbit with the closest part of their orbit to the sun (astronomers call the point of the orbit of a celestial body closest to the Sun “perihelion”). The perihelion of the orbit of this celestial body is closer to the Sun than the orbit of Venus (0.6 AU). To Mercury, of course, it does not hold out much. And aphelion (the point of the orbit farthest from the Sun) is located beyond the orbit of Mars. If the orbit of this asteroid lay in the plane of the orbit of Earth, Venus or Mars, it would have a chance to collide with something. And this is almost true: the orbit of the asteroid (488453) 1994 XD deviates only 4 degrees from the plane of the ecliptic (the plane of the earth’s orbit). But this is quite enough to approach Venus up to 1 million km, with the Earth – up to 3 million km, and with Mars – up to 4.5 million km. But not closer. As you can see, Venus is more at risk, but the risk is small in relation to her – it is actually absent. 1 million km is a huge distance. This is 2.5 times farther than the distance from the Earth to the Moon.

Fears in the spirit of “What if it will be attracted” are untenable, because the Moon does not fall, although its relative speed is only 1 km / second. Asteroids of the Apollo family move in rather elongated orbits, and crossing the orbits of the planets, they have speeds significantly exceeding the speeds of those planets they encounter – by many kilometers per second. It will fly by and not feel the earth’s gravity at all.

What else do we know about this asteroid?

It is less than a kilometer in diameter – about 600 meters, but this is inaccurate. Such convergences make it possible to clarify – both the diameter and the period of axial rotation, and even the chemical composition, and perhaps even an approximate map of the surface, can be compiled using the radar scanning method. But still, it should be borne in mind that 600 meters is still a dangerous asteroid when it comes to a collision. Now there is no talk of a collision, but if it did, it would be extremely unpleasant news.

Asteroid orbital period (488453) 1994XD around the Sun is 3.59 years, and this is very similar to the orbital resonance with the Earth, as a result of which the asteroid passes the point of closest approach to our planet 1 time in 9 years. And what has fallen into resonance is doomed to do the same for all eternity. But it is possible that two other planets, with which the minor planet also has “close contacts” – Venus and Mars, can slightly loosen this resonance.

In 2005, a satellite was discovered near this asteroid. Yes – it happens. Small planets, like large ones, can also have satellites. Moreover, in terms of the number of satellites, small planets have long overtaken large ones. At the moment (oh no – as of January 2022), science knows 457 asteroids with satellites (probably in reality there are significantly more), and some asteroids have more than one satellite. In total, there are about half a thousand satellites of asteroids in the solar system, but how many satellites of large planets do we know? – significantly less. This, of course, is about natural satellites – such as the Moon, Phobos with Deimos, and the like, and not those that Elon Musk launches fifty at a time.

Asteroid satellite (488453) 1994XD quite a crumb – about 150 meters in diameter, and most likely it is just a shapeless stone block that makes a revolution in 18 hours around another shapeless block, which is a little larger. The gap between these bodies is also small – something about 200 meters. In the conditions of the local microgravity, one could simply jump from one asteroid to another. The main thing is not to miss.

And now, this couple flies to visit us. This is very good, because asteroids with satellites so close to the Earth do not often fly up. In any case, I don’t remember such a case.

It is interesting to estimate the angular size of this system from a distance of 3 million km

A simple calculation shows that something 1 km across (for simplicity) from a distance of 3 million km will have an apparent size of 1/15 of an arc second. This is very little. It is extremely small for amateur, and indeed for ground-based telescopes. But it is quite consistent with the resolution of the James Webb telescope (although it was not launched at all for this) or the Hubble telescope. And radio interferometers can even work with such small objects.

For lovers of astronomy on the night of closest approach – from June 11 to June 12, 2023 – an asteroid (488453) 1994XD will appear as a stellar object of magnitude 14 (almost like Pluto), rather quickly passing from the constellation Cygnus to the constellation Cepheus. The asteroid will pass over the northern hemisphere of the planet – here we are lucky.

Well, the last thing I would like to say is that astronomers are extremely actively monitoring this and thousands of similar asteroids. While I was preparing this publication, collecting information about the object, I had the opportunity to evaluate the colossal work that is being done by a variety of observatories, conducting hundreds and thousands of observation sessions of all potentially dangerous celestial objects. It’s amazing how they have time for everything else, which is also interesting, but does not threaten us. But as we know, astronomers have time for everything – even for infinitely distant black holes in the cores of other galaxies.

PS: The time indicated on the maps corresponds to Moscow +1 hour

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