Enough of politics. I’ve had more than enough of it.
Instead I’m going to write about newly-discovered asteroid 2016 HO3 that is circling the Earth.
Astronomers found a small asteroid circling around the Earth. Estimated to be between 40 meters (120 feet) and 100 meters (300 feet), the asteroid is now named 2016 HO3.
Scientists say 2016 HO3 is too far to be considered a true satellite of Earth, like the moon. Instead, they call 2016 HO3 as the best example of a quasi-satellite or near-Earth companion we have found so far.
The difference between quasi-satellites and true satellites is the time they take to loop around Earth. A true satellite should only loop within a few months or less than a year but it takes quasi-satellites a year to loop around Earth completely.
A week or two back I got hold of state vectors – position and velocity on a given date – for 2016 HO3 from NASA’s Horizons website, and plugged them into my orbital simulation model of the Sun and all the planets. Here’s a view of its orbit around the Earth as seen from the Sun over one year:
The black line is where the orbit is above the ecliptic – the planetary plane -, and the orange line is where the orbit is below the ecliptic. The horizontal smudge in the middle is the path of the Moon around the Earth. The Moon is roughly 450,000 km from the Earth. 2016 HO3 never gets nearer than about 20 million km from the Earth.
So it’s certainly going round the Earth, and taking almost exactly one year to do so.
But is it going round the Earth in the same way that the Moon does, drawn by the Earth’s gravitational attraction?
One way to test this is to reduce the Earth’s mass to 1 kg, and see whether it has any effect on either satellite. When I do this with the Moon, it immediately stops going round the Earth, moves quickly away, and becomes another satellite of the Sun.
But when I did this with 2016 HO3, it carried on going round the Earth in almost exactly the same orbit as before, going round and round the Earth just as shown above. So even with its correct mass, the Earth is having only a very small effect on it.
And that’s really because 2016 HO3 has an orbit round the Sun which is almost exactly the same as the Earth’s, only slightly more elliptic, and tilted slightly more to the ecliptic. Both the Earth and 2016 HO3 are taking 365.25 days to go round the Sun, and they’re always quite near each other. And they’re also far enough apart for the Earth’s gravitational influence to be tiny.
But it seems that the small influence of the Earth is going to be enough to keep 2016 HO3 from drifting slowly away for the next several hundred years (although I didn’t try to check that with my model, because it would have taken a long time). It’s going to be around for a long time.
I think they should give it a better name than 2016 HO3 if it’s going to be going round us for hundreds of years. Since it’s only been in this quasi-orbit for 100 years, it might best be named after some “star” born in 1916. Like film star Betty Grable. So my suggestion would be to call it Grable. Or BettyGrable. Or maybe just Betty.
I hope that made a welcome change from writing about all the mad, infuriating things happening on our little spinning planet. Or at least put them in a different perspective.