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Bad Astronomy | THOR program speeds up search for near-Earth asteroids

Bad Astronomy |  THOR program speeds up search for near-Earth asteroids
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Note: This article was written in part to aid promotion. June 30 Asteroid DayA global effort to raise awareness of the dangers and scientific significance of asteroids. On June 30 of each year, Anniversary of the great Tunguska impact of 1908and is one of the founding partners of the B612 Foundation mentioned below. I was originally scheduled to be in Luxembourg. – Asteroid Day HQ – to manage some panels and talk about asteroids, but a health issue (now solved!) prevented me from traveling. Still, I hope you’ll take a look at the great events planned, including livestreams with scientists, astronauts, and other experts.. Learn and have fun!


Finding near-Earth asteroids has taken a huge leap forward, thanks to THOR.

Yes, different THOR. This stands for Tracketless Heliocentric Orbit Recovery, and this is a method that not only greatly speeds up how quickly asteroids can be found, but also allows searching using old, archived images regardless of when they were taken. he is faster and can only use the large database of observations available online. So yes, this is very important.

In general, finding an asteroid is not difficult, it just takes time. They appear to move slowly across the sky as they orbit the Sun. You use a telescope to take a view of a single point, wait a little while – usually you go to other points in the sky to observe them – then you observe the same point again. Do it again and you now have three images of the same piece of sky.

The stars don’t move, so if you align the three images, the stars would all appear in the same place, but the asteroid would have moved and formed a line of three dots. This is the trace of its movement in that time, which is why this hyphen is called. scout. It may be enough to use age-old equations of motion to create an estimated trajectory for the object, and the equation describing that trajectory can then be projected into the future or past to see where it will be in the sky or where it is; future observations or previously archived ones can be searched to see if they are there, and the trajectory can be refined.

In practice, of course, it’s much more complicated, but that’s more or less how it was done. One problem is that this method is very computer time intensive and not very efficient. Another is that asteroids don’t always seem to be moving in a straight line; The movement of the Earth around the Sun – or the movement of an orbiting observatory around the Earth – can wiggle these lines, making it harder to detect asteroids. Also, as large surveys come online over the next few years, they will find millions of asteroids (!!) and this method will run into a dead end trying to keep track of them all.

enter THOR [link to paper]a project developed by Asteroid Institutea project B612 Foundation. The idea is not to follow the asteroids themselves, but to create theoretical test orbits for an asteroid, which is a little behind the usual way of doing things. Let’s say a test orbit is a circular orbit with a distance of 300 million km from the Sun at a certain inclination and orientation. This produces a series of numbers called orbital parametersand they in turn define an equation that can be solved for where an asteroid is at a given time.

This test trajectory is then projected forward or backward relative to the times of other observations, and then objects close to this path are searched for. Algorithms for such searches are common and tend to be quite fast.

This method has several advantages – The Asteroid Institute has a good FAQ to explain all this – but what’s really striking is that it doesn’t need observations taken close together over time and at a certain speed to work. The position of a potential asteroid in a test orbit can be calculated for the duration of any given observation from any observatory. Because we know when an observation was made, and also where in the sky it was filmed, it is possible to see if the potential asteroid was in that observation at the time, even if it was taken weeks or more ago.

This is extremely powerful. there are many – one share – astronomical observations stored in databases, and in fact the team that created the algorithm tested it on real data. They used two weeks of observations. Zwicky Temporary Facility, a massive sky survey to look for potential asteroids and managed to recover over 97% of previously known asteroids appearing in the data! Influential.

They also used data NOIRLab Resource catalogreviewed an enormous database of astronomical observations and a month’s worth of observations. They found 104 new asteroids in the data and were confirmed by them. Minor Planet Center. So it can find new asteroids as well as known asteroids. This is important because new observations could trigger thousands of warnings about potential asteroids; if these could be quickly sorted out for known asteroids, it would be a huge time saver.

THOR can extract asteroids quickly and over different observations and use old images to actually detect orbits. As these massive new surveys come online, THOR looks set to prove incredibly useful in locating the many asteroids that are expected to be discovered. 6 million in the next ten years.

That’s a lot of rock. Knowing where they are and more importantly where they will be obviously very importantThat’s why I’m in for it.


Note: If you are a code enthusiast, THOR on GitHub.

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