Killer asteroids, THOR algorithm can save Earth

Predicting the arrival of an asteroid that could damage Earth early is one of the priorities of Ed Low, a former NASA astronaut with a Ph.D. in applied physics. To achieve this, direct B612 . Foundationwhich is a non-profit organization engaged in the study of celestial bodies that it discovered in the course of its activity More than 100 new asteroids. The discovery of an asteroid is not shocking news in itself. They discover it all the time — but she is interested in learning more about the technique Lou uses to do it.

It is not based on direct observation of the heavenly vault with a telescopebut in connection with the analysis of data already obtained by other telescopes, from old images, with the help of the latest and most powerful computational tools. This is the modern way of doing astronomy, says Lu. Ed Lu, along with B612, used THOR, an algorithm for analyzing astronomical images And check out hundreds of them—the ones in the NOIRLab Digital Archive alone number 412,000.

The purpose of the algorithm — born out of a collaboration between the B612 Foundation, Joachim Moeyens (a graduate student at the University of Washington) and Mario Yorick, professor of astronomy — It is the identification of asteroids among the 68 billion cosmic light points present in the images: Determine how many asteroids there are actually and how many points of light were captured at different times depicting the same asteroid.

To understand how THOR works on a large scale, it is useful to specify that asteroids are usually detected when a portion of the sky is imaged multiple times during the same night: distant stars and galaxies correspond to points of light that remain fixed between one image and another, while celestial bodies closer to Earth move quickly, Thus their light points change during the same night. Astronomers call a series of observations of a single celestial body moving during the same night a “tracklet.” However, if asteroids are not systematically searched for, these points of light Only random data is considered in the random images of the skyLou says.

search group Each point of light is the starting point for identifying the asteroidAnd the Even without a tracking device: THOR is an acronym for Tracklet-less Heliocentric Orbit Recovery, or Trackless Solar Orbit Recovery. In more detail, starting with the assumption that the motion of the asteroid is governed by the laws of microgravity, THOR:

• It traces the possible orbit of a point of light, assuming that it is located at a certain distance and is moving at a certain speed;
• Calculates the location of the light point on the previous and following nights, moving along the assumed orbit;
• Compare the estimated data with images of the sky taken on the previous and following nights: If the point of light is really where it’s supposed to, there’s a good chance it’s an asteroid. To reach this conclusion, the algorithm checks the displacement of a celestial body by examining at least five observations in a few weeks.

It will be clear that starting with the aforementioned 68 billion light points, there are thousands of possible orbits to calculate. An impossible task to complete without the help of cloud computing. Not by chance in the project There is a contribution from Google and its cloud platform. The results obtained by THOR are promising:

• Scientists examined about 1/8 of the data from the NOIRLab archives (for the month of September 2013)
• THOR has identified 1,354 bright spots that could correspond to asteroids. The International Astronomical Union has already classified many of them as such, but some of them were only observed during one night and the data was insufficient to determine their orbit with certainty.
• 104 new asteroids discovered thanks to THOR

The activity of the B612 Foundation is absolutely necessary, given that of the approximately 25,000 asteroids with a diameter of at least 140 meters around the Earth, only 40% have been identified, while the remaining 60% remain undiscovered. These are celestial bodies capable of causing devastating effects in the unfortunate hypothesis that they managed to reach the surface of the Earth. Knowing its path in advance will also allow the timely use of deflection systems such as Those studied as part of NASA’s DART mission.

THOR could also make use of the latest instruments to observe the celestial vault, such as the Vera C. Rubin Observatory’s LSST telescope, Currently under construction in Chile. One of the project’s goals is to study supernovae as well as to identify celestial bodies approaching Earth. Using THOR and its predictive model could halve the number of observations needed to identify study objects (the telescope could return to the same point in the sky every two nights instead of every four nights, thus expanding the search area).