NASA, ESA, PG Martín (Autonomous University of Madrid), J. DePasquale (STScI)
It looks like someone took this NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158 and crossed it out with a white pen. In reality, it is a combination of several exposures of a foreground asteroid that moves across Hubble’s field of view, “photobombing” the observation of the galaxy.
Recently, astronomers used a set of archival images taken by the NASA/ESA Hubble Space Telescope to visually detect a fairly unknown population of small asteroids.
The treasure hunt required the analysis of 37,000 Hubble images, spanning a period of 19 years.
The reward was finding 1701 tracks of asteroids, with 1031 of these asteroids to be catalogued. Around 400, not catalogued, are of a size less than 1 km.
Volunteers from around the world, known as “citizen scientists“, contributed to the identification of this set of asteroids. Professional scientists then combined the volunteers’ efforts with machine learning algorithms to identify the asteroids.
The research results were presented in an article recently published in Astronomy & Astrophysics.
This is a new approach to find asteroids in astronomical archives that span decadesand researchers say it can be effectively applied to other data sets.
“We are deepening the observation of the population of smaller asteroids in the main belt. We were surprised to see such a large number of candidate objects,” he said. Pablo García Martinresearcher at the Autonomous University of Madrid, Spain, and main author of the article.
“There were some evidence that this population existeda, but now we are confirming it with a random sample of asteroids obtained using the entire Hubble archive. This is important to provide information about the evolutionary models of our Solar System.”
The large, random sample provides new insights into the formation and evolution of the asteroid belt. The discovery of many small asteroids favors the idea that are fragments of larger asteroids that collided and fragmented, like destroyed pottery, a crushing process that lasts billions of years.
An alternative theory for the existence of smaller fragments is that formed this way billions of years ago. But there is no conceivable mechanism that would stop them, like a snowball rolling down a hill, from becoming larger and larger as they gather dust from the planet-forming circumstellar disk around our Sun.
“The collisions would have a certain signature that we could use to test the current population of the main belt,” said co-author Bruno Merínfrom the European Center for Space Astronomy in Madrid, Spain.
Because of Hubble’s fast orbit around Earth, it can pick up errant asteroids through their tracks in the exposures it obtains.
Seen from a ground-based telescope, an asteroid leaves a trail in the image; you asteroids “photobomb” Hubble displaysappearing as curved and unmistakable streaks in photos taken by the space telescope.
This chart is based on archival data from the Hubble Space Telescope, which was used to identify a population of very small, largely unknown asteroids. The asteroids were not the intended targets, but rather background stars and galaxies in Hubble images. The treasure hunt required analyzing 37,000 Hubble images spanning 19 years. To this end, “citizen science” volunteers and artificial intelligence algorithms were used. The reward was finding 1701 previously undetected asteroid tracks.
As Hubble rotates around Earth, change your point of view while observing an asteroid, which is also moving along its own orbit.
By knowing Hubble’s position during observation and measuring the curvature of the streaks, scientists can determine distances to asteroids and estimate the shapes of their orbits.
The asteroids photographed are mostly in the main waist, which lies between the orbits of Mars and Jupiter. Your brightness is measured by cameras Hubble’s sensitive sensors, and comparing its brightness to its distance allows an estimate of its size.
The faintest asteroids analyzed during the study are about a fortieth of a million – 1/(40×106) – from the brightness of the faintest star that can be seen by the human eye.
“Asteroid positions change over time and, therefore, it is not possible to find them just by entering the coordinates, because at different times they may not be there”, said Bruno.
“As astronomers, We don’t have time to search in all asteroid images. That’s why we had the idea of collaborate with more than 10,000 citizens volunteers to analyze Hubble’s huge archives,” he added.
In 2019, an international group of astronomers launched Hubble Asteroid Hunter, a citizen science project to identify asteroids in archival Hubble data.
The initiative was developed by researchers and engineers from the European Science and Technology Center and the ESAC Science Data Center, in collaboration with Zooniverse, the largest and most popular citizen science platform in the world, and with Google.
A total of 11,482 citizen volunteerswhich provided around two million identifications, then received a training set for an automated, artificial intelligence-based asteroid identification algorithm.
This pioneering approach can be effectively applied to other datasets.
The project will then explore asteroid risks previously unknown to characterize their orbits and study their properties, such as rotation periods.
Since most of these asteroid streaks were captured by Hubble many years ago, Can’t follow them now to determine their orbits.
