This Hubble Space Telescope image of the barred spiral
galaxy UGC 12158 looks like someone took a white marking pen to it. In reality
it is a combination of time exposures of a foreground asteroid moving through
Hubble's field-of-view, photobombing the observation of the galaxy. Several
exposures of the galaxy were taken, what is evidence in the dashed pattern. The
asteroid appears as a curved trail due to parallax: because Hubble is not
stationary, but orbiting Earth, and this gives the illusion that the faint
asteroid is swimming along a curved trajectory. The uncharted asteroid is in
inside the asteroid belt in our solar system, and hence is 10 trillion times
closer to Hubble than the background galaxy. Rather than a nuisance, this type
of data are useful to astronomers for doing a census of the asteroid population
in our solar system.
NASA, ESA, Pablo García Martín (UAM); Image
Processing: Joseph DePasquale (STScI); Acknowledgment: Alex Filippenko (UC
Berkeley)
Volunteers from around the world
known as "citizen scientists" contributed to the identification of
this asteroid bounty. Professional scientists combined the volunteers' efforts
with machine learning algorithm to identify the asteroids. It represents a new
approach to finding asteroids in astronomical archives spanning decades, which
may be effectively applied to other datasets, say the researchers.
"We are getting deeper into
seeing the smaller population of main belt asteroids. We were surprised with
seeing such a large number of candidate objects," said lead author Pablo
García Martín of the Autonomous University of Madrid, Spain. "There was
some hint of this population existing, but now we are confirming it with a
random asteroid population sample obtained using the whole Hubble archive. This
is important for providing insights into the evolutionary models of our solar
system."
The large, random sample offers new
insights into the formation and evolution of the asteroid belt. Finding a lot
of small asteroids favors the idea that they are fragments of larger asteroids
that have collided and broken apart, like smashed pottery. This is a
grinding-down process spanning billions of years.
An alternative theory for the
existence of smaller fragments is that they formed that way billions of years
ago. But there is no conceivable mechanism that would keep them from
snowballing up to larger sizes as they agglomerated dust from the planet-forming
circumstellar disk around our Sun. "Collisions would have a certain
signature that we can use to test the current main belt population," said
co-author Bruno Merín of the European Space Astronomy Centre, in Madrid, Spain
.
Amateur Astronomers Teach AI to
Find Asteroids
Because of Hubble's fast orbit
around the Earth, it can capture wandering asteroids through their telltale
trails in the Hubble exposures. As viewed from an Earth-based telescope, an
asteroid leaves a streak across the picture. Asteroids "photobomb"
Hubble exposures by appearing as unmistakable, curved trails in Hubble
photographs.
As Hubble moves around the Earth,
it changes its point of view while observing an asteroid, which also moves
along its own orbit. By knowing the position of Hubble during the observation
and measuring the curvature of the streaks, scientists can determine the
distances to the asteroids and estimate the shapes of their orbits.
The asteroids snagged mostly dwell
in the main belt, which lies between the orbits of Mars and Jupiter. Their
brightness is measured by Hubble's sensitive cameras. And comparing their
brightness to their distance allows for a size estimate. The faintest asteroids
in the survey are roughly one forty-millionth the brightness of the faintest
star that can be seen by the human eye.
"Asteroid positions change
with time, and therefore you cannot find them just by entering coordinates,
because at different times, they might not be there," said Merín. "As
astronomers we don't have time to go looking through all the asteroid images.
So we got the idea to collaborate with over 10,000 citizen-science volunteers
to peruse the huge Hubble archives."
In 2019 an international group of
astronomers launched the Hubble Asteroid Hunter, a citizen-science project to
identify asteroids in archival Hubble data. The initiative was developed by
researchers and engineers at the European Science and Technology Centre (ESTEC)
and the European Space Astronomy Centre's science data center (ESDC), in
collaboration with the Zooniverse platform, the world's largest and most
popular citizen-science platform, and Google.
This graph is based on Hubble Space Telescope archival
data that was used to identify a largely unseen population of very small
asteroids in their tracks. The asteroids were not the intended targets, but
instead photobombed background stars and galaxies in Hubble images. The
comprehensive treasure hunt required perusing 37,000 Hubble images spanning 19
years. This was accomplished by using "citizen science" volunteers
and artificial intelligence algorithms. The payoff was finding 1,701 asteroid
trails of previously undetected asteroids.
Pablo García Martín (UAM), Elizabeth Wheatley (STScI)
A total of 11,482 citizen-science
volunteers, who provided nearly 2 million identifications, were then given a
training set for an automated algorithm to identify asteroids based on
artificial intelligence. This pioneering approach may be effectively applied to
other datasets.
The project will next explore the
streaks of previously unknown asteroids to characterize their orbits and study
their properties, such as rotation periods. Because most of these asteroid
streaks were captured by Hubble many years ago, it is not possible to follow
them up now to determine their orbits.
The findings are published in the journal Astronomy and Astrophysics.
To learn how you can participate in
citizen science projects related to NASA, visit https://science.nasa.gov/citizen-science/. Participation is open to everyone around the world,
not limited to U.S. citizens or residents.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Source: Hubble Goes Hunting for Small Main Belt Asteroids - NASA Science
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