Using a NASA-designed software program, members of the public helped identify a cache of brown dwarfs – sometimes called failed stars – lurking in our cosmic neighborhood.
We’ve
never met some of the Sun’s closest neighbors until now. In a new study,
astronomers report the discovery of 95 objects known as brown dwarfs, many
within a few dozen light-years of the Sun. They’re well outside the solar
system, so don’t experience heat from the Sun, but still inhabit a region
astronomers consider our cosmic neighborhood. This collection represents some
of the coldest known examples of these objects, which are between the sizes of
planets and stars.
Members
of the public helped make these discoveries through Backyard Worlds:
Planet 9, a NASA-funded citizen science project that is a
collaboration between volunteers and professional scientists. Backyard Worlds
incorporates data from NASA’s Near-Earth Object Wide-Field Infrared Survey
Explorer (NEOWISE) satellite along with
all-sky observations collected between 2010 and 2011 under its previous moniker,
WISE. Data from NASA’s retired Spitzer Space Telescope and the facilities of the
National Science Foundation’s NOIRLab were also instrumental in the analysis.
“Vast
modern datasets can unlock landmark discoveries, and it’s exciting that these
could be spotted first by citizen scientists,” said Aaron Meisner,
assistant scientist at NSF’s NOIRLab and the lead author of the study
describing the brown dwarfs. “These Backyard Worlds discoveries show that
members of the public can play an important role in reshaping our scientific
understanding of our solar neighborhood.”
Why These Brown Dwarfs Are Important
Brown
dwarfs are not massive enough to power themselves like stars but are still many
times heavier than planets. Despite their name, brown dwarfs would actually
appear magenta or orange-red to the human eye if seen close up. While brown
dwarfs can be extremely hot, even thousands of degrees Fahrenheit, many of the
newly discovered ones are colder than the boiling point of water. Some even
approach the temperature of Earth and are cool enough to harbor water clouds.
Brown
dwarfs with low temperatures are also small in diameter and therefore faint in
visible light. Still, they give off heat in the form of infrared light, which
is invisible to the human eye yet detectable by telescopes such as NEOWISE and
Spitzer. For cold brown dwarfs like those in this study, the infrared signal is
also faint, so they are easier to find the closer they are to our solar system.
Discovering
and characterizing astronomical objects near the Sun is fundamental to our
understanding of our place in, and the history of, the universe. With their
relatively cold temperatures, these newly discovered brown dwarfs represent a
long sought missing link within the brown dwarf population.
In
2014, scientists discovered the coldest-known brown dwarf, called WISE 0855,
using data from NASA’s WISE mission in infrared light. WISE 0855 is about minus
10 degrees Fahrenheit, or minus 23 degrees Celsius. No other brown dwarf came
close to this object’s low temperature. Some researchers wondered if 0855 was
actually a rogue exoplanet – a planet that originated
in a star system but was kicked out of its orbit. This new batch of brown
dwarfs, together with others recently discovered using NEOWISE and Spitzer,
puts 0855 in context.
“Our
new discoveries help connect the dots between 0855 and the other known brown
dwarfs,” said astrophysicist Marc Kuchner, the principal investigator of
Backyard Worlds and the Citizen Science Officer for NASA’s Science Mission
Directorate. Kuchner is also an astrophysicist at NASA’s Goddard Space Flight
Center in Greenbelt, Maryland.
Since
the same physical processes may form both planets and brown dwarfs, the new
findings offer prospects for research into worlds beyond our solar system.
“This
paper is evidence that the solar neighborhood is still uncharted territory and
citizen scientists are excellent astronomical cartographers,” said
coauthor Jackie Faherty of the American Museum of Natural History in New York. “Mapping
the coldest brown dwarfs down to the lowest masses gives us key insights into
the low-mass star-formation process while providing a target list for detailed
studies of the atmospheres of Jupiter analogs.”
How Professional Scientists and Citizen
Scientists Collaborated
To
help find our Sun’s coldest, nearest neighbors, the professional astronomers of
the Backyard Worlds project turned to a worldwide network of more than 100,000
citizen scientists. These volunteers diligently inspect trillions of pixels of
telescope images to identify the subtle movements of brown dwarfs. Despite the
abilities of machine learning and supercomputers, there’s no substitute for the
human eye when it comes to scouring telescope images for moving objects. For
this new group of brown dwarfs, 20 citizen scientists across 10 different
countries are listed as coauthors of the study.
“Being
that this will be the first scientific paper that I’m a coauthor on, its
publication will definitely be the highlight of working with Backyard Worlds so
far,” said Les Hamlet, a citizen scientist in
Springfield, Missouri, who has worked on Backyard Worlds since 2017. “Also,
being connected in some way with the now-retired Spitzer Space Telescope
through this paper is kind of special to me.”
Backyard
Worlds volunteers primarily examine sky maps produced from observations by WISE
and NEOWISE. Participants then scour additional archival datasets, like those
from the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory
and Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American
Observatory, programs of NSF’s NOIRLab. Spitzer, which NASA retired in January
2020, provided the crucial brown dwarf temperature estimates. The results will
be published in The Astrophysical Journal.
Backyard
Worlds volunteers have already discovered more than 1,500 cold worlds near the
Sun. The new discovery of 95 brown dwarfs is the largest published sample of
these objects ever discovered through a citizen science project.
Alongside
the dedicated efforts of the Backyard Worlds volunteers, NOIRLab’s Astro Data
Lab science platform was instrumental in this research.
The
approach of the Backyard Worlds project – searching for rare objects in large
datasets – is also one of the goals for the Vera C. Rubin Observatory, an
NSF/Department of Energy facility currently under construction on Cerro Pachón
in Chile’s Atacama Desert. The Rubin Observatory will image the entire southern
sky every three nights over 10 years, providing a vast amount of data that will
enable new ways of doing astrophysical research.
The
new Backyard Worlds discoveries also underscore Spitzer’s pioneering legacy of
revealing the Sun’s coolest neighbors. NASA’s forthcoming James Webb Space
Telescope will also be a powerful tool for examining brown dwarfs for more insights into these
mysterious objects and what they can reveal about the formation of planets and
their atmospheres.
About Backyard Worlds: Planet 9
The ongoing Backyard Worlds: Planet 9 project, funded
by NASA, lets anyone join the quest to find more mysterious objects in
spacecraft data. Check it out at backyardworlds.org.
News Media Contact
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
Elizabeth Landau
NASA Headquarters
202-923-0167
elandau@nasa.gov
2020-159
Source: Jet Propulsion Laboratory