Reported in The Astrophysical Journal Supplement Series, researchers using data from the Dark Energy Survey (DES) have identified more than 300 so-called trans-Neptunian objects (TNOs)—minor planets located in the far reaches of the solar system—including well over 100 new discoveries.
Led by graduate student Pedro Bernardinelli and professors Gary Bernstein and Masao Sako at University of Pennsylvania, the research pioneers a new technique that could help astronomers in the search for undiscovered planets—including the mysterious “Planet 9.”
Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard … [+]
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What is a trans-Neptunian object (TNO)?
Also referred to as “transneptunian” objects, a TNO is a minor planet or dwarf planet that orbits the sun from beyond Neptune. That means over 30 astronomical units (au), a single au being the distance from the Earth to the Sun. Pluto is a TNO. In fact, it’s the original and the largest alongside Eris, with Haumea, Makemake and Gonggong close behind in terms of size.
What is the Dark Energy Survey (DES)?
The study uses results from DES, a six-year project that finished in January 2019. Using the 520-megapixel Dark Energy Camera mounted on the Blanco 4-meter telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile, its mission was to collect high-precision images of a quarter of the southern hemisphere’s sky to help astronomers understand the nature of dark energy—the mysterious force that is accelerating the expansion of the Universe. Although it was never intended to uncover TNOs, its mapping of a portion of the night sky in unprecedented detail.
The Víctor M. Blanco Telescope, also known as the Blanco 4m, is a 4-metre aperture telescope located … [+]
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How were the TNOs found?
DES was designed to study galaxies and supernovas, not to find TNOs, but the exquisite detail and the fact that images of the sky are are two hours apart meant that researchers could find TNOs by tracking the movement of “dots.” Seven billion of them, in fact. “The number of TNOs you can find depends on how much of the sky you look at and what’s the faintest thing you can find,” said Bernstein. “Dedicated TNO surveys have a way of seeing the object move, and it’s easy to track them down,” added Bernardinelli. “One of the key things we did in this paper was figure out a way to recover those movements.”
The team first reduced the seven billion dots to around 400 candidates that were seen over at least six nights of observation. “We have this list of candidates, and then we have to make sure that our candidates are actually real things,” said Bernardinelli. “For TNOs that are there, we actually pointed at them for 25 different nights. That means there’s images where that object should be, but it didn’t make it through the first step of being called a dot.”
What TNOs were found?
The researchers found 316 TNOs, including 245 discoveries made by DES and 139 new objects that were not previously published. With only 3,000 objects currently known, this DES catalog represents 10% of all known TNOs. Pluto, the best-known TNO, is 40 times farther away from the sun than Earth is, and the TNOs found using the DES data range from 30 to 90 times Earth’s distance from the sun. Some are way beyond Pluto.
Is “Planet 9” out there?
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How will this research help find “Planet 9?”
The new Vera C. Rubin Observatory, also at CTIO in Chile, could use the team’s method to detect even fainter and more distant objects than DES. By studying the orbits of these objects, researchers might also be able to look for “Planet 9,” a Neptune-sized planet that some think could exist beyond Pluto. “There are lots of ideas about giant planets that used to be in the solar system and aren’t there anymore, or planets that are far away and massive but too faint for us to have noticed yet,” said Bernstein.
Wishing you clear skies and wide eyes.
