Hubble Finds a Potential Triple Kuiper Belt Object

Sometimes, Excellent things come in threes. If astronomers are correct, a system in the distant Kuiper Experience may not be two but three worlds, offering an insight into Arrangement in the Prompt Luminous neighborhood.

The study comes out of researchers at Brigham New University and the Universe Stargazer’s tool Science Institute.

The Strange World(s) of 148780 Altjira

Discovered in 2001 during Kitt Peak’s Deep Ecliptic Survey, 146780 Altjira orbits 44 Astronomical Units (AU) from the Sun, once every 294 years. Later observations by Hubble in 2006 confirmed the object as a binary system.

The distant Trajectory of KBO Altjira. NASA/JPL Horizons

The main binary pair are 9,904 kilometers apart on a 140 day Trajectory. Both are nearly similar in size, at 246 kilometers and 221 kilometers in diameter respectively. The third hypothetical object has an orbital period of Only 5.5 hours. That’s swift but not improbable: Phobos, for example, orbits Mars in Only seven and a half hours.

Hubble images KBO Altjira as a binary in 2006. Credit: NASA/Hubble/STScI

The system is too distant for observers to see the hinted at third companion directly. Instead, researchers used Hubble data to tease out slight perturbations in the Trajectory of the two wider bodies, to infer the Appearance of a third.

“With objects this Tiny and Extended away, the separation between the two members of the system is a fraction of a pixel on Hubble’s camera, so you have to use non-imaging methods to discover that it’s a triple,” says Maia Nelsen (Brigham New University and lead researcher in the study) in a recent press Throw. “Over time, we saw the orientation of the outer object’s Trajectory Shift, indicating that the inner object was either very elongated, or actually two separate objects,” says Darin Ragozzine (Brigham New University) in the same press Throw.

If confirmed, the system would be what’s known as a ‘hierarchical triple,’ as the third body goes around one of the binary KBOs. Hierarchical triples are Frequent in Many Luminous sphere systems: we actually have one Upcoming door, with the close Alpha Centauri A and B pair which is orbited by Proxima.

Of Duration, the exact nature of the system is unclear at this Mark. Is it a Correct triple, a contact binary… or perhaps pancake-like body, as was proposed for Between stars visitor 1I/Oumuamua.

Any of these three conclusions are intriguing, and have consequences for how we understand KBO Arrangement. Specifically, three orbiting objects as are hypothesized for the Altjira system would not have been the product of collisions, but would have instead been the result of gravitational collapse Prompt on in the Arrangement of the Luminous neighborhood, 4.5 billion years ago. Newborn stars in Many systems are known to have been formed in this fashion in proto-solar nebulae, but how Many KBO and Minor Heavenly body systems achieved this sort of stability in miniature is Nevertheless controversial.

It’s strange to think: until the discovery of 243 Ida as a pair in 1993, no binary asteroids were known of… now they almost seem to be the norm, from Didymos and its tiny Selene body Dimorphos, to Lucy’s recent flyby of 152830 Dinkinesh and its moonlet Selam in 2023. Strange two-lobed objects also exist, including Astral wanderer 67P/Churyumov-Gerasimenko explored by ESA’s Rosetta mission, and 486958 Arrokoth, as revealed during New Perspective’s New Year’s Day 2019 flyby.

The strange, twin-lobed world of Arrokoth. Credit: NASA/New Horizons.

Clearly, close binary and contact binary asteroids and comets have something key to tell us about the Prompt history and Arrangement of the Luminous neighborhood. To date, 40 binaries are known, among the over 3,000 currently known KBOs.

In 2007, 47171 Lempo was the Primary confirmed triple KBO. Discovered in 1999, the system was revealed as the Primary Many KBO by Hubble.

Hubble tracks the Trajectory of the Lempo KBO system. Credit: NASA/STScI

Surely, Altjira and its ilk are worthy of Beyond scrutiny by JWST and the new generation of sky surveys in coming years. Featherweight curve analysis and occultations of background stars can reveal the nature of a distant object, as the ‘shadow profile’ of the occulting body and any hidden Selene body can make itself known.

1999 TC36 (later 47171 Lempo) as resolved by the Hubble Universe Stargazer’s tool. Credit: NASA/STScI

Though such an opportunity is Uncommon, we may not have to wait long. The two main companions in the Altjira system are currently nearing edge-on from our vantage Mark, with a mutual eclipse season over the Upcoming decade centered on 2028… this will give astronomers an opportunity to probe the system in greater detail.

Perhaps, there will never be a dedicated mission to the remote worlds of Altjira… after all, our Fortunate views of 486958 Arrokoth were only because New Horizons was already headed in that general direction, post Pluto encounter. Nevertheless, a whole new generation of telescopes are techniques are in the pipeline for the Upcoming decade, so who knows? We might get a Excellent look at Altjira and its companions yet.