Ulti­ma Thule as seen from New Hori­zons

NASA/Johns Hop­kins Uni­ver­si­ty Applied Physics Laboratory/Southwest Research Insti­tute

Trav­el far enough toward the edge of the solar sys­tem and it’s as if you’ve trav­eled back in time. That’s what NASA’s New Hori­zons space­craft found when it passed beyond Plu­to deep into the Kuiper Belt to per­form a fly­by of an object nick­named Ulti­ma Thule. 

Kuiper Belt Objects orbit the sun so far out they may wan­der in the frigid void for bil­lions of years undis­turbed and there­fore unchanged since the solar sys­tem formed. To vis­it one is to see our cor­ner of the cos­mos as it looked over 4 bil­lion years ago. 

New Hori­zons per­formed its fly­by of Ulti­ma Thule, offi­cial­ly known as 2014 MU69, on New Year’s Day. Researchers have just pub­lished the ini­tial results from the space­craft’s obser­va­tions of the dis­tant object.

The paper, pub­lished in Fri­day’s edi­tion of Sci­ence, describes a space rock shaped like a flat­tened snow­man drift­ing alone in the cold. Ulti­ma Thule has no appar­ent satel­lites, rings or even detectable amounts of dust and gas­es accom­pa­ny­ing it as it makes its 293-year jour­ney around the sun. 

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Earth­’s ori­gin sto­ry is one of vio­lent col­li­sions. It’s thought that our plan­et’s ear­li­est days were marked by a heavy bom­bard­ment of aster­oids, comets and oth­er left­over bits from the solar sys­tem’s for­ma­tion. The moon itself may even be a prod­uct of a mas­sive ear­ly col­li­sion. 

But out in the far reach­es of the Kuiper Belt, where the sun’s radi­a­tion is bare­ly felt as either light or warmth, Ulti­ma Thule seems to have had a remark­ably peace­ful his­to­ry. Even the join­ing of the objec­t’s two lobes (the larg­er “bel­ly” of the snow­man shape is called Ulti­ma while the head is Thule) was not the result of a vio­lent impact.

“All avail­able evi­dence indi­cates that MU69 is instead the prod­uct of a gen­tle col­li­sion or merg­er of two inde­pen­dent­ly formed bod­ies, pos­si­bly con­tact­ing one anoth­er at (or more slow­ly than) their mutu­al grav­i­ta­tion­al infall speed,” reads the paper by lead author and New Hori­zons chief Alan Stern, along with dozens of cred­it­ed co-authors.

In oth­er words, Ulti­ma Thule is two small­er bod­ies in a sort of eter­nal hug, cling­ing to each oth­er in the cold dark­ness for bil­lions of years. This com­ing togeth­er was a rel­a­tive­ly calm event, and per­haps the only event Ulti­ma Thule has ever expe­ri­enced, at least until a strange robot flew by it a few months ago on a sight­see­ing expe­di­tion.

Before vis­it­ing Ulti­ma Thule, New Hori­zons explored Plu­to’s plan­e­tary sys­tem in 2015, send­ing back vivid and detailed images of a sur­pris­ing­ly com­plex world. 

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In addi­tion to dis­cern­ing some of Ulti­ma Thule’s ori­gin sto­ry, NASA’s space­craft helped con­firm that the small­ish world (30 kilo­me­ters or 19 miles wide) is red in col­or as expect­ed, but comes with some unex­pect­ed and so far unex­plained bright spots.

This is like­ly just the begin­ning of what New Hori­zons will teach us about Ulti­ma Thule, the Kuiper Belt and the ori­gins of our solar sys­tem. Stern and col­leagues write that this study is based on only about 10% of the total data New Hori­zons gath­ered dur­ing its Jan­u­ary fly­by. 

More data will con­tin­ue to come in until trans­mis­sion is com­plete in 2020.

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Tiny T. rex is ter­ri­ble tyran­t’s pet-size pre­his­toric pre­de­ces­sor: A new­ly dis­cov­ered ances­tor of Tyran­nosaurus rex was­n’t near­ly as impos­ing as the king of dead­ly dinosaurs.

Tags Sci-Tech NASA Space

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