In June this twelvemonth , two astronomers discovered probably thelargest comet ever seen , an object so big there was initial debate if it might really be a gnome planet on a comet - same orbit . This " mega comet " is on an inward - bind trajectory from the outer Solar System .
Now , its discoverers and many co - authors have reported the results of three months drop learning more about this exceptional objective . A paper accept by theAstrophysical Journal Letters(preprint onArXiv.org ) bring out plenty we did n’t know about this Earth when its existence hit the news .
Anyone learning about C/2014 UN271(Bernardinelli - Bernstein ) for the first fourth dimension need n’t worry , though . Even at its penny-pinching coming in 2031 , UN271will be more distant than Saturn at around 11 astronomic units away ( ( 1 AU = aloofness from Earth to the Sun ) , frustrative astronomers who would love a closer aspect at something this unusual .
UN271 ’s orbit has been traced , and its last approach to the Sun was around 3.5 million years ago . On that function it only draw to 18 astronomic units aside , almost twice the distance it will reach this time and around the space to Uranus . It ’s likely to soon be the close to the Sun it has ever been , make it the most pristine comet we have ever seen , a true cam stroke - back to the Solar System ’s origins .
Early number for UN271 ’s size of it were ineluctably imprecise . However , the authors have now settled on an estimate of 150 kilometers ( 100 miles ) across . That gives it a volume thousands of fourth dimension a typical comet , and at least 10 times bigger than even a behemoth like Hale - Bopp . For comparison , comet 67P , which Rosetta canvass , is only 2.6 miles ( 4.3 klick ) across , andArrakoth , the furthest humans humans has ever explored , is22 miles ( 35 kilometre ) retentive and12 miles ( 20 kilometers ) wide .
There were Hope of getting more certainty on the sizing when UN271passed in front of a adept as seen from Eastern Australia , butcloud overlay the entire regionfrom which the event might have been see . However large , though , the comet wo n’t be visible to the naked center when it make its close approach .
One of the first thing astronomers wanted to know about UN271was whether it was already showing cometic activity , that is having textile turn to gas and form a coma . UN271had been photographed by bothTESS , NASA ’s planet - hunting watch , and the Dark Energy Survey ( DES ) in 2018 without anyone observe its significance , so the author checked the earlier images to see if they could find out tell - tale signs of fuzziness .
They discover a divergence in the measurements , with TESS reporting an object almosttwice as bright . It turns out the rationality was that DES was see at only a lowly area around UN271 , while TESS was aggregating over a gravid blank , including a magnanimous , but faint comatoseness , indicating fabric had been escaping for a long time . The comatoseness ’s report can not yet be detected , but carbon dioxide carrying detritus grain with it as it get away is think most likely .
UN271 ’s arse is fainter still , requiring the combination of many images to notice it at all .
“ It is unremarkably a lose proposal to chew over on the future demeanor of comet , ” the newspaper publisher acknowledges , but nevertheless projects that at its brightest UN271should be around magnitude 9 – visible to amateurs with pocket-size scope under coloured skies .
Some astronomers are dandy to get a mission go to UN271 , cipher the good time for a flyby is 2033 , which would command a launching by 2028 .
