New ad­ven­tures for New Hori­zons

Space probe heads for dis­tant ob­ject that might not ex­ist.

Cosmos - - Digest -

The New Hori­zons space probe, which in 2015 beamed back hu­man­ity’s best-ever views of Pluto, is hurtling through the outer reaches of the so­lar sys­tem on its way to ren­dezvous with a lump of ice known as 2014 MU69.

It won’t get there for more than a year – the fly-by is ex­pected on 31 De­cem­ber 2018 or 1 Jan­uary 2019 – so the space­craft is hi­ber­nat­ing to con­serve energy Mean­while, sci­en­tists are do­ing every­thing they can to find out as much as pos­si­ble about its tar­get be­fore it gets there.

2014 MU69 sits in the Kuiper belt, a broad disc of small float­ing bod­ies way be­yond Nep­tune, four to six bil­lion kilo­me­tres from the Sun. In some ways it mir­rors the as­ter­oid belt be­tween Mars and Jupiter, though Kuiper belt ob­jects are on the whole much icier.

Very lit­tle is known about 2014 MU69: it was only dis­cov­ered in 2014, when astronomers used the Hub­ble Space Te­le­scope to look for some­thing in­ter­est­ing be­yond Pluto that New Hori­zons might be able to ma­noeu­vre it­self to­wards. Be­cause it is so tiny and dis­tant it’s hard to get a good look.

Astronomers have been watching very closely when MU69 passes in front of a back­ground star. On these oc­ca­sions, known as stel­lar oc­cul­ta­tions, ob­serv­ing changes to the im­age of the star re­veals in­for­ma­tion about the size of the lump, and also whether any de­bris near it might pose a nav­i­ga­tion hazard.

The first oc­cul­ta­tion oc­curred on 3 June. More than 50 ob­servers set up telescopes in South Africa and Ar­gentina to ob­serve it. Although the event lasted only two sec­onds, the telescopes cap­tured more than 100,000 images.

The ob­servers did see the back­ground star dim­ming but were un­able to make any di­rect ob­ser­va­tions of 2014 MU69 it­self, which sug­gests it is smaller than thought. It is also pos­si­ble it is ac­tu­ally a swarm of ob­jects, rather than a sin­gle en­tity.

Two other oc­cul­ta­tions in July were ob­served by NASA’S air­borne Strato­spheric Ob­ser­va­tory for In­frared As­tron­omy and the Hub­ble Space Te­le­scope.

When all the data has been an­a­lysed, the New Hori­zons team should have every­thing they need to make sure that when the probe wakes up on its jour­ney through the void, it will have the best in­for­ma­tion pos­si­ble to guide it on its way.

See the fu­ture of space mis­sions, page 72.

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