Hy­dro­gen wall may have formed at our So­lar Sys­tem’s bor­der

Data from New Hori­zons is al­most match­ing that of Voy­ager, point­ing to the po­ten­tial ex­is­tence of a vis­i­ble bound­ary

All About Space - - Launch Pad -

NASA sci­en­tists are al­most cer­tain that their New Hori­zons probe is able to view the outer bound­ary of our So­lar Sys­tem. Ob­ser­va­tions in­di­cate that the probe is see­ing ex­tra-ul­tra­vi­o­let light at a point fur­ther from the Sun than would other­wise be ex­pected. This is likely to be pro­duced by a wall of hy­dro­gen and would be the point at which our Sun's pow­er­ful jets of mat­ter and en­ergy flow have waned, re­duc­ing the abil­ity to push back on the bits of dust and other mat­ter which floats within our galaxy's walls.

This is oc­cur­ring far be­yond the or­bit of Pluto, which New Hori­zons flew past in 2015. The probe, which is now 6.4 bil­lion kilo­me­tres (4 bil­lion miles) away from Earth, has since been mak­ing its way out­ward to­wards a mass of in­ter­stel­lar mat­ter, in­clud­ing hy­dro­gen. The mea­sure­ments be­ing taken by New Hori­zons are closely match­ing those made by the Voy­ager mis­sion 30 years ago. “We as­sume there’s some­thing ex­tra out there, some ex­tra source of bright­ness,” says the pa­per's au­thor Randy Glad­stone.

That said, the ul­tra­vi­o­let light might still be from an­other source deeper in the galaxy, which is why sci­en­tists are await­ing more data. New Hori­zons will con­tinue to take 360-de­gree snap­shots of ul­tra­vi­o­let emis­sions as it pre­pares to visit the Kuiper Belt Ob­ject 2014 MU69 next year. It should mean sci­en­tists gain a bet­ter idea of the ga­lac­tic hy­dro­gen wall which is un­der­stood to wrap around the So­lar Sys­tem like a bub­ble and form the thresh­old be­tween us and the broader galaxy.

Il­lus­tra­tion show­ing lay­ers of the he­lio­sphere and the 'shock' that forms

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