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
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