{"id":303,"date":"2021-11-15T19:00:17","date_gmt":"2021-11-15T18:00:17","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=104160"},"modified":"2021-11-15T19:18:10","modified_gmt":"2021-11-15T18:18:10","slug":"does-our-solar-system-have-a-wall","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/does-our-solar-system-have-a-wall\/","title":{"rendered":"Does our Solar System have a wall?"},"content":{"rendered":"

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By Dr Alastair Gunn\n \t\t<\/p>

Published: Monday, 15 November 2021 at 12:00 am<\/p>

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Yes and no. True, scientists sometimes describe the rise in temperature at the\u00a0Solar\u00a0System\u2019s \u2018heliopause\u2019 as a wall. This is the region of space where the \u2018solar wind\u2019 \u2013 the constant stream of mostly protons, electrons, and alpha particles emitted by the Sun \u2013 is no longer strong enough to push back the \u2018wind\u2019 of particles coming from distant stars. Here, the hot, tenuous solar wind plasma (ionised gas) gives way to the colder, denser \u2018interstellar medium\u2019 (ISM).<\/p>\n

The heliopause marks the boundary between the\u00a0Solar\u00a0System and interstellar space \u2013 it is the edge of the \u2018heliosphere\u2019, the bubble of space in which the Sun\u2019s magnetic field and particle emissions dominate.<\/p>\n

How large is this important boundary? Consider that one astronomical unit, AU, is defined as the average distance between the Earth and the Sun. The heliosphere lies at about 120AUs from the Sun in the direction facing the interstellar wind \u2013 and in the opposite direction it extends to at least 350AU.<\/p>\n

\""Does\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
The Sun causing a bow shock (orange) as its solar wind (blue) collides with interstellar medium (gas, dust and other matter between star systems) \u00a9 Science Photo Library<\/span><\/figcaption><\/div>\n

By deflecting 70 per cent of energetic \u2018cosmic rays\u2019, the Sun\u2019s heliosphere is crucial in protecting the Earth (and hence humans) from harmful interstellar radiation.<\/p>\n

Launched in 1977, initially bound for Jupiter and Saturn, NASA\u2019s Voyager 1 and Voyager 2 spacecraft appear to have crossed the Sun\u2019s heliopause on 25 August 2012 and 5 November 2018, respectively. Instruments onboard Voyager 2 discovered that as plasma at the heliopause slows down, it becomes denser and the local magnetic field increases.<\/p>\n

Just beyond the heliopause, the temperature of the ISM is a staggering 29,700\u201350,000\u00b0C. This region has somewhat sensationally been dubbed the \u2018wall of fire\u2019. This is misleading because, although it is\u00a0incredibly\u00a0hot, the plasma here is extremely diffuse; meaning the Voyager probes (or anything else for that matter) can easily pass through the heliopause completely unharmed.<\/p>\n

Read more:<\/strong><\/p>\n