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| Voyager Solar System 'exit' debated | |
| (35 minutes later) | |
| The Voyager-1 probe may be outside the Solar System, some scientists say. | |
| If confirmed, it would be the first man-made object to do so. | If confirmed, it would be the first man-made object to do so. |
| Launched in September 1977, the probe was sent initially to study the outer planets, but then just kept on going. | Launched in September 1977, the probe was sent initially to study the outer planets, but then just kept on going. |
| Researchers who have studied its data indicate it has now entered a realm of space beyond the influence of our Sun. | Researchers who have studied its data indicate it has now entered a realm of space beyond the influence of our Sun. |
| But the US space agency (Nasa) says there is still some doubt about this. | But the US space agency (Nasa) says there is still some doubt about this. |
| Voyager is currently moving more than 18 billion km from Earth, or 123 times the distance between our planet and the Sun. | Voyager is currently moving more than 18 billion km from Earth, or 123 times the distance between our planet and the Sun. |
| The claim is made in a soon-to-be published paper in the journal Geophysical Research Letters. | The claim is made in a soon-to-be published paper in the journal Geophysical Research Letters. |
| The spacecraft has been monitoring changes in its environment for some time that have suggested it is about to cross the Solar System's border - the so-called heliopause. | The spacecraft has been monitoring changes in its environment for some time that have suggested it is about to cross the Solar System's border - the so-called heliopause. |
| Cosmic ray detection | Cosmic ray detection |
| It has been detecting a rise in the number of high-energy particles, or cosmic rays, coming towards it from interstellar space, while at the same time recording a decline in the intensity of energetic particles coming from behind, from our Sun. | It has been detecting a rise in the number of high-energy particles, or cosmic rays, coming towards it from interstellar space, while at the same time recording a decline in the intensity of energetic particles coming from behind, from our Sun. |
| A big change occurred on 25 August last year, which the GRL paper's authors say was like a "heliocliff". | A big change occurred on 25 August last year, which the GRL paper's authors say was like a "heliocliff". |
| "Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere," explained Prof Bill Webber from New Mexico State University in Las Cruces. | "Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere," explained Prof Bill Webber from New Mexico State University in Las Cruces. |
| Nasa says this view does not reflect the view of everyone working on the project, and Prof Weber acknowledges there is an ongoing debate. | Nasa says this view does not reflect the view of everyone working on the project, and Prof Weber acknowledges there is an ongoing debate. |
| The agency is expected to release a statement later on Tuesday. | The agency is expected to release a statement later on Tuesday. |
| Many researchers would like a long period with the data all pointing in one direction before calling the exit definitive. | Many researchers would like a long period with the data all pointing in one direction before calling the exit definitive. |
| Voyager-1 was launched on 5 September 1977, and its sister spacecraft, Voyager-2, on 20 August 1977. | Voyager-1 was launched on 5 September 1977, and its sister spacecraft, Voyager-2, on 20 August 1977. |
| The probes' initial goal was to survey the outer planets Jupiter, Saturn, Uranus and Neptune - a task they completed in 1989. | The probes' initial goal was to survey the outer planets Jupiter, Saturn, Uranus and Neptune - a task they completed in 1989. |
| They were then despatched towards deep space, in the general direction of the centre of our Milky Way Galaxy. | They were then despatched towards deep space, in the general direction of the centre of our Milky Way Galaxy. |
| Their plutonium power sources will stop generating electricity in about 10-15 years, at which point their instruments and transmitters will die. | Their plutonium power sources will stop generating electricity in about 10-15 years, at which point their instruments and transmitters will die. |
| Voyager-1 is on course to approach a star called AC +793888, but it will only get to within two light-years of it and it will be tens of thousands of years before it does so. | Voyager-1 is on course to approach a star called AC +793888, but it will only get to within two light-years of it and it will be tens of thousands of years before it does so. |