Tweet This
Credit: NASA/JPLArtist's concept of Voyager in flight.
“These missions do not need to be nearly as complex as Voyager, but they do need to have a much higher velocity so that we can get there sooner and reach much greater distances than Voyager 1 will achieve,” Don Gurnett, the principal investigator for the spacecraft’s plasma wave instrument and a physicist at the University of Iowa, told me.
It was Gurnett and colleagues’ own plasma wave instrument that confirmed that on August 25, 2012, Voyager 1 had indeed crossed over into interstellar space. Our observations were based on vibrations in the plasma caused by two shock waves that propagated into the interstellar medium from energetic solar flares at the Sun, he says. (A plasma is typically a superheated gas whose atoms have been stripped of some or all of its electrons. Yet unlike normal gas, is also electrically-conductive and subject to the forces of magnetism.) Since 2012, Voyager 1’s plasma instrument has detected three more such solar shock wave events.
Such distant plasma measurements have enabled Gurnett and colleagues to directly probe the interstellar medium. And for the first time they have a profile of the plasma density going outward into the interstellar medium from the heliopause. (The heliopause is a boundary of equilibrium between the influence of charged particles from the solar wind and particles, stellar winds and cosmic rays from the interstellar medium.)
But it was the frequency of vibrations that enabled Gurnett and colleagues to determine that in August 2012, the local plasma density at this distance was nearly a factor of fifty greater than the density of the solar plasma. Thus, it was consistent with densities expected of the local interstellar environment. In fact, the team determined that the plasma density in the local interstellar medium averages some one hundred thousand particles per cubic meter.
Gurnett says Voyager 1’s most exciting results are the extent to which shock waves from solar flares can propagate so far from the Sun and make major disturbances in the local interstellar medium.
“These shock waves continually stir up the local interstellar medium, causing noticeable perturbations in the local cosmic ray intensity,” said Gurnett. He says the fact that such flares can makes major disturbances so far from the Sun and stir up the local interstellar medium is Voyager 1’s most surprising scientific result.
Voyager 1 remains the most distant human-made object and is leaving the solar system at a rate of about 325 million miles per year. Voyager 1 is now at a distance of almost a light day or some 140 astronomical units (AU) or Earth-Sun distances.
“Fifty years ago, there was speculation that the solar wind streaming out from the Sun may just get gradually get absorbed as it diffuses into the interstellar medium, with no sharp boundary at all,” said Gurnett. “Now we know that it does form a distinct well-defined boundary.”
But he says what’s needed now are better measurements of the heliopause’s plasma using mass spectrometers. That would enable researchers to better understand the overall shape of our solar system’s heliopause.
NASA reports that Voyager 1 is expected to keep its current suite of science instruments on through 2021. But it will take another 300 years for it to finally reach our solar system’s Oort Cloud of comets. But it will take more than another 38,000 years before the craft comes close to another star.
In 40,272 A.D., NASA says Voyager 1 will come within 1.7 light years of the star AC+79 3888, in Ursa Minor (the Little Dipper).
Again, the moral of the story is that we need faster spacecraft.
NASA’s New Horizons mission to Pluto and beyond has already surpassed everyone’s expectations. But Gurnett says we really need what he terms a “quantum leap in rocket performance,” to make faster scientific progress in understanding the nearby interstellar medium.
“Remote sensing measurement can provide some information, but [such] measurements are very difficult to interpret and we need in situ measurements for confirmation,” said Gurnett.
">Forty years after launch, NASA’s Voyager 1 spacecraft is still alive and kicking --- now heading in the direction of the constellation of Ophiuchus --- its camera long turned off. Four of its ten original instruments are all still operating and sending back meaningful data. Yet rather than bask in its continued glory, one of Voyager 1’s original science team members says now is the time to mount a handful of new such missions.
Those would be ones designed to solidify our understanding of the local interstellar environment that would head out of our solar system from several different directions and at much higher velocities than Voyager 1.
Credit: NASA/JPLArtist's concept of Voyager in flight.
“These missions do not need to be nearly as complex as Voyager, but they do need to have a much higher velocity so that we can get there sooner and reach much greater distances than Voyager 1 will achieve,” Don Gurnett, the principal investigator for the spacecraft’s plasma wave instrument and a physicist at the University of Iowa, told me.
It was Gurnett and colleagues’ own plasma wave instrument that confirmed that on August 25, 2012, Voyager 1 had indeed crossed over into interstellar space. Our observations were based on vibrations in the plasma caused by two shock waves that propagated into the interstellar medium from energetic solar flares at the Sun, he says. (A plasma is typically a superheated gas whose atoms have been stripped of some or all of its electrons. Yet unlike normal gas, is also electrically-conductive and subject to the forces of magnetism.) Since 2012, Voyager 1’s plasma instrument has detected three more such solar shock wave events.
Such distant plasma measurements have enabled Gurnett and colleagues to directly probe the interstellar medium. And for the first time they have a profile of the plasma density going outward into the interstellar medium from the heliopause. (The heliopause is a boundary of equilibrium between the influence of charged particles from the solar wind and particles, stellar winds and cosmic rays from the interstellar medium.)
But it was the frequency of vibrations that enabled Gurnett and colleagues to determine that in August 2012, the local plasma density at this distance was nearly a factor of fifty greater than the density of the solar plasma. Thus, it was consistent with densities expected of the local interstellar environment. In fact, the team determined that the plasma density in the local interstellar medium averages some one hundred thousand particles per cubic meter.
Gurnett says Voyager 1’s most exciting results are the extent to which shock waves from solar flares can propagate so far from the Sun and make major disturbances in the local interstellar medium.
“These shock waves continually stir up the local interstellar medium, causing noticeable perturbations in the local cosmic ray intensity,” said Gurnett. He says the fact that such flares can makes major disturbances so far from the Sun and stir up the local interstellar medium is Voyager 1’s most surprising scientific result.
Voyager 1 remains the most distant human-made object and is leaving the solar system at a rate of about 325 million miles per year. Voyager 1 is now at a distance of almost a light day or some 140 astronomical units (AU) or Earth-Sun distances.
“Fifty years ago, there was speculation that the solar wind streaming out from the Sun may just get gradually get absorbed as it diffuses into the interstellar medium, with no sharp boundary at all,” said Gurnett. “Now we know that it does form a distinct well-defined boundary.”
But he says what’s needed now are better measurements of the heliopause’s plasma using mass spectrometers. That would enable researchers to better understand the overall shape of our solar system’s heliopause.
NASA reports that Voyager 1 is expected to keep its current suite of science instruments on through 2021. But it will take another 300 years for it to finally reach our solar system’s Oort Cloud of comets. But it will take more than another 38,000 years before the craft comes close to another star.
In 40,272 A.D., NASA says Voyager 1 will come within 1.7 light years of the star AC+79 3888, in Ursa Minor (the Little Dipper).
Again, the moral of the story is that we need faster spacecraft.
NASA’s New Horizons mission to Pluto and beyond has already surpassed everyone’s expectations. But Gurnett says we really need what he terms a “quantum leap in rocket performance,” to make faster scientific progress in understanding the nearby interstellar medium.
“Remote sensing measurement can provide some information, but [such] measurements are very difficult to interpret and we need in situ measurements for confirmation,” said Gurnett.
Read Again Voyager 1 Scientist Says NASA Needs New Interstellar Probes : http://ift.tt/2vgIP0ZBagikan Berita Ini
0 Response to "Voyager 1 Scientist Says NASA Needs New Interstellar Probes"
Post a Comment