Andrew Yee[_1_]
August 10th 08, 09:56 PM
News Office
Massachusetts Institute of Technology
July 7, 2008
MIT instrument studies edge of sun's bubble
Spacecraft gives data on space beyond sun's influence
David Chandler, MIT News Office
The Voyager 1 and 2 spacecraft have traveled beyond the edges of the bubble
in space where the sun's constant outward wind of particles and radiation
slams into the interstellar medium that pervades our galaxy. The first
scientific reports on what the Voyagers found there appears this week in the
journal Nature.
The deep-space probes, which were designed mainly to study the outer planets
Jupiter, Saturn, Uranus and Neptune, have now traveled more than 8 billion
miles away from the Earth. Voyager 1 is now more than 94 Astronomical Units
away (one AU is the average distance from the Earth to the sun, or 93
million miles), and Voyager 2 is more than 84 AU. Because they are leaving
the solar system on paths that are about 45 degrees apart, the data reveals
details about the shape of the bubble created by the solar wind. The fact
that they crossed the edge of the solar outflow -- a region called the
boundary shock -- at different distances out from the sun proved that this
bubble is squashed rather than being a symmetrical sphere.
Some of the data that revealed this boundary region comes from a set of
magnetic field sensors developed and built at MIT back in the 1970s, based
on an earlier MIT instrument sent on Explorer 1 in 1961. John Richardson,
Principal Research Scientist at MIT's Kavli Institute for Astrophysics and
Space Science, is a co-author of the two Nature papers, and John Belcher,
professor of physics at MIT and former principal investigator for the
Voyager Plasma Science instrument, is a co-author of one of them.
"We have never made direct measurements in the interstellar medium, the
material between the stars," Belcher says, "because the sun's supersonically
expanding atmosphere blows a bubble in the local interstellar medium whose
radius is 100 times the distance from the sun to the Earth."
"It's starting to feel the interstellar wind," Richardson says of the
fast-receding spacecraft, which is already more than three times as far from
the sun as the solar system's outermost planets. "The interstellar wind is
coming at us at 26 km per second," he says.
Sometime about a decade from now, Belcher says, Voyager 2 "will be through
the shocked solar wind and into the interstellar medium proper. This is the
material out of which the sun condensed, which has never been explored
before."
Nobody knows much about that interstellar medium, such as what the density
of hydrogen atoms is in that incredibly tenuous vacuum. "We will be able to
deduce that better" once Voyager reaches it, Richardson says. "We'll also
get a first look at cosmic rays that haven't been influenced by the sun's
magnetic field, once we get outside," and thus learn more about the origins
of these extremely fast-moving particles, he says. "That's one of our major
scientific goals."
On a personal note, Belcher said that the creators of the MIT plasma
instrument all wrote their names inside it before it was sent to be attached
to the spacecraft. "My father had a 7th grade education, my generation was
the first in the family to go to college," he says, "and my name is on a
spaceship that will eventually reach the stars and probably last longer than
the Earth itself!"
An earlier report on what Voyager 2 found was presented at a scientific
meeting last December.
The work was funded by NASA.
IMAGE CAPTION:
[http://web.mit.edu/newsoffice/2008/heliosphere-nasa-enlarged.html]
The scale of the heliosphere and nearby galactic neighborhood. The solar
system and its nearby galactic neighborhood are illustrated here on a
logarithmic scale extending (from < 1 to) 1 million Astornomical Units (AU).
Image: NASA/JPL
Massachusetts Institute of Technology
July 7, 2008
MIT instrument studies edge of sun's bubble
Spacecraft gives data on space beyond sun's influence
David Chandler, MIT News Office
The Voyager 1 and 2 spacecraft have traveled beyond the edges of the bubble
in space where the sun's constant outward wind of particles and radiation
slams into the interstellar medium that pervades our galaxy. The first
scientific reports on what the Voyagers found there appears this week in the
journal Nature.
The deep-space probes, which were designed mainly to study the outer planets
Jupiter, Saturn, Uranus and Neptune, have now traveled more than 8 billion
miles away from the Earth. Voyager 1 is now more than 94 Astronomical Units
away (one AU is the average distance from the Earth to the sun, or 93
million miles), and Voyager 2 is more than 84 AU. Because they are leaving
the solar system on paths that are about 45 degrees apart, the data reveals
details about the shape of the bubble created by the solar wind. The fact
that they crossed the edge of the solar outflow -- a region called the
boundary shock -- at different distances out from the sun proved that this
bubble is squashed rather than being a symmetrical sphere.
Some of the data that revealed this boundary region comes from a set of
magnetic field sensors developed and built at MIT back in the 1970s, based
on an earlier MIT instrument sent on Explorer 1 in 1961. John Richardson,
Principal Research Scientist at MIT's Kavli Institute for Astrophysics and
Space Science, is a co-author of the two Nature papers, and John Belcher,
professor of physics at MIT and former principal investigator for the
Voyager Plasma Science instrument, is a co-author of one of them.
"We have never made direct measurements in the interstellar medium, the
material between the stars," Belcher says, "because the sun's supersonically
expanding atmosphere blows a bubble in the local interstellar medium whose
radius is 100 times the distance from the sun to the Earth."
"It's starting to feel the interstellar wind," Richardson says of the
fast-receding spacecraft, which is already more than three times as far from
the sun as the solar system's outermost planets. "The interstellar wind is
coming at us at 26 km per second," he says.
Sometime about a decade from now, Belcher says, Voyager 2 "will be through
the shocked solar wind and into the interstellar medium proper. This is the
material out of which the sun condensed, which has never been explored
before."
Nobody knows much about that interstellar medium, such as what the density
of hydrogen atoms is in that incredibly tenuous vacuum. "We will be able to
deduce that better" once Voyager reaches it, Richardson says. "We'll also
get a first look at cosmic rays that haven't been influenced by the sun's
magnetic field, once we get outside," and thus learn more about the origins
of these extremely fast-moving particles, he says. "That's one of our major
scientific goals."
On a personal note, Belcher said that the creators of the MIT plasma
instrument all wrote their names inside it before it was sent to be attached
to the spacecraft. "My father had a 7th grade education, my generation was
the first in the family to go to college," he says, "and my name is on a
spaceship that will eventually reach the stars and probably last longer than
the Earth itself!"
An earlier report on what Voyager 2 found was presented at a scientific
meeting last December.
The work was funded by NASA.
IMAGE CAPTION:
[http://web.mit.edu/newsoffice/2008/heliosphere-nasa-enlarged.html]
The scale of the heliosphere and nearby galactic neighborhood. The solar
system and its nearby galactic neighborhood are illustrated here on a
logarithmic scale extending (from < 1 to) 1 million Astornomical Units (AU).
Image: NASA/JPL