Friday, 1 April 2011

MIT Kavli Institute for Astrophysics and Space Research

"Development of the space station is as inevitable as the rising of the sun; man has already poked his nose into space and he is not likely to pull it back . . . ."
— Werner von Braun, 1952.~
MIT instrument finds surprises at solar system's edge

David Chandler, MIT News Office

December 10, 2007

Where are the Voyagers?

Interstellar Mission.
The twin Voyager 1 and 2 spacecraft continue exploring where nothing from Earth has flown before. In the 33rd year after their 1977 launches, they each are much farther away from Earth and the Sun than Pluto. Voyager 1 and 2 are now in the "Heliosheath" - the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas. Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network (DSN).

The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain. And beyond.

Edited and Add By:

Arip Nurahman

Department of Physic Faculty of Sciences and Mathematics
Indonesia University of Education


Follower Open Course Ware at MIT-Harvard University, Cambridge. USA.

The Voyager 2 spacecraft's Plasma Science instrument, developed at MIT in the 1970s, has turned up surprising revelations about the boundary zone that marks the edge of the sun's influence in space.

The unexpected findings emerged in the last few weeks as the spacecraft traversed the termination shock wave formed when the flow of particles constantly streaming out from the sun--the solar wind--slams into the surrounding thin gas that fills the space between stars.

The first surprise is that there is an unexpectedly strong magnetic field in that surrounding interstellar region, generated by currents in that incredibly tenuous gas. This magnetic field is squashing the bubble of out flowing gas from the sun, distorting it from the uniform spherical shape space physicists had expected to find.

A second surprise also emerged from Voyager 2's passage through the solar system's outer edge: Just outside that boundary the temperature, although hotter than inside, was ten times cooler than expected. Theorists had to scramble to come up with an explanation for the unanticipated chilling effect.

"It's a different kind of shockwave than we've seen anywhere else," says John Richardson, principal investigator for the Plasma Physics instrument and a Principal Research Scientist at MIT's Kavli Institute for Astrophysics and Space Science. The unexpected coolness, theorists now think, is caused by energy going into particles that are hotter than those that can be measured by the MIT plasma instrument.

Richardson will be taking part in a press conference reporting the new findings on Monday, Dec. 10, at a meeting of the American Geophysical Union in San Francisco.

The Voyager 1 and 2 spacecraft were designed primarily to study the planets Jupiter and Saturn and their moons. After launch, Voyager 2's path was adjusted to take it past Uranus and Neptune as well. Although the craft were only built for a five-year mission, both are still working well three decades later.

"We were incredibly lucky to have it last 30 years," says John Belcher, professor of physics at MIT and former principal investigator for the Voyager Plasma Science instrument. The craft is now expected to keep working until about 2020, and still has important scientific objectives ahead.

It is now passing through a boundary zone called the heliosheath, a region where the solar wind interacts with the surrounding interstellar medium. But sometime in the next decade, it will cross a final edge, called the heliopause, where the sun's outflow of particles ends. At that point, it will be able to measure characteristics of the interstellar medium, for the first time, in a region unaffected by the solar wind and the sun's magnetism.

Although Voyager 1 had already crossed the termination shockwave three years ago, the MIT Plasma Science instrument on that spacecraft had stopped working, so the spacecraft could only indirectly detect the end of the sun's influence.

But with Voyager 2, the Plasma Science instrument not only detected the boundary, making detailed measurements of the solar wind's temperature, speed and density as the spacecraft crossed through it, but it actually encountered the shockwave repeatedly. Because the outflow of the solar wind varies with changes in the sun's activity level, building up during large solar flares and quieting during lulls in sunspot activity, the boundary itself pulsates in and out. These pulsations can wash across the craft multiple times, just as a boat landing onshore may cross the ocean's edge multiple times as waves crash in and then recede.

While Voyager 1 apparently made a single crossing, Voyager 2 apparently crossed the boundary five times, producing a wealth of new data. It's even possible that if there are large variations in that solar outflow, the shock layer "could push past Voyager again," says Richardson. "That would give us some idea of how elastic the shock is" -- that is, how far out these pulsations may stretch. Until and unless such detections are made, "we only have models" of how great such variations might be, he says.

Voyager 2 is now 7.879 billion miles from Earth, traveling away at almost 35,000 miles per hour. Voyager 1 is 9.797 billion miles away, going more than 38,000 mph.

The Plasma Science instrument was developed by the late Professor Herbert Bridge and Alan Lazarus, a senior research scientist in the Department of Physics and MIT's Kavli Institute for Astrophysics and Space Science. NASA has sponsored the work.

MIT Kavli Institute for Astrophysics and Space Research

About the MKI  
Founded in 1965, formerly the Center for Space Research (CSR), the MIT Kavli Institute for Astrophysics and Space Research (MKI) at the Massachusetts Institute of Technology is an interdepartmental center that supports research in space science and engineering, astronomy and astrophysics. MKI plays a leading role in the design, construction and utilization of instruments placed aboard space vehicles launched by NASA or other agencies. The Institute's projects draw upon the interests and expertise of scientists and engineers from several MIT departments, thus affording a wide array of opportunities for both students and faculty. Experimental programs are supplemented by closely related programs of ground-based research, by theoretical investigations, and by laboratory development of instrumentation for space-based and ground-based experiments. MKI is located at 70 Vassar St. in the building named after the MIT Ph.D. graduate and NASA astronaut Ronald McNair.

The Director   Professor Jacqueline Hewitt, Professor of Physics at MIT, is the Director of the MKI.

Affiliated Departments and
  Department of Physics
Department of Earth Atmospheric and Planetary Sciences
Department of Electrical Engineering and Computer Science
Department of Aeronautics and Astronautics
Lincoln Laboratory


  Chandra X-ray Center (MKI)
Magellan Observatory (MKI)
Haystack Observatory (MIT)
Millstone Observatory (MIT)
Wallace Observatory (MIT)

How to reach us   The MKI's headquarters and Director's office are located in Building 37 of the MIT Campus at 70 Vassar Street, Cambridge, MA 02139.
We are a short walk from the Kendall Square subway stop, located on the eastern edge of the MIT campus.
For walking directions from the MBTA Kendall T stop to MKI please check here. To reach the MIT/MKI with other means of transportation check here.
MIT Campus Map showing MKI Centers, nearby hotels and Kendall T stop.

  MIT Kavli Institute for Astrophysics and Space Research
77 Massachusetts Avenue, 37-287
Cambridge, MA 02139
Telephone: (617) 253-7501
Fax: (617) 253-0861

  MIT Kavli Institute for Astrophysics and Space Research
77 Massachusetts Avenue, 37-241
Cambridge, MA 02139
Telephone: (617) 253-7501
Fax: (617) 253-3111


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