Voyager 2 proves solar system is squashed

Dec 10, 2007
Voyager 2 proves solar system is squashed
Artist's concept of our solar system. Image credit: NASA

NASA's Voyager 2 spacecraft has followed its twin Voyager 1 into the solar system's final frontier, a vast region at the edge of our solar system where the solar wind runs up against the thin gas between the stars.

However, Voyager 2 took a different path, entering this region, called the heliosheath, on August 30, 2007. Because Voyager 2 crossed the heliosheath boundary, called the solar wind termination shock, about 10 billion miles away from Voyager 1 and almost a billion miles closer to the sun, it confirmed that our solar system is “squashed” or “dented”– that the bubble carved into interstellar space by the solar wind is not perfectly round. Where Voyager 2 made its crossing, the bubble is pushed in closer to the sun by the local interstellar magnetic field.

“Voyager 2 continues its journey of discovery, crossing the termination shock multiple times as it entered the outermost layer of the giant heliospheric bubble surrounding the Sun and joined Voyager 1 in the last leg of the race to interstellar space.” said Voyager Project Scientist Dr. Edward Stone of the California Institute of Technology, Pasadena, Calif.

The solar wind is a thin gas of electrically charged particles (plasma) blown into space by the sun. The solar wind blows in all directions, carving a bubble into interstellar space that extends past the orbit of Pluto. This bubble is called the heliosphere, and Voyager 1 was the first spacecraft to explore its outer layer, when it crossed into the heliosheath in December 2004. As Voyager 1 made this historic passage, it encountered the shock wave that surrounds our solar system called the solar wind termination shock, where the solar wind is abruptly slowed by pressure from the gas and magnetic field in interstellar space.

Even though Voyager 2 is the second spacecraft to cross the shock, it is scientifically exciting for a couple of reasons. The Voyager 2 spacecraft has a working Plasma Science instrument that can directly measure the velocity, density and temperature of the solar wind. This instrument is no longer working on Voyager 1 and estimates of the solar wind speed had to be made indirectly. Secondly, Voyager 1 may have had only a single shock crossing and it happened during a data gap. But Voyager 2 had at least five shock crossings over a couple of days (the shock “sloshes” back and forth like surf on a beach, allowing multiple crossings) and three of them are clearly in the data. They show us an unusual shock.

In a normal shock wave, fast-moving material slows down and forms a denser, hotter region as it encounters an obstacle. However, Voyager 2 found a much lower temperature beyond the shock than was predicted. This probably indicates that the energy is being transferred to cosmic ray particles that were accelerated to high speeds at the shock.

"The important new data describing the termination shock are still being pondered, but it is clear that Voyager has once again surprised us," said Dr. Eric Christian, Voyager Program Scientist at NASA Headquarters, Washington.

The two Voyager spacecraft will be the only source of local observations of this distant but highly interesting region for years to come. But in the summer of 2008, NASA will be launching a mission specifically designed to globally image the termination shock and heliosheath remotely from Earth orbit. The Interstellar Boundary Explorer (IBEX), led by Dr. David McComas of the Southwest Research Institute in San Antonio, Texas, will use energetic neutral atoms (ENAs) to create all-sky maps at various energies of the interaction of the heliosphere with interstellar space. ENAs are formed when energetic electrically-charged particles “steal” an electron from another particle. Once neutral, they travel straight, unaffected by the solar magnetic field. IBEX will detect some of the particles that happen to be headed towards the Earth, and the number and energy of the particles coming from all different directions will tell us much more about the overall structure of the interaction between the heliosphere and interstellar space.

Results on the Voyager 2 shock crossing from the entire Voyager science team are being presented at the Fall 2007 meeting of the American Geophysical Union in San Francisco. The Voyagers were built by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., which continues to operate both spacecraft.

Source: Goddard Space Flight Center

Explore further: Quest for extraterrestrial life not over, experts say

add to favorites email to friend print save as pdf

Related Stories

Voyager observes magnetic field fluctuations in heliosheath

Oct 29, 2012

As they near the outer reaches of the solar system, for the past several years the two Voyager spacecraft have been sending back observations that challenge scientists' views of the physics at the edge of the heliosphere, ...

No more solar wind for Voyager 1 spacecraft

Dec 13, 2010

(PhysOrg.com) -- The 33-year odyssey of NASA's Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind.

The Stars My Destination

Nov 10, 2009

The Voyager spacecraft are now in the outermost layer of the heliosphere, traveling toward interstellar space - the first man-made spacecraft to travel such a vast distance from Earth.

The sounds of interstellar space

Nov 04, 2013

Scifi movies are sometimes criticized when explosions in the void make noise. As the old saying goes, "in space, no one can hear you scream." Without air there is no sound.

Recommended for you

Quest for extraterrestrial life not over, experts say

Apr 18, 2014

The discovery of an Earth-sized planet in the "habitable" zone of a distant star, though exciting, is still a long way from pointing to the existence of extraterrestrial life, experts said Friday. ...

Continents may be a key feature of Super-Earths

Apr 18, 2014

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Exoplanets soon to gleam in the eye of NESSI

Apr 18, 2014

(Phys.org) —The New Mexico Exoplanet Spectroscopic Survey Instrument (NESSI) will soon get its first "taste" of exoplanets, helping astronomers decipher their chemical composition. Exoplanets are planets ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

Maningo
3 / 5 (2) Dec 11, 2007

A few months ago astrophysicist Russ Humphreys published a solution to the Pioneer Anomaly.
earls
2.5 / 5 (2) Dec 11, 2007
Yeah, half the registered members of this site have too.

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.