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Distance
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Voyagers Grand Tour

The first "geminis" in history to venture deep into the solar system, Voyager 1 and Voyager 2, launched in 1977 aboard Titan-Centaur rockets, taking advantage of a rare geometric alignment of the outer planets.

Voyager 1 flew by Jupiter and Saturn before continuing on toward interstellar space. Voyager 2 also flew by Jupiter and Saturn and proceeded to explore Uranus and Neptune. To date Voyager 2 is the only spacecraft to have visited those outer planets. Both spacecrafts are currently in the "Heliosheath" -- the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas. From this farthest distance ever travelled by human-made spacecrafts, the Voyager satellites are still transmitting scientific data that help understand the physics of the outmost sphere of the solar system. At this distance the sun is just a tiny spot of light.

Nowadays, the Hubble Space Telescope delivers images of the planets in nearly the same resolution, but taken from 550 kilometers above Earth's surface. Nevertheless, when the Grand Tour ended in 1989 with Voyager 2's fly-by of Neptune the text books of planetary science have been rewritten, while the world was stunned by fascination of the first close-up images of the outer planets and their numerous moons.

Unfortunately, Voyager 2 could not make it to Pluto because it was far out of range for another swing by maneuver towards Pluto's orbital position at that time. NASA's New Horizons spacecraft is currently on its way to Pluto and the Kuiper Belt to fill the gap.


Please visit NASA's fascinating Voyager site to learn more.


Update: Historic Journey Into Interstellar Space

Update: Voyager 1 at the Final Frontier


Update: The 34 Years old Voyager Twins still Amaze with Exciting Data

Voyager at Triton in 1989 Voyager 2 at Neptune's moon Triton in 1989

June 2012 - Voyager 1 is currently closest to a frontier that we call the boundary of our solar system with interstellar space, a region free of any physical influence from our Sun, virtually, "where no other man-made probe has gone before".

Known as the heliosphere, the sun blows a bubble of charged particles around itself extending towards where Voyager 1 is currently en-route. The spacecraft is equipped with two high-energy telescopes which measure the number of particles and send the data on a journey of 16 hours and 38 minutes back to NASA's Deep Space Network on Earth for analysis.

As of June 14, 2012, the latest results indicate a significantly increased intensity of charged particles. The Voyager scientists therefore concluded that the probe is on the edge of our solar system. Though the date of transit into interstellar space is still unknown, Voyager 1 will soon be the first human-made explorer cruising outside the solar system and telling us where exactly the boundary is located and what the space between the stars is made of. Voyager 1 will then open the gate to a new era of space exploration.



Indicators

At the boundary of the heliosphere, the particle wind from the sun is calm while its magnetic field is piled up, and higher-energy particles from inside our solar system leak into interstellar space. It is expected that the direction of the magnetic field lines, which run east-west within, will change directions towards north-south beyond the frontier.

At or near the boundary the number of charged particles from the sun should decline while the amount of cosmic rays from outside should increase. Indeed, Voyager has been measuring declining energetic particles originating from both, inside and outside our solar system as if the particles are leaking out into interstellar space. Simultaneously, Voyager registered a notable increase of high-energy electrons originating from our galaxy diffusing into our solar system.



Voyager Joined Forces with Saturn's Cassini

Actually, Voyager data has previously been combined with measurements from the magnetospheric imaging instrument on board the Cassini spacecraft which collects data on neutral atoms streaming into our solar system.

Interstellar Boundary

A best estimate indicates that the boundary between interstellar space and the bubble of charged particles is approximately 11 billion miles (18 billion kilometers, or 120AUs). Since Voyager 1 is already nearly 11 billion miles out there, it could cross into interstellar space at any time - in astronomical terms - yet, considering that Voyager 1 travels a billion miles every three years, we may not have to wait that long. Power and fuel will last until 2020. By then, Voyager 1 should be 12.4 billion miles (19.9 billion km) away in interstellar space.



The Voyagers are Heading Towards the Stars

In about 40,000 years, Voyager 1 will drift within 1.6 light-years (9.3 trillion miles) of Gliese 445, a faint, currently 17.6 light-years remote, red star in the constellation of Camelopardalis, near the northern star Polaris. Behold, Voyager has no warp thrusters, why in such a short time?

While Voyager 1 closes on Gliese 445, the high proper motion star is approaching the Sun at high radial velocity of 119 km/s. Therefore, at the time Voyager 1 passes Gliese 445, the star will be merely 3.45 light-years from the Sun.

Interstellar Boundary Voyager 1 passing the star Gliese 445 in the center of the image.

In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles, about the distance between the sun and the closest star, Alpha Centauri) from Sirius, the brightest star in the sky out there in Canis Major at a distance of 8.6 light-years.

Behold, why does it take 296,000 years to Sirius, while it takes just 40,000 years to Gliese 445 which is at half of the distance of Sirius? Well, while Gliese 445 approaches the sun at a rate of over 100 km/s, Sirius approaches the sun at merely 7.6 km/s. Also remember that Voyager is predicted to pass Sirius at a distance of more than 4 light-years.


Reference and further reading...


Terms



NASA Video: Voyager Finds Magnetic Foam at the edge of the Solar System.
• Heliosphere

The region, or rather a bubble blown by the sun around itself, which is dominated by the Sun's magnetic field and particles contained in the solar wind. The heliosphere embraces:

• Termination Shock

The region where the supersonic solar wind will be held back from further expansion by the interstellar wind.

• Heliosheath

The region between the Termination Shock and the Heliospause, which is still influenced by the Sun's magnetic field and particles contained in the solar wind.

• Heliospause

The region where the Sun's influence wanes and the beginning of interstellar space can be sensed. Beyond the heliospause lies interstellar space.



Update: Voyager Encounters a New Region at the Outer Solar System

New region at the solar system edge Image credit: NASA/JPL-Caltech

December 2011 - Thanks to the Voyagers we did not only venture to the planets. Voyager 1 has now entered the outmost region of the solar system while it still transmits data of high scientific value. It is now within a space which is called the "Stagnation Region" where the influence of the sun, such as solar wind and intensity of energetic particles decline.

"Although Voyager I is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager I is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years", wrote NASA in its December 5th release.

It is most likely that Voyager 1 will send data from which we will learn how far our solar system reaches and what interstellar space is actually made of. At present, the probe is at a distance from the sun about 24 times that of Jupiter and about four times further out than Pluto. A fine return of investment! Voyager 2 is not as close to the edge of the solar system as Voyager 1. Voyager 2 is about 9.1 billion miles (14.5 billion kilometers) away from the sun.

Reference and further reading...
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