heliosheath Archives

August 7, 2012December 23, 2015 by Jason Major

Winds of Change at the Edge of the Solar System

As the venerable Voyager 1 spacecraft hurtles ever outward, breaking through the very borders of our solar system at staggering speeds upwards of 35,000 mph, it’s sending back information about the curious region of space where the Sun’s outward flow of energetic particles meets the more intense cosmic radiation beyond — a boundary called the heliosheath.

Voyager 1 has been traveling through this region for the past seven years, all the while its instruments registering gradually increasing levels of cosmic ray particles. But recently the levels have been jumping up and down, indicating something new is going on… perhaps Voyager 1 is finally busting through the breakers of our Sun’s cosmic bay into the open ocean of interstellar space?

Data sent from Voyager 1 — a trip that currently takes the information nearly 17 hours to make — have shown steadily increasing levels of cosmic radiation as the spacecraft moves farther from the Sun. But on July 28, the levels of high-energy cosmic particles detected by Voyager jumped by 5 percent, with levels of lower-energy radiation from the Sun dropping by nearly half later the same day. Within three days both levels had returned to their previous states.

The last time such a jump in levels occurred was in May — and that spike took a week to happen.

“The increase and the decrease are sharper than we’ve seen before, but that’s also what we said about the May data,” said Edward Stone, the Voyager project scientist based at the California Institute of Technology. “The data are changing in ways that we didn’t expect, but Voyager has always surprised us with new discoveries.”

The graph below shows the jump in cosmic particles detected starting May 2012.

Over 11 billion miles (18 billion km) from home, Voyager 1 has been cruising through space since its launch on September 5, 1977. Its twin, Voyager 2, was launched two weeks earlier and is currently 9.3 billion miles (15 billion km) away. Both spacecraft are healthy and continue to communicate with Earth, and will both eventually break through the borders of our solar system and enter true interstellar space. If they are still operational when that happens — and there’s no reason that they shouldn’t be — we will finally get a sense of what conditions are like “out there”.

Although Voyager 1 is registering intriguing fluctuations in radiation from both inside and outside the Solar System, it’s not quite there yet.

“Our two veteran Voyager spacecraft are hale and healthy as they near the 35th anniversary of their launch,” said Suzanne Dodd, Voyager project manager based at JPL in Pasadena. “We know they will cross into interstellar space. It’s just a question of when.”

Read more about Voyager’s ongoing breakout here.

“We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space.”

– Edward Stone, Voyager project scientist, Caltech

Images: NASA/JPL-Caltech

June 15, 2012December 23, 2015 by Jason Major

Voyager 1 Breaking Through the Borders of the Solar System

After almost 35 years traveling at over 35,000 mph, the venerable (and still operational!) Voyager 1 spacecraft is truly breaking through to the other side, crossing the outermost boundaries of our solar system into interstellar space — over 11 billion miles from home.

Data received from Voyager 1 — a trip that currently takes the information 16 hours and 38 minutes to make — reveal steadily increasing levels of cosmic radiation, indicating that the spacecraft is leaving the relatively protected bubble of the Sun’s influence and venturing into the wild and wooly space beyond.

From the JPL press release:

“The laws of physics say that someday Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the solar system’s frontier.”

The data making the 16-hour-38 minute, 11.1-billion-mile (17.8-billion-kilometer), journey from Voyager 1 to antennas of NASA’s Deep Space Network on Earth detail the number of charged particles measured by the two High Energy telescopes aboard the 34-year-old spacecraft. These energetic particles were generated when stars in our cosmic neighborhood went supernova.

“From January 2009 to January 2012, there had been a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering,” said Stone. “More recently, we have seen very rapid escalation in that part of the energy spectrum. Beginning on May 7, the cosmic ray hits have increased five percent in a week and nine percent in a month.”

This marked increase is one of a triad of data sets which need to make significant swings of the needle to indicate a new era in space exploration. The second important measure from the spacecraft’s two telescopes is the intensity of energetic particles generated inside the heliosphere, the bubble of charged particles the sun blows around itself. While there has been a slow decline in the measurements of these energetic particles, they have not dropped off precipitously, which could be expected when Voyager breaks through the solar boundary.

“When the Voyagers launched in 1977, the space age was all of 20 years old. Many of us on the team dreamed of reaching interstellar space, but we really had no way of knowing how long a journey it would be — or if these two vehicles that we invested so much time and energy in would operate long enough to reach it.”

– Ed Stone, Voyager project scientist, Caltech

Aged Voyager 1 Does In-flight Gymnastics for Science

Voyager 1 Mission — Artist impression of Voyager 1, the first probe to traverse the heliosheath (NASA)

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She might be old, but she’s still got it where it counts. The 33-year old Voyager 1 probe, flying out near the edge of the solar system conducted a roll program, spinning 70 degrees counterclockwise, and held the position by spinning gyroscopes for two hours, 33 minutes. Voyager performed its in-flight gymnastics on March 7, 2011 and scientists hope the maneuver will help answer the question of which direction is the sun’s stream of charged particles turns when it nears the edge of the solar system.

“Even though Voyager 1 has been traveling through the solar system for 33 years, it is still a limber enough gymnast to do acrobatics we haven’t asked it to do in 21 years,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory. “It executed the maneuver without a hitch, and we look forward to doing it a few more times to allow the scientists to gather the data they need.”

Voyager needed to get in the right orientation to enable its Low Energy Charged Particle instrument to gather data.

The last time either of the two Voyager spacecraft rolled and stopped in a gyro-controlled orientation was Feb. 14, 1990, when Voyager 1 snapped a family portrait of the planets. See the image here.

The two Voyager spacecraft are traveling through a turbulent area known as the heliosheath,the outer shell of a bubble around our solar system created by the solar wind. The solar wind is traveling outward from the sun at a million miles per hour. Scientists think the wind must turn as it approaches the heliosheath where it makes contact with the interstellar wind — , which originates in the region between stars.

In June 2010, when Voyager 1 was about 17 billion kilometers (about 11 billion miles) away from the sun, data from the Low Energy Charged Particle instrument began to show that the net outward flow of the solar wind was zero. That zero reading has continued since. The Voyager science team doesn’t think the wind has disappeared in that area, but perhaps has just turned a corner. But where does it go from there: up, down or to the side?

“Because the direction of the solar wind has changed and its radial speed has dropped to zero, we have to change the orientation of Voyager 1 so the Low Energy Charged Particle instrument can act like a kind of weather vane to see which way the wind is now blowing,” said Edward Stone, Voyager project manager. “Knowing the strength and direction of the wind is critical to understanding the shape of our solar bubble and estimating how much farther it is to the edge of interstellar space.”

Voyager engineers performed a test roll and hold back on Feb. 2, just to make sure the spacecraft was still capable. No problems for the old girl, and spacecraft had no problem in reorienting itself and locking back onto its guide star, Alpha Centauri.

This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Image credit: NASA/JPL-Caltech

There will be five more of these maneuvers over the next seven days, with the longest hold lasting three hours 50 minutes. The Voyager team plans to execute a series of weekly rolls for this purpose every three months.

Over the next few months, scientists will analyze the data.

“We do whatever we can to make sure the scientists get exactly the kinds of data they need, because only the Voyager spacecraft are still active in this exotic region of space,” said Jefferson Hall, Voyager mission operations manager at JPL. “We were delighted to see Voyager still has the capability to acquire unique science data in an area that won’t likely be traveled by other spacecraft for decades to come.”

Voyager 2 was launched on Aug. 20, 1977. Voyager 1 was launched on Sept. 5, 1977. On March 7, Voyager 1 was 17.4 billion kilometers (10.8 billion miles) away from the sun. Voyager 2 was 14.2 billion kilometers (8.8 billion miles) away from the sun, on a different trajectory.

The solar wind’s outward flow has not yet diminished to zero where Voyager 2 is exploring, but that may happen as the spacecraft approaches the edge of the bubble in the years ahead.

Voyager is just another good old girl.

Source: JPL