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Voyager 1 Is an Interstellar Craft

the_sun_flareHard to over-emphasize just how historic this is: it has been confirmed that Voyager 1 has pierced the heliosphere and entered into interstellar space. Back in June I posted about a “mysterious region” at the edge of our solar system, which had scientists a little confused about Voyager’s location. Evidently, that confusion has been cleared away.

From the University of Iowa’s IowaNow website:

“On April 9, the Voyager 1 Plasma Wave instrument, built at the UI in the mid-1970s, began detecting locally generated waves, called electron plasma oscillations, at a frequency that corresponds to an electron density about 40 times greater than the density inside the heliosphere—the region of the sun’s influence,” says Gurnett. “The increased electron density is very close to the value scientists expected to find in the interstellar medium.

“This is the first solid evidence that Voyager 1 has crossed the heliopause, the boundary between the heliosphere, and interstellar space,” says Gurnett, principal investigator for the plasma wave instrument.

At age 36, Voyager 1 is the most distant human-made object at more than 11.6 billion miles from the sun, or about 125 astronomical units.

“At that distance it takes more than 17 hours for a radio signal to travel from the spacecraft to one of NASA’s Deep Space Network antennas. The signal strength is so incredibly weak that it takes both a 230-foot and a 110-foot-diameter antenna to receive our highest resolution data,” Gurnett says.

That makes Voyager 1 the first human-made spacecraft to enter interstellar space. Though we can’t see or feel what that’s like, an instrument on the probe captured the sound of vibrating plasma there, and sent it back to Earth. You can listen to that here (or at the bottom of this post).

National Geographic explains how scientists know Voyager 1 crossed over in a little more detail:

Knowing exactly where the solar wind ends and where interstellar space begins has been an open question among space scientists for more than four decades, says Stone.

Since an instrument for directly detecting that transition died in 1980, the researchers have had to rely on indirect measures of magnetic and electrical activity from other instruments aboard Voyager 1 to find an answer.

One key to identifying this boundary is the difference in the density of charged particles between the solar wind and interstellar space, as it is about 50 times greater in the latter region.

Looking at a pair of solar storms that caught up to the spacecraft last October and then again last April, Gurnett’s team reported that measured changes in electrical activity around Voyager correspond to interstellar space.

As the storms passed the spacecraft, they triggered spikes in electrical and radio waves that uniquely corresponded in frequency to the spacecraft having entered the more densely charged interstellar space.

Based on that increase, the team extrapolated the entry date for Voyager 1 into interstellar space as August 25, 2012.

Voyager still has some life left in it too. The probe is not expected to completely lose power until 2025, though instruments on board will likely fail before that time. Remember, Voyager 1 was designed in the early ’70s and was launched on September 5th, 1977. As Suzanne Dodd—the Voyager project manager—points out, your average smartphone has approximately 250,000 times more memory than Voyager 1 does, which makes its continuing operation seem all that more miraculous. Also makes me wonder what we’re doing with all that extra memory in our pockets.



Speed Bump at the Edge of the Solar System

voyager_trajectoryI haven’t posted any science-y articles to the blog in awhile, but today two caught my attention.

Voyager I, now in space for over 35 years, is just approaching the very edge of our solar system. Astronomers have expected some very particular things to happen once it crosses over into interstellar space. Only, those things aren’t happening at all, and nobody can say why for sure.


The first Voyager sped out of the solar system in 1980 and it has since been edging closer and closer to interstellar space. The probe is currently out more than 120 times the distance between the Earth and the sun.

Scientists initially thought that Voyager’s transition into this new realm, where effects from the rest of the galaxy become more pronounced, would be gradual and unexciting. But it’s proven to be far more complicated than anything researchers had imagined…

…it’s almost as if Voyager thought it was going outside but instead found itself standing in the foyer of the sun’s home with an open door that allows wind to blow in from the galaxy. Not only were scientists not expecting this foyer to exist, they have no idea how long the probe will stay inside of it. Stone speculated that the probe could travel some months or years before it reaches interstellar space.

For the curious reader, 120 times the distance between the Earth and the sun is approximately 18.5 billion kilometers, or 11.5 billion miles. It’s hard to imagine such a distance, so think of it this way:  The speed of light is 299,792,458 meters per second. If you could travel that quickly, it would take more than 34 hours to go from the sun to Voyager I’s current position and back.

Or think of it in miles per hour: 300,000,000 meters per second is around 671 million miles per hour. You could get to Jupiter in about 40 minutes at that speed. Voyager I was launched on 5 September 1977, but its closest approach to Jupiter didn’t happen until 1979. It would take roughly a year to reach the Oort cloud.

It takes sunlight eight full minutes to reach the Earth.

Once you start to fix the distance in your head, Voyager I’s position becomes all the more amazing.

The other article that caught my attention concerns the formation exoplanets, and came via SETI’s Facebook page. It also puts our knowledge of the universe into perspective:

A team of researchers has discovered evidence that an extrasolar planet may be forming quite far from its star — about twice the distance Pluto is from our Sun. The planet lies inside a dusty, gaseous disk around a small red dwarf TW Hydrae, which is only about 55% of the mass of the Sun. The discovery adds to the ever-increasing variety of planetary systems in the Milky Way.

Planet formation far away from a small parent star is at odds with the conventional planet-making dogma. Under the most accepted scenario, planets form over tens of millions of years from the slow accretion of dust, rocks, and gas. That happens most easily close to the central star, where orbital timescales are short. Even under a disk instability scenario, in which planets can collapse quickly from the disk, it’s not clear such a low mass planet could form.

Carnegie astrophysicist Alan Boss, who works on disk instability models, said “If the mass of this suspected planet is as low as it seems to be, this presents a real puzzle. Theory would say that it cannot exist!”

But apparently it does exist. I’m excited by this kind of news because it demonstrates the versatility of planet formation in the universe. The more possible planets, the more places life could exist. And like lots of other people, I want to believe we’re not alone.