Voyager space probes enter the “foam zone”

New comet C/2011 L4 was discovered by Pan-STARRS, a 60-inch telescope that automatically searches the skies for objects that either move or change their brightness from night to night. Photo credit: Ernesto Guido and Giovanni Sostero.

Let’s begin with a bit of astro news. A new comet named C/2011 L4 (PANSTAARS)  was discovered on images taken by the Pan-STARRS 1 telescope at Haleakala, Hawaii on June 6. Currently the comet is exceedingly faint, but come April 2013 it may become as bright as 2nd magnitude and easily visible with the naked eye. Of course that’s a long way off, and the comet’s orbit is still being refined. We’ll have occasional updates in the months ahead. You’ll find more information in the Remanzacco Observatory blog maintained by Italian observers Giovanni Sostero and Ernesto Guido.

The supernova in the Whirlpool Galaxy on June 4. Credit: William Wiethoff

I got yet another look at supernova 2011 dh in the Whirlpool Galaxy (M51) last night. Even in moonlight, it was rather easy to see in my 10-inch telescope. The star continues to climb in brightness.

Using a chart from the American Association of Variable Star Observers (AAVSO), I estimated it at magnitude 12.9. That puts the supernova within range of 4 to 6-inch telescopes under dark skies. If you do have a scope that size, be patient. In a week,  the moon will be past full and out of the sky, and you’ll have a much easier time spotting it. And who knows – the supernova may shine even more brightly by then.


The Voyager space probes appear to have entered a strange realm of frothy magnetic bubbles at the edge of the solar system

The twin Voyager space probes, launched in the 1970s, were the first study the outer planets Jupiter, Saturn, Uranus and Neptune up close. They’re now about 9 billion miles away in the heliosheath, the “border crossing” zone between the realm of the sun and the rest of the stars in the Milky Way galaxy. One day soon, the probes will leave the influence of the sun and enter true interstellar space.

The edge of the solar system appears frothy like these bubbles along a river's edge. But instead of water film enclosing air, the bubbles are made of magnetic energy enclosing regions of space. Photo: Bob King

Late this week, astronomer Merav Opher of Boston University, announced that the probes have entered a strange realm of magnetic bubbles at the solar system’s fringe. Each is about 100 million miles across or about the same distance Earth is from the sun.

“The sun’s magnetic field extends all the way to the edge of the solar system,” explains Opher. “Because the sun spins, its magnetic field becomes twisted and wrinkled, a bit like a ballerina’s skirt. Far, far away from the sun, where the Voyagers are now, the folds of the skirt bunch up.”

And when they bunch up, magnetic field lines, similar to those traced by iron filings around a magnet, criss-cross and reconnect – sometimes explosively – to form a froth of magnetic bubbles distinct from the rest of the sun’s magnetic field.

Old and new views of the heliosheath. Red and blue spirals are the gracefully curving magnetic field lines of the older view. New data from Voyager add a magnetic froth (inset) to the mix. Credit: NASA

The reason anyone should care about this is that the bubbles form a membrane of sorts that defines how our solar system interacts with the rest of the galaxy. Think of it as a cell wall that allows desirable chemicals inside and prevents undesirable materials from entering. In the case of magnetic bubbles, astronomers aren’t yet sure whether froth is a good absorber of powerful galactic cosmic rays or if these tiny, atom-sized cannonballs find it easier to penetrate such a porous shield.

Despite their name, cosmic rays are subatomic particles shot out from black holes and supernova explosions. They pack a huge wallop despite their tiny size, because they’re traveling at close to the speed of light. All their energy is bound up in speed or what physicists call kinetic energy. The vast majority are simple protons or hydrogen atom nuclei.

A collision between a cosmic ray particle and an atom in a photographic emulsion. Credit: NASA, Dr. David P. Stern

Cosmic rays pose a health hazard to astronauts on missions that would take them beyond the protective shield of Earth’s magnetic field. High speed protons can damage DNA and increase cancer risk.

Whether or not the solar system’s “foam zone” makes a good shield, it’s interesting to reflect on the fact that supernovas and other highly energetic processes that happen in distant corners of the universe can have so direct an effect on our bodies, when we leave the safety of Earth.

Those particles that do make it past our planet’s magnetic field strike the upper atmosphere, where they create showers of secondary, less energetic particles that dissipate the cosmic ray’s original energy. One of the coolest things I’ve ever experienced regarding cosmic rays was a muon detector set up by the University of Minnesota-Duluth physics club. Muons are subatomic particles similar to electrons but heavier that are produced in profusion when cosmic rays strike the upper atmosphere. Everytime a muon arrived at the detector, it made a little click. And yes, they kept coming all day long. I remember thinking how the universe, vast and distant as so much of it is, can touch you in very real ways.

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7 thoughts on “Voyager space probes enter the “foam zone”

  1. interesting article as usual. but an fyi. want you to know that i have two e-mail addresses that i use at different times. but either way, i’m still tom. also, i probably will soon change my nom de plume (or nom de guerre). the one i am using here has outlived its usefulness.

  2. Does the moons path around the horizon change like the sun does around the equinoxes? Does it have a shorter or longer “uptime”?

    • Hi Lars, if you mean the full moon, yes. The full moon in June and July takes a very low path across the southern sky and is up only a short amount of time compared the winter full moon. The sun is just the opposite. When the moon “rides low” the sun ride high. Since we’re near the solstice, the sun is near its highest point in the sky all year. Am I understanding your question correctly?

  3. What amazes me most is that we are still able to receive this kind of measurement data from the Voyager space probes – wonderful little machines out there, and fantastic receiving technology down here.

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