Pixel Planet Is Home Sweet Home

Voyager 1 celebrates its 35th year in space today. The probe was 3.7 billion miles from Earth and 32 degrees above the plane of the solar system when it took this photo in 1990. Earth is only 0.12 pixels wide. The fuzzy light in the images is scattered sunlight because Earth was very close to the Sun as seen from Voyager the same way Mercury appears close to the sun from Earth. Credit: NASA

This is one of my very favorite photos. Earth is tiny – less than a pixel wide – and looks so tentative as if any moment it might disappear in the reflective glare of the sun. It was taken on February 14, 1990 at the end of its primary mission from 3.7 billion miles miles away. NASA mission controllers commanded the probe to spin around and take a family portrait of the solar system.

Voyager’s wide-angle view showing the overexposed sun. The inset photos are photos of the Earth and Venus taken with the narrow-angle lens. Credit: NASA

Carl Sagan, planetary astronomer and creator of the inspirational Cosmos TV series, made the suggestion. Here’s what he had to say about the picture. It recalls Apollo astronaut Neil Armstrong’s vision of Earth:

“From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.”

Both Voyager 1 and its sister probe Voyager 2 are located in the heliosheath near the boundary between interstellar and solar space called the heliopause. The wind of particles constantly streaming from the sun creates a vast bubble of solar influence called the heliosphere. Credit: NASA/JPL-Caltech

Voyager 1 left the Earth 35 years ago today on September 4, 1977 and took our eyes all the way to Jupiter, Saturn and beyond. Today it’s 11.3 billion miles from home near the edge of the solar system, still within the cocoon of the sun’s influence but just barely. Within the next year or two the probe will sail through the heliopause or boundary of the solar system and into interstellar space.

In May this year Voyager 1 detected an increase in cosmic rays from outside the sun’s realm, a sure sign it’s close to leaving the solar womb. These high-speed particles cut loose during explosive events like supernovae and bound around the galaxy until zipping through the heliopause and heading for Earth. They collide with atoms in the rarefied upper atmosphere and create showers of small, secondary particles that head toward the ground. Only a small number of those ever make it down that far, but they and ones further up are responsible for a portion of our planet’s natural background radiation.

Artist’s concept of the two Van Allen radiation belts with Earth nestled at their center. The belts, which extend up the way up to 65 degrees north and south latitudes, contain high-energy protons and electrons, many of which originate from the sun. The blue and red arcs indicate north and south magnetic polarities. Credit: T. Benesch and J. Carns for the NASA Science Mission Directorate

While we’re on the topic of radiation, NASA recently launched the twin Radiation Belt Storm Probes into Earth’s Van Allen radiation belts last Thursday. The belts are two donut-shaped regions filled with high energy particles that surround the Earth. Most of the particles stream in from the sun and get trapped by the planet’s magnetic field. The inner belt, a mix of protons and electrons, can reach down as low as 600 miles; the outer belt is filled with fast-moving electrons and extends outward some 37,000 miles from the surface of Earth.

James Van Allen (center) along with rocket scientists William Pickering (left) and Wernher von Braun hold a model of the Explorer 1 satellite, which was launched on January 31, 1958. Credit: NASA

No one knew about any of this activity before 1958. That’s when the U.S. successfully launched Explorer 1, our country’s first satellite. James Van Allen, a space scientist at the University of Iowa, insisted that a Geiger counter be placed on board to measure cosmic rays in space. He got his way and the counter shot off the scale as it orbited the Earth.

Space scientists came to realize through this and subsequent satellite missions that the “empty” space near our planet was buzzing with activity. The belts were named after their discoverer.

The Radiation Belt Storm probes are identical craft that will fly in separate orbits through the inner and outer Van Allen belts. Since most of the subatomic particles there arrived from the sun, solar activity causes all kinds of interesting fluctuations in the belts. Sometimes they’re chalk full of electrons and can affect satellite electronics; other times the belts are nearly empty and quiet. The probes will sample magnetic and electrical fields in the belts and count how many and what kinds of particles are flying around up there. Scientists hope the data will help better predict space weather which includes things like northern lights. Stay tuned.

8 Responses

  1. Hunter

    Great post on Voyager 1 Bob! Still chugging along after all these years! And to think, each Voyager craft only has 68 kilobytes of computer memory. The smallest iPod – an 8-gigabyte iPod Nano – is 100,000 times more powerful.

    Keep up the nice posts Bob!

    1. astrobob

      Hey Hunter, thanks a lot! And thanks for your comparison of Voyager’s computing power to today’s consumer electronics.

  2. Andrés Díaz V

    Hi Bob, sorry for bother you but I need to make you a question about something different of this subject. In our group about astronomic events one member post about a big object that appear in the SOHO solar observatory near sun. I thing that is one of the planets mercury, venus or mars but the member suggest that is something totally different, Can you give your opinion about please?… Thanks for advance…

    1. astrobob

      Hi Andres,
      Thanks for writing. The image in the SOHO coronagraph photo is the planet Mercury, currently located about 5 degrees NNW of the sun.

  3. Mike

    Carl Sagen took lots of jabs form his program and even for things he didn’t say. Carl was very good at explaining in common terms complex science and bringing it to a wide audience. Cosmos was a little hokey at times (the pretend spacecraft and control panel he manipulated comes to mind and I would bet was not his idea) yet it was a great series explaining various principals that make up our life experiences in the natural world. Thanks Carl. May you rest in peace sir.

    Thanks Bob for this. After 12 more years we would not even register in a photo from their vantage point. I can recall some of the controversy about “….sending too much information about us out to evil alien civilizations to find us and invade!” If they were smart they would stay away. :^>

    Take care Bob!

    1. astrobob

      Yes, I remember the fears at the time of sending too much information of our whereabouts. That assumes they’d want to destroy us like most aliens seem to want to do in the movies.

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