NASA Space Place – The Shape Of The Solar System

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in June, 2017.

By Marcus Woo

2013february2_spaceplaceWhen Stamatios (Tom) Krimigis was selected for the Voyager mission in 1971, he became the team’s youngest principal investigator of an instrument, responsible for the Low Energy Charged Particles (LECP) instrument. It would measure the ions coursing around and between the planets, as well as those beyond. Little did he know, though, that more than 40 years later, both Voyager 1 and 2 still would be speeding through space, continuing to literally reshape our view of the solar system.

The solar system is enclosed in a vast bubble, carved out by the solar wind blowing against the gas of the interstellar medium. For more than half a century, scientists thought that as the sun moved through the galaxy, the interstellar medium would push back on the heliosphere, elongating the bubble and giving it a pointy, comet-like tail similar to the magnetospheres—bubbles formed by magnetic fields—surrounding Earth and most of the other planets

“We in the heliophysics community have lived with this picture for 55 years,” said Krimigis, of The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “And we did that because we didn’t have any data. It was all theory.”

But now, he and his colleagues have the data. New measurements from Voyager and the Cassini spacecraft suggest that the bubble isn’t pointy after all. It’s spherical.

Their analysis relies on measuring high-speed particles from the heliosphere boundary. There, the heated ions from the solar wind can strike neutral atoms coming from the interstellar medium and snatch away an electron. Those ions become neutral atoms, and ricochet back toward the sun and the planets, uninhibited by the interplanetary magnetic field.

Voyager is now at the edge of the heliosphere, where its LECP instrument can detect those solar-wind ions. The researchers found that the number of measured ions rise and fall with increased and decreased solar activity, matching the 11-year solar cycle, showing that the particles are indeed originating from the sun.

Meanwhile, Cassini, which launched 20 years after Voyager in 1997, has been measuring those neutral atoms bouncing back, using another instrument led by Krimigis, the Magnetosphere Imaging Instrument (MIMI). Between 2003 and 2014, the number of measured atoms soared and dropped in the same way as the ions, revealing that the latter begat the former. The neutral atoms must therefore come from the edge of the heliosphere.

If the heliosphere were comet-shaped, atoms from the tail would take longer to arrive at MIMI than those from the head. But the measurements from MIMI, which can detect incoming atoms from all directions, were the same everywhere. This suggests the distance to the heliosphere is the same every which way. The heliosphere, then, must be round, upending most scientists’ prior assumptions.

It’s a discovery more than four decades in the making. As Cassini ends its mission this year, the Voyager spacecraft will continue blazing through interstellar space, their remarkable longevity having been essential for revealing the heliosphere’s shape.

“Without them,” Krimigis says, “we wouldn’t be able to do any of this.”

To teach kids about the Voyager mission, visit the NASA Space Place:

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Caption: New data from NASA’s Cassini and Voyager show that the heliosphere — the bubble of the sun’s magnetic influence that surrounds the solar system — may be much more compact and rounded than previously thought. The image on the left shows a compact model of the heliosphere, supported by this latest data, while the image on the right shows an alternate model with an extended tail. The main difference is the new model’s lack of a trailing, comet-like tail on one side of the heliosphere. This tail is shown in the old model in light blue. Image credits: Dialynas, et al. (left); NASA (right)

About NASA Space Place

With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages everyone to get excited about science and technology. Visit (facebook|twitter) to explore space and Earth science!

“Confronting The Big Questions: Highlights of Modern Astronomy” – Starting July 17th At Coursera

Greetings, fellow astrophiles!

The following was forwarded along to several local astronomy group mail lists by CNYO/SAS/ASRAS member Dr. David Wormuth. The Coursera course, “Confronting The Big Questions: Highlights of Modern Astronomy,” is hosted right in our own neighborhood – featuring University of Rochester professor of astrophysics (and NPR science mainstay) Dr. Adam Frank (twitter).

You’ve no excuse for not learning something interesting this summer.

Click on the following link for all of the details and to enroll – Coursera will certainly not complain if you wish to enroll through the paying option ($49) to support the cause, but you can also sign up for the free option (without a completion certificate at the end) when you enroll for the course.

From the course website:

About this Course

An introduction to modern astronomy’s most important questions. The four sections of the course are Planets and Life in The Universe; The Life of Stars; Galaxies and Their Environments; The History of The Universe.

The MOST Offers FREE Summer Camp! Spots Limited!

Greetings, fellow astrophiles!

This in from the TACNY email list about a great summer opportunity at The MOST for students starting 9th grade this fall.

Students graduating 8th grade can learn about
environmental science by conducting field experiments

If you have a child who’s entering ninth grade in the fall, The MOST has the perfect camp to keep them thinking this summer: Honeywell Summer Science Week.

Students spend July 10-14 out in the field conducting real scientific research as they learn about factors that stress the Onondaga Lake watershed. They also learn what Honeywell has done to clean up the lake, which was once considered the most polluted lake in the country. Then students come back for a day July 19 to discuss their research and present what they learned.

Best of all, thanks to the generous sponsorship from Honeywell, the camp is FREE to participants!

To apply for Honeywell Summer Science Week, contact Michael Amadori or Peter Plumley as soon as possible. There are only 15 spaces left!

Technology Alliance of Central New York

Founded in 1903 as the Technology Club of Syracuse, the nonprofit Technology Alliance of Central New York’s mission is to facilitate community awareness, appreciation, and education of technology; and to collaborate with like-minded organizations across Central New York.

For more information about TACNY, visit and their Facebook page.