NASA rocket to investigate the windshield of the solar system

NASA rocket to investigate the windshield of the solar system

An illustration of the heliosphere bombarded with cosmic rays from outside our solar system. Credit: NASA’s Goddard Space Flight Center / Conceptual Image Lab

Eleven billion kilometers away – more than four times the distance from us to Pluto – lies the boundary of our solar system’s magnetic bubble, the heliopause. Here the sun’s magnetic field sparkles like an invisible cobweb through space. Interstellar space begins.

“It really is the largest frontier of its kind we can study,” said Walt Harris, a space physicist at the University of Arizona in Tucson.

We still know little about what lies beyond this boundary. Fortunately, pieces of interstellar space can come to us, move through this boundary and through the solar system.

A new NASA mission will study light from interstellar particles that have drifted in our solar system to learn about the nearest parts of interstellar space. The mission, called the Spatial Heterodyne Interferometric Emission Line Dynamics Spectrometer, or SHIELDS, had its first opportunity on 19 April 2021 to launch aboard a suborbital rocket from the White Sands Missile Range in New Mexico.

Our entire solar system floats in a cluster of clouds, an area cleared by ancient supernova explosions. Astronomers call this region the Local Bubble, an elongated plot of about 300 light-years inside the spiral-shaped Orion arm of our Milky Way galaxy. It contains hundreds of stars, including our own Sun.

We sail this interstellar sea in our reliable vessel, the heliosphere, a much smaller (though still gigantic) magnetic bubble that is inflated by the sun. As we orbit the Sun, the solar system itself, wrapped in the heliosphere, is tossed about 23,000 km per hour by the Local Bubble. Interstellar particles throw the nose of our heliosphere like rain against a windshield.

Our heliosphere looks more like a rubber raft than a wooden sailboat: the environment takes shape. It compresses at pressure points, extending where it yields. Exactly how and where our heliosphere’s liner deforms gives us clues about the nature of interstellar space beyond. This boundary – and any deformities in it – is what Walt Harris, lead investigator for the SHIELDS mission, is after.

SHIELDS is a telescope that will launch aboard a resounding rocket, a small vehicle that flies into space for a few minutes of observation time before falling back to earth. Harris’ team launched an earlier version of the telescope in 2014 as part of the HYPE mission, and after modifying the design, they are ready to start again.

SHIELDS measures light from a special population of hydrogen atoms originally coming from interstellar space. These atoms are neutral, with a balanced number of protons and electrons. Neutral atoms can cross magnetic field lines, so that they seep through the heliopause and into our solar system almost intact – but not completely.

NASA rocket to investigate the windshield of the solar system

Illustration of the local bubble. Credit: NASA’s Goddard Space Flight Center

The small effects of this border crossing are the key to SHIELDS ‘technique. Charged particles flow around the heliopause and form a barrier. Neutral particles from interstellar space must move through this glove, changing their paths. SHIELDS are designed to reconstruct the orbits of the neutral particles to determine where they come from and what they see along the way.

A few minutes after launch, SHIELDS reaches its peak about 300 kilometers from the ground, far above the absorbing effect of the earth’s atmosphere. By pointing the telescope at the nose of the heliosphere, it will detect light-emitting hydrogen atoms. To measure how the light’s wavelength stretches or contracts, shows the velocity of the particles. All things considered, SHIELDS will compile a map to reconstruct the shape and varying density of matter during the helio pause.

Harris hopes the data can answer tantalizing questions about interstellar space.

Astronomers, for example, think that the Local Bubble as a whole is about 1/10 as dense as most of the rest of the galaxy’s main disk. But we do not know the details – is the matter evenly distributed in the local bubble or surrounded in dense bags by nothing?

“There’s a lot of uncertainty about the fine structure of the interstellar medium – our maps are kind of crude,” Harris said. “We know the general outlines of these clouds, but we do not know what happens in them.”

Astronomers also do not know much about the magnetic field of the galaxy. But it should leave a mark on our heliosphere that can detect SHIELDS and compress the heliopause in a specific way, based on its strength and orientation.

Finally, it can be a useful guide for the (distant) future to learn what our current plot of interstellar space looks like. Our solar system only passes through our current space. In about 50,000 years we’re on our way out of the Local Bubble and who knows what.

“We do not really know what that other cloud is like, and we do not know what happens if you cross a border into that cloud,” Harris said. “There’s a lot of interest in understanding what we’re likely to experience as our solar system makes that transition.”

Not that our solar system has not done this before. Over the past four billion years, Harris explained, the earth has passed through various interstellar environments. It’s just that we’re there now, with the scientific tools to document it.

“We’re just trying to understand our place in the galaxy, and where we’re headed in the future,” Harris said.


NASA sounding rocket to study interplanetary medium


Provided by NASA’s Goddard Space Flight Center

Quotation: NASA rocket to investigate the windshield of the solar system (2021, April 16), detected on April 18, 2021 from https://phys.org/news/2021-04-nasa-rocket-survey-solar-windshield.html

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