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New evidence shows that our neighbors in space are full of hydrogen



New evidence shows that our neighbors in space are full of hydrogen

When NASA̵

7;s New Horizons spacecraft was 280,000 miles (450,000 kilometers) away, the color global panorama of Pluto was enhanced. Image Credit: NASA/JHUAPL/SwRI

Only two Voyager spacecraft have been there, and the supersonic travel lasted more than 30 years. It crosses the rocky Kuiper belt, far beyond the orbit of Pluto, and four times that distance. This field is marked only by an invisible magnetic boundary, and is the end of the sun-dominated space: the closest range of interstellar space.


In this starless land, the 100 billion stars of the Milky Way quarreled with the ancient remnants of the Big Bang, emitting particles and light. This mixture is the material between stars, called the interstellar medium. Its content records the distant past of our solar system and may predict its future.

Measurements from NASA’s New Horizons spacecraft are revising our estimate of a key characteristic of the interstellar medium: how thick it is.Findings published today Astrophysical Journal Shared some new observations that the local interstellar medium has 40% more hydrogen atoms than previous studies suggested. The result unified many measurements that were originally different from each other and provided new ideas for our neighbors in space.

Through the interstellar fog

Just as the earth moves around the sun, our entire solar system travels through the Milky Way at a speed of more than 50,000 mph. When we traverse the fog of interstellar particles, we are shielded by magnetic bubbles called the magnetosphere around the sun. A lot of interstellar gas flows around this bubble, but not all.

Our heliosphere repels charged particles, which are guided by a magnetic field. But more than half of the local interstellar gas is neutral, which means they have a balanced number of protons and electrons. When we cultivated them, the three-dimensional interstellar immediately penetrated through, adding volume to the solar wind.

Eric Christian, a space physicist at NASA’s Goddard Space Flight Center, said: “It’s like you are running in a thick fog and you are accumulating water.” “When you run, your clothes are soaked. This slows you down.”

Soon after these interstellar atoms drifted into our heliosphere, they were interrupted by sunlight and hit by solar wind particles. Many people lost electrons in the turbulence and became positively charged “pickup ions”. Although these new particle swarms have changed, they are accompanied by the secret of fog.

Pavel Swazina, a postdoctoral researcher at Princeton University and the lead author of the study, said: “We did not directly observe interstellar atoms from New Horizons, but we can observe these absorbing ions.” “They are deprived of electrons, but We know that they came to us as neutral atoms from outside the solar circle.”

New evidence shows that our neighbors in space are full of hydrogen

Animation of the heliosphere.Image credit: NASA’s Goddard Space Flight Center/Concept Image Laboratory/Walter Feimer

NASA’s “New Horizons” spacecraft was launched in January 2006 and is the most suitable one to measure them. Now, five years have passed since its meeting point with Pluto, where it captured the first close-up image of a dwarf planet, and today, it ventures through the Kuiper belt at the edge of our solar system, where the absorbed ions are the freshest. The solar wind or SWAP instrument around Pluto of the spacecraft can detect these pickup ions and distinguish them from the normal solar wind by their higher energy.

The amount of absorbed ions detected by New Horizons reveals the thickness of the fog we are passing through. Just like when a jogger is wet in a thicker fog, the more ions observed in New Horizons, the denser the interstellar fog must be.

Different measurements

Swaczyna used SWAP measurements to obtain the density of neutral hydrogen at the end of the electric shock, when the solar wind was close to the interstellar medium and suddenly slowed down. After months of careful inspection and testing, they found that the number was 0.127 particles per cubic centimeter, or, in a space the size of a quart of milk, there are about 120 hydrogen atoms.

This result confirms a 2001 study that used Voyager 2 (approximately 4 billion miles) to measure the deceleration speed of the solar wind when it reached the spacecraft. The main reason for the deceleration is the intervention of interstellar medium particles, indicating that the interstellar hydrogen density matches. There are about 120 hydrogen atoms in a quart-sized space.

However, the new research brings together a different number. Scientists used data from NASA’s Ulysses mission (a little closer to the sun than Jupiter) to measure the pickup ions and estimate the density of about 85 hydrogen atoms in quart space. A few years later, another study combining Ulysses and Voyager data found similar results.

Swaczyna said: “You know, if you find a difference from your previous job, you will naturally start looking for errors.”

But after some digging, the new number began to look like the correct number. New horizon measurement is more suitable for observations based on distant stars. On the other hand, Ulysses’ measurements have a shortcoming: they are closer to the sun, where they absorb very little ions and the measurements are more uncertain.

Christian said: “The observations of ions absorbed by the inner heliosphere have been filtered through billions of miles.” “Most of the new horizons will bring about huge changes.”

New evidence shows that our neighbors in space are full of hydrogen

The ribbon is still one of IBEX’s greatest discoveries. It refers to the huge diagonal high-energy neutral particles drawn across the front of a hollow sphere. Credit: NASA / IBEX

Regarding the Ulysses/Voyager merger result, Swaczyna noticed that a figure in the calculation was out of date and was 35% lower than the current consensus value. Recalculations using currently accepted values ​​can make them roughly match the New Horizons measurement results and the 2001 study.

Arik Posner, author of a 2001 study at NASA headquarters in Washington, D.C., said: “The confirmation of our almost forgotten results in the past is surprising. This is a fairly simple method that we have overcome to measure solar wind deceleration. . Since then more complex research has been conducted, but this is not the case.”

New land

The increase from 85 atoms in a quart of milk to 120 may not seem like much. However, in model-based sciences like solar physics, adjustments to a number affect each other.

The new estimates may help explain one of the biggest mysteries in solar physics in recent years. Soon after NASA’s “Interstellar Boundary Probe” or IBEX mission returned to its first complete data set, scientists noticed a strange band of high-energy particles from the front edge of our heliosphere. They call it the “IBEX functional area”.

Christian said: “The function of IBEX has brought us a big surprise. This structure is located at the edge of our solar system 1 billion miles wide and 10 billion miles long. No one knows.” “But even if we develop why we use it. Model, all models indicate that it should not be as bright as it is now.”

“The 40% increase in interstellar density observed in this study is absolutely critical,” said David McComas, a professor of astrophysics science at Princeton University, the lead researcher of NASA’s IBEX mission and the co-author of the study. Embedded in the denser parts of interstellar space, and compared with the actual observations of IBEX, it can also explain major errors in our simulation results.”

But, most importantly, the result can be a better understanding of our local stellar community.

Swaczyna said: “This is the first time we have observed instrument pickup ions at such a great distance, and our image of the local interstellar medium matches the images of other astronomical observations.” “This is a good sign.”


The solar wind around Pluto confirms that the solar wind is getting further and further away from the sun


More information:
P.Swaczyna et al. The density of neutral hydrogen near the solar interstellar, Astrophysical Journal (2020). DOI: 10.3847 / 1538-4357 / abb80a

Citation: New evidence that space is full of hydrogen (October 31, 2020) was retrieved from https://phys.org/news/2020-10-evidence-neighborhood-space-stuffed-hydrogen.html on October 31, 2020

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