At first glance, it looks like something from an alien autopsy. Under the flickering lights of the operating room of a top-secret government agency, a strange organ cut out of an abnormally shaped chest cavity, the tendrils of the veins dropped to the floor, dripping viscous mucus. (Anyone at X-Com?)
But no, that’s just our solar system.
This strange and fascinating shape is actually a graphic representation of the appearance of the solar system, or the magnetic bubbles surrounding the solar system. It represents the heliosphere, which is a huge bubble carved into space by the continuous flow of the sun.
They call it the “deflated croissant”
The problem with accurately measuring the heliosphere is that we are in it. Its edge distance exceeds 16 billion kilometers (10 billion miles). Only because of this pair of Voyager spacecraft can we obtain any data from outside the solar circle. Voyager 1 left space and entered interstellar space in August 2012, while Voyager 2 performed the same operation in November 2019.
NASA’s IBEX or the Instellar Boundary Explorer are dedicated to researching the heliosphere. There are complex interactions between the heliosphere and the interstellar space, which is a region called “menopause”. IBEX studies so-called high-energy neutral atoms. They are produced when cosmic rays outside the solar system meet charged particles in the solar system. Since these high-energy neutral atoms are produced by interacting with the interstellar medium (ISM), they can be used as a proxy for measuring the edge of the heliosphere.
However, the data from these interactions is very complex. It must be entered into a computer model to make any sensible predictions about the nature and shape of the heliosphere. NASA and the National Science Foundation (NSF) funded a work that made it meaningful, the SHIELD Drive Science Center at Boston University.
A study published earlier this year presented some new results about the heliosphere. Its title is “Small, circular heliosphere suggested by a magnetohydrodynamic model that absorbs ions.” The main author is Merav Opher, professor of astronomy at Boston University. The research was published in the journal Natural Astronomy.
Scientists once thought that the shape of the heliosphere was a bit like a comet. When our solar system moves in space, the outflow of the sun will encounter the ISM, forming a bow impact or bow wave at the front edge, and a spiral tail at the back edge, reminiscent of the tail of a comet.
The author explained in the paper: “For the past six centuries, people have been exploring the shape of the heliosphere.” “Since the pioneering work of Baranov and Malama, people have agreed that daylight The layer is shaped like a comet.”
But this new study shows us a different heliosphere. The authors point out that recent evidence suggests that the heliosphere contains two jet-like structures.
In addition to the IBEX data, the researchers also used data from Cassini and New Horizons in their new study. They are both planetary missions, but they still contribute data on the solar system. Take Cassini as an example, which measured particles that interacted with the ISM and bounced back into the inner solar system. They explained: “The Cassini’s observations of high-energy neutral atoms further show that the heliosphere has no tails.”
New Vision measures the so-called Pickup Ion (PUI). PUI is a key part of this research. They are created when the sun passes through a partially ionized medium. They exchange electric charges with the solar wind to generate a large number of heat absorption ions (PUI), whose temperature is different from that of the solar wind ions.
When Voyager 2 crossed the border into interstellar space, it indicated that the pressure of the heliosheath was governed by these PUIs. But at the time, there was no research on how PUI shapes the heliosphere. This is what this research did, and this is how we get this strange new image of the heliosphere.
In the paper, the author explained: “The new model not only reproduces the characteristics of the PUI based on the New Horizons observations, but also reproduces the solar wind ions based on the Voyager 2 spacecraft observations and the external sun-like magnetic field data Voyager 1 and Travel The heliosphere of person 2.”
PUI is much hotter than other particles in the solar wind, and this difference is the key to this work.
“There are two fluids mixed together. Lead ion is a very cold component, and one is a hotter component,” the lead author Opher said in the press release. “If you have some cold fluids and hot fluids and put them in space, they will not mix-they will mainly develop separately. What we did is to separate these two components of the solar wind and simulate the final formation 3D shape of the heliosphere.”
What we got was not very good, neat shape. Instead of a spherical extension with a tail, we have a deflated croissant shape. The bulbous organic appearance looks like some kind of organ.
“As absorbed ions dominate thermodynamics, everything is spherical. However, because they leave the system soon beyond the termination impact, the entire solar layer gradually becomes thinner.” Opher said.
Although graphically speaking, this new heliospheric image is very interesting, but it is also scientifically important. That’s because the heliosphere plays an important role.
Outside the solar circle, other high-energy events in the solar system produce cosmic rays. Cosmic rays are high-energy protons and atomic nuclei, which move in space at a relativistic speed. Things like supernovae make them, and they spread out in all directions.
Cosmic rays are dangerous, and the heliosphere is our barrier against them. The heliosphere absorbs about 75% of the cosmic rays in the direction we are heading, but the rays passing through may cause great damage. On Earth, our magnetosphere and atmosphere mostly protect us from cosmic rays. But for satellites, spacecraft, and astronauts, the danger is real.
Cosmic rays not only damage electronic equipment, but exposure to electronic equipment also increases the risk of cancer among astronauts. And they are so tall that it is difficult to isolate astronauts from them. Due to the increased risk of cancer, cosmic rays are one of the main dangers of long-term space flight.
There is also some evidence that as the solar system moved relative to the plane of the Milky Way, the increase in cosmic rays led to past extinctions. Some researchers also believe that past supernova explosions exposed the Earth to higher levels of cosmic rays, which may have triggered the extinction of Pliocene marine giant animals. But many studies are controversial.
A better understanding of our own heliosphere may also help us understand the habitability of exoplanets. Cosmic ray radiation may make planets uninhabitable, even if we find these planets in the “Goldlock zone” around distant stars. As we gain a better understanding of the shape and function of our own heliosphere, we can apply this knowledge to other solar systems, thus providing us with a more sophisticated way to study habitability and life.
As far as the current situation is concerned, we don’t know enough about our own heliosphere (including its shape) to accurately characterize other heliospheres.
But the upcoming NASA mission should help. It is called IMAP or interplanetary mapping and acceleration probe. IMAP is scheduled to be launched in 2024, and it will map particles flowing back to Earth from the heliospheric boundary.
The DRIVE Science Center will play a role in the mission of IMAP. Opher and his colleagues at DRIVE are creating a testable heliosphere model in time for IMAP deployment in 2024. Their model will contain more detailed predictions of the shape and other characteristics of the heliosphere. Then, scientists can use IMAP observations to test.
The author wrote in the conclusion of the paper: “Future remote sensing and in-situ measurements will be able to test the authenticity of a more circular heliosphere.” “…Future missions such as interstellar mapping and acceleration probes will be more advanced than current missions. The high energy returns to the ENA (high-energy neutral atom, what PUI becomes after the charge exchange) mapping, so it will be able to explore the ENA from deep into the tail of the heliosphere. Therefore, the global structure of the heliosphere will be further explored and will be tested Our model.”