What is this? New astrophysical research highlights a significant cosmic event two million years ago when the solar system passed through a dense interstellar cloud. This possibly altered Earth’s climate by exposing it to enhanced cosmic radiation, supported by increased isotopes found in geological records

Earth was a very different place around two million years ago, with our early human ancestors living alongside saber-toothed tigers, mastodons, and enormous rodents. And, depending on where they were, they may have been cold: Earth had fallen into a deep freeze, with multiple ice ages coming and going until about 12,000 years ago. Scientists theorize that ice ages occur for a number of reasons, including the planet’s tilt and rotation, shifting plate tectonics, volcanic eruptions, and carbon dioxide levels in the atmosphere.

But what if drastic changes like these are not only a result of Earth’s environment, but also the sun’s location in the galaxy?

Impact of the Sun’s Galactic Journey

In a new paper published today (June 10) in Nature Astronomy, lead author and astrophysicist Merav Opher—an astronomy professor at Boston University and fellow at Harvard Radcliffe Institute— found evidence that some two million years ago, the solar system encountered an interstellar cloud so dense that it could have interfered with the sun’s solar wind. Opher and her co-authors believe this shows that the sun’s location in space might shape Earth’s history more than previously considered

Geological and Cosmic Evidence

If that had happened, says Opher, Earth would have been fully exposed to the interstellar medium, where gas and dust mix with the leftover atomic elements of exploded stars, including iron and plutonium. Normally, the heliosphere filters out most of these radioactive particles. But without protection, they can easily reach Earth.

In one scenario, the solar system passed through a dense cloud of interstellar material, causing Earth to ice over. In the other, the solar system passed through less dense clouds that destroyed the planet’s protective ozone layer, raising levels of harmful ultraviolet radiation.

The possibilities, based on modeling but not yet supported by solid evidence, were presented in the journal Geophysical Research Letters

Computer models show dramatic climate change can be caused by interstellar dust accumulating in Earth’s atmosphere during the solar system’s immersion into a dense space cloud,” said Alex Pavlov, principal author of both papers and a researcher at the University of Colorado, Boulder

What is interstellar space in simple words?

Interstellar space is the area between the stars, but it is far from empty. It contains vast quantities of neutrinos, charged particles, atoms, molecules, dark matter and photons ranging from the highest-energy radiation to the sluggish light of the cosmic microwave background (CMB) albeit rather sparsely spread out

Why is it called interstellar space?

At first glance, the answer seems simple. ‘Inter’ means between. ‘Stellar’ refers to stars. “Easy!” you think, “Interstellar space is the part of space that exists between stars

What is the meaning of heliopause?

heliopause. / hē′lē-ə-pôz′ / The region surrounding the solar system at which pressure from the outgoing solar wind equals the pressure from the interstellar medium (made up mostly of hydrogen and helium), and the solar wind can penetrate no further

What is beyond the heliopause?

Outside the heliopause, would be a turbulent region caused by the pressure of the advancing heliopause against the interstellar medium. However, the velocity of the solar wind relative to the interstellar medium is probably too low for a bow shock

Has Voyager passed the heliopause?

On Aug. 25, 2012, Voyager 1 flew beyond the heliopause and entered interstellar space, making it the first human-made object to explore this new territory. At the time, it was at a distance of about 122 AU, or about 11 billion miles (18 billion kilometers) from the sun

What is the heliosphere and why is it important?

The Sun sends out a constant flow of solar material called the solar wind, which creates a bubble around the planets called the heliosphere. The heliosphere acts as a shield that protects the planets from interstellar radiation

What is the difference between heliosphere and interstellar space?

This schematic shows our solar bubble moving through nearby interstellar space, or the space between stars. Interstellar space is shown in blue because it is filled with plasma, or ionized gas, that has a lower temperature than what is inside our solar bubble, also known as the heliosphere

Is Earth inside the heliosphere?

Earth has spheres (land, water, air, living things) and Earth is part of the Sun system, called the heliosphere. Most systems are inside the Earth, but the heliosphere is all around Earth and the entire solar system.

Does the Milky Way have a heliosphere?

Our corner of the universe, the solar system, is nestled inside the Milky Way galaxy, home to more than 100 billion stars. The solar system is encased in a bubble called the heliosphere, which separates us from the vast galaxy beyond – and some of its harsh space radiation

What would happen without the heliosphere?

As the heliosphere determines the environment in which the solar system, including our planet exists, its study is assuming ever greater importance. Without it, we probably wouldn’t be here

Is the heliosphere magnetic?

heliosphere, the region surrounding the Sun and the solar system that is filled with the solar magnetic field and the protons and electrons of the solar wind. The solar magnetic field in the heliosphere has a dipole structure

What is next to heliosphere?

Look to the solar wind!

This place is called the heliopause. It marks the end of a region created by our Sun that is called the heliosphere. The Sun creates this heliosphere by sending a constant flow of particles and a magnetic field out into space at over 670,000 miles per hour. This stream is called the ‘solar wind

What is called an interstellar cloud?

A nebula is an interstellar cloud of dust and other ionized gases resulting from the explosion of a star. Nebulae are clouds made up mainly of hydrogen gas and dust particles. Suggest Corrections

Interstellar clouds are dense regions of gas, plasma, and dust that exist in the space between star systems in galaxies. They are held together by gravity and can be formed from gas and dust particles from red giants in their later life

Some believe that interstellar clouds may have impacted Earth’s climate in the past. For example, a 2024 Newscientist article suggests that the solar system may have passed through a dense, cold interstellar cloud 2–3 million years ago, exposing Earth to the interstellar environment and outside the protective heliosphere. This could have led to an increase in hydrogen in the atmosphere and increased radiation, which may have had a substantial impact on Earth’s climate

Between 2 and 3 million years ago, the solar system encountered turbulence on a galactic scale, colliding with a dense interstellar cloud that may have altered both the climate and evolution on Earth

In a new paper published in Nature Astronomy, lead author and astrophysicist Merav Opher—an astronomy professor at Boston University and fellow at Harvard Radcliffe Institute— found evidence that some two million years ago, the solar system encountered an interstellar cloud so dense that it could have interfered with the sun’s solar wind. Opher and her co-authors believe this shows that the sun’s location in space might shape Earth’s history more than previously considered.  

Our whole solar system is swathed in a protective plasma shield that emanates from the sun, known as the heliosphere. It’s made from a constant flow of charged particles, called solar wind, that stretch well past Pluto, wrapping the planets in what NASA calls a “a giant bubble.” It protects us from radiation and galactic rays that could alter DNA, and scientists believe it’s part of the reason life evolved on Earth as it did. According to the latest paper, the cold cloud compressed the heliosphere in such a way that it briefly placed Earth and the other planets in the solar system outside of the heliosphere’s influence. 

This paper is the first to quantitatively show there was an encounter between the sun and something outside of the solar system that would have affected Earth’s climate,” says Opher, who is an expert on the heliosphere. Her models have quite literally shaped our scientific understanding of the heliosphere, and how the bubble is structured by the solar wind pushing up against the interstellar medium—which is the space in between stars and beyond the heliosphere in our galaxy. Her theory is that the heliosphere is shaped like a puffy croissant, an idea that shook the space physics community. Now, she’s shedding new light on how the heliosphere, and where the sun moves through space, could affect Earth’s atmospheric chemistry

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