*Written by OC Wanderer, author of Destiny Among the Stars, a LitRPG sci-fi series set in the real stellar neighborhood. Published October 5, 2026.*
A supernova can leave behind a [neutron star](https://ocwanderer.com/blog/what-would-it-feel-like-to-approach-a-neutron-star). A whole cluster of explosions can reshape the space between stars, pushing gas into a shell and leaving a vast hollow inside. Our Sun is traveling through one of those hollows right now: the Local Bubble.
I wonder whether that emptiness has been good to us. Suppose two worlds circle two similar stars, one inside the Bubble and one far outside it. I picture the inside world getting the calmer sky. But thin gas comes with a history of nearby explosions, and particles from those explosions may still reach worlds inside the cavity. The interesting question is what that world inherits from its neighborhood, and how much protection its star, magnetic field and atmosphere provide.
## The explosions left a hollow surrounded by stellar nurseries
The nearest star-forming clouds trace the surface of the Local Bubble, with their young stars drifting outward, mostly at right angles to it. Run those motions backward and the picture begins to resemble an enormous expanding shell: a burst of stellar birth and death near its center about 14 million years ago, followed by blasts pushing gas outward into the clouds where new stars now form. Catherine Zucker's team pieced this history together in 2022 from stellar motions and 3D gas maps within about 650 light-years of the Sun.<sup class="footnote-ref" data-footnote="true" id="fnref-1"><a class="footnote-link" href="#fn-1">1</a></sup> I love the scale of that connection. The aftermath of dead stars became the material for new ones.
A 2023 simulation puts the count at 14 explosions, all from one nearby group of stars, the Scorpius-Centaurus association.<sup class="footnote-ref" data-footnote="true" id="fnref-2"><a class="footnote-link" href="#fn-2">2</a></sup> Inside, the Bubble's hot gas is exceedingly thin.<sup class="footnote-ref" data-footnote="true" id="fnref-3"><a class="footnote-link" href="#fn-3">3</a></sup> The explosions swept gas into the wall, where the prominent nearby star-forming clouds now sit hundreds of light-years out. For our imagined world, an empty-looking neighborhood and a ring of stellar nurseries would be parts of the same history.
## The wall is much closer in some directions than others
Calling this place a bubble makes me picture something round. Its mapped wall is far more irregular. A 2024 high-resolution 3D dust map puts the wall about 550 light-years away on average, but its distance ranges from about 230 light-years in the nearest direction to more than 1,950 in the farthest. That is over eight times as far.<sup class="footnote-ref" data-footnote="true" id="fnref-4"><a class="footnote-link" href="#fn-4">4</a></sup> A crew choosing a route toward the star-forming clouds would care a great deal about which direction it chose.
In the northern sky, the wall stretches far above the Galaxy's disk. The researchers interpret that extension as a “Local Chimney,” where the supernova-driven bubble broke open and vented material upward. That is a wonderful image: an interstellar cavity with a chimney reaching out of the galactic disk. It also makes “inside the Bubble” a rather incomplete address. The distance to new stars on its wall depends on direction.
## Thin gas can still carry energetic particles
Sweeping gas out of a region does not sweep away every danger to a planet. Fast-moving atomic nuclei, the cosmic rays we worry about, can still travel through it. A 2017 analysis of AMS-02 measurements suggested that most of the lower-energy cosmic rays come from remnants of supernovae inside the Bubble, some dating to about a million years ago.<sup class="footnote-ref" data-footnote="true" id="fnref-5"><a class="footnote-link" href="#fn-5">5</a></sup> If that explanation holds, the explosions that helped empty our neighborhood also supplied particles moving through it.
Now picture a particle's journey toward a world. A 2025 model places the Bubble's magnetic field along its shell; because magnetic fields bend charged particles, I would expect that geometry to affect their paths.<sup class="footnote-ref" data-footnote="true" id="fnref-6"><a class="footnote-link" href="#fn-6">6</a></sup> Closer to home, the solar wind inflates the Sun's heliosphere, which NASA describes as a giant shield against galactic cosmic radiation.<sup class="footnote-ref" data-footnote="true" id="fnref-7"><a class="footnote-link" href="#fn-7">7</a></sup> A planet's magnetic field and atmosphere then shape what reaches the surface. These are the same pieces [we looked at](https://ocwanderer.com/blog/what-conditions-does-a-planet-actually-need-to-hold-on-to-its-atmosphere-long-term) when asking how a world holds onto its air. An apparently empty sky can hide a complicated journey through several layers of protection.
That makes sheltering a ship a compelling choice in *Destiny Among the Stars*. After a flare in Book 1, Chapter 41, the *Triumph* waits at New Dawn “beneath the sweep of its rings and deep inside its magnetic field, where another flare would hit far less hard than in open space.” The crew can move their ship into shelter. A world's inhabitants have to live with the protections their world provides.
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## The Sun travels through changing surroundings
Our Sun has a route through this history. In the 2023 simulation, it entered the Bubble about 4.6 million years ago.<sup class="footnote-ref" data-footnote="true" id="fnref-8"><a class="footnote-link" href="#fn-8">8</a></sup> Traces of nearby explosions have reached Earth itself: deep-sea crust preserves radioactive iron-60 from stellar sources. Modeling its transport points to two supernovae about 300 light-years away, exploding 2.3 million and 1.5 million years ago.<sup class="footnote-ref" data-footnote="true" id="fnref-9"><a class="footnote-link" href="#fn-9">9</a></sup> Those dates bring the Bubble's violent history much closer to us than its 14-million-year beginning.
Today the Sun sits in a small warm pocket inside the Bubble, the Local Interstellar Cloud, at about a quarter of an atom per cubic centimeter. A cubic centimeter of air at Earth's surface holds about 25 quintillion molecules.<sup class="footnote-ref" data-footnote="true" id="fnref-10"><a class="footnote-link" href="#fn-10">10</a></sup> It is hard to imagine anything so sparse pushing on the Sun's protective bubble. A much denser cloud makes that possibility easier to see.
What if the Sun crossed one 2 to 3 million years ago? A 2024 study modeled that possible encounter using hydrogen survey data. The cloud in its simulation was roughly ten thousand times denser than the Sun's present pocket, and it squeezed the heliosphere to inside Earth's orbit.<sup class="footnote-ref" data-footnote="true" id="fnref-11"><a class="footnote-link" href="#fn-11">11</a></sup> Imagine Earth continuing along its usual orbit while the boundary of the Sun's protective bubble retreats past it. That possibility is thrilling worldbuilding material, even though the encounter remains contested and its biological consequences are unresolved.
The evidence gives us a way to test it. Beryllium-10 and aluminum-26 form under cosmic-ray bombardment, so deep-ocean samples can help investigate past exposure. A 2026 analysis found no indication of a strong rise in cosmic rays 2 to 3 million years ago.<sup class="footnote-ref" data-footnote="true" id="fnref-12"><a class="footnote-link" href="#fn-12">12</a></sup> A simulation can show how the heliosphere might shrink; finding the expected radiation trace in Earth's record is another challenge. I would want that part of the story settled before treating the crossing as an explanation for what happened to life here.
## So could the Local Bubble be unusually good, or unusually bad, for habitability?
The answer depends on the world and the era. The Bubble's thin gas and history of explosions set the surroundings, while the star's heliosphere, the world's magnetic field and its atmosphere shape the exposure at the surface. “Inside” alone gives us too little information to choose the safer of our two imagined worlds.
I began by giving the inside world a calmer sky. Now I want to know where its star has traveled and what protects the people looking up. Fourteen explosions in the simulation trace back to one nearby association, which makes me curious about the nursery that produced those stars. That leads to [what is in Scorpius-Centaurus, our nearest massive-star nursery?](https://ocwanderer.com/blog/the-scorpius-centaurus-association-is-the-closest-star-forming-region-to-earth-whats-actually-there)
> [!lore] If you want to follow a crew that shelters its ship inside a planet's magnetic field, [start *Destiny Among the Stars*](https://ocwanderer.com/storytime/story/destiny-among-the-stars).
## Endnotes
1. <span id="fn-1"></span> Catherine Zucker et al., “Star Formation Near the Sun Is Driven by Expansion of the Local Bubble,” *Nature* 601 (2022), 334–337, [DOI](https://doi.org/10.1038/s41586-021-04286-5), [arXiv:2201.05124](https://arxiv.org/abs/2201.05124). The abstract gives nearly all local star-forming complexes on the Bubble's surface, outward expansion perpendicular to it, a burst of birth and death about 14 million years ago near the Bubble's center, and a swept-up shell that fragmented into the most prominent nearby molecular clouds. The volume is within about 200 parsecs of the Sun (arXiv summary). A parsec is 3.2616 light-years, so 200 pc is 652 light-years. <a class="footnote-backref" href="#fnref-1" aria-label="Back to reference 1">↩</a>
2. <span id="fn-2"></span> Schulreich et al., “Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble. II.” *Astronomy & Astrophysics* 680 (2023), A39, [arXiv:2309.13983](https://arxiv.org/abs/2309.13983): 14 supernova explosions, 13 in the Upper Centaurus-Lupus and Lower Centaurus-Crux subgroups and one in V1062 Sco, both Sco-Cen populations, found with Gaia data. The count of missing massive stars comes from the paper's initial-mass-function fit as reported in the [A&A abstract summary](https://www.aanda.org/articles/aa/full_html/2023/12/aa47532-23/aa47532-23.html). <a class="footnote-backref" href="#fnref-2" aria-label="Back to reference 2">↩</a>
3. <span id="fn-3"></span> K. Ferrière, "The Interstellar Environment of Our Galaxy," *Reviews of Modern Physics* 73 (2001): 1031, [arXiv:astro-ph/0106359](https://arxiv.org/abs/astro-ph/0106359): the Local Bubble's hot gas at about 0.0065 particles per cubic centimeter. <a class="footnote-backref" href="#fnref-3" aria-label="Back to reference 3">↩</a>
4. <span id="fn-4"></span> Theo J. O'Neill et al., “The Local Bubble Is a Local Chimney: A New Model from 3D Dust Mapping,” *The Astrophysical Journal* 973 (2024), 136, [DOI](https://doi.org/10.3847/1538-4357/ad61de), [arXiv:2403.04961](https://arxiv.org/abs/2403.04961): peak-extinction surface at an average of 170 pc (range 70 to 600+ pc), typical thickness 35 pc, a Northern extension consistent with a Local Chimney, and possible tunnels to adjacent cavities. Author conversion at 3.2616 light-years per parsec: 170 pc = 554 ly; 35 pc = 114 ly; 70 pc = 228 ly; 600 pc = 1,957 ly; 1,957 ÷ 228 = 8.6. <a class="footnote-backref" href="#fnref-4" aria-label="Back to reference 4">↩</a>
5. <span id="fn-5"></span> A. D. Erlykin, S. K. Machavariani, and A. W. Wolfendale, “The Local Bubble in the interstellar medium and the origin of the low energy cosmic rays,” *Advances in Space Research* 59 (2017), [DOI](https://doi.org/10.1016/j.asr.2016.10.017), [arXiv:1610.07014](https://arxiv.org/abs/1610.07014). The abstract suggests the bulk below about 200 GV of rigidity (momentum divided by charge) comes from a modest number of supernova remnants in the Local Bubble that "appear to have occurred some 10⁶ years ago." The analysis uses AMS-02 data. <a class="footnote-backref" href="#fnref-5" aria-label="Back to reference 5">↩</a>
6. <span id="fn-6"></span> Theo J. O'Neill et al., “A 3D Model of the Local Bubble's Magnetic Field: Insights from Dust and Starlight Polarization,” *The Astrophysical Journal* 988 (2025), 191, [DOI](https://doi.org/10.3847/1538-4357/ade306), [arXiv:2410.17341](https://arxiv.org/abs/2410.17341). The model assumes the field is tangent to the dust-traced shell, built from the polarization of dust emission and starlight, and finds the Local Bubble likely dominates the polarized signal in the majority of lines of sight. The steering of particles is the author's inference from the field orientation. <a class="footnote-backref" href="#fnref-6" aria-label="Back to reference 6">↩</a>
7. <span id="fn-7"></span> NASA Science, “[Heliosphere](https://science.nasa.gov/heliophysics/focus-areas/heliosphere/).” The page says the heliosphere acts as a giant shield protecting the planets from galactic cosmic radiation and gives no percentage. <a class="footnote-backref" href="#fnref-7" aria-label="Back to reference 7">↩</a>
8. <span id="fn-8"></span> Schulreich et al. (2023), same paper as note 2: the simulation finds the Solar System "entered the LB about 4.6 Myr ago." <a class="footnote-backref" href="#fnref-8" aria-label="Back to reference 8">↩</a>
9. <span id="fn-9"></span> Dieter Breitschwerdt et al., “The Locations of Recent Supernovae Near the Sun from Modelling 60Fe Transport,” *Nature* 532 (2016), 73–76, [DOI](https://doi.org/10.1038/nature17424). Two supernovae at distances between 90 and 100 pc, the closest 2.3 million years ago and the second-closest about 1.5 million years ago. 90 to 100 pc = 293 to 326 light-years. <a class="footnote-backref" href="#fnref-9" aria-label="Back to reference 9">↩</a>
10. <span id="fn-10"></span> J. D. Slavin and P. C. Frisch, "The Boundary Conditions of the Heliosphere," *Astronomy & Astrophysics* 491 (2008): 53, [arXiv:0704.0989](https://arxiv.org/abs/0704.0989): 0.23 to 0.27 hydrogen atoms per cubic centimeter in the Local Interstellar Cloud. Air near Earth's surface holds about 2.5 × 10¹⁹ molecules per cubic centimeter (standard value, author's figure). <a class="footnote-backref" href="#fnref-10" aria-label="Back to reference 10">↩</a>
11. <span id="fn-11"></span> Merav Opher, Abraham Loeb, and J. E. G. Peek, “A Possible Direct Exposure of the Earth to the Cold Dense Interstellar Medium 2–3 Myr Ago,” *Nature Astronomy* 8 (2024), 983–990, [DOI](https://doi.org/10.1038/s41550-024-02279-8): HI4PI 21-cm data, the Local Ribbon of Cold Clouds, heliosphere shrinking to 0.22 au (0.22 times the Earth-Sun distance). The cloud density of about 3,000 particles per cubic centimeter is from [Harvard Gazette](https://news.harvard.edu/gazette/story/2024/06/earth-exposed-to-interstellar-medium-millions-of-years-ago-says-study-heliosphere/), which also reports 0.1 particles per cubic centimeter outside the heliosphere and that the authors left biological consequences unexplored. 3,000 ÷ 0.25 = 12,000, or roughly ten thousand (against the Local Interstellar Cloud figure in note 10; against the Gazette's 0.1 the ratio is 30,000). <a class="footnote-backref" href="#fnref-11" aria-label="Back to reference 11">↩</a>
12. <span id="fn-12"></span> Dominik Koll et al., “No Indication of a Strong Increase in Galactic Cosmic Ray Intensity 2–3 Myr Ago from Cosmogenic Nuclides,” *Nature Astronomy* 10 (2026), 630–632, [DOI](https://doi.org/10.1038/s41550-026-02834-5); Merav Opher et al., “Reply to: No Indication of a Strong Increase,” *Nature Astronomy* 10 (2026), 633–635, [DOI](https://doi.org/10.1038/s41550-026-02835-4). <a class="footnote-backref" href="#fnref-12" aria-label="Back to reference 12">↩</a>