After breathing a deep sigh, I feel better — don’t you? It’s relaxing. And it turns out there’s a good reason why we feel relief after big breaths. It comes down to a special fluid inside our lungs. The liquid — pulmonary surfactant — helps our lungs work. Without it, we’d be in serious trouble. But researchers at ETH Zurich, a university in Switzerland, found that deep breaths have an interesting effect on how this fluid interacts with the lungs. The new research was published in the journal Science Advances and could have meaningful implications for future medicine and therapies. 

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‘Magic’ lung fluid to the rescue 

For a long time, scientists have been interested in how this fluid helps us breathe. In the 1980s, research into this area resulted in a life-saving treatment for babies born prematurely with underdeveloped lungs. 

By extracting fluid from animal lungs and injecting it into those of premature infants, doctors were able to reduce respiratory distress syndrome from developing right after birth. The fluid reduces surface stress in the lungs.

«This surface stress influences how compliant the lungs are,» said ETH Zurich professor Jan Vermant. «The more compliant the lungs are, the less resistance there is to expansion and contraction — and the easier it is to breathe.»

Breathing deep to ease tension

The research team wanted to see how lung fluid behaved when it was stretched and recompressed, so they simulated the movements of normal and deep breaths in the lab. 

They measured the fluid’s surface stress in each case and compared the data. The researchers found that surface stress decreases significantly after a deep breath. 

The utmost layer of the thin film that the fluid leaves on a lung settles and hardens over time. 

«Directly at the boundary with the air, there is a slightly stiffer surface layer,» said Maria Novaes-Silva, a doctoral student in Vermant’s research group and the study’s first author. She said that the pronounced stretching and compression of the pulmonary fluid that comes with a deep sigh actually rearranges the surface layer’s composition.

So, after you let out a deep breath, it becomes easier for you to breathe. That’s why we feel a sense of relief from a deep sigh. 

An ETH Zurich spokesperson said that clinical practice has also found that breathing becomes increasingly complex with constant shallow breaths. So, the lab measurements seem to follow real-world observations. 

The researchers theorize that this study may contribute to a better understanding of adult lung failure. 

A pair of once-in-a-lifetime comets will rocket through our skies this October, and it’s a rare treat because they won’t be back for hundreds of years. The comets, C/2025 A6 (Lemmon) and C/2025 R2 (SWAN), look similar from our perspective. 

You can spot these green gaseous globes and their streaming tails right now, but they’ll be even easier to see this coming week. SWAN will shine the brightest around Monday, Oct. 20, NBC News reports. 

Just a day later, on Tuesday, Oct. 21, Lemmon will make its peak showing in the dark sky. You’ll be able to see Lemmon without any equipment, but SWAN will be pretty faint, says Jason Steffen, assistant professor of physics and astronomy at UNLV. 

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«Current models are showing the [Lemmon] comet will likely peak between 3.5 and 4.5 magnitudes when it is nearest to Earth on October 21, which is dimmer than what they showed last week,» Saint Louis Science Center wrote in an update. «This is still bright enough that it could become naked-eye visible from light-polluted locations.»

CNN reports that SWAN will next come by again in 650 to 700 years, and Lemmon won’t return for another 1,300 years.

«Comet Lemmon is called a non-periodic comet. Unlike Halley’s comet, which comes around every 76 years, a non-periodic comet’s orbit is really highly elliptical,» Steffen says. «The last time it was here was in the 700s.»

Comets are known to buck even the most careful predictions, but wary observers might catch these rare spectacles in October from their backyards in the predawn morning or night sky.

New comets on the scene

Lemmon and SWAN were both discovered in 2025. Lemmon was discovered on Jan. 3 in Arizona by the Mount Lemmon Survey using a 60-inch telescope installed on Mt. Lemmon to find celestial objects, which gave the comet its name. 

A Ukrainian amateur astronomer named Vladimir Bezugly discovered the SWAN comet on Sept. 11 while he was looking through images captured by SWAN, a science instrument called Solar Wind ANisotropies, which is installed on the Solar and Heliospheric Observatory in space. 

«It was an easy comet for detection due to sufficient brightness in the (ultraviolet) band and location in the SWAN images, exactly in its center,» Bezugly told Universe Today. He also noted it’s the 20th official SWAN comet so far.

How to see Lemmon and SWAN this month

The darker the night sky, the easier it will be to see comets, moons, planets and stars. If you live in a city, bundle up and take an evening skygazing trip to the country, where there’s less light pollution. Oh, and grab blankets, chairs and something warm to drink.

It takes your eyes a while to adjust to the darkness. Find a comfortable spot where you can stay still and gaze up. The comets might be bright enough to see without aid, but NASA recommends binoculars as a great entry-level stargazing tool.

Telescopes are one of the best ways to skygaze, and you might be able to find one to use or rent at your local library or university. But modern telescopes can also be fairly affordable. 

Smartphone apps can also be helpful when trying to identify celestial phenomena and where to find them. For a few recommendations, check out our list of stargazing apps. 

A sky full of wonders

Aside from the newly discovered comets, skywatchers have a few other cosmic treats to enjoy this month. 

The Orionids meteor shower, when Earth travels through the massive tail of Halley’s Comet, began earlier this month, but you’ll be able to see the meteors through the beginning of November. 

The next supermoon, known as the Beaver Moon, will take place on Nov. 5.