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For a long time, we wondered if other stars hosted planets like the Sun does. Finally, in the 1990s, we got our answer. Now, another question lingers.

Most of the planets in our Solar System have moons. Do exoplanets have exomoons?

Moons are the norm in our Solar System. Only Mercury and Venus, the two planets closest to the Sun, don’t have moons. Mercury is too small to maintain a hold on a moon so close to the Sun, and Venus may have had one in the past and then lost it. On the other end of the scale are our two gas giants, Jupiter and Saturn. Together, they host almost 250 moons, though many of them are very small.

There’s no reason to think that planets in other solar systems don’t have moons. But just like with exoplanets, we don’t know until we know.

We thought we knew six years ago when researchers at Columbia University found evidence of a giant moon orbiting the exoplanet Kepler-1625b. They were suitably cautious with their findings, making certain people understand that they had found only a candidate moon in the Kepler 1625 system. “This candidate has passed a thorough preliminary inspection, but we emphasize again our position that the Kepler data are insufficient to make a conclusive statement about the existence of this moon,” the authors wrote. They hoped that follow-up observations with the Hubble Space Telescope would confirm it. “Only after the HST observation is made should any claim about this moon’s existence be given much credence.”

Hubble never did confirm it, but Kepler 1625b wasn’t the only exoplanet with a potential exomoon. Kepler-1708b also exhibited signs of an orbiting exomoon. Now, new research suggests that what scientists were seeing in the data are not exomoons.

This is an artist's visualization of Kepler-1708b, the second exoplanet with a potential exomoon. Image Credit: NASA.
This is an artist’s visualization of Kepler-1708b, the second exoplanet with a potential exomoon. Image Credit: NASA.

Exomoons are extraordinarily difficult to detect. When exoplanets are hundreds or thousands of light years away, we can only detect them when they block their star’s light. That’s already a monumentally difficult task that’s plagued with false positives and other obstacles. Exomoons are much smaller and far more elusive, making their detection dramatically more difficult.

“Exomoons are so far away that we cannot see them directly, even with the most powerful modern telescopes,” explains Dr. René Heller. Heller is from the Max Planck Institute for Solar System Research (MPS) and the first author of a new research article in Nature Astronomy. It’s titled “Large exomoons unlikely around Kepler-1625 b and Kepler-1708 b,” a title that needs no parsing.

Kepler 1625b is a Jupiter-size planet orbiting a Sun-like star over 8,000 light-years away. When its potential moon was discovered, it generated lots of interest. Not only because it would’ve been the first one, but it also would’ve been a gigantic behemoth moon as large as Neptune that dwarfed all of the moons in our solar system.

Kepler-1708b orbits an F-type star over 5,000 light-years away. In 2021 astronomers found evidence of an exomoon orbiting the Jupiter-like gas giant. If real, it’s also an enormous moon. “The moon is pretty alien compared to any moon in the solar system,” said David Kipping, an astronomer at Columbia University involved with the discovery. “We’re not sure if it’s rocky; we’re not sure if it’s gaseous. It’s kind of in between the size of Neptune, which is gaseous, and the Earth, which is rocky,” Kipping said in an interview with NPR.

We tend to think of exoplanet discoveries as more direct than they really are. In the past, astronomers would sit at their telescopes carefully observing the sky until they found something. But modern astronomy isn’t like that. Spacecraft like Kepler and TESS generate an enormous amount of data, and it’s up to scientists to make sense of it and find the discoveries in all that data. These exomoons were discovered in a deep analysis of Kepler data.

Astronomers look for light curves in Kepler data. When they find one that dips regularly, it indicates an exoplanet. Exomoons would also produce light curves, but they’re more complicated than

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Why is Jupiter’s Great Red Spot Shrinking? It’s Starving.

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The largest storm in the Solar System is shrinking and planetary scientists think they have an explanation. It could be related to a reduction in the number of smaller storms that feed it and may be starving Jupiter’s centuries-old Great Red Spot (GRS).

This storm has intrigued observers from its perch in the Jovian southern hemisphere since it was first seen in the mid-1600s. Continuous observations of it began in the late 1800s, which allowed scientists to chart a constant parade of changes. In the process, they’ve learned quite a bit about the spot. It’s a high-pressure region that generates a 16,000 km-wide anticyclonic storm with winds clocking in at more than 321 km per hour. The storm extends down through the atmosphere to a depth of about 250 km below the mainly ammonia cloud tops.

A zoomed-in view of the Great Red Spot based on Juno observations. Courtesy Kevin Gill.
A zoomed-in view of the Great Red Spot based on Juno observations. Courtesy Kevin Gill.

Modeling a Shrinking and Growing Great Red Spot

Over the past century, scientists noticed the GRS shrinking, leaving them with a puzzle on their hands. Yale Ph.D. student Caleb Keaveney had the idea that perhaps smaller storms that feed the GRS could play a role in starving it. He and a team of researchers focused on their influence and conducted a series of 3D simulations of the Spot. They used a model called the Explicit Planetary Isentropic-Coordinate (EPIC) model, which is used in studying planetary atmospheres. The result was a suite of computer models that simulated interactions between the Great Red Spot and smaller storms of varying frequency and intensity.

A separate control group of simulations left out the small storms. Then, the team compared the simulations. They saw that the smaller storms seemed to strengthen the Great Red Spot and make it grow. “We found through numerical simulations that by feeding the Great Red Spot a diet of smaller storms, as has been known to occur on Jupiter, we could modulate its size,” Keaveney said.

If that’s true, then the presence (or lack thereof) of those smaller storms could be what’s changing the spot’s size. Essentially, a lot of smaller spots cause it to grow larger. Fewer little ones cause it to shrink. Furthermore, the team’s modeling supports an interesting idea. Without forced interactions with these smaller vortices, the Spot can shrink over a period of about 2.6 Earth years.

Using Earth Storms as a Comparison

The Great Red Spot isn’t the only place in the Solar System that sports such a long-lived high-pressure system. Earth experiences plenty of them, usually called “heat domes” or “blocks.” Most of us are familiar with heat domes because we experience them during the summer months. They happen frequently in the upper atmosphere jet stream that circulates across our planet’s mid-latitudes. We can blame them for some of the extreme weather people experience—such as heat waves and extended droughts. They tend to last a long time, and they are linked to interactions with smaller transient weather such as high-pressure eddies and anticyclones.

Given that the Great Red Spot is an anticyclonic feature, it has interesting implications for similar atmospheric structures on both planets, according to Keaveney. “Interactions with nearby weather systems have been shown to sustain and amplify heat domes, which motivated our hypothesis that similar interactions on Jupiter could sustain the Great Red Spot,” he said. “In validating that hypothesis, we provide additional support to this understanding of heat domes on Earth.”

The Ever-changing Great Red Spot

In addition to the changing size of the Great Red Spot, observers also notice shifts in its color. It’s mainly reddish-orange but has been known to fade to a pinkish-orange hue. The colors suggest some complex chemistry occurring in the region spurred by solar radiation. It has an effect on a chemical compound called ammonium hydrosulfide as well as the organic compound acetylene. That creates a substance called a tholin, which gives a reddish color wherever it exists.

At times the spot has nearly disappeared altogether due to some complex interaction with a feature called
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Review: Patagonia Black Hole Pack 32L Travel Pack

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Travel Pack
Patagonia Black Hole Pack 32L

$169, 32L/1,831 c.i., 1 lb. 12.6 oz./810g

One size

backcountry.com

If you’re like me, whenever you’re flying somewhere for a few days, maybe a week or more, you ask yourself the same question: Can I do this without checking luggage? Not only do I loathe paying a luggage fee, but I don’t want to give an airline the opportunity to lose my luggage. Plus, I like the convenience, low expense, and the ethically and morally correct choice (in this age of climate crisis) of using public transportation to and from airports—which is really only feasible when carrying one small, light, portable bag or pack. For me, the carry-on of choice is the Patagonia Black Hole Pack 32L.

For starters, I generally like having a small and light pack or bag with shoulder straps that I can throw onto my back to move quickly through airports; wheeled luggage of any size quickly loses its convenience when you’re in a serious rush in an airport, have no choice but to go up or down stairs (which I prefer, anyway, to standing on an escalator behind a line of stationary people), or are taking subways, buses, or trains.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-guides to classic backpacking trips. Click here to learn how I can help you plan your next trip.

The Patagonia Black Hole Pack 32L back panel and shoulder straps.
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” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg?fit=225%2C300&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg?fit=768%2C1024&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2-768×1024.jpg?resize=768%2C1024&ssl=1″ alt=”The Patagonia Black Hole Pack 32L back panel and shoulder straps.” class=”wp-image-59669″ style=”width:602px;height:auto” srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg 225w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg 640w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/07/06224812/Patagonia-Black-Hole-Pack-32L-harness-2.jpg 900w” sizes=”(max-width: 768px) 100vw, 768px” data-recalc-dims=”1″ />The Patagonia Black Hole Pack 32L back panel and shoulder straps.

On my most recent trip, flying cross-country to visit family and friends—two flights and a layover of 90 minutes or more in each direction—I wanted to avoid checking luggage (for all the reasons given above). Packing frugally, I fit everything I needed into my Black Hole Pack 32L for
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Pulsars are the Ideal Probes for Dark Matter

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Pulsars are the remnants of the explosion of massive stars at the end of their lives. The event is known as a supernova and as they rapidly spin they sweep a high energy beam across the cosmos much like a lighthouse. The alignment of some pulsar beams mean they sweep across Earth predictably and with precise regularity. They can be, and often are used as timing gauges but a team of astronomers have found subtle timing changes in some pulsars hinting at unseen mass between pulsars and telescopes—possibly dark matter entities.

The discovery in 1967 of pulsars has revolutionised our understanding of stellar evolution. The are formed during the collapse of supermassive stars at the end of their life. As the fusion in the core ceases, the inrushing stellar material crashing down onto the core compresses it to incredible density. The material that once made up the star is, through this process compressed into a sphere just a few tens of kilometres across. Pulsars are closely related to neutron stars which are formed though the same process and it is believed, the only difference is that one has a highly energetic beam that flashes across the Earth and one doesn’t. 

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Visualization of a fast-rotating pulsar. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab

A team studying pulsars has recently detected hints of potential dark matter objects through changes in pulsar timing events as they rotate. Professor John LoSecco from the University of Notre Dame, presented at the National Astronomy Meeting at the University of Hull and emphasised the precision of pulsar-based timekeeping. “Science has advanced with precise time measurement methods,” he noted, comparing Earth’s atomic clocks with pulsars in space. While gravitational effects on light have been understood for over a century, their applications in uncovering hidden masses remain largely unexplored until now.

Professor LoSecco and the team noted tiny deviations in the pulsar timing, suggesting that radio waves may be getting redirected around an unseen mass located somewhere between the pulsar and the telescope. LoSecco theorised that the masses could potentially be dark matter!

By examining the delays and analysing the radio pulse arrivals (which were typically accurate to within a nanosecond) they explored the pathway of radio signals within the latest Parkes Pulsar Timing Array survey. Other telescopes involved in this initiative were the Effelsberg, Nançay, Westerbork, Green Bank, Arecibo, Parkes, and the Lovell telescope in Cheshire. Using this and Parkes data, the pulse arrival times were analysed.

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The Arecibo Radio Telescope Credit: UCF

The results showed that the pulses occur regularly every three weeks across three observational bands. However, when dark matter causes delays in arrival times, these delays display distinct shapes proportional to the mass of the dark matter. Regions with dark matter slow down the passage of light and effect the pulsar timings. The Sun for example, could produce a delay of about 10 microseconds however the timing differences 10,000 times smaller.  A detailed examination of precise data from 65 ‘millisecond pulsars’ has identified approximately twelve instances suggestive of interactions with dark matter.

Source : How astronomers are using pulsars to observe evidence of dark matter

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