Cataclysmic events happen in the Universe all the time. Black hole mergers, supernovae, gamma-ray bursts, and a whole host of others. Most of them happen in distant galaxies, so they pose no threat to us. But there are a few that could affect life on Earth, and a couple could even pose an existential threat. One of these threats is known as a kilonova.
The threat generally comes from high-energy particles. Earth has a good atmosphere and a reasonably strong magnetic field, so we’re well protected from most solar flares and stray cosmic rays. We’re less protected by a truly powerful beam of gamma rays or X-rays that could ionize our atmosphere and kill life on Earth. The most popular idea is that a nearby supernova could kill us all, but the nearest large star that might explode any time soon is Betelguese. It’s just 650 light years away, but when it becomes a supernova it won’t harm Earth, it will just become a star nearly as bright as the Moon.
A more recent idea is that a kilonova might get us. These are triggered by the merger of two neutron stars and can generate a tremendous amount of high-energy particles. They aren’t as bright as a supernova, but they can be a thousand times brighter than a nova. From the polar regions come beams of X-rays, and from the equatorial region comes the kilonova blast itself, which can accelerate particles to become cosmic rays. If Earth happens to be close to a kilonova, it would be very, very bad news for all of us. Fortunately, a recent study shows the kilonova risk is tiny.
Structure of a kilonova. Credit: Perkins, et al
The study is based on a neutron star merger observed in 2017. It was detected optically as a gamma-ray burst (GRB) and gravitationally as a compact object merger. This means we have good data on the masses and distances of the original neutron stars as well as the amount of energy they produced. The team then supplemented this data with theoretical simulations.
There are three main threats from a kilonova explosion. The first is the X-ray emission from the afterglow of the event, which generally emanates from the polar region. Given the decrease in light intensity with distance, the team calculated it would pose a threat to a range of 5 parsecs, or about 16 light-years. The second threat is from the gamma rays produced by the explosion itself. Since gamma rays tend to scatter strongly off interstellar particles, they only pose a threat to 4 parsecs or 13 light-years.
The third threat is more subtle. The first two would reach us at the speed of light, and if we were outside their threat radius we would see them only as an amazing light show. But the shock wave of the kilonova would create an expanding shell of high-energy cosmic rays. These could reach us a thousand years or more after the initial X-rays and gamma-rays. When the team calculated the lethal range of cosmic rays, they found it was nearly 36 light-years. So a nearby cosmic light show from a kilonova could be a warning of our imminent demise.
But there’s no real need to worry. Given the rarity of neutron star mergers in the galaxy, the chance of Earth being close to a kilonova is essentially zero. A much greater risk comes from the solar flares of our own Sun, which mostly poses a technological risk, not an existential one. So we can sleep easy knowing that a neutron star merger isn’t likely to cause us any harm.
Reference: Haille M. L. Perkins, et al. “Could a Kilonova Kill: a Threat Assessment.” arXiv preprint arXiv:2310.11627 (2023).
The post How Close is Too Close to a Kilonova? appeared first on Universe Today.
How to Get a Permit to Backpack the Teton Crest Trail
backpackers, the Teton Crest Trail really delivers it all: beautiful lakes,
creeks, and waterfalls, high passes with sweeping vistas, endless meadows of
vibrant wildflowers, a good chance of seeing wildlife like elk and moose, some
of the best campsites you will ever pitch a tent in, and mind-boggling scenery
just about every step of the way. And it’s a relatively beginner-friendly trip
of 40 miles or less, which most people can hike in four to five days.
No wonder it’s so enormously popular—and there’s so much competition for backcountry permits.
In this story, I will offer tips on how to maximize your chances of getting a permit to backpack the Teton Crest Trail, sharing expertise I’ve acquired from more than 20 trips in the Tetons and several on the Teton Crest Trail over more than three decades, including the 10 years I spent as Northwest Editor of Backpacker magazine and even longer running this blog.
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.
Lake Solitude, North Fork Cascade Canyon, Grand Teton National Park.
” data-image-caption=”Lake Solitude in the North Fork of Cascade Canyon, Grand Teton National Park. Click photo for my e-guide “The Complete Guide to Backpacking the Teton Crest Trail.”
” data-medium-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?fit=900%2C600&ssl=1″ src=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?resize=900%2C600&ssl=1″ alt=”Lake Solitude, North Fork Cascade Canyon, Grand Teton National Park.” class=”wp-image-36414″ srcset=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?resize=1024%2C683&ssl=1 1024w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?resize=300%2C200&ssl=1 300w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?resize=768%2C512&ssl=1 768w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?resize=1080%2C720&ssl=1 1080w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-095-Lake-Solitude-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P..jpg?w=1200&ssl=1 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Lake Solitude in the North Fork of Cascade Canyon, Grand Teton National Park. Click photo for my e-guide “The Complete Guide to Backpacking the Teton Crest Trail.”
See my story from my most-recent trip on it, “A Wonderful Obsession: Backpacking the Teton Crest Trail,” which requires a paid subscription to The Big Outside to read in full, including basic information on planning a TCT backpacking trip. For much more information and expert tips on planning this trip, get my top-selling e-guide “The Complete Guide to Backpacking the Teton Crest Trail in Grand Teton National Park.”
I’ve also helped many readers plan a backpacking trip in the Tetons and elsewhere, answering all of their questions and customizing an itinerary ideal for them. See my Custom Trip Planning page to learn how
Did you miss our previous article…
Eris Could be Slushier Than Pluto
In 2005, astronomer Mike Brown and his colleagues Chad Trujillo and David Rabinowitz announced the discovery of a previously unknown planetoid in the Kuiper Belt beyond Neptune’s orbit. The team named this object Eris after the Greek personification of strife and discord, which was assigned by the IAU a year later. Along with Haumea and Makemake, which they similarly observed in 2004 and 2005 (respectively), this object led to the “Great Planet Debate,” which continues to this day. Meanwhile, astronomers have continued to study the Trans-Neptunian region to learn more about these objects.
While subsequent observations have allowed astronomers to get a better idea of Eris’ size and mass, there are many unresolved questions about the structure of this “dwarf planet” and how it compares to Pluto. In a recent study, Mike Brown and University of California Santa Cruz professor Francis Nimmo presented a series of models based on new mass estimates for Eris’ moon Dysnomia. According to their results, Eris is likely differentiated into a convecting icy shell and rocky core, which sets it apart from Pluto’s conductive shell.
Their paper, “The internal structure of Eris inferred from its spin and orbit evolution,” recently appeared in the journal Science Advances. The research began while Nimmo was visiting Professor Brown at Caltech and realized that some of his previously-unpublished data could help reveal information about the properties of Eris. At present, we know that Eris is about the same size and mass as Pluto and has a highly eccentric orbit around our Sun, ranging from 38.271 AU at perihelion to 97.457 AU at aphelion. This is almost twice as eccentric as Pluto’s orbit and roughly 50% farther from the Sun.
Comparison between the eight largest TNOs with Earth (all to scale). Credit: NASA/Lexicon
For several months, Brown and Nimmo worked on models of Eris that incorporated two key pieces of information. The first had to do with Eris’ only known satellite, Dysnomia, and how the two bodies always face the same way toward each other. “That happens because the big planet gets spun down by the tides that the little moon raises on it,” said Nimmo in a recent UCSC press release. “The bigger the moon is, the faster the planet spins down. And so as soon as you know that, then you can actually start to do real calculations.”
Astronomers can use the spin and orbital characteristics of planets and their moons to infer certain properties, like their internal structures. But until recently, scientists did not have estimates on Dysnomia’s size, mass, and density. Luckily, Brown and his colleague Bryan J. Butler – a researcher at the National Radio Astronomy Observatory (NRAO) – recently conducted observations of Dysnomia and Eris (and Orcus and its satellite Vanth) using the Atacama Large Millimeter-submillimeter Array (ALMA). Based on their findings, published in The Planetary Science Journal, Dysnomia has a diameter of about 615 km (382 mi) and Dysnomia and Eris have a mass ratio of 0.0085.
This upper mass limit provided the second crucial piece of information, which concerned Eris’ internal structure. The main result of Brown and Nimmo’s model (but did not expect) is that Eris is surprisingly dissipative, a concept in thermodynamics where a system operates out of equilibrium. From this, they determined that Eris has a rocky core surrounded by a layer of ice and a crust that is likely convecting. “The rock contains radioactive elements, and those produce heat,” Nimmo said. “And then that heat has to get out somehow. So as the heat escapes, it drives this slow churning in the ice.”
This sets it apart from Pluto, which has a conducting shell, as revealed by the New Horizon mission. Brown and Nimmo hope that more exact measurements of Dysnomia’s mass will be available in the near future, as well as additional data about the shape of Eris. Because of its distance, Eris appears as a single pixel of light, while Dysnomia is visible as a faint speck next to it (see below). Therefore, astronomers must monitor Eris as it passes in front of background stars to reconstruct its shape. This is similar to the Transit Method astronomers use to detect exoplanets and constrain their sizes.
Hubble is Offline Because of a Problem with one of its Gyros
The rich flow of scientific data—and stunning images—that comes from the Hubble Space Telescope is being interrupted by gyro problems. One of the telescope’s three remaining gyros gave faulty readings, and the Hubble automatically entered safe mode. In safe mode, science operations are suspended.
Without gyros, the Hubble can’t orient itself properly. Gyros measure the telescope’s turn rate and help the telescope know where it’s pointed. They’re part of the system that keeps the space telescope pointed in the right direction. There’s no indication of any problems with Hubble’s instruments, like its Wide-Field Camera 3 or its Advanced Camera for Surveys.
This all began on November 19th when Hubble went into safe mode. Engineers recovered the telescope, and regular science operations resumed the following day. However, the unstable gyro caused problems again, and the space telescope suspended science operations again on the 21st. It was recovered again, then went back into safe mode on November 23rd. That’s where things stand now.
NASA is working to resume science operations of the Hubble Space Telescope after it entered safe mode Nov. 23 due to an ongoing gyroscope issue. Hubble’s instruments are stable, and the telescope is in good health: https://t.co/QOdJJ9WjYh pic.twitter.com/URRHYV3Le8
— Hubble (@NASAHubble) November 29, 2023
The Hubble was launched with six original gyros, but they failed fairly rapidly. During its last shuttle servicing mission in 2009, the Hubble received six new gyros. Three of them were the older type that failed fairly quickly, and three were new ones. The three older ones from 2009 have failed, and Hubble has three remaining gyros, and all of them have a more modern design. It can operate with a single functioning gyro, though it’s less efficient.
This image shows astronaut Mike Massimino during Service Mission 4 to the Hubble in 2009. Astronaut Mike Good is in the background. During SM-4, Hubble received new gyroscopes, as well as two new scientific instruments – the Cosmic Origins Spectrograph (COS) and Wide Field Camera 3 (WFC3). Image Credit: NASA
Each gyro is a small cylinder filled with fluid. Inside the fluid, an internal float spins thousands of times per second. The original six gyros and three of the 2009 replacements contained bromine in the fluid. The bromine ate away at the gyros, causing their eventual demise.
One of the Hubble’s gyros. Older ones had bromine in their interior fluid, which ate away at the gyros, causing their demise. Image Credit: NASA
This isn’t the first time failing gyros have caused a shutdown in Hubble’s science operations. The preceding incident happened in 2018. At that time, Ken Sembach was the Director of the Space Telescope Science Institute (STScI.) In an interview, he expressed some frustration, telling Business Insider, “We’ve had some issues with this gyro in the past, and we’ve got some possible leads on the current problem. But the thing that’s been clear on Hubble is that these gyros all have a mind of their own. I don’t think anybody really knows what’s going on with it right now.”
The gyros are just part of the system that keeps Hubble pointed where astronomers want it pointed. The system also includes reaction wheels and fine guidance sensors
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