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The Milky Way galaxy is our home, and yet in some ways, it is the least understood galaxy. One of the biggest challenges astronomers have is in understanding its large-scale structure. Because we’re in the midst of it all, mapping our galaxy is a bit like trying to map the size and shape of a wooded park while standing in the middle of it.

One of the ways astronomers can map our galaxy is to measure the position and distance of thousands upon thousands of stars. This is one of the main goals of the Gaia mission, which studies the location and motion of more than a billion stars. Gaia has already revealed details in the structure of the Milky Way, such as a wave pattern among some stars.

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The Eagle, Omega, Triffid, and Lagoon Nebulae, imaged by NASA’s infrared Spitzer Space Telescope. Credit: NASA/JPL-Caltech

Another method is to look at specific objects in our galaxy, such as star-forming nebulae. Star-forming nebulae tend to be located within the spiral arms of a galaxy, where there is the most gas and dust. The Spitzer infrared space telescope has measured the distances to young stars within many nebulae, which helped us confirm that the Milky Way has four main spiral arms.

A new study combines data from Gaia and Spitzer, comparing the location of some nebulae with the overall spiral distribution of stars.[^1] The study focused on a main spiral arm within the galaxy known as the Sagittarius Arm. It is the spiral arm just inward from the Sun’s arm of Orion. The team hoped to measure an aspect of the spiral arm known as the pitch angle. It tells you how tightly wound a spiral arm is. The larger the pitch angle, the more open the spiral arms are. In the case of the Sagittarius Arm, the pitch angle is about 12 degrees. But pitch the angle of some nebulae are very different.

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Astronomers found a break in our galaxy’s Sagittarius Arm. Credit: NASA/JPL-Caltech

The team looked at four prominent nebulae in our night sky: the Eagle Nebula (which contains the Pillars of Creation), the Omega Nebula, the Trifid Nebula, and the Lagoon Nebula. These four nebulae are in the same general region and were used in the 1950s to confirm the existence of the Sagittarius Arm. This new study pinned down the location of these nebulae and other stars and found the region has a pitch angle of 60 degrees.

This doesn’t mean our original measure of the Sagittarius Arm is wrong, but it does point to a type of structure known as galactic spurs. Some spiral galaxies have very smooth spiral arms, where gas, dust, and star-forming regions are all along the same curve. Other spiral galaxies have more broken spiral arms, with small feathery offshoots called spurs. We don’t know for sure which type of galaxy the Milky Way is, but this new study points to it being the latter.

Reference: Kuhn, M. A., et al. “A high pitch angle structure in the Sagittarius Arm.” Astronomy & Astrophysics 651 (2021): L10.

The post The Milky Way Broke one of its Arms appeared first on Universe Today.

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Does Betelgeuse Even Rotate? Maybe Not

Betelgeuse pulsating UV HST jpeg

Betelgeuse is the well known red giant star in the corner of Orion the hunter. The name translated in some languages means ‘armpit of the giant’ which I think of all the star names, is simply the best! Betelgeuse has been fascinating observers of late not only because it unexpectedly faded a few years ago but more recently a study shows it’s super fast rotational speed which is, when compared to other supergiants, is like nothing seen before. 

One of the brightest stars in the northern hemisphere sky, in fact the tenth brightest, Betelgeuse has a stunning red colour. It is a semi regular variable star which means there is some regularity to its varied light output but there are occasions, perhaps lasting between 20 and 2000 days where the variation is interrupted. If Betelgeuse were placed in the Sun’s position then its visible surface would more than likely extend beyond the orbit of Mars and swallow up everything in between. 

Image showing the variability of Betelgeuse
1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles (Credit :  STScI, NASA, ESA)

Like all stars, Betelgeuse rotates but a recent study using the Atacama Large Milimeter Array (ALMA) has showed that Betelgeuse is rotating faster than expected. Cool stars like Betelgeuse expand as they evolve and to conserve momentum the rotation must slow.  It is possible that mass loss due to stellar winds decreases rotation speeds further. The current theory predicts that red giants rotate at around 1km per second while red supergiants a little less than 0.1km per second. 

Image showing two of the receivers of the ALMA array in the Atacama Desert.
Two of the Atacama Large Millimeter/submillimeter Array (ALMA) 12-metre antennas (Credit : Iztok Bon?ina/ESO)

Current theory aside it seems there have been a number of observations of at least a few hundred giant stars rotating faster. Betelgeuse in particular has shown faster than expected rotation. Somewhat usefully, it’s proximity to Earth has meant its surface can be resolved and accurate measurements taken. Measurements showed that half of the visible hemisphere was blue shifted and the the other half red shifted. We can use this information to accurately calculate a rotational velocity.

When it comes to Betelgeuse, the radial velocity with ALMA was measured to be around 5.47 km per second. This value was compared against previous observations using Hubble Space Telescope and thankfully this agreed. One leading theory takes binary star evolution as a possible cause and in particular a merger with a low mass companion star. This is not an unusual process with an expected one-third of red supergiants experience stellar merger before their core collapses marking the end of their life. When it comes to red giants the team considered the impact of merging with planetary systems on the rotational velocity.

There are complications however in attaining sufficient data but the team modelled 3D radiation hydrodynamic simulations of red supergiants with properties similar to Betelgeuse. Throwing a proverbial spanner in the works, the team suggest that it is possible that the observations could be wrong and false signals have been picked up from churning convective plasma at the surface rather than the rotation of the star itself!

In an attempt to ascertain if it is possible to accurately measure the rotational speed of red giants and supergiants they had to develop new processing techniques to establish predictions that they could compare with observations of Betelgeuse. The team finally conclude that to be able to establish without doubt that Betelgeuse and other red supergiants are rotating
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5 Reasons You Must Backpack the Teton Crest Trail

Wind4 016 jpg

By Michael Lanza

On my first backpacking trip on the Teton Crest Trail in Grand Teton National Park, camped on Death Canyon Shelf, a broad, boulder-strewn and wildflower-carpeted bench at 9,500 feet, I awoke to the sound of heavy clomping outside my tent. I unzipped the tent door to investigate—and saw a huge bull elk standing just outside my nylon walls.

As I’ve come to learn over more than 20 trips to the Tetons since that first one over three decades ago, that elk encounter symbolized just one of several compelling reasons why every backpacker should move the Teton Crest Trail to the top of their to-do list: the wildlife. Where it occurred illustrates another reason: After years of backpacking all over the United States—including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog—Death Canyon Shelf is still one of my all-time favorite backcountry campsites.

Wind4 016 1 jpg
Hi, I’m Michael Lanza, creator of The Big Outside, which has made several top outdoors blog lists. 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 to learn how I can help you plan your next trip.

Watching the sunset from a campsite in the North Fork Cascade Canyon, Grand Teton National Park.
” data-image-caption=”Watching the sunset from a campsite in the North Fork Cascade Canyon on the Teton Crest Trail in Grand Teton National Park.
” data-medium-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?fit=200%2C300&ssl=1″ data-large-file=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?fit=683%2C1024&ssl=1″ src=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?resize=432%2C648&ssl=1″ alt=”Watching the sunset from a campsite in the North Fork Cascade Canyon, Grand Teton National Park.” class=”wp-image-36411″ style=”width:432px;height:648px” width=”432″ height=”648″ srcset=”https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?w=800&ssl=1 800w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?resize=200%2C300&ssl=1 200w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?resize=768%2C1152&ssl=1 768w, https://i0.wp.com/thebigoutside.com/wp-content/uploads/2019/11/Tet19-090-A-campsite-on-the-Teton-Crest-Trail-North-Fork-Cascade-Canyon-Grand-Teton-N.P.jpg?resize=683%2C1024&ssl=1 683w” sizes=”(max-width: 432px) 100vw, 432px” data-recalc-dims=”1″ />Watching the sunset from a campsite in the North Fork Cascade Canyon, Grand Teton National Park.

And I certainly consider the Teton Crest Trail one of the 10 best backpacking trips in America. It’s the one I keep going back to again and again. (Read about my most recent trip.)

I think the five reasons I lay out below will give you insights into questions you might have about this classic hike—and inspire you to go do it.

But know this important planning detail: The

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How to Get a Permit to Backpack the Teton Crest Trail

Tet19 047 Me on Teton Crest Trail copy cropped jpg

By
Michael Lanza

For
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.

Tet19 047 Me on Teton Crest Trail copy cropped 1 jpg
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
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