One of the greatest cosmological mysteries facing astrophysicists today is Dark Matter. Since the 1960s, scientists have postulated that this invisible mass accounts for most of the matter in the Universe. While there are still many unresolved questions about it – i.e., What is it composed of? How do we detect it? What evidence is there beyond indirect detection? – we have managed to learn a few things about it over time.
For example, astrophysicists have observed that Dark Matter played a vital role in the formation of galaxies and is responsible for keeping them gravitationally bound. However, when an international team of astronomers observed the ultra-diffuse galaxy AGC 114905, they found no evidence of Dark Matter at all. If these observations are accurate, this discovery could force scientists to reevaluate their cosmological models and the way we look at the Universe.
The research team was led by researchers from the Kapteyn Astronomical Institute at the University of Groningen and the Netherlands Institute for Radio Astronomy (ASTRON). They were joined by astronomers and cosmologists from the University of Durham, Valparaiso University, and the University of Illinois. Their research findings were accepted for publication and will appear in the Monthly Notices of the Royal Astronomical Society.
As the team explained in a previous study, the road to this discovery began when Pavel Mancera Piña – a Ph.D. student with the University of Groningen and ASTRON and the lead author on both papers – and his colleagues observed six galaxies that appeared to have little or no dark matter. These findings contradicted prevailing theories about dark matter, which states that all galaxies (especially ultra-diffuse dwarf galaxies) could not exist without dark matter to hold them together.
Piña and his colleagues were instructed to retake their measurements and used the Very Large Array (VLA) in New Mexico to conduct an observation campaign of one galaxy in particular. This was AGC 114905, a gas-rich, ultra-diffuse dwarf galaxy located about 250 million light-years away in the constellation Pisces. This designation refers to the fact that it is a low luminosity galaxy with far fewer stars than galaxies like ours (despite being comparable in size).
During this campaign, the team collected data on the rotation of gas in AGC 114905 for 40 hours between July and October 2020. They then made a graph that showed the distance of the gas from the center of the galaxy (x-axis) and the rotational speed of the gas (y-axis), which is a standard way of revealing the influence of dark matter. This graph showed that the presence of normal matter alone could explain the motions of the gas in AGC 114905.
As Piña explained in a recent Royal Astronomical Society press release:
“This is, of course, what we thought and hoped for because it confirms our previous measurements. But now the problem remains that the theory predicts that there must be dark matter in AGC 114905, but our observations say there isn’t. In fact, the difference between theory and observation is only getting bigger.”
Simulation of dark matter and gas. Credit: Illustris Collaboration (CC BY-SA 4.0)
As Piña and his colleagues indicate in their study, there are several possible explanations for the lack of dark matter. For starters, AGC 114905 may have been stripped of its dark matter through tidal interaction with neighboring large galaxies. They also adjusted the parameters of the Lamba-Cold Dark Matter (?CDM) cosmological model and alternate theories to General Relavity to obtain values consistent with their observations. But as Piña explained, none of it worked:
“But there are none. And in the most reputed galaxy formation framework, the so called cold dark matter model, we would have to introduce extreme parameter values that are far beyond the usual range. Also with modified Newtonian dynamics, an alternative theory to cold dark matter, we cannot reproduce the motions of the gas within the galaxy.”
Another possibility they considered was that their estimates of the estimated angle at which
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NASA’s Interstellar Mapping Probe Prepares for a 2025 Launch
Engineers at NASA have completed an important milestone in developing the Interstellar Mapping and Acceleration Probe (IMAP) spacecraft. It’s now moving from development and design to the assembly, testing, and integration phase, targeting a launch in late Spring 2025. After launch, the spacecraft will fly to the Earth-Sun L1 Lagrange Point and analyze how the Sun’s solar wind interacts with charged particles originating from outside the Solar System.
IMAP will follow up on discoveries and insights from the two Voyager spacecraft and the Interstellar Boundary Explorer (IBEX) and will help investigate two of the most important overarching issues in heliophysics: the energization of charged particles from the Sun and the interaction of the solar wind at its boundary with interstellar space.
The mission will map the boundaries of the heliosphere — the electromagnetic bubble surrounding and protecting our solar system — and help researchers better understand the boundary of the heliosphere. This region is where the constant flow of particles from our Sun, called the solar wind, collides with material from the rest of the galaxy. This collision limits the amount of harmful cosmic radiation entering the heliosphere.
An updated model (left) suggests the shape of the Sun’s bubble of influence, the heliosphere, may be a deflated croissant shape, rather than the long-tailed comet shape suggested by other research (right). The white lines represent the solar magnetic field, while the red lines represent the interstellar magnetic field. Image Credits Opher, et al
It will also help settle the debate on the actual shape of the heliosphere. A study in 2020, using data from several spacecraft, suggested that the Sun’s bubble of influence may be a deflated croissant shape, rather than the long-tailed comet shape that has previously been
The spacecraft will be positioned about 1.5 million km (1 million miles) from Earth and will collect and analyze particles that make it through to help chart and understand the range of particles in interplanetary space.
The milestone the IMAP mission recently met is called Key Decision Point D, which allows the mission to move from development and design to the testing and integration phase. The targeted launch date was moved back one months, from late April to May 2025 to ensure that the project team has the adequate resources to “address risks and technical complexities during system integration and testing,” NASA said in a recent mission blog post.
The spacecraft is currently being assembled inside the clean room at the Johns Hopkins Applied Physics Lab in Laurel, Maryland. There is a live, 24-hour feed where you can watch the assembly, integration, and testing.
During the next few months, engineers will install the electronics, communications systems, thermal systems, propulsion, batteries, and many more complex systems to make the spacecraft work. Additionally, all 10 of IMAP’s instruments will soon start to arrive from around the world and be integrated with the spacecraft one by one. Finally, the spacecraft will begin testing before being sent to NASA’s Goddard Space Flight Center for final testing prior to launch.
Learn more about the mission and the huge team of universities and organizations that are part of IMAP at the mission website.
The post NASA’s Interstellar Mapping Probe Prepares for a 2025 Launch appeared first on Universe Today.
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Does Betelgeuse Even Rotate? Maybe Not
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.
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.
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
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.
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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