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If the Sun has a stellar neighbourhood, it can be usefully defined as a 20 parsec (65 light-years) sphere centred on our star. Astronomers have been actively cataloguing the stellar population in the neighbourhood for decades, but it hasn’t been easy since many stars are small and dim.

Even with all of the challenges inherent in the effort, astronomers have made steady progress. Do we now have a complete catalogue?

In a new article in Research Notes of the American Astronomical Society, a pair of researchers from the Leibniz Institute for Astrophysics in Potsdam, Germany, try to understand how complete or incomplete our catalogue of the stellar neighbourhood is. The article is titled “Do We Finally Know all Stellar and Substellar Neighbors within 10~pc of the Sun?” The authors are Ralf-Dieter Scholz and Alexey Mints.

If all stars shone as brightly as main sequence stars like our Sun do, it would be easy to catalogue the stars in our neighbourhood. But they don’t. Some are so small and dim that they’re considered failed stars. We call them brown dwarfs or substellar objects.

When we look up at the night sky with the unaided eye, our view is dominated by main sequence stars and giant stars, many of which are far beyond our stellar neighbourhood. Many stars are too dim to see, like red dwarfs and brown dwarfs. In fact, Proxima Centauri, a red dwarf and our nearest neighbour, wasn’t discovered until the early 20th century.

Proxima Centauri. Credit: ESA/Hubble & NASA
Proxima Centauri. Credit: ESA/Hubble & NASA

In the early days of astronomy, measurements of proper motions showed that some stars that appear fixed in place are closer than other stars. All stars move and have proper motion; it’s just not always noticeable in the span of a single lifetime. High proper motion surveys of stars led to the selection of certain stars for measurements of their parallax, which helped locate more stars correctly in space. Then, in the early 20th century, as astronomy and photography were used in conjunction, photographic astrometry triggered a wave of discoveries of our solar neighbours. Those efforts showed that our nearest neighbours are red dwarfs (M dwarfs).

In the 1990s, as technology advanced, infrared sky surveys found more dim stars. “A second wave of discoveries started in the late 1990s with the advance of infrared sky surveys,” the authors write. Missions like the Two Micron All-Sky Survey (2MASS) gave us a new, unprecedented look at the sky. It found M dwarfs, brown dwarfs, and substellar objects like L, T, and Y types, and even minor planets in the Solar System. (Definitions of brown dwarfs and other substellar objects overlap.) By the year 2,000, the Sloan Digital Sky Survey came online, strengthening our catalogue of the sky.

In 1997, Henry et al. published an important paper on the solar neighbourhood titled “The solar neighborhood IV: discovery of the twentieth nearest star.” It showed that the discovery of LHS 1565, about 3.7 pc from Earth, spelled trouble for our census of the neighbourhood. “It ranks as the twentieth closest stellar system and underscores the incompleteness of the nearby star sample, particularly for objects near the end of the main sequence,” Henry et al. wrote. “Ironically, this unassuming red dwarf provides a shocking reminder of how much we have yet to learn about even our nearest stellar neighbours.”

Since about 1997, there’s been a burst of discoveries of stars within the Sun’s neighbourhood. The authors say that these seem to have filled in the gaps in our 10 pc neighbourhood. But some of the knowledge was still based on two assumptions. The first was that the survey out to 5 parsecs was complete, and the second was that the density was uniform out to 10 parsecs. “The first of these is not true, and the second is in question,” the authors write.

Where does that leave us? Up to 90 star systems could still be missing.

Artist’s conception of a brown dwarf like 2MASSJ22282889 431026Did you miss our previous article…
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Galaxies Regulate their Own Growth so they Don’t Run Out of Star Forming Gas

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Look at most spiral or barred spiral galaxies and you will see multiple regions where stars are forming. These star forming regions are comprised of mostly hydrogen gas with a few other elements for good measure. The first galaxies in the Universe had huge supplies of this star forming gas. Left unchecked they could have burned through the gas quickly, generating enormous amounts of star formation. Life fast though and die young for such an energetic burst of star formation would soon fizzle out leaving behind dead and dying stars. In some way it seems, galaxies seem to regulate their star formation thanks to supermassive black holes at their centre. 

The first galaxies formed about 400 to 700 million years after the Big Bang, during the Epoch known as Reionization. These early galaxies were small and faint, mostly composed of hydrogen and helium, and contained dense clusters of massive, short-lived Population III stars (the first generation of stars.) The intense radiation from these stars ionised the surrounding gas, clearing the fog that permeated space making the universe transparent for the first time. These primordial galaxies began merging and interacting, laying the foundation for the galaxy types seen today.

A new study published in the Monthly Notices of the Royal Astronomical Society explores why galaxies are not as large as astronomers would expect. The research suggests that galaxies, even those that formed first, avoid an early death because they have mechanisms similar to “heart and lungs,” which regulate their “breathing”. Without these regulatory processes our bodies, and galaxies would have aged much faster, resulting in massive galaxies filled with dead and dying stars and devoid of new star formation.

Observations show that galaxies are not so big and full of dying stars having outgrown themselves. It seems something limits their ability to allow gas to form into stars. Astrophysicists at the University of Kent believe they may have the answer: galaxies could be controlling their growth rate through a process not too dissimilar to “breathing.” They compare the supermassive black hole at the centre of a galaxy to a heart and the supersonic jets emerging from the poles with the radiation and gas they emit to airways feeding a pair of lungs.

The supermassive black holes seem to pulse just like a heart. These pulses cause a shock front to oscillate along the jets like a diaphragm inflating and deflating the lungs. This process transmits energy along the jet slowly counteracting the pull of gravity and slowing gas accretion and star formation. The idea was developed by PhD student Carl Richards and his simulations showed a black hole pulsing like a heart. 

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Assisted by magnetic fields, a spiraling wind helps the supermassive black hole in galaxy ESO320-G030 grow. In this illustration, the core of the galaxy is dominated by a rotating wind of dense gas leading outwards from the (hidden) supermassive black hole at the galaxy’s center. The motions of the gas, traced by light from molecules of hydrogen cyanide, have been measured with the Atacama Large Millimeter/submillimeter Array. Image credit: M. D. Gorski/Aaron M. Geller, Northwestern University, CIERA, the Center for Interdisciplinary Exploration and Research in Astrophysics.

Richards explains “We realised that there would have to be some means for the jets to support the body – the galaxy’s surrounding ambient gas – and that is what we discovered in our computer simulations,” He continued “The unexpected behaviour was revealed when we analysed the computer simulations of high pressure and allowed the heart to pulse.”

Evidence of ripples just like those in Richards’ simulations, in extra-galactic media have been found in galaxy clusters like the Perseus cluster. These ripples are thought to sustain a galaxy’s environment, though their generation mechanism was unclear. Conventional simulations fail to explain gas flows into galaxies, but the work of the team from the University of Kent may well have answered the question.

Source : How the ‘heart and lungs’ of a galaxy extend its life.

The post Galaxies Regulate their Own Growth so they Don’t Run Out of Star Forming Gas appeared first on Universe Today.

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Bear Essentials: How to Store Food When Backcountry Camping

Tet19 047 Me on Teton Crest Trail copy cropped 28

By Michael Lanza

On our first night in the backcountry of Yosemite National Park on one of my earliest backpacking trips, two friends and I—all complete novices—hung our food from a tree branch near our camp. Unfortunately, the conifer trees around us all had short branches: Our food stuff sacks hung close to the trunk.

During the night, the predictable happened: We awoke to the sound of a black bear clawing up the tree after our food.

Despite our nervousness and incompetence, we somehow managed to shoo that black bear off, though not before he (or she) departed with a respectable haul from our food supply. But by virtue of having started out with way more food than we needed—another rookie mistake that, ironically, compensated for this more-serious rookie mistake (read my tips on not overpacking)—we made it through that hike without going hungry and ultimately had a wonderful adventure.

And we went home with a valuable lesson learned.

Tet19 047 Me on Teton Crest Trail copy cropped 29
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-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A black bear along the Sol Duc River Trail in Olympic National Park.
” data-image-caption=”A black bear along the Sol Duc River Trail in Olympic National Park.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg?fit=300%2C201&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg?fit=900%2C602&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2-1024×685.jpg?resize=900%2C602&ssl=1″ alt=”A black bear along the Sol Duc River Trail in Olympic National Park.” class=”wp-image-34782″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1080w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2019/03/06232206/Olym6-070-Black-bear-Sol-Duc-River-Trail-Olympic-NP-WA-2.jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />A black bear along the Sol Duc River Trail in Olympic National Park.

I’ve learned much more about storing food properly in the backcountry over the more than three decades since that early trip, including the 10 years I spent as the Northwest Editor of Backpacker magazine and even longer running this blog. This article shares what I’ve learned about protecting food from critters like bears and, more commonly, mice and other small animals and some birds like ravens.

Follow the tips below and you’ll not only save yourself and your party or family from going hungry, you might save a bear from developing a habit of seeing humans as sources of food, which too often leads to a bad outcome for that animal.

If you have any questions or tips of your own to share, please do so in the comments section at the bottom of this
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The Rugged Desert Moss Best Equipped to Survive on Mars

Mars

For decades, we have seen Mars as a desolate landscape devoid of any signs of life. Attempt to identify ways of growing plants and food on the red planet have focussed on greenhouse like structures to enable plants to survive, that is, until now! A desert moss called ‘Syntrichia caninervis’ has been identified and it can grown in extreme environments like Antarctica and the Mojave Desert. A new study revealed the moss can survive Mars-like environments too including low temperatures, high levels of radiation and drought. 

Mars has often be referred to as the “Red Planet” for its distinct red hue. It is the fourth planet from the Sun and to some extent resembles the Earth. Polar ice caps, seasonal weather patterns, extinct volcanoes, ancient riverbeds and flood plains are among the many surface features and. This cold world has fascinated us for centuries and its thin atmosphere, mostly made up of carbon dioxide, has been subjected to lots of studies. It has been thought for many years that it experiences some of the harshest weather conditions, including planet-wide dust storms but the recent study suggests there may just be a plant on Earth capable of surviving these conditions. 

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Mars, Credit NASA

Exploring and colonising planets like Mars can enhance human sustainability. Since no life forms have been found on Mars, introducing Earth organisms might be necessary for creating suitable conditions for human life in a process known as terraforming. This will involve selecting or engineering plants that can thrive in the harsh environments of an alien world. Few studies have tested organisms’ ability to withstand extreme environments of space or Mars, focusing mainly on microorganisms, algae, and lichens. However until recently, studies including mosses and whole plants have been lacking.

There have been many long term plans and even whimsical ideas to establish settlements on Mars. Pivotal to the success is the establishment of adapted crops that can grow in controlled, synthetic environments. However, to develop such a plant requires significant progress and development before plants are capable of growing in the soils and harsh conditions. In the report by lead author Xiaoshuang Li and team the incredible resilience of a moss called Syntrichia caninervis (S. caninervis) to survive a Mars-like environment even after having lost more than 98% of its water content.

Studies into the resilience of the plants have shown they can withstand extremely low temperatures and regenerate even after being stored in a freezer at -80°C for five years or in liquid nitrogen for one month. S. caninervis also demonstrates high resistance to gamma radiation and can survive in simulated Martian conditions.

The study concluded that S. caninervis is among the most stress-tolerant organisms known. It shows how it is a real potential species for the colonisation of alien worlds like Mars. The resilience to extreme conditions such as desiccation, low temperatures, and high radiation makes it an ideal for future terraforming efforts. It helps to understand the unique properties of this moss (in particular) and how it can form a foundational layer for biologically sustainable human habitats in space.

Source : The extremotolerant desert moss Syntrichia caninervis is a promising pioneer plant for colonizing extraterrestrial environments

The post The Rugged Desert Moss Best Equipped to Survive on Mars appeared first on Universe Today.

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