Measuring Galaxy Evolution with Globular Clusters
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The galaxy NGC 4365 in the Virgo supercluster of galaxies, showing its many globular clusters (most of the more than one hundred dots in this image are actually globular star clusters). A new study of over seven thousand globular clusters around ten Virgo galaxies finds that they are often gathered into distinct groupings whose shapes reflect the formation of the clusters and the histories of the galaxies.
NASA/HST and ESO VLT
Globular clusters are gravitationally bound ensembles of stars, as many as a million stars in some cases, grouped in roughly spherical clusters with diameters as small as only tens of light-years. Globular clusters are typically located in the outer regions (the halos) of galaxies; the Milky Way galaxy has about two hundred globular clusters orbiting it. Astronomers are interested in globular clusters in part because they are home to many of the oldest known stars, but also because of their locations in the halos. Collisions between galaxies are commonplace, and globular clusters may provide fossil evidence of these encounters because they are strongly affected by such interactions. During a collision, a galaxy can grow by absorbing or merging with its neighbor, and some models predict that clusters form during these interactions. Moreover, it is possible that in a merger large numbers of globular clusters originally belonging to a smaller galaxy may be captured by the larger galaxy. In any case, the distribution of globular clusters around a galaxy holds clues to their origins and the history of its host galaxy.
The Virgo Cluster of galaxies, containing between one and two thousand galaxies, is located about fifty-four million light-years away in the direction of the constellation of Virgo. The ten brightest galaxies of the Virgo Cluster alone contain 7053 detected globular clusters. CfA astronomers Raffaele D'Abrusco, Pepi Fabbiano, and Andreas Zezas carefully examined this set of globular clusters looking for information about the history of these galaxies. In a new paper, they report discovering distinctive structures among the globular cluster systems, meaning that the globular clusters around these galaxies are not distributed symmetrically. Their configurations often take shapes ranging from roughly linear to circular, with some more complex shapes as well. The scientists found 229 such structures in this subsample, forty-two of them classified as being medium or large and stretching over as much as seventy-five thousand light-years. The elongated structures tend to be aligned with an axis of the host galaxy, as would be expected if a merger were responsible.
The scientists argue that these structures are indeed the remnants of galaxies that were accreted in the past, and among other things they estimate limits on the masses of these parent galaxies. Computer simulations provide some rough level of agreement. The authors note that with more detailed computations, these structures offer a powerful new tool to advance the study of galaxy evolution.
"Spatial Structures in the Globular Cluster Distribution of the Ten Brightest Virgo Galaxies," R. D'Abrusco, G. Fabbiano, A. Zezas, ApJ 2015 (in press)
Magnesium: Connecting Human and Planetary Health to the Stars
Posted by Daniel Henryk Rasolt | Mar 10, 2019
Magnesium: Connecting Human and Planetary Health to the Stars
Our Elemental Origins
It is easy for us humans – with our self-proclaimed superior intelligence over other species, and ability to innovate and exploit the natural world to our whims – to forget or ignore that we are in fact part of nature. This is not solely an existential statement, or even an acknowledgement of the dependency that we have on nature for our long-term survival as a species. From our behaviors and physiology, to the very molecules, elements and atoms that makeup the cells of our body, we are nature!
One must even expand the meaning of “the natural world” to truly appreciate where we come from. The history of those aforementioned atoms and elements in particular, extends well beyond the evolution of our species, and even beyond the evolution of our planet and solar system. The fundamental building blocks that makeup our bodies and the diverse and beautiful planet that we depend upon, are born from the cosmos.
To illustrate this interconnectedness between our existence and health, the natural world here on earth, and the vast universe, let us focus in this article on one specific element: magnesium. But before we do so, let’s give a shout-out to carbon, iron, gold and so many other elements whose multi-billion year biographies can also uniquely illustrate the connection between our present reality as resource consuming earthlings and the high-energy events that have happened during the evolution of the universe.
Magnesium
Magnesium is a metal with the atomic number 12, and is believed to be the 9th most prevalent element in the universe. Magnesium is the 8th most abundant element found in the earth’s crust, which is made up of approximately two percent magnesium through a range of compounds (it does not occur on its own naturally on earth).
Magnesium is also the third most dissolved element in seawater, and is an important component of chlorophyll molecules. Chlorophyll is found in plants and algae, and is vital in converting sunlight into energy through photosynthesis. This energy (calories) sustains biological life on earth, including our own.
Magnesium is produced through a nuclear fusion reaction of three helium atoms and carbon within massive aging stars. As these stars die, they expel their elemental contents into the universe.
For particularly massive stars, high-energy supernova explosions occur, either through a runaway nuclear reaction (type 1 supernovae) or by a star collapsing under its own gravity after burning up all of its nuclear fuel (type 2 supernovae). In both cases, the resulting supernova explosion expels the inner contents that formed under nuclear fusion within the previously massive star, far and wide.
Iron, sulfur, nickel, silicon, carbon and magnesium, are just a few examples of elements that populate our planet and universe due to this powerful process. The quantity of these elements coming from any particular supernova depends upon: the size, energy and velocity of the explosion, its distance away from us, and the makeup of the intergalactic and interstellar medium between the explosion and our solar system. The result: Around 4.5 billion years ago, the remnants of supernova explosions helped to form our solar system, planet, and eventually us.
The Magnesium-Food-Health Connection
Every cell of the human body contains and depends upon magnesium. Proper nerve and muscle function, bone strength, blood flow and heart rate – all could not take place in the absence of magnesium.
The synthesis of proteins, production of energy, signaling between cells, and many other “physiological pathways” within the human body, become diminished without a sufficient amount of magnesium. In nutritional and physiological terms, magnesium is referred to as an “essential mineral and a cofactor for hundreds of enzymes,” as well as a micronutrient.
Deficiency of magnesium in the body has been connected to cardiovascular disease (CVD), osteoporosis, and metabolic diseases like type 2 diabetes. Conversely, magnesium has been shown to increase insulin sensitivity, making it an important “nutrient” for both preventing and managing metabolic diseases.
According to the National Institute of Health (NIH), adult females should consume at least 310 to 320 milligrams of magnesium in their daily diet, while adult males should consume 400 to 420 milligrams of magnesium daily. Highly refined and processed foods have much lower magnesium content than the whole foods they are derived from. So a typical “Western Diet” – high in processed foods and beverages – can indeed lead to magnesium deficiency, as well as deficiency in other valuable macro and micronutrients.
Magnesium deficiency is just another factor that connects these western diets to metabolic diseases. Furthermore, people with kidney disease (nephropathy) are more likely to suffer from “magnesium wasting,” or excessive loss of magnesium in urine. This can create a dangerous feedback loop, where low magnesium levels decrease insulin sensitivity, exacerbating kidney disease, which can further reduce magnesium levels in people with metabolic diseases.
Foods high in fiber, such as dark leafy greens, whole grains, legumes, nuts and seeds, and even dark chocolate and certain kinds of seafood and meat, contain substantial amounts of magnesium. Magnesium supplements, which have been all the rage in recent years as part of the growing multi-billion dollar supplement industry, are both unnecessary for healthy individuals and mostly unproven as to their benefits. Furthermore, these supplements do nothing to address the preventable cause of magnesium deficiency, which is eating an unhealthy and unbalanced diet that lacks in whole foods.
Lower levels of magnesium in foods becomes even more pronounced when the foods (both whole and processed) come from industrial monocultures, whose uniformity reduces biodiversity, and whose chemically fertilized soils contain a reduced diversity of microorganisms, and minerals like magnesium.
Magnesium is considered a “secondary macronutrient” for plants, meaning it is critical to plant growth and health. Magnesium availability to plants comes principally from the soil, so a degraded or otherwise unhealthy soil will result in plants and seeds with diminished magnesium content. This subsequently has negative impacts on human health when these nutrient-deficient crops are consumed.
Since most life on this planet depends on chlorophyll and photosynthesis for energy (and breathable air), both plants and animals contain magnesium, so consuming a balanced diet based on whole foods that are grown sustainably, should provide a sufficient amount of magnesium for most people.
An Interconnected Perspective
Magnesium is a great illustrator of the complex connection between our health, the health of the planet, and the beautiful cosmos where the components of life were born. We should appreciate the great abundance and diversity that sustains us and other life, and not lose sight of the amazing depths to which our own existence owes its presence.
The stars made us, the planet has sustained us, and in a cosmological quarter-blink of an eye, our species has attacked the very processes and diversity that keeps us alive and healthy
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