FYFD

Tag: astronomy

  • Solar Eclipses and Coronal Mass Ejections

    Solar Eclipses and Coronal Mass Ejections

    Observations of many solar phenomena have only become accessible to humans relatively recently with the advent of satellites. Prior to that, it simply wasn’t feasible to observe dynamics in the sun’s atmosphere, like solar prominences or coronal mass ejections – the sun was simply too bright to see them – except during the occasional total solar eclipse!

    In the 1970s, scientists identified massive bursts of solar plasma as coronal mass ejections. These solar storms are responsible for so-called space weather and, when directed toward Earth, can pose a hazard to technologies on the ground and astronauts in orbit. Scientists initially thought this was the first time such storms had been observed, but they later recognized that photographs and sketches of an 1860 total eclipse revealed that humanity had seen a coronal mass ejection more than 100 years before! Check out the NASA video below for the full story. You can also learn about some of the science that will be going on in today’s eclipse. And, for those in the U.S. today, have a fun and safe time viewing the ecliipse!  (Image credit: S. Habbal, M. Druckmüller and P. Aniol, source; video credit: NASA Goddard)

  • Stellar Bow Shock

    Stellar Bow Shock

    This Hubble image shows a young star in the Orion Nebula and the curved bow shock arcing around it. Despite its age, the star LL Orionis is energetic, producing a stellar wind that exceeds our sun’s. When that wind collided with the flow in the Orion Nebula, it formed this bow shock that is about a half a light-year wide. We don’t often think about fluid dynamics applying in space, but if we consider a lengthscale that is large enough, even space contains enough matter to behave like a fluid. LL Orionis’s bow shock is in many ways comparable to ones we see form around re-entering spacecraft. (Image credit: NASA/Hubble, via APOD; submitted by jshoer)

  • Turbulence in the Solar Wind

    Turbulence in the Solar Wind

    One of the key features of turbulent flows is that they contain many different length scales. Look at the plume from an erupting volcano, and you’ll see eddies that are hundreds of meters across as well as tiny ones on the order of millimeters. This enormous difference in scale is one of the major challenges in simulating turbulent flows. Since energy enters at the large scale and is passed to smaller and smaller scales before being dissipated at the tiniest scales of the flow, properly simulating a turbulent flow requires resolving all of these length scales. This is especially challenging for applications like the solar wind – the  stream of charged particles that flows from the sun and gets diverted around the Earth by our magnetic field. The image above shows some of the turbulence in our solar wind. The structures seen in the flow range from the size of the Earth all the way to the scale of electrons! (Image credit: B. Loring, Berkeley Lab)

  • The Bubble Nebula

    The Bubble Nebula

    This spectacular Hubble image shows the Bubble Nebula. The source of this nebula is the star seen toward the upper left side of the bubble. This massive, super-hot star has ceased to fuse hydrogen and is now fusing helium, powering its way to a likely end as a supernova. As it burns, the star emits a stellar wind of gas moving at over 6.4 million kilometers an hour. As the flow moves outward, it encounters colder dense gases that it pushes along as it expands; this is the blue bubble surface that we see. The asymmetry of the bubble with respect to its source star is caused by the variation in the surrounding gas’s density. The bubble’s front moves more slowly in areas with more gas, thus making the bubble appear lop-sided. (Image credit: NASA; via Gizmodo)

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    5 Years of SDO

    NASA’s Solar Dynamics Observatory (SDO) is our premiere source for data on the sun. In honor of its five-year anniversary, NASA released this beautiful video compiling some of the highlights among the 2600 terabytes of data the spacecraft has recorded. SDO has captured some truly stunning footage over the years of sunspots, prominences, and eruptions. The latter two are examples of plasma flows and visible magnetohydrodynamics. SDO’s observations are also helping researchers determine what goes on just beneath the sun’s surface, where convection and buoyancy are major forces in the transport of heat generated from fusion in the star’s core. Incidentally, SDO’s launch featured some uncommonly stunning fluid dynamics as well. (Video credit: NASA Goddard)

  • Turbulence and Star Formation

    Turbulence and Star Formation

    Galaxy clusters are objects containing hundreds or thousands of galaxies immersed in hot gas. This gas glows brightly in X-ray, as seen in the Perseus (top) and Virgo (bottom) clusters above. Over time, the gas near the center of the clusters should cool, generating many new stars, but this is not what astronomers observe. New research suggests turbulence may prevent this star formation. The supermassive black holes near the center of these galaxy clusters pump enormous amounts of energy into their surroundings through jets of particles. Those jets churn the gas of the cluster, generating turbulence, which ultimately dissipates as heat. It is this turbulent heating astronomers think counters the radiative cooling of the gas, thereby keeping the gas hot enough to prevent star formation. You can read more about the findings in the research paper.  (Image credits: NASA/Chandra/I. Zhuravleva et al.; via io9)

  • Supernova Simulation

    Supernova Simulation

    New research shows that supermassive first-generation stars may explode in supernovae without leaving behind remnants like black holes. The work is a result of modeling the life and death of stars 55,000 to 56,000 times more massive than our sun. When such stars reach the end of their lives, they become unstable due to relativistic effects and begin to collapse inward. The collapse reinvigorates fusion inside the star and it begins to rapidly fuse heavier elements like oxygen, magnesium, or even iron from the helium in its core. Eventually, the energy released overcomes the binding energy of the star and it explodes outward as a supernova. The image above is a slice through such a star approximately one day after its collapse is reversed. Hydrodynamic instabilities like the Rayleigh-Taylor instability produce mixing of the heavy elements throughout the expanding interior of the star. The mixing should produce a signature that can be observed in the aftermath as these stars seed their galaxies with the heavy elements needed to form planets. For more, see Science Daily and Chen et al. (Image credit: K. Chen et al., via Science Daily; submitted by mechanicoolest)

  • Saturnian Auroras

    Saturnian Auroras

    Earth is not the only planet in our solar system with auroras. As the solar wind–a stream of rarefied plasma from our sun–blows through the solar system, it interacts with the magnetic fields of other planets as well as our own. Saturn’s magnetic field second only to Jupiter’s in strength. This strong magnetosphere deflects many of the solar wind’s energetic particles, but, as on Earth, some of the particles get drawn in along Saturn’s magnetic field lines. These lines converge at the poles, where the high-energy particles interact with the gases in the upper reaches of Saturn’s atmosphere. As a result, Saturn, like Earth, has impressive and colorful light displays around its poles. (Image credit: ESA/Hubble, M. Kornmesser & L. Calçada, source video; via spaceplasma)

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    Jupiter Timelapse

    This timelapse video shows Jupiter as seen by Voyager 1. In it, each second corresponds to approximately 1 Jupiter day, or 10 Earth hours. Be sure to fullscreen it so that you can appreciate the details. The timelapse highlights the differences in velocity (and even flow direction!) between Jupiter’s cloud bands. It is these velocity differences that create the shear forces which cause Kelvin-Helmholtz instabilities–the series of overturning eddies–seen between the bands. Earth also has bands of winds moving in opposite directions, but there are fewer of them and the composition of our atmosphere is such that they do not make for such a dramatic naked eye view of large-scale fluid dynamics. (Video credit: NASA/JPL/B. Jónsson/I. Regan)

  • Shrinking Red Spot

    Shrinking Red Spot

    Observations show Jupiter’s iconic Great Red Spot is shrinking, most recently at a rate of more than 900 km a year. As it gets smaller, the storm is also changing shape and becoming more circular. Scientists don’t yet have an explanation for the shrinkage or its recent acceleration, but this is unsurprising given the rich complexity of the storm. For example, the source of the Red Spot’s longevity–it may be more than 300 years old–is still an open topic of research. Some of the most recent observations show smaller eddies feeding into the storm; the current hypothesis is that these eddies may be increasing the Red Spot’s dissipation and accelerating its breakup. (Photo credit: NASA/ESA; h/t to io9)