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Spherical Ethylene Diffusion Flame in Microgravity

This is an image of a spherical diffusion flame of ethylene burning in air in the NASA GRC 2.2 s drop tower. The image was recorded about 1.4 s after ignition. The ethylene flowrate is 1.5 mg/s and the scale is revealed by the 6.5 mm porous sphere visible in the image. The image was recorded using a Nikon D100 digital single-lens reflex camera with a 125 ms exposure.

Credit: P.B. Sunderland (University of Maryland), D.L. Urban and D.P. Stocker (NASA Glenn Research Center), B.H. Chao (University of Hawaii) and R.L. Axelbaum (Washington University)

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Ternary Flame

This image shows a ternary flame system with a Santoro burner below a ring burner. The steady soot column generated by the acetylene diffusion flame passes into the hydrogen ring flame, where it is oxidized. This allows soot oxidation to be studied in the absence of soot formation. The camera is a Nikon D100 digital still camera at 6.1 megapixels. This research is supported by NSF.

Credit: H. Guo, P.M. Anderson, P.B. Sunderland (University of Maryland)

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Sonoluminescence: How Bubbles Turn Sound into Light

Sonoluminescence is a phenomenon that occurs when a small gas bubble is acoustically suspended and periodically driven in a liquid solution at ultrasonic frequencies, resulting in bubble collapse, cavitation, and light emission. The thermal energy that is released from the bubble collapse is so great that it can cause weak light emission. The mechanism of the light emission remains uncertain, but some of the current theories, which are categorized under either thermal or electrical processes, are Bremsstrahlung radiation, argon rectification hypothesis., and hot spot. People are beginning to lean more towards thermal processes as temperatures have consistently been proven with different methods of spectral analysis. In order to understand the light emission mechanism, it is important to know what is happening in the bubble’s interior and at the bubble’s surface.

The inertia of a collapsing bubble generates high pressures and temperatures capable of ionizing a small fraction of the noble gas within the volume of the bubble. This small fraction of ionized gas is transparent and allows for volume emission to be detected. Free electrons from the ionized noble gas begin to interact with other neutral atoms causing thermal bremsstrahlung radiation. Surface emission emits a more intense flash of light with a longer duration and is dependent on wavelength. Experimental data suggest that only volume emission occurs in the case of sonoluminescence. As the sound wave reaches a low energy trough the bubble expands and electrons are able to recombine with free ions and halt light emission. Light pulse time is dependent on the ionization energy of the noble gas with argon having a light pulse of 160 picoseconds.

Although the bubble above is illuminated with a floodlight that is shining directly into the camera the flash of light – sonoluminescence is easily seen as the bubble reaches its minimum radius.

Watch the video: here

Credit: Seth Putterman

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Dark Nebula LDN 810

This image was obtained with the wide-field view of the Mosaic camera on the Mayall 4-meter telescope at Kitt Peak National Observatory.

LDN 810 is a dark nebula that was first cataloged by B.T. Lynds in 1962. The dark region at the center contains gas and dust out of which new stars are forming. A bipolar outflow of gas from one of these stars has also been detected.

A faint trail of dust and gas extends from the center of the image to the upper-left corner. The image was generated with observations in the Us (violet), B (blue), V (green) and I (red) filters. In this image, North is up, East is to the left.