I look up — many people feel small because they’re small and the Universe is big — but I feel big, because my atoms came from those stars. There’s a level of connectivity.
That’s really what you want in life, you want to feel connected, you want to feel relevant, you want to feel like a participant in the goings on of activities and events around you.
That’s precisely what we are, just by being alive…
- Dr. Neil DeGrasse Tyson [ x ]
A Burning Candle In Zero-GravityThe results of a Burning and Suppression of Solids (BASS) experiment demonstrates that in zero-gravity—where heat doesn’t rise—a flame burns in a uniform oval.
Credit: Col. Chris Hadfield
When astronomers refer to the temperature of a star, they are talking about the temperature of the gases in the photosphere, and they express those temperatures on the Kelvin temperature scale. On this scale, zero degrees Kelvin (written 0 K) is absolute zero (2273.2°C or 2459.7°F), the temperature at which an object contains no thermal energy that can be extracted. Water freezes at 273 K and boils at 373 K (at sea-level atmospheric pressure). The Kelvin temperature scale is useful in astronomy because it is based on absolute zero and consequently is related directly to the motion of the particles in an object.
Now you can understand why a hot object glows, or to put it another way, why a hot object emits photons, bundles of electromagnetic energy. The hotter an object is, the more motion there is among its particles. The agitated particles, including electrons, collide with each other, and when electrons accelerate—change their motion—part of the energy is carried away as electromagnetic radiation. The radiation emitted by a heated object is called black-body radiation, a name translated from a German term that refers to the way a perfectly opaque object would behave. A perfectly opaque object would be both a perfectly efficient absorber and a perfectly efficient emitter of radiation. At room temperature, such a perfect absorber and emitter would look black, but at higher temperatures it would glow at wavelengths visible to a human eye. That explains why in astronomy and physics contexts you will see the term black-body referring to objects that glow brightly.
Black-body radiation is quite common. In fact, it is responsible for the light emitted by an incandescent light bulb. Electricity flowing through the filament of the bulb heats it to high temperature, and it glows. You can also recognize the light emitted by hot lava as black-body radiation. Many objects in the sky, including the sun and other stars, primarily emit black-body radiation because they are mostly opaque.
Gif credit: caucasianmale
Our home planet, making a spectacle of itself. Photographed by a human living and working on the International Space Station. Credit: NASA
Prometheus creating Saturn ring streamers
What’s causing those strange dark streaks in the rings of Saturn? Prometheus. Specifically, an orbital dance involving Saturn’s moon Prometheus keeps creating unusual light and dark streamers in the F-Ring of Saturn. Now Prometheus orbits Saturn just inside the thin F-ring, but ventures into its inner edge about every 15 hours. Prometheus’ gravity then pulls the closest ring particles toward the 100-km moon. The result is not only a stream of bright ring particles but also a dark ribbon where ring particles used to be. Since Prometheus orbits faster than the ring particles, the icy moon pulls out a new streamer every pass. Sometimes, several streamers or kinks are visible at once.
Image credit: Cassini Imaging Team, ISS, JPL, ESA, NASA
Filaments in the Cygnus Loop
Subtle and delicate in appearance, these are filaments of shocked interstellar gas — part of the expanding blast wave from a violent stellar explosion. Recorded in November 1997 with the Wide Field and Planetary Camera 2 onboard the Hubble Space Telescope, the picture is a closeup of a supernova remnant known as the Cygnus Loop. The nearly edge-on view shows a small portion of the immense shock front moving toward the top of the frame at about 170 kilometers per second while glowing in light emitted by atoms of excited Hydrogen gas. Situated at over 1,440 light-years away, the Cygnus Loop is thought to have been expanding for 5 - 10 thousand years.
Image credit: William P. Blair and Ravi Sankrit (Johns Hopkins University), NASA