On Stories, Leaving A Mark, And Wanting To Be Remembered

Bioluminescent Plankton

Scientists have only recently discovered that this type of plankton glows when they are moved because of stress - ironic when you consider how relaxing the sight of the shimmering waves are in the dark night. Bioluminescence is used as a defence mechanism to draw predators towards the creature trying to eat the plankton. The tiny flashes of light also disorientate and surprise the predator.

These tiny organisms produce light using a chemical called luciferin. The process of creating a bioluminescent light, which is simply light produced within a living creature, differs between organisms. Some need a particular food or another creature for the effect to happen. But this type of plankton, called dinoflagellates, produce luciferin on their own. The light the tiny plankton emit is called ‘cold light’, meaning less than 20% of the light generates heat.

Huge areas of the ocean can become populated by glowing plankton but the effect is especially common in warm-water lagoons that have narrow openings to the sea. This causes the plankton to gather and become trapped, causing the water to turn orange.

Image credit: Will Ho, Kin Cheung, Landscapes Maldives & eyegami

Source: Kuoni

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you have encountered a group of trilobites! reblog to help them on their journey

The Himalayan plateau, as seen from the ISS by europeanspaceagency

Can you believe this monster snake actually existed?

Titanoboa is an extinct genus of very large snakes that lived in what is now La Guajira in northeastern Colombia. They could grow up to 12.8 m long and reach a weight of 1,135 kg. Fossils of Titanoboa have been found in the Cerrejón Formation, and date to around 58 to 60 million years ago.

Titanoboa skeleton on display at Queensland Art Gallery

Cassini spacecraft captured this image of Saturn and Titan

Solar Winds

Great Basin National Park in Nevada is one of the darkest spots in the United States. What better time to appreciate this park’s clear night sky, then on International Day of Clean Air? Good air quality coupled with a lack of light pollution give visitors majestic starry views of Wheeler Peak. On clear, moonless nights at Great Basin, thousands of stars, numerous planets, star clusters, meteors, man-made satellites, the Andromeda Galaxy, and the Milky Way can be seen with the naked eye. The area boasts some of the darkest night skies left in the country. Low humidity, good air quality, and minimal light pollution, combined with high elevation, create a unique window to the universe. Photo by John Vermette (sharetheexperience.org). Photo description: A bright Milky Way and night sky filled with stars light up the mountains below.

50 Foot Long Congo Snake

In 1959 Remy Van Lierden was flying over the Katanga region in the Democratic Republic of the Congo. He was flying a helicopter and returning to the base that he commanded in Kamina. As he passed over a clearing in the jungle he noticed a large animal laying out in the sun. What he saw was a 50 foot long snake, with green and brown scales. He couldn’t believe his eyes and neither could his passengers. He circled around and made several passes off the monstrous snake, however he flew away when it got into the striking position and thought it was too dangerous to contour to fly over the animal. During one of the passes he made a passenger on his aircraft snapped this picture to prove what they saw. The snake in question is clearly large and it’s easy to see how it could have been a threat to a low flying helicopter. It’s believed that the snake is a Titanoboa which is thought to be extinct, and has been for millions of years. But it’s possible that the species may have survived. The natives claim that the snake pictured here is a small one and that they can get up to twice and three times the size.

Stars

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

How do stars form?

Stars are born within the clouds of dust and scattered throughout most galaxies. A familiar example of such as a dust cloud is the Orion Nebula.

Turbulence deep within these clouds gives rise to knots with sufficient mass that the gas and dust can begin to collapse under its own gravitational attraction. As the cloud collapses, the material at the center begins to heat up. Known as a protostar, it is this hot core at the heart of the collapsing cloud that will one day become a star.

Three-dimensional computer models of star formation predict that the spinning clouds of collapsing gas and dust may break up into two or three blobs; this would explain why the majority the stars in the Milky Way are paired or in groups of multiple stars.

As the cloud collapses, a dense, hot core forms and begins gathering dust and gas. Not all of this material ends up as part of a star — the remaining dust can become planets, asteroids, or comets or may remain as dust.

In some cases, the cloud may not collapse at a steady pace. In January 2004, an amateur astronomer, James McNeil, discovered a small nebula that appeared unexpectedly near the nebula Messier 78, in the constellation of Orion. When observers around the world pointed their instruments at McNeil’s Nebula, they found something interesting — its brightness appears to vary. Observations with NASA’s Chandra X-ray Observatory provided a likely explanation: the interaction between the young star’s magnetic field and the surrounding gas causes episodic increases in brightness.

Main Sequence Stars

A star the size of our Sun requires about 50 million years to mature from the beginning of the collapse to adulthood. Our Sun will stay in this mature phase (on the main sequence as shown in the Hertzsprung-Russell Diagram) for approximately 10 billion years.

Stars are fueled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight, and the energy by which it shines.

As shown in the Hertzsprung-Russell Diagram, Main Sequence stars span a wide range of luminosities and colors, and can be classified according to those characteristics. The smallest stars, known as red dwarfs, may contain as little as 10% the mass of the Sun and emit only 0.01% as much energy, glowing feebly at temperatures between 3000-4000K. Despite their diminutive nature, red dwarfs are by far the most numerous stars in the Universe and have lifespans of tens of billions of years.

On the other hand, the most massive stars, known as hypergiants, may be 100 or more times more massive than the Sun, and have surface temperatures of more than 30,000 K. Hypergiants emit hundreds of thousands of times more energy than the Sun, but have lifetimes of only a few million years. Although extreme stars such as these are believed to have been common in the early Universe, today they are extremely rare - the entire Milky Way galaxy contains only a handful of hypergiants.

Stars and Their Fates

In general, the larger a star, the shorter its life, although all but the most massive stars live for billions of years. When a star has fused all the hydrogen in its core, nuclear reactions cease. Deprived of the energy production needed to support it, the core begins to collapse into itself and becomes much hotter. Hydrogen is still available outside the core, so hydrogen fusion continues in a shell surrounding the core. The increasingly hot core also pushes the outer layers of the star outward, causing them to expand and cool, transforming the star into a red giant.

If the star is sufficiently massive, the collapsing core may become hot enough to support more exotic nuclear reactions that consume helium and produce a variety of heavier elements up to iron. However, such reactions offer only a temporary reprieve. Gradually, the star’s internal nuclear fires become increasingly unstable - sometimes burning furiously, other times dying down. These variations cause the star to pulsate and throw off its outer layers, enshrouding itself in a cocoon of gas and dust. What happens next depends on the size of the core.

Average Stars Become White Dwarfs

For average stars like the Sun, the process of ejecting its outer layers continues until the stellar core is exposed. This dead, but still ferociously hot stellar cinder is called a White Dwarf. White dwarfs, which are roughly the size of our Earth despite containing the mass of a star, once puzzled astronomers - why didn’t they collapse further? What force supported the mass of the core? Quantum mechanics provided the explanation. Pressure from fast moving electrons keeps these stars from collapsing. The more massive the core, the denser the white dwarf that is formed. Thus, the smaller a white dwarf is in diameter, the larger it is in mass! These paradoxical stars are very common - our own Sun will be a white dwarf billions of years from now. White dwarfs are intrinsically very faint because they are so small and, lacking a source of energy production, they fade into oblivion as they gradually cool down. This fate awaits only those stars with a mass up to about 1.4 times the mass of our Sun. Above that mass, electron pressure cannot support the core against further collapse. Such stars suffer a different fate as described below.

Supernovae Leave Behind Neutron Stars or Black Holes 

Main sequence stars over eight solar masses are destined to die in a titanic explosion called a supernova. A supernova is not merely a bigger nova. In a nova, only the star’s surface explodes. In a supernova, the star’s core collapses and then explodes. In massive stars, a complex series of nuclear reactions leads to the production of iron in the core. Having achieved iron, the star has wrung all the energy it can out of nuclear fusion - fusion reactions that form elements heavier than iron actually consume energy rather than produce it. The star no longer has any way to support its own mass, and the iron core collapses. In just a matter of seconds the core shrinks from roughly 5000 miles across to just a dozen, and the temperature spikes 100 billion degrees or more. The outer layers of the star initially begin to collapse along with the core, but rebound with the enormous release of energy and are thrown violently outward. Supernovae release an almost unimaginable amount of energy. For a period of days to weeks, a supernova may outshine an entire galaxy. Likewise, all the naturally occurring elements and a rich array of subatomic particles are produced in these explosions. On average, a supernova explosion occurs about once every hundred years in the typical galaxy. About 25 to 50 supernovae are discovered each year in other galaxies, but most are too far away to be seen without a telescope.

Neutron Stars

If the collapsing stellar core at the center of a supernova contains between about 1.4 and 3 solar masses, the collapse continues until electrons and protons combine to form neutrons, producing a neutron star. Neutron stars are incredibly dense - similar to the density of an atomic nucleus. Because it contains so much mass packed into such a small volume, the gravitation at the surface of a neutron star is immense.

Neutron stars also have powerful magnetic fields which can accelerate atomic particles around its magnetic poles producing powerful beams of radiation. Those beams sweep around like massive searchlight beams as the star rotates. If such a beam is oriented so that it periodically points toward the Earth, we observe it as regular pulses of radiation that occur whenever the magnetic pole sweeps past the line of sight. In this case, the neutron star is known as a pulsar.

Black Holes

If the collapsed stellar core is larger than three solar masses, it collapses completely to form a black hole: an infinitely dense object whose gravity is so strong that nothing can escape its immediate proximity, not even light. Since photons are what our instruments are designed to see, black holes can only be detected indirectly. Indirect observations are possible because the gravitational field of a black hole is so powerful that any nearby material - often the outer layers of a companion star - is caught up and dragged in. As matter spirals into a black hole, it forms a disk that is heated to enormous temperatures, emitting copious quantities of X-rays and Gamma-rays that indicate the presence of the underlying hidden companion.

From the Remains, New Stars Arise

The dust and debris left behind by novae and supernovae eventually blend with the surrounding interstellar gas and dust, enriching it with the heavy elements and chemical compounds produced during stellar death. Eventually, those materials are recycled, providing the building blocks for a new generation of stars and accompanying planetary systems.

Credit and reference: science.nasa.gov 

image credit: ESO, NASA, ESA, Hubble

Wow, it’s Friday! Have a great weekend. 

Dunkleosteus model featured in ep. 12 of Shelf Life: 6 Extinctions in 6 Minutes.