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Three Goblin Art
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Aqua Utopiaïœæ”·ăźćșă§èšæ¶ă玥ă
Claire Keane

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Today's Document
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Lint Roller? I Barely Know Her
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Sweet Seals For You, Always
YOU ARE THE REASON
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Monterey Bay Aquarium

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Kurt Herschel - Weinbergschnecken. (Helix pomatia) bei der Paarung. Jena, um 1925
Fallen Angel - Alexandre Cabanel
Swimmer Kathy Flicker spitting water while in swimming pool looking like her head is detached from her underwater body due to refraction of water, 1962 - by George Silk (1916 - 2004), New Zealander
The Lives, Times, and Deaths of Stars
Who among us doesnât covertly read tabloid headlines when we pass them by? But if youâre really looking for a dramatic story, you might want to redirect your attention from Hollywoodâs stars to the real thing. From birth to death, these burning spheres of gas experience some of the most extreme conditions our cosmos has to offer.
All stars are born in clouds of dust and gas like the Pillars of Creation in the Eagle Nebula pictured below. In these stellar nurseries, clumps of gas form, pulling in more and more mass as time passes. As they grow, these clumps start to spin and heat up. Once they get heavy and hot enough (like, 27 million degrees Fahrenheit or 15 million degrees Celsius), nuclear fusion starts in their cores. This process occurs when protons, the nuclei of hydrogen atoms, squish together to form helium nuclei. This releases a lot of energy, which heats the star and pushes against the force of its gravity. A star is born.
Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)
From then on, starsâ life cycles depend on how much mass they have. Scientists typically divide them into two broad categories: low-mass and high-mass stars. (Technically, thereâs an intermediate-mass category, but weâll stick with these two to keep it straightforward!)
Low-mass stars
A low-mass star has a mass eight times the Sunâs or less and can burn steadily for billions of years. As it reaches the end of its life, its core runs out of hydrogen to convert into helium. Because the energy produced by fusion is the only force fighting gravityâs tendency to pull matter together, the core starts to collapse. But squeezing the core also increases its temperature and pressure, so much so that its helium starts to fuse into carbon, which also releases energy. The core rebounds a little, but the starâs atmosphere expands a lot, eventually turning into a red giant star and destroying any nearby planets. (Donât worry, though, this is several billion years away for our Sun!)
Red giants become unstable and begin pulsating, periodically inflating and ejecting some of their atmospheres. Eventually, all of the starâs outer layers blow away, creating an expanding cloud of dust and gas misleadingly called a planetary nebula. (There are no planets involved.)
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
All thatâs left of the star is its core, now called a white dwarf, a roughly Earth-sized stellar cinder that gradually cools over billions of years. If you could scoop up a teaspoon of its material, it would weigh more than a pickup truck. (Scientists recently found a potential planet closely orbiting a white dwarf. It somehow managed to survive the starâs chaotic, destructive history!)
High-mass stars
A high-mass star has a mass eight times the Sunâs or more and may only live for millions of years. (Rigel, a blue supergiant in the constellation Orion, pictured below, is 18 times the Sunâs mass.)
Credit: Rogelio Bernal Andreo
A high-mass star starts out doing the same things as a low-mass star, but it doesnât stop at fusing helium into carbon. When the core runs out of helium, it shrinks, heats up, and starts converting its carbon into neon, which releases energy. Later, the core fuses the neon it produced into oxygen. Then, as the neon runs out, the core converts oxygen into silicon. Finally, this silicon fuses into iron. These processes produce energy that keeps the core from collapsing, but each new fuel buys it less and less time. By the point silicon fuses into iron, the star runs out of fuel in a matter of days. The next step would be fusing iron into some heavier element, but doing requires energy instead of releasing it. Â
The starâs iron core collapses until forces between the nuclei push the brakes, and then it rebounds back to its original size. This change creates a shock wave that travels through the starâs outer layers. The result is a huge explosion called a supernova.
Whatâs left behind depends on the starâs initial mass. Remember, a high-mass star is anything with a mass more than eight times the Sunâs â which is a huge range! A star on the lower end of this spectrum leaves behind a city-size, superdense neutron star. (Some of these weird objects can spin faster than blender blades and have powerful magnetic fields. A teaspoon of their material would weigh as much as a mountain.)
At even higher masses, the starâs core turns into a black hole, one of the most bizarre cosmic objects out there. Black holes have such strong gravity that light canât escape them. If you tried to get a teaspoon of material to weigh, you wouldnât get it back once it crossed the event horizon â unless it could travel faster than the speed of light, and we donât know of anything that can! (Weâre a long way from visiting a black hole, but if you ever find yourself near one, there are some important safety considerations you should keep in mind.)
The explosion also leaves behind a cloud of debris called a supernova remnant. These and planetary nebulae from low-mass stars are the sources of many of the elements we find on Earth. Their dust and gas will one day become a part of other stars, starting the whole process over again.
Thatâs a very brief summary of the lives, times, and deaths of stars. (Remember, thereâs that whole intermediate-mass category we glossed over!) To keep up with the most recent stellar news, follow NASA Universe on Twitter and Facebook.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
Walmsley Brothers - A Lonely Valley, 1890
Tracking the Sunâs Cycles
Scientists just announced that our Sun is in a new cycle.
Solar activity has been relatively low over the past few years, and now that scientists have confirmed solar minimum was in December 2019, a new solar cycle is underway â meaning that we expect to see solar activity start to ramp up over the next several years.
The Sun goes through natural cycles, in which the star swings from relatively calm to stormy. At its most active â called solar maximum â the Sun is freckled with sunspots, and its magnetic poles reverse. At solar maximum, the Sunâs magnetic field, which drives solar activity, is taut and tangled. During solar minimum, sunspots are few and far between, and the Sunâs magnetic field is ordered and relaxed.
Understanding the Sunâs behavior is an important part of life in our solar system. The Sunâs violent outbursts can disturb the satellites and communications signals traveling around Earth, or one day, Artemis astronauts exploring distant worlds. Scientists study the solar cycle so we can better predict solar activity.
Measuring the solar cycle
Surveying sunspots is the most basic of ways we study how solar activity rises and falls over time, and itâs the basis of many efforts to track the solar cycle. Around the world, observers conduct daily sunspot censuses. They draw the Sun at the same time each day, using the same tools for consistency. Together, their observations make up the international sunspot number, a complex task run by the World Data Center for the Sunspot Index and Long-term Solar Observations, at the Royal Observatory of Belgium in Brussels, which tracks sunspots and pinpoints the highs and lows of the solar cycle. Some 80 stations around the world contribute their data.
Credit: USET data/image, Royal Observatory of Belgium, Brussels
Other indicators besides sunspots can signal when the Sun is reaching its low. In previous cycles, scientists have noticed the strength of the Sunâs magnetic field near the poles at solar minimum hints at the intensity of the next maximum. When the poles are weak, the next peak is weak, and vice versa.
Another signal comes from outside the solar system. Cosmic rays are high-energy particle fragments, the rubble from exploded stars in distant galaxies that shoot into our solar system with astounding energy. During solar maximum, the Sunâs strong magnetic field envelops our solar system in a magnetic cocoon that is difficult for cosmic rays to infiltrate. In off-peak years, the number of cosmic rays in the solar system climbs as more and more make it past the quiet Sun. By tracking cosmic rays both in space and on the ground, scientists have yet another measure of the Sunâs cycle.
Since 1989, an international panel of expertsâsponsored by NASA and NOAAâmeets each decade to make their prediction for the next solar cycle. The prediction includes the sunspot number, a measure of how strong a cycle will be, and the cycleâs expected start and peak. This new solar cycle is forecast to be about the same strength as the solar cycle that just ended â both fairly weak. The new solar cycle is expected to peak in July 2025.
Learn more about the Sunâs cycle and how it affects our solar system at nasa.gov/sunearth.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
American model Sarah McDaniel (32C-24-36, 5 ft 10 in, 1995- ) was the cover girl for Playboy magazineâs first non-nude issue in 2016. You might also have noticed that her eyes are different colors (left: light blue, right: yellow-brown).
Update: several followers tell me that her blue eye color may be the result of a contact lens.
Every night I still ask the Lord, âWhy?â and havenât heard a decent answer yetâ -Â Jack Kerouac, Desolation Angels
UFO magazine cover. Kosmologi. September 1960.
Internet Archive
The Continuing Search
Jack Kerouac (1966)
© Farabola/Leemage/AFP
Lou Reed for Coney Island Baby, 1975, by Mick Rock.
âPigeon feeding near Blue Mosqueâ, 1991 Â // Â Steve McCurry
âPolished silicate rocks.â Nos terrains. 1898.
Gallica
Fruit postcard, Paul Huf, 1983