- 3767 - STARDUST - what people are made of? Science has said humans are made of stardust, and now, a new survey of 150,000 stars shows just how true the old cliché is: Humans and their galaxy have about 97 percent of the same kind of atoms, and the elements of life appear to be more prevalent toward the galaxy's center.
--------------------- 3767 - STARDUST - what people are made of?
- The crucial elements for life on Earth, the building blocks of life, can be abbreviated as CHNOPS: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. For the first time, astronomers have cataloged the abundance of these elements in a huge sample of stars.
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- The astronomers evaluated each element's abundance through “spectroscopy“; each element emits distinct wavelengths of light from within a star, and they measured the depth of the dark and bright patches in each star's light spectrum to determine what it was made of.
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- They used stellar measurements from the Sloan Digital Sky Survey's (SDSS) Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph in New Mexico. APOGEE can peer through the dust in the Milky Way because it uses infrared wavelengths, which pass through dust.
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- This instrument collects light in the near-infrared part of the electromagnetic spectrum and disperses it, like a prism, to reveal signatures of different elements in the atmospheres of stars.
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- A fraction of the almost 200,000 stars surveyed by APOGEE overlap with the sample of stars targeted by the NASA Kepler mission, which was designed to find potentially Earth-like planets.
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- Although humans share most elements with the stars, the proportions of those elements differ between humans and stars. Humans are about 65 percent oxygen by mass, whereas oxygen makes up less than 1 percent of all elements measured in space and in the spectra of stars.
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- The six most common elements of life on Earth (including more than 97 percent of the mass of a human body) are carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus. Those same elements are abundant at the center of our Milky Way galaxy.
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- The proportion of each element of life differed depending on the region of the galaxy in which it was found. For example, the sun resides on the outskirts of one of the Milky Way's spiral arms. Stars on the outskirts of the galaxy have fewer heavy elements required for life's building blocks, such as oxygen, than those in more central regions of the galaxy.
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- In January, 2006, a conical capsule carrying the first samples of a comet and the first pristine traces of interstellar dust ever collected landed in the Utah desert. The capsule had been dropped from NASA's Stardust spacecraft, which continued its voyage through space and became the first mission to visit two comets.
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- Launched in 1999, “Stardust” visited an asteroid before making a close brush with “Comet Wild 2“, then returned to Earth to deposit the samples. As part of its extended mission, the box-shaped craft visited “Comet Tempel 1“. When the mission ended, in March, 2011, the spacecraft had traveled nearly 5.7 billion miles over the course of nearly 12 years.
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- Although the mission has come to a close, researchers are still hunting down the dust particles embedded in material carried by the capsule that returned to Earth more than a decade ago.
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- The Stardust was a boxy craft that carried two solar arrays, along with a 101 pounds sample-return capsule that was dropped into Earth's atmosphere, carrying samples of comet and interstellar dust. The spaceship carried two dedicated science instruments and several engineering instruments required for spacecraft operation that also collected scientific data:
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- The aerogel dust collectors were two tennis-racket-shaped collectors capable of extending from and retracting into the spacecraft. The aerogel covering the collectors kept dust particles pristine as they slowed from high speeds to a dead stop. One side of a collector gathered material from Wild 2 while the other side sampled material encountered as Stardust traveled through space.
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- The Cometary and Interstellar Dust Analyzer (CIDA) determined the composition of individual dust grains that collided with a silver impact plate.
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- The Navigation Camera targeted the comet, collecting high-resolution images.
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- The Dust Flux Monitors monitored the flux and size distribution of particles in Stardust's environment.
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- After a three billion-mile journey to rendezvous with a comet, the Stardust return capsule joins the national collection of flight icons at the National Air and Space Museum.
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- The crown jewel of Stardust's instruments was the sample-gathering aerogel. The product is a silicon-based solid with a porous, sponge-like structure and consists mostly of empty space. Because the particles that Stardust aimed to sample were traveling at up to six times the speed of a rifle bullet, a high-speed capture in a conventional collector could alter the particles' shape and chemical composition. But when the high-speed particles hit aerogel, they were captured with minimal heating or chemical alteration.
Capturing the particles in aerogel was a little bit like collecting BBs by shooting them into Styrofoam.
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- Each particle created a carrot-shaped track up to 200 times the particle's length in the aerogel, allowing scientists to trace the particles' paths through the mostly transparent material.
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- Stardust's primary science objectives included making a flyby of Wild 2 at a velocity low enough that samples could be collected for return and interstellar dust particles could be collected. This would also allow the return of as many high-resolution images as possible of the comet's nucleus and the surrounding shell of gas, or coma.
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- On its way to Wild 2, Stardust collected interstellar dust material older than the solar system. In 2003, the probe flew within 2,050 miles of the asteroid 5535 Annefrank. The mission team used the tiny asteroid as a preliminary run and an attempt to improve Stardust’s flyby accuracy while collecting images of Annefrank.
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- Stardust entered the coma of Wild 2 on December 31, 2003, and made its closest approach on January 2, 2004, passing within 155 miles of the comet. At that point, the spacecraft was 1.85 times the Earth-sun distance from the sun.
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- The sample collector was extended on December 24, and after collecting all the material possible, it was sealed in the sample vault of the re-entry capsule only 6 hours after the flyby.
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- In January 2006, Stardust dropped its conical capsule into the Earth's atmosphere. The capsule landed at the U.S. Air Force Test and Training Range in the Utah desert. Within two days, the capsule was transferred to the Johnson Space Center in Houston, where researchers began the long hunt through aerogel for signs of the tiny particles.
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- Back in space, Stardust was placed into hibernation until it was funded for an extended mission called the New Exploration of Tempel 1 (NExT). A year earlier, in 2005, NASA's Deep Impact spacecraft observed Tempel 1 and crashed a probe into it. The Stardust-NExT mission returned to Tempel 1 to continue mapping the comet and examine how the impact crater had changed.
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- When Stardust flew by its second target, on February 14, 2011, the probe became the first spacecraft to visit two comets, while Comet Tempel 1 became the first comet visited by two space probes. Stardust's images revealed that much of the material blown out of the nucleus by Deep Impact had fallen back into the crater, suggesting that the heart of the comet wasn’t as tightly held together as previously believed.
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- On March 25, 2011, Stardust's extended mission ended. The spacecraft continues to orbit the sun, and NASA predicts that the probe will never get closer than 1.7 million miles to Earth's orbit.
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- Like most comets, Wild 2 is a fossil of planetary formation. For most of its life, it orbited between Jupiter and Uranus, but a brush with Jupiter in 1974 moved the comet to an orbit closer to the sun. By the time Stardust visited the comet, Wild 2 had made only five close encounters with the sun, which meant that the comet was in roughly the same condition as when it was formed with the solar system, some 4.5 billion years ago.
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- Stardust's samples helped researchers discover a new class of organics, captured by the dust particles, that was more primitive than those spotted in meteorites. Scientists also found irregular particles known as calcium-aluminum-rich inclusions (CAIs). CAIs are the oldest solar system materials and are composed of exotic compounds that form at very high temperatures.
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- The team also discovered a handful of interstellar particles, the first ever collected in space and returned to Earth for study. These particles drifted into the solar system from the region between stars and were likely formed before the sun was made. Finding them involves combing through millions of images of interstellar material captured by Stardust. Citizen scientists continue to help hunt for the particles by searching through millions of images
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- Your stardust has evolved into excellent reading and comprehension material. Learning where you came from. But, not why, not how, ………..
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November 30, 2022 STARDUST - what people are made of? 3767
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