The Planck Space Telescope, a European Space Agency (ESA) mission in which NASA also made important contributions, spent more than four years peering at the remnant radiation left over from the Big Bang birth of our Universe almost 14 billion years ago. This relic radiation, called the Cosmic Microwave Background (CMB), is now helping astronomers to better understand the mysterious history and strange fabric of our Universe–as well as certain secrets that our own Milky Way Galaxy has kept well-hidden from the prying eyes of observers on Earth. New maps from the Planck satellite have unveiled the “polarized” light from the primordial Universe, showing that the first generation of stars caught fire 100 million years later than earlier estimates indicated. The new images of the CMB, based on data released by the Planck satellite, have revealed that the process of reionization, which ended the cosmic Dark Ages when the most ancient stars were born, started 550 million years after the Big Bang. The new data became available to the public on February 5, 2015, and now include observations made during Planck’s entire mission.
The ancient and mysterious history of our Universe is a 13.8 billion-year saga that astronomers are trying to understand. The CMB, which is the fossil light resulting from a primordial era when the baby Universe was searing-hot and unimaginably dense–only 380,000 years after the Big Bang–provides a major source of information that astronomers can use. Due to the expansion of the Universe, astronomers observe this light today covering literally the entire sky at microwave wavelengths.
“Planck can see the old light from our Universe’s birth, gas and dust in our own Galaxy, and pretty much everything in between, either directly or by its effect on the old light,” Dr. Charles Lawrence explained in a February 5, 2015 NASA Jet Propulsion Laboratory (JPL) Press Release. Dr. Lawrence is the U.S. project scientist for the Planck mission at the JPL in Pasadena, California.
There was a time, early in our Universe’s existence, when it was an incredible swath of featureless darkness. A preliminary study of the Planck data indicates that this ancient epoch took place before the first generation of stars were born to chase away with their brilliant fires this strange and murky universal night. This ancient epoch, the cosmic Dark Ages, lasted more than 100 million years–or longer. Although the Dark Ages ended 550 million years after the Big Bang, according to the new Planck data, earlier studies–conducted by astronomers using other telescopes–suggest that the cosmic Dark Ages ended 300 to 400 million years after our Universe’s birth. Research is ongoing to validate the new Planck finding.
Between 2009 and 2013, the Planck satellite surveyed the sky to study the ancient CMB light in unprecedented detail. Exquisitely tiny differences in the CMB’s temperature trace regions of slightly different density in the primordial Universe. These small temperature variations served as the “seeds” of all future structure–the stars and galaxies today.
The First Stars
The first generation of stars were unlike the stars in the Universe that we are familiar with. The first stars formed directly from the lightest of all gases–the hydrogen and helium that were synthesized in the Big Bang birth of the Universe itself (Big Bang nucleosynthesis). Many astronomers think that the first stars were gigantic, extremely bright, and that their birth was probably responsible for altering our Universe from what it once was in its infancy to what it is now. The first stars are commonly thought to be the likely precursors of the Universe’s chemical composition and structure–galaxies are believed to have formed later.
The first stars were born in the very early Universe from pristine cradles composed of clouds of light primordial gases–hydrogen, helium, and trace amounts of lithium. First-generation stars (Population III stars) are generally thought to have sparkled their way into the Cosmos before the galaxies had formed. Nevertheless, little is known about the first stars. This is because they lived fast and died young, as all massive stars do, and existed for only a wink of the Universe’s “eye”–a brief few million years. 바카라사이트
Numerical simulations conducted on supercomputers have provided scientists with insight into the ancient and mysterious formation process of Population III stars. Many of the simulations suggest that only a small percentage of these very massive, very ancient giant stars–sometimes weighing one hundred solar-masses, or more–could have been born in the ancient Universe, and instead the majority of the first stars might have been born with smaller masses of ten to a hundred times solar-mass.
The massive first stars of our Universe perished in the brilliant fires of tremendous supernovae blasts. These stellar explosions hurled the heavier atomic elements forged in the nuclear-fusing cores of the first stars shrieking into space. In this way, the newly created atomic elements were incorporated into the clouds of gas that subsequently gave birth to the next generation of stars (Population II stars). Less massive, smaller stellar sparklers–like our own Sun–can linger around for a very long time before they finally meet their inevitable doom. Smaller stars, even less massive than our Sun–that were born in the ancient Universe–may still be dazzling the Cosmos with their flames. Our large, barred-spiral Milky Way Galaxy contains just such long-lived, low-mass stellar constituents that harbor a low-metal content. All of the familiar atomic elements listed in the Periodic Table that are heavier than helium are metals in the terminology of astronomers. All of the metals in our Universe were formed in the seething, searing intense fires of the nuclear-fusing hearts of stars–or else in their explosive supernova deaths (stellar nucleosynthesis). Thus, the first generation of stars (Population III), forged the first batch of heavy atomic elements from which the galaxies and later generations of stars emerged. Our Star, the Sun, is a Population I star, a member of the glittering