First Stars

Why Finding The First Stars In Our Universe Puts Us Closer To The Big Bang

Anonymous — Mon, 12 Mar 2018 19:28:38 +0000

Why Finding The First Stars In Our Universe Puts Us Closer To The Big Bang Anonymous (not verified) Mon, 03/12/2018 - 13:28

Nell London

From babyֱ��app Public Radio: Astronomers have detected the first stars ever to shine in the universe, an event that happened more than 13 billion years ago. No one’s actually seen them -- scientists picked up their radio waves. But Doug Duncan, director emeritus of the Fiske Planetarium in Boulder, says the discovery may be the most significant find in astronomy since gravitational waves. Scientists want to understand our universe and how it formed from the earliest time, and this puts us incredibly close to the very beginning - the Big Bang.

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When Stars Were Born: Earliest Starlight’s Effects Are Detected

Anonymous — Wed, 28 Feb 2018 15:54:24 +0000

When Stars Were Born: Earliest Starlight’s Effects Are Detected Anonymous (not verified) Wed, 02/28/2018 - 08:54

Dennis Overbye

From The New York Times: It was morning in the universe and much colder than anyone had expected when light from the first stars began to tickle and excite their dark surroundings nearly 14 billion years ago.

Astronomers using a small radio telescope in Australia reported on Wednesday that they had discerned effects of that first starlight on the universe when it was only 180 million years old. The observations take astronomers farther back into the mists of time than even the Hubble Space Telescope can see and raised new questions about how well astronomers really know the early days of the cosmos, and about the nature of the mysterious so-called dark matter whose gravity sculpts the luminous galaxies.

“We have seen indirectly evidence of very early stars in the universe — stars that would have formed by the time the universe was only 180 million years old,” said Judd Bowman of Arizona State, leader of the experiment known as EDGES, for Experiment to Detect Global EoR, in an email. Dr. Bowman and his colleagues published their results in Nature Wednesday. Read more...

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Astronomers detect light from the Universe’s first stars

Anonymous — Wed, 28 Feb 2018 15:50:23 +0000

Astronomers detect light from the Universe’s first stars Anonymous (not verified) Wed, 02/28/2018 - 08:50

Elizabeth Gibney

From Nature: Astronomers have for the first time spotted long-sought signals of light from the earliest stars ever to form in the Universe — around 180 million years after the Big Bang.

The signal is a fingerprint left on background radiation by hydrogen that absorbed some of this primordial light. The evidence hints that the gas that made up the early Universe was colder than predicted. This, physicists say, is a possible sign of dark matter’s influence. If confirmed, the discovery could mark the first time that dark matter has been detected through anything other than its gravitational effects.

“This is the first time we’ve seen any signal from this early in the Universe, aside from the afterglow of the Big Bang,” says Judd Bowman, an astronomer at Arizona State University in Tempe who led the work, which is published in Nature¹ on 28 February. “If it’s true, this is major news,” says Saleem Zaroubi, a cosmologist at the University of Groningen in the Netherlands. Other teams will need to confirm the signal but, so far, the finding seems to be robust, he says. “It’s very exciting stuff. This is a period in the Universe’s history we know very little about.” Read more...

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A surprising chill before the cosmic dawn

Anonymous — Wed, 28 Feb 2018 15:44:55 +0000

A surprising chill before the cosmic dawn Anonymous (not verified) Wed, 02/28/2018 - 08:44

Lincoln Greenhill

From Nature: The first stars to form generated copious fluxes of ultraviolet radiation that suffused the early Universe — a phenomenon referred to as the cosmic dawn. Many calculations have been performed to estimate when this occurred, but no data-driven constraints on the timing have been available. In a paper in Nature, Bowman et al. report what might be the first detection of the thermal footprints of these stars, tracking back to 180 million years after the Big Bang.

Less than one million years after the Big Bang, the Universe consisted of atomic gas (chiefly hydrogen) and a form of matter that outweighs regular matter by more than five times but has yet to be seen directly. Measurements over decades have indicated that, oddly enough, this ‘dark’ matter interacts with itself and with regular matter only through the action of gravity. It was mainly the gravity of dark matter that amplified small, localized density perturbations in the Universe shortly after the Big Bang to generate the first large-scale structures. But it was the hydrogen within these perturbations that collapsed piecemeal to form stars, bringing about the cosmic dawn.

The observable thermal footprints of early stars derive from small variations in the ratio of the number of interstellar hydrogen atoms found in two particular energy states; a transition between these states causes a photon to be emitted or absorbed at a characteristic radio frequency. The ratio reflects the degree of excitation of the hydrogen, and can be expressed as a temperature, known as the atomic spin temperature (T_S). Read more...

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Signal Detected from Cosmic Dawn

Anonymous — Wed, 28 Feb 2018 15:35:33 +0000

Signal Detected from Cosmic Dawn Anonymous (not verified) Wed, 02/28/2018 - 08:35

Jonathan Amos

From the BBC: Scientists say they have observed a signature on the sky from the very first stars to shine in the Universe. They did it with the aid of a small radio telescope in the Australian outback that was tuned to detect the earliest ever evidence for hydrogen. This hydrogen was in a state that could only be explained if it had been touched by the intense light of stars. The team puts the time of this interaction at a mere 180 million years after the Big Bang. Given that the cosmos is roughly 13.8 billion years old, it means the first stars lit up a full nine billion years before even our own Sun flickered into life.

Dr Judd Bowman of Arizona State University, US, is the lead author on the scholarly paper describing the observation in the journal Nature. He told BBC News that the discovery's great significance meant his group had to be absolutely sure no mistakes were made. "We first started seeing signs in our data back in late 2015. And we've really spent the last couple of years trying to think of all sorts of possible alternative explanations, and then rule them out one by one," he said. Read more...

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