Early Universe

The quest to unlock the secrets of the baby Universe

Anonymous — Wed, 14 Aug 2019 21:03:41 +0000

The quest to unlock the secrets of the baby Universe Anonymous (not verified) Wed, 08/14/2019 - 15:03

Davide Castelvecchi

From Nature: The quest to unlock the secrets of the baby Universe

To get an idea of what the Universe looks like from Earth’s perspective, picture a big watermelon. Our Galaxy, the Milky Way, is one of the seeds, at the centre of the fruit. The space around it, the pink flesh, is sprinkled with countless other seeds. Those are also galaxies that we — living inside that central seed — can observe through our telescopes.

Because light travels at a finite speed, we see other galaxies as they were in the past. The seeds farthest from the centre of the watermelon are the earliest galaxies seen so far, dating back to a time when the Universe was just one-thirtieth of its current age of 13.8 billion years. Beyond those, at the thin, green outer layer of the watermelon skin, lies something primeval from before the time of stars. This layer represents the Universe when it was a mere 380,000 years old, and still a warm, glowing soup of subatomic particles. We know about that period because its light still ripples through space — although it has stretched so much over the eons that it now exists as a faint glow of microwave radiation.

The most mysterious part of the observable Universe is another layer of the watermelon, the section between the green shell and the pink flesh. This represents the first billion years of the Universe’s history. Astronomers have seen very little of this period, except for a few, exceedingly bright galaxies and other objects. Read more...

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Astronomers Use Radio Waves to Look Back at First Stars in the Universe

Anonymous — Fri, 02 Mar 2018 19:50:17 +0000

Astronomers Use Radio Waves to Look Back at First Stars in the Universe Anonymous (not verified) Fri, 03/02/2018 - 12:50

Annika Cline

From KJZZ 91.5 Radio: The story of the universe as we know it and the planet we live on begins with the first star. In 2016, the Hubble Telescope measured the oldest known galaxy in the universe — one that formed 400 million years after the Big Bang.

A group of astronomers has sliced that record in half with new findings that suggest the oldest stars formed 180 million years after the Big Bang. The study is a collaboration between ASU and MIT and was published this week in the journal Nature.

Dr. Judd Bowman is an astrophysicist at ASU who co-authored the study. And he sort of knows how to travel back in time. “Every telescope is a time machine, so the farther away we look, the farther back in time we see,” Bowman said.

It’s not like a TARDIS or a flying DeLorean, but Bowman works with technology that picks up traces of the distant past — signals in the sky leftover from the universe’s earliest moments. Think about it as the first stars sending a letter to a pen pal that didn’t exist yet. But the letter isn’t so easy to read. Read more and listen to the audio...

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An Absorption Profile Centered at 78 megahertz in the Sky-averaged Spectrum

Anonymous — Thu, 01 Mar 2018 15:32:43 +0000

An Absorption Profile Centered at 78 megahertz in the Sky-averaged Spectrum Anonymous (not verified) Thu, 03/01/2018 - 08:32

Judd D. Bowman Alan E. E. Rogers Raul A. Monsalve Thomas J. Mozdzen & Nivedita Mahesh

From Nature: After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later. Read more...

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Did Dark Matter Make The Early Universe Chill Out?

Anonymous — Wed, 28 Feb 2018 15:58:22 +0000

Did Dark Matter Make The Early Universe Chill Out? Anonymous (not verified) Wed, 02/28/2018 - 08:58

Nell Greenfieldboyce

From NPR: Scientists have probed a period of the universe's early history that no one has been able to explore before — and they got a surprise: It was far colder in the young universe, before the first stars blinked on, than astronomers previously thought.

What's more, that cosmic chill may have come from previously unknown interactions between normal matter and mysterious, so-called dark matter, according to two new reports in the journal Nature.

If so, it's the first time scientists have observed any effect of dark matter other than its gravitational pull.

All of this comes from an experiment that detected a faint radio signal from primordial hydrogen gas in the young universe, just 180 million years after the Big Bang. Read more...

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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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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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Astronomers detect ancient signal from first stars in universe

Anonymous — Wed, 28 Feb 2018 15:17:31 +0000

Astronomers detect ancient signal from first stars in universe Anonymous (not verified) Wed, 02/28/2018 - 08:17

From ��ſ��2023��¼ Today: For the first time, astronomers have detected a signal from stars emerging in the early universe. Using a radio antenna not much larger than a refrigerator, the researchers discovered that ancient suns were active within 180 million years of the Big Bang.

The astronomers, from Arizona State University (ASU), the Massachusetts Institute of Technology (MIT) and the University of Colorado Boulder, made the discovery with their Experiment to Detect the Global EoR (Epoch of Reionization) Signature (EDGES) project, funded by the National Science Foundation (NSF). They reported their findings in the March 1 issue of Nature.

"The EDGES experiment measures the tiny perturbation in the radio spectrum due to the appearance of the first stars and galaxies in the Universe,” said Raul Monsalve, a postdoctoral researcher at ��ſ��2023��¼’s Network for Exploration and Space Science (NESS) and a co-author of the new study. “We have detected an absorption feature consistent with the formation of the first generations of stars 180 million years after the big bang." Read more...

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