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  • richardmitnick 3:21 pm on January 5, 2017 Permalink | Reply
    Tags: , , , , , , ESA/Planck,   

    From USRA: “Arecibo Observatory casts new light on cosmic microwave background observed by WMAP and PLANCK spacecraft” 

    usra-bloc

    USRA

    January 4, 2017
    PR Contact: Suraiya Farukhi
    sfarukhi@usra.edu
    Universities Space Research Association
    410-740-6224 (o)
    443-812-6945 (c)

    Technical Contact: Joan Schmelz
    jschmelz@usra.edu
    Universities Space Research Association
    787-878-2612 x603

    NAIC/Arecibo Observatory, Puerto Rico, USA
    NAIC/Arecibo Observatory, Puerto Rico, USA

    Arecibo Observatory observations of galactic neutral hydrogen structure confirm the discovery of an unexpected contribution to the measurements of the cosmic microwave background observed by the WMAP and Planck spacecraft.

    NASA WMAP satellite
    NASA WMAP satellite

    ESA/Planck
    “ESA/Planck

    An accurate understanding of the foreground (galactic) sources of radiation observed by these two spacecraft is essential for extracting information about the small-scale structure in the cosmic microwave background believed to be indicative of events in the early universe.

    Cosmic Microwave Background WMAP
    Cosmic Microwave Background WMAP

    CMB per ESA/Planck
    CMB per ESA/Planck

    The new source of radiation in the 22 to 100 GHz range observed by WMAP and Planck appears to be emission from cold electrons (known as free-free emission). While cosmologists have corrected for this type of radiation from hot electrons associated with galactic nebulae where the source temperatures are thousands of degrees, the new model requires electron temperatures more like a few 100 K.

    The spectrum of the small-scale features observed by WMAP and Planck in this frequency range is very nearly flat — a finding consistent with the sources being associated with the Big Bang. At first glance it appears that the spectrum expected from the emission by cold galactic electrons, which exist throughout interstellar space, would be far too steep to fit the data. However, if the sources of emission have a small angular size compared with the beam width used in the WMAP and Planck spacecraft, the signals they record would be diluted. The beam widths increase with lower frequency, and the net result of this “beam dilution” is to produce an apparently flat spectrum in the 22 to 100 GHz range.

    “It was the beam dilution that was the key insight,” noted Dr. Gerrit Verschuur, astronomer emeritus at the Arecibo Observatory and lead author on the paper. “Emission from an unresolved source could mimic the flat spectrum observed by WMAP and Planck.”

    The model invoking the emission from cold electrons not only gives the observed flat spectrum usually attributed to cosmic sources but also predicts values for the angular scale and temperature for the emitting volumes. Those predictions can then be compared with observations of galactic structure revealed in the Galactic Arecibo L-Band Feed Array (GALFA) HI survey.

    “The interstellar medium is much more surprising and important than we have given it credit for,” noted Dr. Joshua Peek, an astronomer at the Space Telescope Science Institute and a co-investigator on the GALFA-HI survey. “Arecibo, with its combination of large area and high resolution, remains a spectacular and cutting edge tool for comparing ISM maps to cosmological data sets.”

    The angular scales of the smallest features observed in neutral hydrogen maps made at Arecibo and the temperature of the apparently associated gas both match the model calculations extremely well. So far only three well-studied areas have been analyzed in such detail, but more work is being planned.

    “It was the agreement between the model predictions and the GALFA-HI observations that convinced me that we might be onto something,” noted Dr. Joan Schmelz, Director, Universities Space Research Association (USRA) at Arecibo Observatory and a coauthor on the paper. “We hope that these results help us understand the true cosmological nature of Planck and WMAP data.”

    The data suggest that the structure and physics of diffuse interstellar matter, in particular of cold hydrogen gas and associated electrons, may be more complex than heretofore considered. Such complexities need to be taken into account in order to produce better foreground masks for application to the high-frequency continuum observations of Planck and WMAP in the quest for a cosmologically significant signal.

    USRA’s Dr. Joan Schmelz will present these findings on January 4, 2017, at a press conference at the American Astronomical Society’s (AAS) meeting at Grapevine, Texas.

    The results were published in the Astrophysical Journal, December 1, 2016, in a paper entitled On the Nature of Small-Scale Structure in the Cosmic Microwave Background Observed by Planck and WMAP by G. L. Verschuur and J. T. Schmelz.

    See the full article here .

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    USRA is an independent, nonprofit research corporation where the combined efforts of in-house talent and university-based expertise merge to advance space science and technology.

    SIGNIFICANCE & PURPOSE

    USRA was founded in 1969, near the beginning of the Space Age, driven by the vision of two individuals, James Webb (NASA Administrator 1961-1968) and Frederick Seitz (National Academy of Sciences President 1962-1969). They recognized that the technical challenges of space would require an established research base to develop novel concepts and innovative technologies. Together, they worked to create USRA to satisfy not only the ongoing need for innovation in space, but also the need to involve society more broadly so the benefits of space activities would be realized.

     
  • richardmitnick 8:38 am on December 29, 2016 Permalink | Reply
    Tags: , , , , DDM hypothesis, , ESA/Planck, , Institute for Nuclear Research in Moscow, , The Universe is losing dark matter and researchers have finally measured how much   

    From Science Alert: “The Universe is losing dark matter, and researchers have finally measured how much” 

    ScienceAlert

    Science Alert

    28 DEC 2016
    JOSH HRALA

    1
    MIPT

    Researchers from Russia have, for the first time, been able to measure the amount of dark matter the Universe has lost since the Big Bang some 13.7 billion years ago, and calculate that as much as 5 percent of dark matter could have deteriorated.

    The finding could explain one of the biggest mysteries in physics – why our Universe appears to function in a slightly different way than it did in the years just after the Big Bang, and it could also shed insight into how it might continue to evolve in future.

    “The discrepancy between the cosmological parameters in the modern Universe and the Universe shortly after the Big Bang can be explained by the fact that the proportion of dark matter has decreased,” said co-author Igor Tkachev, from the Institute for Nuclear Research in Moscow.

    “We have now, for the first time, been able to calculate how much dark matter could have been lost, and what the corresponding size of the unstable component would be.”

    The mystery surrounding dark matter was first brought up way back in the 1930s, when astrophysicists and astronomers observed that galaxies moved in weird ways, appearing to be under the effect of way more gravity than could be explained by the visible matter and energy in the Universe.

    This gravitational pull has to come from somewhere. So, researchers came up with a new type of ‘dark matter’ to describe the invisible mass responsible for the things they were witnessing.

    As of right now, the current hypothesis states that the Universe is made up of 4.9 percent normal matter – the stuff we can see, such as galaxies and stars – 26.8 percent dark matter, and 68.3 percent dark energy, a hypothetical type of energy that’s spread throughout the Universe, and which might be responsible for the Universe’s expansion.

    But even though the majority of matter predicted to be in the Universe is actually dark, very little is known about dark matter – in fact, scientists still haven’t been able to prove that it actually exists.

    One of the ways scientists study dark matter is by examining the cosmic microwave background (CMB), which some call the ‘echo of the Big Bang’.

    CMB per ESA/Planck
    CMB per ESA/Planck

    The CMB is the thermal radiation left over from the Big Bang, making it somewhat of an astronomical time capsule that researchers can use to understand the early, newly born Universe.

    The problem is that the cosmological parameters that govern how our Universe works – such as the speed of light and the way gravity works – appear to differ ever so slightly in the CMB compared to the parameters we know to exist in the modern Universe.

    “This variance was significantly more than margins of error and systematic errors known to us,” Tkachev explains. “Therefore, we are either dealing with some kind of unknown error, or the composition of the ancient universe is considerably different to the modern Universe.”

    One of the hypotheses that might explain why the early Universe was so different is the ‘decaying dark matter‘ [Nature] (DDM) hypothesis – the idea that dark matter has slowly been disappearing from the Universe.

    And that’s exactly what Tkachev and his colleagues set out to analyse on a mathematical level, looking for just how much dark matter might have decayed since the creation of the Universe.

    The study’s lead author, Dmitry Gorbunov, also from the Institute for Nuclear Research, explains:

    “Let us imagine that dark matter consists of several components, as in ordinary matter (protons, electrons, neutrons, neutrinos, photons). And one component consists of unstable particles with a rather long lifespan.

    In the era of the formation of hydrogen, hundreds of thousands of years after the Big Bang, they are still in the Universe, but by now (billions of years later), they have disappeared, having decayed into neutrinos or hypothetical relativistic particles. In that case, the amount of dark matter in the era of hydrogen formation and today will be different.”

    To come up with a figure, the team analysed data taken from the Planck Telescope observations on the CMB, and compared it to different dark matter models like DDM.

    ESA/Planck
    ESA/Planck

    They found that the DDM model accurately depicts the observational data found in the modern Universe over other possible explanations for why our Universe looks so different today compared to straight after the Big Bang.

    The team was able to take the study a step further by comparing the CMB data to the modern observational studies of the Universe and error-correcting for various cosmological effects – such as gravitational lensing, which can amplify regions of space thanks to the way gravity can bend light.

    In the end, they suggest that the Universe has lost somewhere between 2 and 5 percent of its dark matter since the Big Bang, as a result of these hypothetical dark matter particles decaying over time.

    “This means that in today’s Universe, there is 5 percent less dark matter than in the recombination era,” Tkachev concludes.

    “We are not currently able to say how quickly this unstable part decayed; dark matter may still be disintegrating even now, although that would be a different and considerably more complex model.”

    These findings suggest that dark matter decays over time, making the Universe move in different ways than it had in the past, though the findings call for more outside research before anything is said for certain.

    Even so, this research is another step closer to potentially understanding the nature of dark matter, and solving one of science’s greatest mysteries – why the Universe looks the way it does, and how it will evolve in the future.

    The team’s work was published in Physical Review D.

    See the full article here .

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  • richardmitnick 12:39 pm on August 8, 2016 Permalink | Reply
    Tags: , , , , ESA/Planck,   

    From Astronomy: “When did the lights turn on in the universe?” 

    Astronomy magazine

    Astronomy.com

    August 08, 2016
    Nola Taylor Redd

    1
    A map showing the history of the universe, including the shift from neutral to ionized hydrogen resulting in the universe we see today.
    NAOJ

    The early universe hides behind the cloak of its Dark Ages, a period of time light can’t seem to pierce. Even the length of those unseen years remains uncertain. As part of its efforts to probe the secrets of those hidden years, the European Space Agency’s Planck Satellite recently announced the most precise constraints on the universe’s evasive era, for the first time revealing that the first stars and their galaxies are enough to light up the darkness.

    ESA/Planck
    ESA/Planck

    Trying to pierce the veil of darkness has been a decades-long struggle to look back in time nearly 14 billion years. After the Big Bang, the hot universe quickly cooled down, and the simplest atomic particles formed. The protons and electrons of the early universe constantly collided, creating a hot soup that kept light from passing. The Dark Ages had begun.

    As the gas cooled down, and the expanding galaxy stretched space-time, the particles recombined to form neutral hydrogen. Like the rising dawn, the universe grew gradually more transparent, its gradual glow imprinted on the radio noise scientists recognize as the Cosmic Microwave Background (CMB). The universe remained dark, however, because nothing produced visible light.

    Cosmic Microwave Background per ESA/Planck
    Cosmic Microwave Background per ESA/Planck

    Gravity worked hard to change that. It didn’t take long for the force to begin pulling material together, forming the first stars and galaxies. Bright galaxies know as quasars, whose central supermassive black holes produce powerful jets of light and matter, also populated the early universe. Heat from the young objects broke the neutral hydrogen apart over time in the process known as reionization, with slow-sweeping bubbles of light spreading outward from the bright objects. As the bubbles grew and overlapped, the universe once again became visible, and the Dark Age ended. (The change of state in hydrogen that allowed a visible universe is called the Epoch of Reionization.)

    Perhaps one of the most challenging attributes of the Dark Age is the difficulty inherent in nailing down just when it ended and how long it lasted. Because light didn’t shine from the start of the Dark Age, scientists must rely on the glow from the CMB to provide them with clues to when recombination brought particles together to make the universe gradually more transparent. Observations of early galaxies and quasars, the brightest objects in the universe, help narrow down how long the lights were off.

    Planck’s most recent results suggest that the time of reionization, when light from the first objects began to break apart molecules once again, occurred about 55 million years later than previous studies placed it.

    “It is certainly clear that we are now measuring a later onset of reionization,” says Planck Project Scientist Jan Tauber said by email.

    Planck Scientist Graca Rocha, of the Jet Propulsion Laboratory, stresses that Planck’s measurements have become more precise over time. Rocha, who presented a portion of the research at the American Astronomical Society meeting in San Diego, California in June, pointed to the error bar in the calculations, a number that has grown smaller over time. The most recent results have an error of less than nine-thousandanths.

    “We are narrowing the range of reionization, when the first stars start to form,” Rocha told Astronomy. “People are thrilled about the shift down.”

    Strange objects begone

    The first early estimates suggested that reionization wrapped up extremely fast, requiring unusual astronomical bodies to clear the darkness. Tension mounted as the scientists sought to reconcile multiple forms of observation. Planck’s new numbers helped to relieve some of the pressure as the more precise calculations suggested that novel things were unnecessary after all.

    “Those early measurements required ‘strange objects’ to reionize the universe, but those concerns have now been dissipated by Planck,” Tauber says.

    “We now know that the first galaxies that we can already observe are enough to reionize the universe at the time shown by the [Cosmic Microwave Background].”

    Since its launch in 2009, Planck has probed the early universe, seeking to learn more about when the Dark Ages started and ended. Over three quarters of a decade, the spacecraft has helped to improve the understanding of the unseen era by penetrating the veil of darkness around it.

    The more sophisticated analysis reveals that the first objects didn’t begin to separate the fog of particles until “quite late,” Tauber says. Planck reveals that the universe was no more than 10 percent ionized by the time the universe was 475 million years old. It also demonstrated that the process wrapped up quickly, within about 250 million years.

    “This model is very consistent with observations of the earliest galaxies,” Tauber says.

    These galaxies allow scientists to estimate the total amount of light available to the early universe to split the particles once again.

    “So the Planck- and CMB-based estimates are now in full agreement with direct observations.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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