From The Johns Hopkins University Via “Science Alert (AU)” : “An Unexpected Source Might Be Helping The Universe Glow More Than It Should” 

From The Johns Hopkins University



“Science Alert (AU)”

Michelle Starr

When the New Horizons probe reached the outer dark of the Solar System out past Pluto its instruments picked up something strange.

Very very faintly the space between the stars was glowing with optical light. This in itself was not unexpected; this light is called the cosmic optical background [COB], a faint luminescence from all the light sources in the Universe outside our galaxy [Nature Communications (below)].

Figure 1: The trajectory of New Horizons through the solar system.
Data collection periods of relevance to this study are indicated. Both the x−y and r−z planes are shown (a,b, respectively), with the axes in solar ecliptic units [see formula in Nature Communications paper below]. New Horizons was launched from Earth at 1 a.u., and the data with the LORRI dust cover in place were acquired at 1.9 a.u., just beyond Mars’ orbit at 1.5 a.u. (inner blue dotted lines). The dust cover was ejected near 3.6 a.u., and the data were acquired before and during an encounter with Jupiter. The data considered here were taken between 2007 and 2010 while New Horizons was in cruise phase. The red vectors indicate the relative positions of fields 1−4 compared to the sun and plane of the ecliptic.

Figure 2: Measurements of the COB surface brightness.
The [see formula in Nature Communications paper below] determined in this study are shown as both an upper limit (red) and a mean (red star). We also show previous results in the literature, including direct constraints on the COB (filled symbols) and the IGL (open symbols). The plotted LORRI errors are purely statistical and are calculated from the observed variance in the mean of individual 10 s exposures; see Fig. 3 for an assessment of the systematic uncertainties in the measurement. We include the measurements from HST-WFPC2 (ref. 7; green squares), combinations of DIRBE and 2MASS10,11,12,13 (diamonds; the wavelengths of these measurements have been shifted for clarity), a measurement using the ‘dark cloud’ method8 (grey circles), and previous Pioneer 10/11 measurements22,23 (blue upper limit leader and circles). The gold region indicates the H.E.S.S. constraints on the extragalactic background light29. We include the background inferred from CIBER5 (pentagons). The IGL points are compiled from HST-STIS in the ultraviolet (UV)62 (open square), and the Hubble Deep Field63 (downward open triangles) the Subaru Deep Field64,65 (upward open triangles and sideways pointing triangles) in the optical/near-IR. Where plotted, horizontal bars indicate the effective wavelength band of the measurement. Our new LORRI value from just 260 s of integration time is consistent with the previous Pioneer values.

The strange part was the amount of light. There was significantly more than scientists thought there should be – twice as much, in fact.

Now, in a new paper [PRL (below)], scientists lay out a possible explanation for the optical light excess: a by-product of an otherwise undetectable interaction of dark matter.

“The results of this work,” write a team of researchers led by astrophysicist José Luis Bernal of Johns Hopkins University, “provide a potential explanation for the cosmic optical background [COB] excess that is allowed by independent observational constraints, and that may answer one of the most long-standing unknowns in cosmology: the nature of dark matter.”

We have many questions about the Universe, but dark matter is among the most vexing. It’s the name we give to a mysterious mass in the Universe responsible for providing far more gravity in concentrated spots than there ought to be.

Galaxies rotate faster than they should under the gravity generated by the mass of visible matter.

The curvature of space-time around massive objects is greater than it should be if we calculated the warping of space based only on the amount of glowing material.

But whatever it is creating this effect, we can’t detect it directly. The only way we know it’s there is that we just can’t account for this extra gravity.

And there’s a lot of it. Roughly 80 percent of the matter in the Universe is dark matter.

Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., and Vera Rubin a Woman in STEM, denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky.
Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed 30 years later by Vera Rubin.

In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.
Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

Vera Rubin measuring spectra, worked on Dark Matter(Emilio Segre Visual Archives AIP SPL).

Dark Matter Research

Super Cryogenic Dark Matter Search from DOE’s SLAC National Accelerator Laboratory at Stanford University at SNOLAB (Vale Inco Mine, Sudbury, Canada).

LBNL LZ Dark Matter Experiment xenon detector at Sanford Underground Research Facility Credit: Matt Kapust.

DAMA at Gran Sasso uses sodium iodide housed in copper to hunt for dark matter LNGS-INFN.

Yale HAYSTAC axion dark matter experiment at Yale’s Wright Lab.

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB (CA) deep in Sudbury’s Creighton Mine.

The LBNL LZ Dark Matter Experiment Dark Matter project at SURF, Lead, SD.

DAMA-LIBRA Dark Matter experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) located in the Abruzzo region of central Italy.

DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at The University of Zurich [Universität Zürich](CH).

PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

Inside the Axion Dark Matter eXperiment U Washington Credit : Mark Stone U. of Washington. Axion Dark Matter Experiment.

The University of Western Australia ORGAN Experiment’s main detector. A small copper cylinder called a “resonant cavity” traps photons generated during dark matter conversion. The cylinder is bolted to a “dilution refrigerator” which cools the experiment to very low temperatures.

There are some hypotheses about what it might be. One of the candidates is the axion, which belongs to a hypothetical class of particles first conceptualized in the 1970s to resolve the question of why strong atomic forces follow something called charge-parity symmetry when most models say they don’t need to.

[See ADMX above]

As it turns out, axions in a specific mass range should also behave exactly like we expect dark matter to. And there might be a way to detect them – because theoretically, axions are expected to decay into pairs of photons in the presence of a strong magnetic field.

Several experiments are searching for sources of these photons, but they should also be streaming through space in excess numbers.

The difficulty is in separating them from all the other sources of light in the Universe, and this is where the cosmic optical background comes in.

The background is itself very difficult to detect since it’s so faint. The Long Range Reconnaissance Imager (LORRI) aboard the New Horizons is possibly the best tool for the job yet. It’s far from Earth and the Sun, and LORRI is far more sensitive than instruments attached to the more distant Voyager probes that launched 40 years earlier.

Scientists have presumed the excess detected by New Horizons to be the product attributed to stars and galaxies that we can’t see. And that option is still very much on the table. The work of Bernal and his team was to assess whether axion-like dark matter could possibly be responsible for the extra light.

They conducted mathematical modeling and determined that axions with masses between 8 and 20 electronvolts could produce the observed signal under certain conditions.

That’s incredibly light for a particle, which tends to be measured in megaelectronvolts. But with recent estimates putting the hypothetical piece of matter at a fraction of a single electronvolt, these numbers would demand axions to be relatively beefy.

It’s impossible to tell which explanation is correct based solely on the current data. However, by narrowing down the masses of the axions that could be responsible for the excess, the researchers have laid the foundations for future searches for these enigmatic particles.

“If the excess arises from dark-matter decay to a photon line, there will be a significant signal in forthcoming line-intensity mapping measurements,” the researchers write.

“Moreover, the ultraviolet instrument aboard New Horizons (which will have better sensitivity and probe a different range of the spectrum) and future studies of very high-energy gamma-ray attenuation will also test this hypothesis and expand the search for dark matter to a wider range of frequencies.”

The research has been published in Physical Review Letters.

Science paper:
Nature Communications 2017
See the science paper for instructive material with more images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct.


Please help promote STEM in your local schools.

Stem Education Coalition

Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

The Johns Hopkins University is a private research university in Baltimore, Maryland. Founded in 1876, the university was named for its first benefactor, the American entrepreneur and philanthropist Johns Hopkins. His $7 million bequest (approximately $147.5 million in today’s currency)—of which half financed the establishment of the Johns Hopkins Hospital—was the largest philanthropic gift in the history of the United States up to that time. Daniel Coit Gilman, who was inaugurated as the institution’s first president on February 22, 1876, led the university to revolutionize higher education in the U.S. by integrating teaching and research. Adopting the concept of a graduate school from Germany’s historic Ruprecht Karl University of Heidelberg, [Ruprecht-Karls-Universität Heidelberg] (DE), Johns Hopkins University is considered the first research university in the United States. Over the course of several decades, the university has led all U.S. universities in annual research and development expenditures. In fiscal year 2016, Johns Hopkins spent nearly $2.5 billion on research. The university has graduate campuses in Italy, China, and Washington, D.C., in addition to its main campus in Baltimore.

Johns Hopkins is organized into 10 divisions on campuses in Maryland and Washington, D.C., with international centers in Italy and China. The two undergraduate divisions, the Zanvyl Krieger School of Arts and Sciences and the Whiting School of Engineering, are located on the Homewood campus in Baltimore’s Charles Village neighborhood. The medical school, nursing school, and Bloomberg School of Public Health, and Johns Hopkins Children’s Center are located on the Medical Institutions campus in East Baltimore. The university also consists of the Peabody Institute, Applied Physics Laboratory, Paul H. Nitze School of Advanced International Studies, School of Education, Carey Business School, and various other facilities.

Johns Hopkins was a founding member of the American Association of Universities. As of October 2019, 39 Nobel laureates and 1 Fields Medalist have been affiliated with Johns Hopkins. Founded in 1883, the Blue Jays men’s lacrosse team has captured 44 national titles and plays in the Big Ten Conference as an affiliate member as of 2014.


The opportunity to participate in important research is one of the distinguishing characteristics of Hopkins’ undergraduate education. About 80 percent of undergraduates perform independent research, often alongside top researchers. In FY 2013, Johns Hopkins received $2.2 billion in federal research grants—more than any other U.S. university for the 35th consecutive year. Johns Hopkins has had seventy-seven members of the Institute of Medicine, forty-three Howard Hughes Medical Institute Investigators, seventeen members of the National Academy of Engineering, and sixty-two members of the National Academy of Sciences. As of October 2019, 39 Nobel Prize winners have been affiliated with the university as alumni, faculty members or researchers, with the most recent winners being Gregg Semenza and William G. Kaelin.

Between 1999 and 2009, The Johns Hopkins University was among the most cited institutions in the world. It attracted nearly 1,222,166 citations and produced 54,022 papers under its name, ranking No. 3 globally [after Harvard University and the Max Planck Society (DE)] in the number of total citations published in Thomson Reuters-indexed journals over 22 fields in America.

In FY 2000, Johns Hopkins received $95.4 million in research grants from the National Aeronautics and Space Administration, making it the leading recipient of NASA research and development funding. In FY 2002, Hopkins became the first university to cross the $1 billion threshold on either list, recording $1.14 billion in total research and $1.023 billion in federally sponsored research. In FY 2008, Johns Hopkins University performed $1.68 billion in science, medical and engineering research, making it the leading U.S. academic institution in total R&D spending for the 30th year in a row, according to a National Science Foundation ranking. These totals include grants and expenditures of JHU’s Applied Physics Laboratory in Laurel, Maryland.

The Johns Hopkins University also offers the “Center for Talented Youth” program—a nonprofit organization dedicated to identifying and developing the talents of the most promising K-12 grade students worldwide. As part of the Johns Hopkins University, the “Center for Talented Youth” or CTY helps fulfill the university’s mission of preparing students to make significant future contributions to the world. The Johns Hopkins Digital Media Center (DMC) is a multimedia lab space as well as an equipment, technology and knowledge resource for students interested in exploring creative uses of emerging media and use of technology.

In 2013, the Bloomberg Distinguished Professorships program was established by a $250 million gift from Michael Bloomberg. This program enables the university to recruit fifty researchers from around the world to joint appointments throughout the nine divisions and research centers. For The American Academy of Arts and Sciences each professor must be a leader in interdisciplinary research and be active in undergraduate education. Directed by Vice Provost for Research Denis Wirtz, there are currently thirty-two Bloomberg Distinguished Professors at the university, including three Nobel Laureates, eight fellows of the American Association for the Advancement of Science, ten members of the American Academy of Arts and Sciences, and thirteen members of the National Academies.