Link Between Primordial Black Holes and Dark Matter

Scientist suggests possible link between primordial black holes and dark matter

Left: This image from NASA’s Spitzer Space Telescope shows an infrared view of a sky area in the constellation Ursa Major. Right: After masking out all known stars, galaxies and artifacts and enhancing what’s left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors indicate brighter areas. The CIB glow is more irregular than can be explained by distant unresolved galaxies, and this excess structure is thought to be light emitted when the universe was less than a billion years old. Scientists say it likely originated from the first luminous objects to form in the universe, which includes both the first stars and black holes. Credit: NASA/JPL-Caltech/A. Kashlinsky (Goddard)

Scientia — Dark matter is a mysterious substance composing most of the material universe, now widely thought to be some form of massive exotic particle. An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe’s existence, known as primordial black holes. Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year.

“This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good,” said Alexander Kashlinsky, an astrophysicist at NASA Goddard. “If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun’s mass.”

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In 2005, Kashlinsky led a team of astronomers using NASA’s Spitzer Space Telescope to explore the background glow of infrared light in one part of the sky. The researchers reported excessive patchiness in the glow and concluded it was likely caused by the aggregate light of the first sources to illuminate the universe more than 13 billion years ago. Follow-up studies confirmed that this cosmic infrared background (CIB) showed similar unexpected structure in other parts of the sky.

In 2013, another study compared how the cosmic X-ray background (CXB) detected by NASA’s Chandra X-ray Observatory compared to the CIB in the same area of the sky. The first stars emitted mainly optical and ultraviolet light, which today is stretched into the infrared by the expansion of space, so they should not contribute significantly to the CXB.

Yet the irregular glow of low-energy X-rays in the CXB matched the patchiness of the CIB quite well. The only object we know of that can be sufficiently luminous across this wide an energy range is a black hole. The research team concluded that primordial black holes must have been abundant among the earliest stars, making up at least about one out of every five of the sources contributing to the CIB.

The nature of dark matter remains one of the most important unresolved issues in astrophysics. Scientists currently favor theoretical models that explain dark matter as an exotic massive particle, but so far searches have failed to turn up evidence these hypothetical particles actually exist. NASA is currently investigating this issue as part of its Alpha Magnetic Spectrometer and Fermi Gamma-ray Space Telescope missions.

“These studies are providing increasingly sensitive results, slowly shrinking the box of parameters where dark matter particles can hide,” Kashlinsky said. “The failure to find them has led to renewed interest in studying how well primordial black holes—black holes formed in the universe’s first fraction of a second—could work as dark matter.”

Physicists have outlined several ways in which the hot, rapidly expanding universe could produce primordial black holes in the first thousandths of a second after the Big Bang. The older the universe is when these mechanisms take hold, the larger the black holes can be. And because the window for creating them lasts only a tiny fraction of the first second, scientists expect primordial black holes would exhibit a narrow range of masses.

Primordial black holes, if they exist, could be similar to the merging black holes detected by the LIGO team in 2014. This computer simulation shows in slow motion what this merger would have looked like up close. The ring around the black holes, called an Einstein ring, arises from all the stars in a small region directly behind the holes whose light is distorted by gravitational lensing. The gravitational waves detected by LIGO are not shown in this video, although their effects can be seen in the Einstein ring. Gravitational waves traveling out behind the black holes disturb stellar images comprising the Einstein ring, causing them to slosh around in the ring even long after the merger is complete. Gravitational waves traveling in other directions cause weaker, shorter-lived sloshing everywhere outside the Einstein ring. If played back in real time, the movie would last about a third of a second. Credit: SXS Lensing

On Sept. 14, gravitational waves produced by a pair of merging black holes 1.3 billion light-years away were captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves as well as the first direct detection of black holes. The signal provided LIGO scientists with information about the masses of the individual black holes, which were 29 and 36 times the sun’s mass, plus or minus about four solar masses. These values were both unexpectedly large and surprisingly similar.

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“Depending on the mechanism at work, primordial black holes could have properties very similar to what LIGO detected,” Kashlinsky explained. “If we assume this is the case, that LIGO caught a merger of black holes formed in the early universe, we can look at the consequences this has on our understanding of how the cosmos ultimately evolved.”

In his new paper, published May 24 in The Astrophysical Journal Letters, Kashlinsky analyzes what might have happened if dark matter consisted of a population of black holes similar to those detected by LIGO. The black holes distort the distribution of mass in the early universe, adding a small fluctuation that has consequences hundreds of millions of years later, when the first stars begin to form.

For much of the universe’s first 500 million years, normal matter remained too hot to coalesce into the first stars. Dark matter was unaffected by the high temperature because, whatever its nature, it primarily interacts through gravity. Aggregating by mutual attraction, dark matter first collapsed into clumps called minihaloes, which provided a gravitational seed enabling normal matter to accumulate. Hot gas collapsed toward the minihaloes, resulting in pockets of gas dense enough to further collapse on their own into the first stars. Kashlinsky shows that if black holes play the part of dark matter, this process occurs more rapidly and easily produces the lumpiness of the CIB detected in Spitzer data even if only a small fraction of minihaloes manage to produce stars.

As cosmic gas fell into the minihaloes, their constituent black holes would naturally capture some of it too. Matter falling toward a black hole heats up and ultimately produces X-rays. Together, infrared light from the first stars and X-rays from gas falling into dark matter black holes can account for the observed agreement between the patchiness of the CIB and the CXB.

Occasionally, some primordial black holes will pass close enough to be gravitationally captured into binary systems. The black holes in each of these binaries will, over eons, emit gravitational radiation, lose orbital energy and spiral inward, ultimately merging into a larger black hole like the event LIGO observed.

“Future LIGO observing runs will tell us much more about the universe’s population of black holes, and it won’t be long before we’ll know if the scenario I outline is either supported or ruled out,” Kashlinsky said.

Kashlinsky leads science team centered at Goddard that is participating in the European Space Agency’s Euclid mission, which is currently scheduled to launch in 2020. The project, named LIBRAE, will enable the observatory to probe source populations in the CIB with high precision and determine what portion was produced by black holes.

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– Credit and Resource –

More information: A. Kashlinsky. LIGO GRAVITATIONAL WAVE DETECTION, PRIMORDIAL BLACK HOLES, AND THE NEAR-IR COSMIC INFRARED BACKGROUND ANISOTROPIES, The Astrophysical Journal (2016). DOI: 10.3847/2041-8205/823/2/L25 , On Arxiv: arxiv.org/abs/1605.04023

Journal reference: Astrophysical Journal Letters, Astrophysical Journal, arXiv

Provided by: NASA

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Link Between Primordial Black Holes and Dark Matter

Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary

NASA’s Juno Spacecraft Crosses Jupiter/Sun Gravitational Boundary

Scientia — Since its launch five years ago, there have been three forces tugging at NASA’s Juno spacecraft as it speeds through the solar system. The sun, Earth and Jupiter have all been influential — a gravitational trifecta of sorts. At times, Earth was close enough to be the frontrunner. More recently, the sun has had the most clout when it comes to Juno’s trajectory. Today, it can be reported that Jupiter is now in the gravitational driver’s seat, and the basketball court-sized spacecraft is not looking back.

This artist’s rendering shows NASA’s Juno spacecraft making one of its close passes over Jupiter.
Credits: NASA/JPL-Caltech

“Today the gravitational influence of Jupiter is neck and neck with that of the sun,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “As of tomorrow, and for the rest of the mission, we project Jupiter’s gravity will dominate as the trajectory-perturbing effects by other celestial bodies are reduced to insignificant roles.”

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Juno was launched on Aug. 5, 2011. On July 4 of this year, it will perform a Jupiter orbit insertion maneuver — a 35-minute burn of its main engine, which will impart a mean change in velocity of 1,212 mph (542 meters per second) on the spacecraft. Once in orbit, the spacecraft will circle the Jovian world 37 times, skimming to within 3,100 miles (5,000 kilometers) above the planet’s cloud tops. During the flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

Juno’s name comes from Greek and Roman mythology. The mythical god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife — the goddess Juno — was able to peer through the clouds and reveal Jupiter’s true nature.

NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena manages JPL for NASA.

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– Credit and Resource –

NASA

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Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary

What is Dark Matter and Dark Energy?

Dark Energy and Dark Matter

In the early 1990s, one thing was fairly certain about the expansion of the Universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. The Universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the Universe was actually expanding more slowly than it is today. So the expansion of the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it.

Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein’s theory of gravity, one that contained what was called a “cosmological constant.” Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein’s theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don’t know what the correct explanation is, but they have given the solution a name. It is called dark energy.

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What Is Dark Energy?

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe’s expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%. The rest – everything on Earth, everything ever observed with all of our instruments, all normal matter – adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn’t be called “normal” matter at all, since it is such a small fraction of the Universe.

This diagram reveals changes in the rate of expansion since the universe’s birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart.
NASA/STSci/Ann Feild

One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein’s gravity theory, the version that contains a cosmological constant, makes a second prediction: “empty space” can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe.

Another explanation for how space acquires energy comes from the quantum theory of matter. In this theory, “empty space” is actually full of temporary (“virtual”) particles that continually form and then disappear. But when physicists tried to calculate how much energy this would give empty space, the answer came out wrong – wrong by a lot. The number came out 10120 times too big. That’s a 1 with 120 zeros after it. It’s hard to get an answer that bad. So the mystery continues.

Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field, something that fills all of space but something whose effect on the expansion of the Universe is the opposite of that of matter and normal energy. Some theorists have named this “quintessence,” after the fifth element of the Greek philosophers. But, if quintessence is the answer, we still don’t know what it is like, what it interacts with, or why it exists. So the mystery continues.

A last possibility is that Einstein’s theory of gravity is not correct. That would not only affect the expansion of the Universe, but it would also affect the way that normal matter in galaxies and clusters of galaxies behaved. This fact would provide a way to decide if the solution to the dark energy problem is a new gravity theory or not: we could observe how galaxies come together in clusters. But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein’s theory is known to do, and still give us the different prediction for the Universe that we need? There are candidate theories, but none are compelling. So the mystery continues.

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The thing that is needed to decide between dark energy possibilities – a property of space, a new dynamic fluid, or a new theory of gravity – is more data, better data.

What is Dark Matter?

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

One of the most complicated and dramatic collisions between galaxy clusters ever seen is captured in this new composite image of Abell 2744. The blue shows a map of the total mass concentration (mostly dark matter).

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or “MACHOs”. But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles)

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What is Dark Matter and Dark Energy?

New Green Propellants Complete Milestones

Scientia — To stay in the proper orbit, many satellites have thrusters–small rocket engines–that fire to change altitude or orientation in space. On Earth where gravity dominates, 5 pounds of thrust, equivalent to 22 Newtons of force, may seem small, but in space, it doesn’t take much thrust to move a large spacecraft.

Currently, most satellite thrusters are powered by hydrazine, a toxic and corrosive fuel that is dangerous to handle and store. In a quest to replace hydrazine with a more environmentally friendly fuel, NASA is testing thrusters propelled by green propellants that can provide better performance than hydrazine without the toxicity. These propellants could help lower costs by eliminating infrastructure needed for handling toxic fuels and reducing processing time–making it less expensive and safer and easier to launch both commercial and NASA spacecraft.

This image reveals a temperature profile of a 22 Newton thruster using the green propellant LMP-103S during a 10-second pulsing test that ratchets the temperature upward. Using this data, engineers can determine how chemical reactions cause heat to flow around to the thruster over time.
Credits: NASA/MSFC/Christopher Burnside

“When you consider all of the satellites in orbit today that do everything from observing Earth and monitoring weather to peering deep into our universe to answer questions about its origins, it’s easy to see that using green propellants will make a big difference in increased mission performance at a reduced cost while keeping both the environment and our workforce safe from contamination,” said Steve Jurczyk, NASA’s associate administrator for the Space Technology Mission Directorate (STMD) at NASA Headquarters in Washington. “NASA has a rich history of ensuring our technology and scientific prowess has a benefit to life on Earth, and green propellant will help ensure that NASA continues to be a steward of this planet.”

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NASA recently completed several hot-fire tests with thrusters powered by two different green propellants with the potential to replace hydrazine. Both are ionic liquid-based blends that are less toxic and less flammable than hydrazine, which makes them easier and less costly to store, to handle and to fuel up spacecraft before launch. Additionally, the new propellants offer higher performance, delivering more thrust for a given quantity of propellant than hydrazine.

NASA engineers monitor temperature data on the left computer screen as a thruster fueled with the green propellant LMP-103S viewed on the right computer screen is fired at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

One of the green propellants is a hydroxylammonium nitrate-based propellant known as AF-M315E. It was developed by the Air Force Research Laboratory at Edwards Air Force Base in California. This propellant will be demonstrated on a small satellite on NASA’s Green Propellant Infusion Mission (GPIM). During the GPIM flight, the smallsat will fire thrusters powered by AF-M315E to conduct maneuvers to change the satellite’s altitude and orientation. GPIM recently passed a major milestone with the delivery of the propellant’s propulsion subsystem built by Aerojet Rocketdyne in Redmond, Washington, to the mission’s prime contractor, Ball Aerospace & Technologies Corp. in Boulder, Colorado, for integration into the spacecraft. For this project, the GPIM team tested two different sized thrusters (1 and 22 Newton) with AF-M315E. Five of the 1-Newton thrusters will fly on GPIM.

“With GPIM’s flight scheduled to launch next year, NASA and the aerospace industry have taken positive steps to demonstrate use of a propellant that will reduce satellite fueling hazards and save time and money during launch campaigns,” said Tim Smith, GPIM mission manager for NASA’s Technology Demonstration Missions at Marshall. GPIM is managed by STMD’s Technology Demonstration Missions Program Office at Marshall.

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The other green propellant is a fuel called LMP-103S, which is based on the oxidizer ammonium dinitramide produced by Eurenco Bofors in Karlskoga, Sweden. A team at NASA’s Marshall Space Flight Center in Huntsville, Alabama, recently completed tests with both 5 Newton and 22 Newton thruster built by ECAPS and powered by LMP-103S. Engineers fired the 22 Newton thruster 35 times under varying conditions and monitored results with infrared cameras. Orbital ATK, Inc. assisted NASA with these tests.

Large and small thrusters are used to propel satellites in space. NASA engineers conducted the first tests with a 22 Newton (5-pound) thruster fueled with the green propellant LMP-103S. Engineer Chris Burnside examines a smaller 5 Newton (1-pound) thruster that also was tested at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

“We conducted the first NASA tests with 22 Newton thrusters with this propellant in the United States,” said Christopher Burnside, lead engineer for testing the LMP-103S propellant. “They performed quite well, providing performance at comparable levels to today’s hydrazine thrusters. It’s always great to put thrusters through the paces in an environment that simulates operational conditions.”

To guide future investments, NASA is leading the development of a green propellant roadmap along with other government agencies, industry and academic leaders who recently shared their collective experiences during a technical interchange meeting at Marshall.

“I like the analogy of relating thrusters and propellant systems to aircraft,” said Charles Pierce, manager of Marshall’s Spacecraft Propulsion Systems Branch, which recently completed the tests with LMP-103S. “One aircraft doesn’t meet every need. Some high performance aircraft need to fly fast while other larger aircraft need to conserve fuel and fly slowly. Some carry passengers while others carry only cargo. Likewise, NASA needs to have flexibility in the types of thrusters and propellant systems it has to meet a variety of mission needs. One type of propellant might work best for one type of mission while another is better suited for a different mission. It’s important that we have choices as we go green.”

– Credit and Resource –

Tracy McMahan

NASA Marshall Space Flight Center

256-544-0034

tracy.mcmahan@nasa.gov

Last Updated: Sep. 14, 2015

Editor: Lee Mohon

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New Green Propellants Complete Milestones