Nav: Home

Primordial black holes may have helped to forge heavy elements

August 04, 2017

Astronomers like to say we are the byproducts of stars, stellar furnaces that long ago fused hydrogen and helium into the elements needed for life through the process of stellar nucleosynthesis.

As the late Carl Sagan once put it: "The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff."

But what about the heavier elements in the periodic chart, elements such as gold, platinum and uranium?

Astronomers believe most of these "r-process elements"--elements much heavier than iron--were created, either in the aftermath of the collapse of massive stars and the associated supernova explosions, or in the merging of binary neutron star systems.

"A different kind of furnace was needed to forge gold, platinum, uranium and most other elements heavier than iron," explained George Fuller, a theoretical astrophysicist and professor of physics who directs UC San Diego's Center for Astrophysics and Space Sciences. "These elements most likely formed in an environment rich with neutrons."

In a paper published August 7 in the journal Physical Review Letters, he and two other theoretical astrophysicists at UCLA--Alex Kusenko and Volodymyr Takhistov--offer another means by which stars could have produced these heavy elements: tiny black holes that came into contact with and are captured by neutron stars, and then destroy them.

Neutron stars are the smallest and densest stars known to exist, so dense that a spoonful of their surface has an equivalent mass of three billion tons.

Tiny black holes are more speculative, but many astronomers believe they could be a byproduct of the Big Bang and that they could now make up some fraction of the "dark matter"--the unseen, nearly non-interacting stuff that observations reveal exists in the universe.

If these tiny black holes follow the distribution of dark matter in space and co-exist with neutron stars, Fuller and his colleagues contend in their paper that some interesting physics would occur.

They calculate that, in rare instances, a neutron star will capture such a black hole and then devoured from the inside out by it. This violent process can lead to the ejection of some of the dense neutron star matter into space.

"Small black holes produced in the Big Bang can invade a neutron star and eat it from the inside," Fuller explained. "In the last milliseconds of the neutron star's demise, the amount of ejected neutron-rich material is sufficient to explain the observed abundances of heavy elements."

"As the neutron stars are devoured," he added, "they spin up and eject cold neutron matter, which decompresses, heats up and make these elements."

This process of creating the periodic table's heaviest elements would also provide explanations for a number of other unresolved puzzles in the universe and within our own Milky Way galaxy.

"Since these events happen rarely, one can understand why only one in ten dwarf galaxies is enriched with heavy elements," said Fuller. "The systematic destruction of neutron stars by primordial black holes is consistent with the paucity of neutron stars in the galactic center and in dwarf galaxies, where the density of black holes should be very high."

In addition, the scientists calculated that ejection of nuclear matter from the tiny black holes devouring neutron stars would produce three other unexplained phenomenon observed by astronomers.

"They are a distinctive display of infrared light (sometimes termed a "kilonova"), a radio emission that may explain the mysterious Fast Radio Bursts from unknown sources deep in the cosmos, and the positrons detected in the galactic center by X-ray observations," said Fuller. "Each of these represent long-standing mysteries. It is indeed surprising that the solutions of these seemingly unrelated phenomena may be connected with the violent end of neutron stars at the hands of tiny black holes."

-end-

Funding for this project was provided by the National Science Foundation (PHY-1614864) at UC San Diego and by the U.S. Department of Energy (DE-SC0009937) at UCLA. Alex Kusenko was also supported, in part, by the World Premier International Research Center Initiative (WPI), MEXT, Japan.

University of California - San Diego

Related Black Holes Articles:

Supermassive black holes found in 2 tiny galaxies
U astronomers and colleagues have found two ultra-compact dwarf galaxies with supermassive black holes, the second and third such galaxies found to harbor the objects.
Stars born in winds from supermassive black holes
Observations using ESO's Very Large Telescope have revealed stars forming within powerful outflows of material blasted out from supermassive black holes at the cores of galaxies.
Did LIGO detect black holes or gravastars?
After the first direct detection of gravitational waves that was announced last February by the LIGO Scientific Collaboration and made news all over the world, Luciano Rezzolla (Goethe University Frankfurt, Germany) and Cecilia Chirenti (Federal University of ABC in Santo André, Brazil) set out to test whether the observed signal could have been a gravastar or not.
New research reveals hundreds of undiscovered black holes
Computer simulations of a spherical collection of stars known as 'NGC 6101' reveal that it contains hundreds of black holes, until now thought impossible.
Chorus of black holes radiates X-rays
The NuSTAR mission is identifying which black holes erupt with the highest-energy X-rays.
Did the LIGO gravitational waves originate from primordial black holes?
Binary black holes recently discovered by the LIGO-Virgo collaboration could be primordial entities that formed just after the Big Bang, report Japanese astrophysicists.
A new look at the galaxy-shaping power of black holes
Data from a now-defunct satellite is providing new insights into the complex tug-of-war between galaxies, the hot plasma that surrounds them, and the giant black holes that lurk in their centers.
The energy spectrum of particles will help make out black holes
Scientists from MIPT, the Institute for Theoretical and Experimental Physics, and the National Research University Higher School of Economics have devised a method of distinguishing black holes from compact massive objects that are externally indistinguishable from one another.
Using gravitational waves to catch runaway black holes
Black holes are the most powerful gravitational force in the universe.
Black holes and measuring gravitational waves
The supermassive black holes found at the center of every galaxy, including our own Milky Way, may, on average, be smaller than we thought, according to work led by University of Southampton astronomer Dr.

Best Science Podcasts 2017

We have hand picked the best science podcasts for 2017. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: Radiolab

Oliver Sipple
One morning, Oliver Sipple went out for a walk. A couple hours later, to his own surprise, he saved the life of the President of the United States. But in the days that followed, Sipple's split-second act of heroism turned into a rationale for making his personal life into political opportunity. What happens next makes us wonder what a moment, or a movement, or a whole society can demand of one person. And how much is too much?  Through newly unearthed archival tape, we hear Sipple himself grapple with some of the most vexing topics of his day and ours - privacy, identity, the freedom of the press - not to mention the bonds of family and friendship.  Reported by Latif Nasser and Tracie Hunte. Produced by Matt Kielty, Annie McEwen, Latif Nasser and Tracie Hunte. Special thanks to Jerry Pritikin, Michael Yamashita, Stan Smith, Duffy Jennings; Ann Dolan, Megan Filly and Ginale Harris at the Superior Court of San Francisco; Leah Gracik, Karyn Hunt, Jesse Hamlin, The San Francisco Bay Area Television Archive, Mike Amico, Jennifer Vanasco and Joey Plaster. Support Radiolab today at Radiolab.org/donate.
Now Playing: TED Radio Hour

Future Consequences
From data collection to gene editing to AI, what we once considered science fiction is now becoming reality. This hour, TED speakers explore the future consequences of our present actions. Guests include designer Anab Jain, futurist Juan Enriquez, biologist Paul Knoepfler, and neuroscientist and philosopher Sam Harris.