Earth’s Gold Came From Colliding Stars

Are you wearing a gold ring? Or perhaps gold-plated earrings? Maybe you have some gold fillings in your teeth… for that matter, the human body itself naturally contains gold — 0.000014%, to be exact! But regardless of where and how much of the precious yellow metal you may have with you at this very moment, it all ultimately came from the same place.

And no, I don’t mean Fort Knox, the jewelry store, or even under the ground — all the gold on Earth likely originated from violent collisions between neutron stars, billions of years in the past.

Recent research by scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts has revealed that considerable amounts of gold — along with other heavy elements — are produced during impacts between neutron stars, the super-dense remains of stars originally 1.4 to 9 times the mass of our Sun.

The team’s investigation of a short-duration gamma-ray outburst that occurred in June (GRB 130603B) showed a surprising residual near-infrared glow, possibly from a cloud of material created during the stellar merger. This cloud is thought to contain a considerable amount of freshly-minted heavy elements, including gold.

“We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses – quite a lot of bling!” said lead author Edo Berger.

"With this remnant of a dead neutron star, I thee wed." (FreeDigitalPhotos.net/bigjom)
“With this remnant of a dead neutron star, I thee wed.” (FreeDigitalPhotos.net/bigjom)

The mass of the Moon is 7.347 x 1022 kg… about 1.2% the mass of Earth. The collision between these neutron stars then, 3.9 billion light-years away, produced 10 times that much gold based on the team’s estimates.

Quite a lot of bling, indeed.

Gamma-ray bursts come in two varieties – long and short – depending on the duration of the gamma-ray flash. GRB 130603B, detected by NASA’s Swift satellite on June 3rd, lasted for less than two-tenths of a second.

Although the gamma rays disappeared quickly, GRB 130603B also displayed a slowly fading glow dominated by infrared light. Its brightness and behavior didn’t match the typical “afterglow” created when a high-speed jet of particles slams into the surrounding environment.

Instead, the glow behaved like it came from exotic radioactive elements. The neutron-rich material ejected by colliding neutron stars can generate such elements, which then undergo radioactive decay, emitting a glow that’s dominated by infrared light – exactly what the team observed.

“We’ve been looking for a ‘smoking gun’ to link a short gamma-ray burst with a neutron star collision,” said Wen-fai Fong, a graduate student at CfA and a co-author of the paper. “The radioactive glow from GRB 130603B may be that smoking gun.”

The team calculates that about one-hundredth of a solar mass of material was ejected by the gamma-ray burst, some of which was gold. By combining the estimated gold produced by a single short GRB with the number of such explosions that have likely occurred over the entire age of the Universe, all the gold in the cosmos – and thus on Earth – may very well have come from such gamma-ray bursts.

Watch an animation of two colliding neutron stars along with the resulting GRB below (Credit: Dana Berry, SkyWorks Digital, Inc.):

How much gold is there on Earth, by the way? Since most of it lies deep inside Earth’s core and is thus unreachable, the total amount ever retrieved by humans over the course of history is surprisingly small: about 172,000 tonnes, or enough to make a cube 20.7 meters (68 feet) per side (based on the Thomson Reuters GFMS annual survey.) Some other estimates put this amount at slightly more or less, but the bottom line is that there really isn’t all that much gold available in Earth’s crust… which is partly what makes it (and other “precious” metals) so valuable.

And perhaps the knowledge that every single ounce of that gold was created by dead stars smashing together billions of years ago in some distant part of the Universe would add to that value.

“To paraphrase Carl Sagan, we are all star stuff, and our jewelry is colliding-star stuff,” Berger said.

The team’s findings were presented today in a press conference at the CfA in Cambridge. (See the paper here.)

Source: Harvard-Smithsonian CfA

Book Review: Your Ticket to the Universe

Your Ticket to the Universe is full of images and graphics of astronomical wonders.
Your Ticket to the Universe is full of images and graphics of astronomical wonders.

Every once in a while an astronomy book comes out that combines stunning high-definition images from the world’s most advanced telescopes, comprehensive descriptions of cosmic objects that are both approachable and easy to understand (but not overly simplistic) and a gorgeous layout that makes every page spread visually exciting and enjoyable.

This is one of those books.

Your Ticket to the Universe: A Guide to Exploring the Cosmos is a wonderful astronomy book by Kimberly K. Arcand and Megan Watzke, media coordinator and press officer for NASA’s Chandra X-ray Observatory, respectively. Published by Smithsonian Books, it features 240 pages of gorgeous glossy images from space exploration missions, from the “backyard” of our own Solar System to the more exotic environments found throughout the Galaxy… and even beyond to the very edges of the visible Universe itself.

Find out how you can win a copy of this book here!

As members of the Chandra team, headquartered at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, Kim and Megan have long had firsthand experience with incredible astronomical images — they previously designed and coordinated the internationally-acclaimed From Earth to the Universe and From Earth to the Solar System photo installation projects, which helped set up presentations of space exploration images in public locations around the world.

Your Ticket to the Universe features images from some of the most recent missions - like MSL!
Your Ticket to the Universe even features images from some of the most recent missions – like MSL!

Your Ticket to the Universe takes such impressive images — from telescopes and observatories like Hubble, Spitzer, SDO, Chandra, Cassini, GOES, VLT, and many others, as well as from talented photographers on Earth and in orbit aboard the ISS — and puts them right into your hands, along with in-depth descriptions that are comprehensive yet accessible to even the most casual fans of space exploration.

This is my favorite kind of astronomy book. Although I look at images like the ones in Your Ticket to the Universe online every day, there’s something special about having them physically in front of you in print — and well-written text that can be understood by everyone is crucial, in my opinion, as it means a book may very well become an inspiration to a whole new generation of scientists and explorers.

“The sky belongs to everyone. That’s the premise of this guidebook to the Universe. You don’t need a medical degree to know when you’re sick or a doctorate in literature to appreciate a novel. In the same spirit, even those of us who don’t have advanced degrees in astronomy can gain access to all the wonder and experience that the Universe has to offer.”

Kim K. Arcand holds a copy of her book during a presentation at the Skyscrapers Astronomical Society of Rhode Island
Author Kimberly K. Arcand holds a copy of her book during a presentation at the Skyscrapers Astronomical Society of Rhode Island

I’ve had the pleasure of meeting co-author Kimberly Arcand on several occasions — I attended high school with her husband — and her knowledge about astronomy imaging as well as her ability to present it in an understandable way is truly impressive, to say the least. She’s quite an enthusiastic ambassador for space exploration, and Your Ticket to the Universe only serves to further demonstrate that.

I highly recommend it for anyone who finds our Universe fascinating.

Your Ticket to the Universe will be available online starting April 2 at Smithsonian Books, or you can pre-order a copy at Barnes & Noble or on Amazon.com. Don’t explore the cosmos without it!