Top Photo: The first image of a black hole! Photo courtesy of Event Horizon Telescope
Black holes—we’ve known about them, studied them, run computer simulations to model them. And on April 10, we got to see the first image of one!
Feryal Ozel is an astronomer and astrophysicist with the University of Arizona who studies black holes and neutron stars. She’s part of an international team of more than 200 scientists that took the first image a black hole. Dr. Ozel is on the science council for the project called the Event Horizon Telescope.
By SYNCHRONIZING eight radio telescopes around the globe, astronomers and engineers created a powerful virtual telescope to look at black holes. The project got underway 10 years ago, but the groundwork began well before that.
A black hole forms when a massive star—some can be billions of times larger than our sun—collapses in upon itself. “Black holes have collapsed into something infinitesimally small, according to our understanding, held up by nothing,” Dr. Ozel explains. “And they create this extreme warp in space-time that separates them from our universe!”
With so much mass, the gravity of a black hole is strong enough to prevent light from escaping. That gravity also draws matter into it.
But if light cannot escape a black hole, how do you photograph it? “What works to our advantage is that black holes pull matter from nearby stars and objects,” Dr. Ozel says. These gasses are pulled into a swirling, doughnut-shaped hurricane that heat up as they’re drawn in, emitting a lot of light, which can be photographed. And that boundary where no light or other radiation can escape is known as the black hole’s “event horizon.” According to Albert Einstein’s theory of relativity, that event horizon is proportional in size to its mass.
The Event Horizon Telescope (EHT) originally included the a radio telescope on Mount Graham run by the UofA in Southern Arizona, one in Antarctica also run by the UofA, two scopes in South America and Hawaii, one in Europe and one in Greenland.
The images from these telescopes were taken over a 10-day span in 2017. The telescopes were aimed at the supermassive black hole in the M87 galaxy in the Virgo cluster 57 million light years away. Its event horizon is about three times the size of our solar system! “It’s truly huge—it’s 6.5 billion times more massive than our sun,” Ozel says.
The EHT images generated 5,000 trillion bytes of data, stored on a half ton of hard drives! Scientists used new computer technology, cloud storage and came up with special algorithms to turn this data into this image.
Now the EHT has added two more radio telescopes and the scientists are crunching the data for a picture of the Milky Way’s black hole, Sagittarius A*, also taken in 2017.
“We were amazed and excited that our experiment worked,” Ozel says. “I was awed that it looked so much like what we had predicted.”
Time for a Change—Find Valuable Coins!
The Great American Coin Hunt just happened as part of National Coin Week April 21–27.
Coin dealers all over the country snuck thousands of old and valuable coins into our change system. And to get young and old excited about collecting coins again, the U.S. Mint kicked things off by putting special quarters into circulation!
To celebrate its 227th birthday on April 2, the U.S. Mint released 2 million of each of its five 2019 America the Beautiful quarters with a W mint mark on its obverse (front or heads side). These coins were struck—the process whereby round flat blanks of metal are made into coins—at the West Point Mint in New York. These special W quarters represent just 1 percent of those quarters in circulation! “We want to encourage Americans to consider coin collecting by making the W mint mark quarters only available in general circulation,” says Mint Director David Ryder.
With so many people buying things electronically these days, coin collecting has lost some of its shine. So coin collectors and the U.S. Mint want to boost interest in what’s rattling around in your piggy bank or pocket!
If you didn’t know, NUMIS-MATICS is the collecting and/or study of coins and related stuff.
The idea for the Great American Coin Hunt has been in the works for years, according to Rob Oberth, one of the lead coin dealers for this event as part of National Coin Week. The idea is to put the thrill of the hunt back into hobby. So find those Indian Head pennies, Buffalo nickels, silver dimes and W mint quarters!