The Holidays are upon us -
Be sure to take some time to come to the Imaginarium during the holiday season. Hokulani Imaginarium is scheduling family-friendly seasonal shows beginning Saturday, November 24, at 2:00 p.m. with the ever popular Season of Light
that traces many of the world's most enduring customs at this time of year from Christmas trees, and the Hanukkah Menorah, to Santa Clause and the Star of Bethlehem.
Will we ever see a black hole for real?
Two things that school students who visit the Hokulani Imaginarium full dome shows always ask: “Are we going to see aliens and black holes?” They, like astronomers, want to see what is as yet “unseen”.
We live 26,000 light-years from the center of the Milky Way
. This distance hasn’t stopped astronomers from drawing a fairly accurate map of the heart of the galaxy and the galactic bulge. If you stargaze and find the Sagittarius constellation, you are looking in the direction of the heart of our galaxy. Several thousand light-years farther in, there’s Sagittarius B2
, a cloud a thousand times the size of our solar system. Another 393 light-years farther and you are at the galactic center. This is the supermassive black hole at the core of the Milky Way, the still point of our slowly rotating galaxy. We call it Sagittarius A*, pronounced “A-star
Scientists have long wondered what they would see if they could peer all the way to its edge. They may soon find out. Astronomers found Sagittarius A* in 1974, when the notion of holes in space was still new and unsettling. Last year, after more than a decade of preparation, astronomers from North and South America, Europe and Asia attempted to take the first picture of a black hole utilizing the Event Horizon Telescope
(E.H.T.), a virtual Earth-size observatory. The E.H.T. uses a technique in which astronomers at observatories on different continents simultaneously observe the same object, and then combine the collected data on a supercomputer.
So why do a bunch of people around the world pursue such a singular esoteric goal? Afterall, a black hole is not an object per se but more pure gravity. How does one photograph pure gravity? In many ways people who pursue such a singular goal are like kids who want to see black holes – they want to see what seems to be unseeable – they want to understand.
Astronomers and scientists think a black hole is the ideal place to test the theory of general relativity
, which describes the universe on the largest scale.
Another, equally successful, equally unbreakable theory of nature has coexisted awkwardly alongside general relativity for a century: quantum theory
. Quantum theory governs the subatomic world. General relativity and quantum theory both govern their respective domains perfectly. The problem is that they describe worlds that look nothing like each other.
The two theories, which I can’t begin to understand, collide most violently in black holes. For example, scientists say Sagittarius A* is a four-million-solar-mass black hole, implying that the black hole “contains” four million suns’ worth of matter. But Einstein’s equations say that the interior of a black hole is a vacuum, and that all the matter that has ever fallen in is packed into an infinitely dense, infinitely small surface at the center of the black hole called a “singularity
”. This doesn’t make much sense to scientists. To understand what happens at the singularity, scientists need a theory of quantum gravity: a framework that unites general relativity with quantum theory. That theory may reveal what happens, or happened, at other singularities, including the one that begot our universe — the Big Bang
. But it’s hard to reconcile two conflicting theories if you can’t find something wrong with either one, and quantum theory, like general relativity, has passed every test. As a result, scientists have been looking for ever-more-extreme situations in which to test these theories. That led them to black holes. Images of black holes like the one below are artist's conceptions, not actual photographs.
The recent effort to photograph a black hole has been long in the making dating back to the late 1990s when astrophysicists Heino Falcke, Fulvio Melia and Eric Agol
concluded that with an Earth-size collection of radio telescopes, all of them operating at the highest frequencies of the radio spectrum, all of them simultaneously observing Sagittarius A*, one would see a dark circle ten times larger than the event horizon. At the edge of this circle, light rays would be trapped, tracing a glowing ring and inside this ring, darkness. Scientists believed Sagittarius A* should cast a shadow.
With this possibility in mind Shep Doleman
, radio astronomer, willed the earliest incarnation of the Event Horizon Telescope into existence. In 2007 Doleman and a small crew set out to prove the concept, to see whether they could get a triangle of high-frequency radio telescopes in Hawaii, California and Arizona to detect Sagittarius A*. They didn’t have the telescopic power to make an image, but they saw something
— a shape smaller than Sagittarius A*’s event horizon. More like-minded scientists joined the team every year.
In April 2017 on five nights over a span of 10 days, teams at high-altitude observatories in France, Mexico, Chile, Arizona, Hawaii and the South Pole tracked Sagittarius A* through the night. When the inaugural E.H.T. observing run concluded on April 11, 2017, the astronomers had recorded more than 65 hours of data. For more than a year they calibrated and corrected and reality-checked their data.
At some point within the next few months, the astronomers will finish their final analysis and submit their results to a scientific journal for peer review. If everything is in order, the results will be published, and then the world will see — something
— perhaps something that has never been seen before.
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