Supermassive black holes are elusive creatures. Massive gravitational beasts that can power immensely bright quasars, or can lurk quietly among the bright stars of a galactic core. We mostly study them indirectly through their bright accretion disks or powerful jets of plasma they create, but we have been able to observe them more directly, such as our images of M87* and Sag A*. But what still eludes us is capturing a direct image of the enigmatic photon ring. A new work in Acta Astronautica proposes how this might be done.Continue reading “Here's What it Would Take to See a Black Hole's Photon Ring”
Millisecond pulsars are amazing astronomical tools. They are fast-rotating neutron stars that sweep beams of radio energy from their magnetic poles, and when they are aligned just right we see them as rapidly flashing radio beacons. They flash with such regularity that we can treat them as cosmic clocks. Any change in their motion can be measured with extreme precision. Astronomers have used millisecond pulsars to measure their orbital decay due to gravitational waves and to observe the background gravitational rumblings of the universe. They have even been proposed as a method of celestial navigation. They may soon also be able to test the most fundamental nature of gravity.Continue reading “Astronomers are Hoping the Event Horizon Telescope saw Pulsars Near the Milky Way's Supermassive Black Hole”
New technologies bring new astronomical insights, which is especially satisfying when they help answer debates that have been ongoing for decades. One of those debates is why exactly the plasma emitted from pulsars “collimates” or is brought together in a narrow beam. While it doesn’t provide a definitive answer to that question, a new paper from an international group of scientists points to a potential solution, but it will require even more advanced technologies.Continue reading “Quasars Produce Giant Jets That Focus Like Lasers. Why They Focus is Still a Mystery, but it’s not Coming From the Galaxy Itself”
In 2019 the Event Horizon Telescope gave us our first direct image of a black hole. It was a powerful image, but not one with much detail. It looks like a blurry orange donut. To be fair, the real meat of the discovery was in the data, not the image. And as a recent study shows, there’s a great deal more in the data than what we’ve seen.Continue reading “Astronomers Have Revealed a Black Hole's Photon Ring for the First Time”
On April 10th, 2019, the world was treated to the first image of a black hole, courtesy of the Event Horizon Telescope (EHT). Specifically, the image was of the Supermassive Black Hole (SMBH) at the center of the supergiant elliptical galaxy known as M87 (aka. Virgo A). These powerful forces of nature are found at the centers of most massive galaxies, which include the Milky Way (where the SMBH known as Sagittarius A* is located).
Using a technique known as Very-Long-Baseline Interferometry (VLBI), this image signaled the birth of a new era for astronomers, where they can finally conduct detailed studies of these powerful forces of nature. Thanks to research performed by the EHT Collaboration team during a six-hour observation period in 2017, astronomers are now being treated to images of the core region of Centaurus A and the radio jet emanating from it.Continue reading “The Event Horizon Telescope Zooms in on Another Supermassive Black Hole”
Back in 2019, the world was treated to the first ever image of a black hole, which was originally captured in 2017. The feat was widely heralded as a leap forward for astrophysics, supporting Einstein’s Theory of Relativity. Now a team led by the Radboud University proposes sending instruments into space to estimate black hole parameters more accurately by an order of magnitude. The newest paper, led by Dr. Volodymyr Kudriashov, translates science goals into technical requirements and focuses on the instrumentation needed for the Event Horizon Imager, as the mission is called.Continue reading “Space Telescopes Could Provide Next-Level Images of Black Hole Event Horizons”
“We have taken the first picture of a black hole.”
EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian.
What was once un-seeable can now be seen. Black holes, those difficult-to-understand singularities that may reside at the center of every galaxy, are becoming seeable. The Event Horizon Telescope (EHT) has revealed the first-ever image of a black hole, and with this image, and all the science behind it, they may help crack open one of the biggest mysteries in the Universe.Continue reading “It’s Finally here. The First Ever Image of a Black Hole”
Scientists have long suspected that supermassive black holes (SMBH) reside at the center of every large galaxy in our universe. These can be billions of times more massive than our sun, and are so powerful that activity at their boundaries can ripple throughout their host galaxies.
In the case of the Milky Way galaxy, this SMBH is believed to correspond with the location of a complex radio source known as Sagittarius A*. Like all black holes, no one has even been able to confirm that they exist, simply because no one has ever been able to observe one.
But thanks to researchers working out of MIT’s Haystack Observatory, that may be about to change. Using a new telescope array known as the “Event Horizon Telescope” (EHT), the MIT team hopes to produce this “image of the century” very soon.Initially predicted by Einstein, scientists have been forced to study black holes by observing their apparent effect on space and matter in their vicinity. These include stellar bodies that have periodically disappeared into dark regions, never to be heard from again.
As Sheperd Doeleman, assistant director of the Haystack Observatory at Massachusetts Institute of Technology (MIT), said of black holes: “It’s an exit door from our universe. You walk through that door, you’re not coming back.”
As the most extreme object predict by Einstein’s theory of gravity, supermassive black holes are the places in space where, according to Doeleman, “gravity completely goes haywire and crushes an enormous mass into an incredibly close space.”
To create the EHT array, the scientists linked together radio dishes in Hawaii, Arizona, and California. The combined power of the EHT means that it can see details 2,000 times finer than what’s visible to the Hubble Space Telescope.
These radio dishes were then trained on M87, a galaxy some 50 million light years from the Milky Way in the Virgo Cluster, and Sagittarius A* to study the event horizons at their cores.
Other instruments have been able to observe and measure the effects of a black hole on stars, planets, and light. But so far, no one has ever actually seen the Milky Way’s Supermassive black hole.
According to David Rabanus, instruments manager for ALMA: “There is no telescope available which can resolve such a small radius,” he said. “It’s a very high-mass black hole, but that mass is concentrated in a very, very small region.”
Doeleman’s research focuses on studying super massive black holes with sufficient resolution to directly observe the event horizon. To do this his group assembles global networks of telescopes that observe at mm wavelengths to create an Earth-size virtual telescope using the technique of Very Long Baseline Interferometry (VLBI).
“We target SgrA*, the 4 million solar mass black hole at the center of the Milky Way, and M87, a giant elliptical galaxy,” says Doeleman. “Both of these objects present to us the largest apparent event horizons in the Universe, and both can be resolved by (sub)mm VLBI arrays.” he added. “We call this project The Event Horizon Telescope (EHT).”
Ultimately, the EHT project is a world-wide collaboration that combines the resolving power of numerous antennas from a global network of radio telescopes to capture the first image ever of the most exotic object in our Universe – the event horizon of a black hole.
“In essence, we are making a virtual telescope with a mirror that is as big as the Earth,” said Doeleman who is the principal investigator of the Event Horizon Telescope. “Each radio telescope we use can be thought of as a small silvered portion of a large mirror. With enough such silvered spots, one can start to make an image.”
“The Event Horizon Telescope is the first to resolve spatial scales comparable to the size of the event horizon of a black hole,” said University of California, Berkeley astronomer Jason Dexter. “I don’t think it’s crazy to think we might get an image in the next five years.”
First postulated by Albert Einstein’s Theory of General Relativity, the existence of black holes has since been supported by decades’ worth of observations, measurements, and experiments. But never has it been possible to directly observe and image one of these maelstroms, whose sheer gravitational power twists and mangle the very fabric of space and time.
Finally being able to observe one will not only be a major scientific breakthrough, but could very well provide the most impressive imagery ever captured.
“Sgr A* is the right object, VLBI is the right technique, and this decade is the right time.”
So states the mission page of the Event Horizon Telescope, an international endeavor that will combine the capabilities of over 50 radio telescopes across the globe to create a single Earth-sized telescope to image the enormous black hole at the center of our galaxy. For the first time, astronomers will “see” one of the most enigmatic objects in the Universe.
And tomorrow, January 18, researchers from around the world will convene in Tucson, AZ to discuss how to make this long-standing astronomical dream a reality.
During a conference organized by Dimitrios Psaltis, associate professor of astrophysics at the University of Arizona’s Steward Observatory, and Dan Marrone, an assistant professor of astronomy at the Steward Observatory, astrophysicists, scientists and researchers will gather to coordinate the ultimate goal of the Event Horizon Telescope; that is, an image of Sgr A*’s accretion disk and the “shadow” of its event horizon.
“Nobody has ever taken a picture of a black hole. We are going to do just that.”
– Dimitrios Psaltis, associate professor of astrophysics at the University of Arizona’s Steward Observatory
Sgr A* (pronounced as “Sagittarius A-star”) is a supermassive black hole residing at the center of the Milky Way. It is estimated to contain the equivalent mass of 4 million Suns, packed into an area smaller than the diameter of Mercury’s orbit.
Because of its proximity and estimated mass, Sgr A* presents the largest apparent event horizon size of any black hole candidate in the Universe. Still, its size in the sky is about the same as viewing “a grapefruit on the Moon.”
So what are astronomers expecting to actually “see”?
(Read more: What does a black hole look like?)
Because black holes by definition are black – that is, invisible in all wavelengths of radiation due to the incredibly powerful gravitational effect on space-time around them – an image of the black hole itself will be impossible. But Sgr A*’s accretion disk should be visible to radio telescopes due to its billion-degree temperatures and powerful radio (as well as submillimeter, near infrared and X-ray) emissions… especially in the area leading up to and just at its event horizon. By imaging the glow of this super-hot disk astronomers hope to define Sgr A*’s Schwarzschild radius – its gravitational “point of no return”.
This is also commonly referred to as its shadow.
The position and existence of Sgr A* has been predicted by physics and inferred by the motions of stars around the galactic nucleus. And just last month a giant gas cloud was identified by researchers with the European Southern Observatory, traveling directly toward Sgr A*’s accretion disk. But, if the EHT project is successful, it will be the first time a black hole will be directly imaged in any shape or form.
“So far, we have indirect evidence that there is a black hole at the center of the Milky Way,” said Dimitrios Psaltis. “But once we see its shadow, there will be no doubt.”
The ambitious Event Horizon Telescope project will use not just one telescope but rather a combination of over 50 radio telescopes around the world, including the Submillimeter Telescope on Mt. Graham in Arizona, telescopes on Mauna Kea in Hawaii and the Combined Array for Research in Millimeter-wave Astronomy in California, as well as several radio telescopes in Europe, a 10-meter dish at the South Pole and, if all goes well, the 50-radio-antenna capabilities of the new Atacama Large Millimeter Array in Chile. This coordinated group effort will, in effect, turn our entire planet into one enormous dish for collecting radio emissions.
By using long-term observations with Very Long Baseline Interferometry (VLBI) at short (230-450 GHz) wavelengths, the EHT team predicts that the goal of imaging a black hole will be achieved within the next decade.
“What is great about the one in the center of the Milky Way is that is big enough and close enough,” said assistant professor Dan Marrone. “There are bigger ones in other galaxies, and there are closer ones, but they’re smaller. Ours is just the right combination of size and distance.”