Thanks to Draper and its Hack the Moon initiative for supporting PBS Digital Studios. Imagine being a beam of light from a distant star, traveling across the universe. To trace my journey, you’d need two essential tools: a series of radio telescopes like the Submillimeter Array and one of the world’s most precise clocks. After traveling such a long distance, I arrive on Earth as a very faint signal. To detect me, multiple antennas must be pointed at the same spot in the sky. However, my signal reaches each telescope at slightly different times. By using an incredibly accurate clock, we can synchronize these signals and combine them to create a clearer image. With enough radio telescopes and a supercomputer, we can even capture something once thought impossible to see: a black hole.
On April 10, 2019, the Event Horizon Telescope collaboration made history by capturing the first-ever image of a black hole. This cosmic phenomenon, resembling a glowing ring, is a supermassive black hole located at the center of the M87 galaxy, about 55 million light-years away in the constellation Virgo. The orange ring we see is made up of photons from hot, swirling gas orbiting the black hole. The inner edge of this ring marks the event horizon, a point beyond which nothing can escape.
The Event Horizon Telescope isn’t a single telescope but a network of telescopes working together to form a larger, Earth-sized telescope. This collaboration allows us to see what was once deemed unseeable. The idea of dark, massive objects in space, dense enough to trap light, was first suggested by John Michell in the 18th century, who called them “dark stars.” The modern concept of black holes emerged from Einstein’s theory of general relativity. Throughout the 20th century, scientists sought to observe black holes, but how do you see something that doesn’t emit light?
Capturing an image of a black hole is like tuning in to your favorite radio station, but with a twist. Black holes don’t emit visible light, but the hot gas around them does emit light in other parts of the electromagnetic spectrum, which we can detect. Space is mostly transparent to radio waves, making them ideal for observation. However, radio waves have long wavelengths, making it challenging to produce sharp images. Despite their massive size, black holes appear tiny in the sky. Observing M87* from Earth is like trying to spot a bagel on the moon.
To solve this, scientists created a telescope as large as the Earth. By connecting radio telescopes worldwide, the Event Horizon Telescope achieves a resolution a thousand times better than the Hubble Space Telescope. This is possible by aligning the clocks between telescopes with extreme precision, down to a picosecond.
In April 2017, the Event Horizon Telescope pointed telescopes at eight locations worldwide, including the Submillimeter Array on Mauna Kea, to observe the black hole. They synchronized their observations using a highly precise clock called a hydrogen maser, which keeps time to within a billionth of a second. By combining the data in a supercomputer, they produced the first radio image of a black hole.
In a large science room, a supercomputer combines signals from various telescopes, formatting them for the Event Horizon Telescope. This is where the black hole image was captured. The hydrogen maser, located in a bunker, sends a reference tone to synchronize all clocks in the system. By combining waves through interferometry, scientists ensure they don’t lose the signal due to destructive interference. GPS timestamps and the hydrogen maser keep everything aligned on the shortest time scales.
The Event Horizon Telescope is now attempting to capture an image of the supermassive black hole at the center of our galaxy in the constellation Sagittarius. Thanks to generations of scientists, we’ve moved beyond using just our eyes to explore the universe. Each discovery solves one mystery while unveiling new ones, keeping us gazing at the stars in wonder.
If you think a planet-sized telescope is impressive, wait until you explore the vastness of the universe. Check out Matt O’Dowd from Space Time in the next episode.
Thanks to Draper and their Hack the Moon initiative for supporting PBS Digital Studios. Discover the story of the engineers behind the Apollo missions at wehackthemoon.com. Hack The Moon chronicles the technologies that made the moon landing possible. PBS brings you the universe with the SUMMER OF SPACE, featuring new science and history shows on PBS and streaming on PBS.org and the PBS Video app. Watch it all on PBS.org/summerofspace.
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Engage in a simulation exercise where you use virtual radio telescopes to capture an image of a black hole. Use software that mimics the Event Horizon Telescope’s process, adjusting parameters to understand how synchronization and data combination work.
Participate in a group discussion to explore the concept of interferometry. Discuss how combining signals from multiple telescopes enhances image resolution and why precise timing is crucial. Share insights on how this technique was pivotal in capturing the black hole image.
Prepare a presentation on the evolution of black hole theories, from John Michell’s “dark stars” to Einstein’s general relativity. Highlight key scientific advancements that led to the modern understanding of black holes and their observation.
Engage in a hands-on workshop analyzing real data from radio telescopes. Learn how to process and interpret this data using software tools, gaining insights into the challenges and techniques used in astrophysical research.
Write a creative narrative from the perspective of a photon traveling from a distant star to Earth. Describe the journey through space, the encounter with a black hole, and the eventual detection by the Event Horizon Telescope.
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Thank you to Draper and its Hack the Moon initiative for supporting PBS Digital Studios. Imagine for a moment that I’m a beam of light far outside the visible range, traveling from a star in a distant part of the universe. If you want to see where I came from, you’ll need two things: a series of radio telescopes like the Submillimeter Array and one of the most accurate clocks in the world. I’ve traveled a long way to get here, so when I arrive on Earth, I’m an extremely faint signal. To see me, you’ll need to point multiple antennas at the same point in the sky. But my faint signal will arrive at each telescope at ever so slightly different points in time. Using our incredibly precise clock, we can synchronize these signals and combine those faint images to create a much clearer picture. If you point enough radio telescopes at the exact same spot and have access to a supercomputer, you can even see something we once thought was unseeable: a black hole.
On April 10, 2019, astrophysicists from the Event Horizon Telescope collaboration made headlines with the first-ever image of a black hole. This astronomical donut, surrounded by a glowing ring, is a supermassive black hole weighing about 6.5 billion times the mass of our sun, located at the center of the M87 galaxy, approximately 55 million light-years away in the constellation Virgo. The orange ring we see consists of photons produced by hot, swirling gas orbiting around the edge of the black hole. The inner edge of that ring is the event horizon, a point of no return.
The Event Horizon Telescope is not just one telescope; it’s a network of many telescopes, including those here, working together as a larger telescope, allowing us to see something we once thought was impossible. The concept of dark, massive objects in space, dense enough to capture light itself, was first hinted at by John Michell in the 18th century, referring to them as “dark stars.” The first modern hints about black holes emerged as an abstract mathematical idea within Einstein’s theory of general relativity. Throughout the 20th century, scientists searched for black holes, but how do you observe the absence of light?
Creating an image of a light-swallowing cosmic abyss is akin to tuning in to hear your favorite song on the radio, but with a unique challenge. Black holes may not produce any light waves in the visible spectrum, but the hot clouds of swirling gas at their edges emit light in other parts of the electromagnetic spectrum that we can detect. Fortunately, space is mostly transparent to radio waves, which is what the Event Horizon Telescope team chose to observe. However, this presented astronomers with another challenge: radio waves have very long wavelengths, and the longer the wavelength of light used, the more difficult it is to produce a sharp image. Additionally, as massive as black holes are, they appear very tiny in the sky. From our vantage point on Earth, seeing M87* in the sky is like trying to see a bagel on the moon.
The solution? A telescope the size of the Earth.
Geoff, it’s great to meet you. Can you tell me how you captured that incredible image?
With the Event Horizon Telescope, we effectively use a telescope that has a resolution a thousand times better than the Hubble Space Telescope. The way to achieve finer detail and better angular resolution is by building a larger diameter aperture. We connect telescopes located around the world, all radio, to create a single telescope—a mirror the size of the entire planet, though most of the mirror is missing. To create that mirror, we need to have the clocks between the telescopes carefully aligned. We can synchronize our clocks to within a picosecond.
Over several nights in April 2017, the Event Horizon Telescope pointed telescopes at eight different locations around the world at the black hole, including the eight antennas here at the Submillimeter Array on Mauna Kea. To function as one, they synchronized their observations using an extremely precise clock at each site. This clock, called a hydrogen maser, can keep time to within a billionth of a second. By combining all the data in a supercomputer, they created the first-ever radio image of a black hole.
We’re in a large science room! What happens in here?
This is a big supercomputer, specially designed to combine the signals from all our different telescopes and format the combined signal for the Event Horizon Telescope.
This is where you captured the black hole image?
Exactly, light stopped right here. At the other end of this lab, the clock signals come in. The hydrogen maser is in a bunker underneath, sending up its reference tone 10 megahertz signal, which gets distributed to all the different clocks used throughout the system. We’re combining waves, which is what interferometry means. If those waves shift slightly when you combine them, they can destructively interfere, causing you to lose your signal. We use GPS to timestamp it and the hydrogen maser to ensure everything is aligned on the shortest time scales.
This is where our part of the Event Horizon Telescope data comes in, and we record the light, capturing it forever.
But this isn’t the end of our story. The Event Horizon Telescope is now trying to take a picture of the supermassive black hole at the center of our own galaxy in the constellation Sagittarius. Thanks to generations of scientists, we’re well beyond using just our eyes to see the universe. With each new discovery, one mystery ends, only to reveal even greater mysteries for new scientists to uncover, keeping us all looking out at the stars in wonder.
If you thought a planet-sized telescope was big, just wait until you find out how vast the universe is. Check out Matt O’Dowd from Space Time in the next episode.
Thank you to Draper and their Hack the Moon initiative for supporting PBS Digital Studios. You know the story of the astronauts who landed on the moon; now you can log on to wehackthemoon.com to discover the story of the engineers who guided them there and back safely. Hack The Moon chronicles the engineers and technologies behind the Apollo missions. Brought to you by Draper, the site is full of images, videos, and stories about the people who made the moon landing possible. PBS is bringing you the universe with the SUMMER OF SPACE, featuring six incredible new science and history shows airing on PBS and streaming on PBS.org and the PBS Video app. Watch it all on PBS.org/summerofspace.
Black Hole – A region of space having a gravitational field so intense that no matter or radiation can escape. – The discovery of a black hole at the center of our galaxy has provided new insights into the dynamics of galactic cores.
Event Horizon – The boundary surrounding a black hole beyond which no light or other radiation can escape. – As matter approaches the event horizon, it is stretched and heated, emitting radiation that can be detected by astronomers.
Telescope – An instrument designed to observe distant objects by collecting electromagnetic radiation. – The Hubble Space Telescope has captured some of the most detailed images of distant galaxies ever seen.
Photons – Elementary particles that are the quantum of the electromagnetic field, including electromagnetic radiation such as light. – Photons emitted from a star can travel across the universe, providing information about the star’s composition and motion.
Radio Waves – A type of electromagnetic radiation with wavelengths longer than infrared light, used in various forms of communication. – Radio waves are crucial for astronomers to study celestial objects that are not visible in other wavelengths.
Supercomputer – A high-performance computing machine used for complex calculations, often employed in simulations and modeling in physics and astronomy. – Researchers used a supercomputer to simulate the formation of large-scale structures in the universe.
Electromagnetic – Relating to the interrelation of electric currents or fields and magnetic fields. – The electromagnetic spectrum encompasses all types of electromagnetic radiation, from gamma rays to radio waves.
Galaxy – A massive, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter. – The Milky Way is a spiral galaxy that contains our solar system and billions of other stars.
Universe – The totality of known or supposed objects and phenomena throughout space; the cosmos. – The study of the universe’s expansion provides critical insights into its origin and ultimate fate.
Gravity – A natural phenomenon by which all things with mass or energy are brought toward one another, including planets, stars, and galaxies. – Gravity is the force that keeps planets in orbit around stars and governs the motion of galaxies.
