This week is Black Hole Week, and NASA is celebrating it by showing some stunning black hole visualizations, including a frankly disturbing visualization to help you imagine just how big a supermassive black hole is. Supermassive black holes are at the center of galaxies (including our own) and in general, the larger the galaxy, the larger the black hole.
Illustration of the black hole Sagittarius A* at the center of the Milky Way. International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/(Spaceengine) Credit: M. Zamani (NSFs NOIRLab)
While a typical black hole weighs about ten times the mass of the Sun, supermassive black holes can weigh millions or even billions of solar masses. However, these objects are incredibly dense, and it’s hard to imagine just how large such an object would be. That’s what this video comparison is all about, showing the size of different types of black holes compared to our solar system, scaled by their shadows.
Learning about black holes is challenging because their tremendous gravity means they absorb light that gets too close — but they often have disks of dust and gas swirling around them that rub against each other and get hot, causing them to die telescopes become visible. Astronomers can’t see the black holes themselves directly, but they can see this warm matter, and this is how the Event Horizon Telescope project was able to capture famous images of black holes.
This is the first image of Sagittarius A* (or Sgr A* for short), the supermassive black hole at the center of our galaxy. It is the first direct visible evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array connecting eight existing radio observatories around the planet to form a single “Earth-sized” virtual telescope. The telescope is named for the “event horizon,” the limit of the black hole beyond which no light can escape. EHT collaboration
Supermassive black holes are particularly interesting to study because we’re still learning about their relationship to the galaxies they inhabit and how they grow so large.
“Direct measurements, many using the Hubble Space Telescope, confirm the presence of more than 100 supermassive black holes,” said Jeremy Schnittman, theorist at NASA’s Goddard Space Flight Center, in a statement. “How do they get so big? When galaxies collide, their central black holes can also merge.”
This merging process would be epic and would create a force so great that gravitational waves would be detectable from Earth. But to tune into those waves, we need a new instrument like the upcoming Laser Interferometer Space Antenna mission, a collaboration between NASA and the European Space Agency that will use three spacecraft that shoot lasers at each other and will be able to to detect these gravitational waves.
“Since 2015, gravitational-wave observatories on Earth have detected mergers of tens of solar-mass black holes, thanks to the tiny ripples in spacetime that these events create,” said Goddard astrophysicist Ira Thorpe. “Supermassive black hole mergers will produce waves at much lower frequencies that can be detected with a space-based observatory millions of times larger than its Earth-based counterparts.”