From: veritasium
The Event Horizon Telescope (EHT) collaboration released the first-ever image of a black hole on April 10, 2019 [00:00:02]. This image was of the supermassive black hole located at the center of the galaxy M87 [00:00:10]. While M87 was successfully imaged, the EHT also observed Sagittarius A* (Sgr A*), the supermassive black hole at the center of our own Milky Way galaxy, though an image of Sgr A* has not yet been released [00:03:45].
M87 Black Hole
The M87 black hole is a supermassive black hole with a mass 6.5 billion times that of our Sun [00:02:22]. Its shadow is nearly the size of our solar system [00:02:27]. It is located 53.5 million light-years away [00:02:34], making its apparent size from our perspective only about 40 micro arcseconds [00:02:38].
Key characteristics of the M87 black hole include:
- Activity: It is very active, constantly feeding on matter from its glowing hot accretion disk [00:00:56].
- Plasma Orbit: Plasma orbits clockwise around the black hole, completing one orbit in approximately 2 days [00:00:29]. This plasma appears brighter when moving towards us and dimmer when moving away due to relativistic beaming [00:00:20].
- Jets: It possesses narrow, collimated jets above and below it, thought to be created by strong magnetic fields [00:01:07]. These jets extend at least 5,000 light-years [00:01:18], with one pointing almost directly at Earth, made visible by relativistic beaming [00:01:23].
- Observation Wavelength: The image was created using electromagnetic waves with a wavelength of 1.3 millimeters (radio waves) [00:00:39]. This wavelength was chosen because it can reveal features close to the event horizon and can penetrate the accretion disk and interstellar dust to reach telescopes [00:00:48].
- Space-time Warping: The warping of space-time around the M87 black hole allows observers to see light even from parts of the accretion disk located behind the black hole; this light is lensed above and below the shadow region [00:01:45].
- Image Resolution: The image appears fuzzy because, despite its immense size, its angular size from Earth is extremely small [00:02:10]. To achieve this resolution, the Event Horizon Telescope collaboration used eight telescopes spread across the globe, simulating an Earth-sized telescope through the Earth’s rotation [00:03:28].
Sagittarius A* Black Hole
Sagittarius A* (Sgr A*) is the supermassive black hole at the center of our Milky Way galaxy [00:03:51].
- Mass: It has a mass only four million times that of our Sun [00:04:07].
- Distance: It is much closer than M87, located around 26,000 light-years away [00:04:03].
- Activity: Sgr A* is less active than M87, only periodically consuming matter [00:04:12].
- Plasma Orbit: The matter orbiting Sgr A* would exhibit much more variation over time, with orbits taking between four to thirty minutes [00:04:16]. This rapid variation is a likely reason why an image of Sgr A* has not yet been released [00:04:21].
Summary Comparison
| Feature | M87 Black Hole | Sagittarius A* Black Hole |
|---|---|---|
| Location | Center of galaxy M87 [00:00:10] | Center of our Milky Way galaxy [00:03:51] |
| Mass | 6.5 billion times the Sun’s mass [00:02:22] | 4 million times the Sun’s mass [00:04:07] |
| Distance | 53.5 million light-years away [00:02:34] | Around 26,000 light-years away [00:04:03] |
| Activity Level | Very active; constantly feeding [00:00:56] | Less active; periodically gobbling matter [00:04:12] |
| Plasma Orbit Time | Approximately 2 days [00:00:34] | 4 to 30 minutes [00:04:16] |
| Jets | Prominent, extending 5,000+ light-years [00:01:07] | Not mentioned |
| Image Status | First-ever image released (April 10, 2019) [00:00:02] | Simulation available; image not yet released [00:03:55] |