en.wikipedia.org/wiki/Messier_87
2 corrections found
The event horizon of the black hole at the center was directly imaged by the EHT
The EHT did not directly image M87*'s event horizon. It imaged the black hole's shadow/silhouette and the bright emission around it, which are larger than and distinct from the event horizon itself.
Full reasoning
This sentence conflates the event horizon itself with the shadow/silhouette and surrounding emission ring seen by the Event Horizon Telescope.
Official descriptions of the 2019 result make this distinction explicit:
- NASA explains that a black hole cannot itself be seen, because no light escapes it. What the EHT image shows is the black hole and its shadow, outlined by hot gas near the event horizon.
- ESO's official EHT image page says the shadow is the closest we can come to an image of the black hole itself, and that the event horizon is about 2.5 times smaller than the shadow it casts.
So the EHT result was not a direct image of the event horizon. It was an image of the shadow/silhouette cast by the black hole, plus the glowing material around it.
2 sources
- Black Hole Image Makes History; NASA Telescopes Coordinated Observations - NASA
A black hole and its shadow have been captured in an image for the first time... By its very nature, a black hole cannot be seen... The stunning new image shows the shadow of the supermassive black hole in the center of Messier 87 (M87).
- First Image of a Black Hole | ESO
The shadow of a black hole seen here is the closest we can come to an image of the black hole itself... The black hole's boundary — the event horizon — is around 2.5 times smaller than the shadow it casts.
with the core subgroup including M87 (Virgo A) and M49 (Virgo B)
Virgo A and Virgo B are separate Virgo Cluster substructures, not a single shared core subgroup. Virgo A is centered on M87, while Virgo B is centered on M49.
Full reasoning
This wording incorrectly merges Virgo A and Virgo B into one “core subgroup.” In standard descriptions of the Virgo Cluster, these are distinct subclusters/subclumps:
- Virgo A is the major subcluster centered on M87.
- Virgo B is a separate, smaller subcluster centered on M49.
Authoritative Virgo Cluster reviews describe the cluster as having multiple subconcentrations, with subcluster A around M87 and subcluster B around M49, rather than a single subgroup that includes both. So the sentence should not present M87/Virgo A and M49/Virgo B as one common “core subgroup.”
2 sources
- Virgo Cluster
There is a major subcluster (A) of galaxies around the giant E galaxy M87 ... there is a smaller, less dense subcluster (B) around the brightest cluster member M49.
- The Virgo Cluster - Home of M87
There is another double structure of the Virgo cluster ... defined by the northern M86 / M87 subclump structure (called “cluster A”) ... and the southern galaxy concentration around M49, called here the “M49 subclump” (= “cluster B”).