Key facts
- NASA defines black holes as concentrations of matter compressed into a very small space.
- NASA’s summary puts stellar-mass black holes at between three and dozens of solar masses, and supermassive ones at roughly 100,000 to billions of solar masses.
- According to NASA, the motions of stars near the Milky Way’s centre were used to demonstrate the presence of a supermassive black hole there.
- ESO describes a measurement of a distant black hole associated with GRAVITY+, but the available summary gives neither figures nor uncertainties.
- NASA reports Webb-related interpretations involving GLIMPSE-17775; the available summaries are not enough to verify their details or editorial status.
Related records
Black holes attract interest because they combine a difficult idea to picture—much matter concentrated into very little space—with a practical challenge: they are not studied like a star that emits light and can be seen directly. NASA’s basic explanation is that gravity near the event horizon is extreme. The horizon marks a boundary relevant to the object; it is not a solid surface like a planet’s. Astronomers therefore also look for signs of what happens around a black hole.
This distinction helps avoid a misleading picture. Calling it a “hole” does not mean it is an empty cavity, and its existence does not imply that everything nearby must fall in. The information provided describes compact objects and mentions observations of stars and gas, but it does not give enough detail to explain here the conditions for capture or the orbits of each particular system.
One familiar name for objects on very different scales
NASA distinguishes stellar-mass and supermassive black holes. According to its public-facing summary, stellar-mass black holes have between three and dozens of times the Sun’s mass and are spread across the Milky Way. Supermassive black holes range from about 100,000 solar masses to billions of solar masses. These are broad ranges: the sources consulted do not provide a complete inventory or data with which to calculate how many exist.
The difference in scale matters because “black hole” does not name a single class of object with one characteristic mass. A report about a supermassive black hole in a distant galaxy should not be confused with the stellar-mass population in our own galaxy. The materials available also do not describe an intermediate category here or allow comparisons of formation rates.
How astronomers infer something they do not see directly
One approach is to track the motion of nearby objects. NASA says astronomers followed the orbits of several stars near the Milky Way’s centre and that those motions demonstrated that a supermassive black hole is there. The general idea is to study gravitational effects on the surroundings, rather than assign the black hole a directly visible surface.
The movement of gas can provide another clue. In an announcement about GRAVITY+, the European Southern Observatory (ESO) explains that astronomers use telescopes to track the motion of gas and stars in order to measure a black hole’s mass directly. The announcement presents a measurement of a distant black hole and links it to GRAVITY+, but the available summary does not specify the mass, distance, margin of error or associated scientific paper. It is therefore not possible to reconstruct or assess the measurement from that brief text.
Webb and questions about the early universe
The James Webb Space Telescope is a NASA space observatory. One agency page reports a black hole that may have formed before its galaxy. That wording raises a question about the order and pace at which black holes and galaxies grow. The summary provided, however, does not include the object’s age, the evidence used or the details of the analysis; on its own, it is not enough to explain how that sequence was established.
Another NASA page describes GLIMPSE-17775 as a candidate interpreted as a supermassive black hole hidden by a dense envelope of partly ionised gas, and says that analysis of its spectrum provides several lines of evidence supporting that model. The description presents an interpretation supported by evidence, not a claim free of uncertainty. It does not provide the spectrum, the alternatives considered or the paper’s editorial status, so the case should not be presented with more certainty than the summary allows.
Findings that need context and clear limits
Other NASA summaries mention a black hole that appears to be “sideways” and spinning in an unexpected direction relative to its galaxy, as well as a study seeking to estimate what proportion of active supermassive black holes are hidden. These point to different research questions: orientation and spin in one case, and a potentially overlooked population in the other. The descriptions provide no figures, detailed observations or quantitative conclusions, so they do not establish what proportion is hidden or what mechanism produced that orientation.
The type of source also matters. The material available here consists of institutional pages and short descriptions, not the full scientific papers. In one case, ESO says the measurement is described in a paper, but the information provided does not establish whether that paper has been peer reviewed. Nor should peer review be assumed merely because research appears in an index or on an institutional page. Without the full documents, the methods, numerical uncertainties, possible alternative explanations and precise scope of each result remain unresolved.
Taken together, the clearest picture these sources support is straightforward: black holes are extreme concentrations of matter; their masses span very different scales; and their presence can be inferred from their influence on stars or gas. Webb and other observatories extend the questions to distant, difficult-to-interpret objects, but each specific claim must be read in light of its evidence and limitations.