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The Proper Motion of Sgr A*: II. The Mass of Sgr A*

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Paper breakdownThe authors' claims, conditions and measurements, as JSON Signed receiptProof this review has not been altered
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M. J. Reid (1), A. Brunthaler (2) ((1) Harvard-Smithsonian Center for Astrophysics, (2) Max-Planck-Institut fuer Radioastronomie, Joint Institute for VLBI in Europe)

Astrophysics · Submitted 5 Aug 2004

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim Our observations provide the first direct evidence that a compact radiative source at the center of a galaxy contains of order 10^6 Msun and provides overwhelming evidence that it is in the form of a super-massive black hole.

how it is stated · asserted 1.00 read the record →

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arXiv IDastro-ph/0408107 (version 1)
Pith IDEAIYONLN, Pith's permanent record of this paper and its review
Citation(2) Max-Planck-Institut fuer Radioastronomie, A. Brunthaler (2) ((1) Harvard-Smithsonian Center for Astrophysics, Joint Institute for VLBI in Europe), M. J. Reid (1). "The Proper Motion of Sgr A*: II. The Mass of Sgr A*." arXiv:astro-ph/0408107 (2004). https://pith.science/paper/EAIYONLN
Claim paper

The compiled record

The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Open the compiled record

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 6,023 input tokens.

What the abstract itself states, as probabilities: claims first 0.82 · states limitation 0.50 · human participants 0.01 · controlled comparison 0.09 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.84 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We report measurements with the VLBA of the position of Sgr A* with respect to two extragalactic radio sources over a period of eight years. The apparent proper motion of \sgrab relative to J1745-283 is 6.379 +/- 0.024 mas/y along a position angle of 209.60 +/- 0.18 degrees, almost entirely in the plane of the Galaxy. The effects of the orbit of the Sun around the Galactic center can account for this motion, and the residual proper motion of Sgr A* perpendicular to the plane of the Galaxy is -0.4 +/- 0.9 km/s. A maximum-likelihood analysis of the motion expected for a massive object within the observed Galactic center stellar cluster indicates that Sgr A* contains more than about 10% of the approximately 4 x 10^6 Msun deduced from stellar orbits. The intrinsic size of Sgr A*, as measured by several investigators, is less than 1 AU, and the implied mass density of ~10^22 Msun/pc^3 is within about three orders of magnitude of a comparable super-massive black hole within its Schwarzschild radius. Our observations provide the first direct evidence that a compact radiative source at the center of a galaxy contains of order 10^6 Msun and provides overwhelming evidence that it is in the form of a super-massive black hole. Finally, the existence of "intermediate mass" black holes more massive than ~10^4 Msun between roughly 10^3 and 10^5 AU from Sgr A* are excluded.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We report measurements with the VLBA of the position of Sgr A* with respect to two extragalactic radio sources over a period of eight years. method 0.57 0.97 0.02 asserted 1.00
s1 The apparent proper motion of \sgrab relative to J1745-283 is 6.379 +/- 0.024 mas/y along a position angle of 209.60 +/- 0.18 degrees, almost entirely in the plane of the Galaxy. result 1.00 0.94 0.04 asserted 1.00
s2 The effects of the orbit of the Sun around the Galactic center can account for this motion, and the residual proper motion of Sgr A* perpendicular to the plane of the Galaxy is -0.4 +/- 0.9 km/s. result 0.73 0.84 0.04 asserted 0.79
s3 A maximum-likelihood analysis of the motion expected for a massive object within the observed Galactic center stellar cluster indicates that Sgr A* contains more than about 10% of the approximately 4 x 10^6 Msun deduced from stellar orbits. result 0.91 0.77 0.13 hedged possibility 0.97
s4 The intrinsic size of Sgr A*, as measured by several investigators, is less than 1 AU, and the implied mass density of ~10^22 Msun/pc^3 is within about three orders of magnitude of a comparable super-massive black hole within its Schwarzschild radius. interpretation 0.59 0.20 0.09 asserted 0.91
s5 Our observations provide the first direct evidence that a compact radiative source at the center of a galaxy contains of order 10^6 Msun and provides overwhelming evidence that it is in the form of a super-massive black hole. interpretation 0.92 0.87 0.88 asserted 1.00
s6 Finally, the existence of "intermediate mass" black holes more massive than ~10^4 Msun between roughly 10^3 and 10^5 AU from Sgr A* are excluded. result 0.99 0.72 0.06 asserted 1.00

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 1.00.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper
Original abstract

We report measurements with the VLBA of the position of Sgr A* with respect to two extragalactic radio sources over a period of eight years. The apparent proper motion of \sgrab relative to J1745-283 is 6.379 +/- 0.024 mas/y along a position angle of 209.60 +/- 0.18 degrees, almost entirely in the plane of the Galaxy. The effects of the orbit of the Sun around the Galactic center can account for this motion, and the residual proper motion of Sgr A* perpendicular to the plane of the Galaxy is -0.4 +/- 0.9 km/s. A maximum-likelihood analysis of the motion expected for a massive object within the observed Galactic center stellar cluster indicates that Sgr A* contains more than about 10% of the approximately 4 x 10^6 Msun deduced from stellar orbits. The intrinsic size of Sgr A*, as measured by several investigators, is less than 1 AU, and the implied mass density of ~10^22 Msun/pc^3 is within about three orders of magnitude of a comparable super-massive black hole within its Schwarzschild radius. Our observations provide the first direct evidence that a compact radiative source at the center of a galaxy contains of order 10^6 Msun and provides overwhelming evidence that it is in the form of a super-massive black hole. Finally, the existence of "intermediate mass" black holes more massive than ~10^4 Msun between roughly 10^3 and 10^5 AU from Sgr A* are excluded.

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References
How later papers used it

155 later papers cite it

Evidence: substantial. 151 of the citing papers share no author with it, and 120 of those carry a confident label from Pith's citation classifier.

Pith read 19 of the 185 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Uses its data or values 14 of 118 papers with this label
How the literature uses it

25 arXiv papers cite this in 31 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 9 sentences without a confident label

Uses its method or tool 1 paper
  • In each set of observations, we included several “geodetic blocks,” where we observed 12-15 bright sources from the International Celestial Reference Frame (ICRF) list of sources [ref] over a period of $∼$45 minutes to measure the tropospheric zenith delay and clock offsets at each antenna [ref] .

    VLBI Observations of the Nearby Type IIb Supernova 2011dh · VLBI Observations · 0.89

Uses its data or values 17 papers
  • To ensure consistency between the $(X,Y,Z)$ Cartesian system and the Galactocentric cylindrical system $(R,Θ,Z)$, Fig. [ref], we adopt the Solar distance from the Galactic centre of $R_⊙= 8.122 kpc$ obtained by [ref] , and the Solar velocity components $(U_⊙, V_⊙, W_⊙) = (11.1, 245.8, 7.8) km s^-1$ [ref] .

    Galaxy rotation curve based on RGB stars from the Gaia DR3 catalogue · Coordinate Systems · 1.00

  • We adopt the recent determinations of the galactic parameters ($R_0=8.122 ±0.031 kpc$ [ref] , the peculiar motion of the Sun in the tangential direction $V_⊙=12.24 ±0.47 km/s$ [ref] ; $Ω_g, ⊙ = 30.24±0.12$ km/s/kpc [ref] , and the local standard of rest $V_LSR=0±15 km/s$ [ref] ) and use standard error propagation to obtain a $V_0$ distribution described by the above-mentioned range, $V_0= 233±15$ km/s.

    A robust estimate of the Milky Way mass from rotation curve data · Dependence on the local circular velocity · 1.00

  • By removing the solar motion in longitude from the reflex of the motion of Sgr $A^*$ in longitude, the authors of [ref] find: Θ_0/R_0= A-B = 29.45 ±0.15 km s^-1 kpc^-1.

    A novel determination of the local dark matter density · Local circular velocity and Galactocentric distance · 1.00

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