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Perseus Cluster
Perseus Cluster
Perseus Cluster
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Perseus Cluster
Chandra X-ray Observatory observations of the central regions of the Perseus galaxy cluster. Image is 284 arcsec across. RA 03h 19m 47.60s Dec +41° 30' 37.00" in Perseus. Observation dates: 13 pointings between August 8, 2002 and October 20, 2004. Color code: Energy (Red 0.3–1.2 keV, Green 1.2-2 keV, Blue 2–7 keV). Instrument: ACIS.
Observation data (Epoch J2000)
ConstellationPerseus
Right ascension03hh 18m [1]
Declination+41° 30′[1]
Brightest memberNGC 1275
Number of galaxies>1000[1]
Richness class2[2]
Bautz–Morgan classificationII-III[2]
Redshift0.01790 (5 366 km/s)[1]
Distance73.6 Mpc (240.05 Mly) h−1
0.705[1]
X-ray flux9.1×10−11 erg s−1 cm−2 (2–10 keV)[1]
Other designations
Abell 426,[1] NGC 1275 Cluster,[1] LGG 88

The Perseus Cluster (Abell 426) is a cluster of galaxies in the constellation Perseus. It has a recession speed of 5,366 km/s and a diameter of 863′.[1] It is one of the most massive objects in the known universe, containing thousands of galaxies immersed in a vast cloud of multimillion-degree gas.

X-radiation from the cluster

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The Perseus galaxy cluster is the brightest cluster in the sky when observed in the X-ray band.[3]

The cluster contains the radio source 3C 84 that is currently blowing bubbles of relativistic plasma into the core of the cluster. These are seen as holes in an X-ray image of the cluster, as they push away the X-ray emitting gas. They are known as radio bubbles, because they appear as emitters of radio waves due to the relativistic particles in the bubble. The galaxy NGC 1275 is located at the centre of the cluster, where the X-ray emission is brightest.

The first detection of X-ray emission from the Perseus Cluster (astronomical designation Per XR-1) occurred during an Aerobee rocket flight on March 1, 1970. The X-ray source may be associated with NGC 1275 (Per A, 3C 84), and was reported in 1971.[4] If the source is NGC 1275, then Lx is about 4 x 1045 ergs/s.[4] More detailed observations from Uhuru confirmed the earlier detection and its source within the Perseus cluster.[5]

Perseus galaxy cluster's Cosmic music note

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In 2003, a team of astronomers led by Andrew Fabian at Cambridge University discovered one of the deepest notes ever detected, after 53 hours of Chandra observations.[6] No human will actually hear the note, because its time period between oscillations is 9.6 million years, which is 57 octaves below the keys in the middle of a piano.[6] The sound waves appear to be generated by the inflation of bubbles of relativistic plasma by the central active galactic nucleus in NGC 1275. The bubbles are visible as ripples in the X-ray band since the X-ray brightness of the intracluster medium that fills the cluster is strongly dependent on the density of the plasma. In May 2022, NASA reported the sonification (converting astronomical data associated with pressure waves into sound) of the black hole at the center of the Perseus galaxy cluster.[7][8]

A similar case also happens in the nearby Virgo Cluster, generated by an even larger supermassive black hole in the galaxy Messier 87, also detected by Chandra. Like the former, no human will hear the note. The tone is variable, and even lower than those generated by NGC 1275, from 56 octaves below middle C on minor eruptions, to as low as 59 octaves below middle C on major eruptions.[9]

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  • Euclid space telescope view of the Perseus Cluster. The image shows 1000 galaxies belonging to the cluster, and more than 100000 additional galaxies further away in the background
    Euclid space telescope view of the Perseus Cluster. The image shows 1000 galaxies belonging to the cluster, and more than 100000 additional galaxies further away in the background
  • Perseus Cluster photographed with amateur equipment
    Perseus Cluster photographed with amateur equipment
  • Perseus Cluster (Chandra X-ray).
    Perseus Cluster (Chandra X-ray).
  • Turbulence may prevent galaxy clusters from cooling (Chandra X-ray).
    Turbulence may prevent galaxy clusters from cooling (Chandra X-ray).
  • Composite view of NGC 1275 and the center of the Perseus Cluster (VLA-Radio, Chandra-X-ray, Hubble-Visible, SDSS-Infrared)
    Composite view of NGC 1275 and the center of the Perseus Cluster (VLA-Radio, Chandra-X-ray, Hubble-Visible, SDSS-Infrared)

See also

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References

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Perseus Cluster

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from Grokipedia
The Perseus Cluster, also known as Abell 426, is a massive galaxy cluster located approximately 250 million light-years from Earth in the constellation Perseus, containing thousands of galaxies bound by gravity within a vast cloud of hot intracluster gas. At its center lies the active galaxy NGC 1275, which harbors a supermassive black hole that drives powerful outflows and jets, contributing to the cluster's dynamic structure. With a total mass exceeding 660 trillion times that of the Sun, it ranks among the most massive nearby galaxy clusters and is a key laboratory for studying dark matter, galaxy evolution, and intracluster medium processes. This cluster, part of the larger Pisces-Perseus supercluster, spans about 11.6 million light-years across and exhibits one of the most luminous emissions in the sky due to its multimillion-degree gas heated by and feedback from the central . Notable features include enormous cavities or "bubbles" in the gas, carved by relativistic jets from , and pressure waves—effectively sound waves at frequencies far below human hearing—that propagate through the medium, offering insights into energy transport in clusters. Observations across wavelengths, from radio to , reveal its role in cosmic , with the cluster's of around 5,366 km/s indicating its via the Hubble flow.

Overview

Discovery and historical observations

The Perseus Cluster, cataloged optically as Abell 426, was first identified in 1958 by George O. Abell through a systematic survey of rich galaxy clusters on the Society-Palomar Observatory Sky Survey plates. Abell's catalog highlighted Abell 426 as a prominent concentration of galaxies in the constellation Perseus, though its full significance as a massive cluster became apparent only with later multiwavelength observations. The cluster's X-ray emission was detected for the first time on March 1, 1970, during an rocket flight equipped with proportional counters launched from . This serendipitous discovery, reported by Fritz et al., identified a strong source (designated Per XR-1) centered near the galaxy , marking the initial evidence of hot intracluster gas in the Perseus Cluster. Subsequent confirmation came from the Uhuru satellite, launched in 1970, which in 1972 observations revealed the source as extended and the brightest -emitting cluster in the sky, with emission spanning several arcminutes and associated with the cluster's core. These Uhuru data, analyzed by Forman et al., demonstrated that the luminosity originated from diffuse hot plasma rather than solely the central . Advancing into the late 1970s, the Einstein Observatory (launched 1978) provided the first high-resolution X-ray images of the Perseus Cluster in 1979, resolving the emission peak around —the central galaxy hosting the radio source 3C 84—and hinting at cooling gas in the core through spectral analysis with its Solid State Spectrometer. The 1990s brought detailed mapping with the ROSAT satellite (1990–1999), whose Position Sensitive Proportional Counter and High-Resolution Imager observations in the early 1990s uncovered an extensive X-ray halo extending over 1.3 degrees, revealing substructure in the and confirming the cluster's role as a prototype for cooling-flow systems. Böhringer et al.'s 1993 ROSAT study emphasized the halo's symmetry and brightness, attributing it to thermal emission from a massive hot gas envelope. A pivotal milestone occurred in 2003 with a deep exposure of nearly 200 kiloseconds on the cluster core, led by Fabian et al., which imaged unprecedented details including outward-propagating shock fronts approximately 30 kpc from and concentric "ripples" in the extending to 50 kpc. These features, collected using Chandra's Advanced CCD Imaging Spectrometer, suggested dynamic interactions such as sound waves generated by recurrent outbursts from the central , providing the first direct evidence of active feedback mechanisms regulating the . This observation built on the timeline of major telescopes: Uhuru for initial detection (1970–1973), Einstein for imaging (1978–1981), ROSAT for halo mapping (1990s), and for high-resolution dynamics (2000s onward).

Location and basic parameters

The Perseus Cluster lies in the constellation Perseus, with equatorial coordinates of right ascension 03h 18m 50.3s and declination +41° 30′ 08″ (J2000 epoch). These coordinates mark the central position as defined in the Abell catalog for this rich cluster of galaxies. The cluster spans an angular diameter of 863 arcminutes, reflecting its extensive apparent size on the sky due to its irregular morphology and proximity. It is characterized by a richness class of 2, indicating a substantial population of galaxies within the standard magnitude limits for cluster classification, and a Bautz–Morgan classification of II-III, which denotes an intermediate level of dominance by the brightest central galaxies. Over 1,000 have been identified as members, contributing to its status as one of the richer nearby clusters. Overall, the Perseus Cluster exhibits a rich, irregular structure with a prominent bright core centered on the dominant galaxy NGC 1275. At an estimated distance of 73.6 Mpc, it provides a key nearby laboratory for studying cluster dynamics.

Physical properties

Mass and size

The Perseus Cluster possesses a total mass of (8.6 \pm 0.9) \times 10^{14} solar masses within r_{200}, derived from analyses of X-ray gas dynamics under the assumption of hydrostatic equilibrium and corroborated by weak gravitational lensing measurements of the cluster's mass profile. These methods reveal a gravitationally bound system dominated by dark matter, with the intracluster medium and galaxies contributing lesser fractions to the overall mass budget. The cluster's dark matter component accounts for about 85% of the total mass, as inferred from comparisons between dynamical, X-ray, and luminous matter distributions. Recent Euclid observations (as of May 2025) confirm this mass estimate within r_{200} = 1.96 Mpc. The spatial structure of the Perseus Cluster is defined by a core radius of about 200 kpc, marking the scale over which the intracluster gas density profile flattens in the central regions, and an r_{200} of 1.96 Mpc, encompassing the volume where the mean overdensity relative to the critical density is 200. These dimensions highlight the cluster's extended halo, with the core exhibiting enhanced density due to cooling processes near the central galaxy, while the r_{200} boundary delineates the transition to infalling material. Dynamical estimates of the cluster's mass further support these findings through observations of member motions. The line-of-sight velocity dispersion of galaxies is approximately 1170 km/s, reflecting the depth of the well. Applying the provides an independent mass calculation, assuming the cluster is in approximate dynamical equilibrium: M=3σ2RGM = \frac{3 \sigma^2 R}{G} where σ\sigma is the velocity dispersion, RR is the virial radius, and GG is the . Substituting σ≈1170\sigma \approx 1170 km/s and R≈1.96R \approx 1.96 Mpc into this relation yields a estimate on the order of 101510^{15} solar masses, aligning closely with and lensing results and underscoring the reliability of these complementary approaches. Among nearby clusters at redshifts z<0.1z < 0.1, the Perseus Cluster ranks as one of the most massive, its scale and binding energy influencing large-scale structure formation in the local cosmic web. This prominence makes it a key laboratory for studying gravitational dynamics in massive systems.

Redshift and distance

The Perseus Cluster exhibits a spectroscopic redshift of z=0.01790±0.00016z = 0.01790 \pm 0.00016, measured from optical spectra of numerous member galaxies, providing a precise indicator of its recession due to the expansion of the universe. This redshift corresponds to a heliocentric recession velocity of 5258 km/s, as determined from recent spectroscopic surveys. The distance to the cluster is derived from this redshift using in the form v=H0dv = H_0 d, with the Hubble constant H0≈70H_0 \approx 70 km/s/Mpc, yielding a luminosity distance of approximately 75 Mpc (about 245 million light-years). More recent Euclid observations place it at 72 Mpc (as of May 2025). More precisely, the distance accounts for the standard Λ\LambdaCDM cosmological model with parameters Ωm=0.3\Omega_m = 0.3 and ΩΛ=0.7\Omega_\Lambda = 0.7. The comoving distance DcD_c is given by the line-of-sight integral Dc=∫0zc dz′H(z′),D_c = \int_0^z \frac{c \, dz'}{H(z')}, where H(z′)=H0Ωm(1+z′)3+ΩΛH(z') = H_0 \sqrt{\Omega_m (1 + z')^3 + \Omega_\Lambda}
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