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Messier 61
Messier 61
Messier 61
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Messier 61[1]
M61 imaged by the Hubble Space Telescope on April 28, 2014[2]
Observation data (J2000 epoch)
ConstellationVirgo
Right ascension12h 21m 54.9205s[3]
Declination+04° 28′ 25.631″[3]
Redshift0.005224±0.000007[3]
Heliocentric radial velocity1566±2 km/s[3]
Galactocentric velocity1483±4 km/s[3]
Distance52.5 ± 2.3 Mly (16.10 ± 0.71 Mpc)
Apparent magnitude (V)9.7[4]
Characteristics
TypeSAB(rs)bc,[3] HIISy2[3]
Size~92,300 ly (28.30 kpc) (estimated)[3]
Apparent size (V)6.5′ × 5.8′[3]
Other designations
HOLM 379A, IRAS 12194+0444, NGC 4303, UGC 7420, MCG +01-32-022, PGC 40001, CGCG 042-045[3]
References: SIMBAD: Search M61

Messier 61 (also known as M61, NGC 4303, or the Swelling Spiral Galaxy) is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was first discovered by Barnaba Oriani on May 5, 1779, six days before Charles Messier discovered the same galaxy. Messier had observed it on the same night as Oriani but had mistaken it for a comet.[5] Its distance has been estimated to be 45.61 million light years from the Milky Way Galaxy. It is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.[6]

Properties

[edit]

M61 is one of the largest members of Virgo Cluster, and belongs to a smaller subgroup known as the S Cloud.[7][8] The morphological classification of SAB(rs)bc[3] indicates a weakly-barred spiral (SAB) with the suggestion of a ring structure (rs) and moderate to loosely wound spiral arms.[9] It has an active galactic nucleus[10] and is classified as a starburst galaxy containing a massive nuclear star cluster with an estimated mass of 1 million solar masses (M☉) and an age of 4 million years,[11] as well as a central candidate supermassive black hole weighing around 5 million M☉.[12] It cohabits with an older massive star cluster as well as a likely older starburst.[11] Evidence of significant star formation and active bright nebulae appears across M61's disk.[13] Unlike most late-type spiral galaxies within the Virgo Cluster, M61 shows an unusual abundance of neutral hydrogen (H I).[14]

Supernovae

[edit]

Eight supernovae have been observed in M61, making it one of the most prodigious galaxies for such cataclysmic events.[15][16][5] These include:

[edit]
  • M61 (with NGC 4301 in upper left) imaged by the Vera C. Rubin Observatory
    M61 (with NGC 4301 in upper left) imaged by the Vera C. Rubin Observatory
  • Spiral galaxy Messier 61 is aligned face-on towards Earth.[35]
    Spiral galaxy Messier 61 is aligned face-on towards Earth.[35]
  • Messier 61 image using data from Hubble's Wide Field Camera 2
    Messier 61 image using data from Hubble's Wide Field Camera 2
  • Amateur Image of Messier 61 Showing Supernova 2008in on April 16, 2009
    Amateur Image of Messier 61 Showing Supernova 2008in on April 16, 2009
  • Infrared image of M61 taken by the Spitzer Space Telescope
    Infrared image of M61 taken by the Spitzer Space Telescope
  • Messier 61 with SN2020jfo (Supernova) observed on May 15, 2020
    Messier 61 with SN2020jfo (Supernova) observed on May 15, 2020
  • M61 galaxy image that incorporates data from not only Hubble, but also the FORS camera at the European Southern Observatory’s Very Large Telescope
    M61 galaxy image that incorporates data from not only Hubble, but also the FORS camera at the European Southern Observatory’s Very Large Telescope

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Messier 61

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Messier 61 (M61), also known as NGC 4303, is a and prominent member of the , located approximately 52.5 million light-years from in the constellation Virgo. It spans about 100,000 light-years in diameter, comparable in size to the , and exhibits an of 9.7, making it visible with moderate telescopes under dark skies. As a , M61 features intense rates driven by gravitational interactions, particularly in its prominent spiral arms, which glow with bright blue regions of young, massive stars. This activity is fueled by an at its core, powered by a , and has led to the observation of eight supernovae as of 2025—the highest number recorded in any . In 2025, the revealed a prominent stellar stream extending from M61, indicating past galactic interactions. Discovered independently in 1779 by Italian astronomer Barnaba Oriani and French astronomer (who initially mistook it for a ), M61 has been extensively studied by telescopes like Hubble, revealing intricate dust lanes and a face-on orientation that highlights its structure.

Discovery and Observation

Discovery History

Messier 61 was first discovered on May 5, 1779, by the Italian astronomer Barnaba Oriani while he was tracking the path of C/1779 A1 (Bode). Oriani described the object as a very faint, nebulous patch resembling a without a tail, leading him to initially classify it as such. On the same night, French astronomer independently observed the object during his own comet search but suspected it might be the comet itself or a related . After further checks, Messier confirmed its stationary nature and included it in his famous catalog on May 11, 1779, as the 61st entry (M61), marking it as a potential comet-like to aid other observers in distinguishing true comets from fixed deep-sky objects. The object drew further attention from , who observed it on April 17, 1786, and cataloged it as his nebula H I.139, noting its very bright, very large, and irregularly round appearance with a gradually brighter middle. In 1888, John Louis Emil Dreyer formally designated it NGC 4303 in the , compiling positions and descriptions from earlier observers including Herschel. Early catalogers faced challenges distinguishing M61 from nearby objects like in the crowded Virgo region, contributing to occasional positional mix-ups in historical records.

Observational Details

Messier 61 is located at 12h 21m 54.9s and +04° 28′ 26″ in the J2000 epoch. Its apparent visual magnitude of 9.7 renders it accessible to observers using medium-sized amateur telescopes, such as those with apertures of 100–150 mm, particularly under away from urban light pollution. From the , Messier 61 is best observed during spring, typically from to , when it reaches its highest point in the evening sky near the border between the constellations Virgo and . To locate it, start from the bright stars 16 Virginis (magnitude 5.0) and 17 Virginis (magnitude 5.6), then move approximately 1.5° north, where the appears as a faint, mottled patch. Observing Messier 61 presents challenges due to its proximity to these brighter foreground stars, which can overwhelm its low , as well as interference from in suburban or urban environments. Employing —shifting the gaze slightly away from the direct line to the object—can enhance visibility of its faint disk and spiral arms, especially at magnifications of 70–150×. Beyond the Messier catalog, it is designated NGC 4303 in the , a standard reference for deep-sky objects. Under suitable conditions, its barred spiral structure may become discernible as a subtle elongation in larger instruments.

Physical Characteristics

Morphology and Structure

Messier 61, also known as NGC 4303, is classified as an according to the de Vaucouleurs revised classification system, characterized by a weak bar and loosely wound spiral arms that suggest an inner ring-like structure formed by the arm segments. This morphology places it among intermediate spiral galaxies with moderate arm openness, where the spiral pattern emerges gradually from the ends of the central bar. At its core, the galaxy features a prominent central bar measuring approximately 2.5 kiloparsecs in length, which channels toward the nucleus and is surrounded by a bright, compact nucleus indicative of active processes such as a low-luminosity or concentrated . Extending outward from the bar are two main spiral arms rich in structural complexity, including dense dust lanes that trace the spiral pattern and delineate regions of obscuration, as well as numerous H II regions marking sites of ongoing . These arms contribute to the galaxy's overall disk-like appearance, with the dust and ionized gas highlighting the dynamic interplay between the bar and the spiral structure. Observed at a low inclination angle of approximately 27 degrees, Messier 61 presents a nearly face-on view to , allowing for clear resolution of its internal features with minimal distortion from projection effects. The disk spans an overall diameter of about 100,000 light-years, comparable in scale to the , encompassing the bar, nucleus, and extended spiral components within a well-defined .

Size, Distance, and Composition

Messier 61 lies at a distance of approximately 55 million light-years (16.8 Mpc) from , consistent with measurements for the . This distance has been supported by fluctuation measurements applied to early-type galaxies in the , providing calibration for spiral members like Messier 61. The galaxy spans an of about 6.5 arcminutes, translating to a physical of roughly 100,000 light-years at this distance. Its total dynamical mass is estimated at around 101110^{11} solar masses, derived from rotation curve modeling that accounts for the contributions from stellar, gaseous, and components within the optical extent. The in Messier 61 features older, yellow stars predominantly in the central bulge and bar, indicative of evolved, low-mass stars formed billions of years ago, while the spiral arms host younger, blue stars associated with recent episodes. The includes dense molecular clouds traced by CO emissions, particularly concentrated along the bar and in the arms, alongside regions of ionized hydrogen gas revealed through Hα emission from H II regions powered by young, massive stars. in Messier 61 is comparable to that of the , reflecting chemical evolution patterns typical of spiral disks.

Virgo Cluster Context

Position and Membership

Messier 61 is situated in the , the nearest rich cluster of galaxies to the Local Group, located at a distance of approximately 55 million light-years (17 Mpc) from . This cluster, comprising over 1,300 member galaxies, spans an angular extent of about 5 by 3 degrees on the sky in the constellation Virgo. Messier 61 occupies a position in the southern portion of this structure, roughly 8 degrees south of the central giant M87 (Virgo A), which marks the dynamical core of the cluster. Its membership in the is confirmed by its heliocentric of 1,566 ± 2 km/s, derived from spectroscopic observations, which aligns with the cluster's velocity distribution and indicates motion consistent with infall toward the Virgo A core. This velocity places Messier 61 within the infalling population of galaxies approaching the cluster center, contributing to its classification as a bona fide member despite its peripheral location. Messier 61 lies in proximity to several prominent cluster members, including the elliptical galaxies M60 (angular separation of about 7 degrees) and (approximately 8.5 degrees), as well as the central M87, highlighting its integration into the cluster's southern extension. As a foreground element in this region—evidenced by its relatively higher relative to the cluster mean—it experiences the dynamical influences of the cluster environment, such as gravitational interactions and effects that shape galaxy evolution.

Galactic Interactions

Messier 61, situated on the periphery of the approximately 8.2 degrees from the central galaxy M87, is subject to gravitational interactions with neighboring galaxies that have left subtle imprints on its structure. Observations reveal evidence of past close encounters, particularly with the nearby companions NGC 4292 (projected distance of about 61 kpc) and NGC 4303A (7.5 arcminutes northwest), which likely induced gravitational perturbations. These interactions are inferred to have caused distortions in the galaxy's spiral arms, manifesting as a boomerang-like asymmetry in the eastern arm of the outer disk. In 2025, a stellar stream was discovered around Messier 61 using the , providing further evidence of tidal interactions with a . In addition to tidal effects, Messier 61 experiences from the hot (ICM) of the , which influences the distribution of its atomic and molecular gas. As a face-on spiral at the cluster's outskirts, it shows no severe gas deficiency, with H I observations indicating only moderate environmental disturbance rather than active stripping tails or plumes typical of more central galaxies. This process is quantified in models where the exerted on the galaxy's disk is below the critical threshold for significant , preserving much of its gas reservoir while subtly altering outer gas flows. The galaxy's prominent bar structure may owe its formation in part to minor mergers with dwarf satellites, as confirmed by the detection of Hα-emitting satellite galaxies in its vicinity. Such accretions can drive non-axisymmetric instabilities, contributing to bar development without major morphological disruption. Simulations of Virgo Cluster member orbits demonstrate that spirals like Messier 61 follow eccentric paths that accumulate tidal distortions, enhancing asymmetries in the outer disk and perturbing the stellar distribution.

Stellar Activity and Evolution

Star Formation and Starburst Features

Messier 61 (NGC 4303) is classified as a , exhibiting exceptionally intense that rapidly consumes its gas reserves on astronomical timescales. This activity is concentrated in the galaxy's prominent spiral arms and circumnuclear region, where gravitational dynamics funnel molecular gas into dense concentrations conducive to collapse and new star birth. The galaxy's star formation rate is estimated at 6.0 ± 0.3 solar masses per year, a value elevated relative to typical spirals of comparable size (~100,000 light-years across) and indicative of the bursty nature driving its evolution. This rate is derived from multiwavelength spectral energy distribution fitting, incorporating ultraviolet to submillimeter data that highlight the dominance of young, massive stars. Numerous H II regions, ionized by these hot O and B-type stars, dot the spiral arms, while clusters of young stars are prominently detected in ultraviolet continuum imaging, revealing ongoing massive star formation not visible in optical or near-infrared wavelengths. Infrared observations further trace the heated dust associated with these embedded clusters and H II regions, underscoring the galaxy's high output of ultraviolet radiation from recent stellar generations. Fueling this starburst are substantial reservoirs of molecular gas, with a total H₂ mass of (1.75 ± 0.32) × 10⁸ solar masses in the central kiloparsec, including dense phases traced by lines such as HCN, HNC, HCO⁺, and C₂H. These have been mapped at high resolution using the Atacama Large Millimeter/submillimeter (ALMA) at 3 mm wavelengths, showing concentrations along the bar and spiral structures that correlate with star-forming sites. Feedback mechanisms play a key role in regulating this process: the low-luminosity contributes marginally (~20% of the total energy output) through radiation and potential outflows from its dusty , while supernovae from the prolific young drive gas and expulsion, limiting further collapse and maintaining the burst's episodic character.

Supernovae Events

Messier 61 has hosted at least eight confirmed supernovae since 1926, the highest number recorded in any Messier catalog galaxy, corresponding to an average rate of approximately one event every 12 years. This elevated rate is linked to the galaxy's high activity, which produces massive stars that end their lives in core-collapse explosions. The documented supernovae in Messier 61, along with their types and discovery details, are summarized in the following table:
DesignationTypeDiscovery DateDiscoverer(s)Peak MagnitudeReference
SN 1926AII1926 May 9Max Wolf, K. W. Reinmuth~14IAUC 111
SN 1961III1961 June 3Milton Humason~13IAUC 1761
SN 1964FII1964 June 30Leonida Rosino~14IAUC 1868
SN 1999gnII1999 Dec 17Alessandro Dimai~16IAUC 7335
SN 2006ovII-P2006 Nov 24Koichi Itagaki~14.9CBET 1040
SN 2008inII2008 Dec 26Koichi Itagaki~14.9CBET 1636
SN 2014dtIax2014 Oct 29Koichi Itagaki~13.6CBET 4011
SN 2020jfoIIP2020 May 6Zwicky Transient Facility~14.3arXiv:2202.09412
These events span both core-collapse Type II supernovae, arising from the explosions of massive stars, and rarer Type I variants from disruptions. Most observations have relied on ground-based telescopes, including those contributing to Circulars (IAUC) and Central Bureau Electronic Telegrams (CBET), which provided initial detections, light curves, and spectroscopic classifications. The has captured detailed imaging and spectra for several recent events, such as SN 2014dt and SN 2020jfo, enabling precise measurements of expansion velocities and ejecta composition. Type I supernovae in Messier 61, including the Iax subtype SN 2014dt, have been instrumental in distance determinations due to their use as standardized candles after corrections for shapes and colors. These measurements help refine the distance to the , anchoring the at ~16.7 Mpc for Messier 61. Studies of core-collapse events like SN 2006ov have also probed progenitor masses and environments through pre-explosion Hubble images, revealing origins. The remnant of SN 1999gn, a Type II event, has been examined for its nebular emission, offering insights into nucleosynthesis yields of elements produced in core-collapse explosions, such as oxygen and heavier metals from explosive nucleosynthesis.

Recent Discoveries

Tidal Tail Observation

In November 2025, astronomers announced the discovery of a prominent stellar stream, often referred to as a tidal tail, extending from Messier 61 using early images from the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). The finding was detailed in a Research Note published on November 7, 2025, based on the observatory's Virgo First Look imaging campaign conducted in October 2025. This feature had evaded detection in prior observations despite extensive study of the galaxy, highlighting the sensitivity of the Rubin's 8.4-meter mirror and its wide-field camera to low-surface-brightness structures. The tidal tail spans approximately 50 kiloparsecs, or about 163,000 light-years, making it one of the longest such streams identified to date. It consists of stripped stars with a total of roughly 2×1082 \times 10^8 solar masses and a color (g - z ≈ 1.0), indicative of an older population likely originating from a disrupted . The stream's faint , around 28 magnitudes per square arcsecond in the g-band, required advanced image processing to subtract foreground and reveal its curved morphology. This curvature and extent suggest a past gravitational interaction with a dwarf satellite, potentially triggering enhanced in Messier 61. This observation parallels similar tidal features seen in other Virgo Cluster galaxies, such as the extensive streams around M87, underscoring the prevalence of merger remnants in dense environments. The discovery exemplifies the Rubin's capability to uncover diffuse stellar structures, with expectations for many more such detections in the full LSST survey.

Implications for Galaxy History

The discovery of a stellar stream extending approximately 50 kpc from Messier 61 provides direct evidence of a past accretion event involving a dwarf with a of about 2×108M⊙2 \times 10^8 M_\odot, indicating that this barred spiral has undergone dynamical interactions that challenge models assuming isolated evolution. Such accretion events, common in dense cluster environments like the , demonstrate how Messier 61's history deviates from quiescent spiral development, instead reflecting a pattern of ongoing material infall that reshapes its structure over gigayears. In the Virgo Cluster, frequent high-speed encounters—termed galaxy harassment—facilitate multiple minor merger-like interactions that accelerate evolutionary processes in spirals like Messier 61, leading to the stripping of outer gas reservoirs and the enhancement of central dynamical features. These repeated interactions link to heightened rates, as gravitational perturbations from accreted dwarfs can drive gas inflows toward the nucleus, fueling bursts that have been observed in Messier 61 and potentially strengthening its prominent bar over billions of years through angular momentum transfer and disk instabilities. Looking ahead, the ongoing in the suggests Messier 61 faces continued tidal stripping, which could diminish its spiral arms and deplete , progressively transforming it into a over the next few billion years—a fate consistent with the observed morphological mix in cluster environments. This evolutionary pathway underscores broader models of cluster galaxy , where cumulative minor interactions, rather than major mergers, dominate the transformation of late-type spirals into early-type systems, providing a template for understanding hierarchical assembly in dense cosmic structures.

References

  1. https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-61/
  2. https://science.nasa.gov/missions/hubble/messier-61-looks-straight-into-hubbles-camera/
  3. https://www.esa.int/ESA_Multimedia/Images/2014/04/A_hungry_starburst_galaxy
  4. https://bigthink.com/starts-with-a-bang/stream-stars-escaping-galaxy/
  5. https://www.messier-objects.com/messier-61/
  6. https://esahubble.org/images/potw1417a/
  7. http://www.messier.seds.org/m/m061.html
  8. http://www.messier.seds.org/Mdes/dm061.html
  9. https://cseligman.com/text/atlas/ngc43.htm
  10. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Messier+61
  11. https://www.astronomy.com/observing/101-must-see-cosmic-objects-m61/
  12. https://www.universetoday.com/articles/messier-61
  13. https://www.astronomy.com/science/spiral-galaxy-m61-the-silver-needle-galaxy-ngc-4244-and-spiral-galaxy-ngc-3998/
  14. https://www.go-astronomy.com/messier.php?Messier=M61
  15. https://www.aanda.org/articles/aa/pdf/2007/26/aa6784-06.pdf
  16. https://ned.ipac.caltech.edu/level5/Lynds/NGC4303.html
  17. https://arxiv.org/abs/astro-ph/0204133
  18. https://academic.oup.com/pasj/article/71/Supplement_1/S13/5420421
  19. https://academic.oup.com/mnras/article/482/4/4437/5162850
  20. http://www.messier.seds.org/xtra/supp/redshift.html
  21. https://arxiv.org/abs/2510.24836
  22. https://cdsarc.u-strasbg.fr/vizier/ftp/vizier/aa/papers/0360002/2300447.pdf
  23. https://www.aanda.org/articles/aa/full_html/2012/09/aa18871-12/aa18871-12.html
  24. https://arxiv.org/pdf/astro-ph/9511019
  25. https://academic.oup.com/mnras/article/479/4/4367/5040236
  26. https://academic.oup.com/mnras/article/410/4/2549/1007959
  27. https://science.nasa.gov/missions/hubble/hubble-view-a-hungry-starburst-galaxy/
  28. https://academic.oup.com/pasj/article/58/2/299/1515540
  29. https://arxiv.org/abs/2411.18723
  30. https://arxiv.org/abs/1212.4153
  31. https://arxiv.org/abs/2202.09412
  32. https://cosmicpursuits.com/2760/supernova-in-messier-61/
  33. http://www.cbat.eps.harvard.edu/IAUC/IAUC00000/00111.html
  34. http://www.cbat.eps.harvard.edu/IAUC/IAUC00000/01761.html
  35. http://www.cbat.eps.harvard.edu/IAUC/IAUC00000/01868.html
  36. http://www.cbat.eps.harvard.edu/iauc/07300/07335.html
  37. https://www.cbat.eps.harvard.edu/CBET/0001/CBET001040.txt
  38. https://www.cbat.eps.harvard.edu/cbet/1636.html
  39. https://www.cbat.eps.harvard.edu/cbet/4011.html
  40. https://arxiv.org/abs/1412.1088
  41. https://arxiv.org/abs/astro-ph/0701049
  42. https://theses.hal.science/tel-02018238v1/file/2018AZUR4101.pdf
  43. https://www.scientificamerican.com/article/rubin-observatory-discovers-surprise-tail-on-iconic-galaxy/
  44. https://www.forbes.com/sites/brucedorminey/2025/11/07/rubin-observatory-finds-massive-stellar-stream-around-spiral-galaxy-m61/
  45. https://arxiv.org/abs/astro-ph/9510034
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