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A ring galaxy is a galaxy with a circle like appearance, Hoag's object discovered by Art Hoag in 1950 is an example of a ring galaxy.The ring contains many massive, relatively young blue stars which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that the ring galaxies were formed when a smaller galaxy passed through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.


Hoag's Object is a non typical galaxy of the type known as a ring galaxy. The galaxy is named after Arthur Hoag who discovered it in 1950 and identified it as either a planetary nebula or a peculiar galaxy with eight billion stars. 
A nera perfect ring of young hot blue stars circles the old yellow nucleus of this ring galaxy c. 600 million light years away in the constellation Serpens. The diameter of the 6 arcsecond inner core of the galaxy is about 17±0.7 kly (5.3±0.2 kpc) while the surrounding ring has an inner 28″ diameter of 75±3 kly (24.8±1.1 kpc) and an outer 45″ diameter of 121±4 kly (39.9±1.7 kpc), which is slightly larger than the Milky Way Galaxy. The gap separating the two stellar populations may contain some start clusters  that are almost too faint to see. As rare as this type of galaxy is, another more distant ring galaxy (SDSS J151713.93+213516.8) can be seen through Hoag's Object, between the nucleus and the outer ring of the galaxy, at roughly the one o'clock position.


Enlarged image where the ring galaxy SDSS J151713 can be observed. 93 + 213516.8

Many of the details of the galaxy remain a mystery, foremost of which is how it formed. So-called "classic" ring galaxies are generally formed by the collision of a small galaxy with a larger disk-shaped galaxy. This collision produces a density wave in the disk that leads to a characteristic ring-like appearance. Such an event would have happened at least 2–3 billion years in the past, and may have resembled the processes that form polar ring galaxies. However, there is no sign of any second galaxy that would have acted as the "bullet", and the likely older core of Hoag's Object has a very low velocity relative to the ring, making the typical formation hypothesis quite unlikely.A few other galaxies share the primary characteristics of Hoag's Object, including a bright detached ring of stars, but their centers are elongated or barred, and they may exhibit some spiral structure. While none match Hoag's Object in symmetry, this handful of galaxies are known to some as Hoag-type galaxies.


The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a spiral galaxy in the constellation Virgo located 9.55 MPC  (31,100,000 ly) from Earth. The galaxy has a diameter of approximately 15kpc (50,000 light years), 30% the size of the Milky Way. It has a bright nucleus and an unusually large central bulge and a prominent dust lane in it's inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy, but the Spitzer space telescope found that the halo around the Sombrero Galaxy is larger and more massive than previously thought, indicative of a giant elliptical galaxy. 


NASA's Spitzer Space Telescope was launched in 2003 to study the universe in the infrared. It is the last mission of the NASA Great Observatories program, which saw four specialized telescopes (including the Hubble Space Telescope) launched between 1990 and 2003.

Original air date: Aug. 9 at 7 p.m. PT (10 p.m. ET, 0200 UTC) The Spitzer Space Telescope is one of NASA’s Great Observatories, designed to observe the universe in infrared light. Launched in 2003 with an expected lifetime of five years, Spitzer has succeeded beyond our wildest expectations. This talk will cover engineering feats and technical challenges, as well as recent science highlights. These include science Spitzer was not designed to do, such as the discovery and characterization of seven rocky, potentially habitable planets in the nearby TRAPPIST-1 system. Speaker: Sean Carey, Manager of the Spitzer Science Center, Caltech/IPAC

The goal of the Great Observatories is to observe the universe in distinct wavelengths of light. Spitzer focuses on the infrared band, which normally represents heat radiation from objects. The other observatories looked at visible light (Hubble, still operational), gamma-rays (Compton Gamma-Ray Observatory, no longer operational) and X-rays (the Chandra X-Ray Observatory, still operational.)
"Spitzer's highly sensitive instruments allow scientists to peer into cosmic regions that are hidden from optical telescopes, including dusty stellar nurseries, the centers of galaxies, and newly forming planetary systems," NASA wrote on the Spitzer website. "Spitzer's infrared eyes also allows astronomers see cooler objects in space, like failed stars (brown dwarfs), extrasolar planets, giant molecular clouds, and organic molecules that may hold the secret to life on other planets."


The Chandra X-Ray Observatory is a NASA telescope that looks at black holes, quasars, supernovas, and the like – all sources of high energy in the universe. It shows a side of the cosmos that is invisible to the human eye.After more than a decade in service, the observatory has helped scientists glimpse the universe in action. It has watched galaxies collide, observed a black hole with cosmic hurricane winds, and glimpsed a supernova turning itself inside out after an explosion. The observatory was launched on STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors. Chandra is an Earth satellite in a 64 hour orbit and its mission is ongoing as of 2018.

Lyman Spitzer 1940's.jpg

Above - Lyman Spitzer - Right - Pierre Mechain.

The telescope is named after Lyman Spitzer Jr, an astrophysicist who made major contributions in the areas of stellar dynamics, plasma physics, thermonuclear fusion and space astronomy, according to a NASA biography. Spitzer was the first person to propose the idea of placing a large telescope in space and was the driving force behind the development of the Hubble Space Telescope.


Pierre François André Méchain 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who with Charles Messier was a major contributor to the early study of deep sky objects and comets.

The galaxy has an apparent magnitude of +8.0, making it easily visible with amateur telescopes, and it is consicered by some authors to be the brightest galaxy within a radius of 10 megaparsecs of the Milky Way. Its large bulge, it's central supermassive black hole and it's dust lane all attract the attention of professional astronomers. The Sombrero Galaxy was discovered on May 11, 1781 by Pierre Mechain, who described the object in a May 1783 letter to J.Bernoulli that was later published in the Berliner Astronomisches Jahrbuch. 


Mizar and Alcor, the Sombrero Galaxy (M104), and elliptical galaxy M60

As noted above, this galaxy's most striking feature is the dust lane that crosses in front of the bulge of the galaxy. This dust lane is actually a symmetrical ring that encloses the bulge of the galaxy. Most of the cold atomic hydrogen gas and the dust lie within this ring. The ring might also contain most of the Sombrero Galaxy's cold molecular gas, although this is an inference based on observations with low resolution and weak detection's. Additional observations are needed to confirm that the Sombrero galaxy's molecular gas is constrained to the ring. Based on infrared spectroscopy the dust ring is the primary site of star formation within this galaxy.


The nucleus of the Sombrero galaxy is classified as a low ionization nuclear emission region (LINER). These are nuclear regions where ionized gas is present, but the ions are only weakly ionized (i.e. the atoms are missing relatively few electrons). The source of energy for ionizing the gas in LINERs has been debated extensively. Some LINER nuclei may be powered by hot, young stars found in star formation regions, whereas other LINER nuclei may be powered by active galactic nuclei (highly energetic regions that contain supermassive black holes). Infrared spectroscopy observations have demonstrated that the nucleus of the Sombrero Galaxy is probably devoid of any significant star formation activity. However, a supermassive black hole has been identified in the nucleus (as discussed in the subsection below), so this active galactic nucleus is probably the energy source that weakly ionizes the gas in the Sombrero Galaxy.


For the first time ever, astronomers at The University of New Mexico say they've been able to observe and measure the orbital motion between two supermassive black holes hundreds of millions of light years from Earth - a discovery more than a decade in the making. In early 2016, an international team of researchers, including a UNM alumnus, working on the LIGO project detected the existence of gravitational waves, confirming Albert Einstein's 100-year-old prediction and astonishing the scientific community. These gravitational waves were the result two stellar mass black holes (~30 solar mass) colliding in space within the Hubble time. Now, thanks to this latest research, scientists will be able to start to understand what leads up to the merger of supermassive black holes that creates ripples in the fabric of space-time and begin to learn more about the evolution of galaxies and the role these black holes play in it.


This image shows that celestial objects make dents in the fabric of space-time. The Earth, being 81 times more massive than its moon (right), induces a much greater curvature. According to general relativity, this curvature is what we perceive as gravity. 


Using the Very Long Baseline Array (VLBA), a system made up of 10 radio telescopes across the U.S. and operated in Socorro, N.M., researchers have been able to observe several frequencies of radio signals emitted by these supermassive black holes (SMBH). Over time, astronomers have essentially been able to plot their trajectory and confirm them as a visual binary system. In other words, they've observed these black holes in orbit with one another.
"When Dr. Taylor gave me this data I was at the very beginning of learning how to image and understand it," said Bansal. "And, as I learned there was data going back to 2003, we plotted it and determined they are orbiting one another. It's very exciting." For Taylor, the discovery is the result of more than 20 years of work and an incredible feat given the precision required to pull off these measurements.


An antenna for the Very Long Baseline Array (VLBA). The VLBA is a radio astronomy observatory antenna, composed of ten 82-foot collectors spread out across the USA from the Virgin Islands to Hawaii, working together to form a radio antenna 5,000 miles in diameter, thus forming a portion of the National Radio Astronomy Observatory. Information from this configuration is collected from each site and sent to the Science Operations Center at the New Mexico Institute of Mining and Technology, in Socorro. The VLBA observes at wavelengths of 28 cm to 3 mm (1.2 GHz to 96 GHz) in eight discrete bands plus two narrow sub-gigahertz bands, including the primary spectral lines that produce high-brightness maser emission. 

At roughly 750 million light years from Earth, the galaxy named 0402+379 and the supermassive black holes within it, are incredibly far away; but are also at the perfect distance from Earth and each other to be observed.

Bansal says these supermassive black holes have a combined mass of 15 billion times that of our sun, or 15 billion solar masses. The unbelievable size of these black holes means their orbital period is around 24,000 years, so while the team has been observing them for over a decade, they've yet to see even the slightest curvature in their orbit.


"If you imagine a snail on the recently-discovered Earth-like planet orbiting Proxima Centauri - 4.243 light years away - moving at 1 cm a second, that's the angular motion we're resolving here," said Roger W. Romani, professor of physics at Stanford University and member of the research team.
"What we've been able to do is a true technical achievement over this 12-year period using the VLBA to achieve sufficient resolution and precision in the astrometry to actually see the orbit happening," said Taylor. "It's a bit of triumph in technology to have been able to do this."
While the technical accomplishment of this discovery is truly amazing, Bansal and Taylor say the research could also teach us a lot about the universe, where galaxies come from and where they're going. "Supermassive black holes have a lot of influence on the stars around them and the growth and evolution of the galaxy," explained Taylor. "So, understanding more about them and what happens when they merge with one another could be important for our understanding for the universe."


The proponents of string theory seem to think they can provide a more elegant description of the Universe by adding additional dimensions. But some other theoreticians think they've found a way to view the Universe as having one less dimension. The work sprung out of a long argument with Stephen Hawking about the nature of black holes, which was eventually solved by the realization that the event horizon could act as a hologram, preserving information about the material that's gotten sucked inside. The same sort of math, it turns out, can actually describe any point in the Universe, meaning that the entire content Universe can be viewed as a giant hologram, one that resides on the surface of whatever two-dimensional shape will enclose it.


Stephen Hawking attempted to describe what happens to matter during its lifetime in a black hole. He suggested that, from the perspective of quantum mechanics, the information about the quantum state of a particle that enters a black hole goes with it. This isn't a problem until the black hole starts to boil away through what's now called Hawking radiation, which creates a separate particle outside the event horizon while destroying one inside. This process ensures that the matter that escapes the black hole has no connection to the quantum state of the material that had gotten sucked in. As a result, information is destroyed. And that causes a problem, as the panel described.


Susskind described just how counterintuitive this is. The holograms we're familiar with store an interference pattern that only becomes information we can interpret once light passes through them. On a micro-scale, related bits of information may be scattered far apart, and it's impossible to figure out what bit encodes what. And, when it comes to the event horizon, the bits are vanishingly small, on the level of the Planck scale (1.6 x 10-35 meters). These bits are so small, as 't Hooft noted, that you can store a staggering amount of information in a reasonable amount of space—enough to describe all the information that's been sucked into a black hole.


In the 1990s, a research group led by John Kormendy demonstrated that a supermassive black hole is present within the Sombrero Galaxy. Using spectroscopy data from both the CFHT and the Hubble Space Telescope  the group showed that the speed of revolution of the stars within the center of the galaxy could not be maintained unless a mass 1 billion times the mass of the Sun or 109 M☉, is present in the center. This is among the most massive black holes measured in any nearby galaxies.


The workstation screen in the above photo shows an unsharp-masked spectrum of the Sombrero Galaxy (NGC 4594) and the rotation curve implied by the S-shaped spectral lines. This rapid rotation and the observed steep velocity dispersion gradient are the signature of a billion-solar-mass black hole (see Kormendy et al. 1996, ApJL, 473, L91)

At radio and X-ray wavelengths, the nucleus is a strong source of synchrotron emission. Synchrotron emission is produced when high velocity electrons oscillate as they pass through regions with strong magnetic fields. This emission is quite common for active galactic nuclei. Although radio synchrotron emission may vary over time for some active galactic nuclei, the luminosity of the radio emission from the Sombrero Galaxy varies only 10–20%.


In 2006, two groups published measurements of the submillimeter radiation  from the nucleus of the Sombrero Galaxy at a wavelength of 850 um. This submillimeter emission was found not to originate from the thermal emission from dust (which is commonly seen at infrared and submillimeter wavelenghts, synchrotron emission (which is commonly seen at radio wavelenghts), bremsstrahlung emission from hot gas (which is uncommonly seen at millimeter wavelengths), or molecular gas (which commonly produces submillimeter spectral lines). The source of the submillimeter emission remains unidentified.


750 to 950 nm Wavelength Range, Large Field of View

The Sombrero Galaxy has a relatively large number of globular clusters, Observational studies of globular clusters in the Sombrero Galaxy have produced estimates of the population in the range of 1,200 to 2,000. The ratio of the number of globular clusters to the total luminosity of the galaxy is high compared to the Milky Way and similar galaxies with small bulges, but the ratio is comparable to other galaxies with large bulges. These results have been repeatedly used to demonstrate that the number of globular clusters in galaxies is thought to be related to the size of the galaxies' bulges. The surface density of the globular clusters generally follows the light profile of the bulge except for near the center of the galaxy.


We call it the ‘globular cluster opportunity,’” says Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics (CfA). “A globular cluster might be the first place in which intelligent life is identified in our galaxy. Sending a broadcast between the stars wouldn’t take any longer than a letter from the U.S. to Europe in the 18th century. “Interstellar travel would take less time too. The Voyager probes are 100 billion miles from Earth, or one-tenth as far as it would take to reach the closest star if we lived in a globular cluster. That means sending an interstellar probe is something a civilization at our technological level could do in a globular cluster,” she adds.


Globular star clusters are amazing in almost every way. They’re densely packed, holding a million stars in a ball only about 100 light-years across on average. They’re old, dating back almost to the birth of the Milky Way. And according to new research, they also could be extraordinarily good places to look for space-faring civilizations.

Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics (CfA)

The Milky Way hosts about 150 globular clusters, most of them orbiting in the galactic outskirts. They formed about 10 billion years ago on average. As a result, their stars contain fewer of the heavy elements needed to construct planets, since those elements (like iron and silicon) must be created in earlier generations of stars. Some scientists have argued that this makes globular cluster stars less likely to host planets. In fact, only one planet has been found in a globular cluster to date.  The Hubble image below shows 47 Tucanae – the second most luminous globular cluster in the Milky Way, after Omega Centauri.


The heart of the giant globular star cluster 47 Tucanae in the Hubble image at top left reveals the glow of 200,000 stars. The green box outlines the cluster’s crowded core, where Hubble spied a parade of young white dwarfs starting their slow-paced 40-million-year journey to the less populated suburbs. The stellar relics are too faint to be seen clearly in visible light, as shown in the Hubble image at top right. But in ultraviolet light the stars glow brightly because they are extremely hot, as shown in the image at bottom right. The green circles in the image outline the brightest of the young white dwarfs spied by Hubble. Image credit: NASA / ESA / H. Richer & J. Heyl, University of British Columbia / J. Mack, STScI / G. Piotto, University of Padova.

However, Di Stefano and her colleague Alak Ray of the Tata Institute of Fundamental Research in Mumbai, India, argue that this view is too pessimistic. Exoplanets have been found around stars only one-tenth as metal-rich as our sun. And while Jupiter-sized planets are found preferentially around stars containing higher levels of heavy elements, research finds that smaller, Earth-sized planets show no such preference.
“It’s premature to say there are no planets in globular clusters,” states Ray.


Another concern is that a globular cluster’s crowded environment would threaten any planets that do form. A neighboring star could wander too close and gravitationally disrupt a planetary system, flinging worlds into icy interstellar space. However, a star’s habitable zone — the distance at which a planet would be warm enough for liquid water — varies depending on the star. While brighter stars have more distant habitable zones, planets orbiting dimmer stars would have to huddle much closer. Brighter stars also live shorter lives, and since globular clusters are old, those stars have died out. The predominant stars in globular clusters are faint, long-lived red dwarfs. Any potentially habitable planets they host would orbit nearby and be relatively safe from stellar interactions.


“Once planets form, they can survive for long periods of time, even longer than the current age of the universe,” explains Di Stefano.
So if habitable planets can form in globular clusters and survive for billions of years, what are the consequences for life should it evolve? Life would have ample time to become increasingly complex, and even potentially develop intelligence.
Such a civilization would enjoy a very different environment than our own. The nearest star to our solar system is four light-years, or 24 trillion miles, away. In contrast, the nearest star within a globular cluster could be about 20 times closer — just 1 trillion miles away. This would make interstellar communication and exploration significantly easier.


The closest globular cluster to Earth is still several thousand light-years away, making it difficult to find planets, particularly in a cluster’s crowded core. But it could be possible to detect transiting planets on the outskirts of globular clusters. Astronomers might even spot free-floating planets through gravitational lensing, in which the planet’s gravity magnifies light from a background star. A more intriguing idea might be to target globular clusters with SETI search methods, looking for radio or laser broadcasts. The concept has a long history: In 1974 astronomer Frank Drake used the Arecibo radio telescope to broadcast the first deliberate message from Earth to outer space. It was directed at the globular cluster Messier 13 (M13).

The Daily Galaxy via Harvard University

Image credits: 


At least two methods have been used to measure the distance to the Sombrero Galaxy.The first method relies on comparing the measured fluxes from planetary nebulae in the Sombrero Galaxy to the known luminosities of planetary nebulae in the Milky Way Galaxy.This method gave the distance to the Sombrero Galaxy as 29 ± 2 Mly (8,890 ± 610 kpc). The other method used is the surface brightness fluctuations method, This method uses the grainy appearance of the galaxy's bulge to estimate the distance to it. Nearby galaxy bulges will appear very grainy, while more distant bulges will appear smooth. Early measurements using this technique gave distances of 30.6 ± 1.3 Mly (9,380 ± 400 kpc). Later, after some refinement of the technique, a distance of 32 ± 3 Mly (9,810 ± 920 kpc) was measured. This was even further refined in 2003 to be 29.6 ± 2.5 Mly (9,080 ± 770 kpc)


M42, also known as the Great Orion Nebula or Orion Nebula, is the prime deep sky attraction in the constellation of Orion and a showpiece deep sky object. With an apparent magnitude of +4.0, it's easily visible to the naked eye. This emission reflection nebula and star forming region spans more than a degree of sky and is therefore one of the largest and brightest objects of its type.
Orion is a prominent constellation and one of the most recognizable and familiar sights. Located on the celestial equator, it's visible throughout the World and best seen during the months of December, January and February. The constellation is filled with bright stars, including first magnitude Rigel and Betelgeuse plus a further five second magnitude stars. Three of the second magnitude stars (Mintaka, Alnilam and Alnitak) form the famous belt of Orion. Positioned just 5 degrees south of the belt is the Orion Nebula itself, which is part of the Hunters Sword.


To the naked eye, M42 appears as a soft diffuse glow surrounding the stars of the sword of Orion. When viewed through 10x50 binoculars, it's a prominent feature appearing large and bright. The centre region is obvious, with parts of fainter nebulosity extending outwards towards the east and west in the shape of two wings. Two prominent bright stars, embedded within the nebula, are easily visible at the heart of M42. They form the famous multiple star, Theta1 Orionis, commonly known as the Trapezium. This grouping, which is one of the most observed multiple star systems consists of four bright members in the shape of a trapezoid, plus a few fainter stars. An 80mm (3.1-inch) telescope at low/medium power easily splits the Trapezium into its main components. Combined with the surrounding nebula, it's a fantastic view. The four brightest stars of the Trapezium have magnitudes of +5.1(C), +6.7(D), +6.7->7.7(A) and +8.0->8.7(B) respectively. Unusually, they are lettered in order of right ascension instead of magnitude. A challenge for observers of the Trapezium is to spot two of the fainter members, 11th mag. stars E and F. They can be observed with apertures of 80mm (3.1 inches) on nights of good seeing, but much easier with scopes of the order of 150mm (6 inches) or greater.


The first VLTI image is that of the double star Theta1 Orionis C in the Orion Nebula Trapezium. From these, and several other observations, the team of astronomers, led by Stefan Kraus and Gerd Weigelt from the Max-Planck Institute in Bonn, could obtain the full orbit of the two stars in the system, and derive the total mass of the two stars (47 solar masses) and their distance from us (1350 light-years).
This montage shows a wide-view of the Orion Nebula as seen with ISAAC on ESO’s Very Large Telescope, a zoom of the Trapezium obtained with the NASA/ESA Hubble Space Telescope, and the orbit derived by the astronomers, using several facilities over 11 years. The VLTI images created for this system have an extraordinary spatial resolution of about 2 milli-arcseconds.



ESO/S.Kraus et al., M.McCaughrean et al. (AIP)

Large telescopes reveal more intrigue details in M42. The view through a 200mm (8-inch) telescope is superb. At low magnifications, the Orion Nebula fills the field of view with significant amounts of structural detail, such as twists and wisps of cloud formations visible. The Trapezium is very evident and bright. Visually the Orion Nebula can often exhibit a green hue but photographically it appears mostly red. The discovery of the Orion Nebula is generally credited to French astronomer Nicolas-Claude Fabri de Peiresc. He recorded it on November 26, 1610. It was then independently located by Johann Baptist Cysat in 1611. Surprisingly, neither Ptolemy's Almagest nor Al Sufi's Book of Fixed Stars noted the nebula, even though they both listed patches of nebulosity elsewhere in the sky. Galileo Galilei made telescopic observations of the surrounding region in 1610 and 1617, but also failed to notice M42. However, he did discover the Trapezium on February 4, 1617. This has led to some to speculate that there has since been a flare-up of the illuminating stars, increasing the brightness of the nebula.


The Orion Nebula is a spectacular deep sky object and one of the most famous of all. It's visible to the naked eye as a faint haze, a wonderful sight in binoculars and spectacular through telescopes. You are looking at a stellar nursery where stars are been born. At the heart of the nebula and illuminating the surrounding region is a group of stars known as the Trapezium. This multiple star system consists of four main bright members and is easily resolvable in small scopes.

Nicolas-Claude Fabri de Peiresc (1 December 1580 – 24 June 1637), often known simply as Peiresc, or by the Latin form of his name Peirescius, was a French astronomer, antiquary and savant who maintained a wide correspondence with scientists and was a successful organizer of scientific inquiry. 


Winter Triangle

M42 is located 1,340 light years away from Earth and has a spatial diameter of 24 light-years. Positioned only 8 arc minutes north of M42 is M43, which is also part of the Orion Nebula. It's separated from the main nebula by a dark dust lane.
Messier 42, NGC, 1976, Name    Orion Nebula
Object Type    Emission and Reflection Nebula
Constellation    Orion
Distance (light-years)    1,340
Apparent Mag.    +4.0
RA (J2000) - 05h 35m 17s
DEC (J2000) -05d 23m 27s
Apparent Size (arc mins)    65 x 60
Radius (light-years)    12
Other Name    Sharpless 281
Notable Feature    Trapezium Cluster

The average distance measured through these two techniques is 29.3 ± 1.6 Mly (8,980 ± 490 kpc). The absolute magnitude (in the blue) of the Sombrero Galaxy is estimated to be −21.9 at 30.6 Mly (9,400 kpc) (−21.8 at the average distance of above), that as stated above makes it the brightest galaxy within a radius of 32.6 Mly (10,000 kpc) around the Milky Way. A report from 2016 used the Hubble Space Telescope to measure the distance to M104 based on the tip of the red giant branch method yielding 9.55 ± 0.13 ± 0.31 Mpc.


Constellation Orion rising over a suburban street in Burlington, Ontario, at about 9:45 PM on the evening of 2013 March 26. Betelgeuse, the brightest star in Orion, is in the middle of the frame and about 1/8th of the way down from the top.

The Sombrero Galaxy lies within a complex, filament-like cloud of galaxies that extends to the south of the Virgo Cluster. However, it is unclear whether the Sombrero Galaxy is part of a formal galaxy group. Hierarchical methods for identifying groups, which determine group membership by considering whether individual galaxies belong to a larger aggregate of galaxies, typically produce results showing that the Sombrero Galaxy is part of a group that includes NGC 4487, NGC 4504, NGC 4802, UGCA 289, and possibly a few other galaxies. However, results that rely on the percolation method (i.e. the "friends-of-friends" method), which links individual galaxies together to determine group membership, indicate that either the Sombrero Galaxy is not in a group or that it may only be part of a galaxy pair with UGCA 287. Besides that, M104 is also accompanied by an ultracompact dwarf galaxy, that was discovered in 2009. This object has an absolute magnitute of -12.3, a radius where half of its light is emitted of just 47.9 ly (3,030,000 AU), and a mass of 3.3*107 M.


The Sombrero Galaxy is located 11.5° west of Spica and 5.5° northeast of Eta Corvi,  Although the galaxy is visible with 7x35 binoculars or a 4-inch (100 mm) amateur telescope, an 8-inch (200 mm) telescope is needed to distinguish the bulge from the disk, and a 10-or-12-inch (250 or 300 mm) telescope is needed to see the dark dust lane.

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