Maffei 1 is a massive

elliptical galaxy An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work ''The R ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Cassiopeia. Once believed to be a member of the

Local Group The Local Group is the galaxy group that includes the Milky Way. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...

of galaxies, it is now known to belong to a separate group, the

IC 342/Maffei Group The IC 342/Maffei Group (also known as the IC 342 Group or the Maffei 1 Group) corresponds to one or two galaxy groups close to the Local Group. The member galaxies are mostly concentrated around either IC 342 or Maffei 1, which would be the brig ...

. It was named after

Paolo Maffei Paolo Maffei (2 January 1926 – 1 March 2009) was an Italian astrophysicist and science writer. He was born in Arezzo and was director of the Catania Observatory and an astronomer at Arcetri, Bologna, Asiago and Hamburg. He studied ...

, who discovered it and the neighboring

Maffei 2 Maffei 2 is an intermediate spiral galaxy about 10 million light-years away in the constellation Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. Maffei 2 lies in the Zone of Avoidan ...

in 1967 via their

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

emissions. Maffei 1 is a slightly flattened core type elliptical galaxy. It has a boxy shape and is made mainly of old

metal-rich In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as ...

stars. It has a tiny blue nucleus in which stars continue to form. Like all large ellipticals it contains a significant population of globular clusters. Maffei 1 is situated at an estimated distance of 3–4 Mpc from the Milky Way. It may be the closest giant elliptical galaxy. Maffei 1 lies in the

Zone of Avoidance The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), is the area of the sky that is obscured by the Milky Way. The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard ...

and is heavily obscured by the Milky Way's

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s and

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...

. If it were not obscured, it would be one of the largest (about 3/4 the size of the

full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic coordinate system, ecliptic longitudes of the Sun and Moon opp ...

), brightest, and best-known galaxies in the sky. It can be observed visually, using a 30–35 cm or bigger telescope under a very dark sky.

Discovery

The Italian astronomer

was one of the pioneers of

infrared astronomy Infrared astronomy is a sub-discipline of astronomy which specializes in the observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers, and falls in betwee ...

. In the 1950s and 60s, in order to obtain high quality images of celestial objects in the very

near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

part of the spectrum (the I-band, 680–880 nm), he used chemically hyper-sensitized standard Eastman emulsions I-N. To achieve the hyper-sensitization he immersed them in 5%

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

solution for 3–5 minutes. This procedure increased their sensitivity by an order of magnitude. Between 1957 and 1967 Maffei observed many different objects using this technique, including

globular clusters A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member ...

and

planetary nebulae A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated t ...

. Some of those objects were not visible at all on blue light (250–500 nm) sensitive plates. The galaxy Maffei 1 was discovered on a hyper-sensitized I-N photographic plate exposed on 29 September 1967 with the Schmidt telescope at

Asiago Observatory The Asiago Astrophysical Observatory (''Osservatorio Astrofisico di Asiago'', or Asiago Observatory for short) is an Italian astronomical observatory (IAU code 043) owned and operated by the University of Padua. Founded in 1942, it is located on ...

. Maffei found Maffei 1, together with its companion spiral galaxy

, while searching for

diffuse nebulae A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming region ...

and

T Tauri star T Tauri stars (TTS) are a class of variable stars that are less than about ten million years old. This class is named after the prototype, T Tauri, a young star in the Taurus star-forming region. They are found near molecular clouds and iden ...

s. The object had an apparent size up to 50″ in the near infrared but was not visible on the corresponding blue light sensitive plate. Its spectrum lacked any emission or absorption lines. Later it was shown to be radio-quiet as well. In 1970

Hyron Spinrad Hyron Spinrad (February 17, 1934 – December 7, 2015) was an American astronomer. His research has ranged from the study of planet atmospheres to the evolution of galaxies. From 2010 until his death in late 2015 he was an emeritus professor ...

suggested that Maffei 1 is a nearby heavily obscured giant elliptical galaxy. Maffei 1 would be among the ten brightest galaxies in the northern sky if not situated behind the Milky Way.

Distance

Maffei 1 is located only 0.55° from the galactic plane in the middle of the

zone of avoidance The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), is the area of the sky that is obscured by the Milky Way. The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard ...

and suffers from about 4.7 magnitudes of

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

(a factor of about 1/70) in visible light. In addition to extinction, observation of Maffei 1 is further hindered by the fact that it is covered by myriads of faint Milky Way stars, which can easily be confused with its own. As a result, determining its distance has been particularly difficult. In 1971, soon after its discovery, Hyron Spinrad estimated the distance to Maffei 1 at about 1 Mpc, which would place it within the

of galaxies. In 1983 this estimate was revised up to 2.1 Mpc by Ronald Buta and Marshall McCall using the general relation between the luminosity and

velocity dispersion In astronomy, the velocity dispersion (''σ'') is the statistical dispersion of velocity, velocities about the Arithmetic mean, mean velocity for a group of astronomical objects, such as an open cluster, globular cluster, galaxy, galaxy cluster, or ...

for

elliptical galaxies An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work ''The Real ...

. That distance puts Maffei 1 well outside the Local Group, but close enough to have influenced it in the past. In 1993 Gerard Luppino and John Tonry used surface brightness fluctuations to derive a new distance estimate to Maffei 1 of . Later in 2001, Tim Davidge and

Sidney van den Bergh Sidney Van den Bergh, OC, FRS (born 20 May 1929 in Wassenaar) is a retired Dutch-Canadian astronomer. He showed an interest in science from an early age, learning to read with books on astronomy. In addition to being interested in astronomy. ...

used adaptive optics to observe the brightest

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

stars in Maffei 1 and concluded that it is located at the distance 4.4 Mpc from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The latest determination of the distance to Maffei 1, which is based on the re-calibrated luminosity/velocity dispersion relation for the elliptical galaxies and the updated extinction, is , or over 9 million

light years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

away. For perspective, the nearby

Andromeda Galaxy The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gala ...

is estimated to be about 2.5 million light years away. The larger (≥3 Mpc) distances reported in the past 20 years would imply that Maffei 1 has never been close enough to the Local Group to significantly influence its dynamics. Maffei 1 moves away from the Sun at the speed of about 66 km/s. Its velocity relative to the Local Group's

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...

is, however, 297 km/s away. That means that Maffei 1 participates in the general

expansion of the Universe The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not exp ...

Physical properties

Size and shape

Maffei 1 is a massive elliptical galaxy classified as type E3 in the

Hubble classification The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. It is often colloquially known as the Hubble tuning-fork diagram because the shape in which it is traditionally represented resembles a t ...

scheme. This means that it is slightly flattened, its

semi-minor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both focus (geometry), foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major wikt: ...

being 70% of its

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

. Maffei 1 has also a boxy shape (E(b)3 type), while its central region (radius ≈ 34 pc) is deficient in light emission as compared to the r^1/4 law, meaning that Maffei 1 is a core type elliptical. Both the boxy shape and the presence of an underluminous core are typical of intermediate to massive ellipticals. The apparent dimensions of Maffei 1 depend strongly on the wavelength of light because of the heavy obscuration by the Milky Way. In blue light it is 1–2′ across while in the near infrared its major axis reaches 23′—more than 3/4 of the Moon's diameter. At a distance of 3 Mpc this corresponds to approximately 23 kpc. The total visible absolute magnitude of Maffei 1, M_V=−20.8, is comparable to that of the Milky Way. Maffei 1 and 2 cropped

Nucleus

Maffei 1 possesses a tiny blue nucleus at its center approximately 1.2 pc across. It contains about 29

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es of

ionized Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...

hydrogen. This implies that it has undergone recent star formation. There are no signs of an

active galactic nucleus An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not pr ...

(AGN) in the center of Maffei 1. The X-ray emission from the center is extended and likely comes from a number of stellar sources.

Stars and stellar clusters

Maffei 1 is mainly made of old metal-rich stars more than 10 billion years in age. As a large elliptical galaxy, Maffei 1 is expected to host a significant population of

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

s (about 1100). However, due to heavy intervening absorption, ground-based observations for a long time failed to identify any of them. Observations by the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

in 2000 revealed about 20 globular cluster candidates in the central region of the galaxy. Later infrared observations from telescopes on the ground also found a population of bright globular cluster candidates.

Group membership

Maffei 1 is a principal member of a nearby group of galaxies. The group's other members are the giant spiral galaxies

IC 342 IC 342 (also known as Caldwell 5) is an intermediate spiral galaxy in the constellation Camelopardalis, located relatively close to the Milky Way. Despite its size and actual brightness, its location behind dusty areas near the galactic equator m ...

and

. Maffei 1 has also a small satellite spiral galaxy

Dwingeloo 1 Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparabl ...

as well as a number of dwarf satellites like MB1. The Group is one of the closest galaxy groups to the Milky Way galaxy.

Notes

References

External links

Maffei 1
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Astronomy Picture of the Day Astronomy Picture of the Day (APOD) is a website provided by NASA and Michigan Technological University (MTU). According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation writt ...

2010 March 9 {{Sky, 02, 36, 35.4, +, 59, 39, 19, 9800000 Elliptical galaxies Peculiar galaxies IC 342/Maffei Group Cassiopeia (constellation) 09892 Sharpless objects UGCA objects