Bedin I is a

dwarf spheroidal galaxy A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and to systems that are comp ...

located in the constellation Pavo. It is situated around 28.38 million

light-year 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 ...

s from Earth, behind the

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 ...

NGC 6752 NGC 6752 (also known as Caldwell 93 and nicknamed the Great Peacock Globular) is a globular cluster in the constellation Pavo. It is the fourth-brightest globular cluster in the sky, after Omega Centauri, 47 Tucanae and Messier 22, respectively. ...

. Bedin I is possibly one of the oldest galaxies known, having formed around 10–13 billion years ago, and is one of the most isolated dwarf galaxies known, situated around 2.12 million light-years away from

NGC 6744 __NOTOC__ NGC 6744 (also known as Caldwell 101) is an intermediate spiral galaxy about 30 million light-years away in the constellation Pavo (Peacock). It is considered as a Milky Way mimic in the immediate vicinity, displaying flocculent (fluff ...

, its nearest neighbor with which it may be physically associated. As such, it has been deemed by astronomers as a "fossil" from the

early universe The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, wit ...

. It was accidentally discovered by Italian astronomer Luigi Bedin, whose team was studying

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

s in NGC 6752 using the ''Hubble'' Space Telescope in September 2018; the discovery was announced in a paper published in January 2019.

Nomenclature

Bedin I, pronounced , was named by its discovery team after their leader, Luigi Bedin, who is a researcher at the

National Institute for Astrophysics The National Institute for Astrophysics ( it, Istituto Nazionale di Astrofisica, or INAF) is an Italian research institute in astronomy and astrophysics, founded in 1999. INAF funds and operates twenty separate research facilities, which in turn e ...

's observatory in

Padua Padua ( ; it, Padova ; vec, Pàdova) is a city and ''comune'' in Veneto, northern Italy. Padua is on the river Bacchiglione, west of Venice. It is the capital of the province of Padua. It is also the economic and communications hub of the ...

, Italy. He was credited as the galaxy's sole discoverer. Bedin and the team opted to avoid the galaxy being given "an anonymous identification based on its coordinates."

Characteristics

Bedin I is an isolated dwarf spheroidal galaxy located around 8.7 megaparsecs, or around 28.38 million light-years, from Earth, with similar characteristics to KKR 25 and the Tucana Dwarf Galaxy. It is estimated to be around 840 by 340

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s, or 2,700 by 1,100

s, in size, which is a fifth the size of the

Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...

. At a

metallicity 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 a ...

of −1.3, the galaxy's population is made up of metal-poor

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

stars, and its luminosity is roughly a thousand times dimmer than the

Milky Way Galaxy The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

, at an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of −9.76. Bedin I is believed to have formed around 10–13 billion years ago with no star formation having occurred since then, making it one of the oldest galaxies known. Bedin I is also possibly the most isolated dwarf galaxy known, located at least 650 kiloparsecs, or 2.12 million light-years, from its nearest neighbor, the

intermediate spiral galaxy An intermediate spiral galaxy is a galaxy that is in between the classifications of a barred spiral galaxy and an unbarred spiral galaxy. It is designated as SAB in the galaxy morphological classification system devised by Gerard de Vaucouleur ...

NGC 6744; the Milky Way and Andromeda galaxies are separated by a similar distance. A physical association with NGC 6744 has been speculated however, due to the close

angular distance Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

between the galaxies, and their similar physical distances from Earth. Its age, isolation, and lack of interaction with other galaxies has led to the galaxy being deemed a "fossil" from the

Observation

Bedin I is located in the constellation Pavo, at a

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

of and

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...

of . The galaxy is situated behind a group of unnamed foreground stars within the globular cluster NGC 6752. Bedin I measures around 20 by 8

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

across and has an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 19.94, although its visibility is significantly decreased by NGC 6752, one of the brightest globular clusters in the sky with an apparent magnitude of 5.4. Bedin I was accidentally discovered by a team researching white dwarfs in the cluster in an effort to better determine the cluster's age. The galaxy partially appeared in the field of view during program GO-15096 of the ''Hubble'' Space Telescope, led by

principal investigator In many countries, the term principal investigator (PI) refers to the holder of an independent grant and the lead researcher for the grant project, usually in the sciences, such as a laboratory study or a clinical trial. The phrase is also often us ...

Luigi R. Bedin, which occurred between 7 and 18 September 2018. The program, which saw the Wide Field Channel (WFC) of the

Advanced Camera for Surveys The Advanced Camera for Surveys (ACS) is a third-generation axial instrument aboard the Hubble Space Telescope (HST). The initial design and scientific capabilities of ACS were defined by a team based at Johns Hopkins University. ACS was assembl ...

(ACS) pointed at NGC 6752 for 75 exposures lasting 1,270 seconds each, was conducted over 40 orbits; these exposures were able to capture objects with an apparent magnitude above 30. Five of the orbits failed however, due to poor guide star acquisition. The journal '' Monthly Notices of the Royal Astronomical Society: Letters'' published the team's three-part

scientific paper : ''For a broader class of literature, see Academic publishing.'' Scientific literature comprises scholarly publications that report original empirical and theoretical work in the natural and social sciences. Within an academic field, scienti ...

on findings from the program on 31 January 2019, with the first part dedicated to the discovery of Bedin I. A second program of 40 orbits, GO-15491, is currently scheduled for late 2019.

References

Notes Sources # # Citations

External links

The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background
Lock-green

at '' Monthly Notices of the Royal Astronomical Society: Letters'' Archived
31 January 2019) {{DEFAULTSORT:Bedin I Astronomical objects discovered in 2018 Discoveries by the Hubble Space Telescope Dwarf spheroidal galaxies Pavo (constellation)

Nomenclature

Characteristics

Observation

See also

References

External links