Trumpler 27 is a possible

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

in the southern constellation

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Gre ...

. If it exists, it is a few thousand light-years away from the Sun, with estimates ranging from 3,900 light-years (1,210 kiloparsecs) to 6,800 light-years (2,100 kiloparsecs) The name refers to

Robert Julius Trumpler Robert Julius Trumpler (until 1915 Robert Trümpler, born October 2, 1886 in Zürich, Switzerland; died September 10, 1956 in Berkeley, United States) was a Swiss-American astronomer. Career After initial schooling, Trumpler entered the Universit ...

's catalog of open clusters, published in 1930. It was originally thought to be young open cluster in the outer edge of the

Sagittarius Arm Sagittarius ( ) may refer to: * Sagittarius (constellation) * Sagittarius (astrology), a sign of the Zodiac Ships *'' SuperStar Sagittarius'', a cruise ship * USS ''Sagittarius'' (AKN-2), a World War II US Navy cargo ship Music * Sagittarius ...

, still surrounded by

interstellar matter In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar s ...

. The light from the stars is heavily extinguished and reddened by intervening interstellar dust. The light coming from the stars is also significantly polarized. However, a close study in 2012 could not confirm whether the stars truly form a cluster, or if they are a close alignment of bright stars. Several member stars have been studied in closer detail. Star #1 of Trumpler 27 is CD−33°12241, a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Anta ...

star with a

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of M0Ia. Stars #28 and #105 are Wolf-Rayet stars. Star #27, a

blue giant In astronomy, a blue giant is a hot star with a luminosity class of III (giant star, giant) or II (bright giant). In the standard Hertzsprung–Russell diagram, these stars lie above and to the right of the main sequence. The term applies to a ...

star with a spectral type of O8III((f)), may be one of the

most luminous stars This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance t ...

known, with a

bolometric magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it w ...

of −10.5. Star #102 is known as V925 Scorpii or HD 159378, and is a rare yellow supergiant star.

References

{{Scorpius Open clusters Scorpius (constellation)