NGC 7552 (also known as IC 5294) is a barred spiral galaxy in the constellation Grus. It is at a distance of roughly 60 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, which, given its apparent dimensions, means that NGC 7552 is about 75,000 light years across. It forms with three other spiral galaxies the Grus Quartet.

Observation history

NGC 7552 was originally discovered and reported in 1826 by James Dunlop and

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...

added it in the ''

General Catalogue of Nebulae and Clusters A general officer is an officer of high rank in the armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers to a rank above colonel."general, adj. and n.". OED On ...

'' as number 3977. However,

Lewis Swift Lewis A. Swift (February 29, 1820 – January 5, 1913) was an American astronomer who discovered 13 comets and 1,248 previously uncatalogued nebulae. Only William Herschel discovered more nebulae visually. Discoveries Swift discovered or co-discov ...

reported the galaxy independently in on October 22, 1897, at right ascention 9 arcseconds off the location of the galaxy and was included in ''

Index Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and em ...

'' as IC 5294.

Structure

NGC 7552 is a barred spiral galaxy, with two spiral arms forming an outer pseudo-ring. The galaxy is seen nearly face on, at an inclination of ~ 28°. The one arm is more prominent and the less prominent arm shows no clear continuation with the bar. The bar is dusty, and four huge HII regions are detected in it. The disk features numerous scattered

HII region An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...

s in an asymmetric pattern. The total

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 ...

luminosity of the galaxy is , and thus is categorised as a luminous infrared galaxy.

Starburst ring

NGC 7552 taken by T-ReCS - Geminiann11015b

In 1994, Forbes et al. observed a partial starburst ring with 1 kpc radius at Br-gamma with various hot spots. They also detected a small-scale molecular bar and a large reservoir of molecular material, however, no evidence of current activity was detected at the nucleus. The ring is more than 100 parsecs wide. The ring is brighter north of the nucleus and there is inhabited by the younger star populations. Brandl et al. detected in near- and mid-infrared nine prominent structures within the ring they identified as star clusters with stellar ages ranging between 5.5 Myr and 6.3 Myr. These clusters account for the 75% of the bolometric luminosity of the starburst ring, with total luminosity of the clusters 2.1 × 10¹⁰ L⊙. Numerous supernova remnants have been observed in the ring. Further observations of the galaxy in radio waves showed that NGC 7552 contains three star forming rings of radii 1.0 kpc, 1.9 kpc, and 3.4 kpc as observed by the

Very Large Array The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twen ...

at 46.9 MHz and the

Australia Telescope Compact Array The Australia Telescope Compact Array (ATCA) is a radio telescope operated by CSIRO at the Paul Wild Observatory, twenty five kilometres (16 mi) west of the town of Narrabri in New South Wales, Australia. Its opening ceremony took place on ...

. One

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

has been observed in NGC 7552: SN 2017bzc ( Type Ia, mag. 12.8).

Galaxy group

NGC 7552 belongs in NGC 7582 group, also known as the Grus group. Other members of the group include the spiral galaxies

NGC 7599 NGC commonly refers to: * New General Catalogue of Nebulae and Clusters of Stars, a catalogue of deep sky objects in astronomy NGC may also refer to: Companies * NGC Corporation, name of US electric company Dynegy, Inc. from 1995 to 1998 * Nat ...

NGC 7590 NGC commonly refers to: * New General Catalogue of Nebulae and Clusters of Stars, a catalogue of deep sky objects in astronomy NGC may also refer to: Companies * NGC Corporation, name of US electric company Dynegy, Inc. from 1995 to 1998 * Nat ...

, and NGC 7582, which along with NGC 7552 form the Grus Quartet. A large tidal extension of HI reaches from NGC 7582 to NGC 7552, which is indicative of interactions between the group members, yet NGC 7552 does not have highly disturbed morphology.

References

External links