The Chamaeleon complex is a large star forming region (SFR) at the surface of the Local Bubble that includes the Chamaeleon I, Chamaeleon II, and Chamaeleon III dark clouds. It occupies nearly all of the constellation Chamaeleon and overlaps into Apus, Musca, Carina and Octans. The mean density of X-ray sources is about one source per square degree. [2]
The Chamaeleon I (Cha I) cloud is one of the nearest active star formation regions at ~160 pc. [3] It is relatively isolated from other star-forming clouds, so it is unlikely that older pre-main sequence (PMS) stars have drifted into the field. [3] The total stellar population is 200–300. [3] The Cha I cloud is further divided into the North cloud or region and South cloud or main cloud.
HD 97300 emits X-rays, illuminates the reflection nebula IC 2631 and is one of the highest mass members of the Cha I cloud, spectral type B9V, a Herbig Ae/Be star without emission lines. [3]
Cha Helpha 1 is an object of spectral type M8 in the Chamaeleon I dark cloud that was determined in 1998 to be an X-ray source and as such is the first X-ray emitting brown dwarf found.
There are some seventy to ninety X-ray sources in the Chamaeleon I star forming region. [4] The Uhuru X-ray source (4U 1119–77) is within the Chamaeleon I cloud. This source region within the Chamaeleon I dark cloud was observed by ROSAT on February 9 at 22:14:47 UTC to February 18, 1991, 17:59:12 UTC, and on March 6, 1991, from 09:12:19 to 13:05:13 UTC. [4] This cloud contains both "weak" T Tauri (WTT) stars and "classical" T Tauri (CTT) stars. [4] Chamaeleon I X-ray ROSAT source 66 is at RA 11h 17m 36.4-37.9s Dec -77° 04' 27-50", is a CTT, Chamaeleon I No. T56, aka CTT star HM 32. [4]
The Chamaeleon I dark cloud was observed with the Imaging Proportional Counter (IPC) on board the Einstein Observatory for 2.5 h on January 23–24, 1981, identifying some 22 X-ray sources. [5] None of these sources was closer than 8' to 4U 1119–77.
Chamaeleon II contains the Uhuru source 4U 1302–77. It is close to RXJ 1303.1-7706 at RA 13h 03m 04.70s Dec -77° 06' 55.0", a K7-M0 new WTT. [2] The Chamaeleon II dark cloud contains some 40 X-ray sources. [6] Observation in Chamaeleon II was carried out from September 10 to 17, 1993. [6] Source RXJ 1301.9-7706, a new WTTS candidate of spectral type K1, is closest to 4U 1302–77. [6]
"Chamaeleon III appears to be devoid of current star-formation activity." [7] There are two particularly prominent nebulae associated with this area. The smaller is commonly known as the Thumbprint Nebula [8] and the larger The Talon Nebula. [9]
The cloud is sometimes extended with an eastern part, [10] and together with the distinctively long Dark Doodad Nebula (or Musca nebula) to the north the complex is called the Musca-Chamaeleonis Molecular Cloud. [11]
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. X-ray astronomy uses a type of space telescope that can see x-ray radiation which standard optical telescopes, such as the Mauna Kea Observatories, cannot.
The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about 5.78 kiloparsecs (18,900 light-years), and contains several hundred million stars. It has a total mass of approximately 7 billion solar masses. At a distance of about 200,000 light-years, the SMC is among the nearest intergalactic neighbors of the Milky Way and is one of the most distant objects visible to the naked eye.
Musca is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe 35 cm (14 in) in diameter published in 1597 in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. It was also known as Apis for 200 years. Musca remains below the horizon for most Northern Hemisphere observers.
The Trifid Nebula is an H II region in the north-west of Sagittarius in a star-forming region in the Milky Way's Scutum-Centaurus Arm. It was discovered by Charles Messier on June 5, 1764. Its name means 'three-lobe'. The object is an unusual combination of an open cluster of stars, an emission nebula, a reflection nebula, and a dark nebula. Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
Gliese 1 is a red dwarf in the constellation Sculptor, which is found in the southern celestial hemisphere. It is one of the closest stars to the Sun, at a distance of 14.2 light years. Because of its proximity to the Earth it is a frequent object of study and much is known about its physical properties and composition. However, with an apparent magnitude of about 8.6 it is too faint to be seen with the naked eye.
The Cygnus Loop is a large supernova remnant (SNR) in the constellation Cygnus, an emission nebula measuring nearly 3° across. Some arcs of the loop, known collectively as the Veil Nebula or Cirrus Nebula, emit in the visible electromagnetic range. Radio, infrared, and X-ray images reveal the complete loop.
OTS 44 is a free-floating planetary-mass object or brown dwarf located at 550 light-years (170 pc) in the constellation Chamaeleon near the reflection nebula IC 2631. It is among the lowest-mass free-floating substellar objects, with approximately 11.5 times the mass of Jupiter, or approximately 1.1% that of the Sun. Its radius is not very well known and is estimated to be 23–57% that of the Sun.
IC 443 is a galactic supernova remnant (SNR) in the constellation Gemini. On the plane of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years from Earth.
The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 900 to 1,500 light-years away.
NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. The nebula contains many proto-stars shielded by dark discs of gas, and young stars wrapped in expanding "cocoons" or expanding gases surrounding these small stars. It is also known as the Lobster Nebula. This nebula was given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance, which, in infrared images the bright, western part resembles a dove, while the eastern part looks like a skull. A petition by anime fans to rename it as the Madokami nebula, due to resemblance with a character, was unsuccessful.
IC 5146 is a reflection/emission nebula and Caldwell object in the constellation Cygnus. The NGC description refers to IC 5146 as a cluster of 9.5 mag stars involved in a bright and dark nebula. The cluster is also known as Collinder 470. It shines at magnitude +10.0/+9.3/+7.2. Its celestial coordinates are RA 21h 53.5m, dec +47° 16′. It is located near the naked-eye star Pi Cygni, the open cluster NGC 7209 in Lacerta, and the bright open cluster M39. The cluster is about 4,000 ly away, and the central star that lights it formed about 100,000 years ago; the nebula is about 12 arcmins across, which is equivalent to a span of 15 light years.
V420 Aurigae is a high-mass star with an inferred compact companion. Closely orbiting each other every 0.8 days, they are a source of X-ray emission.
Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.
Gliese 208 is a red dwarf star with an apparent magnitude of 8.9. It is 37 light years away in the constellation of Orion. It is an extremely wide binary with 2MASS J0536+1117, an M4 star 2.6 arcminutes away
The Lockman Hole is an area of the sky in which minimal amounts of neutral hydrogen gas are observed from the perspective of Earth. The Lockman Hole is a relatively clear window on distant objects, which makes it an attractive area of the sky for observational astronomy surveys. It is located near the pointer stars of the Big Dipper in the constellation Ursa Major and is ~15 square degrees in size.
ν Chamaeleontis, Latinized as Nu Chamaeleontis, is a single star in the southern circumpolar constellation of Chamaeleon. It is a yellow-hued star, dimly visible to the naked eye, with an apparent visual magnitude of 5.43. This object is located at a distance of 189 light-years from the Sun, based on its parallax, and is drifting further away with a radial velocity of +11 km/s. It has an absolute magnitude of 1.59.
AZ Cancri (AZ Cnc) is a M-type flare star in the constellation Cancer. It has an apparent visual magnitude of approximately 17.59.
Westerhout 40 or W40 is a star-forming region in the Milky Way located in the constellation Serpens. In this region, interstellar gas forming a diffuse nebula surrounds a cluster of several hundred new-born stars. The distance to W40 is 436 ± 9 pc, making it one of the closest sites of formation of high-mass O-type and B-type stars. The ionizing radiation from the massive OB stars has created an H II region, which has an hour-glass morphology.
HD 104237 is a candidate multiple star system in the southern constellation of Chamaeleon. It has the variable star designation DX Chamaeleontis, abbreviated DX Cha; HD 104237 is the stellar designation from the Henry Draper Catalogue. The system is dimly visible to the naked eye with an apparent visual magnitude that ranges from 6.59 down to 6.70. It is located at a distance of approximately 348 light-years from the Sun based on parallax measurements. The system is positioned just 2′ to the north-east of the 5th magnitude star Epsilon Chamaeleontis, and is a member of the ε Cha association of co-moving stars.
