V838 Monocerotis is a spectroscopic binary star system in the constellation Monoceros about 19,000 light years from the Sun. The previously unremarked star was observed in early 2002 experiencing a major outburst, and was one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then identified as the first of a new class of eruptive variables known as luminous red novae. The reason for the outburst is still uncertain, but is thought to have been a merger of two stars within a triple system.
A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star. Nearly 180 proplyds have been discovered in the Orion Nebula. Images of proplyds in other star-forming regions are rare, while Orion is the only region with a large known sample due to its relative proximity to Earth.
NGC 2346 is a planetary nebula near the celestial equator in the constellation of Monoceros, less than a degree to the ESE of Delta Monocerotis. It is informally known as the Butterfly Nebula. The nebula is bright and conspicuous with a visual magnitude of 9.6, and has been extensively studied. Among its most remarkable characteristics is its unusually cool central star, which is a spectroscopic binary, and its unusual shape.
The Red Rectangle Nebula, so called because of its red color and unique rectangular shape, is a protoplanetary nebula in the Monoceros constellation. Also known as HD 44179, the nebula was discovered in 1973 during a rocket flight associated with the AFCRL Infrared Sky Survey called Hi Star. The binary system at the center of the nebula was first discovered by Robert Grant Aitken in 1915.
Sher 25 is a blue supergiant star in the constellation Carina, located approximately 25,000 light years from the Sun in the H II region NGC 3603 of the Milky Way. It is a spectral type B1Iab star with an apparent magnitude of 12.2. Its initial main sequence mass is calculated at 60 times the mass of the Sun, but a star of this type will have already lost a substantial fraction of that mass. It is unclear whether Sher 25 has been through a red supergiant phase or has just evolved from the main sequence, so the current mass is very uncertain.
NGC 1808 is a barred spiral galaxy located in the southern constellation of Columba, about two degrees to the south and east of Gamma Caeli. It was discovered by Scottish astronomer James Dunlop, who described it as a "faint nebula". The galaxy is a member of the NGC 1808 group, which is part of the larger Dorado Group.
NGC 1333 is a reflection nebula located in the northern constellation Perseus, positioned next to the southern constellation border with Taurus and Aries. It was first discovered by German astronomer Eduard Schönfeld in 1855. The nebula is visible as a hazy patch in a small telescope, while a larger aperture will show a pair of dark nebulae designated Barnard 1 and Barnard 2. It is associated with a dark cloud L1450. Estimates of the distance to this nebula range from 980–1,140 ly (300–350 pc).
NGC 5307 is a planetary nebula in the southern constellation of Centaurus, positioned less than 3° to the northeast of the star Epsilon Centauri. It was discovered by English astronomer John Herschel on April 15, 1836. The nebula is located at a distance of approximately 10.6 kilolight-years from the Sun. The central star, designated PNG 312.3+10.5, is a weak emission-line star, superficially similar to the WC subtype of Wolf–Rayet stars. It has a spectral class of O(H)3.5 V.
NGC 7354 is a planetary nebula located in the northern circumpolar constellation of Cepheus, at a distance of approximately 5.5 kly from the Sun. It was discovered by German-born astronomer William Herschel on November 3, 1787. John L. E. Dreyer described it as, "a planetary nebula, bright, small, round, pretty gradually a very little brighter middle".
NGC 3195 is a planetary nebula located in the southern constellation of Chamaeleon. It is the most southern of all the bright sizable planetary nebula in the sky, and remains concealed from all northern observers. Discovered by Sir John Herschel in 1835, this 11.6 apparent magnitude planetary nebula is slightly oval in shape, with dimensions of 40×35 arc seconds, and can be seen visually in telescopic apertures of 10.5 centimetres (4.1 in) at low magnifications.
NGC 6884 is a planetary nebula located in the constellation Cygnus, less than a degree to the southwest of the star Ο1 Cygni. It lies at a distance of approximately 12.5 kly from the Sun. The nebula was discovered on May 8, 1883, by American astronomer Edward C. Pickering.
WR 136 is a Wolf–Rayet star located in the constellation Cygnus. It is in the center of the Crescent Nebula. Its age is estimated to be around 4.7 million years and it is nearing the end of its life. Within a few hundred thousand years, it is expected to explode as a supernova.
S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros. It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.
NGC 6072 is a planetary nebulae in the southern constellation of Scorpius. It has a dynamical age of 104 years. Its circumstellar envelope is likely to be rich in carbon as it has very strong CN (cyanide) spectral lines. CN spectral lines are generally not detected in oxygen rich AGB (asymptotic giant branch) circumstellar envelopes. NGC 6072 also shows H2 (hydrogen) emission and intense CO (carbon monoxide) emission which has been mapped displaying bipolarity and some gas at high velocity. The evolution of this planetary nebulae is likely to be dominated by photodissociation and ion/radical molecular reactions. Shock chemistry is also likely to be important.
AB Aurigae is a young Herbig Ae star in the Auriga constellation. It is located at a distance of approximately 531 light years from the Sun based on stellar parallax. This pre-main-sequence star has a stellar classification of A0Ve, matching an A-type main-sequence star with emission lines in the spectrum. It has 2.4 times the mass of the Sun and is radiating 38 times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The radio emission from the system suggests the presence of a thermal jet originating from the star with a velocity of 300 km s−1. This is causing an estimated mass loss of 1.7×10−8 M☉ yr−1.
30 Monocerotis is a single star in the equatorial constellation of Hydra, located 122 light years away from the Sun. It has the Bayer designation C Hydrae; 30 Monocerotis is the Flamsteed designation and was assigned when it belonged to the Monoceros constellation. The object is visible to the naked eye as a white-hued star with an apparent visual magnitude of 3.90. It is moving away from the Earth with a heliocentric radial velocity of +10 km/s.
HD 259431 is a young stellar object in the constellation of Monoceros.
KH 15D, described as a winking star because of its unusual dips in brightness, is a binary T Tauri star system embedded in a circumbinary disk. It is a member of the young open cluster NGC 2264, located about 2,500 light-years (770 pc) from the Sun in the constellation of Monoceros.
HD 150193 is a binary star system in the constellation of Ophiuchus. The primary star was identified as a Herbig Ae/Be star with a strong solar wind, losing approximately a tenth of solar mass per million years. It does host a very small debris disk, likely due to disk truncation by the nearby stellar companion. The disk is inclined 38±9° to the plane of sky. It appears to be highly evolved and asymmetric, with indications of flattening and grains growth.
