martinsastro

Astronomy for all.
Last additions - Martin
Lagoon.jpg
Lagoon.jpgLagoon nebula.714 viewsThe Lagoon Nebula is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90' by 40', translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binoculars or a telescope, human vision having poor color sensitivity at low light levels. The nebula contains a number of Bok globules - dark, collapsing clouds of protostellar material - the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that pours out ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the "Hourglass Nebula" (so named by John Herschel), which should not be confused with the better known Hourglass Nebula in the constellation of Musca. In 2006 the first four Herbig-Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it.MartinOct 19, 2010
IC443.jpg
IC443.jpgIC443.553 viewsIC 443 (also known as the Jellyfish Nebula and Sharpless 248 (Sh2-248)) is a Galactic supernova remnant (SNR) in the constellation Gemini. On the plan of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years (~5×1016 km) from Earth.
IC 443 is thought to be the remains of a supernova that occurred 3,000 - 30,000 years ago. The same supernova event likely created the neutron star CXOU J061705.3+222127, the collapsed remnant of the stellar core.
IC 443 is one of the best-studied cases of supernova remnants interacting with surrounding molecular clouds.
MartinOct 19, 2010
horsephotobucket.jpg
horsephotobucket.jpgHorsehead nebula.659 viewsThe Horsehead Nebula (also known as Barnard 33 in bright nebula IC 434) is a dark nebula in the constellation Orion. The nebula is located just below (to the south of) Alnitak, the star farthest left on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. The Horsehead Nebula is approximately 1500 light years from Earth. It is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which is similar to that of a horse's head when viewed from Earth. The shape was first noticed in 1888 by Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory.

The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.
MartinOct 19, 2010
good.jpg
good.jpgNGC6188575 viewsMartinOct 19, 2010
etaha-2.jpg
etaha-2.jpgEta Carinae in HA.578 viewsThis stellar system is currently one of the most massive that can be studied in great detail. Until recently, Eta Carinae was thought to be the most massive single star, but it was recently demoted to a binary system.[7] The most massive star in the Eta Carinae multiple star system has more than 100 times the mass of the Sun. Other known massive stars are more luminous and more massive.

Stars in the mass class of Eta Carinae, with more than 100 times the mass of the Sun, produce more than a million times as much light as the Sun. They are quite rare — only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach (or potentially exceed) the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in their radiation and gas.

Eta Carinae's chief significance for astrophysics is based on its giant eruption or supernova impostor event, which was observed around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova impostors have been seen in other galaxies, for example the false supernovae SN 1961v in NGC 1058[8] and SN 2006jc in UGC 4904,[9] which produced a false supernova, noted in October 2004. Significantly, SN 2006jc was destroyed in a supernova explosion two years later, observed on October 9, 2006.[10] The supernova impostor phenomenon may represent a surface instability[11] or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon, and after nearly 170 years the star's internal structure has not fully recovered.
MartinOct 19, 2010
etacrop.jpg
etacrop.jpgEta Carinae nebula.562 viewsThis stellar system is currently one of the most massive that can be studied in great detail. Until recently, Eta Carinae was thought to be the most massive single star, but it was recently demoted to a binary system.[7] The most massive star in the Eta Carinae multiple star system has more than 100 times the mass of the Sun. Other known massive stars are more luminous and more massive.

Stars in the mass class of Eta Carinae, with more than 100 times the mass of the Sun, produce more than a million times as much light as the Sun. They are quite rare — only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach (or potentially exceed) the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in their radiation and gas.

Eta Carinae's chief significance for astrophysics is based on its giant eruption or supernova impostor event, which was observed around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova impostors have been seen in other galaxies, for example the false supernovae SN 1961v in NGC 1058[8] and SN 2006jc in UGC 4904,[9] which produced a false supernova, noted in October 2004. Significantly, SN 2006jc was destroyed in a supernova explosion two years later, observed on October 9, 2006.[10] The supernova impostor phenomenon may represent a surface instability[11] or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon, and after nearly 170 years the star's internal structure has not fully recovered.
MartinOct 19, 2010
Eagle_done-1.jpg
Eagle_done-1.jpgEagle nebula.541 viewsThe Eagle Nebula is part of a diffuse emission nebula, or H II region, which is catalogued as IC 4703. This region of active current star formation is about 6,500 light-years distant. The tower of gas that can be seen coming off the nebula is approximately 57 trillion miles (97 trillion km) high.

The brightest star in the nebula has an apparent magnitude of +8.24, easily visible with good binoculars.
MartinOct 19, 2010
chickenHA.jpg
chickenHA.jpgChicken nebula.547 viewsIC 2944, also known as the Running Chicken Nebula or the Lambda Cen Nebula, is an open cluster with an associated emission nebula found in the constellation Centaurus, near the star Lambda Centauri. It features Bok globules and is most likely a site of active star formation.

The Hubble Space Telescope image on the right is a close up of Bok Globules discovered in IC 2944 by South African astronomer A. David Thackeray in 1950[2]. These globules are now known as Thackeray's Globules.
MartinOct 19, 2010
catspaw.jpg
catspaw.jpgCats paw nebula.812 viewsNGC 6334 (also known as the Cat's Paw Nebula , Bear Claw Nebula and Gum 64) is an emission nebula located in the constellation Scorpius.[2] It was discovered by astronomer John Herschel in 1837, who observed it from the Cape of Good Hope in South Africa.MartinOct 19, 2010
goodbugcrop.jpg
goodbugcrop.jpgBug nebula.408 viewsNGC 6302 (also called the Bug Nebula or Butterfly Nebula), is a bipolar planetary nebula in the constellation Scorpius. It is one of the most complex[clarification needed] planetary nebulae observed. The spectrum of NGC 6302 shows its central star is one of the hottest objects in the galaxy, with a surface temperature in excess of 200,000 K, implying that the star from which it formed must have been very large.

The central star has never been observed and is surrounded by a particularly dense equatorial disc composed of gas and dust. This dense disc is postulated to have caused the star's outflows to form a bipolar structure (Gurzadyan 1997), similar to an hour-glass. This bipolar structure shows many interesting features seen in planetary nebulae such as ionization walls, knots and sharp edges to the lobes.
MartinOct 19, 2010
dumbbellcrop.jpg
dumbbellcrop.jpgDumbbell nebula.477 viewsThe Dumbbell Nebula (also known as Messier 27, M 27, or NGC 6853) is a planetary nebula (PN) in the constellation Vulpecula, at a distance of about 1,360 light years.

This object was the first planetary nebula to be discovered; by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and its diameter of about 8 arcminutes, it is easily visible in binoculars, and a popular observing target in amateur telescopes.
MartinOct 19, 2010
Cheriocrop.jpg
Cheriocrop.jpgCherio nebula.444 viewsM57 is located in Lyra, south of its brightest star Vega. Vega is the northwestern vertex of the three stars of the Summer Triangle. M57 lies about 40% of the angular distance from β Lyrae to γ Lyrae.[5]

M57 is best seen through at least a 20 cm (8-inch) telescope, but even a 7.5 cm (3-inch) telescope will show the ring.[5] Larger instruments will show a few darker zones on the eastern and western edges of the ring, and some faint nebulosity inside the disk.

This nebula was discovered by Antoine Darquier de Pellepoix in January, 1779, who reported that it was "...as large as Jupiter and resembles a planet which is fading." Later the same month, Charles Messier independently found the same nebula while searching for comets. It was then entered into his catalogue as the 57th object. Messier and William Herschel also speculated that the nebula was formed by multiple faint stars that were unable to resolve with his telescope.[6][7]

In 1800, Count Friedrich von Hahn discovered the faint central star in the heart of the nebula. In 1864, William Huggins examined the spectra of multiple nebulae, discovering that some of these objects, including M57, displayed the spectra of bright emission lines characteristic of fluorescing glowing gases. Huggins concluded that most planetary nebulae were not composed of unresolved stars, as had been previously suspected, but were nebulosities.[8][9]
MartinOct 19, 2010
132 files on 11 page(s) 10