Sphingid ceratonia, maybe (APOD 2009 May 24 Carina Nebula)
Posted: Sun May 24, 2009 4:52 pm
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- The Silence of the Lambs (1991)
Roden: Sphingid ceratonia, maybe.
[cuts open cocoon]
Roden: Agent Starling, meet Mr. Acherontia styx.
Pilcher: Weird.
Roden: Better known to his friends as the Death's-head moth.
------------------------------------------------http://apod.nasa.gov/apod/ap090524.html wrote:
<<Carina nebula (NGC 3372) containing Eta Carinae.
Eta Carinae and its surrounding Homunculus Nebula are
the small, saturated (white) blob centered vertically in the image
and approximately 1/5 of the distance from left to right.>>
--------------------------------------------------------------------------------------------------------------http://www.stomptokyo.com/movies/godzilla-vs-mothra-64.html wrote: .
<<With the exception of the original Godzilla, Godzilla vs Mothra is
probably the high water mark of the Godzilla series of movies. The
film opens during a big storm that washes an even bigger egg on shore
in Japan. So what happens when an egg the size of an ocean liner
washes ashore? The local fisherman sell it to a huge company.
ConHugeCo then puts the egg on display, two bits a gander. This may be
the most realistic thing ever to happen in a Godzilla movie. But darn
it all, it's never that simple. No sooner has ConHugeCo got the egg
than two miniature fairy women (who represent the "powers of goodness
and light," or so they say) appeal to the company's officers to return
the egg to Infant Island. The egg is the progeny of the god of Infant
Island, the giant insect Mothra, last seen in 1961's Mothra.>>
http://en.wikipedia.org/wiki/Eta_Carinae
<<Eta Carinae (η Carinae or η Car) is a stellar system in the Carina constellation containing at least two stars, one of which is a luminous blue variable star. Its combined luminosity is about four million times that of the Sun and, with an estimated system mass of in excess of 100 solar masses. Because of its mass and the stage of life, it is expected to explode in a supernova in the astronomically near future.
Eta Carinae has the traditional names Tseen She (from the Chinese 天社 (Mandarin: tiānshè) "Heaven's altar") and Foramen.
This 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. The most massive star in the Eta Carinae multiple star system has less 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 imposter event, with its light travelling almost 8,000 light-years to reach us around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova imposters have been seen in other galaxies, for example the false supernovas SN 1961v in NGC 1058 and SN 2006jc in NGC 4904, 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. The supernova impostor phenomenon may represent a surface instability or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon, and after 160 years the star's internal structure has not fully recovered.
This object is located in the constellation Carina (right ascension 10 h 45.1 m, declination −59°41m), about 7,500 to 8,000 light-years from the Sun. It is not visible north of latitude 27°N and thus is circumpolar south of latitude 27°S.
Very large stars like Eta Carinae use up their fuel very quickly because of their disproportionately high luminosities. Eta Carinae is expected to explode as a supernova or hypernova some time within the next million years or so. As its current age and evolutionary path are uncertain, it could explode within the next several millennia or even in the next few years. LBVs such as Eta Carinae may be a stage in the evolution of the most massive stars; the prevailing theory now holds that they will exhibit extreme mass loss and become Wolf-Rayet Stars before they go supernova, if they are unable to hold their mass to explode as a hypernova.
It is possible that the Eta Carinae hypernova or supernova could affect Earth, about 7,500 light years away, but would not likely affect terrestrial humans directly, who will be protected from gamma rays by the atmosphere, as well from some other cosmic rays by the magnetosphere. The damage would likely be restricted to the upper atmosphere, the ozone layer, spacecraft, including satellites, and any astronauts in space, although a certain few claim that radiation damage to the upper atmosphere would have catastrophic effects as well. At least one scientist has claimed that when the star explodes, "it would be so bright that you would see it during the day, and you could even read a book by its light at night". A supernova or hypernova produced by Eta Carinae would probably eject a gamma ray burst (GRB) out on both polar areas of its rotational axis. Calculations show that the deposited energy of such a GRB striking the Earth's atmosphere would be equivalent to one kiloton of TNT per square kilometer over the entire hemisphere facing the star with ionizing radiation depositing ten times the lethal whole body dose to the surface. This catastrophic burst would probably not hit Earth, though, because the rotation axis does not currently point at us. If Eta Carinae is a binary system, this may affect the future intensity and orientation of the supernova explosion that it produces, depending on the circumstances.>>
-------------------------------------------------http://www.seds.org/messier/xtra/ngc/etacar.html wrote:
<<Eta Carinae is one of the most remarkable stars in the heavens.
This star was first cataloged by Edmond Halley in 1677, as a star of fourth magnitude. Since, its brightness has varied in a most remarkable way: In 1730, its brightness reached mag 2, and again fell to mag 4 in about 1782. It brightened again about 1801 and faded back to 4th magnitude in 1811. In 1820, Eta began to brighten steadily, reaching 2nd magnitude in 1822 and 1st mag in 1827. After this first preliminary maximum, the star faded back to mag 2 for about 5 years, then rose again to about mag 0. After a further slight decline, Eta's brightness incresed once more and reached its maximal brilliance of nearly -1.0 in April 1843, when it outshone all stars in the sky but Sirius. After this brilliant show, the star slowly faded continuously, and became invisible in 1868. Interrupted by two minor outbursts around 1870 and 1889, Eta Carinae faded to about 8th magnitude around 1900, where it remained until 1941. At that time, the star began to brighten again, and reached 7th magnitude about 1953. Slowly and steadily, Eta Carinae became brighter until about 6th magnitude in the early 1990s - the star reached naked-eye visibility again at that time. Then in 1998-99, the star suddenly brightened by about a factor two. This behavior is not fully understood at this time (early 2000), and it seems hard to predict how this remarcable variable will develop in the future.
Eta Carinae is one of the most massive stars in the universe, with probably more than 100 solar masses. It is about 4 million times brighter than our local star, making it also one of the most luminous stars known. Eta Carinae radiates 99 % of its luminosity in the infrared part of the spectrum, where it is the brightest object in the sky at 10-20 microns wavelength.
As such massive stars have a comparatively short expected lifetime of roughly 1 million years, Eta Carinae must have formed recently in the cosmic timescale; it is actually situated in the heavily star forming nebula NGC 3372, called the Great Carina Nebula, or the Eta Carinae Nebula. It will probably end its life in a supernova explosion within the next few 100,000 years (some astronomers speculate that this will occur even sooner).
Because of its high mass, Eta Carinae is highly unstable, and prone to violent outbursts. According to the current theory of stellar structure and evolution, this instability is caused by the fact that its high mass causes an extremely high luminosity. This leads to a high radiation presure at the star's "surface", which blows significant portions of the star's outlayers off into space, in a slow but violent eruption. Our image shows the nebula formed by the ejected material.
The last of these outbursts occurred between 1835 and 1855 and peaked in 1843, when despite its distance (7,500 to 10,000 light years away) Eta Carinae briefly became the second brightest star in the sky with an apparent magnitude -1.
The picture in this page is a combination of three different images taken in red, green, and blue light. The ghostly red outer glow surrounding the star is composed of the very fastest moving of the material which was ejected during the last century's outburst. This material, much of which is moving more than two million miles per hour, is largely composed of nitrogen and other elements formed in the interior of the massive star, and subsequently ejected into interstellar space.
The bright blue-white nebulosity closer in to the star also consists of ejected stellar material. Unlike the outer nebulosity, this material is very dusty and reflects starlight. The new data show that this structure consists of two lobes of material, one of which (lower left) is moving toward us and the other of which (upper right) is moving away. The knots of ejected material have sizes comparable to that of our solar system. The total mass of the ejecta from the last outburst is estimated to be two to three solar masses.
Previous models of such bipolar flows predict a dense disk surrounding the star which funnels the ejected material out of the poles of the system. In Eta Carinae, however, high velocity material is spraying out in the same plane as the hypothetical disk, which is supposed to be channeling the flow.
The rapidly moving ejected gas shows up in spectra of Eta Carinae by peculiarly shifted spectral lines, forming the so-called P Cygni profiles (named after P Cygni, one of the other few star of same type known in the Milky Way).>>
http://en.wikipedia.org/wiki/Eta_Carinae wrote:
<<One remarkable aspect of Eta Carinae is its changing brightness. It is currently classified as a luminous blue variable (LBV) binary star due to peculiarities in its pattern of brightening and dimming.
When Eta Carinae was first catalogued in 1677 by Edmond Halley, it was of the 4th magnitude, but by 1730, observers noticed it had brightened considerably, and was at that point one of the brightest stars in Carina. Subsequently it dimmed again, and by 1782 it appeared back to its former obscurity, but in 1820 it was observed growing in brightness again. By 1827, it had brightened more than tenfold, and reached its greatest brightness appearance in April 1843: with a magnitude of −0.8, it was the second brightest star in the night-time sky (after Sirius at 8.6 light years away), despite its enormous distance of 7,000–8,000 light-years. (To put the relationship in perspective, the relative brightness would be like comparing a candle (Sirius) at 14.5 meters (48 feet) to another light (Eta Carinae) on the horizon of our planet 10 kilometers (6 mi) away, which would appear almost as bright as the candle.)
Eta Carinae sometimes has large outbursts, the last one just around its maximum brightness, seen in 1841. The reason for these outbursts is not yet known. The most likely possibility is believed to be that they are caused by built-up radiation pressure from the star's enormous luminosity. After 1843, Eta Carinae's appearance faded away, and between about 1900 and 1940 it was only of the 8th magnitude: invisible to the naked eye.[9] Eta Carinae's sudden and unexpected doubled brightness was seen in 1998–1999. As of 2007 its light can be easily seen with the naked eye, because it is brighter than magnitude 5.
A "spectroscopic minimum" or "X-ray eclipse" appeared in 2003. Astronomers organized a large observing campaign, which included every available ground-based (e.g. CCD optical photometry) and space observatory, including major observations with the Hubble Space Telescope, the Chandra X-ray Observatory, the INTEGRAL Gamma-ray space observatory, and the Very Large Telescope. Primary goals of these observations were to determine if in fact Eta Carinae is a binary star; if so, to identify its companion star; to determine the physical mechanism behind the "spectroscopic minima"; and to understand their relation (if any) to the large scale eruptions of the 19th century.
There is good agreement between the X-rays light curve and the evolution of a wind-wind collision zone of a binary system. These results were complemented by new tests on radio wavelengths.
Spectrographic monitoring of Eta Carinae showed that some emission lines faded precisely every 5.52 years, and that this period was stable for decades. The star's radio emission, along with its X-ray brightness,) also drop precipitously during these "events" as well. These variations, along with ultra-violet observations gives very high probability for the scenario that Eta Carinae is actually a binary star, in which a hot, lower mass star revolves around η Carinae in a 5.52-year, highly eccentric elliptical orbit.
The ionizing radiation emitted by the secondary star in Eta Carinae is the major radiation source of the system. A large fraction of this radiation is absorbed by the primary stellar wind, mainly after it encounters the secondary wind and passes through a shock wave. The amount of absorption depends on the compression factor of the primary wind in the shock wave. The compression factor is limited by the magnetic pressure in the primary wind. The variation of the absorption by the post-shock primary wind with orbital phase changes the ionization structure of the circumbinary gas and can account for the radio light curve of Eta Car. Fast variations near periastron passage are attributed to the onset of the accretion phase.
The formerly clockwork regularity of the dimming was upset, as observed in 2008. Following the 5.52 year cycle, the star would have started its next dimming appearance, being seen in January 2009, but the pattern was noticed starting early in July 2008 by the southern Gemini Observatory in La Serena, Chile. Spectrographic measurements showed an increase in blue light from superheated helium, which was formerly assumed to occur with the wind shock. However, if the cause is a binary star, it would be located too far away at this point in time for the wind to interact in so significant a fashion. There is some debate about the cause of the recent event.>>
