segunda-feira, 24 de abril de 2017

Pyxis Nautica, a Bússola, fazendo as vezes de Mastro do Navio Argo, Argonavis


Olá!

Caro Leitor,
suponha que você está perdido
em meio à Floresta Amazônica....
O que você faz
para poder orientar-se?

Bem, primeiramente os céus estrelados
funcionam como nossa maior orientação,
nossa fantástica e natural bússola,
não é verdade?

Corre o risco, porém,
de você não conhecer os céus estrelados,
as constelações,
as estrelas mais ao norte e mais ao sul
e mais ao centro...

Agora imagine-se viajando, navegando
em um navio bem antigo.
e por mares nunca dantes navegados;
Imagine que você é o capitão
e bem conhece a orientação pelas estrelas, sim.
No entanto, será que todos seus marinheiros
e comandados seus
também saber ler as orientações trazidas pelas estrelas?
Talvez você vá precisar se munir
com um instrumento realmente espetacular:
uma Bússola!

Ainda pensando na imagem de um Navio
e de uma Bússola,
vamos encontrar uma pequena e tímida constelação
denominada enquanto Pyxis Nautica
(ou somente Pyxis), a Bússola,
e este pequeno nicho estelar
apresenta-se entremeado ao mastro
de Argonavis, o Navio Argo da antiguidade.
(Aliás, os antigos gregos 
denominavam este lugar
como Mastro
e, no século XIV,
 John Herschel  
- filho de William Herschel -
assim também designou,
porém caiu em desuso).



Stellarium





Pyxis parece ter sido inserida
pelo astrônomo francês Nicolas Louis La Caille
a partir de suas observações nos céus austrais
quando de sua estada no Cabo da Boa Esperança,
África do Sul.

O que nos parece bem paradoxal
é o fato de que o mesmo Lacaille 
que  criou Pyxis, a Bussola,
colocando-a entremeada ao Mastro,
resolveu partir o antigo e imenso Navio Argo
em três (ainda grandes) constelações
- Puppis, a Popa; Carina, a Quilha, e Vela!

Bem, penso que o Caro Leitor já bem percebeu
que não sou muito afeita 
à esta partição do belíssimo Argonavis....,
porque nossa visão a olho nú, à vista desarmada,
dos céus estrelados mais ao sul
visualiza esta constelação por inteiro, 
certamente,
o Navio Argo singrando mares nunca dantes navegados,
mares estelados,
e perdendo sua Proa
ao passar pelo Estreito de Bósforo
e ter pedras rolando e caindo e espatifando-se
sobre sua frente 
que ruma para o sul, 
sempre mais ao sul.

Alguns autores astrônomos
julgam que Pyxis, a Bússola,
é a menos importante constelação dos céus estrelados...

A bem da verdade,
mesmo em lugares de céus escuros e transparentes
e em noites sem a luminosidade da Lua,
mal podemos notar
as estrelas Alpha e Beta e Gamma Pyxidis
que formam uma espécie de agulha da Bússola.
Isso acontece por várias razões
e duas delas são:
a estrela mais luminosa 
vem na magnitude 3.68(Alpha Pyxidis)
e por estar mergulhada esta pequena constelação
 ao caminho leitoso
da Via Lactea
(assim como todo o Navio).




Stellarium

Stellarium




Mesmo sendo apresentada 
como uma constelação quase inexpressiva,
na direção de Pyxis
encontram-se objetos celestes bem interessantes
como 
- T Pyxidis, uma estrela 
"recurrent nova and nova remnant";
- NGC 2818, uma bela nebulosa planetária,
- NGC 2613, uma galáxia espiral,
- Pyxis Globular Cluster 
e ainda alguns outros objetos interessantes
contidos neste pequeno lugar
dos céus estrelados mais ao sul.

Hoje à noite, Caro Leitor,
vou aproveitar para buscar uma boa visão do Navio
e então iidentificar Pyxis, a Bússola.
Por que você também não faz o mesmo?
A visão dos céus a olho nú
é sempre uma imensa emoção!

Com um abraço estrelado,
Janine Milward




A BÚSSOLA

A bússola, mais conhecida pelos marinheiros como agulha, é sem dúvida o instrumento de navegação mais importante a bordo. Ela teve sua origem na China do século IV a.C. Sua adaptação e reconhecimento no Ocidente aconteceu cerca de 1.500 anos depois. A primeira referência deste instrumento na Europa aparece em um documento de 1190, chamado "De Naturis Rerum". As primeiras bússolas chinesas não utilizavam agulhas . Eram compostas por um prato quadrangular representando a Terra. O "indicador"(objeto que indica a direção), com forma de concha, era de pedra imantada e a base (prato), de bronze. Um círculo no centro do prato representava o céu e a base quadrada, a terra.










Foi Flávio Gioia que em 1302 alterou a bússola para ser usada a bordo, usando a agulha sobre um cartão com o desenho de uma rosa-dos-ventos. Os rumos ou as direções dos ventos têm origem na antigüidade. Na Grécia começaram com dois, quatro, oito e doze rumos. No início do século XVI surgem já 16 e na época do Infante D. Henrique já se usavam rosas-dos-ventos com 32 rumos. Primeiramente o rumo era associado à direção dos ventos e só mais tarde aos pontos cardeais. Em certas rosas-dos-ventos, no local que indicava o Leste, aparecia desenhada uma cruz que mostrava a direção da Terra Santa. A declinação de uma agulha é a diferença que uma bússola marca entre o norte geográfico e o norte magnético.










O cabo da concha indicava o sul. A concha é uma representação simbólica da Ursa Maior. A base continha caracteres chineses que assinalavam os oito pontos principais: norte, sul, leste, oeste, nordeste, noroeste, sudeste e sudoeste. A introdução da agulha aumentou a precisão da leitura. Foi nessa época que os chineses introduziram os primeiros marcadores e indicadores, elementos fundamentais da ciência moderna. A Lo Pan é um instrumento complexo, desenvolvido através dos séculos, pelos chineses, para que os praticantes pudessem fazer precisos cálculos de tempo e espaço em sua ciência. O cálculo da direção pode ser efetuado com uma Lo Pan ou com uma bússola normal. Não existe diferença. A Lo Pan apenas nos indica um cálculo mais preciso, e algumas facilidades em relação às direções e as características do local.










Ao longo do tempo veio a verificar-se que a declinação variava com o tempo e o lugar. Também foi D. João de Castro o primeiro a descobrir o desvio de uma agulha, ou seja, o efeito que massas de ferro próximas tem sobre uma bússola. Este efeito obrigou a cuidados com o posicionamento da bússola perto de peças da artilharia, âncoras e outros ferros. Esta foi uma das razões para que os morteiros, as caixas que protegem as bússolas, fossem, no início, de madeira.Durante o século XVI as bússolas portuguesas tinham, pelo menos desde 1537, um sistema de balança para manter o morteiro horizontal. O morteiro era colocado numa coluna de madeira, mais tarde de metal, a bitácula, à frente da roda do leme. A bitácula contêm um sistema chamado cardan que permite que o morteiro se mantenha na horizontal apesar das oscilações do barco.



 http://www.museutec.org.br/previewmuseologico/a_bussola.htm



Mario Jaci Monteiro - As constelações, Cartas Celestes




PYXIS NAUTICA, A BÚSSOLA

Ascensão Reta 8h26m / 4h26m   Declinação -17o.3 / -37o.0
Constelação formada por La Caille em 1752,
com as estrelas do mastro do Navio Argo.
Esta constelação é a menos interessante de todas as constelações. 
Pyxis é rodeada por Hydra, Puppis, Vela e Antlia.

- 6a. Edição do Atlas Celeste
de autoria de Ronaldo Rogério de Freitas Mourão,
Editora Vozes, Petrópolis, ano de 1986




Pyxis (Pyx), a Bússola, é uma constelação do hemisfério celestial sul. O genitivo, usado para formar nomes de estrelas, é Pyxidis. É uma das 14 constelações criadas pelo astrônomo francês Nicolas Louis de Lacaille no século XVIII.

As constelações vizinhas são HydraPuppisVela e Antlia.

Alpha Pyxidis (Alpha Pyxα Pyxidisα Pyx) is a giant star in the constellation Pyxis. It has a stellar classification of B1.5III and is a Beta Cephei variable. This star has more than ten times the mass of the Sun and is more than six times the Sun's radius. The surface temperature is 24,300 K and the star is about 10,000 times as luminous as the Sun.[3][4][7] Stars such as this with more than 10 solar masses are expected to end their life by exploding as a supernova.[10]

Stellarium


Beta Pyxidis (Beta Pyxβ Pyxidisβ Pyx) is a double star[3] located in the southern constellation Pyxis. It has an apparent visual magnitude of 3.954, making it the second brightest star in that faint constellation.
Based upon parallax measurements, the star is an estimated 420 light-years (128 parsecs) from the Earth.[1] The spectrum matches a bright giant or supergiant star of stellar classification G7Ib-II. The interferometer-measured angular diameter of this star is 2.05 ± 0.14 mas.[8] At its estimated distance, this yields a physical size of about 28 times the radius of the Sun.[6] The effective temperature of the star's outer envelope is about 5,400 K, giving it the characteristic yellow hue of a G-type star.[7][9]
In 2010, the star was among a survey of massive, lower effective temperature supergiants in an attempt to detect a magnetic field. This star may have a longitudinal magnetic field with a strength of less than a Gauss.[10] It is a young disk star system with space velocity components, [U, V, W] = [–11.0, +11.8, –2.2] km/s.[5] There is a magnitude 12.5 optical companion, located at an angular separation of 12.7 arcseconds and a position angle of 118° as of the year 1943.[11]

Stellarium




Gamma Pyxidis (Gamma Pyxγ Pyxidisγ Pyx) is a 4th magnitude star in the constellation Pyxis. It is classified as a giant star of composition similar to the Sun[7] with an estimated diameter 3.7 times that of the Sun.[8] It is located an estimated 207 light years from the Solar System.[4]
Gamma Pyxidis is moving through the Galaxy at a speed of 54.2 km/s relative to the Sun. Its projected Galactic orbit carries it between 21,300 and 30,700 light years from the center of the Galaxy.[9]

Stellarium




Hubble telescope picture of T Pyxidis, from a compilation of data taken on Feb. 26, 1994, and June 16, Oct. 7, and Nov. 10, 1995, by the Wide Field and Planetary Camera 2.
Tpyx hst big.jpg


T Pyxidis (T Pyx)[1] is a recurrent nova[2] and nova remnant in the constellation Pyxis. It is a binary star system and its distance is estimated at about 4,783 parsecs (15,600 light-years) from Earth. It contains a Sun-like star and a white dwarf. Because of their close proximity and the larger mass of the white dwarf, the latter draws matter from the larger, less massive star. The influx of matter on the white dwarf's surface causes periodic thermonuclear explosions to occur.
The usual apparent magnitude of this star system is 15.5, but there occurred eruptions with maximal apparent magnitude of about 7.0 in the years 1890, 1902, 1920, 1944, 1966 and 2011.[3] Evidence seems to indicate that T Pyxidis may have increased in mass despite the nova eruptions, and is now close to the Chandrasekhar limit when it might explode as a supernova.[4] When a white dwarf reaches this limit it will collapse under its own weight and cause a type 1a supernova.

Effect on Earth

Because of its relative proximity, some—in particular, Edward Sion, astronomer & astrophysicist at Villanova University, and his team therefrom—contend that a type 1a supernova could have a significant impact on Earth. The received gamma radiation would equal the total (all spectra) radiation of approximately 1,000 solar flares,[5] but the type Ia supernova would have to be closer than 1,000 parsecs (3,300 light-years) to cause significant damage to the ozone layer, and perhaps closer than 500 parsecs. The X-radiation that reaches Earth in such an event, however, would be less than the X-radiation of a single average solar flare.[5]
However, Sion's calculations were challenged by Alex Filippenko of the University of California at Berkeley who said that Sion had possibly miscalculated the damage that could be caused by a T Pyxidis supernova. He had used data for a far more deadly gamma-ray burst (GRB) occurring 1 kiloparsec from Earth, not a supernova, and T Pyxidis certainly is not expected to produce a GRB.[6] According to another expert, "[a] supernova would have to be 10 times closer [to Earth] to do the damage described."[6] Mankind survived when the Crab Nebula supernova went off at a distance of about 6,500 light-years in the year 1054. If this star were to explode as a type Ia supernova at its estimated distance of 3,300 light-years, it would have an apparent magnitude of around -9.3, about as bright as the brightest Iridium (satellite) flares.[7]
Recent data indicates his distance estimate is five times too close. Astronomers used NASA's Hubble Space Telescope to observe the light emitted during its latest outburst in April 2011. The team also used the light echo to refine estimates of the nova's distance from Earth. The new distance is 15,600 light-years (4780 pc) from Earth. Previous estimates were between 6,500 and 16,000 light-years (2000 and 4900 pc).[8]
It has been reported that T Pyx would "soon" become a supernova.[4] However, when contacted by Scientific American, it became apparent that "soon" was meant in astronomical terms: Dr. Sion said that "soon" in the press announcement meant "[a]t the accretion rate we derived, the white dwarf in T Pyxidis will reach the Chandrasekhar Limit in ten million years."[9] By that time it will have moved far enough away from the solar system to have little effect.
AAVSO light curve of recurrent nova T Pyx from 1 Jan 1966 to 17 Nov 2010. Up is brighter and down is fainter. Day numbers are Julian days. Different colors reflect different bandpasses.

2011 Outburst

Mike Linnolt has detected T Pyx first outburst in nearly 45 years. He detected it on April 14, 2011 at magnitude 13.[3] According to AAVSO observers, it reached magnitude 7.5 in the visual and V bands by April 27,[10]and reached magnitude 6.8 by May 3.[11]
AAVSO light curve of recurrent nova T Pyx from April 13 to May 6, 2011. Up is brighter and down is fainter.

X-ray source


T Pyxidis is a super soft X-ray source.[12]


nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae. Over their short lifetimes, this novae shell shows expansion velocities are around 1000 km/s[1], whose faint nebulosity usually are illuminated by their progenitor stars via light echos as observed with the spherical shell[1] of Nova Persei 1901[2] or the energies remaining in the expanding bubbles like T Pyxidis.[3]
As most novae require a close binary system, with a white dwarf and main sequence, sub-giant; or the merging of two red dwarfs; so probably all novae remnants must be associated with binaries[4]. This theortically means these nebulae shapes might be affected by their central progenitor stars and the amount of matter ejected by novae.[1]Shapes of these novae nebulae is of much interest to modern astrophysicists.[1][4]


nova (plural novae or novas) or classical nova (CN or plural CNe) is an astronomical event that causes the sudden appearance of a bright "new" star, that slowly fades from view over several weeks or many months. Novae should not be confused with other more energetic astronomical phenomena known as supernovae (SNe), which catastrophically destroys massive stars or white dwarfs.
..............................................................
Recurrent novae (RNe) are objects that have been seen to experience multiple nova eruptions. There are some ten known galactic recurrent novae.[16] The recurrent nova typically brightens by about 8.6 magnitude, whereas a classic nova brightens by more than 12 magnitude.[16] 



T Pyxidis in outburst on April 15th. North is up. See before-and-after animation.
Ernesto Guido and Giovanni Sostero




The recurrent nova T Pyxidis, which had its last outburst in December 1966 and has been very overdue for its next, finally began a new flareup on April 14th. By the next day it had brightened to about magnitude 8.4. In 1966–67 it reached 6.5 within about a month, and now it has done so again.
Here's a blink animation showing before and after, courtesy Ernesto Guido and Giovanni Sostero in Italy. South is up.
The star is in the dim constellation Pyxis east of Puppis and Canis Major, sinling out of sight for northern observers in May. (Here are finder and comparison-star charts from Sky & Telescope. For larger-scale comparison-star charts, you can use the chart-making site of the American Association of Variable Star Observers).
More information on T Pyx. Old but good AAVSO article. Current AAVSO observing campaign page.
As a white dwarf accreting mass from a binary partner, T Pyx is a prime candidate to explode completely as a Type Ia supernova within the next 10 million years. Last year, careless reporting led to a flurry of media buzz that if it blows up soon it could endanger Earth. Not so. At its distance of about 3,000 light-years, T Pyx would shine as brightly as magnitude –9 if it went Type Ia (as bright as a thick crescent Moon), but its radiation wouldn't harm us. The current Wikipedia article on T Pyx explains this story well.
In its past known outbursts (1890, 1902, 1920, 1944, and 1966), T Pyx took about 20 days to reach 7th magnitude or so and remained 8th mag or brighter for about two months.
Elaborating on this, Bradley Schaefer writes: "Judging from the 1967 eruption light curve, the current eruption light curve will... slowly rise to a peak near V=6.4 around 20 May, slowly fade to V=10 by middle August, then have a sudden drop by two magnitudes over the next 20 days (with drop being invisible due to the Sun). The 1967 eruption did show fast intra-night variations, but the old data does not have the time resolution to tell what is going on."
UPDATE May 13: As T Pyx disappears to the twilight horizon for Northern Hemisphere observers, it has brightened to magnitude 6.5 as of last night according to various observers reporting to the AAVSO. Here are recent observations and a light curve for the most recent 50 days.



Pyxis constellation map.svg
https://pt.wikipedia.org/wiki/Pyxis#/media/File:Pyxis_constellation_map.svg



The text is in the public domain.
[image ALT: a blank space]
http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Pyxis*.html
p348Pyxis Nautica, the Mariner's Compass.
Pyxis was formed by La Caille from stars in the Mast of Argo, and so associated with the Ship, although there, of course, it is an anachronism.
Baily reannexed it to Argo, since four of its members had been placed by Ptolemy where La Caille found them, so that for a time it fell into disuse; but Gould inserted it in his Uranometria Argentina of 1879, with sixty-six stars from 3.8 to 7th magnitudes.






Stellarium



Pyxis (/ˈpɪkss/Latin for a small medicinal box) is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas Louis de Lacaille in the 18th century, and is counted among the 88 modern constellations. The constellation is located close to those forming the old constellation of the ship Argo Navis, and in the 19th century astronomer John Herschel suggested renaming Pyxis to Malus, the mast, but the suggestion was not followed. Pyxis is completely visible from latitudes south of 53 degrees north, with its best evening-sky visibility in February and March.
The plane of the Milky Way passes through Pyxis. A faint constellation, its three brightest stars—AlphaBeta and Gamma Pyxidis—are in a rough line. At magnitude 3.68, Alpha is the constellation's brightest star. It is a blue-white star around 22,000 times as luminous as the Sun. Near Alpha is T Pyxidis, a recurrent nova that has flared up to magnitude 7 every few decades. Three star systems have planets, all discovered by doppler spectroscopy.

History

In ancient Chinese astronomy, Alpha, Beta and Gamma Pyxidis formed part of Tianmiao, a celestial temple honouring the ancestors of the emperor, along with stars from neighbouring Antlia.[1]
The French astronomer Nicolas Louis de Lacaille first described the constellation in French as la Boussole (the Marine Compass) in 1752,[2][3] after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised the Age of Enlightenment.[a] Lacaille Latinised the name to Pixis [sic] Nautica on his 1763 chart.[4] The Ancient Greeks identified the four main stars of Pyxis as the mast of the great ship Argo Navis.[5]
German astronomer Johann Bode defined the constellation Lochium Funis, the Log and Line—a nautical device once used for measuring speed and distance travelled at sea—around Pyxis in his 1801 star atlas, but the depiction did not survive.[6] In 1844 John Herschel attempted to resurrect the classical configuration of Argo Navis by renaming it Malus the Mast, a suggestion followed by Francis Baily, but Benjamin Gould restored Lacaille's nomenclature.[4]

Characteristics

Covering 220.8 square degrees and hence 0.535% of the sky, Pyxis ranks 65th of the 88 modern constellations by area.[7] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 52°N.[7][b] It is most visible in the evening sky in February and March.[8] A small constellation, it is bordered by Hydra to the north, Puppis to the west, Vela to the south, and Antlia to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Pyx'.[9] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of eight sides (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 8h 27.7m and 9h 27.6m, while the declination coordinates are between −17.41° and −37.29°.[10]

Features

Stars

Lacaille gave Bayer designations to ten stars now named Alpha to Lambda Pyxidis, skipping the Greek letters iota and kappa. Although a nautical element, the constellation was not an integral part of the old Argo Navis and hence did not share in the original Bayer designations of that constellation, which were split between Carina, Vela and Puppis.[4] Pyxis is a faint constellation, its three brightest stars—AlphaBeta and Gamma Pyxidis—form a rough line.[11] Overall, there are 41 stars within the constellation's borders with apparent magnitudes brighter than or equal to 6.5.[c][7]
With an apparent magnitude of 3.68, Alpha Pyxidis is the brightest star in the constellation.[13] Located 880 ± 30 light-years distant from Earth,[14] it is a blue-white giant star of spectral type B1.5III that is around 22,000 times as luminous as the Sun and has 9.4 ± 0.7 times its diameter. It began life with a mass 12.1 ± 0.6 times that of the Sun, almost 15 million years ago.[15] Its light is dimmed by 30% due to interstellar dust, so would have a brighter magnitude of 3.31 if not for this.[13] The second brightest star at magnitude 3.97 is Beta Pyxidis, a yellow bright giant or supergiant of spectral type G7Ib-II that is around 435 times as luminous as the Sun,[16] lying 420 ± 10 light-years distant away from Earth.[14] It has a companion star of magnitude 12.5 separated by 9 arcseconds.[17] Gamma Pyxidis is a star of magnitude 4.02 that lies 207 ± 2 light-years distant.[14] It is an orange giant of spectral type K3III that has cooled and swollen to 3.7 times the diameter of the Sun after exhausting its core hydrogen.[18]
Kappa Pyxidis was catalogued but not given a Bayer designation by Lacaille, however Gould felt the star was bright enough to warrant a letter.[4] Kappa has a magnitude of 4.62 and is 560 ± 50 light-years distant.[14]An orange giant of spectral type K4/K5III,[19] Kappa has a luminosity approximately 965 times that of the Sun.[16] It is separated by 2.1 arcseconds from a magnitude 10 star.[20] Theta Pyxidis is a red giant of spectral type M1III and semi-regular variable with two measured periods of 13 and 98.3 days, and an average magnitude of 4.71,[21] and is 500 ± 30 light-years distant from Earth.[14] It has expanded to approximately 54 times the diameter of the Sun.[18]
An image of a central white object surrounded by white and pale blue markers signifying material in a shell-like pattern around it
Hubble Space Telescope picture of T Pyxidis, showing ejected material from past eruptions
Located around 4 degrees northeast of Alpha is T Pyxidis,[22] a binary star system composed of a white dwarf with around 0.8 times the Sun's mass and a red dwarf that orbit each other every 1.8 hours. This system is located around 15,500 light-years away from Earth.[23] A recurrent nova, it has brightened to the 7th magnitude in the years 1890, 1902, 1920, 1944, 1966 and 2011 from a baseline of around 14th magnitude. These outbursts are thought to be due to the white dwarf accreting material from its companion and ejecting periodically.[24]
TY Pyxidis is an eclipsing binary star whose apparent magnitude ranges from 6.85 to 7.5 over 3.2 days.[25] The two components are both of spectral type G5IV with a diameter 2.2 times,[26] and mass 1.2 times that of the Sun, and revolve around each other every 3.2 days.[27] The system is classified as a RS Canum Venaticorum variable, a binary system with prominent starspot activity,[25] and lies 184 ± 5 light-years away.[14] The system emits X-rays, and analysing the emission curve over time led researchers to conclude that there was a loop of material arcing between the two stars.[28] RZ Pyxidis is another eclipsing binary system, made up of two young stars less than 200,000 years old. Both are hot blue-white stars of spectral type B7V and are around 2.5 times the size of the Sun. One is around five times as luminous as the Sun and the other around four times as luminous.[29] The system is classified as a Beta Lyrae variable, the apparent magnitude varying from 8.83 to 9.72 over 0.66 days.[30] XX Pyxidis is one of the more-studied members of a class of stars known as Delta Scuti variables[31]—short period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study astroseismology.[32] Astronomers made more sense of its pulsations when it became clear that it is also a binary star system. The main star is a white main sequence star of spectral type A4V that is around 1.85 ± 0.05 times as massive as the Sun. Its companion is most likely a red dwarf of spectral type M3V, around 0.3 times as massive as the Sun. The two are very close—possibly only 3 times the diameter of the Sun between them—and orbit each other every 1.15 days. The brighter star is deformed into an egg shape.[31]
AK Pyxidis is a red giant of spectral type M5III and semi-regular variable that varies between magnitudes 6.09 and 6.51.[33] Its pulsations take place over multiple periods simultaneously of 55.5, 57.9, 86.7, 162.9 and 232.6 days.[21] UZ Pyxidis is another semi-regular variable red giant, this time a carbon star, that is around 3560 times as luminous as the Sun with a surface temperature of 3482 K, located some 2116 light-years away from Earth.[16] It varies between magnitudes 6.99 and 7.83 over 159 days.[34] VY Pyxidis is a BL Herculis variable (type II Cepheid), ranging between apparent magnitudes 7.13 and 7.40 over a period of 1.24 days.[35] Located around 650 light-years distant, it shines with a luminosity approximately 45 times that of the Sun.[16]
The closest star to Earth in the constellation is Gliese 318, a white dwarf of spectral class DA5 and magnitude 11.85.[36] Its distance has been calculated to be 26 light-years,[37] or 28.7 ± 0.5 light-years distant from Earth. It has around 45% of the Sun's mass, yet only 0.15% of its luminosity.[38] WISEPC J083641.12-185947.2 is a brown dwarf of spectral type T8p located around 72 light-years from Earth. Discovered by infrared astronomy in 2011, it has a magnitude of 18.79[39]

Planetary systems

Pyxis is home to three stars with confirmed planetary systems—all discovered by doppler spectroscopy. A hot JupiterHD 73256 b, that orbits HD 73256 every 2.55 days, was discovered using the CORALIE spectrograph in 2003. The host star is a yellow star of spectral type G9V that has 69% of our Sun's luminosity, 89% of its diameter and 105% of its mass. Around 119 light-years away, it shines with an apparent magnitude of 8.08 and is around a billion years old.[40] HD 73267 b was discovered with the High Accuracy Radial Velocity Planet Searcher (HARPS) in 2008. It orbits HD 73267 every 1260 days, a 7 billion year-old star of spectral type G5V that is around 89% as massive as the Sun.[41] A red dwarf of spectral type M2.5V that has around 42% the Sun's mass, Gliese 317 is orbited by two gas giant planets. Around 50 light-years distant from Earth, it is a good candidate for future searches for more terrestrial rocky planets.[42]

Deep sky objects

Pyxis lies in the plane of the Milky Way, although part of the eastern edge is dark, with material obscuring our galaxy arm there. NGC 2818 is a planetary nebula that lies within a dim open cluster of magnitude 8.2.[43] NGC 2818A is an open cluster that lies on line of sight with it.[44] K 1-2 is a planetary nebula whose central star is a spectroscopic binary composed of two stars in close orbit with jets emanating from the system. The surface temperature of one component has been estimated at as high as 85,000 K.[45]NGC 2627 is an open cluster of magnitude 8.4 that is visible in binoculars.[44]
Discovered in 1995,[46] the Pyxis globular cluster is a 13.3 ± 1.3 billion year-old globular cluster situated around 130,000 light-years distant from Earth and around 133,000 light-years distant from the centre of the Milky Way—a region not previously thought to contain globular clusters.[47] Located in the galactic halo, it was noted to lie on the same plane as the Large Magellanic Cloud and the possibility has been raised that it might be an escaped object from that galaxy.[46]
NGC 2613 is a spiral galaxy of magnitude 10.5 which appears spindle-shaped as it is almost edge-on to observers on Earth.[48] Henize 2-10 is a dwarf galaxy which lies some 30 million light-years away. It is notable for having a black hole around a million solar masses at its centre. Known as a starburst galaxy due to very high rates of star formation, it has a bluish colour due to the huge numbers of young stars within it.[49]
https://en.wikipedia.org/wiki/Pyxis





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NGC 2658 é um aglomerado aberto na direção da constelação de Pyxis. O objeto foi descoberto pelo astrônomo James Dunlop em 1826, usando um telescópio refletor com abertura de 9 polegadas. Devido a sua moderada magnitude aparente (+9,2), é visível apenas com telescópios amadores ou com equipamentos superiores.





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NGC 2627 é um aglomerado aberto na direção da constelação de Pyxis. O objeto foi descoberto pelo astrônomo William Herschel em 1793, usando um telescópio refletor com abertura de 18,6 polegadas. Devido a sua moderada magnitude aparente (+8,4), é visível apenas com telescópios amadores ou com equipamentos superiores.






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Nestled Within
The unique planetary nebula NGC 2818 is nested inside the open star cluster NGC 2818A. Both the cluster and the nebula reside over 10,000 light-years away, in the southern constellation Pyxis (the Compass).

NGC 2818 is one of very few planetary nebulae in our galaxy located within an open cluster. Open clusters, in general, are loosely bound and they disperse over hundreds of millions of years. Stars that form planetary nebulae typically live for billions of years. Hence, it is rare that an open cluster survives long enough for one of its members to form a planetary nebula. This open cluster is particularly ancient, estimated to be nearly one billion years old.

Planetary nebulae fade away gradually over tens of thousands of years. The hot, remnant stellar core of NGC 2818 will eventually cool off for billions of years as a white dwarf. Our own sun will undergo a similar process, but not for another 5 billion years or so.

This Hubble image was taken in November 2008 with the Wide Field Planetary Camera 2. The colors in the image represent a range of emissions coming from the clouds of the nebula: red represents nitrogen, green represents hydrogen, and blue represents oxygen.

Image Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)
 

NGC 2818 é uma nebulosa planetária situada na constelação austral de Pyxis. Grande parte da nebulosa é constituída pelos gases expulsos pelas camadas exteriores de uma estrela no final da sua vida. Esta estrela é uma anã branca situada no centro da nebulosa.
Amiúde é citado como um membro de um aglomerado estelar aberto,[3] porém, as diferenças entre a velocidade radial da nebulosa planetária e este cúmulo aberto sugestionam um alinhamento aparente dos dois astros provocado apenas pela nossa posição no espaço. O caso é outro exemplo de um par superposto, unindo-se ao famoso caso de NGC 2438 e M46.
Em parte devido à sua pequena massa total, os aglomerados estelares abertos apresentam uma coesão relativamente pobre. Em consequência, os aglomerados estelares abertos tendem a ficar dispersos após um tempo relativamente curto, normalmente de cerca de 10 milhões de anos, devido a influências gravitativas externas além de outros fatores. Em condições excepcionais, os aglomerados abertos podem permanecer intatos até 100 milhões de anos.
Os modelos teóricos predizem que as nebulosas planetárias se podem formar por estrelas da sequência principal dentre 1 e 8 massas solares, o qual põe a sua idade em 40 milhões de anos ou mais. Embora haja poucas centenas de cúmulos abertos a conhecer nessa categoria de idade, várias razões limitam as possibilidades de encontrar um membro de um aglomerado estelar aberto numa fase de nebulosa planetária. Uma delas é que a fase de nebulosa planetária das estrelas mais massivas que pertencem a grupos mais novos é apenas da ordem de milhares de anos. Até a data, nenhuma associação verdadeira foi estabelecida entre os aglomerados estelares abertos e as nebulosas planetárias.







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VIMOS photo of NGC 2613, a spiral galaxy that resembles our own Milky Way. Composite VRI image obtained on February 28, 2002

NGC 2613 é uma galáxia espiral (Sb) localizada na direcção da constelação de Pyxis. Possui uma declinação de -22° 58' 22" e uma ascensão recta de 8 horas, 33 minutos e 22,8 segundos.
A galáxia NGC 2613 foi descoberta em 20 de Novembro de 1784 por William Herschel.

NGC 2613 (captured by ESO's 1.5-metre Danish telescope).jpg
By ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen, C. Thöne and C. Féron - http://www.eso.org/gallery/v/ESOPIA/Galaxies/ESO-2613_cc.tif.html (TIFF image), CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=8324169
ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen, C. Thöne and C. Féron - http://www.eso.org/gallery/v/ESOPIA/Galaxies/ESO-2613_cc.tif.html (TIFF image)




The Pyxis globular cluster is a globular cluster in the constellation Pyxis. It lies around 130,000 light-years distant from earth and around 133,000 light-years distant from the centre of the Milky Way—a distance not previously thought to contain globular clusters. It is around 13.3 ± 1.3 billion years old.[1] Discovered in 1995 by astronomer Rainer Wienberger while he was looking for planetary nebulae, it is in the Galactic halo. Irwin and colleagues noted that it appears to lie on the same plane as the Large Magellanic Cloud and raised the possibility that it might be an escaped object from that galaxy.[2]

Pyxis globular cluster
Observation data (J2000 epoch)
ConstellationPyxis
Right ascension09h 07m 57.80s
Declination–37° 13′ 17.0″
Distance130,000 light-years[1]
Physical characteristics
Metallicity = -1.20 ± 0.15[1]dex
Estimated age13.3 ± 1.3 Gyr[1]
Other designationsPyxis globular cluster
https://en.wikipedia.org/wiki/Pyxis_globular_cluster


globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is derived from the Latin globulus—a small sphere. A globular cluster is sometimes known more simply as a globular.
Globular clusters are found in the halo of a galaxy and contain considerably more stars and are much older than the less dense open clusters, which are found in the disk of a galaxy. Globular clusters are fairly common; there are about 150[2] to 158[3] currently known globular clusters in the Milky Way, with perhaps 10 to 20 more still undiscovered.[4] These globular clusters orbit the Galaxy at radii of 40 kiloparsecs (130,000 light-years) or more.[5] Larger galaxies can have more: Andromeda Galaxy, for instance, may have as many as 500.[6] Some giant elliptical galaxies (particularly those at the centers of galaxy clusters) such as M87,[7]have as many as 13,000 globular clusters.
Every galaxy of sufficient mass in the Local Group has an associated group of globular clusters, and almost every large galaxy surveyed has been found to possess a system of globular clusters.[8] The Sagittarius Dwarf galaxy and the disputed Canis Major Dwarf galaxy appear to be in the process of donating their associated globular clusters (such as Palomar 12) to the Milky Way.[9] This demonstrates how many of this galaxy's globular clusters might have been acquired in the past.
Although it appears that globular clusters contain some of the first stars to be produced in the galaxy, their origins and their role in galactic evolution are still unclear. It does appear clear that globular clusters are significantly different from dwarf elliptical galaxies and were formed as part of the star formation of the parent galaxy rather than as a separate galaxy.[10]


The galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of galaxies comprise the halo:
The distinction between the halo and the main body of the galaxy is clearest in spiral galaxies, where the spherical shape of the halo contrasts with the flat disc. In an elliptical galaxy, there is no sharp transition between the body of the galaxy and the halo.


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Os desenhos formados pelas estrelas
 - AS CONSTELAÇÕES - 
são como janelas que se abrem para a infinitude do universo 
e que possibilitam nossa mente a ir percebendo que existe mais, bem mais, 
entre o céu e a terra..., 
bem como percebendo que o caos, 
vagarosamente, 
vai se tornando Cosmos 
e este por nossa mente sendo conscientizado.

Quer dizer, 
nossa mente é tão infinita quanto infinito é o Cosmos.

Com um abraço estrelado,
Janine Milward