Two intersecting circles with the larger circle split in one circle and a ring.

• Inventor: Dmitry Andreev
• Mechanism: Intersecting circles
• Patents: Unknown
• Producer: Custom
• Year: 2022
• Original Price: $0.00 USD
• Current Price: No Data

Epsilon Aurigae (ε Aurigae, abbreviated Epsilon Aur, ε Aur) is a multiple star system in the northern constellation of Auriga, the charioteer. It is an unusual eclipsing binary system comprising an F0 supergiant (officially named Almaaz /ælˈmɑːz/, the traditional name for the system) and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars. The distance to the system is still a subject of debate, but data from the Gaia spacecraft puts its distance at around 1,350±300 light years from Earth.

Epsilon Aurigae was first suspected to be a variable star when German astronomer Johann Heinrich Fritsch observed it in 1821. Later observations by Eduard Heis and Friedrich Wilhelm Argelander reinforced Fritsch's initial suspicions and attracted attention to the star. Hans Ludendorff, however, was the first to study it in great detail. His work revealed that the system was an eclipsing binary variable, a star that dims when its partner obscures its light.

About every 27 years, Epsilon Aurigae's brightness drops from an apparent visual magnitude of +2.92 to +3.83. This dimming lasts 640–730 days. In addition to this eclipse, the system also has a low amplitude pulsation with a non-consistent period of around 66 days.

Epsilon Aurigae's eclipsing companion has been subject to much debate since the object does not emit as much light as is expected for an object its size. As of 2008, the most popularly accepted model for this companion object is a binary star system surrounded by a massive, opaque disk of dust; theories speculating that the object is a large, semitransparent star or a black hole have since been discarded.

Nomenclature:
Richard Hinckley Allen reported that Oxford scholar Thomas Hyde recorded the traditional name Almaaz in his 1665 translation of the catalogue of Ulugh Beg, which he identified with the Arabic Al Maʽaz "the billy goat", corresponding to the name of the star Capella (Latin for "nanny goat"). Allen's spelling corresponds to the plural المعز al-maʽaz "goats". Allen also reported that medieval Persian astronomer Zakariya al-Qazwini knew it as Al Anz.
Ptolemy in the Almagest said that the star marked the charioteer's left elbow.

Nature of the system:
The nature of the Epsilon Aurigae system is unclear. It has long been known to consist of at least two components which undergo periodic eclipses with an unusual flat-bottomed dimming every 27 years. Early explanations with exceptionally large diffuse stars, black holes, and odd doughnut-shaped discs are no longer accepted. There are now two main explanations that can account for the known observed characteristics: a high mass model where the primary is a yellow supergiant of around 15 M☉; and a low mass model where the primary is about 2 M☉ and a less luminous evolved star.

Variations on the high mass model have always been popular, since the primary star is to all appearances a large supergiant star. Spectroscopically it is early F or late A with luminosity class Ia or Iab. Distance estimates consistently lead to luminosities expected for a bright supergiant, although there is a huge variation in published values for the distance. The Hipparcos parallax measurement has a margin of error as large as the value itself and so the derived distance is likely to be anything from 355 to 4,167 parsecs.
The Gaia Data Release 2 parallax is somewhat more precise, leading to a distance of 1,350±350 ly, towards the low end of estimates by other methods.
The main problem with the high mass model is the nature of the secondary, which is required by the known mass function to have a mass comparable to the primary, at odds with observations where it appears as a B-type main-sequence star. The secondary may be a close binary involving two lower-mass main sequence stars, or a more complex system.

The low mass model, recently popularised by the Citizen Sky project, proposes that the primary is an evolved asymptotic giant branch star of 2–4 M☉. This relies on distance and luminosity estimates lower than most observations. The star would be an unusually large and bright giant star for the given mass, possibly as the result of very high mass loss. To match the observed eclipse and orbital data, the secondary is a fairly normal B main sequence star of about 6 M☉ embedded in a thick disc seen nearly edge on.

The orbit itself is now fairly well determined, inclined at over 87 degrees to Earth. The primary and secondary are around 35 AU apart (in the high mass model), which is further than the planet Neptune from the Sun. In the low mass model, the separation is only 18 AU.

Visible component:
The ε Aurigae system during an eclipse (artist impression)
The visible component, Epsilon Aurigae A, is a semiregular pulsating post-asymptotic giant branch star belonging to the spectral class F0.
This F-type star has around 143 to 358 times the diameter of the Sun, and is 37,875 times as luminous. (Reliable sources vary considerably in their estimates of both quantities.) If the star were in the position of the Sun, it would envelop Mercury and possibly Venus. F-type stars like Epsilon Aurigae tend to glow white and display strong ionized calcium absorption lines and weak hydrogen absorption lines; being a class above the Sun (which is a G-type star), F-type stars are typically hotter than sunlike stars.

Eclipsing component:
The eclipsing component emits a comparatively insignificant amount of light, and cannot be directly seen in visible light. A heated region, however, has been discovered in the center of the object. It is widely thought to be a dusty disc surrounding a class B main sequence star. Modelling the spectral energy distribution for ε Aurigae as a whole produces the best fit with a B5V star at the centre of the disc. Such a star would have a mass around 5.9 M☉. The observed orbit, assuming a fairly normal F-type supergiant for the primary star, requires a secondary with a mass over 13 M☉. The low mass model accepts the 5.9 M☉ secondary and so also requires a low-mass primary. The high-mass model accepts a normal mass supergiant primary and argues for a pair of B-type stars, or an unusual single higher-mass star.

The disc around the secondary star is 3.8 AU wide, 0.475 AU thick, and blocks about 70% of the light passing through it, allowing some light from the primary star to be seen even during the eclipses. It radiates like a 550 K black body.

Observation:
The star is easily found because of its brightness and apparent proximity to the star Capella. It is the apex of the isosceles triangle forming the 'nose' of the constellation Auriga. The star is bright enough to be seen from most urban locations with moderate amounts of light pollution.

Visual variable star observers make an estimate of its brightness by comparing its brightness with nearby stars with a known brightness value. This can be done by interpolating the brightness of the variable between two comparison stars, or by individually estimating the magnitude difference between the variable and several different comparisons. Repeating the observation on different nights allows a light curve to be produced showing the variation in brightness of the star. In practice, visual variable star estimates from many observers are statistically combined to produce more accurate results.

The inventor designed it with hollow pieces and two sides with different colours.
Size: 132 x 142 mm
Weight: 165 grams

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