First Empire

Primary of Khado.

HD 4628 (96 G. Piscium) is a main sequence dwarf star star in the constellation Pisces. It has a spectral classification of K2, giving it an orange-red hue and a slightly smaller mass and girth than our Sun. It lies at a distance of approximately 24 light years from us and has a relatively high proper motion. The apparent magnitude is just sufficient for this star to be viewed with the unaided eye. The star appears to be slightly older than our Sun—approximately 5.4 billion years old.

Primary of New Pavonis.

The two brightest components of this system, Gl 667 A and Gl 667 B, are orbiting each other at an average angular separation of 1.81 arcseconds with a high eccentricity of 0.58. At the estimated distance of this system, this is equivalent to a physical separation of about 12.6 AU, or nearly 13 times the separation of the Earth from the Sun. Their eccentric orbit brings the pair as close as about 5 AU to each other, or as distant as 20 AU, corresponding to an eccentricity of 0.6. This orbit takes approximately 42.15 years to complete and the orbital plane is inclined at an angle of 128° to the line of sight from the Earth. The third component, Gl 667 C, orbits the Gl 667 AB pair at an angular separation of about 30", which equates to a physical separation of about 56 to 215 AU.

The largest component of this system, Gliese 667 A (GJ 667 A), is a K-type main-sequence star of stellar classification K3 V. It has about 73% of the mass of the Sun and 76% of the Sun's radius, but is radiating only around 12 or 13% of the luminosity of the Sun. The concentration of elements other than hydrogen and helium, what astronomers term the star's metallicity, is much lower than in the Sun with a relative abundance of around 26% solar. The apparent visual magnitude of this star is 6.29, which, at the star's estimated distance, gives an absolute magnitude of around 7.07 (assuming negligible extinction from interstellar matter).

Like the primary, the secondary component Gliese 667 B (GJ 667 B) is a K-type main-sequence star, although it has a slightly later stellar classification of K5V. This component has a mass of about 69% of the Sun, or 95% of the primary's mass, and it is radiating about 5% of the Sun's visual luminosity. The secondary's apparent magnitude is 7.24, giving it an absolute magnitude of around 8.02.

Gliese 667 C is the smallest stellar component of this system, with only around 31% of the mass of the Sun and 42% of the Sun's radius. It is a red dwarf with a stellar classification of M1.5. This star is radiating only 1.4% of the Sun's luminosity from its outer atmosphere at a relatively cool effective temperature of 3,700 K. This temperature is what gives it the red-hued glow that is a characteristic of M-type stars. The apparent magnitude of this component is 10.25, giving it an absolute magnitude of about 11.03. It is known to have a planetary system of two planets with a third planet as a strong possibility.

From the surface of Gliese 667 Cc, the second planet out that orbits along the middle of the habitable zone, Gliese 667 C would have an angular diameter of 1.24 degrees and would appear to be 2.3 times the visual diameter of our Sun, as it appears from the surface of the Earth. Gliese 667 C would have a visual area 5.4 times greater than that of the Sun but would still only occupy 0.003 percent of Gliese 667 Cc's sky sphere or 0.006 percent of the visible sky when directly overhead.

Two extrasolar planets, Gliese 667 Cb (GJ 667 Cb) and Gliese 667 Cc (GJ 667 Cc), have been found orbiting Gliese 667 C. The planets have masses of at least 6.0 and 3.9 times the mass of Earth, respectively, (and are thus classified as super-Earths). Planet Cb has an orbital period of approximately one week at a semimajor axis of 0.05 AU, while planet Cc orbits the star every four weeks at a distance of 0.1235 AU.

Planet Cb was first announced by the HARPS group on 19 October 2009, together with 29 other planets, while Cc was first mentioned in a pre-print made public on 21 November 2011, claiming that a discovery paper from the same group was in preparation. However, the announcement of a refereed journal report came on 2 February 2012 by researchers at the Carnegie Institution for Science/University of Göttingen. In this announcement, GJ 667 Cc was described as one of the best candidates yet found to harbor liquid water, and thus, potentially, support life on its surface. A detailed orbital analysis and refined orbital parameters for Gliese 667 Cc were presented. Based on GJ 667 C's bolometric luminosity, GJ 667 Cc should receive 0.90 times as much sunlight as Earth does, placing it squarely in the habitable zone.

Preliminary radial-velocity measurements indicate the presence of an additional super-Earth candidate (Gliese 667 Cd), orbiting in an "extended habitable zone" where large quantities of CO2 and other greenhouse gases may make life possible (a planet similar to Gliese 581 d). However, this candidate is less certain due to the similarity of the period to very strong periodicities detected in several activity indices, meaning that the radial velocity signal could be caused by stellar parameters. Its phase sampling is also sparse, causing severe aliasing and potential confusion. Another likely period for this same candidate would be 91 days.

An additional, long-period signal was found in the data. While the trend is largely consistent with the star's orbit around the A/B primary, a minor curvature in the trend suggests that the object may have a shorter period. A preliminary solution of 7100 days was achieved, consistent with a roughly Saturn-mass planet, but a longer time baseline will be needed to differentiate between the two solutions.

Primary of Susanowo.

Gliese 892 is a main sequence star in the constellation of Cassiopeia. It is smaller and less luminous than our Sun, with a spectral class of K3V, which makes it an orange-red hued star. Gl. 892 is relatively close to our system, with an estimated distance of 21.25 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers.

This star has a magnitude 9.4 companion at an angular separation of 106.6 arcseconds.

Primary of Itzamma.

It is a subgiant of spectral type G8 IV, meaning it is about to stop fusing hydrogen in its core and is starting the process of becoming a red giant. Because of that, Delta Pavonis is 22% brighter than the Sun even though the effective temperature of its outer atmosphere is lower, at 5,604 K. It has 99.1% of the Sun's mass and 122% of the Sun's radius. The surface convection zone extends downward to about 43.1% of the star's radius, but only contains 4.8% of the star's mass.

Spectroscopic examination of this star shows that it has a higher abundance of elements heavier than helium (or metallicity, as astronomers call it) than does the Sun. This value is typically given in terms of the relative ratio of iron (chemical symbol Fe) to hydrogen (H) as compared to the Sun's atmosphere.

The age of this star is in the range of 6.6–6.9 billion years old, and the star's luminosity has increased 60% since it became a zero-age main sequence star. It appears to be rotating slowly with a projected rotational velocity of 1.0 km s–1.

Primary of Chuvalete.

Spectral class: G8

More information

Primary of Gaheris.

Gliese 783 (279 G. Sagittarii) is a binary star system in the constellation of Sagittarius. It is 19.87 light years from Earth, and it has an absolute magnitude of +5.32. In space, Gliese 783 is approaching the solar system at a velocity of approximately 140 kilometers per second. At this rate, it will be 6.7 light years away in 40,000 years, and ten times brighter than its current state. The two stars are separated by an angle of 7.1", corresponding to a distance of about 43 AUs.

Spectral Class: K2, M3.5

Primary of Oisin.

The primary and secondary stars are nearly identical orange main sequence dwarves of spectral type K0/K1 and the tertiary star is an orange main sequence dwarf of spectral type K5.

Star C is separated from the A-B pair by 700 arc seconds, compared to a minimum of 4.6 arcsec for A-B, so it has a negligible effect on the movements of the A-B pair. Both A and B have active chromospheres.

The McDonald Observatory team has set limits to the presence of one or more planets around 36 Ophiuchi A with masses between 0.13 and 5.4 Jupiter masses and average separations spanning between 0.05 and 5.2 astronomical units, although the outermost stable orbits around either 36 Ophiuchi A or 36 Ophiuchi B are possible not beyond 1.5 AU.

Primary of Djuli.

The primary star in the Eta Cassiopeiae system has a stellar classification of G0 V, which makes it a G-type main-sequence star like the Sun. It therefore resembles what our Sun might look like if we were to observe it from Eta Cassiopeiae. The star has 97% of the mass of the Sun and 101% of the Sun's radius. It is of apparent magnitude 3.44, radiating 129% of the luminosity of the Sun from its outer envelope at an effective temperature of 6,087 K. It appears to be rotating at a leisurely rate, with a projected rotational velocity of 3.15 km s–1.

The cooler and dimmer magnitude 7.51 companion is of stellar classification K7 V; a K-type main sequence star. It has only 57% of the mass of the Sun and 66%[8] of the Sun's radius. Smaller stars generate energy more slowly, so this component radiates only 6% of the luminosity of the Sun. Its outer atmosphere has an effective temperature of 4,036 K. Compared to the Sun, this star, and the primary component, show only half the abundance of elements other than hydrogen and helium—what astronomer's term their metallicity.

This is a spectroscopic binary system, indicating that its binary nature was first detected by observing shifts in the spectrum. The pair are orbiting around each other over a period of 480 years.

Based on an estimated semimajor axis of 12″ and a parallax of 0.168″, the two stars are separated by an average distance of 71 AU, where an AU is the average distance between the Sun and the Earth. However, the large orbital eccentricity of 0.497 means that their periapsis, or closest approach, is as small as 36 AU, with an apoapsis of about 106 AUs. For comparison, the semi-major axis of Neptune is 30 AU.

Primary of Feng Po.

The primary star of the system (component A) is an orange dwarf star that may just have over three fourths the mass of the Sun, about 77 percent of its radius, and only 15.6 percent of its visual luminosity. It has a separation of 190 astronomical units from the binary components B and C, moving in an eccentric orbit that takes at least 2130 years to complete. Gliese 570 A is spectral type K4V and emits X-rays.

A binary system in their own right, components B and C are both rather dim red dwarf stars that have less mass, radius, and luminosity than the Sun. Component B is spectral type M1V, component C is spectral type M3V, and both emit X-rays.

An artists impression of Gliese 570 D showing the primary stars.
On January 15, 2000, astronomers announced that they had found one of the coolest brown dwarfs then known. Catalogued as Gliese 570 D (or rarely Gliese 570 d), it was observed at a wide separation of more than 1,500 astronomical unit from the triple star system. It has an estimated mass of 50 times that of Jupiter.

The status of Gliese 570 D as a brown dwarf was confirmed by Doppler spectroscopy at the Cerro Tololo Interamerican Observatory in Chile. The surface temperature of this substellar object was found to be a relatively cool 500 degrees Celsius, making it cooler and less luminous than any other known brown dwarf (including the prototype "T" dwarf), and classifying the object as a T7-8V brown dwarf. No X-rays have been reported from this brown dwarf.

Primary of Apocatequil.

Main sequence dwarf of spectral type G9. Formerly it was classified as K0, with the spectrum of this star serving as one of the stable anchor points by which other stars are classified. The radius has been directly measured using interferometery with the CHARA Array, which yields a result of 77.8% of the Sun's radius. It has 87% of the Sun's mass, but the luminosity of this star is only 43% that of the Sun. The projected rotation rate (v sin i) is relatively low at 1.5 km/s. It is considered a slightly metal-poor star, meaning that it has a lower proportion of isotopes with masses more than helium when compared to the Sun.

The temperature, luminosity and surface activity appear to vary slightly in a manner very similar to the sunspot cycle, although the full length of the cycle has not yet been determined. The total variability is among the lowest of all stars that have been measured by the Hipparcos spacecraft.