![]() Although it was not known at the time, these were the most luminous stars. Maury had divided stars based on the widths of their spectral lines, with her class "c" identifying stars with the narrowest lines. Supergiant stars can be identified on the basis of their spectra, with distinctive lines sensitive to high luminosity and low surface gravity. Spectral luminosity class The four brightest stars in NGC 4755 are blue supergiant stars, with a red supergiant star at the centre. Subsequently, as they lacked any measurable parallax, it became apparent that some of these stars were significantly larger and more luminous than the bulk, and the term super-giant arose, quickly adopted as supergiant. One region contained larger and more luminous stars of spectral types A to M and received the name giant. The term giant star was first coined by Hertzsprung when it became apparent that the majority of stars fell into two distinct regions of the Hertzsprung–Russell diagram. The title supergiant, as applied to a star, does not have a single concrete definition. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K. ![]() ![]() ![]() Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. Nevertheless, it is a source of avid study by astronomers in the nearby Tyson cluster.Supergiants are among the most massive and most luminous stars. Evidence suggests it is surrounded by many planets, but governments have deemed it “unprofitable to colonize”, as the combined cons of a high radiation and potentially very long travel times (not to mention a possible supernova risk from its white dwarf companion) have outweighed the possible pros of such an extensive planetary system. It is 556,108 times as luminous as the Sun and is over 10 times as hot. A massive, bright blue O class star, it weighs a whopping 43.8 M ☉ and has an enormous radius of 6.6 R ☉. OKE4-19a exists at the other end of the spectrum from Eitri. It is a tiny M class star of about 0.247 M ☉ and is about a third of the size of the Sun, and only a mere 0.07% as luminous! With only a handful of terrestrial planets and a complete lack of giant planets, it barely features on star maps, and is only a “stepping stone system” to the blue giant Hrimnir. Not all systems are as fortunate as Agamemnon, however. Despite the age of its colony, it is one of the most thriving systems in human space, and boasts not only a “shirt-sleeves” habitable planet, but also a number of easily accessible giant planets and mineral-rich asteroids. Despite this, it is just over three times as bright and is a sweltering 7066 K on its surface. It is about 1.38 M ☉ and is roughly 17% larger than the Sun. Taking these into consideration, the best candidates for life as we know it are K, G and F stars, with K stars being the most likely to house life-bearing worlds.Īgamemnon is a bright, white, metal-rich F class star in the Tyson cluster and is one of the most recently colonized systems in the Armstrong Sector. Therefore, the star must be reasonably metal-rich. Metallicity: Research suggest only mid-high metallicity stars can host planets.Tidal Locking: The habitable zone of the star must be far enough away from the star that planets are not tidally locked to the star, which would inhibit life.Radiation: The star needs to emit enough UV radiation to trigger atmospheric dynamics such as an ozone layer, but not enough that the radiation kills off any potential life.This means that O, B and A stars, which spend less than 1 billion years on the main sequence, are poor candidates for life-bearing worlds. Stellar Lifetime: Any planet needs enough time for life to evolve on it.There are several factors to take into consideration when considering habitability of any particular main sequence star. The effective temperature (surface temperature) of a star is given by: The amount of time the star spends on the main sequence (its “main sequence lifespan”) is determined by the following formula: The luminosity (the amount of energy the star releases) is also related to the mass of the star, via the following relationship: The radius of a G, K or M star can be calculated using the following formula:įrom the above, the circumference (C), surface area (A), volume (V) and density (ρ) can be calculated, using the following formulae: The radius of an O, B, A or F star can be calculated using the following formula: Given the mass of the star, we can work out many other properties. The parameters of each main sequence spectral type Each stellar class has physical parameters, which are summarized in the following table:
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