Originally the constellations were defined informally by the shapes made by their star patterns, but, as the pace of celestial discoveries quickened in the early 20th century, astronomers decided it would be helpful to have an official set of constellation boundaries. One reason was to aid in the naming of new variable stars, which brighten and fade rather than shine steadily.
Such stars are named for the constellation in which they reside, so it is important to agree where one constellation ends and the next begins. Delporte, However, the IAU defines a constellation by its boundary indicated by sky coordinates and not by its pattern and the same constellation may have several variants in its representation.
The constellations should be differentiated from asterisms. Asterisms are patterns or shapes of stars that are not related to the known constellations, but nonetheless are widely recognised by laypeople or in the amateur astronomy community. Whilst a grouping of stars may be officially designated a constellation by the IAU, this does not mean that the stars in that constellation are necessarily grouped together in space. Sometimes stars will be physically close to each other, like the Pleiades, but constellations are generally really a matter of perspective.
They are simply our Earth-based interpretation of two dimensional star patterns on the sky made up of stars of many differing brightnesses and distances from Earth. Each Latin constellation name has two forms: the nominative, for use when talking about the constellation itself, and the genitive, or possessive, which is used in star names.
Most of these are stars that are visible to the naked eye and very bright compared to other stellar objects. For this reason, most of them have a long history of being observed and studied by human beings, and most likely occupy an important place in ancient folklore. So without further ado, here is a sampling of some of the better-known stars in that are visible in the nighttime sky:.
It is very close to the north celestial pole, which is why it has been used as a navigational tool in the northern hemisphere for centuries. Scientifically speaking, this star is known as Alpha Ursae Minoris because it is the alpha star in the constellation Ursa Minor the Little Bear.
Because it is what is known as a Cepheid variable star — i.
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Whereas it appears to be a single bright star to the naked eye, Sirius is actually a binary star system, consisting of a white main-sequence star named Sirius A, and a faint white dwarf companion named Sirius B. The reason why it is so bright in the sky is due to a combination of its luminosity and distance — at 6.
And in truth, it is actually getting closer. For the next 60, years or so, astronomers expect that it will continue to approach our Solar System; at which point, it will begin to recede again.
In ancient Egypt, it was seen as a signal that the flooding of the Nile was close at hand. To the Polynesians in the southern hemisphere, it marked the approach of winter and was an important star for navigation around the Pacific Ocean. Alpha Centauri System: Also known as Rigel Kent or Toliman, Alpha Centauri is the brightest star in the southern constellation of Centaurus and the third brightest star in the night sky.
It is also the closest star system to Earth, at just a shade over four light-years. Centauri C.
Alpha Centauri B is an orange subgiant with Proxima Centauri, the smallest of the three, is a red dwarf roughly 0. English explorer Robert Hues was the first European to make a recorded mention of Alpha Centauri, which he did in his work Tractatus de Globis. In , Jesuit priest and astronomer Jean Richaud confirmed the existence of a second star in the system. In , astronomers discovered an Earth-sized planet around Alpha Centauri B. Also known as Alpha Orionis, it is nevertheless easy to spot in the Orion constellation since it is one of the largest and most luminous stars in the night sky.
In , Margarita Karovska and colleagues from the Harvard—Smithsonian Center for Astrophysics, announced the discovery of two close companions orbiting Betelgeuse. While this remains unconfirmed, the existence of possible companions remains an intriguing possibility. What excites astronomers about Betelgeuse is it will one day go supernova, which is sure to be a spectacular event that people on Earth will be able to see. However, the exact date of when that might happen remains unknown. Rigel: Also known as Beta Orionis, and located between and light years away, Rigel is the brightest star in the constellation Orion and the seventh brightest star in the night sky.
Here too, what appears to be a blue supergiant is actually a multistar system. The primary star Rigel A is a blue-white supergiant that is 21 times more massive than our sun, and shines with approximately , times the luminosity. Rigel B is itself a binary system, consisting of two main sequence blue-white subdwarf stars. Rigel B is the more massive of the pair, weighing in at 2.
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Rigel has been recognized as being a binary since at least when German astronomer F. Struve first measured it. Rigel A is a young star, being only 10 million years old. And given its size, it is expected to go supernova when it reaches the end of its life. Vega: Vega is another bright blue star that anchors the otherwise faint Lyra constellation the Harp.
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It is also the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere after Arcturus. Characterized as a white dwarf star, Vega is roughly 2. It is a relatively close star at only 25 light-years from Earth. Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. It was also one of the first stars whose distance was estimated through parallax measurements, and has served as the baseline for calibrating the photometric brightness scale.
Based on observations that showed excess emission of infrared radiation, Vega is believed to have a circumstellar disk of dust. This dust is likely to be the result of collisions between objects in an orbiting debris disk. Thousands of years ago, ca.
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At an average distance of light years from our Sun, it is one of the nearest star clusters to Earth, and the most visible to the naked eye. Though the seven largest stars are the most apparent, the cluster actually consists of over 1, confirmed members along with several unconfirmed binaries. The core radius of the cluster is about 8 light years across, while it measures some 43 light years at the outer edges. The cluster has had several meanings for many different cultures here on Earth, which include representations in Biblical, ancient Greek, Asian, and traditional Native American folklore.
Antares: Also known as Alpha Scorpii, Antares is a red supergiant and one of the largest and most luminous observable stars in the nighttime sky. Ares — refers to its reddish appearance, which resembles Mars in some respects. This supergiant is estimated to be 17 times more massive, times larger in terms of diameter, and 10, times more luminous than our Sun.
Hawaiian Star Lines
Hence why it can be seen with the naked eye, despite being approximately light-years from Earth. The most recent estimates place its age at 12 million years. Antares is the seventeenth brightest star that can be seen with the naked eye and the brightest star in the constellation Scorpius. Canopus: Also known as Alpha Carinae, this white giant is the brightest star in the southern constellation of Carina and the second brightest star in the nighttime sky.
Located over light-years away from Earth, this star is named after the mythological Canopus, the navigator for king Menelaus of Sparta in The Iliad.
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Thought it was not visible to the ancient Greeks and Romans, the star was known to the ancient Egyptians, as well as the Navajo, Chinese and ancient Indo-Aryan people. In Vedic literature, Canopus is associated with Agastya, a revered sage who is believed to have lived during the 6th or 7th century BCE.
It was not until that it was brought to the attention of European observers, once again by Robert Hues who recorded his observations of it alongside Achernar and Alpha Centauri in his Tractatus de Globis The first of these is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus. The third is in the right foote of the Centaure. Polaris is not a single star, but a multiple star system.
The main component, Alpha Ursae Minoris Aa, is an evolved yellow supergiant star belonging to the spectral class F7. It is 2, times more luminous than the Sun, 4. The star is classified as a Cepheid variable, showing pulsations over a period of about four days. Polaris A is a classic Population I Cepheid variable. It is the brightest Cepheid variable in the sky. Cepheid variables are stars that astronomers use to measure distances to galaxies and clusters. Its variability had been theorized since , but was not confirmed until , when the Danish astronomer Ejnar Hertzsprung confirmed the variation.