Class III luminosity and spectral type of OB classes are typical features of blue giants.
Blue giant is a star with high luminosity and a high surface temperature . Most of them are of spectral class B , although there are also some of spectral type O (such as the case of HD164492A belonging to the open star cluster called Collinder 360 , in the Trifid nebula ).
They usually have an absolute magnitude of between -5, -6 or more and are part of a phase of stellar evolution that does not last too long in time. According to those who contemplate and examine them, these stars have concluded the stage of nuclear fusion of hydrogen and are moving towards a period characterized by expansion and cooling that results in the appearance of red giants .
It is interesting to keep in mind that, although the names are similar, blue giant is not synonymous with blue supergiant (a type of extremely active star, with high temperature and high luminosity that leaves behind a black hole or a neutron star ) or star. main sequence blue (whose particularity is its slow rate of rotation following stellar mergers).
Characteristics of a blue giant star
Every blue giant star has characteristics that allow it to be differentiated from the rest of the luminous astronomical objects.
If you want to locate them in the graph called the Hertzsprung-Russell diagram , for example, you have to direct your gaze to the left side of the upper sector. These formations are generally located in star clusters and are related to stars that have a high mass. Furthermore, they do not go unnoticed given their intense shine and considerable size.
A significant percentage of its electromagnetic radiation is emitted in the ultraviolet area that appears in the electromagnetic spectrum, glowing with a bluish-white tone.
Thanks to the advancement of technology and the availability of more precise instruments, astronomers can add findings and knowledge about blue giants, for example.
Importance
Blue giants are usually valued based on their role as components of the universe. They are important, specialists say, in the development of heavy elements such as iron and carbon .
They have been investigated for a long time in order to expand knowledge about them and reveal unknowns in the field of astrophysics that have them as protagonists.
Years ago, to indicate a specific reference, a team of astronomers linked to the Australian National University worked on the internal structure of a bright blue giant called Beta Crucis that has been adopted as the image of different flags. This star that makes up the constellation of the Southern Cross , scientists maintained, was almost fifteen times more massive compared to the sun. According to asteroseismology , at least at that time Beta Crucis stood out for being the heaviest of the stars with a concrete calculation of age, since it was estimated that it was eleven million years old. Three resources were combined to arrive at the results: more than a decade of high-resolution spectroscopy on Earth, terrestrial polarimetry compiled from both the Penrith Observatory and the Siding Spring Astronomical Observatory , and a series of measurements made with NASA satellites around to the intensity of the light .
Seasons before that official announcement focused on Beta Crucis , thanks to the Hubble space telescope, it was possible to identify, in the central part of the Milky Way , an atypical stellar variety that was classified as a blue straggler . These formations appear to be younger than their peers and could be born with binary stars as their point of origin. The most massive of them is immersed in a process of evolution and expansion, while the other is gaining material arising from the dynamism of its companion. It is believed that stars have not emerged for billions of years in the central bulge of the Milky Way , which has been left as an area for stars similar to the sun to age and for more than one young red dwarf to settle. At some distant time there were blue giants there that ended up exploding as supernovae , specialists said.
A blue supergiant capable of moving at high speed has been detected within the Milky Way.
Nor should we overlook that scientists from the Spanish Astrobiology Center found in the aforementioned Milky Way a region full of fiery, bright, blueish stars about to experience an explosion. Astronomers from different countries under the command of researchers from the University of La Laguna and the Institute of Astrophysics of the Canary Islands , for their part, were able to find the whereabouts of one of the most luminous and massive formations in the Milky Way , a star classified as blue supergiant that is located behind a series of clouds of interstellar dust and gas. There was speculation, in the investigation, with the possibility that she (a star that has surprised with its incredible ability to increase its speed of movement) will become a blue hypergiant (a category that is not abundant, at least , in the galaxy where the solar system appears and, likewise, the planet that human beings inhabit.