That it won't last long. Massive stars - like, several times the mass of our Sun - tend to shine very brightly, and thus use up their fuel very quickly, lasting only a few million years.
Unfortunately, it is impossible to tell accurately where a star is on the main sequence.
A star's position in the main sequence on the Hertzsprung-Russell diagram tells us its temperature, luminosity, and evolutionary stage. Stars in the main sequence are undergoing nuclear fusion in their core, converting hydrogen into helium. The more massive and brighter stars are found at the top left, while less massive and dimmer stars are at the bottom right of the main sequence.
A star's position on the main sequence indicates its mass, temperature, luminosity, and evolutionary stage. Stars fuse hydrogen into helium in their cores while on the main sequence. The more massive the star, the hotter, brighter, and shorter its lifespan.
The apparent magnitude depends on distance, and without that information, it's literally impossible to tell what it might be.
Brightness tells you the temperature and mostly temperature would tell the brightness of the star that we are talking about.
If they are converting hydrogen to helium, then they are on the main sequence. This can be confirmed with a spectral analysis
I have yet to find a good chart with all details of stars on it. (I am currently compiling one now). You can tell a lot from the spectral type of the star. You can determine the colour and star type (supergiant, giant, main sequence etc) it also gives you a maximum and minimum range in temperatures. (See Related Link) Looking at stars with a similar specral type will give you a good ball park figure.
Pay close attention to the opening sequence of a film. Many times, a director will summarize some or all of the main themes for the rest of the film in those first few minutes.
Apart from believing what scientists tell us, watching the stars is positive proof. This is especially apparent when viewing a time delayed sequence of pictures taken with the Pole Star in the centre (in the northern hemisphere). Though there is slight movement of the Pole Star, all other stars move round the Pole Star and show as curved lines of light.
In sequence: happening in chronological order, or forming a sequence. ^_^ Please tell me if that was useful.
bolt tightening sequence on what part?
That appears to be a DNA sequence to something. That is too short of a sequence for anyone to tell you the species.