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By using the habo space telescle to detect the object's velocity
spectrocity...absorption of select frequency of light ie spectrocity
Astronomers are able to identify chemicals in distant space with the use of spectral analysis. This breaks the light apart into a spectrum and find either emission lines or absorption lines and identifies which elements are present.
Doppler shift tells the distance form the earth station
The temperature of a star is determined for it's colour spectrum. The hotter the star the more the spectrum is towards blue where as a cooler star has a spectrum closer to red.
SSo the astronomers can tell us what is happening to the sun. that good enough? :)
Weight is due to gravitational forces between two objects. A single object inspace without another one reasonably nearby, or even in gravitational free-falltoward another object, is weightless. So you can not weigh an object in space.Determining the mass of objects in space is another matter.
What elements the star is made of.
What makes up the star or element.
They get distant, but you have to see it.
The people you should ask are called astronomers who study astronomy.
It tells us that the Universe is expanding.