How do we collect data from distant galaxies?

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  • Data collection from distant galaxies is mainly by studying the light we recieve from them. The light from distant galaxies usually travels over several millennia to reach us. Thus what we see are only images of the galaxies from the past. Light travels at 300,000 km/sec approximately. For instance, the light from the sun takes upto 8 mins to reach us. Imagine how much time it would take for light from faraway stars takes to reach us. Using deep field telescopes installed in space probes like Hubble, Subaru, Darwin among others, data is collected in the form of electormagnetic radiation(x-rays, gamma rays, infrared, visible light etc) coming from different directions in the universe. This data is usually ancient and could give clues about the origin of the universe, presence of other planets/planetoids like Earth or even tell us of birth and death of several stars. But these space probes are not technically capable of travelling huge distances. They can be stationary or attached to comets(only hypothetically for a comet). Parallax can be used to determine the size/distance of celestial objects. Variable stars(stars with varying luminosity)can be used to estimate distances and these are called standard candles. A relation called the period-luminosity(P-L) is used to calibrate and calculate the distance of a star. To measure the temperature of an object, a special detector called the Bolometer is attached to the optical telescope enabling the measurement of infrared radiation from it. The color of a star gives us the temperature of the star. The basic information we can avail off space probes consists of the spectra of starlight, brightness of stars, degree of polarization of starlight, star diameters, etc. A spectral image of a star can give clues to the elementary composition of the stars. The degree of polarization can help us determine the strenght of the magnetic fields in the stellar dust clouds. The electormagnetic data obtained has to be processed before analysis to remove image noise or aberrattions. So far only telescopic images have contributed information about deep space. It will take many years to develop the technology to send probes into the vast reaches of space to garner physical data like the lunar probes and the Mars probes. Our eye into space is our vision of the past that holds many clues for our future. Well, did I manage to answer your Question?
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