Using the ALMA telescope, researchers observed radio waves, to look at water molecules in the disk. They observed water with a slightly heavier oxygen atom (H₂¹⁸O) and Heavy water (HDO where hydrogen is replaced with deuterium).
Band 7 is a specific range of radio frequencies that the ALMA telescope uses to detect molecular emission lines. Here Band 7 HDO lines observed are much weaker than expected. It reveals that the water emission may originate from a more compact and hotter region having a radius of 53 au from the star or regions hidden by optically thick dust.
Rotational temperature is a measure of the average temperature based on how many molecules are in different "spinning" (rotational) energy states. Rotational diagram is used to determine Rotational temperature (an estimate of the gas excitation temperature) and Column density of molecules.
The below equation describes the dust optical depth at a given observing frequency. Larger optical depth (𝜏) means dust blocks more radiation.
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