The above lightcurve is the embodiment of a scientific prediction. You can plug any date/time you want into the prediction and it will tell you how bright the star should be at that time.

 

In fact, we’re going to test that right now.

 

I am getting data on this star right now. In about 15 minutes the Julian Date will be 2453851.60417. According to the ephemeris at the top of the plot above, that corresponds to phase 0.06 which has a predicted magnitude of V=12.74. Most of these measurements are +/- about 0.01 magnitude, so you could say the prediction is that the V-band magnitude will be between 12.70 and 12.77. This is actually +/- 0.03 = 3 x 0.01 and is known as a “3-sigma” error bar. Thus the prediction is stating that there is only a 10% chance that the magnitude is outside of this range.

 

This prediction is also based on the assumption that the star acts the same way all the time. It might have a period of 0.737 days and but have an amplitude modulation. Or it might have a period modulation that makes our period wrong.

 

So let’s go check! Be right back...

 

The measured V magnitude at HJD=2453851.60530 was V=13.13. Hmm! That is way, way off. This means either the period is wrong or the star is oscillating in amplitude. Stay tuned and we’ll figure it out!