Minor Planet 136108 HAUMEA Light Curve

[lukebl]

Hi folks,

Last night I had a go at capturing a series of images of Minor Planet 136108 Haumea, to get a light curve and perhaps see its rotation period. Haumea is fast-rotating and ellipsoid in shape, so I figured that it must vary in magnitude quite a bit during its rotation.

Sure enough, over a period of about 5 hours it varied from about mag 16.5 to 17.2, and the shape of the curve matches its assumed shape and rotation period of about 3.9 hours. As you see, there are asymmetrical dips in the minimum, which I guess indicates different textures, features or albedos of different parts of it. Haumea is the third-brightest object in the Kuiper belt after Pluto and Makemake, with an orbital period of 284 years.

I took about 110 x 3 minute exposures, Atik428ex, 200mm f/5 Newtonian. The data was processed in Muniwin. There was a bright moon which washed things out a bit. I think with a dark sky I'd get a more even curve.

Here's a quick stack of ten images, stacked in Astrometrica

[Demonperformer]

Certainly different from the usual images on SGL ...

It would be interesting to have the experiment repeated and see if the same pattern of bright in the middle of rotation + alternating low and deep minima replicate.

Excellent work.

[lukebl]

Hi folks,

I had another session taking photometric measurements of Haumea last night for comparison with my earlier readings, and the results were somewhat surpising. I averaged every three measurements to get a smoother curve and iron out any atmospheric fluctuations. The results are below.

As you see, last night's measurements show the period is the same (as you'd expect) but brightness is over a much smaller range, of about 0.2 magnitudes, compared with about 0.5 a couple of days ago. Weather conditions were similar and I used the same comparison stars for the photometric measurements.

Any idea why this could be? It surely can't be due to atmospheric conditions as that would equally affect the comparison stars. Perhaps Haumea is tumbling, rather than rotating on a fixed axis. Or maybe my methods are flawed?

2/3 May:

5/6 May:

Curves combined:

[Demonperformer]

The problem is only really the second "deep" dip. Smooth that out 0.3 mag brighter and there is a pretty close fit, including the double-dip-per-rotation effect.

Don't suppose it has anything to do with Hi'iaka? 22% the diameter of Haumea so it might have an effect on the light from Haumea when it crosses the disc. 49.12 days revolution period, so if that is right, the next "deep dip" would be just before 4am on the morning of 20 June.

Just a thought.