planetary partial eclipses
- Transits not found for this planet
- Transit is a partial eclipse of the star by the planet
- eclipse only happens if planets “line of nodes” points at Earth
- demo with lunar orbit simulator
- lack of eclipse implies we aren’t on line of nodes
- orbit tilted several degrees from edge on
Recent Mercury transit demonstrates the effect
- alignment happens about every 10 y.
- 15 Nov. ‘99 event (WWW, TRACE solar observatory)
- x-rays show bloated corona (million K temperature)
- UV comes from patchy chromosphere (10-100 thousand K)
- visible from the photosphere (6000 K temperature)
- smallest diameter in visible
- Nowadays these events are primarily interesting things to look at
- Transit of Venus ~ 1890 first accurate measurement of the AU
- Venus transits every ~ 100 years