V Hydrae is a semiregular variable with a curious light curve. The star appears to undergo cyclical dimming events with a period of 15 to 20 years. The underlying pulsations don't seem to change much during these dimming events, which suggests that the star may be dimmed by dust. In fact, that's considered the most likely explanation, since infrared observations of this star show that molecular emission from diatomic carbon increases at the same time that the star itself dims, and the carbon is a sure sign that dust is forming or is already present. Several other C-type Miras and semiregulars show these dimming events, including RU Vir. You can read more about RU Vir, V Hya, and other Miras that behave like this in the Variable Star of the Season article linked below.
Prepared By: Matthew Templeton