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Astronomy From West Virginia

BIZARRE VARIABLE STAR TT ARIETIS BEGINS A DIMMING EVENT

BRIDGEPORT, WV (S-M)   - The variable star TT Arietis has begun its first dimming episode since the last event concluded in 1985.  On the night of October 25-26, 2009, we observed the star at magnitude 13.6 here at our small observatory.  This is more than two magnitudes dimmer than the star's usual level of magnitude 11.  Further, associates of ours report that they have photometrically observed rapid changes in the brightness of the star, amounting to as much as .5 magnitude change in four minutes.  This level of fast variability in a distant, deep-sky object is almost unprecedented, and it makes the star's activity exciting to watch.

The star is located in Aries, not far from the bright star Sheretan, Beta Arie.  It will take an experienced observer and a telescope of at least eight inches diameter to monitor the event, however.  From our moderately light-polluted location, the star was hard to see in a ten-inch telescope.  It lies in a line with two magnitude 11 stars, and there are numerous 13-14 magnitude stars in the field to use as comparisons.

During the star's last dimming event, which lasted from 1982 until 1985, it reached magnitude 15.5 and stayed so dim for more than three years.  No one knows how long the current event will last, but if the star becomes as dim as it did in the 1980's, it will disappear entirely in most small telescopes.  The cause of the star's dimming is hardly understood.  At one time or another, it has been proposed to be many different types of variable star, but now it appears it may be a sort of in-between type, perhaps a binary system or a star with an unstable accretion disk around it.   - GW