The T Bootis Mystery

  I wrote about looking for T Bootis the night before last, and thought I should jot down some background information about it. T Bootis is the name of a star that was observed over 150 years ago by only one astronomer, and it hasn't been seen since! This makes it a mystery object in a lot of ways. 

  Joseph Baxendell, a British astronomer famous for (among other things) discovering that several stars were variable in brightness, spotted this star on April 9, 1860. He estimated it at 9.75 magnitude at the time (which makes it a very easy object to see through most telescopes, or even large binoculars). The new star was very close to the star Arcturus in the constellation Bootes; which is why it's designated as "T Bootis." Baxendell observed it again the following two nights and noted no change in brightness. He didn't observe the star again until April 22 following what was probably cloudy weather, and on that date he estimated it had dimmed to 12.8 magnitude. (This would have made it fairly dim through small telescopes, or even for my 10" scope with the light-polluted sky I deal with.) On the following night, April 23, 1860, Baxendell could not find it at all. Mass communications in 1860 being what they were, most other astronomers of the time weren't alerted to this discovery for days or weeks. However, several professionals checked the sky for this new object soon after it disappeared and found nothing.

  Since Baxendell was a seasoned professional astronomer, there's little doubt that he saw something! The question that remains is what T Bootis actually was. Though it's referred to as "Nova Bootis 1860" it had characteristics that set it apart from novae that have been observed before and after that time. Most novae occur within or close to the Milky Way, and this part of the sky is almost as far from the Milky Way as possible! Also. most classical novae show a sudden increase in light but a much slower decline in brightness after they peak, and this object apparently dimmed out of sight within days. It probably wasn't an asteroid since Baxendell would have seen movement with respect to the other stars during his observations. It's possible that it was something more exotic like a very distant comet that flared up and looked stellar through the telescope, but Baxendell probably would have seen and noted some "fuzziness" to T Bootis if it had been one. It's even been suggested that T Bootis was something unknown in 1860 like a gravitational lensing event or a distant galaxy eruption. 

  For the past several years. I've tried to make a systematic search for T Bootis. If it was a nova, it may be a recurrent one, and it's possible that it will flare up again. There seems to be less than a dozen amateur astronomers around the world who are doing the same thing. So far in 2011 the AAVSO website shows no other observers reporting it, so I might be the only person on the planet this year looking for it! I try to search the area every clear night I can when this area of the sky is visible. All of my estimates are negative; most nights I try to see if I can spot the nearby star ASAS141307+1901.0 which is about 13.2 magnitude in brightness. If I can see it, but see nothing where the position of T Bootis should be, I report less than 13.2 or < 13.2 to the AAVSO. Sometimes the faintest star I can see is 12.5 magnitude ASAS141327+1907.2, and I report it as < 12.5 on the website. 

  The reason for this search is simple. I probably won't be able to see this star in my lifetime, but on every clear night there's the possibility that I might be the first person since 1860 to catch T Bootis in the sky and make what could be a very important contribution to astronomy! That's all the motivation I need.