|
Variable of the Month V442 Centauri This must surely be one of the easiest variable star fields to identify, as a fifth magnitude star shows the way, and an 8/9 mag pair reassures us that we is in the right ball park. Doing the estimate is just as easy: Either the star is invisible or it is not. In this case an error in your estimate is not nearly as important as reporting the fact that the star is in outburst. Enjoy looking at the field during our lovely spring dawn hours and keep following it until it is low in the West next winter. ETA CARINAE REVISITED One of the 1999 January Variables of the Month was Eta Carinae. S&T Bulletin dated 1999 10 08 contains the paragraph below. Is it expecting too much from Canopus readers to have a daily look with their binoculars or even the naked eye, if the astronomical community finds it worth while to use a R9 000 000 000 satellite to study it? CHANDRA SPIES ETA CARINAE Astronomers were once again surprised by what the Chandra X-ray Observatory can see as it peered into the heart of another familiar celestial object. On September 6th, the $1.5 billion telescope was turned toward Eta Carinae, a much studied star because of its history of variable activity and because astronomers believe that it is a supermassive star on the verge of going supernova (see the January 1998 issue of Sky & Telescope, page 36). The most detailed X-ray image yet of Eta Carinae -- taken by Chandra's Advanced Charge-coupled Device Imaging Spectrometer (ACIS) -- was released today and reveals an unimaginably hot (60 million degree Kelvin) central source surrounded by a relatively cooler inner core and cooler still (3 million degrees K) horseshoe-shaped ring. "It is not what I expected," Fred Seward (Harvard-Smithsonian Center for Astrophysics) explains. "I expected to see a strong point source with a little diffuse emission cloud around it. Instead, we see just the opposite -- a bright cloud of diffuse emission, and much less radiation from the center." Why this is so is unclear at present. Enjoy it. Danie Overbeek. |
|