June 2, 2004 | German astronomers have identified the dimmest galaxy ever seen. It probably contains a mere one million stars, spread out over an area 3,000 light years wide. According to Daniel Zucker (Max Planck Institute for Astronomy, Heidelberg, Germany), this is "a singularly unimpressive galaxy."
The new record holder is a dwarf companion of the Andromeda Galaxy, 2.5 million light-years away. Zucker and his colleague Eric Bell detected Andromeda IX, as it is called, as a slight overdensity of stars in images from the Sloan Digital Sky Survey. They presented their results at this week's meeting of the American Astronomical Society in Denver, Colorado.
Bell says there could be more of these ultra-faint satellites hiding out there, with even lower surface brightness. That would be good news for cosmologists. Current theories about galaxy formation predict many more small satellite galaxies than are actually being observed.
June 2, 2004 | The "Little Ice Age" that froze the northern hemisphere in the late 17th century coincided with a period of extreme solar inactivity known as the Maunder Minimum. Climatologists have often wondered whether the two had any connection. If so, it's up to astronomers to determine if the Sun might undergo such a minimum again. To answer that question, they are studying other Sun-like stars to see if other objects regularly undergo Maunder Minima of their own. One group presented its results this week in a poster presentation at the AAS meeting.
Using their observatory's 1.1-meter telescope, Lowell astronomers Jeffrey C. Hall and G. Wesley Lockwood checked various stars for magnetic activity variations by measuring the brightness of calcium emission lines in the stellar spectra. They found that many Sun-like stars show no sign of cyclic activity over periods of 6 to 9 years, suggesting possible minima. They also found the same stars have widely varying, constant magnetic activity. Thus it isn't clear if the stars they observe are undergoing true "minima."