THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet 70 Falmouth Street Portland, Maine 04103 43.6667° N, 70.2667° W Founded January 1970 “Be kinder than necessary because everyone you meet is fighting some kind of battle.” -J.M. Barrie (1860-1937) Scottish author and creator of Peter Pan. THE DAILY ASTRONOMER Wednesday, January 6, 2016 Belching Black Hole Now, we realize that this title is perhaps the most distasteful thing that the DA has ever foisted onto an unsuspecting populace. In our defense, we have heard other cute nicknames applied to this black hole and I assert that we chose the least objectionable of them all. This black hole is NGC 5194, a rather uncelebrated companion to the famous Whirlpool Galaxy more than 26 million light years away. Astronomers using the Chandra X-Ray Observatory have detected two gaseous "arcs" the black hole expelled millions of years ago.* The presence of these arcs demonstrates that black holes, notorious for drawing gases into themselves, can also repel them. [See an image of this galaxy on the Daily Astronomer Web-page: http://usm.maine.edu/planet/da-7-december-2015 ] These expulsions can serve as limitation mechanisms, preventing galaxies from becoming exceedingly large. Also, by pushing expelled gases into surrounding material, these repulsions could also precipitate star formation. Hence, ironically, a supermassive black hole, often touted as one of the most destructive objects in the known Universe, could also create new generations of stars. However, is these bursts are sufficiently powerful, they'll dispel such large gas stores thereby preventing a lot more star formation from actually occurring. These net negative effect might explain why elliptical galaxies such as NGC 5194 form stars much less frequently than spiral galaxies such as the Milky Way. While astronomers do not know exactly how these arcs formed, some researchers theorize that the black hole "engorged" itself on the copious gases conveyed into the system by its larger companion galaxy. The rapid matter flow would have generated prodigious energy responsible for the outbursts. Astronomers are still learning about the mechanisms that shape the galaxies scattered around the Universe. Much like the formation of the Himalayas, these mechanisms are immensely powerful and operate over long time scales. Often, galactic time scales will prove much longer than geological ones. Fortunately, astronomers can observe activities in myriad galaxies and from these observations can deduce how and why galaxies change through time. *We're including this side bar as an attempt to dispel any confusion related to time frames and verb tenses. NGC 5194 is approximately 26 million light years away. Therefore, we're seeing it as it was 26 million years ago, as light from that galaxy requires 26 million years to reach us. So, if astronomers say that a certain event in this galaxy occurred "three million years ago," they mean that it happened 26 + 3 million or 29 million years ago. We humans are so accustomed to observing everything instantaneously that the lag time is often not taken into account. I hope this side bar is helpful and doesn't make matters worse.