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.