June 16 – Galaxies

M81 in the constellation Ursa Major (Big Dipper)

M81 in the constellation Ursa Major (Big Dipper)

Evening Highlights:
  • M51: The Whirlpool Galaxy, which is actually two galaxies colliding – M51A and M51B – is a beautiful grand-design spiral galaxy found in Ursa Major, and is over 23 million light years away.
  • M81: A spiral galaxy in Ursa Major, over 12 million light years away.
  • M82: A starburst galaxy in Ursa Major, over 12 million light years away.  M81 and M82 can often be seen together in a single field of view.
  • M31: The Andromeda Galaxy, a spiral galaxy and only 2.5 million light years from Earth.  M31 is also the only galaxy that can be seen with the naked-eye.
  • Three planets are visible in the sky tonight.  Don’t know which ones or how to find them?  You will after tonight.
  • See the International Space Station cross the night sky, as well as two iridium flares.
  • Frank will give a presentation on the upcoming August 21 solar eclipse, including how to view it safely.  The presentation starts at 8PM.

Please note that this event is held “weather permitting”, and is cancelled if it is raining or excessively windy; announcement of a cancellation will be posted both on this page as well as facebook.com/sdbhas.  We generally begin observing at 9:30 P.M.  

Our home, the Milky Way Galaxy, is a barred spiral galaxy, meaning it has the spiral arms most people often associate with galaxies, but it also has a distinct bar of stars emanating from the center of the galaxy.  Thought to be at least 100,000 light years in diameter and to have four distinct spiral arms, there is some evidence the Milky Way could actually be as much as 180,000 light years in diameter and have only two arms.  Our solar system is approximately 27,000 light years from the galactic center; so, assuming the Milky Way is 100,000 light years in diameter, we’re in the suburbs.  There are three main types of galaxies – elliptical, spiral and irregular – and several variations of each, with the majority of galaxies being barred spirals.  The Milky Way and Andromeda galaxies are on a collision course, and will collide in approximately 4 billion years.



Tonight’s Images


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