Today’s Astronomical Events – April 12th, 2015

Mizar and Alcor are a famous pair of stars located in the constellation of Ursa Major, the Great Bear. Known for thousands of years, the pair were thought to be a good test of eyesight in ancient times. Mizar is the middle star of the bear’s tail and much brighter than faint Alcor. However, keen-sighted observers will be able to see Alcor with just their eyes. It appears in the ten o’clock position, in relation to Mizar, when Ursa Major is highest in the sky.

The pair make for a fine sight through binoculars with Mizar appearing about twice as bright as Alcor. However, when the pair are observed at low power through a telescope (35x is all that’s required) Mizar itself is seen to be double. Both stars appear blue-white and about the same brightness. (There’s also another faint star that forms a triangle with the Mizar pair and Alcor. In reality, neither this star or Alcor is anywhere near Mizar in space and the alignment is purely by chance.)

(Click on an image to enlarge.)

Map courtesy of Mobile Observatory. Image by the author, May 2006, take with an Orion XT 4.5″ Dobsonian telescope and a Kodak digital camera.



03:44 UT – Last Quarter Moon. (Naked eye, Sagittarius, pre-dawn sky.)

23:32 UT – The just-past last quarter Moon passes dwarf planet Ceres. (Ceres: magnitude 8.4. Capricornus, pre-dawn sky.)

Jupiter’s diameter shrinks to 40”. (Magnitude -2.3. Cancer, evening sky.)

The constellation Virgo (the Virgin) culminates at midnight tonight. (Naked eye, all night.)

The bright multiple stars Mizar and Alcor culminates at midnight tonight. (Mizar: magnitude 2.3. Alcor: magnitude 4.0. Naked eye, Ursa Major, all night. See images above.)



Events in bold involve objects and/or events that are easily visible with the naked eye.

All times are in Universal Time (UTC). To convert the time to your timezone, click here.

Learn more about upcoming astronomical events in 2015 An Astronomical Year (Kindle Edition) and The Astronomical Almanac (2015-2019) (Kindle Edition and Paperback Edition) and 2016 An Astronomical Year (North American Kindle Edition.)

The Amateur Astronomer’s Notebook allows astronomers to log 150 observing sessions and includes an appendix of hundreds of suggested deep sky objects.

Details of all available books across the world can be found here or by visiting the author’s page on Amazon.

If you have any comments or questions, please feel free to contact me at astronomywriter “at”

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s