Friday, August 26, 2011

Orion, Sirius, Jupiter and friends in the pre-dawn sky

August is one of my favorite times of year, because if you rise early in the morning before dawn, you will be treated to the spectacular vision of Orion in the east, trailed by Sirius closer to the horizon (in the northern hemisphere). As the earth turns towards the east, the eastern sky begins to grow lighter and become blue, but the bright outline of Orion and the brilliant star Sirius are still clearly visible even after all the other stars fade away in the light of the approaching sun.

Right now, that sight is clearly visible if you get up before the sun. Here is a chart from EarthSky explaining how to find Orion and Sirius for observers in the northern hemisphere at this time of the year. Here is a previous post discussing these particular stars in conjunction with the term heliacal rising and their importance in the mythology of the ancients.

Currently, that awesome annual phenomenon is made even more spectacular with the addition of planets in the morning sky, especially Jupiter. This morning, the beautiful waning crescent moon accompanied them as well, and tomorrow morning it will do so again, but it will be extremely thin on its way to becoming a new moon this Saturday/Sunday. Above Orion, the unmistakably bright Jupiter stayed visible even after the brightening sun had caused Orion and Sirius to fade from view.

The chart above shows the locations of Orion, Sirius and Jupiter in the morning in the east for tomorrow morning (27 August) in the northern hemisphere. It is a portion of the sky chart generated by the very helpful free Interactive Sky Chart tool from Sky & Telescope.

You can see Orion's belt is almost vertical as he rises in the east, as is Canis Major and Sirius rising behind him. Jupiter is located further up and to the right in the diagram, and will be much higher overhead. Jupiter currently rises about 10:33 pm on the night of the 26th and makes its way across the sky, reaching transit at about 5:18 am on the morning of the 27th, at latitude 35o north. It rises and transits three to four minutes earlier per day.

You can also see in the above chart that Mars is located in the vicinity of Castor and Pollux in the constellation of the Twins (Gemini) at the same time. Here is a graphic from EarthSky describing how to find Mars on the morning of the 27th. It also explains how to find Mercury, low in the sky at dawn, tomorrow morning and over the next several days.

Be sure to rise early if possible and enjoy this glorious spectacle in the eastern sky.