Jared May: What’s Up This First Week of September

We are entering September, the month where summer ends and fall begins (also the season of new deep sky objects). Sunset this week is hovering right around 8 PM, almost a full hour earlier than two months ago in early summer.

The weather this week for most of central Ohio is not looking conducive for stargazing with lots of cloudy days and nights in the forecast ahead. If there is a break in the clouds or perhaps a surprise clear night, there are a few night sky objects and events that are worth a look. Some for this week include the full moon, a close pass between the moon and mars, and some seasonal constellation that have some hidden treasures in them.

This Tuesday is the full moon and if the skies near the eastern horizons are clear around 8:30 PM, the moon will have a very unique appearance to it. There will be two things that will stand out about the moon’s appearance around this time: its color and its size. When the moon is low and near the horizon it may appear to be a brilliant red or orange. This is simply because the moon’s light must travel through substantially more atmosphere to reach our eyes than when it is high in the sky. As the light passes through all the air, blue colors tend to get scattered more than red colors allowing more red light to reach our eyes. If the moon is observed near the horizon it may also appear to be surprisingly large. This is because your eyes are seeing it with familiar references, like rooftops or electric lines. When we do have those references nearby, our brains can actually understand and perceive the apparent size of the moon! When the moon is high in the sky we have no references for size and we cannot accurately judge how big the moon is just by looking at it. When this big red moon appears near autumn, it is referred to as the Harvest Moon.

The Full Moon rising beyond the under-repair Washington Monument.

On Saturday around 10:30 PM, peer over the eastern horizons to see the moon passing right beside the red planet, Mars. They will be roughly 1° apart (about the width of your pinky held at arm’s length). This is a perfect viewing opportunity for naked-eye observers, as well as binocular and telescope users. In some cases, the moon may appear to entirely cover up a planet in the sky and this is called an occultation. 

Two seasonal constellations that have some interesting stars within them are Cygnus the Swan and Cassiopeia. Cygnus the Swan can be found almost directly overhead with the star Deneb (one of three stars of the Summer Triangle) forming the tail. This region of the sky is not just home to bright hydrogen alpha emissions (for you narrowband astrophotographers) but it also has some brilliant x-ray sources and contains one of the largest stars discovered, NML Cygni. This red hypergiant is found just off the tail and shines with a faint apparent magnitude of 16.6. NML Cygni is around 5,300 light-years away from Earth and is between 1,600 and 2,800 R☉ (solar radii) meaning if it were placed at the center of our solar system, the surface of this star would be somewhere out past the orbit of Jupiter or Saturn!

The well-known constellation Cygnus is seen passing nearly straight overhead- at the zenith.

The constellation of Cassiopeia can be found in the north eastern skies as an unmissable sideways “W”. This constellation contains supernova remnants, the brightest radio source in the sky (above 1 GHz), some hypergiants, and a naked-eye variable star. This variable star, gamma Cassiopeiae, is a bright and easy target for citizen scientists involved in the American Association of Variable Star Observers (AAVSO, and they are always looking for new members!). It fluctuates between magnitudes 1.6 and 3 and can be recorded with anything from a trained set of eyes to an advanced telescope setup.

The sky is filled with stars, nebulae, constellations, and other asterisms that each have a unique history and story to them. Many of these deep-sky radio sources or hypergiants may not even be visible to trained optical telescope users, but regardless, looking at them even with the naked eye and knowing that something that amazing is out there is awe inspiring. Get outside and enjoy the night skies with anything from your naked eyes to a telescope and explore.

Clear Skies!