An 'almost, maybe' lunar eclipse this week? Find out here
A supergiant star and two planets form a celestial triangle in the night sky. Credit: Stellarium/S. Sutherland
Meteorologist/Science Writer
Wednesday, August 17, 2016, 11:49 AM - An "almost, maybe" lunar eclipse? Plus, the Perseids continue, Jupiter and Venus dip into the glare from the Sun, and a celestial triangle joins the Full Sturgeon Moon. It's Night Sky this Week!
This new weekly series pairs up the astronomical highlights that are visible in the sky over the next 7 nights with the weather forecast, to give stargazers an idea of what they'll be able to see in the coming week.
An "almost, maybe" lunar eclipse?
On the morning of Thursday, August 18, at around 5:42 a.m. EDT, something is going to be happening with the Full Moon.
Or, maybe not.
According to eclipse charts plotted some time ago, right around that time, the south pole of the Moon is supposed to be just barely touching the outer edge of Earth's penumbra - the diffuse outer ring of the planet's shadow.
Credit: NASA
Sources mention that this is supposed to be the final lunar eclipse of Saros series 109. One Saros is a period of time equal to 6,585.3 days or 18 years, 11 days and 8 hours, and eclipses separated by this amount of time are very similar to one another.
The "almost, maybe" part of this comes from the fact that when you now look up Saros series 109 on NASA's Goddard Space Flight Center eclipse page, the agency reports that the final eclipse of Saros 109 happened at 10:25 p.m. EDT August 7, 1998.
So, while the image above does show the edges of the Moon and the penumbra touching, in actual fact, early on Thursday morning, the the Moon will very likely just barely miss Earth's shadow.
Why the change? It could be due to refinements to eclipse calculations, or new data regarding the size of Earth's shadow.
We still encourage everyone to get out and see the Full Moon that night, as well as other objects in the sky this week. Read on to see why!
The Perseids continue
The Perseid meteor shower put on a spectacular show on Thursday night last week, but the show isn't quite over yet.
The Perseids radiant in the northeast sky. Credit: Stellarium/S. Sutherland
Although the Moon will spoil some of the view, as it approaches Full for the 17th/18th, Earth is still in the stream of debris from Comet Swift-Tuttle, and this shower is still putting out around 20-30 meteors per hour (under ideal conditions).
The radiant will track across the northern sky throughout the night, but be sure to look up, to take in as much of the sky as possible, otherwise you may miss some of the meteors. With the light from the Moon, however, it's likely that only the bright "fireball" meteors will be visible. The darker your location (thus far away from city lights), the more you will see.
Jupiter (and Venus) Setting
Jupiter and Venus are still visible in the sky this week, however you may need to be quick and have sharp eyes to see them. Look to the west just after the Sun dips below the horizon. Two bright "stars" will emerge from the glare of the sunlight, brighter Venus closer to the horizon and Jupiter just up and to the left.
Jupiter and Venus just after sunset. Credit: Stellarium/S. Sutherland
Both planets set soon afterward, so you need to look just at the right time.
Remarkably, if you have the right telescope and know exactly where it is in the sky, Venus (magnitude -3.9) is actually visible in full daylight! This is due to the face of Venus (the side facing Earth) being over 94 per cent illuminated by the Sun.
The Triangle and the Full Sturgeon Moon
August's Full Moon is this week, rising on the night of the 17th through the morning of the 18th (and actually reaching peak "fullness" around 5:30 a.m. EDT). Sometimes referred to as the Full Sturgeon Moon, this is the name given by tribes of Native Americans living near the Great Lakes, since this month is when the lake sturgeon are supposedly easiest to catch.
This week, the Full Sturgeon Moon is joined by a celestial triangle, made up of the planets Saturn and Mars, and the bright star Antares.
The southerly view on the night of August 17-18. Credit: Stellarium/S. Sutherland
Antares is located roughly 550 light years away from us, but it appears so bright in our sky because it is a class of star known as a "red supergiant". The star is so huge that if you swapped it in for our Sun, everything out to the asteroid belt would be consumed by it, and as such, it's roughly 10,000 times brighter than our Sun.
The Sky Forecast
Knowing what's up in the night sky to see is one thing. Actually being able to see it is another, and the weather is a major factor when it comes to stargazing.
For details on your nightly cloud conditions, check your local forecast. Below is a brief overview of the week, showing a snapshot of projected cloud cover for each night.
