Viewing planets and stars is usually a nighttime activity, experienced after the Sun has set and the ensuing darkness allows for these jewels to be seen. But the disappearance of sunlight during a total solar eclipse can result in a similar, albeit more short-lived, opportunity for stargazing. During this year’s August 21 eclipse, for instance, four different planets and several familiar constellations will shine ever-so- briefly during totality.
During this year’s August 21 eclipse, four different planets and several familiar constellations will shine ever-so- briefly during totality.
Planets and Constellations
The brightest object to show itself, Venus, will become visible about 15 to 30 minutes before totality sets in. It will lie 34º west (to the right) of the darkening Sun (1º is about the width of your pinkie finger held at arm’s length, and 10º is the width of your fist held in the same way; thus, Venus will be a little more than three fist widths to the west of the Sun). It will stay visible until 15 to 30 minutes after totality ends.
Fainter Jupiter, located 52º east (to the left) of the Sun, should also become visible during the latter stages of partial eclipse for some observers east of Idaho, but it will be very low on the eastern horizon. It won’t have risen yet as seen west of Idaho so won’t be visible in that area. Some 30 seconds before and after totality, two other planets will be visible, though they will be more difficult to distinguish because of their faintness. Reddish Mars will be only 8º to the west of the Sun, while even fainter Mercury will be 11º southwest of the Sun.
As for constellations, the Sun will be in Leo during totality. Its brightest star, Regulus, may or may not be easy to see, depending on the glare from the nearby Sun’s corona during totality. Other bright stars that should be easier to see include Sirius (in Canis Major) and Rigel (in Orion), both to the west of the Sun; Capella (in Auriga and northwest of the Sun); and Arcturus (in Bootes and to the northeast of the Sun). The Big Dipper will also shine brightly, due north of the Sun.
By Kevin Schindler, Lowell Observatory Public Information Officer and Historian