Planets and Supernovas in the Night Sky

After dominating the western evening skies since almost the beginning of the year, Venus bids us farewell during July. It still sets after the end of dusk at the beginning of the month, it sinks rapidly toward the horizon over the next few weeks, and by month’s end disappears into twilight. After passing between Earth and the sun in mid-August, Venus emerges into the morning sky toward the end of that month and subsequently dominates the pre-dawn skies for the rest of this year.

Mars also begins to leave our evening sky this month, although it does so much more gradually—it doesn’t disappear into twilight until about the middle of August.

Mercury makes an appearance in our evening sky during the latter part of July, although it remains rather close to the horizon during dusk and won’t be easy to see.

Our solar system’s two largest worlds are both well placed for viewing this month. Saturn rises during the mid-evening and is high in our southern sky during the hours before dawn, while Jupiter rises around midnight and shines brightly in our eastern sky throughout the morning hours. An intriguing morning-sky sight takes place Thursday, July 13, when the crescent moon passes close to the Pleiades star cluster in Taurus.

From time to time throughout the universe, a massive star will explode in an event known as a “supernova.” For a while may shine as brightly as all the rest of the stars in its galaxy combined. The most recent supernova we’ve seen in our galaxy occurred more than four centuries ago, but hundreds are seen in other galaxies every year. Most of these are very dim objects, but every so often one will appear that can be seen with backyard telescopes.

Such a supernova recently appeared in a galaxy known as M101, which is located north of the handle of the Big Dipper some 21 million light-years away from us—practically next door, in cosmic terms. A Japanese amateur astronomer, Koichi Itagaki, discovered this supernova on May 19, and in the weeks since then, it has been easily visible in fairly small telescopes. This is, in fact, the brightest supernova that has appeared in our skies in more than a decade. It just so happens that the last bright supernova also appeared in M101.