You are here: Home USNO News, Tours & Events Sky This Week The Sky This Week, 2011 June 21 - 28

The Sky This Week, 2011 June 21 - 28

Deep-sky adventures on the year's shortest night.
SN2011dh_NOFSsmall.jpg

Supernova SN 2011dh in Messier 51, discovered 2011 May 31
Imaged with the USNO Flagstaff Station's 1.3-meter reflector, 2011 June 7 UT
U.S. Naval Observatory image courtesy of Dr. Marc Murison


The Moon wanes in the morning sky this week, passing through the dim stars of the autumnal constellations of Aquarius and Pisces. Last Quarter occurs on the 23rd at 7:48 am Eastern Daylight Time. Look for Luna just under five degrees north of bright Jupiter in the wee hours of the morning of the 26th. On the 28th her slender crescent will be just over four degrees northwest of Mars in the gathering morning twilight. If you have binoculars try to spot the Pleiades star cluster just two degrees north of the Moon. The next New Moon, which occurs on July 1st, will be the first of two for the month.

As we pass the summer solstice on the 21st we are experiencing the shortest nights of the year, and this week we see the latest sunsets for the year. Between the 24th and July 2nd Old Sol settles below the northwestern horizon at 8:38 pm EDT here in Washington. Evening astronomical twilight doesn’t end until 10:37 pm EDT, so stargazers with a hankering to observe deep-sky objects from dark locations better pack a sleeping bag and an extra thermos of coffee for the few precious hours of darkness before morning astronomical twilight, which begins at about 3:45 am. Even though the hours are short, there is much to enjoy in the late spring and early summer sky to fill that time. Many years ago a friend and I pulled a solstice "all-nighter" at Big Meadows on Skyline Drive. We had a memorable evening chasing down bright star clusters and distant galaxies from a large field that was full of deer. One of these "timid" creatures decided to snitch the granola bar from my back pocket at around 3:00 am; I thought that my resulting scream would wake folks up in Luray. It definitely cleared the field of all the deer!

Among the objects we observed that night was the well-known galaxy Messier 51, which may be found just below Alkaid, the star that marks the end of the "handle" of the Big Dipper. My friend’s 14-inch telescope was large enough to reveal the spiral structure first described by the Irish amateur astronomer William Parsons, Lord Rosse, who sketched the swirls of the galaxy’s arms as he observed with his 72-inch telescope in 1845. Amateurs observing today with telescopes of 8-inch or larger apertures may not be able to detect the spiral structure, but they can see a bright supernova which was first detected on May 31st. This object, the result of the cataclysmic demise of a massive star in one of M51’s spiral arms, has been brightening since its discovery and now shines at 12th magnitude, almost as bright as the rest of the galaxy’s stars combined!

A much easier target that’s readily available to urban observers is the planet Saturn, which can be found high in the southwest by 10:00 pm. The ringed planet forms a distinctive elongated triangle with the bright stars Arcturus and Spice, but it is the view through the small telescope that really captivates people. The planet’s golden disc, suspended as if by magic inside the brighter white-tinged rings, is one of the celestial sights that is never forgotten. From a sheltered urban location you should be able to glimpse a few of the planet’s icy moons. From a dark site half a dozen may be glimpsed with an 8-inch telescope.

Early risers should have no trouble spotting the bright glow of Jupiter in the eastern sky any time after about 3:00 am. The giant planet is almost 30 degrees above the horizon at 5:00 am, so if the telescope is handy check out his ever-shifting cloud belts and bright moons. Ruddy Mars is much more difficult to see as he is only 10 degrees up at 5:00 am, but by the end of the week the waning crescent Moon should help you track the red planet down with binoculars. You’ll have to wait until just 20 minutes before sunrise to see dazzling Venus. She hugs the horizon for another few weeks before disappearing behind the Sun later this summer.

USNO Master Clock Time
Javascript must be Enabled