You are here: Home USNO News, Tours & Events Sky This Week The Sky This Week, 2018 July 10 - 17

The Sky This Week, 2018 July 10 - 17

Going to the beach? Wade into the Milky Way!
Messier
Messier 4, globular star cluster in Scorpius
and Antares imaged from Morattico, VA, 2014 July 5

with an Antares Sentinel 80-mm (3-inch) f/6 refractor and a Canon EOS Rebel T2i DSLR.
Globular cluster NGC 6144 is above and to the right of Antares.

The Moon is conspicuous by her near-absence this week as she passes New Moon on the 12th at 10:47 pm Eastern Daylight Time.  At this time Luna will partially eclipse the Sun as seen from one of the most remote corners of the world – the coast of Antarctica south of Australia.  An observer here will see about one-third of the Sun’s disc covered by the Moon as the pair skirt the horizon.  The largest inhabited area to see the eclipse will be Tasmania, where observers will see a small “bite” taken out of the Sun’s upper limb during the course of the eclipse.  This event sets up a series of events over the course of the next month.  There will be a total eclipse of the Moon on July 27 (which unfortunately will be totally invisible from the United States) and another partial solar eclipse on August 11, best seen from the high arctic regions.  Closer to home, Luna’s thin crescent returns to the evening sky by the end of the week.  She may be found a couple of degrees below bright Venus in the fading evening twilight on the evening of the 15th.

If you are taking advantage of summer vacation this week and you’re headed for the mountains or the shore, take advantage of being away from the lights of the city to enjoy one of the most rewarding sights of summer, the Milky Way.  This is the season to see the densest parts of our home galaxy, whose amorphous light cuts a subtle glowing swath from the northeast to the southern horizon.  At 11:00 pm the densest star clouds of the Milky Way rise up from the tail of Scorpius, the Scorpion, and careful scrutiny will show a distinctive dark rift carving through the galaxy’s glow.  We are looking toward the galactic center when we view these clouds from our perch some 30,000 light-years away, and if you have a small telescope you can lose yourself among countless numbers of faint stars.  Interspersed in these star clouds are glowing knots of light which betray the locations of some of the “showpiece” objects of the “deep sky”.  Many of these are clusters of young energetic stars that are forming out of collapsing clouds of glowing hydrogen gas.  Others are older star groups that form into tight spherical shapes known as globular clusters.  These are generally found along the fringes of the Milky Way and contain some of the oldest stars known in the universe.  They are thought to be the remnant cores of dwarf galaxies that swept through the Milky Way’s disc, stripping them of gas and dust needed to form new stars.  In modest aperture telescopes these clusters are truly striking, reminding me of a bust of an aerial firework or the delicate seeds of a dandelion.  One of the best of these, Messier 4, lies just to the right of the bright star Antares in Scorpius.  Another showpiece globular is Messier 22, which can be found a few degrees below and to the left of Saturn.

Venus continues to slide eastward along the ecliptic.  As the week opens she is close to the bright star Regulus in Leo, the Lion, and as the week progresses she pulls away from the star.  She gets a visit from the waxing crescent Moon on the evening of the 15th.  You’ll find the Moon about halfway between Venus and Regulus, a configuration that should provide a nice evening photo opportunity.

Jupiter is now at his best position for telescopic inspection as evening twilight falls.  I like to look at the giant planet against a background of twilight glow since it helps enhance the contrast of some of his tawny cloud belts.  His most notable feature, the Great Red Spot, is well-placed for viewing on the evening of the 14th.  The spot’s color has become much more intense over the past few years, but it’s also been shrinking.  That said, it should be easy to spot in a telescope of four-inch aperture.  On the evening of the 15th you can see the shadow of Europa, Jupiter’s smallest Galilean moon, cross the planet’s cloud tops between dusk and 10:23 pm EDT.  If you’re still watching Old Jove at 11:30 pm you’ll see the shadow of Io begin its trek across the planet’s disc.

Saturn now crosses the meridian at around midnight, so you have a few hours to view him at his best.  Unfortunately, his far southerly declination means that we must observe the ringed planet through more of our turbulent atmosphere, but if you are patient at the eyepiece you may be rewarded with moments of steady air.  The planet’s captivating rings are tilted at their maximum for this apparition, so they should be visible in just about any telescope.

Mars is still in the throes of a spectacular planet-wide dust storm.  Even though his apparent diameter is growing to its greatest size since 1988, he shows little detail other than occasional glimpses of his south polar ice cap.  Even without a telescope, though, his visual appearance is quite striking.  As he approaches opposition on the 27th his brightness exceeds that of Jupiter, and his ruddy tint stands out in stark contrast to the feeble stars of the surrounding autumnal star field.  You should have no trouble finding him.

USNO Master Clock Time
Javascript must be Enabled