October SkyTalk | Dawn Conjunction of Planets

Out of consideration for most of our readers, the majority of our Sky Talk columns over the years have highlighted celestial events visible in the evening sky.  But occasionally predawn morning sky happenings worth getting up early for have been featured.  Such is the case of this month’s planetary spectacular.

Looking due east about 30 minutes before sunrise on the morning of October 11th, two of the major planets will embrace each other!  At that time, Mercury and Jupiter will appear just 0.8 degrees apart.  While visible to the unaided eye, your Scientifics binoculars will show them to much better advantage in the brightening dawn sky.  Both planets will easily fit in the field of view of even the smallest of glasses.  In fact, they will also fit within the low-power field of view of most telescopes.  Mercury itself is typically elusive for most of its orbit, so having Jupiter so close by offers skywatchers an ideal opportunity to spot this “shy” elusive world.

So elusive is Mercury that legend has it that even the great astronomer Copernicus never saw it.  However, this appears to be a myth.  When at it brief “elongations” east of the Sun in the evening sky and west of it in the morning one, it’s actually quite obvious.  But this rapidly moving planet is currently closing in on the Sun and will soon disappear from view.  Jupiter on the other hand is coming around from behind the Sun and moving higher in the sky each morning.  So while they appear to be close to each other in the sky, they are actually quite far apart in space.

Should you be unable to view this event itself on the 11th due to overcast skies (or to oversleeping!), it will still be worthwhile checking out these two planets both a morning or two before and then a morning or two after the conjunction itself.  In the first instance, Mercury and Jupiter will be approaching each other and in the second moving apart, their motions being easily seen in binoculars.  And while such glasses will normally show several of Jupiter’s four bright satellites, its low altitude above the horizon combined with the predawn sky will likely make that difficult at best.  Those using telescope should have better luck at seeing them despite atmospheric turbulence so near the horizon.

If you must restrict your skywatching to evening hours only, take heart.  Golden Saturn will be seen low in the west as darkness falls this month and ruddy Mars appears higher up in the southwest.  You may even be lucky enough to catch a glimpse of Venus later in the month just below Saturn.  If so, combined with the predawn view of Jupiter and Mercury, you will have bagged all five of the major naked-eye planets—quite a feat!

— James Mullaney

Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing.  His latest, Celebrating the Universe!, is available from HayHouse.com