Moonless Mornings bring Zodiacal Light, Perusing Ice Giants, and Will the Dragon Roar?
Will the Dragon Roar?
The annual Draconids meteor shower will peak on the evening of Monday, October 8. At that time, the sky overhead will be plowing straight into the cloud of interplanetary debris that generates the shower. Normally, this is a modest shower, but this year it might be much stronger — delivering up to 10 meteors per hour! Meteors are tiny particles burning up as they scream through our atmosphere. The material producing the Draconids was dropped by repeated passages of periodic Comet 21P/Giacobini-Zinner. Last month, that comet passed very close to Earth, so astronomers are hopeful that this shower will be enhanced this year. And, as a bonus, the moon will be close to its new phase, leaving us a nice dark sky.
To see more meteors, drive away from light-polluted urban skies and find a dark site with plenty of open sky. Don’t bother with binoculars or a telescope — their fields of view are too narrow for meteors. Just watch the sky overhead. And avoid bright white light from phones or tablets — it will spoil your eyes’ dark adaptation. We’ve now entered meteor season. A sequence of very good showers will occur over the next few months.
(Above: The glow of the pre-dawn zodiacal light, which can be seen during moonless periods when the ecliptic (green line) is steeper. Use the bright star Regulus to guide your search.)
During moonless periods in September and October, the steep morning ecliptic favors the appearance of the zodiacal light in the eastern sky for about half an hour before dawn. The glow is sunlight reflected from interplanetary particles drifting in the plane of our solar system. During this week, look east, below the stars of Leo (the Lion), for a broad wedge of faint light rising from the horizon and centered on the ecliptic. (The ecliptic passes directly through the bright star Regulus in Leo.) Don’t confuse the zodiacal light with distant light pollution, or the Milky Way, which is sitting further to the southeast.
The Moon and Planets
On Monday morning the moon will appear as an old, slim crescent briefly visible over the eastern horizon before sunrise. Just before midnight in the Eastern time zone, the moon will reach its new phase, when it is hidden by the nearby sun’s glare and completely absent from the night sky (Hooray!). On Tuesday evening, the young crescent moon will re-appear low above the western horizon. Then, for the balance of the week, our natural satellite will shift eastward and set later while waxing fuller.
As we watch the lit portion of the waxing moon grow larger every evening, we are witnessing the sun slowly rise over its eastern horizon. The slanting sunlight will be illuminating topographic high points and casting deep black shadows from them, especially along the terminator — the imaginary line that runs pole-to-pole between the light and dark hemispheres of the moon. That’s the best place to aim at with your binoculars or backyard telescopes.
Remember — when the side of the moon facing Earth is dark, the side facing away from us is lit by sunlight. The “dark side of the moon”, the hemisphere that faces away from the sun, makes its way all around the moon every month. The side of the moon we never see from Earth is properly called the far side, not the dark side.
The moon will remain a pretty after-dinner treat, embedded in the evening twilight, until Thursday. On that evening, low in the southwestern sky, it will sit 3 finger widths above the very bright planet Jupiter. The pair of objects will be visible together in the field of view of binoculars until they set shortly after 8 pm local time. To end the week, the soon-to-be First Quarter moon will land two finger widths to the right of Saturn on Sunday evening, October 14. The moon will slide closer to Saturn by the time they set in the west at around 10:30 pm local time.
Mercury will be visible this week, with difficulty. It will sink below the west-southwestern horizon shortly after 7 pm local time — soon after the sun. Meanwhile, very bright Venus will be sitting 1.5 fist diameters to the left of Mercury and will set at about the same time. If you have a very low open horizon, you might catch a glimpse of these two inner planets. Because Mercury is on the far side of the sun, its appearance in a telescope will be a nearly fully illuminated disk. On the other hand, Venus is gradually moving between Earth and sun, so it will exhibit a very thin crescent.
By the time the sky gets dark at 8 pm local time this week, the mighty planet Jupiter will sit less than a palm’s width above the southwestern horizon. It will set in the west-southwest at about 8:15 pm local time. Binoculars will let you see Jupiter’s four Galilean moons (Io, Europa, Callisto, and Ganymede) forming a line to either side of the planet.
Brighter, reddish Mars and dimmer, yellow-tinted Saturn will both occupy the southern sky after dusk this week. Once the sky is dark enough to reveal them, both planets will be about two fist diameters above the horizon, with Mars located 35° (three and a half fist diameters) east (to the left) of Saturn. Mars will set in the west at about 1:30 am local time. It’s still well worth looking at, even in a small telescope. Try to see a small white oval near the top of its disk. That’s the southern polar cap (but inverted by your telescope’s optics)!
Saturn will set in the west after 10:30 pm local time. As the sky darkens, even a small telescope should be able to show you some of Saturn’s larger moons, especially its largest satellite, Titan. Using a clock’s dial analogy, Titan will move counter-clockwise over the course of this week — starting from a position at 7 o’clock (nearly below Saturn) and ending at 2 o’clock (to the upper right of Saturn). (Remember that your telescope might flip and/or invert the view. Use the moon to find out how your telescope changes things and keep a note of it, since that will always be the case.)
This autumn will be an ideal time to peruse the ice giant planets Uranus and Neptune. They will be ideally placed for evening observing and also near to their biggest and brightest appearances.
Distant Neptune will be visible all night. It’s still near its closest and brightest appearance for this year. Using a decent quality telescope you can see the very blue, magnitude 7.8 planet among the dim stars of Aquarius (the Water-bearer) — sitting midway between the modestly bright star Phi (φ) Aquarii and the brighter star Hydor (Lambda Aquarii). It will highest in the sky (and best viewing conditions) at about 11 pm local time.
Blue-green coloured Uranus will be visible all night, too. You can see it without optical aid under very dark skies, but binoculars and telescopes work better. Uranus is located in the eastern mid-evening sky, about 4 finger widths to the left of the modestly bright star Torcular (Omega Piscium). That star sits a generous palm’s width above the “V” where the two starry cords of Pisces (the Fishes) meet. The planet will be climb higher until 2 am local time. The higher it sits, the easier it will be to see.
Nebulae are glowing clouds of cold hydrogen gas and traces of other elements that are being energized by radiation from nearby stars. They are far dimmer than celestial objects made up of stars, so they are best viewed when the moon is out of the night sky, as it will be this week. Many nebulae exhibit complex structures reminiscent of delicate veils. They are usually criss-crossed by dark dust regions positioned between Earth and the background gas. Many fine nebulae cover large areas of sky and are better viewed in binoculars. Some are small enough to fit within the field of view of a backyard telescope. Here are some nebulae to try seeing this week.
The constellation of Cygnus (the Swan) is nearly overhead in the eastern sky after dusk. It hosts several spectacular nebulae. The Veil Nebula is a huge supernova remnant that is 2.5° (or five full moon diameters across). This broken and tattered circle of glowing gas is centered 3 finger widths below the star Gienah (also known as Epsilon Cygni). The brighter western segment of the remnant, known as NGC 6960, is easily found where it passes across the medium-bright foreground star designated 52 Cygni. Once there, follow its curve around to find the opposite side of the remnant known as the Eastern Veil, or NGC 6992. There are more strands of nebulosity between those arcs.
The North America Nebula (also designated NGC 7000) is a glowing hydrogen cloud located less than 3 finger widths below the bright star Deneb. Dark dust in the foreground creates the Gulf of Mexico portion of this aptly named nebula. The Pelican Nebula (also designated IC 5070) is a smaller nebula sitting just to the upper right of the North America Nebula. It is part of the same cloud — with the dark dust visually dividing them. For best results, find the darkest skies you can. To see details, use the largest aperture telescope you can, and enhance these nebulas with an Oxygen-III or Ultra High Contrast filter.
Astronomy Skylights for this week (from October 7th, 2018) by Chris Vaughan.
Keep looking up to enjoy the sky! I love getting questions so, if you have any, send me a note.