Wednesday, October 16th 2019, 12:00 pm - What's visible in our sky in Fall 2019? A rare transit of Mercury, plus meteor showers, planetary conjunctions and the elusive Zodiacal Light.
The yearly Orionid meteor shower reaches it peak on Monday night!
As Halley's Comet makes its roughly 75-year journey around the Sun, it leaves behind a trail of dust and ice. Twice every year - first in May and then in October - Earth ploughs straight through that stream of icy debris.
As the planet's atmosphere sweeps up the tiny particles left behind by the comet, it results in numerous bright streaks of light across the night sky. This is known as a meteor shower.
While the meteors we see from Halley in May appear to originate from the constellation Aquarius (thus that meteor shower is named the 'eta Aquariids'), the meteors we are seeing in the sky now appear to come from near the constellation Orion.
The Orionids radiant at 1 a.m. local time, on October 22. Credit: Stellarium/Scott Sutherland
This is the Orionid meteor shower, or simply 'the Orionids'. Every year, it occurs from October 2 to November 7. While it starts off with only a few meteors per night, it slowly ramps up to dozens per night at its peak on October 21.
During the night of October 21 to 22, in the hours after midnight, an observer that is far away from city light pollution, and under clear, dark skies, can expect to see maybe 15-20 meteors per hour.
One thing of note for the Orionids: the meteoroids from this stream hit the top of the atmosphere at exceptionally fast speeds. This makes for brighter meteors, in general, but it can also result in a secondary phenomenon, known as persistent trains.
Embedded content: https://media.giphy.com/media/PTXacbEoYRqZW/giphy.gifA persistent train lingers after this fast-moving meteor. Credit: Giphy
A persistent train forms when a meteoroid is travelling so fast through the air that it strips away electrons from the air molecules in its path. These ionized air molecules linger along the meteoroid's path and each one emits a brief burst of light when it pick up a replacement electron to neutralize that ionization.
With so many molecules emitting this light, it shows up to us as a wispy, dimly-glowing ribbon in the sky, as the molecules are carried along by the wind. Since it takes some time for all of the ionized molecules to replace their lost electrons, these trains have been known to persist for up to half an hour!
Scroll down to the bottom of the article for an in-depth guide on how to get the most out of watching meteor showers.
FALL ASTRONOMY 2019
- Sept 26-Oct 10: Zodiacal Light in pre-dawn eastern sky
- Oct 3: Jupiter-Moon Conjunction
- Oct 5: Saturn-Moon Conjunction
- Oct 8: Draconids Meteor Shower peak
- Oct 10: Southern Taurids Meteor Shower Peak
- Oct 13: smallest/dimmest Full Moon of 2019
- Oct 21: Orionids Meteor Shower peak
- Oct 26-Nov 9: Zodiacal Light in pre-dawn eastern sky
- Oct 31: Jupiter-Moon Conjunction
- Nov 2: Saturn-Moon Conjunction
- Nov 5: Northern Taurids Meteor Shower peak
- Nov 11: Transit of Mercury
- Nov 17: Leonids Meteor Shower peak
- Nov 24: Venus-Jupiter Conjunction
- Nov 28: Jupiter-Venus-Moon conjunction
- Nov 29: Saturn-Moon conjunction
- Dec 11: Venus-Saturn Conjunction
- Dec 14: Geminid Meteor Shower peak
- Dec 21/22: Winter Solstice
SEPT 26 - OCT 10: ZODIACAL LIGHT
This fall, early risers will have a chance to spot an elusive phenomenon known as "The Zodiacal Light".
Moonlight and zodiacal light over La Silla. Credit: ESO
In the Royal Astronomical Society of Canada's 2019 Observer's Handbook, Dr. Roy Bishop, Emeritus Professor of Physics from Acadia University, wrote: "The zodiacal light appears as a huge, softly radiant pyramid of white light with its base near the horizon, and its axis centred on the zodiac (or better, the ecliptic). In its brightest parts, it exceeds the luminance of the central Milky Way."
The zodiacal light is caused by sunlight refracting off tiny bits of dust and ice that orbit around the Sun in the plane of the ecliptic (the same plane the planets orbit in). It is thought that this cloud originates from dust and ice blown off of comets.
According to Dr. Bishop, even though this phenomenon can be quite bright, the light is so diffuse that it can easily be spoiled by moonlight, haze or light pollution. Also, since it is best viewed just after twilight, the inexperienced sometimes confused it for twilight, and thus miss out.
On clear nights, and under dark skies, look to the eastern horizon, in the half an hour just before twilight begins to show, from about September 26 through to around October 10. It can also be seen from October 26 through to around November 9.
The best mornings to try to see this phenomenon are likely on either September 27 or 28, and October 27 or 28, since those are the days of the New Moon, and there will be no chance of moonlight spoiling the attempt. Look for a pyramid-shaped white glow, with the base along the horizon and the point angled towards the south.
MOON CONJUNCTIONS WITH JUPITER AND SATURN
Just as we've been seeing all summer long, with the planets Jupiter and Saturn so close together in our night sky, there are three nights every month to pay especially close attention, as the Moon passes right by these two, pairing up with one, then the other, for a very cool show.
On October 3, watch for Jupiter and the Moon, followed by Saturn and the Moon on October 5. Then seen Jupiter and the Moon again on Halloween, Oct 31, and Saturn and the Moon together on Nov 2.
While out trick-or-treating, look towards the western horizon to see Saturn, Jupiter and a thin Crescent Moon. Credit: Stellarium/Scott Sutherland
This pattern repeats one last time for the season on Nov 28 and Nov 29, with Venus coming in as an added bonus to the Jupiter-Moon conjunction on the 28th.
The view towards the southwest, at around 7:30 p.m. local time on November 28, 2019. Credit: Stellarium/Scott Sutherland
OCT 8 to NOV 17 - FIVE MINOR METEOR SHOWERS PEAK
Although there are annual meteor showers during all parts of the year, Fall is a particularly active season.
A meteor shower occurs when Earth passes through a stream of fast-moving bits of dust or ice, left behind by the passage of a comet or asteroid. With repeated passes around the Sun, these objects build up persistent trails of meteoroids, and as Earth passes through one of these streams, the atmosphere sweeps up the meteoroids.
When a meteoroid particle enters the atmosphere, the bright streak of light it produces (the meteor) is due to the atmospheric gases in its path being suddenly compressed and heated. The meteor goes out when either the meteoroid slows down enough that it is no longer compressing the air to the point of glowing hot, or the heating vaporizes the meteoroid, leaving nothing behind.
There are four minor meteor showers that peak in the autumn months - the Draconids on October 8, the Southern Taurids on October 10, the Orionids on October 21, the Northern Taurids on November 5 and the Leonids on November 17.
Each of these showers produces maybe 10-20 meteors per hour, on average, but this can vary from year to year. Due to this, they tend not to be very noteworthy events, although dedicated meteor shower watchers who get far away from city lights can still catch these displays.
Some years, these minor meteor showers can experience what's known as an 'outburst', becoming a major shower or even a 'meteor storm', as Earth encounters denser parts of the parent body's meteoroid stream. Meteor scientists have become fairly good at predicting these 'outburts' ahead of time. No outbursts are predicted for 2019, however.
In October, the Draconids will be competing with a fairly bright gibbous Moon, as will the northern Taurids, so neither shower is likely to give a good showing. The Orionids will have a last-quarter Moon to contend with, which will be up for the second half of the night (not good!).
For November, the northern Taurids will take place during a first quarter Moon, which will set around midnight (good timing!), but the Leonids could be largely spoiled by a gibbous Moon that rises early in the evening and remains up the rest of the night.
NOV 11: THE TRANSIT OF MERCURY
Among all the events happening in the sky during the next few months, a special show put on by the planet Mercury promises to be the best of them!
On November 11, 2019, Mercury will line up directly between the Sun and Earth to perform what is known as a 'transit'.
This simulated time-lapse view of the transit of Mercury traces the planet's path across the Sun. Credit: NASA/Scott Sutherland
Over the course of roughly five and a half hours, from 7:35 a.m. EST to 1:04 p.m. EST, the tiny planet will show up as a small dark circle as it crosses the face of the Sun!
This will be visible only during the daytime, and only through a telescope equipped with a special solar filter that blocks out the harmful rays of the Sun.
The best viewing in Canada will be from the Maritimes, Quebec, eastern Ontario and southwestern Ontario. For anyone in these areas, the transit will start after sunrise and there is a chance to see all 5.5 hours of it, from start to finish (weather permitting).
- Newfoundland: 9:05 a.m. NST to 2:34 p.m. NST.
- NS, PEI, NB, Labrador: 8:36 a.m. AST to 2:04 p.m. AST.
- Quebec, eastern Ontario: 7:36 a.m. AST to 1:04 p.m. EST.
Anywhere west of the eastern shores of Lake Superior will see the eclipse already in progress as the Sun rises at dawn (also, weather permitting).
- Thunder Bay: Sunrise at 7:58 a.m. EST, to 1:04 p.m. EST.
- Winnipeg: Sunrise at 7:34 a.m. CST, to 12:04 p.m. CST.
- Regina: Sunrise at 8:05 a.m. CST, to 12:04 p.m. CST.
- Calgary: Sunrise at 7:45 a.m. MST, to 11:04 a.m. MST.
- Vancouver: Sunrise at 7:16 a.m. PST, to 10:04 a.m. PST.
This map shows the best places to view the Transit of Mercury. Credit: Eclipse Predictions by Fred Espenak, www.EclipseWise.com
The last time we saw a transit of Mercury was on May 9, 2016. That was only three and a half years before this one, which may not seem very 'rare'. It certainly is rare, however, when you consider that it has taken three and a half orbits for us, and nearly 15 orbits for Mercury, for us to line up with the tiny planet again!
To see this event, you can set up your own telescope, but be sure its a fairly good one (Fred Espenak recommends, in the RASC Observers Handbook 2019, at least a 50x magnification), and that it is equipped with a solar filter that fits over the opening of the telescope. Anything else risks damaging your eyes, and unfortunately, the dot of Mercury will be too small to see simply by using your eclipse glasses from the 2017 Solar Eclipse.
No doubt many astronomy clubs and Canada's various Science Centres will set up viewing days, and you can bet that NASA's Solar Dynamics Observatory will be watching the event from space, which they are sure to livestream as it happens.
Check back for updates, and read on for what else you can see in the sky this season.
Watch below to see NASA's view of the 2016 Transit of Mercury