Just make sure the Sun has completely set before sweeping around the western sky with binoculars.
🌙 WATCH THE CRESCENT GROW
One of the easiest little astronomy experiments this week requires absolutely no equipment.
Look at the Moon at roughly the same time each evening.
On Monday it is a slim crescent.
The following evening it is noticeably thicker.
It also appears farther east relative to the setting Sun.
Night after night, the change becomes obvious.
We often think of the Moon’s phases as static pictures — crescent, quarter, gibbous, full — but watching it repeatedly reminds you that the Moon is physically moving around Earth all the time.
The phase is not changing because Earth’s shadow is covering the Moon.
That misconception refuses to die.
Ordinary Moon phases are caused by our changing view of the Moon’s sunlit half as it orbits Earth.
Earth’s shadow only becomes involved during a lunar eclipse.
If you remember nothing else from this article, please help me retire that myth.
☄️ THE ORIONIDS ARE BUILDING
All Week
Now we get to the meteor shower quietly warming up in the background.
The Orionid meteor shower is active throughout October and reaches its annual maximum around October 21–22, just after the week covered by this article.
But meteor showers do not switch on at midnight on peak night and switch off again twenty-four hours later.
Activity builds gradually.
That means Orionids can already be seen this week.
Rates will be lower than at maximum, so do not expect a meteor every minute, but if you are outside late at night or before dawn, particularly toward the end of the week, keep watching.
You may catch one.
☄️ THESE METEORS CAME FROM HALLEY’S COMET
This is the part that makes the Orionids special.
Their parent comet is 1P/Halley — Halley’s Comet.
Every time Halley’s Comet travels through the inner Solar System, it sheds dust and small particles along its orbit.
Earth passes through that debris stream every October.
Those particles hit our atmosphere at enormous speed, heat the surrounding air and create the bright streaks we call Orionid meteors.
So the comet itself is nowhere near Earth this October.
Halley last passed through the inner Solar System in 1986 and will not return until 2061.
But material it left behind continues crossing our path.
There is something wonderfully ghost-like about that.
The comet leaves.
The meteor shower stays.
🌠 WHY ARE THEY CALLED ORIONIDS?
Trace the paths of Orionid meteors backward and they appear to originate near the constellation Orion.
That apparent origin is called the radiant.
The meteors are not actually coming from the stars in Orion, of course.
Those stars are enormously farther away.
It is simply a perspective effect produced by Earth moving through a stream of particles travelling along roughly parallel paths.
Think about driving through snowfall at night.
Snowflakes appear to stream outward from a point ahead of the car even though they are not physically being launched from that point.
Meteor radiants work similarly.