This Thursday night (November 21-22, 2019) – if you’re on the right part of Earth, and are looking at exactly the right time in a dark, clear sky – you have a good chance of witnessing a brief but very rich outburst of meteors known as the alpha Monocerotids. They will radiate from the constellation Monoceros the Unicorn, and many are calling them by the fanciful and fun name Unicorn meteors. And, indeed, in 2019 this usually-minor shower has a high possibility of being unforgettable, although hard to catch.

Astronomers Esko Lyytinen of the Finnish Fireball Network and Peter Jenniskens of the SETI Institute and NASA’s Ames Research Center have been tracking the alpha Monocerotids for many years. They realized that the circumstances for the shower in 2019 are nearly identical to 1995, when an outburst did occur, sending the rate up to 400 meteors per hour (several meteors per minute) under optimum conditions. That is why they predicted an outburst with a similar rate for this year. They emphasize that your location on Earth and timing – plus a dark sky – are key elements for watching the shower. Writing in Meteor News on November 6, they explained:

If an outburst takes place it is likely to be centered around 04:50 Universal Time on November 22, with a duration of 15 up to 40 minutes maximum.

That time – 4:50 Universal Time on November 22 – is the same as 11:50 p.m. November 21 for those on the east coast of the U.S.; translate Universal Time to your time. To see the shower, you have to be in the eastern part of North America, short of 110 west longitude, or in western Europe or South America, these scientists say.

The Virtual Telescope Project in Rome will offer an online viewing of the expected outburst of Unicorn meteors on the night of November 21-22, 2019. Go to the Virtual Telescope Project’s page.

How confident are these astronomers that this outburst will take place? They sound very confident. Jenniskens wrote in an email to EarthSky:

These outbursts are caused by the dust trail of an unknown long-period comet. Dust was released during the previous orbit of the comet, when it was last near the sun. Some meteoroids made a short orbit and came back early, others made a wider orbit and will come back late.

So, in the path of the comet now is a stream of meteoroids, quite smoothly distributed.

That stream moves in and out of Earth’s path over the years. That is the reason why we rarely get to see this shower. Only when the dust trail wanders into Earth’s path, just as Earth is passing the stream, are we hosed by the meteoroids. It is like watering a distant flower [Earth] with a water hose [the meteoroid stream]. Last good sighting was in 1995, and a weaker sighting in 2007 …

We are confident that the stream will be in Earth’s path this year, because the motion of the trail is determined by the gravity of the planets and sun, which we can accurately calculate.

How intense the shower will become depends on where exactly we cross the stream and on your location.

Rates are highest (several per minute at the peak) when the meteors come straight down, in parts of southern America. Here in the USA, peak rates are less because [we’re seeing the radiant point lower in the sky when the shower is peaking and thus] the meteors come in more grazing.

https://earthsky.org/