On the night of May 30-31, the tau Herculid meteor shower may appear.

There can be surprises in astronomy. A comet is usually too small to be seen with a telescope. In 1995 it suddenly and quite unexpectedly became dimly visible with the naked eye.

Thanks to this tiny comet, things could turn exciting at the end of May. The best of the annual meteor displays might be ranked on that night, as a new shower might erupt.

There is a small chance that this will be one of the most dramatic meteor displays since the spectacular Leonid shower of more than 20 years ago.


Maybe nothing will be seen.

Dates and viewing advice are included in the guide.

How it all started

The story begins on the night of May 2, 1930. Friedrich Carl Arnold Schwassmann and Arno Arthur Wachmann accidentally stumbled across a comet while cataloging new asteroids. This was the third discovery made by the two men.

The comet 73P/Schwassmann-Wachmann 3 passed only 5.7 million miles from Earth on May 31. Despite its very close flyby, comet SW 3 never got bright enough to be seen with the naked eye; it could only be seen with good binoculars or a telescope.

After 1930 comet SW 3 was missing in action for quite a while. SW 3 came and went eight times without being seen. It wasn't seen again until March 1979. In January 1985 it was missed, but it was recovered early in 1990.

Full of surprises

Comet 73P/Schwassmann-Wachmann is seen traveling alongside a fragment

Comet 73P/Schwassmann-Wachmann and its fragment fly through the view of Slooh's high-magnification telescope in Chile. (Image credit: Slooh.com)

Astronomers expected comet SW 3 to return in 1995. The Central Bureau for Astronomical Telegrams suddenly began receiving reports of a naked-eye comet, low in the western evening twilight, and sporting a dust tail.

This wasn't a new comet, it was SW 3!

The comet never came closer to Earth than 122 million miles. It should have been visible only with large telescopes. It was shining more than expected, with a nearly 400-fold increase in brightness. The European Southern Observatory in La Silla, Chile made observations in December of SW 3 that showed that the nucleus had splintered into four parts.

The comet was bright on its next visit in the fall of 2000, showing that two of the fragments spotted in 1995 had returned, together with a new one.

The comet appeared in the spring of 2006 with at least eight remnants and some of them forming their own sub-fragments.

Dozens of fragments were recorded by the Hubble Space Telescope. Between May 4th and 6th, the Spitzer Space Telescope was able to observe 45 of 58 comet chunks using its IRAC camera. SW 3 broke into more than 70 fragments and at its most recent appearance in March 2017, it showed signs that it was continuing to break apart and shed new pieces.

A comet that is very close to our Earth opens up a discussion about the possibility of a new meteor shower. The chance of interacting with a fragmented comet may sound familiar, and most astronomy texts often refer to the famous case of the splitting of comet Biela in 1842 or early 1843. The 1995 break-up of SW 3 has raised the question of whether we can hope for a similar performance in 2022.

Three important factors were considered.

  • When the comet fragmented in 1995, a tremendous expulsion of dust particles was ejected into space.  
  • When SW 3's nucleus broke apart, particles were likely ejected into space in all directions. Small particles the size of pebbles and sand grains are normally pushed behind the comet by the pressure of sunlight. But larger gravel and nugget-sized bits are not affected by solar radiation, so they end up on paths closer to the sun. The closer a celestial body is to the sun, the faster it will move in its orbit (gravity insists upon that; that's fundamental natural law). So, in time, these larger bits and pieces pass by the comet as they move in smaller orbits and thus, move out ahead of the comet.  
  • For those larger pieces to attain this faster orbit, they need to be ejected into space at nearly 60 m.p.h. (26.71 meters per second). Typically, this speed is a bit on the high side, but the sudden breakup of the comet's nucleus in 1995 and its resultant outburst of material might have been just potent enough to produce this necessary speed. 

The larger particles that were expelled in 1995 may have moved to a different location. Particles positioned ahead of the comet are needed for a meteor shower.

Studies by teams of reputable meteor shower experts, including one from Germany, and others from Japan, France, as well as by this author, have all come to the same conclusion: Earth will have a direct interaction with material released from the splitting of SW 3 at the end of May 1995. And the possibility of a new, never-before-seen meteor display appears especially promising. A consensus of the various predictions all points to 05:00 UT/GMT on Tuesday, May 31.

That translates to 1 a.m. EDT on Tuesday, May 31, or 10 p.m. PDT on Monday, May 30.  

If you want to photograph the Herculid meteor shower or want to prepare your gear for the next skywatching event, check out our best cameras for Astrophotography. For more helpful tips to plan out your photo session, read our guide.

Visibility: Radiant and moonlight

The emanation point of the comet would be positioned within the boundaries of the constellation of Bo, about 6 degrees north-northwest of the brilliant yellow-orange star Arcturus.

A large portion of the contiguous United States, south-central and eastern Canada, Mexico, Central and South America, and a small slice of West Africa are well-positioned for this event. In the U.S., the altitude of the radiant ranges from halfway up in the western sky in eastern New England to nearly overhead in southern California and the Desert Southwest.

A map showing the visibility of the possible tau Herculid meteor shower.

This map shows the visibility of a potential meteor outburst and is based on the assumption that peak activity will occur close to 5h UT on May 31.  The apparent altitude of the radiant is presented as green concentric circles at 10° intervals.  Your clenched fist held at arm's length is equal to roughly 10°.  Also plotted are zones for civil twilight (Sun 0° to 6° below the horizon), nautical twilight (6° to 12° below the horizon), and astronomical twilight (12° to 18° below the horizon).  From the Baja Peninsula, Mexico, the radiant is directly overhead at the appointed time.  (Image credit: Jérémie Vaubaillon)

Across parts of the Pacific Northwest, the northern Rockies and Great Plains, as well as for a slice of the Canadian Prairies, northern Ontario, central Quebec, most of Newfoundland and Labrador, the peak is expected to come during a time when the sun is 12 to 18 degrees below the horizon

Unfortunately, for far western and northern North America, as well as for the rest of the globe, the sky will either be too bright, bathed in sunlight or facing away from any incoming meteorites, preventing a view of any possible display.

The moon will be new on May 30. The skies will be dark.

What will we see?

Geminid meteor shower with the silhouette of a tree in the foreground.

The tau Herculids might produce a similar number of meteors observed during the annual Geminid meteor shower in December.   (Image credit: bjdlzx via Getty Images)

That is $64,000. The Earth and comet debris shed in 1995 have not come together in a long time, so it is difficult to predict how much the Earth will encounter. If the debris has spread far enough out ahead of the comet to interact with our planet, then it's all right. We will see next to nothing if not.

On the other hand, we could see a large number of meteors, similar to the annual December Geminids.

If we pass through a lot of comet debris, there is a chance of a big storm. It would probably be short-lived, not more than several hours.

How to watch

For an ideal meteor hunting experience you will need a ref flashlight, warm clothing, a hot drink and a nice deck chair.

To best view the possible meteor shower, go to the darkest possible location, lean back and relax. (Image credit: Future)

You're going to be outside for a while, as you'll need to wait for your eyes to become dark adapted. A reclining lawn chair is ideal. Be sure to dress for the weather; it might get chillier than what the local forecast suggests so also bring along a blanket. Don't stare at any one part of the sky; keep looking all over.

The most important thing concerning your possible meteor watch is finding a dark site far from any bright lights from which to observe. This will be essential!  

The particles will encounter the Earth at a very low speed. It is possible to hit the Earth from an elliptical path around the sun. The particles from SW 3 will produce very faint meteors, and only the biggest pieces will produce outstandingly bright shooting stars, because the faster a meteoroid travels, the brighter it will be. It is possible that a lot of larger pieces of the nucleus could be present in the shower.

The more dark your sky, the more meteors you will see.

Good luck and clear skies!

If you take a picture of the Herculids meteor shower and would like to share it with Space.com's readers, send your photo, comments, and your name and location to spacephotos@space.com.

The instructor and guest lecturer at New York's Hayden Planetarium is Joe Rao. He writes about astronomy for a number of publications. Follow us on social media.