Find the radiating points of the Perseids and Delta Aquariid

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The radiating points of Perseids and Delta Aquariids, as well as those of other meteor showers, are represented by streaks radiating from a single point. The point is surrounded by a white circle.
Meteor showers have a radiating point, a point in the sky from which they appear to radiate. Image via Anton / Wikimedia Commons.

The Delta Aquariid meteor shower has a broad maximum, as opposed to a sharp peak in activity, and produces meteors throughout late July and early August. It rides the most famous Perseid meteor shower, which slowly rises to its peak every year around August 11, 12, and 13. The Perseids take their name from the constellation Perseus the hero. And the Delta Aquariids get their name from the star Skat, aka Delta Aquarii, in the constellation Aquarius the Water Carrier. For both showers, if you trace the meteor paths backwards, you will find the radiant points of the meteors. Read on to learn more about these hot spots in the sky. Now here is the good news. You do not need know the radiation point of a shower to take advantage of meteors. But these dots in the sky are fun to find!

Find the point of radiation of the Perseids

Perseus himself is not that easy to find. But a neighboring constellation – Cassiopeia the Queen – is. Look north for Cassiopeia. It has a very distinctive shape of the letter W or the number 3. See it? Good. Perseus gets up later than Cassiopeia on these summer evenings. In the wee hours, you will find Perseus under Cassiopeia in the northeastern sky.

Seen from the northern hemisphere, the Perseid radiant point is low in the northeastern sky in the evening and rises upwards throughout the night. The higher the radiation in your sky, the more Perseid meteors you are likely to see. For the Perseids, the radiant is highest before dawn.

Graphic of the constellation Perseus with arrows pointing radially outward from the spot near its apex.
The point of radiation of the Perseid meteor shower is in the constellation Perseus. The easy-to-find constellation Cassiopeia is nearby. Remember, you don’t have to find the radiation point of a shower to see meteors. Instead, meteors will fly in all parts of the sky.

Do you have a dark country sky? Then look for the Double Cluster in Persée. This double star cluster marks almost exactly the radiating point of the Perseid meteor shower. You can find it by scanning with your binoculars between Perseus and Cassiopeia.

Although the Double Cluster can be seen with the naked eye, its stars appear through binoculars. The clusters are more officially known as NGC 884 (Chi Persei) and NGC 869 (h Persei).

Are you looking for a dark sky? Discover EarthSky’s best places for stargazing.

Starry field with the constellation Cassiopeia and an arrow pointing to 2 small spots.
Here’s a cool binocular object to look for as you watch meteors. The constellation Cassiopeia recalls the famous double cluster at the northern end of the constellation Perseus. In addition, the Double Cluster almost marks the radiance of the Perseid meteor shower. Image via Flickr / Mike Durkin.
The sky above an orange horizon, with the constellation Perseus, the stars, and the Pleiades labeled.
Here’s more to see, as the night goes by. From the northern mid-latitudes, the constellation Perseus, the stars Capella and Aldebaran and the Pleiades cluster illuminate the northeastern sky in the wee hours after midnight on the nights of late July and early August. Meteors radiate from Perseus. Image via Till Credner / AlltheSky.com.
Milky Way above the observatory buildings with a trail of meteors above a building on the left.
Some Perseid meteors will be visible in the southern hemisphere, although their numbers will not be as high. Photo of northern Chile, via the European Southern Observatory / S. Guisard.

Find the point of radiation for the Delta Aquariids

As mentioned above, Delta Aquariids radiate from the constellation Aquarius, especially near its star Skat or Delta Aquarii. Skat is not a shining star. He is only the third brightest in the dark constellation Aquarius the Water Bearer. Still, you can spot this constellation and star if you go to a dark place. If you are in the northern hemisphere, you will also need a good view to the south to see Aquarius. From the mid-latitudes of the southern hemisphere, the star and constellation are north and higher in the sky.

Skat only appears modestly brilliant. But seen on the dome of the sky, it is close to a very bright star, Fomalhaut in the constellation Piscis Austrinus the Southern Pisces.

If you can see the Grande Place de Pégase and Fomalhaut, they can help you find Skat. See the 2nd table below. In addition, in 2021, Jupiter is close to the radiant Delta Aquariid. See the table directly below.

Jupiter shines brightly in front of the constellation Aquarius, radiant with the Delta Aquariid meteor shower.
Aquarius, the radiant of the Delta Aquariid meteor shower, is highest for the night around 2 hours after midnight (at midnight we hear halfway between sunset and sunrise). Aquarius is a relatively weak constellation. At the end of July 2021, the dazzling Jupiter sits on the western border of Aquarius, near the radiant point of the Delta Aquariid shower. So when you look towards Jupiter, you are looking approximately towards the radiant of this shower.
Sky map showing the Grand Carré de Pégase at Fomalhaut to the radiating point Delta Aquariid.
Note: This graph is valid for any year and Jupiter does not appear on it. Regardless of the year, you can find the glow point of the Delta Aquariids using the bright star Fomalhaut as a guide. The radiation point of the Delta Aquariid shower is located near a Faint Star Skat, or Delta Aquarii. This star is near in the sky to Fomalhaut, which sits roughly on a line drawn south through the stars on the west side of Pegasus Square. This graphic shows a large area, from head to south, viewed from the northern hemisphere. From the southern hemisphere, the radiant is closer to the sky. But don’t worry too much about the radiant spots. Meteors will appear in all parts of the sky.
Sky map of the region around the constellation Aquarius. A red circle marks the radiation of the Delta Aquariid meteor shower.
See bigger. | Want to see the star Skat, radiating point of the Delta Aquariids? This table can help you. The radiant is circled in red. To see Skat, you need a dark sky. Graphic via Wikimedia Commons.

Why do meteor showers have a point of radiation?

Of course, in reality, the Delta Aquariid meteors have nothing to do with the star Skat. And the Perseid meteors have nothing to do with the Perseus Double Cluster. Skat is about 160 light years away. The Double Cluster is believed to be over 7,000 light years from us, in the Perseus arm of the Milky Way. Meanwhile, meteors in annual downpours start near Earth, as debris left behind in space by comets. They encounter Earth’s atmosphere and begin to vaporize about 100 km above the surface of our world.

So why do meteor showers have radiant spots? This is because meteors enter Earth’s atmosphere through parallel paths. Seeing them coming from a bright spot in the sky is much the same illusion as standing on railroad tracks and seeing the tracks converge in the distance.

View of the train tracks as if they were pulled apart near you and pulled together in the distance.
When you stand on a railroad track, you can see the illusion of converging tracks in the distance. Likewise, the paths of meteors in a single meteor shower seem to converge at a point – the radiant point – on the dome of the sky. Image via Shutterstock.

Bottom line: How to find the radiation points for the Delta Aquariid meteor shower and the Perseid meteor shower. Plus an explanation of why meteors in annual downpours have radiation points.

Grande Place de Pégase: Easy to see

Read about all the major meteor showers: EarthSky’s guide to meteor showers

Deborah Byrd

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About the Author:

Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she is the editor of this website. She has won a host of awards from the broadcasting and science communities, including an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes science is a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like throwing a big global party for nature lovers,” she says.

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