Find Perseid and Delta Aquariid radiant points
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 overlaps with the more famous Perseid meteor shower, which rises slowly to its peak each year around August 11, 12 and 13. The Perseids take their name from the constellation Perseus the Hero. And the Delta Aquariids take their name from the star Skat, aka Delta Aquarii, in the constellation Aquarius the Water Bearer. For both showers, if you trace the paths of the meteors backward, you’ll find the meteors’ radiant points. Keep reading to learn more about these sought-after points in the sky. Now here’s the good news. You don’t need to know a shower’s radiant point to enjoy the meteors. But these points in the sky are fun to find!
Find the radiant point for the Perseids
Perseus itself isn’t all that easy to find. But a nearby constellation – Cassiopeia the Queen – is. Look northward for Cassiopeia. It has a very distinctive shape of the letter W or the number 3. See it? Good. Perseus rises later than Cassiopeia on these summer evenings. By the wee hours, you’ll find Perseus below Cassiopeia in the northeastern sky.
As viewed from the Northern Hemisphere, the Perseids’ radiant point sits low in the northeast sky at evening and climbs upward throughout the night. The higher that the radiant is in your sky, the more Perseid meteors you’re likely to see. For the Perseids, the radiant is highest before dawn.
Do you have a dark country sky? Then look for the Double Cluster in Perseus. This dual cluster of stars almost exactly marks the radiant 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 unaided eye, its stars burst into view through binoculars. The clusters are more formally known as NGC 884 (Chi Persei) and NGC 869 (h Persei).
Looking for a dark sky? Check out EarthSky’s Best Places to Stargaze.
Find the radiant point for the Delta Aquariids
As mentioned above, the Delta Aquariids radiate from the constellation Aquarius, specifically from near its star Skat or Delta Aquarii. Skat isn’t a bright star. It ranks as only the third brightest in the dim constellation Aquarius the Water Bearer. Still, you can glimpse this constellation and this star if you go someplace dark. If you’re in the Northern Hemisphere, you’ll also need a good view to the south to see Aquarius. From mid-latitudes in the Southern Hemisphere, the star and constellation are northward and higher in the sky.
Skat appears only modestly bright. But as viewed on the sky’s dome it’s near to a very bright star, Fomalhaut in the constellation Piscis Austrinus the Southern Fish.
If you can see the Great Square of Pegasus and Fomalhaut, they can help you find Skat. See the 2nd chart down, below. Also, in 2021, Jupiter is near the Delta Aquariid radiant. See the chart directly below.
Why do meteor showers have a radiant point?
Of course, in actuality, the Delta Aquariid meteors have nothing whatever to do with the star Skat. And the Perseid meteors have nothing to do with the Double Cluster in Perseus. Skat lies about 160 light-years away. The Double Cluster is thought to be over 7,000 light-years away from us, in the Perseus arm of the Milky Way galaxy. Meanwhile, meteors in annual showers start out close to Earth, as bits of debris left behind in space by comets. They encounter Earth’s atmosphere and begin to vaporize some 60 miles (100 km) above our world’s surface.
So why do meteor showers have radiant points? It’s because the meteors enter Earth’s atmosphere on parallel paths. Seeing them come from a radiant point in the sky is much the same illusion as standing on railroad tracks and seeing the tracks converge in the distance.
Bottom line: How to find the radiant points for the Delta Aquariid meteor shower and the Perseid meteor shower. Plus an explanation of why meteors in annual showers have radiant points.
Great Square of Pegasus: Easy to see
Read about all the major meteor showers: EarthSky’s meteor shower guide