Stargazer alert for Philadelphia! Here's how and when you can see a very rare planetary parade this week.
Over the next several nights in the Philadelphia region, through its peak on Friday, we will have the opportunity to see all seven of our sister planets simultaneously and in a straight line, parading across the sky.
This "Great Planet Parade" is very special and incredibly rare. It won't be visible again until 2040.
On Wednesday and Thursday evenings this week just after sunset, six of the seven planets will be visible to the Philadelphia area. Venus, Mars, Jupiter, Saturn, Uranus, and Neptune will form a line beginning on the horizon to the southeast and extending high into the sky.
Mercury will make its appearance completing the rare alignment with the other six planets Friday evening.
Both Thursday evening and Friday evening are the best chance for the Philadelphia area to see the planet parade, despite the chance of clouds in the area.
In case you wondered, we can't ever see all eight of the planets in our solar system because we are one of the eight planets. The best Earth can do is provide a celestial view for the ages.
Optimal viewing across the Delaware Valley
Here are the keys to optimal viewing across the Delaware Valley:
- First, the weather must cooperate. Clear skies or at least mostly clear skies are needed.
- Second, you must be outside during the first 90 minutes after sunset. This is a very short window of time so be prepared because both Saturn and Mercury will drop below the horizon first.
- Third, you'll need to be away from bright lights.
- Fourth, look to the southern and southeastern sky beginning at the horizon and extending in a line upward.
- Fifth, give your eyes up to 30 minutes to adjust to the darkness and avoid looking at a bright phone screen.
- Sixth, you will be able to see Mercury, Venus, Mars and Jupiter with the naked eye. However, binoculars or a telescope are recommended to see Uranus and Neptune and even Saturn, since it will be closer to the sun.
- Seventh, if you follow astronomy, here are some of the constellations the planets will be visible near: Mars near Gemini, Jupiter near Taurus, Mercury near Aquarius, Uranus near Aries, and both Neptune and Venus near Pisces (Venus will also be the brightest planet in the sky).
How rare are planetary alignments?
The sight of two to four planets in a line is common, four to six planets is very rare, and to have all seven planets visible is extremely rare. The last time the seven planets aligned was on April 8, 2024, the day of the Great North American Total Solar Eclipse. The next time all seven planets will align isn't until 2040.
Just a month ago, six of the planets were aligned. There will be a chance to see six planets aligned in late August this year. Mars will be missing in August.
These rare six to seven planet alignments, visible from Earth, typically occur every 100 years due to the length of some planetary orbits. We are fortunate to have several alignments in a span of two years. Some alignments are pre-sunrise while others are post-sunset. This week's viewing is post-sunset.
Why do the planetary alignments occur?
All eight planets in our solar system orbit the sun on the same path or plane but at different speeds and different distances from the sun. Some planets have fast orbits like Mercury, which orbits the sun every 88 days. Others have slow orbits like Neptune, which takes 165 years to complete one orbit. Of course, our planet Earth completes its orbit every 365 days.
Occasionally, several planets will catch up to each other and form a line in the sky. This line doesn't last more than a few days at most because the planets are still traveling at different speeds, so the line will separate as the planets continue their own orbits.
