This Memorial Day weekend will not just bring together family and friends for barbeques and other festivities that traditionally mark the unofficial beginning of summer. This year, three planets will also come together in the western sky just after sunset. The planets Jupiter, Venus, and Mercury will form a small triangle in the twilight just above the western horizon. The picture to the right shows the three planets on May 25th at 9:30pm about 20 degrees north of due west.
Jupiter and Venus are the brightest of the planets. Jupiter has been visible in the evening sky since fall while Venus has been visible only in the morning sky. For a couple of weeks both planets will be in the evening sky. This weekend, they will be passing each other as Venus climbs higher, away from the Sun and Jupiter moves lower, closer to the Sun. Jupiter will swing around the Sun and be visible in the in the early morning sky just before sunrise for the Summer.
Joining these two bright planets is Mercury, the fastest moving planet. Of the five planets visible with the unaided eye, Mercury is the faintest, smallest, and because it is the closest to the Sun, the least likely to be observed. This conjunction provides an excellent opportunity to identify Mercury. Over the next few days you will notice that Mercury moves faster than the other two brighter planets. By Tuesday evening, May 28th, Mercury will be noticeably higher above Venus and Jupiter while those two bright planets pass each other. The picture to the left shows the planets on May 28th at 9:30pm.
The conjunction may not be the only astronomical event to observe this weekend. The Sun is reaching its maximum level of activity in its eleven year cycle. The number of sunspots on the Sun’s photosphere is at its highest and along with them, the associated solar storms that send streams of particles outward into the solar system. Over the weekend two very large storms sent streams of particles toward the earth. These particles impacted the earth during the past two days causing spectacular auroras as far south as Cape Cod, MA. The picture below of the aurora was taken from Cape Cod on May 20th. Chances are good that aurora may be visible any evening this summer. You can monitor solar storms, sunspots, and aurora at http://spaceweather.com/.
Finally, while you are outside this weekend, if the aurora is not capturing your attention take a look at the Big Dipper. Almost directly overhead, the arc of the Dipper’s handle will point to the bright star Arctarus – brightest star in the shepherd constellation, Boötes. If you keep following the arc, the next bright object along the path will be Saturn. So, with the three planets in conjunction in the western sky and Saturn in the southeast you will be able to see four planets in the early evening for the next week. Only Mars will be missing. The red planet happens to be very close to the Sun in the morning sky now. The sky chart below shows the sky at 9:30pm on Memorial Day. Note the conjunction of the three planets in the northwest and Saturn in the southeast.
Have a Happy and Safe Memorial Day and Happy Star Gazing!