Newsletter Archive

Good Mercury Hunting

November 10, 2020

In the morning skies for the next few days there will be some beautiful sunrise scenes, and a good opportunity to search for the hard-to-find Mercury ... for those willing to get up before the sun.

Mars, Jupiter, and Saturn (coincidentally all of the visible "outer planets") are currently visible in the evening skies, lined up in a row. A couple of weeks ago, the moon passed down the row as well. The other two visible planets (coincidentally both of the "inner planets") are now lined up over the sunrise, and the moon will pass along this lineup in the coming mornings.

Both Venus and Mercury are trapped near the sun, and are never visible except over sunrises and sunsets. When the brilliant "morning star" or "evening star" is present over a sunrise or sunset, it makes very beautiful scenes, especially if there is also a crescent moon nearby. (This may have been the origin of the name "Venus" for this beautiful sunrise-decorating star.) Venus is currently a morning star, and you should have no trouble finding it. It will be the brightest star over the eastern horizon before the sun rises. Mercury is dimmer and closer to the sun, but the next few days will provide good hunting conditions. If you have a clear view of the eastern horizon, you may be able to find it below Venus, close to the horizon, perhaps a half-hour or an hour before the sun rises. Venus and the moon will be there to help you find it.

Like the evening planets, the morning planets also line up more or less with the sun. If you imagine the sun below the horizon, and connect it in your imagination with a line passing through the planets in the sky, you will be visualizing the solar system. For the next few mornings, the crescent moon will descend along this arc in the sky, growing ever closer to the sun, and ever thinner and fainter. On the morning of Friday, the 13th, the moon will be between the two planets. If you have difficulty recognizing Mercury, this may be your best chance, because you can use Venus and the moon as guideposts or "stepping stones" to reach Mercury. The attached picture shows the Friday morning scene from Iowa. (If you live at a different latitude, the arrangement will appear rotated left or right, and if you live at a different longitude, the moon will be shifted up or down along the arc, due to the time difference.)

The Morning Planets

Today, the 10th of November, is actually the "greatest elongation" of Mercury, meaning that Mercury is the farthest it will be from the sun during this rotation, and from now on it will descend into the sunrise. Venus passed its greatest elongation months ago and is already descending. If you continue to watch as the mornings go by, both of these planets will follow the moon, sink into the sunrise, and both will eventually reappear on the other side as a sunset planet visible in the evenings.

You may also notice a few bright stars around. The brightest "star" that catches your attention when you first glance into the sky will probably be Venus, but there will be a couple of other bright "normal" stars in the neighborhood as well. The one on the left is Arcturus, the 4th brightest star in the sky (if you don't count the sun, which I don't). The one below Venus is Spica, the brightest star in Virgo, and the 16th brightest star in the sky.

If you look high and to the left, to the northeast, you may find the Big Dipper standing on its handle. If you follow the arc of the handle, you might notice that it takes you nicely to Arcturus, and if you keep going, to Spica. This is one of the useful guideposts to remember, to help you find your way around among the stars. From the Big Dipper, you can "arc to Arcturus, and then speed on to Spica." In this week's morning sky, you may also notice that this "Arcturus arc" passes nicely between the two planets, giving you yet another marker to help you find Mercury.