How to drive an astronomer goo-goo

I know we didn't get far with our "Top Ten" list of things to see from a city sky, but sometimes things just pop up to get in the way. Such is an event this time.

Want to know how to drive an astronomer goo-goo? Tell him there is a planetary transit of the Sun coming up. He (or she) will get glassy-eyed, start to drool at the mouth, and get weak in the knees.

A transit is when any orbiting body crosses the face of any other orbiting body when seen from any other orbiting body in an outlying orbit. In this case Mercury and Venus can be seen crossing the face of the Sun from any planet from Earth outward.

Mercury can be seen crossing the Sun from Earth 13 or 14 times a century.

Venus can be seen to cross the Sun in pairs of events eight years apart separated by another transit 100 years later. The most recent transits of Venus was in 2004 and 20012 and I was fortunate enough to witness both events. The next transit of Venus won't be until 2112.

Earth can be seen to transit the Sun if you were on any planet farther out in the solar system.

For example, if you were standing on Mars on Nov. 10, 2084, you could watch Earth cross the Sun from Mars.

Transits of Mercury occur only in May or November and are more frequent than transits of Venus because Mercury orbits the Sun once every 88 Earth Days.

Recent transits of Mercury were in 2001 and 2003 and will happen next on November 11, 2019, and November 13, 2032.

Mercury's transit starts before sunrise on Tuesday, May 9, at 5:13 a.m. MDT as seen from Southwest Nebraska. Timing for other areas will be off by a few minutes from that time. The tiny planet will cross the Sun's face until 12:35 pm MDT.

Local sunrise is 5:30 a.m. MDT.

In order to view the transit you need a telescope and a very clear, unobstructed eastern horizon.

You will also need the proper solar filtration to reduce the light of the Sun through the telescope. If viewed it unfiltered that view of the Sun will be the last thing you ever see.

Solar filters can be obtained from almost any source of astronomical equipment.

SKY WATCH: Third quarter moon on Friday, April 29. Third quarter moons are typically observed in the early morning to early afternoon. For example, on that Friday the moon will be seen high in the south at about 7 a.m. MDT and will set in the west at about 12:46 p.m. MDT.

The planet Jupiter can be seen high in the south about an hour after local sunset directly below Leo, the Lion, and Mars and Saturn will be above the eastern horizon just after midnight.

You might want to make an effort to be up and outside at that time because the two bright planets will make a nice triangle with the bright star Antares in Scorpius, the Scorpion.

NEXT WEEK: Back to our Top Ten List for city skies, some tips for viewing the transit and more astronomical blathering