Unless you have a radio telescope in your backyard, daytime astronomy is pretty much limited to the sun. Our daytime star is a fascinating astronomical object. It generates sunspots and prominences, those looping arches of solar plasma carried up from the sun’s surface by its magnetic field.
Active spots on the sun’s surface can fire flares and coronal mass ejections — clouds of electrically charged particles — at our planet. Upon arrival at Earth, these can wreak havoc with satellite operations and even our electrical grid. At the least, they generate the beautiful auroral displays we call the Northern Lights. But, without proper shielding, you should never try to look at the sun.
The moon also is often visible in daylight, but generally creates no astronomical excitement. It can this Saturday.
Viewing planets by day
There actually are several other astronomical bodies besides the sun and the Moon regularly visible during daylight hours — notably Venus, Jupiter, Mars and Saturn. The problem is finding their pinpoints of light against the blue daytime sky. This is where the moon can help this Saturday.
Everything in space is brighter when higher in the sky. Around 8 p.m. Saturday, the moon and Mars will be very close together in the south, with less than the moon’s diameter separating them. And they’ll be about as high as they will be for the day. With the sun less than an hour from setting, the sky where the moon and Mars float will be dimmer than normal. The half-full moon will be easily visible and you can use it as a guide to Mars, hovering just above it. You may need to use binoculars to first locate Mars, but it should be visible with the normal human eye.
On Saturday, the moon will pass not quite as close to Saturn, but their closest approach occurs at 9 p.m., when it will be dark enough to see Saturn without the aid of the moon.
When two celestial bodies appear close together in our sky, even though they are actually separated by many millions of miles, like the moon and these two planets, astronomers call that a conjunction. Over time, the moon has conjunctions with all of our planets.
If two celestial bodies are actually close together, and not just in appearance, astronomers call that a collision. Best to avoid those.
Orbit to produce high tides
Planets, Earth included, orbit stars not in perfect circles, but rather in ovals. The same is true as the moon orbits Earth. So once each orbit, the orbiting body reaches the extremes of the oval, the ends. At those times, tidal effects are greatest.
Earth reaches one of the points around the sun on Friday. Our moon reaches one of those points around Earth on July 13. The two forces that most affect our tides will reinforce each other, creating particularly high tides. And this perigee point, when the moon is closest to us, in August will be even closer, so tides should remain generally strong for a while.
Make sure your boat is well-anchored to the docks at Lake Hefner.
•Whatever astronomical sights grace our sky, day or night, we’ll let you know about it in our daily presentation “Tonight’s Sky.” Log on to www.sciencemuseumok.org or call 602-3761 for more information.
•The Oklahoma City Astronomy Club meets July 11. Check out its web page at www.okcastroclub.com to learn about club activities.
•Planet visibility report: After months of dominating the night sky as the brightest planet visible, Jupiter finally dives into the evening twilight on it way behind the sun. That leaves Mars and Saturn as the lone planets in the early night sky. Venus rises two hours before the sun each morning, and Mercury joins Venus in the morning twilight during the middle of the month. Full moon occurs July 12 with new moon following on July 26.
Wayne Harris-Wyrick is director of the Kirkpatrick Planetarium at Science Museum Oklahoma. Questions or comments may be emailed to firstname.lastname@example.org