Sky Watch: Star light, star bright … oh, wait! It's the planet Venus

Even in the worst areas of light pollution, Venus has been putting on a great show this spring and will dazzle on through most of the summer.

Without a doubt Venus is the brightest starlike object in the night sky. Only Earth’s moon is brighter than the second-closest planet to the Sun. Well before the end of evening twilight, Venus pops out in the early evening western sky on its way to the horizon. Meanwhile, Jupiter, the fourth-brightest celestial object, is on the rise in the southeastern sky.

Venus is so bright that, if you’re looking at it away from the city lights where it’s super dark, it can even cast a faint shadow, something I’ve experienced several times. The last time was a couple of years ago on an astrophotography trip to the Arizona desert.

The reason Venus is so brilliant is twofold. It’s one of our next-door neighbors in the solar system, so as the Earth and Venus orbit the sun at their different paces they’re never far away from each other. Secondly, Venus is completely shrouded by very reflective clouds that bounce sunlight our way.

Even as bright as Venus is the planet named after the Roman goddess of love is anything but lovely! It has a poisonous atmosphere and is the hottest planet in our solar system. That cloud cover is mainly made up of carbon dioxide and sulfuric acid. Acid rain comes out of those clouds. There’s even occasional lightning. You certainly wouldn’t want to spend a lot of time floating in those clouds. It would be really rough on your complexion!

The heavy-duty carbon dioxide makes Venus the king of global warming in our solar system. Most of the sun’s light and radiation is bounced away by Venus’s highly reflective clouds but some sunlight manages to fight its way through and heat up the planet’s rugged surface of mountains and valleys. But what happens is that most of the infrared radiation that rises in response to the sun’s heating is trapped and absorbed by the carbon dioxide in the atmosphere. That drives up the temperature like crazy on the surface. Temperatures on Venus can top 900 degrees.

Another reason you don’t find many travel offers to Venus is because of the very thick atmosphere. The atmospheric pressure at the surface is 90 times that of Earth’s surface. It’s a poisonous pressure cooker!

As bright and close as Venus is to the Earth, I think overall it’s a really lousy telescope target. One obvious reason is all the cloud cover, and another is that most of the time it’s really low in the sky. That gives it a fuzzy appearance because its light has to go through a longer path in our atmosphere. High winds can also greatly affect it, too. If it’s really windy and there’s a lot of wind sheer, Venus can even twinkle. Planets usually don’t do that.

During my stargazing programs, I often get requests to point one of my big scopes at Venus. I try to convince those folks that basically all they’ll see a very bright oval-ish dot and that’s about it. The times I will turn the telescopes on Venus are when it turns into a crescent, which actually happens on a regular basis. That’s because we view Venus over the period of 584 days, called the synodic period. We watch Venus circle the sun in its orbit that lies within Earth’s orbit around our home star. It actually takes Venus just 225 days to orbit the sun but while it does we on Earth are also moving at a slower pace, so it appears to take longer for us to see a complete solar circuit of Venus.

Because of all of this, we never see Venus veer all that much from the sun in our sky. We either see it as a “morning star” in the eastern sky before sunrise or as an “evening star” in the western sky after sunset, where it is right now. Also because of the changing celestial geometry of the sun, Earth and Venus, Venus goes through phases just like our moon. Right now it’s a waning gibbous oval-ish Venus. As the summer goes on, it’ll turn into a half Venus and in August, it’ll assume a crescent shape. As that happens, Venus will start out in the evening much lower in the western sky and set shortly after the sun does.

So for most of this summer, Venus will be with us in the evening sky, but as we move into summer, three much more interesting planets will join it. In fact, Jupiter already has joined Venus in the eastern sky, with Saturn and Mars not far behind. I’ll have more of the big summer planet parade in next week’s column.

CELESTIAL HUGS

This Sunday evening the near full moon will be just to the upper right to the bright planet Jupiter as they both show up in the low southeastern sky in the early evening. Later on this week, there will be two more celestial huggings best seen in the very early morning sky, around 4 to 4:30 a.m. in the low southern sky. On Thursday morning, the waning full moon will be just to the right of the bright planet Saturn, and on Friday morning, it’ll be to the just to the left of Saturn. Next Sunday morning at about the same time and place, the waning gibbous moon will park just above the bright planet Mars, which has a definite reddish glow.

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