This is the Skywatch Line for Monday, and Tuesday, May 4th and 5th, written by Joe Slomka.
The Sun sets at 8 PM; night falls at 9:53. Dawn begins at 3:51 AM and ends with the Sun rising at 5:44.
The Moon occupies Virgo on both nights. The 91% illuminated Moon rises at 4:38 PM and sets at 5 AM, Tuesday. Tuesday, the 97% lit Moon rises at 5:55 PM and sets at 5:30 AM, Wednesday.
Venus is the sole evening planet visible. In Taurus, Venus shines at minus 4th magnitude, is 42 arc-seconds in size, is 21% lit, 32° high and sets at 11:15 PM.
The pre-sunrise eastern sky is quite active. Jupiter rises in Sagittarius at 1:23 AM, glows with minus 2 magnitude and 41 arc-seconds in size. Dwarf planet Pluto in Sagittarius, still lies 2° away, glows with 14th magnitude and 22°high. Capricornus houses Saturn and Mars. Saturn is the second to rise at 1:39 AM, twinkles with zero magnitude, is 17 arc-seconds and 5° from Jupiter. Mars rises 2:49 AM and about the same brightness as Saturn. The Red Planet is steadily growing larger in our instruments, now almost 8 arc-seconds in size.
By Civil Dawn, Aquarius houses two challenge objects. Neptune rises first, at 3:48 AM, glowing with 8th magnitude and a tiny 2 arc-seconds. By 4:30 AM it is 8° high and 15° by Civil Dawn. Dwarf Planet Ceres rises at 3:39 AM, less than 1 arc-second in size and 9th magnitude. Both should be observed no later than Civil Dawn and using charts from astronomical media. Ceres may require a large telescope.
While you are out hunting for Neptune and Ceres, you will also notice many meteors. Tuesday night is the annual Eta Aquariid meteor shower peak. Meteor showers are the result of Earth running into the debris from passing comets. In this case, the comet is the most famous – Halley’s Comet. Aquariids are famously fast and bright. Normally one could see between 16 and 30 per hour. Meteor specialists forecast this year will be more active than usual. However, conditions are not ideal. The 91% lit Moon and the early Sunrise conspire to wash out half the meteors.
With Venus so prominent, let us examine her in detail. Venus is the second planet from the Sun. It is almost an Earth twin, about the same size and slightly less mass. Early telescopic observers noted its complete cloud cover. They speculated that Venus was a lush, tropical planet. As science obtained better instruments, rude shocks came. Venus did not rotate in 24 hours like Earth; its day lasts 243 earth-days. Russian and US probes landed on Venus; pictures showed a rock filled wasteland. Those same probes recorded a toxic atmosphere with true acid rain. Since Venus is closer to the Sun, it gets twice the solar radiation. Temperatures approach the melting point of lead and atmospheric pressure is 90 times that of Earth. Its slow rotation and lack of axis tilt means no seasons or weather. Most planetary scientists now think that Venus is a case of uncontrolled global warming. Any oceans boiled off, leaving an atmosphere of 96 percent carbon dioxide. Without oceans, there was no water to capture the carbon dioxide into limestone rocks, as on Earth.