Venus | A Narrowing Crescent

Viewed from Earth, the crescent of Venus narrows each day as it orbits the Sun. On 25 March 2017, it will be aligned almost directly between Earth and the Sun. In the weeks following, Venus will appear as a morning object and a thin crescent. Go here to see a 3D tool showing the orbital positions of the inner planets today. Notice the Date and Date Slider controls where you can change the date and see the planets move.


Venus 15 February 2017


Date Time Digitized: Feb 15, 2017, 6:05:33 PM CST
Exposure Time: 1/500 s
Photographic Sensitivity (ISO): 100


NASA Twins Study | Early Results Reported

Astronaut twins Mark and Scott Kelly participated in a study conducted by ten researchers on the effects of long duration space flight. Scott was aboard the International Space Station for 340 days while Mark remained on Earth. Scott returned to Earth 1 March 2016. For details about his return, read this previous post.

Ten researchers reported preliminary results on 23 Jan 2017 in Galveston TX of their comparative studies of the twins. The NASA issued statement is here. I’ll attempt to summarize eight of their findings below.

Credit: NASA

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Dial-a-Moon | 2017

How will the Moon look today, on your birthday, or any date in 2017? Find out at NASA Dial-a-Moon. Enter any month, day, and universal time (UT) hour to see a high definition image. The composite images of Dial-a-Moon are made from those of the Lunar Reconnaissance Orbiter (LRO) in low altitude orbit around the Moon since 2009. Here is the link for southern hemisphere readers.

You may leave the universal time (UT) at the default 1 value. If you are a curious type, Universal time conversion can be done at this link. Enter UTC in the lower right box if it isn’t already set. You can switch from 12 hr to 24 hr at the bottom of the entry boxes. You may also enter any other local time in the upper left box. Go back to Dial-a-Moon to enter the UT.

The collection of accurate images of the Moon for each hour have been made into a movie lasting 5 minutes. Try watching full screen and increase the speed by 2x. Speed can be changed using the gear icon ⚙  after the movie starts. Two versions of the movie are available for readers in northern and southern hemisphere.

I explain the peculiar wobble and tipping motions at this blog post.

Northern hemisphere


Southern hemisphere

Jupiter and Mercury | Iridium 98 Flare

Mercury has been visible in the early morning twilight recently. Jupiter is on the opposite side of the Sun from our location. But, Earth is coming around in our orbit catching up to Jupiter. As a result, Jupiter is also a morning twilight object in the same vicinity as Mercury. They were to be very close to each other low in the eastern sky on 11 Oct 2016. Guess what. It was cloudy. But, I did go out on 10 Oct at 6:45 am when it was very clear to capture the view.

The first image is how it looked to my unaided eyes. The second image is zoomed into the center part of the first just above the tallest trees in the vicinity of a faint jet trail.

They are in there somewhere in the middle.

They are in there somewhere in the middle.



The evening on 9 Oct was also clear. An email notice told me about a bright reflection off of a communication satellite that was to pass right over my location. The satellites are part of the Iridium system consisting of 72 satellites in polar orbits that provide worldwide coverage for satellite phones. Their 3 antennae shown in the image below are flat and highly reflective of sunlight. The positions and angles of each antenna are known allowing predictions of those reflections across the surface of the Earth.

Iridium LLC

The email notice said the location in the sky was toward 148˚ in the southeast and 50˚elevation. It would last about 10 sec due to the 17,000 mph speed of the satellite.

The sky was dark. I set the camera using a protractor for elevation and Google Earth for direction over my neighbor’s house. I started recording a minute before the due time of 7:52 pm. Success. Here is the video trimmed for time to the actual event.

Sturgeon Moon | 17 Aug 2016

We were fortunate to have clear sky last evening. The nearly full Moon rose above the southeast. Here it is about 6 hours before full. Full phase was at 4:27 am CDT on 18 August.



According to the Old Farmer’s Almanac, this is known as the Sturgeon Moon.

Some Native American tribes called the August Moon the “Sturgeon Moon” because they knew that the sturgeon of the Great Lakes and Lake Champlain were most readily caught during this Full Moon. They also called August’s Moon the “Full Green Corn Moon.”
Different tribes had different Moon name preferences. Other examples for August are: “Wheat Cut Moon” (San Ildefonso, and San Juan), or “Moon When All Things Ripen” (Dakotah Sioux) or “Blueberry Moon” (Ojibway).

Mars | Antares | Saturn | A Triangle

Fellow blogger and sky enthusiast, Scott Levine, pointed out the grouping of two planets and a star in the southern sky in recent nights. Our overcast conditions finally parted and gave us a beautiful view of the grouping the evening of 13 August 2016.

It was about 9 pm local time as we headed home from a gathering of about 30 friends. We have all been to Cuba in the past 3 years and were celebrating with some Cuban foods and drinks. We looked to the south and saw this view exactly as Scott described it. That is the roofline of our house at the bottom right.

Click to embiggen

Click to embiggen

Below is a screen shot of the same part of the sky taken from the software Stellarium. Each planet and some stars are labeled. Since Mars and Saturn are in orbits around the Sun, their positions in the sky change each night. Their arrangement with Antares looks different each night. Watch their progress.


Jupiter | Harmony of Motion

Galileo used a telescope to cast his eyes upon Jupiter and its moons Io, Europa, Ganymede, and Callisto in 1610. He recorded notebook drawings of their positions nightly. He believed they moved around the planet Jupiter in what appeared to be orbits. His views were but snapshots in time.

Galileo Galilei | Siderius Nuncius | 1610

Telescopes improved over time. Technology brought us better views. Spacecraft Voyager and Galileo gave us marvelous images of the moons. But, those detailed images still gave us only snapshots in time. Those amazing views still lacked the perspective needed to show them in actual orbit about Jupiter.


Our view of the moons changed with the arrival of the Juno spacecraft on 4 July 2016. It approached Jupiter from above the plane of the orbits of Jupiter and its moons. The perspective allowed the JunoCam camera onboard to image the system multiple times for 17 days between 12 June and 29 June. The still images were made into a movie which shows the four moons in orbit several revolutions around the massive Jupiter.

Notice how the innermost moon Io orbits quickly. The farther moons more slowly. The planets of our solar system behave this way. All bodies in the universe orbit other bodies this same way. We are seeing from a unique perspective above the orbit plane. We are witnessing firsthand the effect of the law of gravitation. It is a thing of beauty. In addition, the three inner moons darken briefly as they pass into the shadow of Jupiter in each orbit.

Quoting Scott Bolton, principal investigator of Juno, Southwest Research Institute:

“This is the king of our solar system, and its disciples going around it. It’s also representative of nature. This is how we look, that’s a mini solar system. And so, I think, to me it’s very significant because we’re finally able to see, with real video, real pictures, this motion. And we’ve only been able to imagine it up until today.”