Steve’s Virtual Planet

Jan 7, 1610

As we start the New Year, this is as good a time of year as any to find inspiration from history. Today is one of those recollections of a day when our world changed over night (well, at least once the data was published in March 1610!).

On Jan 7, 1610, the discovery of three of Jupiter’s moons by Galileo Galilei and a fourth one on Jan 15, provided the evidence that the heliocentric theory proposed by Copernicus was indeed valid. As the details were actually put in print in Galileo’s book Siderius Nuncius (The Starry Messenger), the simple fact of this discovery was not only a wonderful revelation of nature but a complete rebuttal of the idea that the Earth was the center of … well, everything!

This so-called geocentric hypothesis had held sway since the days of Ptolemy (c. 100 – c. 170 AD). However, what Galileo clearly saw, magnified in the telescope, was another world in our solar system that had not been revealed like this before. And since the moons could be shown to orbit the planet, it meant they were NOT orbiting the Earth!! One might say that this discovery shook things up a little!

He might have seen something like this representation on January 7th through his homemade 20 power telescope. From left to right, the objects in the view are Ganymede, Jupiter, Europa, Io & Callisto.

In the simulation above, Callisto and Ganymede are the farthest out but Io and Europa are very close together. So, Galileo may not have been able to split them that first night. Nevertheless, his persistence and continued observations over the next few nights showed clearly how the moons were shifting position in relation to Jupiter itself and the entire collection was drifting against the background star field. To him, this movement of the objects were the clincher in concluding this was not just a planet, but one with orbiting moons.

This set of observations comprised one of the most consequential discoveries in the history of science. Due to Galileo’s keen sense of the importance of the observation and the empirical method he was indeed a giant of the age of modern science. Einstein himself in 1933 referred to Galileo as “the father of modern physics and and in fact of the whole of modern natural science.”

That is powerful inspiration indeed.

originally posted on Jan 7, 2025

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Jupiter’s New Year Return

It’s now well after the Winter Solstice and shorter days are still the rule; sunsets coming earlier paving the way for evening viewing and just in time for the return of Jupiter in the mid evening skies. So the shift grants even more time for catching the king of planets.

Now would be a good time to begin this season’s Jupiter viewing, coming off of the eastern horizon at 5:30 PM, EST. By late January, Jupiter will be rising much earlier and easier to catch in the evening hours.

Jupiter will be with us in the evening sky through early June. Plenty of time to explore the moons and features of our largest planet.

More on Jupiter in the coming weeks as the King of the Solar System brings another great season of Big Planet views. Stay tuned!

originally posted on 12-13-14

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Full Moon Names - September

The most common traditional full moon name for September is the Full Harvest Moon. This month’s full moon appears already full on Sunday, September 7th, around 2:09 PM EDT.

Check the almanac references in the links below:

From the older Old Farmer’s Almanac - September Full Moon. See the article to access a moon rise calculator. There are also alternative names from early American history various native cultures.

From the newer Farmer’s Almanac - September Full Moon. There is a deeper explanation of the history of the Full Buck moon in North America and some additional alternate names.

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Saturn is back for 2025

Saturn is back in the late evening sky again for 2025 and easy to find in the southeastern sky after about 10:00, in the western part of the constellation Pisces. The ringed world has been getting higher in the sky daily, making for better views each week.

Opposition is on September 20 for this apparition and the rings are around 2 degree tilt, almost a straight line (edge on) but still looking very impressive. During this event, the rings will be their brightest due to the Seeliger Effect. Here’s a detailed account of this phenomenon as description by renowned observer Stephen James O’Meara. The Cassini division will still easy to make out with the rings still exposed in the eastern and western edges.

Looking ahead to October, I hope to get get some good views of the ringed planet through Fernbank’s 36 inch Cassegrain. There will be plenty of opportunities to catch the Lord of the Rings through Christmas and from late October, it will share the night sky with Jupiter. In the telescope, the Saturn’s pail yellow color is a easy to detect and fun to compare to the richer hues of Jupiter to the east.

EarthSky has some great resources for viewing the visible planets so you can keep up with all of these solar system objects in advance.

Wish you great views of Saturn this year! Clear skies!

First published Aug 7, 2024, Update Aug 27, 2025

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Full Moon Names - August

The most common traditional full moon name for July is the Full Sturgeon Moon. This month’s full moon appears early on Saturday, August 9th, around 3:55 AM EDT. In the evening that same day, the moon will rise around 9:01PM and should clear the tree line around 10:20PM. As a bonus, the moon will reveal a close conjunction with planet Saturn two nights later!!

Check the almanac references in the links below:

From the older Old Farmer’s Almanac - August Full Moon. See the article to access a moon rise calculator. There are also alternative names from early American history various native cultures.

From the newer Farmer’s Almanac - August Full Moon. There is a deeper explanation of the history of the Full Buck moon in North America and some additional alternate names.

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Full Moon Names - July

The most common traditional full moon name for July is the Full Buck Moon. Summer is here in full force and this months full moon appears early on Thursday, July 1th, right after sunset. In the evening, the moon will rise around 9:15 PM and should clear the tree line between 10 and 11 PM. Check the almanac references in the links below

From the older Old Farmer’s Almanac - July Full Moon. See the article to access a moon rise calculator. There are also alternative names from early American history various native cultures.

From the newer Farmer’s Almanac - July Full Moon. There is a deeper explanation of the history of the Full Buck moon in North America and some additional alternate names.

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How long is a month?

If you check deeper into the meaning of “month”, you quickly find Earth’s moon right at the center of the explanation. It turns out that the ancient Babylonians pretty much started this examination in the years around 500BC. These early mathematicians and astronomers took extra care in watching and noting the movement of the moon. They came up with several methods and terms to show how the moon tracked around the Earth and how long it took.

There are different ways to describe Earth’s orbit and the orbit of the moon around our planet. Its related to the geometry and timing of those orbits. The method for describing the complete cycle of the moon phases is known as the synodic month. This is the view of the moon from Earth’s perspective and is relative to our point of view. The other method has a more general and wider viewpoint and it is known as the siderial month.

In order to get a better feel for these two concepts, it’s handy to have some kind of diagram or, even better, an animation to show the Moon phases as it orbits the Earth. If you can get your mind around the geometry from your perspective and the solar system perspective (as in the animation), it’s easier to see how “the month” is defined in both of the methods above.

Ultimately, we are talking about lunar calendar systems and there are actually quite a few. The ancient astronomers weren’t just moon gazing but trying to understand what they were looking at. Their persistence lead to what is now a very refined but kind of crazy way of showing what month it is. After all, we want everyone to know our Birthday in time or maybe we just want to take a month off!

First published 3-19-2016; Updated 7-1-25

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Full Moon Names - June

The most common traditional full moon name for June is the Strawberry Moon. Check the alternate names in the links below. Summer is on the way and this months full moon happens on the solstice.

This year, the full Moon appears on Wednesday, June 11th. In the eastern US, the moon will rise just after sunset, around 8:48 PM and should start clearing the tree line around 11:30 PM.

From the older Old Farmer’s Almanac - June Full Moon. See the article to access a moon rise calculator. There are also alternative names from early American history various native cultures.

From the newer Farmer’s Almanac - June Full Moon. There is a deeper explanation of the history of the worm moon in North America and some additional alternate names.

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Summer Geometry

The night sky is peppered with all kinds of star patterns that have fascinated human kind for untold centuries. These patterns were thought to be gods and creatures of all kinds, kindly (mostly) looking over our affairs here on Earth. For the grander groups of stars, we save the name constellation. But sometimes smaller groups appear that have an even grander attraction. We call these patterns either within (or without) their constellations asterisms.

One of the most recognizable asterisms in the sky is the Summer Triangle. Unlike many other asterisms that are confined to one constellation, with the Summer Triangle, you get three for the price of one! The key stars in The Triangle are as follows: Vega in the constellation Lyra (The Lyre), Deneb in Cygnus (The Swan) and Altair in Aquila (The Eagle). Vega is the brightest of the three and easy to find through the summer into early Fall. Once you get to know how the Triangle is placed in the sky, you can also use it as a guide to other constellations and stars. This month, you can catch this fairly bright asterism clearing the tree tops after about 10:00PM in the eastern sky and it will stay flying overhead into October.

Follow the links above to get details on these different objects. You’ll find that the three constellations have long been associated with birds of some kind, no matter what culture is gazing up. If you’re keen to investigate the mythology, check your local library for Richard Hinckley Allen’s “Star Names: Their Lore and Meaning”. It’s one of the great modern resources for ancient astronomy.

Regardless, you can revel in the magic of the Three Mythical Birds of Summer!

Originally published 6-12-15, revised 6-1-25

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Full Moon Names - May

The most common traditional full moon name for May is the Flower Moon. One might think of spring time and the trees and shrubs in bloom, but check the alternate names in the links below,

This year, the full Moon appears on Monday, May 12th. In the eastern US, the moon will rise at 8:56 PM and should start clearing the tree line around 11:00 PM.

From the older Old Farmer’s Almanac - May Full Moon. See the article to access a moon rise calculator. There are also alternative names from early American history various native cultures.

From the newer Farmer’s Almanac - May Full Moon. There is a deeper explanation of the history of the worm moon in North America and some additional alternate names.

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