I recently received my IYA GalileoScope refracting telescope which is a working replica of the “spyglass” Galileo used during his observations of 1609-10. Would you enjoy seeing the Moon, Jupiter and Mars as they appeared to Galileo 400 years ago as he was making his amazing discoveries? I will be scheduling my Galileo star party to coincide with the First Quarter Moon around January 23rd. If you’d like to join me contact me here or check back for updates.

Galileoscopes cost just $20 and are available online. Click either the image or link above to visit the website.

For information on this event or scheduling your own a private astronomy event contact me here.

Weather here in the midwest has been cloudy and very cold during the past two to three weeks and I have been remiss in preparing obeserving updates here on the website. I tell guests at star party events that my enthusiam for astronomical observation is directly proportional to the outdoor temperature. Last weekend the skies cleared for the first time since Christmas weekend and I noticed Jupiter is still hovering to the southwest after sunset. What’s this? There are stars! So it’s time for an updated StarGeezer Observer guide. Four of the five “naked eye” planets, Mercury, Mars, Jupiter and Saturn are observable now. So, let’s begin with…

Mercury in the morning

Elusive planet Mercury will reach maximum western elongation, which means it will rise before dawn during the last two weeks of January. Mercury is challenging target because it is so small and it never appears farther than about 25 degrees from the Sun. The images of the planets out to Saturn seen above were all taken through telescopes and give a good impression of how small the angular size and appearance of Mercury are.

This elongation will be a decent morning apparition of tiny Mercury, better for those living in the southern hemisphere. Look for Mercury’s tiny orange-red disc between January 20 and February 1 with the best dates being the 21st for those of us north of the equator (14 degrees above horizon) and the 31st (21 degrees) for those in the south. You will need binoculars or a telescope to find Mercury which will rise about 90 minutes before sunrise. Try to spot Mercury’s crescent disc about 30 minutes before sunup on the dates specified. Planet Mercury’s best evening apparition for 2010 will happen in early April and it’s best morning appearance for the year in late September.

Galileo’s Starry Messenger

Observing Jupiter this month is especially compelling because Galileo Galilee began his revolutionary observations of Jupiter in January 1610. Having spent November and December 1609 observing the changing phases of the Moon in January, 1610, Galileo turned his thirty power refractor toward Jupiter. The “King of the solar system” had reached opposition in early December, 1609, thus it was visible all night long. Saturn set not long after sunset and Mars and Venus were early morning risers. It was logical then that Galileo would focus his attention on Jupiter’s bright disc. Since Jupiter was just a month past opposition it’s apparent motion was retrograde, westward or rightward against the starry background. Although not completely understood at the time astronomers of the early 17th century were aware of the retrograde motions of the planets.

On January 7, 1610 Galileo observed Jupiter accompanied by three “stars” (the Jovian moons Calisto, Europa and Ganymede). Io was occulted behind Jupiter’s disc that night. On the next clear night Galileo expected to find Jupiter to the west of those three “stars”. What he saw however was that these “stars” not only stayed with Jupiter and danced around him but there were four of them! Galileo soon realized that these were not “stars” but “planets” rotating about Jupiter. He continued his observations into March and published his findings the same month in a book called the “Starry Messenger” . This revelation profoundly changed the science of astronomy for here was proof that Earth was not the center of the Solar System or the cosmos. To be sure Galileo’s observations didn’t settle the issue. He was brought before the Inquisition in 1616. In the early 17th century you could be burned at the stake if you challenged the orthodoxy that Earth was the center of the universe. Later in 1610 Galileo observed that Saturn had “ears”, later discerned to be the ring structure by Huygens in 1655. He observed phases of Venus, all of this in 1610. Later came his postulations that ocean tides are proof that Earth rotates. Near the end of his life, in 1642, he discovered libration of the Moon. I hope you appreciate the significance of Galileo’s observations and will take the time to celebrate their 400th anniversary by observing Jupiter this month.

Jupiter is still observable in the southwest after sunset. If you’re interested in taking a peek at “Jove” don’t put it off. Jupiter sets a few minutes earlier each evening and by month’s end it will be setting less than two hours after sunset. You’ll want start observing as dusk falls before the planet’s disc sinks into the atmospheric murk. Jupiter and Venus will have a nice conjunction in mid-February but it will be a challenge to observe because both planets will appear low on the western horizon at sunset. Jupiter will reach conjunction with the Sun on February 28 so do your Jovian observing now.

Weather permitting I may present a public viewing of Jupiter using my newly acquired Galileoscope on or about June 23rd at the First Quarter Moon. Stay tuned.

Next, observing Mar’s opposition, Phobos and Deimos and watching for an asteroid.

Here’s a little Holiday treat you might want to stay up late (or get up early) for. The Ursid meteor shower peaks on the morning of Tuesday, 22 December. As you may have guessed by the name, the Ursid shower’s radiant is circumpolar, near Kochab, the “front” star in the bowl of Ursa Minor, the little dipper. Ursids are the dusty debris of comet 8P/Tuttle and tend to be faint and relatively slow moving.

The American Meteor Society offers these Ursid observing tips:

Most of the Ursid meteors are faint therefore it is important to observe from rural areas away from city lights. Since the radiant lies in the northern half of the sky it would be best to face this general direction to see the most activity. There is no need to stare directly at the radiant, rather it is advised simply to place the radiant somewhere within your field of view so that it will to easy to trace which meteors line up with Kochab (Ursids) and those that don’t (non-Ursids or sporadics). From dark skies one should also be able to count 10-15 sporadic (random) meteors per hour.

Mars in Reverse

I don’t think you’ll hear a backup warning beeper but Mars began retrograde or apparent westward motion on 21 December. What this means in practical, observable, terms is that as Earth overtakes Mars as we approach opposition in late January the Red Planet will appear to move westward against background stars. Mars will retrograde more than 10 degrees from western Leo into central Cancer during January, 2010. You might consider observing Mars at least once a week for the next month. I suggest you use the star Regulus, Leo’s “front paw” as a reference point. Measure the angular separation between Mars and Regulus by fully extending your arm and using your fist as a reference. Remember when your arm is fully extended your fist subtends 10 degrees, an open palm with outstretched fingers about 20 degrees. I’ll venture a guess that as I write this Mars is about 13 or 14 degrees west of Regulus, or “a fist and a couple of fingers”. If you’d like to know more about using using fingers, hands and fists to measure angular distances in the sky contact me here.

Mr. Moon and the Seven Sisters

The Moon will glide by the Pleiades on the evening of Tuesday, 29 December. You can observe this one naked eye but the Moon will be two days away from full and very bright. Binoculars will show a very nice view of the Moon less than a degree west (to the right) of the Seven Sisters.

Finally I should mention what will likely be the last celestial event of note during 2009 and the IYA. There will be a penumbral lunar eclipse on 31 December which will be visible in the Eastern Hemisphere. If it happens to be dark where you are at 19:23 UT (2:23 pm EST) on New Year’s Eve you’ll have to look carefully for this one. The umbral magnitude of this eclipse will be 0.082. In other words only a very tiny fraction of the Moon’s disc will fall under the Earth’s shadow.

Skies have been overcast here in southern Indiana for over a week so we’ve missed the Geminids, Mercury and the Ursids. Hope your New Year will be great and your Skies Clear!

As we discussed last week, the Moon will be “new” on Wednesday, December 16th. Look for a very slender crescent Moon on the western horizon after sunset on succeding evenings. As I’ve mentioned before I really enjoy chasing very old waning crescent and young waxing crescent Moons. Try spotting the very old Moon 47 hours before “new” on the morning of the 14th or 23 hours before new on the 15th. The 33 hour young Moon on the evening of the 17th will be a real challenge or the 57 hour young Moon on the 18th will be an easier target.

Some observers enjoy the challenge of seeing opposing crescent Moons, that is an Old crescent Moon and Young crescent Moon with the shortest period between. If you are interested in trying this and reporting your results, positive or negative, message me here.

Mercury

While you’re out watching the young Moon during evenings this week try spotting the elusive Mercury. Mercury and Venus are “inferior” planets, they orbit the Sun inside Earth’s orbit. They appear relatively near the Sun as “evening stars”  or “morning stars” from our vantage point here on the “third stone”.

Mercury will reach maximum eastern elongation, 20.3 degrees from the Sun, on 18 December. For observers in the northern hemisphere it will peak at 16.3 degrees above your western horizon at sunset on Tuesday, 15 December. This elongation does not favor observers in the southern hemisphere as Mercury will peak at 12.5 degrees above your western horizon on 22 December. Mercury is coming around toward us from the far side of the Sun and, early on in this apparition, will appear as a tiny gibbous moon half lit on the date of maximum elongation. As Mercury approaches inferior conjunction with the Sun (on 4 January) it will increase in angular size while it’s illuminated portion shrinks to a thin crescent. Use binoculars or a telescope with a low power eyepiece if you have one to view the tiny planet. See the finder chart with the view looking southwest at 5:30 pm local time on Friday, 18 December. An added treat will be the passing of the waxing crescent Moon which will appear just to the west (lower right) of Mercury on the 17th and just east (above left) of him on the 18th. Click on the chart which was generated using the Stellarium planetarium program to enlarge.

Jupiter, Neptune and the Gallilean moons

You’ll need a telescope for this exercise. This week after Mercury has set and darkness is falling look for the other bright “evening star” to the southwest. This is Jupiter. This week Jupiter and Neptune meet for their third conjunction of 2009. Jove will serve as a locator beacon for Neptune which is 6 times further away and much more difficult to spot. Compare Jupiter at magnitude -2.2 and angular size of 36 arc seconds to Neptune at +7.9 and 2.2″ wide. Observing Neptune is a challenge because of its distance. I have observed the planets of our solar system out to Uranus but never seen Neptune. On Sunday, 20 December, Jupiter will appear lass than half a degree south-southeast of Neptune. I suggest that you try to observe them over several evenings and make a sketch of their changing positions from evening to evening. Neptune will glide north to south to the west of Jupiter against the background of fixed stars. Dress warmly and give this a try.

Mars

 We’re catching up with and will pass Mars in January. The red planet is rising at about 10:30 pm now and rises out of the atmospheric turbulence around local midnight. Look for Mars at this hour above your eastern horizon east of (below and left of) Cancer near the Sickle of Leo. I think the rusty red disc of this planetary interloper stands out very obviously below and to the left of Orion and Gemini. Can you spot it?

Mars will reach opposition on 29 January, 2010, at a distance of 61.7 million miles or nearly twice the distance of the 2003 opposition. This time around its magnitude will be -1.3 and angular size 14.1″ compared to -2.9 and 25.1″ in 2003. I suggest you try observing Mars at least once a week. We’re close enough now that surface details will be revealed when viewed with telescopes of 4 inch aperature or greater. It is also interesting to observe Mars naked eye and watch it as it grows brighter as opposition approaches.

Winter Solstice

21 December is the winter solstice, the start of winter in the northern hemisphere, summer in the southern. Remember Earth is tilted 23.4 degrees to the plane of its orbit around the Sun. At the December solstice Earth’s south pole is most tilted toward the Sun. On the 21st the northern hemisphere will have the fewest hours of daylight (”shortest” day) and the southern hemisphere the longest. This tilt of Earth’s axis is the reason we have seasons, it has nothing to do with our distance from the Sun. Earth will be at perihelion (nearest the Sun) on 3 January, 2010 at about 0.983 Astronomical Unit or about 2% nearer than average. The most significant influence on our seasonal temperatures is the angle at which sunlight strikes Earth. Seasons are more extreme in the north because more of the southern hemisphere is covered by oceans. Large bodies of water smooth temperature averages.

Intuitively you may think the days are already getting longer. This is because the earliest sunset for the northern hemisphere occurred on 7 December. Because more people see the sunset than sunrise this is a popular misconception. Although the 21st is the “shortest” day in the north, earliest sunset was 7 December and the latest sunrise will be 4 January, 2010

You can get a sense of why the days are shorter by observing where the Sun rises or sets and comparing this position to a sunrise or sunset at the spring equinox next March or the summer solstice in June. Simply go outside at sunrise or sunset and make note of the position of the Sun along your horizon. Compare this to your observations in Spring and Summer. You can also see how low the Sun is above the southern horizon during the early afternoon hours.

 This panoramic image is a composite of three pictures I took looking west at sunsets in November, September and June. See how the position of the Sun changes?

The most significant astronomy, science and spaceflight stories of 2009?

I’ll post my annual poll the last week of the month. If you have a suggestion for this list please email me with it and participate in our poll. 2009 has been a year filled with changes, joy and sadness for me. I was reunited with my daughters after more than 30 years without them and lost 3 of my wonderful feline companions, Shelby age 17, Missy 16 and Dianna age 15. I miss them terribly.

I hope your 2010 will be filled with wonderful days and Clear Skies!

Mark, the StarGeezer