The Return of Jupiter and Saturn to the Evening Sky

Jupiter

    Quite a few months have passed since the local observatories have had the opportunity to provide detailed images of some of our planetary companions in the solar system. When weather conditions have allowed, the Moon has been a good substitute. When the Moon has not been available, telescope operators have turned to double stars and faint fuzzies like star clusters, galaxies and nebulae. However, these celestial objects don’t often elicit the wow factor that planetary viewing can do. Add some high thin haze, atmospheric turbulence, a little bit of moisture and light pollution, and it has been a challenge to provide decent views of the heavens. Our observing opportunities have now greatly improved.

    While amateur astronomers have been observing Jupiter and Saturn during hours when most people are in REM dreamland, from now through November telescopes throughout Rhode Island will focus on exquisite views of these two gas giant worlds and all their glory. All I can say is, “It’s about time!!” This month’s column will provide a brief observing guide to Jupiter. Next month I will feature Saturn.

    Back on June 10 Jupiter reached opposition. That means it rose as the Sun was setting. This date was also the date of Jupiter’s closest approach to the Earth for this year—about 397,850,855 miles. By July 1 this distance will have increased to 403,576,313 miles as the Earth pulls out ahead of Jupiter in our respective orbits. Fortunately, views of  the Jovian system do not suffer dramatically from rapidly increasing distance.

    However, Jupiter currently traverses a shallow arc across the sky because it, and all the planets, follows the ecliptic (path of the Sun and the plane of the solar system). Unfortunately because the ecliptic is low in our summer night sky, this scenario will keep Jupiter within some of summer’s often murky atmospheric conditions no more than 26 degrees above the southern horizon. Regardless, Jupiter reveals much detail even with small amateur telescopes.

    First, you need to locate Jupiter among the constellations. Currently Jupiter resides among the stars of a not so obvious pattern of stars called Ophiuchus. Lucky for us a more recognizable Scorpius is a neighboring star pattern. See the following star map.

Location of Jupiter and Saturn in the sky on July 1

Bright Jupiter will be to the east (left) of Scorpius’ brightest star, red Antares. Focus in on Jupiter with your own telescope and begin your exploration, or let the volunteers at the local observatories guide your viewing pleasure.

    It’s hard to predict what you will notice first. Will it be Jupiter’s large striped disk, or will it be some of his moons that grab your attention?

    Let’s begin our examination with the planet itself. Jupiter is quite large; you could fit 1,321 Earths within its volume. Despite its distance from the Earth, this giant world is exciting to observe through any sized telescope. The striped appearance of the primary dark bands and lighter zones are easy to see, though the famous centuries old Great Red Spot (GRS) is no longer very great Over the last 150 years or so detailed measurements have revealed that the GRS has shrunk by 50%, and in more recent years its oval shape has become more circular.

    In fact, some astronomers have speculated that this long-lived storm may be dissipating. Recent observations have revealed that the GRS exhibits indications that it may be “unraveling.” We may be witnessing an historical event in the near future if this degeneration continues. Review this link for details about the recent GRS event:

    While the color of the GRS has changed throughout the decades, its lighter salmon coloring has made it a little more difficult to detect during the last decade. However, according to a recent Sky and Telescope article, “Over the last few years, the GRS has been sporting a rich, orange-red color…” This color enhancement makes the GRS much easier to detect if it is facing the Earth. Transit times of the GRS . Keep in mind that Jupiter rotates once in ten hours, so each night you will see different views of the planetary disk.

    Or exploration of Jupiter will now focus on his four prominent satellites, called the Galilean moons in honor of their discoverer Galileo Galilei on January 7, 1610. These moons, given names from Greek mythology, are Io, Europa, Ganymede and Callisto. They are easily observed in small telescopes as they orbit around Jupiter. When several of the moons are visible at the same time, they often appear in a straight line, parading around Jupiter in the plane of its equator. This arrangement presents many interesting phenomena for us earth-bound astronomers to observe.

    When a moon passes in front of Jupiter and casts a shadow onto the Jovian cloud tops, it is called a shadow transit. Besides seeing the satellite’s shadow, you may also see the bright disk of the satellite traversing Jupiter’s clouds at the same time, though this event is more difficult to observe. A moon may also pass behind the planet, which is called an occultation. Jupiter’s shadow can even eclipse a satellite as well; gradually the moon will either blink out or reappear. Also, it’s fun to watch all four moons line up on one side of the planet. I love to watch Jupiter over an extended period of time during the course of one evening because the view is dynamically changing as you watch.

Saturn Preview

        In conclusion, if you just can’t wait for my Saturn observing guide next month, this beautiful ringed world comes to opposition on July 9 in the constellation of Sagittarius. Since Saturn also tracks across the sky on the ecliptic it will take some time to rise high enough above horizon haze to observe. If you wait until July 15 at 11:00 p.m. you will find Saturn to the left of Sagittarius’ “teapot handle” asterism. About one degree to the right will be a waxing gibbous Moon, just one day from Full. More details next month.

    Over the next five months I encourage you to drag those telescopes you may own out of the attic or up from the basement and have them collect the light of Jupiter instead of dust! If you don’t have a telescope, or you wish to observe greater detail than what it could provide, please visit one of the local observatories for incredible views of Jupiter, Saturn and other astronomical objects. Seagrave Memorial Observatory in North Scituate is open every clear Saturday night. Ladd Observatory in Providence is open every Tuesday night. The Margaret M. Jacoby Observatory at the CCRI Knight Campus in Warwick is open every clear Thursday night. Frosty Drew Observatory in Charlestown is open every clear Friday night. Be sure to check the respective websites for any schedule update before venturing out for a visit.

Summer Stargazing

Summer Solstice

    As we approach the Summer Solstice in the northern hemisphere, this year on June 21 at 11:54 a.m. EDT (Eastern Daylight Time), here in Rhode Island many folks revel in the extra daylight hours, especially in the evening. Astronomers are not among those individuals because our skies do not get fully dark until about 10 p.m., and dawn’s early light starts around 4 a.m. That leaves little time to explore the universe with telescopes and cameras to capture the beauty of the heavens. Then as the summer months continue, we must contend with high humidity and pesky mosquitoes.

    However, there are a couple of planets we will welcome back to the evening sky over the course of this summer. They are Jupiter and Saturn. These distant worlds reveal much detail in the telescopes at the local observatories.

Jupiter and Saturn

    Jupiter will reach opposition on June 10. That means it will rise as the Sun sets. That is also the date of its closest approach to the Earth for this year. Unfortunately, the late rise time on June 10 means some of the local observatories may not be able to focus on Jupiter due to their respective horizon views. Also, because Jupiter will rise in the southeast and travel along a shallow arc across the sky, it will take some time to clear the often murky atmospheric conditions low to the horizon.

    I do not wish to discourage one from observing Jupiter if you can. Even as this column goes to press during early June you could wait until Jupiter rises much higher into the sky to begin observing it. My associates have been observing Jupiter in the early morning sky for months (when the weather cooperated). I will provide a Jupiter observing guide in my July column.

    Two hours after Jupiter rises, our solar system’s most beautiful ringed-world Saturn will rise. Saturn too will take a similar arced path into the sky, so it also will not rise very quickly above the horizon. You should wait a few hours before observing Saturn and his magnificent rings. Saturn reaches opposition one month later on July 9. My observing guide to Saturn will also be included in my July column.

Mercury and Mars

     Within 20 minutes or so after sunset (8:24 p.m. EDT) on the evening of June 23 you can catch a glimpse of our solar system’s innermost planet Mercury. Look about 10 degrees (a fist held at arm’s length provides this measurement) above the west-northwest horizon. You’ll require an unobstructed view to succeed in this observing challenge. Furthermore, an even more challenging task will be to locate the red and dimmer planet Mars 2.5 degrees below and to the right of Mercury. The gauntlet has been dropped. Who will accept and succeed in this challenge?

Hercules   

    One of the jewels of the summer sky resides in the constellation of Hercules. I’m referring to the showpiece of northern hemisphere globular clusters, M13, so designated for being the 13th entry in the sky catalog of 18th century astronomer Charles Messier. This object contains hundreds of thousands of stars. Once you know where to look, M13 can still be detected with the naked-eye as a fuzzy patch from dark-sky locations in Rhode Island.

    You can locate Hercules on June 1 about halfway up in the eastern sky around 9:30 p.m. Find the bright star Vega in the constellation of Lyra and Hercules will be the neighboring constellation to its upper right. Four main stars called the keystone outline the body of Hercules, while two streams of stars form his arms and another stream comprise his legs. Though his extremities look like a stick figure, Hercules has been bulking up on his body. While the constellation has a rich mythological history, space does not permit me to relate it here. Just suffice it to say that the star pattern represents the mighty Hercules of “twelve labors” fame kneeling upon the head of Draco the Dragon, holding a club in one hand, and a branch in the other.

   To locate the globular cluster please reference the above star map. M13 lies between the two stars that form the western side of the keystone. It is about one-third of the way from the northern most star of the keystone. If you can’t detect it with your naked-eye, try using a pair of binoculars. It looks like a small tail-less comet.

    Once you’ve found M13, use a telescope if you have one. A small refractor will show it as a small diffuse patch of light, much like the nucleus of a comet. Larger scopes, say a four- or six-inch reflector, will begin to resolve individual stars within this beautiful beehive of stars. And the beehive description is quite apt, for if one could speed up time you would see these stars, which are all gravitationally bound to the cluster and number about 300,000, orbit the cluster like bees around a hive.

    One of my favorite turn of the 20th century authors is Garrett P. Serviss. I often quote him in my columns because he had such a descriptive and poetic style of writing. For your enjoyment I have excerpted a quote concerning M13 from his wonderful book, Pleasures of the Telescope.

    “…smaller instruments reveal only the in-running streams and the sprinkling of stellar points over the main aggregation, which cause it to sparkle like a cloud of diamond dust transfused with sunbeams.” “It is a ball of suns. Now you need a telescope. You must have one. You must either buy or borrow it, or you must pay a visit to an observatory, for this is a thing that no intelligent human being in these days can afford not to see. Can it be possible that any man can know that fifteen thousand suns are to be seen, burning in a compact globular cluster, and not long to regard them with his own eyes?”

    On the next clear and moonless night, go out and locate the great Hercules in the sky. Binoculars will certainly show you M13, but a telescope will reveal all its splendor. Telescopic views through the larger telescopes at the local observatories are quite impressive. Think about the above description while you enjoy the image.

    Take advantage of the viewing opportunities provided by the local observatories as the summer months progress. Jupiter and Saturn will be the primary focus of attention from mid-summer onwards into fall. In addition will be various phases of the Moon, as well as looks up and down the expanse of our own Milky Way galaxy. Remember, summer brings late sunsets, so please check the respective observatory websites for their open dates and times before venturing out for a visit. Seagrave Memorial Observatory in North Scituate is open every clear Saturday night. Ladd Observatory in Providence is open every Tuesday night. The Margaret M. Jacoby Observatory at the CCRI Knight Campus in Warwick is open every clear Thursday night. Frosty Drew Observatory in Charlestown is open every clear Friday night.

    Keep your eyes to the skies.

A Meteor Shower, a Blue Moon, and No More Iridium Flares


May Meteor Shower

   It’s challenging to explain to someone that you spent a below-freezing December night sitting on your back porch bundled up in a sleeping bag on a lounge chair just to watch a few meteors blaze across the sky. Why? Because sometimes even I question why I choose to do so. A few months back the Geminid meteor shower did not perform well around here, at least not when I decided to observe it. After about an hour and a half I counted less than a dozen meteors, and not all of them were Geminids. Only a couple of them were bright enough to elicit a wow, though not loud enough to wake my neighbors!

    That’s the way it is with meteor showers. Sometimes you’re in the right place at the right time to see the meteors to best advantage. Other times you are not. It can be frustrating when the latter occurs, especially when the weather conspires against you. Still, after all my decades of stargazing I never tire of watching for meteors to fall from the sky.

    The early days of May present us with warmer weather prospects to enjoy a somewhat “meteor-ocre” display of shooting stars. During the pre-dawn hours of May 5 and 6, the Earth will be sweeping through a stream of particles shed by Halley’s Comet long ago. (Either morning will be a fine time to observe since the Eta Aquarids do not have a sharp peak. The meteors comprising this meteor shower enter the Earth’s upper atmosphere head-on at 41 miles per second. While the Moon will not interfere with observing this shooting star display this year (New Moon is on the 4th), one can expect to see no more than 10-15 swift and yellow shooting stars per hour from Southern New England. Why? The Eta Aquarids, are best observed from the southern hemisphere.

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Astronomical Events Determine Easter Observance

In simpler times our forefathers paid close attention to the clockwork motion of the heavens. One didn’t have to observe the sky for too long a period of time to notice the cyclic phases of the Moon, or the changing position of the Sun relative to the horizon over the course of a year. Nature provided a precise clock and calendar that could be used to determine when to celebrate special events.

It should therefore not be surprising that many religions observances would likewise be established in accordance with those same astronomical circumstances. Christians, for instance, observe Easter every year, but the date for the celebration changes. Since we can barely even remember birthdays and anniversaries that always occur on the same date, it’s time for me to enlighten you with the facts of how the date for Easter is determined.

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Reason for the Seasons

Folklore tells us that March comes in like a lion and goes out like a lamb. While March is meteorologically a spring month, here in New England and other mid-latitude locations throughout America, it is still cold and snowy when it commences and much milder and rainy at month’s end. Hence the comparison to the ferocity of a lion and the tranquility of a lamb. However, this explanation, attributed to the early American Colonists, is not globally applicable. We must turn to astronomy for a more inclusive answer.

It’s really quite simple. When March begins, the constellation Leo the lion is rising above the eastern horizon just after sunset, and at month’s end Aries the ram can be found setting below the western horizon at sunset. This sky clockwork has not appreciably changed for thousands of years. Our ancestors observed the appearance of these star patterns and ascribed significance to their seasonal arrival and departure in the sky.

Most everyone links the weather with seasonal changes. However, through my decades of public outreach and teaching astronomy, I know many folks are misinformed as to the reason for the season(s). Some individuals believe the northern hemisphere summer is hot because the Earth is closest (perihelion) to the Sun at that point in its orbit. Quite the opposite is true. Earth is at perihelion (approximately 91,000,000 miles) in early January, while farthest (aphelion) from the Sun at the beginning of July (approximately 94,000,000 miles). Even this three million mile difference has little effect on the Earth and its environment. The seasonal changes are the result of the Earth’s axial tilt as it orbits the Sun.

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