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Ephemeris: 12/17/2024 – A closeup look at Ganymede
This is Bob Moler with Ephemeris for Tuesday, December 17th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:03, and it will rise tomorrow at 8:15. The Moon, 2 days past full, will rise at 7:23 this evening. | Ganymede is the largest satellite in the solar system orbiting the largest planet in the solar system, Jupiter. It is 1 1/2 times the diameter of our Moon, and slightly larger than the planet Mercury. It is an icy moon, being about half made-up of water ice and silica. Ganymede appears to have a below surface ocean of water like Europa. And its surface appears to be quite smooth, not as smooth as Europa’s but parts of it are literally devoid of craters for the most part, and many of the craters it does appear to have inner craters in the center which looks quite weird. The Juno spacecraft, still orbiting Jupiter, took some very close images of Ganymede back in 2021 using its relatively simple camera. These were some of the best images of it.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 12/10/2024 – Jupiter’s four bright moons
This is Ephemeris for Tuesday, December 10th. Today the Sun will be up for 8 hours and 52 minutes, setting at 5:02, and it will rise tomorrow at 8:10. The Moon, 2 days past first quarter, will set at 3:39 tomorrow morning.
The bright star like object in the east in the evenings is the planet Jupiter. If one were to look at Jupiter through binoculars it would appear somewhat larger than a star would look. It has several dimmer stars from one side to the other of it, and if one looked the next night those little stars would have moved. Those are not stars at all, but the four largest moons of Jupiter. This would be easily apparent in the telescope. These are the four Galilean moons. They were observed by Galileo in either late 1609 or early 1610. Another astronomer, Simon Marius discovered these moons at about the same time, but Galileo was first to publish. So he gets the honor. However, Simon Marius is the one who gave them the names we know them by today. Their names, in order of their distance from Jupiter, are: Io, Europa, Ganymede, and Callisto. Each is a fascinating world in its own right.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
The periods of these satellites is interesting. Io orbits Jupiter in 1.8 days. Europa orbits in 3.6 days twice as long as Io. Ganymede orbits Jupiter in 7.2 days which is twice as long as Europa. Callisto takes 16.7 days to orbit Jupiter, and that is longer than twice Ganymede’s orbital period, and so is not in resonance with Ganymede. So the first three are in a 2:1orbital resonance with each other.
08/19/2021 – Ephemeris – Jupiter is at opposition today!
This is Ephemeris for Thursday, August 19th. Today the Sun will be up for 13 hours and 51 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, 3 days before full, will set at 4:11 tomorrow morning.
Tonight, Jupiter will be at opposition. That’s a shortcut term for Jupiter being opposite the Sun in our sky. At that time, Jupiter rises at sunset and sets at sunrise. It is also at its closest to us. It also officially becomes an evening planet, available in the evening for those of us with daytime jobs. In even small telescopes, Jupiter shows two dark bands. There’s more, but those two are the most prominent. Its four largest moons will be visible before 9:50 pm tonight, after that the innermost of the four, Io, will start to cross the face of Jupiter. It will leave Ganymede on Jupiter’s east side. On the west side will be the moon Europa, and farther out, Callisto. At 12:08 am, Io will reappear on the west side of Jupiter, joining Europa and Callisto. The moons do put on a show.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.
Addendum
Jupiter’s Galilean moons at two times tonight, August 19th at 9:30 pm (01:30 on the 20th, UT) and 12:30 am (04:30 UT). From 9:50 pm to 12:08 am (01:50 – 04:08 UT), Io will pass in front of Jupiter and be practically invisible. Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
08/04/2020 – Ephemeris – Viewing Jupiter and its moons with binoculars or small telescope
This is Ephemeris for Tuesday, August 4th. Today the Sun will be up for 14 hours and 30 minutes, setting at 9:03, and it will rise tomorrow at 6:34. The Moon, 1 day past full, will rise at 10:06 this evening.
The planet Jupiter is a fine object to view with just about any optical aid be it a pair of binoculars, spotting scope or telescope. In binoculars, if held steady or mounted on a tripod Jupiter itself will no longer look star-like, but a tiny disk. Several of Jupiter’s moons can also be seen. With a telescope four of them can be seen, the same four Galileo discovered 410 years ago. At 10 pm they will be in the same order of distance from the planet that they actually are. The two nearest will be on the west side of the planet Io the closest, the Europa the next moon out. On the east side there is the third farthest Ganymede, and farthest out is Callisto. Their orbits are nearly edge on to us, so they shuttle from one side to the other of the planet.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter and its Galilean moons for tonight and tomorrow night August 4 & 5, 2020. Those moons really move from night to night. This is shown north at the top, east to the left. Based on telescope design the image presented could be inverted, mirror image or both. Created using Cartes du Ciel (Sky Charts).
Due to the lack of time (59 seconds) I could only cover the moons. I’ll address Jupiter’s cloud features at another time. Can’t wait? Here’s a link: https://bobmoler.wordpress.com/2018/05/22/05-22-2018-ephemeris-seeing-detail-on-the-face-of-jupiter-with-a-small-telescope/
04/12/2016 – Ephemeris – Can you tell the Jovian moons apart without a program?
Ephemeris for Yuri’s Night, Tuesday, April 12th. The Sun will rise at 7:02. It’ll be up for 13 hours and 21 minutes, setting at 8:24. The Moon, 1 day before first quarter, will set at 2:22 tomorrow morning.
It’s the 55th anniversary of Yuri Gagarin’s flight as first human to orbit the Earth. Speaking of orbits, we can see Jupiter’s 4 largest moons orbit that planet in small telescopes. Their orbits are nearly edge on to us, so they seem to move back and forth from one side to the other of the planet in pretty much a straight line. So how can you tell them apart without a reference? The four moons from Jupiter in order are Io, Europa, Ganymede, and Callisto. They are not normally arranged like that. Ganymede is the brightest and Callisto the dimmest, and is usually the farthest away. Io is usually the closest appearing and has a slight reddish hue due to its sulfurous volcanic surface, and Europa is the dimmer moon close in to Jupiter. Io also can be seen to noticeably move in an hour.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
One of my old pictures of Jupiter. Callisto is obvious from its far left position and dimmer brightness. On the right, the farthest is Ganymede due to its brightness and position. Inside of it is Europa, again, dimmer than Ganymede and inside position is probably Europa. That leaves Io, which may be trying to duck behind Jupiter, as a bump in the left edge of the planet.
Jupiter and its moons as simulated by Cartes du Ciel for tonight, 10 p.m. April 12, 2016. The bodies, from let to right are Ganymede, Callisto. a background star, Jupiter, Io, and Europa.
02/19/2015 – Ephemeris – Jupiter is beginning to take its rightful place as king of the evening sky
Ephemeris for Friday, February 19th. The Sun will rise at 7:37. It’ll be up for 10 hours and 38 minutes, setting at 6:16. The Moon, 3 days before full, will set at 6:10 tomorrow morning.
Jupiter is becoming noticeable in the evening sky in the east after 8 p.m. The heavy atmosphere near the horizon make telescopic observations difficult because the planet and its satellites will appear fuzzy and have color fringes top and bottom. Wait an hour or two for the planet to rise higher into quieter and thinner air to get the best telescopic views. Jupiter is accompanied by four moons in telescopes. Tonight they’re on one side of Jupiter, with Io closest, then Europa and Ganymede close to each other, while Callisto as usual appears to be the farthest satellite. The face of Jupiter itself is crossed by dark belts and light zones that run in the same direction as the satellites orbit. The moons change position from night to night.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter, the Moon and stars tonight at 10 p.m., February 19, 2016. Created using Stellarium.
This image is shown smaller than actual size. Image expansion lately hasn’t worked. If you are using Firefox, right-click on the image, and then click on View Image.
Jupiter and its moons tonight, 10 p.m. February 19, 2016. Created using Stellarium.
Jupiter and its four Galilean moons. The planet has to be over exposed to pick up the moons. But the eye can handle the brightness difference with no problem. This is one of my old pictures I do believe.
Jupiter with its Great Red Spot November 18, 2012 by Scott Anttila.
The above image by Scott Anttila is actually much better that the image seen in small telescopes. Advances in digital photography and processing allow the stacking and averaging of many images to create better pictures by amateur astronomers with modest equipment than the best telescopes of a quarter century ago.
08/06/2015 – Ephemeris – There’s an eagle in the stars
Ephemeris for Thursday, August 6th. The Sun rises at 6:34. It’ll be up for 14 hours and 27 minutes, setting at 9:02. The Moon, at last quarter today, will rise at 12:46 tomorrow morning.
The southernmost star in the Summer Triangle of three bright stars is Altair, high in the south-southeast in the evening. It’s in the head of the constellation Aquila the Eagle. Altair is flanked by two stars, the eagle’s shoulders, and farther out are the wing tips. Other stars to the lower right are in its body and a last three in its tail. Near the tail binoculars will show a fuzzy spot that telescopes show as a compact star cluster, sometimes called the Wild Duck Cluster for its nearly triangular shape. Aquila is flying northeastward through the Milky Way, where it is split in two by a cloud of gas and dust. According to mythology the Trojan boy Ganymede was taken to heaven at the behest of the god Zeus by this eagle.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Aquila the Eagle in the southeastern sky. Created using Stellarium.
Finder chart for M11, the Wild Duck Cluster, Created using Stellarium.
06/03/2015 – Ephemeris – The visible bright planets are hanging on in the evening
Ephemeris for Wednesday, June 3rd. Today the Sun will be up for 15 hours and 23 minutes, setting at 9:22. The Moon, 1 day past full, will rise at 10:15 this evening and tomorrow the Sun will rise at 5:59.
Lets take a look at the bright planets for this week. Our brilliant evening star Venus is in the west by 9:45 p.m. It will set at 12:40 a.m. As Venus is reaching its greatest eastern elongation or separation from the Sun it is now setting earlier. Venus apparent orbit of the Sun is also tilting to a lower angle with the horizon, since though east, it is now south of the Sun. Jupiter will appear high in the west-southwestern sky about 10 p.m. It will set at 1:23 a.m. It’s near the sickle-shaped head of Leo the lion, and it’s the second brightest star-like object in the sky after Venus, which is approaching it. Saturn is in the southeast as evening twilight fades. It will set at 5:37 a.m. in the southwest.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The evening planets and bright stars, including the Moon, at 10:30 p.m. June 3, 2015. Created using Stellarium. Click on Image to enlarge.
Comparison of the apparent sizes and satellite locations of the bright planets and the Moon at 10:30 p.m. June 3, 2015. Created using Cartes du Ciel (Sky Charts) and GIMP.
Jupiter’s satellites Io and Ganymede have a busy night tonight
Satellite Event UT EDT Ganymede Transit Start June 4 0:17 June 3 8:17 p.m. Io Transit Start June 4 2:46 June 3 10:46 p.m. Io Shadow Start June 4 3:56 June 3 11:56 p.m. Ganymede Transit End June 4 3:56 June 3 11:56 p.m. Ganymede Shadow Start June 4 4:57 June 4 12:57 a.m. Io Transit End June 4 5:04 June 4 1:04 a.m. Io Shadow End June 4 6:13 * Ganymede Shadow End June 4 8:35 * * Not visible from the Traverse City/Interlochen are, Jupiter has set.
Satellite data was taken from www.projectpluto.com/jevent.htm
03/12/2015 – Ephemeris – Tonight’s a big night for Jovian satellite events
Ephemeris for Thursday, March 12th. The Sun will rise at 8:01. It’ll be up for 11 hours and 43 minutes, setting at 7:44. The Moon, 1 day before last quarter, will rise at 2:40 tomorrow morning.
Tonight will be a busy one in Jupiter’s system for those watching with telescopes. As it gets dark Jupiter’s moon Io will be in front of Jupiter and very difficult to spot. It’s shadow may be seen as a tiny inky black dot on the face of the planet. Io will move off the planet at 8:55 p.m., This will be followed by the shadow at 9:42 p.m. The fun isn’t over because the moon Europa will be appearing to approach Jupiter as Io leaves it. Europa will disappear behind Jupiter at 12:06 a.m. It will stay hidden until 4:32 a.m. Europe will clear the planet earlier, but will still be in Jupiter’s shadow until 4:32. When a moon’s in shadow, it is said to be eclipsed. When behind the planet it is occulted and when in front of Jupiter it is in transit.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Io transit end at 8:55 p.m., March 12, 2015. Note Io’s shadow will leave the face of Jupiter at 9:32 p.m. Created using Cartes du Ciel (Sky Charts).
Io passes Europa about 10:20 p.m. March 12, 2015. Created using Cartes du Ciel (Sky Charts).
Europa’s occultation begins at 12:06 a.m., March 13, 2015. Created using Cartes du Ciel (Sky Charts).
Europa emerges from eclipse by Jupiter’s shadow at 4:32 a.m., March 13, 2015. Note that Ganymede has entered the picture. It appeared to pass Io at about 3:30 a.m. Created using Cartes du Ciel (Sky Charts).
12/10/2014 – Ephemeris – Two holdout planets in the evening sky
Ephemeris for Wednesday, December 10th. The sun will rise at 8:08. It’ll be up for 8 hours and 53 minutes, setting at 5:02. The moon, half way from full to last quarter, will rise at 9:23 this evening.
In reviewing which planets are visible tonight, it looks like we’re still down to two. Venus, Saturn and Mercury are still hanging near the direction of the Sun. It will be a little while before we see them again. However we can see Mars, which will be low in the southwest at 7 p.m. It will set at 8:30 p.m. Mars’ setting time will slowly advance 5 minutes between now and the end of the year. Normal setting times for stars and planets decrease by 4 minutes a night or about a half hour a week. Mars is moving northeastward in the sky and is counteracting that. Jupiter will rise at 10 p.m. in the east-northeast. The best views in a telescope may have to wait for at least an hour after that. Jupiter is a wonderful sight in a telescope.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars low in the southwest at 7 p.m. December 10, 2014. Created using Stellarium.
Jupiter and the Moon low in the east at 11 p.m. December 10, 2014. On the evening of the 11th the Moon will appear below Jupiter. Created using Stellarium.
The moon as it would appear in binoculars at 11p.m. December 10, 2014. Created using Stellarium.
Jupiter and its moon as seen in a telescope. at 11 p.m. December 10, 2014. Note that Europa and Ganymede appear very close. They will move closer until 5 a.m. when they will appear at their closest. Created using Stellarium.
Bob Moler's Ephemeris Blog 