Archive
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.
04/14/2015 – Ephemeris – Arcas and Callisto
Ephemeris for Tuesday, April 14th. The Sun will rise at 7:00. It’ll be up for 13 hours and 25 minutes, setting at 8:26. The Moon, 3 days past last quarter, will rise at 5:08 tomorrow morning.
Rising in the eastern sky at 10 p.m. tonight is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite, pointed to by the arc of the handle of the Big Dipper, overhead. In one story Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief Greek god. Zeus’ wife Hera, found out about it, and since she couldn’t punish Zeus, turned Callisto into an ugly bear. Arcas, unaware of why his mother disappeared in his youth was about to kill the bear when Zeus intervened and placed them both in the sky. Now Arcas as Boötes chases the Great Bear forever around the pole of the sky each night.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.
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12/03/2014 – Ephemeris – Bright planets: One early and one late
Ephemeris for Wednesday, December 3rd. The sun will rise at 8:01. It’ll be up for 9 hours and 1 minute, setting at 5:03. The moon, 3 days before full, will set at 5:48 tomorrow morning.
In reviewing which planets are visible tonight, it looks like we’re still down to two. Venus, Saturn and Mercury are hanging around 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 8:29 p.m. Mars’ setting time will slowly advance only 6 minutes between now and the end of the year. Jupiter will rise at 10:28 p.m. in the east-northeast. The best telescopic views will have to wait a couple of hours after that. So if you’re more of an early bird rather than a night owl it might be better to view Jupiter with a telescope in the morning. Jupiter has those four bright moons that change position daily, and sometimes while you watch.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars in the southwest at 7 p.m. December 3, 2014. Created using Stellarium.
A binocular view of what the moon will look like at 7 p.m. December 3, 2014. Created using Stellarium.
Jupiter rising with the winter constellations at 11 p.m., December 3, 2014. We’re actually looking at the eastern half of the sky. Created using Stellarium.
At 6 a.m. December 4, 2014 Jupiter and the winter constellations will swing into the southwest while out of the view the spring and early summer stars take over the eastern sky. Created using Stellarium.
Telescopic view of Jupiter at 6 a.m. December 4, 2014. The moons on the left in order from left to right are Callisto, Ganymede and Europa. In the next hour the moons will appear to get even closer together, especially Ganymede and Callisto. Created using Stellarium.
01/09/2014 – Ephemeris – More on Jupiter’s Galilean moons.
Ephemeris for Thursday, January 9th. The sun will rise at 8:18. It’ll be up for 9 hours and 3 minutes, setting at 5:21. The moon, 2 days past first quarter, will set at 3:20 tomorrow morning.
The planet Jupiter has, as of the latest count, 67 satellites or moons. However only four can be seen in small to medium-sized telescopes. Astronomers use the term moon and satellite interchangeably, though only moons orbit planets. A satellite is a more generic term and is a smaller body that orbits another larger body. Though we don’t usually call an artificial satellite orbiting the Earth a moon. Anyway, the four bright moons of Jupiter are called the Galilean moons, because Galileo discovered then in early 1610. Their names from Jupiter on out are Io, Europa, Ganymede and Callisto. They orbit over Jupiter’s equator. Since the planet has a very small axial tilt the moons seem to move back and forth from one side to the other of Jupiter in a nearly straight line.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
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 a solar eclipse in progress as Ganymede, lower left, casts its shadow on Jupiter on November 14, 2011 at about 10:15 p.m.. Credit: Scott Anttila.
The moon Io is off to the far left. This eclipse can be simulated with Cartes du Ciel.
05/28/2013 – Ephemeris – Boötes the bear chaser
Ephemeris for Tuesday, May 28th. Today the sun will be up for 15 hours and 14 minutes, setting at 9:17. The moon, half way from full to last quarter, will rise at 12:34 tomorrow morning. Tomorrow the sun will rise at 6:02.
Appearing high in the southeastern sky at 10:30 tonight is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite, pointed to by the arc of the handle of the Big Dipper, overhead. In one story Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief Greek god. Zeus’ wife Hera, found out about it, and since she couldn’t punish Zeus, turned Callisto into an ugly bear. Arcas, unaware of why his mother disappeared in his youth was about to kill the bear when Zeus intervened and placed them both in the sky. Now Arcas as Boötes chases the Great Bear forever around the pole of the sky each day and night.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Bootes and Ursa Major high overhead on late spring evenings at 11 p.m. Created using Stellarium.
01/11/2012 – Ephemeris – Where are the planets tonight?
Wednesday, January 11th. The sun will rise at 8:17. It’ll be up for 9 hours and 5 minutes, setting at 5:22. The moon, 2 days past full, will rise at 8:29 this evening.
It’s time again to take a look at the whereabouts of the bright planets. Venus is brilliant in the southwestern sky after sunset and will set at 8:25. Jupiter is the most prominent planet of the evening sky, once Venus sets. It’s located high in the south and is seen against the stars of the constellation Aries. It will pass due south at 7:15 p.m. It will set at 2:00 a.m.. Jupiter is a great sight in a small telescope with its four moons which change position from night to night. Mars will rise at 10:27 p.m in the east northeast and is below the hind end of the constellation Leo the lion. It is 88 million miles away and closing. Mars will pass due south at 4:54 a.m. Saturn will rise at 1:41 a.m. just to the left of the bright star Spica in the east southeast.
* Times, as always are for the Traverse City/Interlochen area of Michigan.
Addendum
Overexposed Jupiter and its moons. My archival image.
The four Galilean satellites or moons of Jupiter are in order of distance from Jupiter Io, Europa, Ganymede and Callisto. They all orbit near Jupiter’s equator, and Jupiter itself has a very small axial tilt of about 3 degrees so the satellites seem to shuffle from one side to the other of Jupiter. The pattern is different night.
The programs Stellarium, Cartes du Ciel, and other sources including http://www.calsky.com can be used to determine the positions of the satellites. But there are clues by just looking at them.
- Io is closest to Jupiter and generally appears so. In the photograph above it appears as a bump on the left edge of Jupiter. It has a slight reddish tinge.
- Europa is dimmer than Io and also is usually close to Jupiter.
- Ganymede is easy. It’s the brightest.
- Callisto is usually found the farthest from Jupiter and is also the dimmest of the four.
Based on the photograph alone, which is undated, I’d guess that from left to right we have Callisto and Io to the left of Jupiter, Europa and Ganymede to the right.
Sometimes fewer than four satellites can be seen. They can hide in front of Jupiter, usually casting their shadow on the planet, behind Jupiter or in its shadow. Calsky will give you the times for your location.
Update
I located the date of the above image. It was taken the evening of March 17, 1989. A check with Cartes du Ciel (Sky Charts) confirm the satellite’s locations and order. Io was just ending a transit (passing in front ) of Jupiter.
Bob Moler's Ephemeris Blog 