Archive
06/25/2015 – Ephemeris – Lunar seas and highlands tell the story of the Moon’s history
Ephemeris for Thursday, June 25th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, 1 day past first quarter, will set at 2:26 tomorrow morning and tomorrow the Sun will rise at 5:58.
Tuesday I talked about the brightness variation on the Moon, the bright and ancient highlands and the darker areas called seas, but a large asteroid impact areas that welled up magma from the moon’s interior erasing prior craters. The dark seas were created after most cratering had ended, or they’d be heavily cratered too. They seem to have occurred about 4 billion years ago, about 500 million years after the Moon formed. This appeared to be a period when the giant planets came closer to the Sun than they are now, before retreating again. This period is called the late heavy bombardment. Not all astronomers give it credence, but it bears out what we see in planetary systems around other stars.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon tonight with pointers to seas near the crater Copernicus and the highlands near the crater Tycho. 10:30 p.m. June 25, 2015. Created using Virtual Moon Atlas.
The Lunar seas near the crater Copernicus showing the smooth surface with relatively few craters. Credit: Virtual Moon Atlas with the texture from NASA’s Lunar Reconnaissance Orbiter. The lunar phase was omitted.
The Lunar highlands near the crater Tycho showing a surface saturated with craters. Credit: Virtual Moon Atlas with the texture from NASA’s Lunar Reconnaissance Orbiter. The lunar phase was omitted. Both images are shown to the same scale.
06/24/2015 – Ephemeris – Jupiter and Venus inch closer while Saturn keeps its distance
Ephemeris for Wednesday, June 24th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, at first quarter today, will set at 1:58 tomorrow morning and tomorrow the Sun will rise at 5:58.
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 around midnight. Venus’ will slide down to the Sun faster and faster in the coming weeks. It will take a bit less than 2 months. Jupiter will appear western sky to the left of and slightly above Venus at about 10 p.m. It will set at 12:09 a.m. It seems to approach Venus, and now appears about 3 and a half degrees away. That’s about three finger widths held at arm’s length. They will cross paths in 6 days, on the 30th. Saturn is in the southeast in evening twilight. It will pass due south at 11:22 p.m. and will set at 4:10 a.m. Even small telescopes can see Saturn’s rings.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter and Venus converge in the west while the Moon and Saturn look on. 10:30 p.m., June 24, 2015. Created using Stellarium. Click to enlarge.
Closeup of the Moon at 10:30 p.m. June 24, 2015. Created using Stellarium.
The evening planets and the Moon using the same magnification at 10:30 p.m., June 24, 2015. Created using Cartes du Ciel (Sky Charts). Click on image to enlarge.
Note that over the last few Wednesdays that I’ve portrayed the planets at the same scale that Venus has been getting larger with respect to Jupiter as it approaches the Earth and Jupiter moves away.
Jupiter-Venus approach animation June 11 to July 1, 2015 at 10:30 p.m. Created using Stellarium and GIMP. Click on image to enlarge.
06/23/2015 – Ephemeris – What can you tell about the appearance of the Moon to the naked eye?
Ephemeris for Tuesday, June 23rd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, 1 day before first quarter, will set at 1:31 tomorrow morning and tomorrow the Sun will rise at 5:57.
The Moon is at nearly half phase or first quarter. The unaided eye can see that the Moon has darker and lighter areas. The Greeks, who thought the objects in the heavens were perfect thought that the Moon was a silvery sphere. They never quite figured out why the moon had this mottled appearance. So why are the bright parts different from the darker parts? The bright parts are called the highlands and are the oldest part of the Moon’s surface. It’s saturated with craters from impacts since the Moon formed. The dark areas are roughly circular, and are really vast craters that penetrated through the Moon’s crust to bring up molten lava that repaved the surface of the Moon some 500 million years after it formed.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon tonight (June 23, 2015). Look at the difference in the surface albedo (reflectance) between the light and dark areas and wonder about their origins. Created using Virtual Moon Atlas.
06/22/2015 – Ephemeris – The summer full moon and the winter Sun trade places
Ephemeris for Monday, June 22nd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, 2 days before first quarter, will set at 1:04 tomorrow morning. Tomorrow the Sun will rise at 5:57.
Summer’s here, and it’s a few days before the latest sunset and latest end of twilight. It might be instructive to check out the height of the moon over the next two weeks or so. The moon is heading south in front of the Sun. The Sun besides its apparent westward motion during the day caused by the Earth’s rotation also moves about twice its diameter each day eastward against the stars caused by the earth’s motion in its orbit of the Sun. Around July 1st, the moon will be about where the Sun will be next winter solstice, 4 days before Christmas. Actually it will be about 8 moon widths above where the Sun will be because its orbit is tilted a bit to the Earth’s. But it will serve as an illustration of the seasonal difference.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The full moon nearest the summer solstice. The full moon appears near where the sun would appear low in the south at the winter solstice. The bottom red line is the ecliptic, the path of the Sun. Created using Stellarium.
The full moon nearest the winter solstice. The full moon appears near where the sun would appear high in the south at the summer solstice. The top red line is the ecliptic, the path of the Sun. Created using Stellarium.
The Moon’s orbit has a slight tilt of a bit more than 5 degrees from the ecliptic, or plane of the Earth’s orbit of the sun. The crossing point is called a node. In the bottom image the node near the western horizon is called the descending node due to the fact that the Moon is heading south of the ecliptic. When the Sun and Moon are near the same node the Moon will be new and we have a chance for a solar eclipse. When at opposite nodes, a lunar eclipse. The nodes slowly slide westward slowly one revolution in about 18.6 years, which causes eclipse seasons, about 6 months apart to occur a bit earlier each year.
05/20/2015 – Ephemeris – Evening bright planet lineup
Ephemeris for Wednesday, May 20th. Today the Sun will be up for 14 hours and 59 minutes, setting at 9:09. The Moon, 2 days past new, will set at 11:35 this evening, and tomorrow the Sun will rise at 6:08.
Lets take a look at the bright planets for this week. Mercury is now too close to the Sun to really be spotted in the evening twilight. It’s at a 13 degree angle from the sun and will set at 10:47. Mercury is getting dimmer as its phase becomes a decreasingly thin crescent. Our brilliant evening star Venus is in the west by 9:30 p.m. It will set at 12:47 a.m. Jupiter will appear high in the west-southwestern sky before 10 p.m. It will set at 2:14 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. Saturn will rise in the east-southeast at 9:03 p.m. It will be low in the southwest as morning twilight brightens. It’s rings and the moon Titan can be seen in small telescopes.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The evening planets from west to east at 10:30 p.m. on May 20, 2015. Created using Stellarium.
Telescopic views of the evening planets showing their relative sizes at 10:30 p.m. on May 20, 2015. Created using Cartes du Ceil (Sky Charts).
Note: The unnamed satellite of Jupiter is Callisto, which ended its transit of Jupiter at 10:27 p.m.
Binocular-like view of the Moon at 10:30 p.m. on May 20,2015. Created using Cartes du Ceil (Sky Charts).
05/19/2015 – Ephemeris – The crescent Moon reappears in the west
Ephemeris for Tuesday, May 19th. Today the Sun will be up for 14 hours and 57 minutes, setting at 9:08. The Moon, 1 day past new, will set at 10:42 this evening, and tomorrow the Sun will rise at 6:09.
The Moon is again making its appearance in the evening sky as a thin crescent. The crescent appearance is because the moon is mostly between the Earth and the Sun. , so we are looking at just a sliver of it is sunlit, and most is unlit by the sun. But the Moon has the Earth in its sky, which is quite bright, and when the moon’s phase is thin, the Earth illuminates its night side with Earth light. We call it Earthshine, when the whole Moon appears faintly inside the crescent. It’s also known more poetically as the “Old moon in the new moon’s arms.” The planets Venus and Mercury also exhibit crescent phases because they can be positioned between the Earth and the Sun, as Mercury is now and Venus will be next month.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Close grouping of, from right to left, Venus, Jupiter, Venus and the overexposed crescent Moon showing Earthshine on June 15, 1991. Credit: Bob Moler.
04/27/2015 – Ephemeris – Two large craters on the Moon for binoculars or a small telescope
Ephemeris for Monday, April 27th. Today the Sun will be up for 14 hours and 3 minutes, setting at 8:42. The Moon, 2 days past first quarter, will set at 4:04 tomorrow morning. Tomorrow the Sun will rise at 6:37.
After taking a look, last week, at some early results from the two spacecraft approaching dwarf planets now, Dawn at Ceres and New Horizons nearing Pluto, let’s get back to our sky and our Moon. Time to get out that telescope or powerful binoculars. The terminator which now is the sunrise line will be cutting through the middle of the crater Copernicus at 10 in the evening. Copernicus, near the Moon’s equator hit a flat lunar sea, so it’s quite conspicuous. Another crater near the Moon’s southern pole is conspicuous because it’s so big. It’s Clavius, with an arc of diminishing sized craters within. It will be completely in sunlight being uncovered slowly now by the terminator.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon at 10 p.m. April 27, 2015 EDT (2:00 UT, April 28). Created using Virtual Moon Atlas.
04/22/2015 – Ephemeris – All the bright planets are back now
Ephemeris for Earth Day, Wednesday, April 22nd. Today the Sun will be up for 13 hours and 49 minutes, setting at 8:36. The Moon, 3 days before first quarter, will set at 12:55 tomorrow morning. Tomorrow the Sun will rise at 6:45.
Lets take a look at the bright planets for this week. Mars and Mercury are in conjunction, that is close to each other low in the west just after sunset. Mars appears a bit lower and left of the brighter Mercury. Mars will set tonight at 9:47 with Mercury 5 minutes later. Our brilliant evening star Venus is high in the west by 9 p.m. It will set at 12:15 a.m. Jupiter will appear high in the southwestern sky in the evening. It will set at 3:58 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. Saturn will rise in the east-southeast at 11:03 p.m. It will be low in the south at 5 to 6 a.m.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
View to the west with Mars, Mercury, Venus and the Moon at 9:15 p.m. April 22, 2015. Created using Stellarium.
Jupiter, the Moon and the setting winter constellations at 10 p.m. April 22, 2015. Created using Stellarium.
The visibility of the Moon at 10 p.m. on April 22, 2015. Created using Cartes du Ciel (Sky Charts).
Jupiter and its moons at 10 p.m. Europa will be transiting the face of Jupiter. It’s shadow will start to cross the face of Jupiter at 11:04 p.m.. The transit will end at 11:27 p.m. and the shadow will leave the face of Jupiter at 1:58 a.m. Created using Cartes du Ciel (Sky Charts).
Saturn rising. Shown at midnight, April 22-23 2015. Created using Stellarium.
Saturn and the summer constellations at 5:45 a.m. April 23, 2015. Created using Stellarium.
What Saturn and its moons might appear like in a telescope at 5:45 a.m., April 23, 2015. Small telescopes will show only the moon Titan. Created using Cartes du Ceil (Sky Charts).
04/21/2015 – Ephemeris – The Moon will pass the Hyades star cluster today to pass near Venus tonight
Apr 21. This is Bob Moler with Ephemeris for Tuesday, April 21st. Today the Sun will be up for 13 hours and 46 minutes, setting at 8:35. The Moon, 3 days past new, will set at midnight. Tomorrow the Sun will rise at 6:47.
The moon, which was new last Saturday passed the face of the constellation Taurus the bull earlier today. The face of Taurus is a letter V shape of stars which is the star cluster called the Hyades. There’s a bright orange star that appears at the left tip of the V called Aldebaran, which actually doesn’t belong to the cluster. At 9:30 the crescent Moon will have also just passed the brilliant planet Venus. By then they will be nearly 8 degrees apart, which is a bit less than the width of a fist held at arm’s length. The Moon, Venus and all the planets move very close along the path of the Sun in the sky, called the ecliptic. Even so the Moon is now about 5 degrees south of the ecliptic and Venus about 2 degrees north of it.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon with Venus and the Hyades at 9:30 p.m. April 21, 2015. Note the Pleiades on the right. Created using Stellarium.
04/07/2015 – Ephemeris – The Moon will pass Saturn tomorrow morning
Ephemeris for Tuesday, April 7th. The Sun will rise at 7:13. It’ll be up for 13 hours and 4 minutes, setting at 8:17. The Moon, 3 days past full, will rise at 11:36 this evening.
The planet Saturn is now rising shortly after midnight. However it is still best seen in the early morning. The Moon will be near Saturn when it rises and will get closer as the morning progresses. By 6 a.m. the Moon will be about four of its widths above and right of Saturn. The Moon will get its closest about 10 a.m., but by then it will be daylight and both will have set. Every week Saturn will rise, and set about a half hour earlier. That’s about an hour every two weeks, and two hours a month. This works for the stars and is pretty close for slow-moving planets like Jupiter and Saturn. So next month at this time Saturn will rise about 10 p.m., and in another month 9 p.m. By then it will be in the sky at sunset, and visible all night.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Saturn and the Moon shortly after rising. 12:44 a.m., April 8, 2015. Created using Stellarium.
Saturn and the Moon shortly after twilight starts. 5:30 a.m., April 8, 2015. Created using Stellarium.
The Moon as it might appear in binoculars at 5:30 a.m. April 8, 2015. Created using Stellarium.
Some Rules of Thumb about the rotation of the earth and its revolution around the Sun.
These are approximate:
Stars rise or set 4 minutes earlier each night.
That’s about a half hour every week, and
It’s about 2 hours every month.
2 hours times 12 months = 24h hours, one rotation of the Earth
As far as viewing the stars and Constellations goes, that’s why we see the constellations in the same positions every year at the same time.
Bob Moler's Ephemeris Blog 