04/23/2019 – Ephemeris – The story of Coma Berenices

Ephemeris for Tuesday, April 23rd. Today the Sun will be up for 13 hours and 52 minutes, setting at 8:37, and it will rise tomorrow at 6:43. The Moon, 3 days before last quarter, will rise at 1:24 tomorrow morning.

High in the southeast at 10 p.m. is a tiny and faint constellation of Coma Berenices, or Berenice’s hair. In it are lots of faint stars arrayed to look like several strands of hair. The whole group will fit in the field of a pair of binoculars, which will also show many more stars. The hank of hair was supposed to belong to Berenice, a real Queen of Egypt, of the 3rd century BCE. who cut off her golden tresses and offered them to the gods for the safe return of her husband from war. Her husband did return safe, and at that same time her hair disappeared from the temple. The oracle of the temple pointed to this constellation showing that her sacrifice was enshrined in the stars.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Coma Berenices and neighboring constellations at 10 p.m. on April 16, 2015. Note that only the upper right star of the upside down L shape actually belongs to the cluster. Created using Stellarium.

 

04/22/2019 – Ephemeris – Earth Day

Ephemeris for Earth Day, Monday, April 22nd. Today the Sun will be up for 13 hours and 49 minutes, setting at 8:36, and it will rise tomorrow at 6:45. The Moon, 3 days past full, will rise at 12:24 tomorrow morning.

A good slogan for this Earth Day or any day is “Support your local planet.” As an amateur astronomer I look around the solar system at all the habitable planets. The Earth is it. Mars may be terraformed at great expense, that is made more earth-like. There may be life in the oceans of Jupiter’s moon Europa, or Saturn’s Enceladus, but they are not habitable for us. Terraforming (stopping and reversing climate change)  the Earth would be the easiest and much more practical. One look at our nearest neighbor Venus will show us our fate, hopefully in billions of years from now, a hell hole of heat and a crushing atmosphere. Our job is push-off that day as far as we can, and keep the Earth a blue-green oasis in the solar system.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Earth rising above the Moon’s limb from Apollo 8. Credit: NASA/Apollo 8

Mars had its day, but that ended about 3 billion years ago. Being half the size of the Earth, Mars cooled down, lost its magnetic field, so the solar wind stripped away most of its atmosphere and water. Credit NASA.

Europa, one of the four Galilean moons of Jupiter and easily seen in small telescopes, is slightly smaller than our Moon. Under that thick icy shell lurks an ocean with more water than all the Earth’s oceans. There’s probably volcanic vents like the black smokers in Earth’s oceans where a whole ecology of extremophiles could live like they do on Earth. Credit: NASA.

Enceladus, a small moon of Saturn spews continuous geysers of water from cracks in its south polar region indicating an ocean below its frozen icy exterior. Sampling the plumes with the right instruments may detect life on this small world without the need for drilling. Credit: NASA.

Is this our future? Venus had the misfortune of ending up too close to the Sun. It has a hellish landscape of nearly 900 degrees F, and 90 times the Earth’s atmospheric pressure. Its clouds consist of sulfuric acid. Talk about a runaway greenhouse effect and acid rain… Credit: NASA.

04/19/2019 – Ephemeris – Why Sunday is Easter

Ephemeris for Good Friday, Friday, April 19th. Today the Sun will be up for 13 hours and 40 minutes, setting at 8:32, and it will rise tomorrow at 6:50. The Moon, at full today, will rise at 8:56 this evening.

Easter will be celebrated by western Christian churches this Sunday. Easter is a movable feast in that it falls on a different date each year following the first full moon of spring. It’s an attempt to follow the Jewish Passover, which starts on the 15th of the month of Nisan. Being a lunar calendar the 15th the generally the night of the full moon. And since the Last Supper was a Seder, the Christian church wanted to follow Passover as closely as possible using the Roman solar based (Julian*) calendar where the year was 365.25 days long. Passover starts at sunset tonight. The western churches eventually adopted the Gregorian calendar to keep in sync with the seasons. The Eastern churches kept the old Julian Calendar and other considerations to calculate the date of Easter, which arrives a week later.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

* The Julian calendar is named after Julius Caesar who proposed it in 46 BC.  It took effect on January 1, 45 BC.  By the Julian calendar today is April 6.

04/18/2019 – Ephemeris – Tides

Ephemeris for Thursday, April 18th. Today the Sun will be up for 13 hours and 37 minutes, setting at 8:31, and it will rise tomorrow at 6:52. The Moon, 1 day before full, will set at 7:22 tomorrow morning.

The Moon and the Earth gravitationally attract each other. And the Moon raises tides in the Earth itself and its oceans. The Earth’s tides on the mass of the Moon has slowed its rotation so it continually shows the Earth the same face. The Moon, only one 81st the mass of the Earth hasn’t been as successful at greatly slowing the Earth’s rotation. It does cause the world’s timekeepers to add one second occasionally to the time stream to offset our atomic clocks to the Earth’s rotation. The most noticeable effects of the Moon’s tidal force is the tides in the Earth’s oceans. The highest tides are when the Sun and Moon are in line with the Earth at new and full moon. Small bodies of water like the Great Lakes don’t have luni-solar tides greater than 2 inches (5 cm).  The Great Lakes do have tide like effects called seiches, like water sloshing in a bath tub, caused by wind or barometric pressure, and can be several feet high.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

This link from NOAA explains tides better than I can:  https://scijinks.gov/tides/.

This link is the explanation of seiches:  https://oceanservice.noaa.gov/facts/gltides.html.

04/17/2019 – Ephemeris – Let’s look for the bright planets

Ephemeris for Wednesday, April 17th. Today the Sun will be up for 13 hours and 34 minutes, setting at 8:30, and it will rise tomorrow at 6:53. The Moon, 2 days before full, will set at 6:53 tomorrow morning.

Let’s look at the planets for this week. Mars will be in the western sky this evening, above the V-shaped stars of the face of Taurus the bull. It will set at 12:23 a.m. In the morning sky we have Jupiter, in Ophiuchus, which will rise tomorrow at 1:07 a.m. in the east-southeast. Saturn will be next to rise at 2:54 a.m., also in the east-southeast. It is in Sagittarius. Venus will rise at 5:56 a.m. again in the east-southeast. By 6:30 in the morning they will be strung out from the south down to the eastern horizon. Venus will remain in our morning sky, though more difficult to see until August when it passes behind the Sun to enter the evening sky. Tiny Mercury may be glimpsed a bit left and just below Venus in the bright twilight.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Mars and the Moon tonight at 9:30 p.m. April 17, 2019. Click on the image to enlarge. Created using Stellarium.

The waxing gibbous nearly full Moon at 9:30 p.m. April 17, 2019. Created using Stellarium.

Morning planets and Moon at 6:30 a.m. April 18, 2019. Click on the image to enlarge. Created using Stellarium.

Jupiter and Saturn with the same magnification at 6:30 a.m. tomorrow morning April 18, 2019. Click on the image to enlarge. Created using Cartes du Ciel (Sky Charts).

Jupiter’s moon Io events earlier in the morning

Moon	Event	Date	U.T.	EDT
Io	Shadow start	18 Apr 2019	05:40	1:40 AM
Io	Transit start	18 Apr 2019	06:44	2:44 AM
Io	Shadow end	18 Apr 2019	07:51	3:51 AM
Io	Transit end	18 Apr 2019	08:56	4:56 AM

Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on April 17, 2019. The night ends on the left with sunrise on the 18th. Click on the image to enlarge. Created using my LookingUp program.

04/16/2019 – Ephemeris – Last week was quite a week in astronomy and space

Ephemeris for Tuesday, April 16th. Today the Sun will be up for 13 hours and 31 minutes, setting at 8:28, and it will rise tomorrow at 6:55. The Moon, 3 days before full, will set at 6:23 tomorrow morning.

Last week was quite a week in astronomy and space. Wednesday was the announcement that the Event Horizon Telescope team had actually imaged the supermassive black hole in the galaxy M87, using eight sub-millimeter radio telescopes observing from five continents simultaneously. We’ll have to wait a bit to get an image of the Milky Way’s supermassive black hole. Later that Day SpaceX launched their Falcon Heavy rocket to loft an Arab communications satellite into orbit. The three boosters landed safely. Thursday the Israeli privately financed Beresheet lunar lander almost landed safely on the Moon. Unfortunately its rocket engines failed during its landing attempt. They will build another and try again.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The first image of the black hole in M87. Credit Event Horizon Telescope.

A 5,000 light year long jet from the black hole M87* that’s actually aimed mostly toward us. So the accretion disk in the black hole image is like a halo around the event horizon seen from near the pole of rotation. Credit: NASA/The Hubble Heritage Team (STScI/AURA).

Falcon Heavy leaves the pad. April 10, 2019. Credit SpaceX.

A selfie image of part of the Beresheet lander moments before contact was lost from the Beresheet spacecraft during its descent to the Moon. Credit: SpaceIL/Israel Aerospace Industries.

04/15/2019 – Ephemeris – Why land at the Moon’s south pole?

Ephemeris for Tax Deadline Day Monday, April 15th. Today the Sun will be up for 13 hours and 28 minutes, setting at 8:27, and it will rise tomorrow at 6:57. The Moon, 3 days past first quarter, will set at 5:53 tomorrow morning.

The hottest piece of real estate on the Moon is the south pole. Unlike the Earth’s south pole and the rest of the Moon, except the north pole, there are mountain tops that are always in sunlight. The Moon has a very small axial tilt, only a degree an a half, compared to the Earth’s 23 and a half degrees which plunges the earth’s poles into a 6 month’s night. Another benefit of the small tilt is that the floors of craters at of near the poles never see sunlight, so are hundreds of degrees below zero and can be cold traps for water vapor from passing or colliding comets. Yes, thar’s water in them thar craters. It’s more valuable than gold, providing oxygen to breathe and hydrogen and oxygen for rocket fuel.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The south pole of the Moon where the presence of water ice is detected by the absorption of neutrons by the hydrogen atoms in the ice. Credit NASA/GSFC/SVS/Roscosmos.