Archive
03/21/2019 – Ephemeris – Are day and night really equal at the equinoxes?
Ephemeris for Thursday, March 21st. Today the Sun will be up for 12 hours and 11 minutes, setting at 7:56, and it will rise tomorrow at 7:42. The Moon, 1 day past full, will rise at 8:52 this evening.
What we had yesterday was the vernal equinox, the start of spring. The word equinox means “equal night”. Yesterday’s daylight hours were 12 hours and 8 minutes. What’s with the 8 minutes? The rising or setting Sun is a mirage. The Earth’s atmosphere acts like a lens and makes the Sun appear higher in the sky than when it is when near the horizon. When the bottom edge of the Sun touches the horizon the Sun is actually still completely below the horizon geometrically. If the Earth had no atmosphere sunrises would occur 4 minutes later, and sunsets would occur 4 minutes earlier around here. That would completely correct the 12 hour 8 minutes daylight time of yesterday to 12 hours even.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
How the atmosphere bends the light of the Sun or Moon rising or setting to appear higher than it actually is. Credit Francisco Javier Blanco González, 2017.
I took a look at the related atmospheric refraction effect last month: https://bobmoler.wordpress.com/2019/02/19/02-19-2019-ephemeris-the-moon-aint-just-super-near-the-horizon/.
03/20/2019 – Ephemeris – The first look, of spring, at the bright planets
Ephemeris for Wednesday, March 20th. Today the Sun will be up for 12 hours and 8 minutes, setting at 7:55, and it will rise tomorrow at 7:44. The Moon, at full today, will rise at 7:35 this evening.
Let’s look at the planets for this week. Looking down we see the Earth which will reach a point in its orbit at 5:58 p.m. (21:58 UT) where spring will start. Mars will be in the west-southwestern sky this evening. It will set at 12:37 a.m. Mars is fading as the Earth, in its inner and faster orbit is leaving Mars behind. In the morning sky we have Jupiter which will rise tomorrow at 2:55 a.m. in the east-southeast It is second to Venus in brightness. Saturn will be next to rise at 4:40 a.m., also in the east-southeast. Venus will rise at 6:26 a.m. also in the east-southeast By 7 in the morning they will be strung out from the southeast to the south. They will be a beautiful sight as morning twilight advances.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars and the Moon and the bright stars on the first day of spring at 9 p.m. March 20, 2019. Click on the image to enlarge. Created using Stellarium.
The full moon, and super moon at that, at 9 p.m. March 20, 2019. Created using Stellarium.
Morning planets and the constellations at 7 a.m. tomorrow March 21, 2019. Created using Stellarium.
Jupiter, Saturn and Venus with the same magnification at 7 a.m. tomorrow morning March 21, 2019. Created using Cartes du Ciel (Sky Charts).
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on March 20, 2019. The night ends on the left with sunrise on the 21st. Note the motion of the Moon from sunrise and sunset. Click on the image to enlarge. Created using my LookingUp program.
03/19/2019 – Ephemeris – Spring and a super-moon happen tomorrow
Ephemeris for Tuesday, March 19th. Today the Sun will be up for 12 hours and 5 minutes, setting at 7:53, and it will rise tomorrow at 7:46. The Moon, 1 day before full, will set at 7:55 tomorrow morning.
Today and tomorrow are busy days, astronomically speaking, for the Earth, Sun and Moon. This afternoon at 3:47 the Moon will reach the perigee point in its orbit of the Earth, its closest point of 223,200 miles (359,400 km) center to center. With the full moon just 30 hours later this will make the Moon a super-moon, the third in a row. The Moon will be full enough to call tonight’s moon a super-moon too when it rises around 6:16 p.m. The next event will be the coming of spring, when the Sun appears to cross the celestial equator heading northward. For a point in the Pacific Ocean, on the equator the Sun will be directly overhead at 5:58 p.m. our time or 21 hours, 58 minutes Universal Time or Greenwich Mean Time.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mini Moon and Super Moon for 2017. Trouble is the Moon appears alone with nothing to compare it to when it is seen in the sky. Created using Cartes du Ciel (Sky Charts).
The Sun’s path through the sky on the equinox day from Traverse City, MI. Created using my LookingUp program. (This is from a couple of years ago. The actual length of daylight depends on when during the day the moment of the equinox occurs. I’ll have more on that Thursday.)
03/18/2019 – Ephemeris – Spring, the full moon and Easter
Ephemeris for Monday, March 18th. Today the Sun will be up for 12 hours and 2 minutes, setting at 7:52, and it will rise tomorrow at 7:48. The Moon, 2 days before full, will set at 7:21 tomorrow morning.
Spring is two days away. In checking my astronomical calendars I noticed an odd thing related to the date of Easter for western churches. If I said that the date of Easter was the first Sunday after the first full Moon after the vernal equinox. I’d be wrong. Even if I replaced vernal equinox with first day of spring, I would still be wrong by ecclesiastical standards. The ecclesiastical vernal equinox is March 21st, no matter what. Plus the full moon date is a tabulated value and not necessarily the astronomical full moon date. This year the astronomical first full moon of spring falls less than 4 hours after the astronomical vernal equinox on March 20th. Therefore Easter will be late this year on April 21st, 4 days earlier than its latest possible date.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
03/15/2019 – Ephemeris – The era of US crewed space launches begins
Ephemeris for Ides of March, Friday, March 15th. Today the Sun will be up for 11 hours and 53 minutes, setting at 7:48, and it will rise tomorrow at 7:53. The Moon, 1 day past first quarter, will set at 5:07 tomorrow morning.
Two weeks ago, the United States began to get back in the human space launch business with the launch of a test Crew Dragon space capsule on a Falcon 9 rocket, all made by SpaceX. The 6 day mission to dock with the International Space Station and then return to the Earth was an apparent success as everything appeared to go smoothly. After a successful in-flight abort test with the same capsule in a few months, another test with a crew will be flown. Boeing’s Starliner capsule is not far behind with a possible uncrewed launch in April. Both companies have abort tests to get behind them before crews can be launched. SpaceX is expected to launch a crew as early as June.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
NASA
SpaceX Falcon 9 Crew Dragon Demo-1 liftoff. Credit NASA.
NASA-SpaceX Demo-1 Screen Cap of docking at the ISS. Credit NASA.
Inside the SpaceX Crew Dragon with Canadian astronaut David Saint-Jacques. Credit NASA/SpaceX.
NASA-SpaceX Demo-1 Crew Dragon Capsule splashdown in the Atlantic. Credit NASA/SpaceX.
03/14/2019 – Ephemeris – Happy Pi Day
Ephemeris for Pi Day, Thursday, March 14th. Today the Sun will be up for 11 hours and 49 minutes, setting at 7:47, and it will rise tomorrow at 7:55. The Moon, at first quarter today, will set at 4:09 tomorrow morning.
Pi day: the first three digits of the mathematical constant π is 3.14 the ratio of a circle’s circumference to its diameter, so March 14th is Pi day. Why do we use the Greek letter pi? Pi is the first letter of the Greek word perimetros which means circumference. The first Pi Day was celebrated in 1988, organized by Larry Shaw at San Francisco’s Exploratorium. There are other lass known pi related days on the calendar. The fraction used in pi approximations is 22/7ths. So July 22nd is Pi Approximation Day. In many formulae π is multiplied by two, or 2π. 2π to two decimal places is 6.28, so it’s Two Pi Day or Tau (τ) Day, June 28th. So whether you like apple, cherry, or pumpkin, have a happy Pi day. https://www.piday.org/pi-facts/
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Credit http://www.piday.org.
Check out https://www.piday.org/pi-facts/ for more information on pi.
03/13/2019 – Ephemeris – Let’s find the bright planets for this week
Ephemeris for Wednesday, March 13th. Today the Sun will be up for 11 hours and 46 minutes, setting at 7:46, and it will rise tomorrow at 7:57. The Moon, 1 day before first quarter, will set at 3:06 tomorrow morning.
Let’s look at the planets for this week. We are back to one evening planet visible now. Mars will be in the west-southwestern sky this evening and will set at 12:39 a.m. Mars is fading as the Earth, in its inner and faster orbit is leaving Mars behind at 175 million miles (282 million km) away. In the morning sky we have Jupiter which will rise tomorrow at 3:20 a.m. in the east-southeast It is second to Venus in brightness. Saturn will be next to rise at 5:06 a.m., also in the east-southeast It will be to the upper right of Venus which will rise at 6:30 a.m. By 7 in the morning they will be strung out from the southeast to the south. They will be a beautiful sight as morning twilight advances.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars and the Moon with the brighter stars at 9 p.m. March 13, 2019. Created using Stellarium.
The Moon as it might appear in binoculars or a small telescope tonight at 9 p.m. March 13, 2019. Created using Stellarium.
Morning planets and the constellations at 7 a.m. Tomorrow March 14, 2019. Click on the image to enlarge. Created using Stellarium.
Jupiter, Saturn and Venus with the same magnification at 7 a.m. tomorrow morning March 14, 2019. Created using Cartes du Ciel (Sky Charts).
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on March 13, 2019. The night ends on the left with sunrise on the 14th. Click on the image to enlarge. Created using my LookingUp program.
03/12/2019 – Ephemeris – Does the Moon rotate?
Ephemeris for Tuesday, March 12th. Today the Sun will be up for 11 hours and 43 minutes, setting at 7:44, and it will rise tomorrow at 7:59. The Moon, 2 days before first quarter, will set at 2:00 tomorrow morning.
Since we see only one face of the Moon throughout the month does that mean that the Moon doesn’t rotate? It doesn’t appear to rotate with respect to the Earth, but the Moon rotates through all the stars and constellations of the zodiac in a 27.32 days. That’s called a sidereal month. The lunar month we’re more familiar with is the synodic month, or lunation, that lasts 29.53 days which is the interval between new moons. It is the basis of the Jewish and Islamic calendars. The reason for the locking of the Moon’s rotation and revolution of the Earth, also called synchronous rotation, is the tidal pull of each on the other. The Earth has managed to slow the Moon’s rotation to match its revolution. The Moon is trying to do the same to the Earth with much less success, though every year or two a second is added to the time stream, UTC1 or Greenwich Mean Time, due to the slowing of the Earth’s rotation.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Animation of the Moon orbiting the Earth showing the Moon’s rotation. Credit: NASA’s Scientific Visualization Studio/Ernie Wright, modified and converted to GIF by Bob Moler.
NASA’s Scientific Visualization Studio web page where I got the original for the above video.
03/11/2019 – Ephemeris – The Moon: Dark side, far side, which is it?
Ephemeris for Monday, March 11th. Today the Sun will be up for 11 hours and 40 minutes, setting at 7:43, and it will rise tomorrow at 8:01. The Moon, 3 days before first quarter, will set at 12:54 tomorrow morning.
Tonight the Moon is at its crescent phase, meaning it is slightly closer to the Sun than the Earth is. Most of the Moon we see is in night. Some earth shine may be seen on its night side due to the big nearly full Earth shining on it. I get ticked sometimes when someone who knows better, especially in the media, mentions the dark side of the Moon when they should use the term far side, the part of the Moon that permanently faces away from the Earth. When the Chinese Chang’e 4 spacecraft landed on the far side of the Moon recently many headlines proclaimed that it landed on the dark side of the Moon. The Moon has a night side, as does the Earth, but that changes as the Moon rotates in the sunlight. And the Moon does rotate. It happens to be in sync with its revolution about the Earth.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The crescent Moon tonight at 9 p.m. EDT, March 11, 2019. Created using Stellarium.
Demonstration of the Moon’s crescent phase with the Styrofoam moon ball we use for Project Astro held up to a light off frame to the right. The night side of the ball is illuminated a bit by the translucency of the ball, and the reflection off my hand. Note the roughness of the ball is visible only at the terminator.
The Earth and Moon if seen as a crescent, near side, far side, sunlit side and earth shine. Credit: me.
03/08/2019 – Ephemeris – International Women’s Day
Ephemeris for International Women’s Day, Friday, March 8th. Today the Sun will be up for 11 hours and 31 minutes, setting at 6:39, and it will rise tomorrow at 7:06. The Moon, 2 days past new, will set at 8:43 this evening.
On this International Women’s Day let’s take a look in my favorite fields of astronomy and space. There’s Hypatia of Alexandria who was murdered by an ignorant mob in 415 AD, Caroline Herschel sister to William Herschel and among other things discovered 8 comets, Maria Mitchell, whose comet discovery rocketed her to fame in the United States in the 1800s, Annie Jump Cannon, who classified stars, Henrietta Leavitt who found how to find distances to far away galaxies, and Vera Rubin who helped discover dark matter. In space there’s Sally Ride, Mae Jamison, and Peggy Whitson, who holds the American space flight time, and EVA time records regardless of gender. And that’s just scratching the surface.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Ten female astronomers everyone should know: https://www.mnn.com/leaderboard/stories/10-female-astronomers-everyone-should-know.
My favorite astronomer on Twitter is astrophysicist Dr. Katherine J Mack @AstroKatie.
