Archive
03/24/2015 – Ephemeris – The Moon will be passing in front of the Hyades tonight
Ephemeris for Tuesday, March 24th. The Sun will rise at 7:38. It’ll be up for 12 hours and 21 minutes, setting at 8:00. The Moon, 3 days before first quarter, will set at 1:16 tomorrow morning.
Tonight he Moon will be crossing in front of the Hyades star cluster, otherwise known as the face of the constellation Taurus the bull. The Moon will make it about half way across by the time it sets. The Moon is 2160 miles in diameter and moves about the same distance in an hour as it orbits the Earth. The International Space Station and other satellites in low Earth orbit have to travel 17,500 miles an hour to stay in orbit. But since the Earth’s gravity, or the gravitational force of any body diminishes with the square of the distance. Double the distance and the gravitational force diminishes by a factor of four. This inverse square law as it is known also works with the diminution of light with distance from its source.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon is travelling in front of the Hyades at 10 p.m. March 24, 2015. Created using Stellarium.
03/23/2015 – Ephemeris – Olbers’ Paradox or why it’s dark at night
Ephemeris for Monday, March 23rd. The Sun will rise at 7:40. It’ll be up for 12 hours and 17 minutes, setting at 7:58. The Moon, 3 days past new, will set at 12:12 tomorrow morning.
Why is it dark at night? It seems like a dumb question but it isn’t, or wasn’t when the question was first asked by Henrich Wilhelm Olbers who lived from 1768 to 1840. The dark sky problem is called Olbers’ Paradox. If the universe was uniformly filled with stars and infinite in size all the stars would overlap giving a bright sky, day or night. The fact that it doesn’t tells us something about the universe. Stars are not uniformly scattered throughout the universe, they are bound up into galaxies, also the more distant stars in their galaxies are red shifted, losing energy. Also if the universe is really infinite, parts of it are receding faster than the speed of light, so we can’t see them. Receding faster than light, how can that be? Though matter cannot move faster than light, space can expand faster than light.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
“Olbers’ Paradox – All Points.” Credit: Kmarinas86, Licensed under CC BY-SA 3.0 via Wikimedia Commons
03/20/2015 – Ephemeris – Spring will spring forth at 6:44 p.m. EDT
Ephemeris for Friday, March 20th. The Sun will rise at 7:46. It’ll be up for 12 hours and 8 minutes, setting at 7:55. The Moon is new today, and won’t be visible.
The Arctic solar eclipse has just ended. But there is one more event of note today. At 6:44 p.m. The Sun will cross the celestial equator heading northward, the projection of the Earth’s equator on the sky. In doing that the season of spring will return to the northern hemisphere. The Sun is already staying up for just over half the day. That will increase to fifteen and a half hours by the summer solstice three months from now. Not only will the Sun will be out longer, but it will rise higher in the sky, rising from 45 degrees altitude in the south at local noon to 69 degrees on June 21st. If the sun stayed at this location it would get very uncomfortable with the heat. As it is as the Sun is climbing down it will still get warmer. Peak summer heat occurs about a month after the solstice.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
These are whole sky diagrams with the edge at the horizon. The Sun’s motion is from left to right. The Sun is plotted every 15 minutes. The Sun’s motion is constant, however the projection causes squeezing of the positions near the zenith (center of the diagram) and stretching near the horizon.
The sun’s daily path through the sky from horizon to horizon on an equinox the first day of spring or autumn. Credit My LookingUp program.
The sun’s daily path through the sky from horizon to horizon on the first day of summer, the summer solstice. Credit My LookingUp program.
03/19/2015 – Ephemeris – A remarkable solar eclipse tomorrow, however we, in the US, won’t see it.
Ephemeris for Thursday, March 19th. The Sun will rise at 7:48. It’ll be up for 12 hours and 5 minutes, setting at 7:53. The Moon, 1 day before new, will rise at 7:50 tomorrow morning.
There will be a rare solar eclipse tomorrow. The bad news is that it won’t be visible from here. Be that as it may, it is total for a circle of ocean near Greenland, and because tomorrow is also the vernal equinox the it is also sunrise at the north pole. As it happens the path of the eclipses totality tracks to the north pole, so the eclipse, partial and total will be visible from there. I’m not sure how long it’s been since an eclipse totality was visible at the pole on an equinox. The next solar eclipse visible from the United States will be on August 21, 2017. This is an eclipse, whose path of totality crosses the continental United States. In about 2 weeks we’ll have a lunar eclipse whose first stages can be seen from northern Michigan in morning twilight.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Pertinent section of the March 20, 2015 total solar Eclipse map. Click on image above for the entire image. Credit: Fred Espenak, NASA’s GSFC.
03/18/2015 Ephemeris – It’s Wednesday, so where are all the bright planets?
Ephemeris for Wednesday, March 18th. The Sun will rise at 7:50. It’ll be up for 12 hours and 2 minutes, setting at 7:52. The Moon, 2 days before new, will rise at 7:14 tomorrow morning.
Lets take a look at the bright planets for this week. Brilliant Venus is in the west by 8:30 p.m. It will set at 10:49 p.m. Mars appears below and right of it. The Red Planet will set tonight at 9:47. Jupiter will appear In the southeastern sky in the evening. It will set at 6:41 a.m. It’s near the sickle-shaped head of Leo the lion, and it’s the brightest star-like object in the sky after Venus sets. In telescopes tonight the moon Io will duck behind Jupiter at 11:17, but will pop into sunlight a bit away from the planet on the other side at 2:28 a.m. because it also will be hidden in Jupiter’s shadow. Early risers will be able to spot Saturn which will rise in the east-southeast at 1:27 a.m. It will be low in the south at 6 to 7 a.m.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter, Venus and Mars at 9 p.m. March 18, 2015. Created using Stellarium.
Saturn and the summer constellations of Scorpius and Sagittarius at 6:30 a.m. March 19, 2015. Created using Stellarium.
Planets to the same scale as viewed in a telescope of the same power. Venus and Jupiter at 8:30 p.m. on March 18, 2015. Saturn at 6:30 a.m. on March 19. 2015. Created using Cartes du Ceil (Sky Charts).
03/17/2015 – Ephemeris – Jupiter’s cloud stripes
Ephemeris for St. Patrick’s Day, Tuesday, March 17th. The Sun will rise at 7:51. It’ll be up for 11 hours and 59 minutes, setting at 7:51. The Moon, 3 days before new, will rise at 6:37 tomorrow morning.
Jupiter is the one planet that we can see detail on with telescopes in the evening sky. Venus is so bright that it is hard to even see its gibbous phase. Actually the best way to see Venus is during the day with the blue sky around it. Jupiter is a big planet, 11 times the Earth’s diameter and 1,300 times it volume. Despite this it is only 318 times the Earth’s mass, so much of its mass is the atmosphere. It’s rotation rate is just under 10 hours at its equator. This drops with latitude, so its atmosphere is twisted into alternate belts and zones. The belts are dark brown while the zones are lighter. They move around the planet at different speeds causing storms that their boundaries. The Great Red Spot is a anticyclone in the south.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Jupiter by Scott Anttila November 14, 2011. With shadow on the planet and the Great Red Spot.
03/13/2015 – Ephemeris – Leo rising
Ephemeris for Friday, March 13th. The Sun will rise at 7:59. It’ll be up for 11 hours and 46 minutes, setting at 7:46. The Moon, at last quarter today, will rise at 3:35 tomorrow morning.
The constellation Leo the lion is now rising in the east at 9 pm. It’s below and left of the Big Dipper higher up in the east-northeast. Leo is marked by two sets of easily recognizable stars. The front of him is a backward question mark of stars, also known as the Sickle that mark his head and mane, along with the front part of his body. Regulus is the star at the bottom of that backwards question mark. It’s the Little King Star. Jupiter this year is above right if it. The hind end of him is a triangle of stars ending with another bright star, but not as bright as Regulus. It’s Denebola which means Lion’s tail. It is thought when the sun was in this constellation long ago that the lions were driven by the heat to quench their thirst in the Nile river. Ancients physicians thought medicines were poison when the sun was here too.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Leo rising in the east behind Jupiter at 9 p.m. on March 13, 2015. Created using Stellarium.
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).
03/11/2015 – Ephemeris – On Wednesday we look at the bright planets
Ephemeris for Wednesday, March 11th. The Sun will rise at 8:02. It’ll be up for 11 hours and 40 minutes, setting at 7:43. The Moon, 2 days before last quarter, will rise at 1:42 tomorrow morning.
Lets take a look at the bright planets for this week. Brilliant Venus is in the west by 8:30 p.m. It will set at 10:31 p.m. Mars appears below and right of it. The Red Planet will set tonight at 9:47. Jupiter will appear In the southeastern sky in the evening. It will set at 6:41 a.m. It’s near the sickle-shaped head of Leo the lion, and it’s the brightest star-like object in the sky after Venus sets. In telescopes tonight the moon Io duck behind Jupiter at 9:29 early, but will pop into sunlight a bit away from the planet on the other side at 12:33 a.m. because it also will be hidden in Jupiter’s shadow. Early risers will be able to spot Saturn which will rise in the east-southeast at 1:54 a.m. It will appear below the Moon tomorrow morning.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The evening planets Mars, Venus, and Jupiter with the winter constellations at 9 p.m. March 11, 2015. Created using Stellarium.
Jupiter and moons at 9 p.m. March 11, 2015, about 29 minutes before Io moves behind Jupiter. Created using Cartes du Ceil (Sky Charts).
Jupiter and moons at 12:33 a.m. March 12, 2015, about when Io emerges into sunlight from Jupiter’s shadow. Created using Cartes du Ceil (Sky Charts).
Saturn and the Moon in Scorpius in the south at 6 a.m. March 12, 2015. Created using Stellarium.
Closeup of Saturn and the Moon at 6 a.m. March 12, 2015. Created using Stellarium.
What Saturn and its moons might appear like in a telescope at 6 a.m., March 12, 2015. Small telescopes will show only the moon Titan. Created using Cartes du Ceil (Sky Charts).
03/10/2015 – Ephemeris – The Great Orion Nebula
Ephemeris for Tuesday, March 10th. The Sun will rise at 8:04. It’ll be up for 11 hours and 37 minutes, setting at 7:42. The Moon, 3 days before last quarter, will rise at 12:43 tomorrow morning.
The constellation of Orion the hunter, now in the south at 9 p.m., contains the most beautiful star forming region in the northern sky. It is the Great Orion Nebula. A nebula is simply a cloud. Back in the early days of telescopes it was anything that appeared fuzzy. Today it’s any cloud, whether of gas or dust, light or dark. The Great Orion Nebula is made up of gas, which is ionized and shines by fluorescence by the ultraviolet light of a clutch of four stars in its heart called the Trapezium. The nebula can be glimpsed with binoculars surrounding what looks like the center star of the vertical line of three stars that appears as the sword hanging from Orion’s belt. It’s the bright end of a large dark cloud that’s behind the bright stars of Orion.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion upright and due south. Created using Stellarium.
The lower part of Orion with the Great Orion Nebula. Created using Stellarium.
Inner part of the Great Orion Nebula with the Trapezium. Image by Scott Anttila
Great Orion Nebula by Scott Anttila
