04/28/2015 – Ephemeris – Why do the stars of winter disappear so fast?

April 28, 2015 Leave a comment

Ephemeris for Tuesday, April 28th.  Today the Sun will be up for 14 hours and 6 minutes, setting at 8:43.   The Moon, 3 days past first quarter, will set at 4:32 tomorrow morning.  Tomorrow the Sun will rise at 6:36.

At 9:30 p.m. the winter constellation of Orion is above the western horizon, but barely visible in the bright twilight.  The sun is moving eastward and northward, setting at about 1 minute and a quarter later each night.  That minute and a quarter is due to the Sun’s northward motion north.  The Sun’s eastward motion, which is actually the Earth’s orbital motion around the sun, makes the stars set approximately 4 minutes earlier each night.  That’s because our time is kept based on the Sun, not the stars.  What happens is that the winter stars seem to disappear rather rapidly.  We lose the bright stars and constellations of winter which are replaced by the sparser constellations of spring.

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

 

04/27/2015 – Ephemeris – Two large craters on the Moon for binoculars or a small telescope

April 27, 2015 Leave a comment

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

Moon

The Moon at 10 p.m. April 27, 2015 EDT (2:00 UT, April 28). Created using Virtual Moon Atlas.

04/24/2015 – Ephemeris – The Dawn spacecraft is descending to dwarf planet Ceres’ day side

April 24, 2015 Leave a comment

Ephemeris for Arbor Day, Friday, April 24th.  Today the Sun will be up for 13 hours and 54 minutes, setting at 8:38.   The Moon, 1 day before first quarter, will set at 2:26 tomorrow morning.  Tomorrow the Sun will rise at 6:42.

The Dawn spacecraft with its ion engine is descending into orbit of that other dwarf planet Ceres, the largest body in the asteroid belt.  Over the past month Dawn has been maneuvering over Ceres’ night side to descend into a polar orbit to better survey the planet.   Last week the Jet Propulsion Laboratory team that has been operating the spacecraft released a video of several photographs of Ceres’ pole as it rotated.  It was still a crescent view, but soon we’ll see Ceres up close and very personal.  We’ll get a closer look at those enigmatic white spots.  Are they just white ice patches on the surface, or are they ice cryovolcanoes spewing water, or something else?  Stay tuned.

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

Addendum

Ceres amimation

Ceres animation from April 14-15, 2015. Dawn was 14,000 miles (22,000 km) from Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.  Click the image to enlarge.

This is a newer animation than the one mentioned in the transcript above that was actually written on the 19th.  Here’s a link to the NASA page that describes the image.  It also has a link to an enlarged frame containing the double bright spot.

Processed image

This is a processed still image of Ceres from the above animated sequence of images.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

There’s no help figuring out what they are but the smaller spot is resolved into two spots.  The bright one is still unresolved.  As of yesterday the Dawn spacecraft should be in its first circular orbit of Ceres at an altitude of  8,400 miles (13,500 km) from Ceres for a few weeks before descending to a lower orbit of Ceres the starting the first week in May.

 

04/23/2015 – Ephemeris – New Horizons’ first glimpse of Pluto and Charon in color

April 23, 2015 Comments off

Ephemeris for Thursday, April 23rd.  Today the Sun will be up for 13 hours and 52 minutes, setting at 8:37.   The Moon, 2 days before first quarter, will set at 1:44 tomorrow morning.  Tomorrow the Sun will rise at 6:43.

Last week NASA’s New Horizons team running the spacecraft that’s been in flight to the dwarf planet Pluto released their first color of Pluto and it’s moon Charon.  The photo doesn’t show any surface features.  That’s to come in the next month or two.  However, Pluto shows kind of a pale orange-pink color, hinting of the colorful images to come.  Charon is a dull gray like the dwarf planet Ceres, which Dawn is approaching, and our own Moon.  How could two bodies with a common origin appear so different?  Stay tuned.  New Horizons will pass through the Pluto system in a couple of hours on July 14th, but will send back the mother lode of its data over the next 16 months.

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

Addendum

Pluto and Charon

First color picture of Pluto and its moon Charon taken by the New Horizons spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.  Click to enlarge.

From the NASA website:

“This image of Pluto and its largest moon, Charon, was taken by the Ralph color imager aboard NASA’s New Horizons spacecraft on April 9 and downlinked to Earth the following day. It is the first color image ever made of the Pluto system by a spacecraft on approach. The image is a preliminary reconstruction, which will be refined later by the New Horizons science team. Clearly visible are both Pluto and the Texas-sized Charon. The image was made from a distance of about 71 million miles (115 million kilometers)—roughly the distance from the Sun to Venus. At this distance, neither Pluto nor Charon is well resolved by the color imager, but their distinctly different appearances can be seen. As New Horizons approaches its flyby of Pluto on July 14, it will deliver color images that eventually show surface features as small as a few miles across.”

04/22/2015 – Ephemeris – All the bright planets are back now

April 22, 2015 Comments off

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

Evening Twilight Planets

View to the west with Mars, Mercury, Venus and the Moon at 9:15 p.m. April 22, 2015. Created using Stellarium.

Jupiter finder

Jupiter, the Moon and the setting winter constellations at 10 p.m. April 22, 2015. Created using Stellarium.

The Moon

The visibility of the Moon at 10 p.m. on April 22, 2015. Created using Cartes du Ciel (Sky Charts).

Jupiter and moons

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

Saturn rising. Shown at midnight, April 22-23 2015. Created using Stellarium.

Saturn finder chart

Saturn and the summer constellations at 5:45 a.m. April 23, 2015. Created using Stellarium.

Saturn and moons

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

April 21, 2015 Comments off

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, Venus and the Hyades

The Moon with Venus and the Hyades at 9:30 p.m. April 21, 2015. Note the Pleiades on the right.  Created using Stellarium.

04/20/2015 – Ephemeris – The Lyrid meteor shower will reach peak Wednesday evening

April 20, 2015 Comments off

Ephemeris for Monday, April 20th.  The Sun rises at 6:50.  It’ll be up for 13 hours and 43 minutes, setting at 8:33.   The Moon, 2 days past new, will set at 10:57 this evening.

This week the Lyrid meteor shower will reach its peak.  The expected peak will be Wednesday the 22nd at 8 p.m. (24 hr UT). Unfortunately the radiant point will not have risen by then.  The radiant, near the star Vega in the constellation of Lyra will rise in the northeast by 10 p.m.  It will approach the zenith by 6 a.m. as morning twilight brightens.  The normal peak hourly rate is about 18 when the radiant is at the zenith,  This year it could be as many as 90 per hour.  However Europe and Asia will be prime locations to view the shower near the  zenith at peak.  The shower is caused by the debris of Comet Thatcher, seen only once in 1861.  When comets approach the Sun they shed gas, dust and small bits of rock.  When the Earth passes through it we get a meteor shower.

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

Addendum

Lyrid meteor radiant.

Lyrid meteor radiant is near Lyra and the bright star Vega. Th bright star by “Lyr” is Vega. Create by Bob Moler’s LookingUp program.

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