05/14/2015 – Ephemeris – The constellation Virgo in mythology

Ephemeris for Thursday, May 14th.  Today the Sun will be up for 14 hours and 46 minutes, setting at 9:02.   The Moon, 3 days past last quarter, will rise at 4:51 tomorrow morning.  Tomorrow the Sun will rise at 6:14.

Tonight in the sky: to the left of the constellation of Leo the lion, which lies in the west-southwest at 11 p.m. is the next constellation of the zodiac: Virgo the virgin, is seen in the south.  Virgo is a large constellation of a reclining woman holding a stalk of wheat.  The bright star in the center of the constellation, Spica, is the head of that spike of wheat; and as such ruled over the harvest in two of Virgo’s guises as the goddesses Persephone and Ceres.  Virgo is also identified as Astraea the goddess of justice.  The constellation of Libra, the scales, is found just east of her.  Early Christians saw Virgo as the Virgin Mary.  Virgo is the home of the Virgo Cluster of thousands of galaxies.

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

Addendum

Virgo with the also mentioned constellations of Leo and Libra for 11 p.m., May 14, 2015. Created using Stellarium.

Virgo as depicted in Urania’s Mirror, a set of constellation cards published in London c.1825. From the Library of Congress. H/T Wikipedia.

Libra as depicted in Urania’s Mirror, a set of constellation cards published in London c.1825. From the Library of Congress. H/T Wikipedia.

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

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 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.

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.

 

03/30/2015 – Ephemeris – The importance of meteorites and asteroids

Ephemeris for Monday, March 30th.  The Sun will rise at 7:27.  It’ll be up for 12 hours and 39 minutes, setting at 8:07.   The Moon, 3 days past first quarter, will set at 5:33 tomorrow morning.

On Friday the 3rd Joe Brooks will be giving a talk at the Grand Traverse Astronomical Society on meteorites.  That will be at 8 p.m. at Northwestern Michigan College’s Rogers Observatory.  NASA has the Dawn spacecraft now settling into orbit of the largest asteroid Ceres.  It is the asteroid belt that is the source of meteorites.  Meteorites are either pieces of destroyed protoplanets due to collisions in the asteroid belt or primitive objects like carbonaceous chondrites pristine that date back to 4.567 billion years ago, the formation of the solar system.  Meteorites tend to be contaminated by the environment.  That’s why samples of asteroids will be so valuable for planetary defense and understanding the origin of the solar system.

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

Addendum

Looking back at Vesta as Dawn headed off to Ceres. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

The bright spot is two. Picture taken February 19, 2015 from 29,000 miles (46,700 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

03/06/2015 – Ephemeris – Learn about this year’s adventures in exploring the soiar system tonight

Ephemeris for Friday, March 6th.  The Sun will rise at 7:12.  It’ll be up for 11 hours and 24 minutes, setting at 6:36.   The Moon, 1 day past full, will rise at 7:47 this evening.

This evening yours truly will be giving a program at the monthly meeting of the Grand Traverse Astronomical Society at 8 p.m. at Northwestern Michigan College’s Rogers Observatory.  It’s entitled Asteroids and Dwarf Planets and Comets, oh my!  It’s about the three solar system bodies being visited this year by spacecraft from NASA and the European Space Agency.  The asteroid is Ceres, which the Dawn spacecraft entered orbit of today.  The dwarf planet is Pluto which is the target of a summer flyby by the New Horizon spacecraft.  The comet is 67P/Churyumov–Gerasimenko orbited by ESA’s Rosetta spacecraft.  There will be a star party at 9 p.m. following the meeting.

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

Addendum

Apologies to MGM.

Looking back at Vesta as Dawn headed off to Ceres. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

The bright spot is two. Picture taken February 19, 2015 from 29,000 miles (46,700 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Artist conception of the New Horizons spacecraft at Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

An animation of Comet 67p/Churyumov–Gerasimenko rotation on July 14, 2014. The 30 pixel wide image has been smoothed. The Rotation rate is 1 rotation every 12.4 hours. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

03/03/2015 – Ephemeris – The bright spots on Ceres are still a mystery

Ephemeris for Tuesday, March 3rd.  The Sun will rise at 7:17.  It’ll be up for 11 hours and 15 minutes, setting at 6:32.   The Moon, 2 days before full, will set at 6:30 tomorrow morning.

The Dawn spacecraft is approaching the asteroid Ceres.  It will be gently captured by Ceres on the 6th.  This as an update from the date I gave you yesterday.  Then the spacecraft will spiral closer and closer to the asteroid over the next few months.  There is a mystery spot on Ceres, a bright spot that was visible by the Hubble Space Telescope orbiting Earth.  As Dawn got close enough to resolve Ceres it too saw the bright spot.  As the spacecraft got even closer the spot showed to be smaller and smaller.  I thought it might be a crater that penetrated into Ceres icy interior.  But the latest image, taken February 19th shows that the bright spot has a companion spot, both inside a crater and still too small to resolve.  It’s still a mystery.

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

Addendum

Hubble’s best photo of Ceres. Note the white spot near the top of the image. Image Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), L. McFadden (University of Maryland, College Park), and M. Mutchler and Z. Levay (STScI)

The white spot shows as Dawn approaches Ceres. Credit: NASA/JPL.

The bright spot is two. Picture taken February 19, 2015 from 29,000 miles (46,700 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

This photo will be the best photo of the bright spots until the end of April, an Dawn maneuvers over the night side of Ceres.

On March 2nd NASA held a Dawn Mission Pre- Close Approach News Briefing which can be found on YouTube.

03/02/2015 – Ephemeris – The Dawn spacecraft (The turtle wins the race)

Ephemeris for Monday, March 2nd.  The sun will rise at 7:19.  It’ll be up for 11 hours and 12 minutes, setting at 6:31.   The moon, 3 days before full, will set at 6:00 tomorrow morning.

On Thursday March 5th NASA’s Dawn spacecraft will fall under the gravitational influence of the asteroid, or actually recently promoted dwarf planet Ceres and enter orbit.  The journey took 7 years including an intermediate year-long stop at the asteroid Vesta.  Dawn uses the latest in ion thrusters, or latest when it was launched.  Using power generated by its solar panels it ejects xenon ions from one of its three ion thrusters to produce a thrust comparable to the weight of a piece of paper.  It can accelerate the spacecraft from zero to 60 miles per hour in a few days.  In the tale of the hare and the tortoise it’s in the tortoise class, at least to start.  Ion engines are 10 times as efficient as chemical rockets and they can thrust for years.

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

Addendum

Artist’s rendition of the Dawn spacecraft at Vesta. Credit: NASA/JPL

Ion engine test. Xenon ions glow blue. Credit NASA.

 

12/30/2014 – Ephemeris – Looking ahead at some local and space astronomical events in 2015

Ephemeris for Tuesday, December 30th.  The sun will rise at 8:19.  It’ll be up for 8 hours and 51 minutes, setting at 5:11.   The moon, 2 days past first quarter, will set at 3:38 tomorrow morning.

Let’s look ahead at a few astronomical and space events that will take place in 2015.  Visible for us will be the partial phase of a lunar eclipse in morning twilight of April 4th,  plus there’s a total lunar eclipse visible during the evening hours of September 27th.  Out in space in the asteroid belt the Dawn spacecraft will enter orbit of Ceres, the largest asteroid and dwarf planet Ceres, a spherical world of rock and ice in April.  Further out past the last planet the New Horizons spacecraft will fly by the dwarf planet Pluto and its system of at least 5 satellites: Charon, Nix, Hydra, Styx, and Kerberos on July 14th.   It will take several months to transmit the data and images back to Earth after which the spacecraft will be redirected to a new target.

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

Addendum

Chart for the total lunar eclipse of April 4, 2015. In Michigan we will see on;y the beginning partial phase in morning twilight. Credit: Fred Espenak, NASA/GSFC

Chart for the total lunar eclipse of September 28, 2015. This is the evening of the 27th, EDT in Michigan. Credit: Fred Espenak, NASA/GSFC.

Dawn orbital track past Mars, stopping at Vesta and continuing to Ceres. Credit: NASA/JPL.

Artist conception of the New Horizons spacecraft at Pluto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

02/25/2014 – Ephemeris – Mars starts its retrograde motion this weekend

Ephemeris for Tuesday, February 25th.  The sun will rise at 7:26.  It’ll be up for 10 hours and 58 minutes, setting at 6:24.   The moon, 3 days past last quarter, will rise at 5:15 tomorrow morning.

The planet Mars, which rises about 10:30 p.m. and is near the star Spica, is slowing its eastward motion as the Earth approaches it.  Mars will stop and appear to reverse course on Saturday March 1st.  It will begin what astronomers call retrograde motion.  This westward motion will continue past Mars’ opposition with the sun on April 8th, and its closest approach to the Earth on April 14th.  Mars retrograde motion will end on May 21st when Mars will resume its prograde or eastward motion.  The ancient Greeks especially had a problem with this because they believed that celestial bodies traveled in uniform circular motion.   They added a circle on the planet’s main circle called an epicycle to kind of solve the problem.  The problem was solved centuries later by Copernicus who made the earth another planet and Kepler who made the planet orbits elliptical.

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

Addendum

The trails of Mars and three asteroids from December 2013 to August 2014. Created using Stellarium.

Vesta and Ceres are going retrograde at the same time as Mars.  The Dawn spacecraft traveling between Vesta to Ceres is about half way in between them.  The other trail, not exhibiting retrograde is that of the small asteroid 2012 DA14 whose claim to fame is that it passed inside the ring  of geosynchronous satellites on February 15, 2013.  It was completely upstaged a few hours earlier by the meteor that exploded over Chelyabinsk, Russia.  It looks like the orbital trail shown for 2012 DA14 has not been updated.  As the result of the encounter with Earth that day the asteroid’s orbit was altered.  2012 DA14 is a provisional designation based on the year, half month and order of discovery.  It’s permanent designation with a name is 367943 Duende.  The name of the asteroid is usually up to the discoverer with the approval of the International Astronomical Union (IAU).  It is the 367,943rd asteroid whose orbital elements are known.  BTW Ceres is 1 Ceres, and Vesta is 4 Vesta.  Though the 4th asteroid found, Vesta is the brightest, at the very limit of naked eye visibility.

02/13/2014 – Ephemeris – Dwarf planet Ceres is the next stop for the Dawn spacecraft.

Ephemeris for Thursday, February 13th.  The sun will rise at 7:45.  It’ll be up for 10 hours and 22 minutes, setting at 6:08.   The Moon, 1 day before full, will set at 7:10 tomorrow morning.

The Dawn spacecraft is in the asteroid belt.  After spending a year orbiting the asteroid Vesta two years ago, it has set its sights on Ceres, the largest asteroid, which was promoted by the same reasoning that Pluto was demoted, as a dwarf planet.  Recently it was announced that Ceres is out-gassing water molecules.  Dawn, with its ion engine is slowly approaching Ceres and will enter orbit of the body in April next year, a few months before the new Horizons spacecraft will fly by the dwarf planet Pluto on Bastille Day 2015.  Dawn will stay in orbit of Ceres for a year at least.   It will take at least several months to download all the images and data from the Pluto encounter from New Horizons, so we will have a very eventful 2015.

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

Addendum

Artist’s rendition of the Dawn spacecraft at Vesta. Credit: NASA/JPL.

The asteroid belt n the inner solar system. Credit: NASA/JPL.

 

Dawn orbital track past Mars, stopping at Vesta and continuing to Ceres. Credit: NASA/JPL.

The Dawn spacecraft uses ion propulsion, which though 10 times more efficient than chemical fuels, has the thrust comparable to that of the weight of a piece of a piece of paper.  Consequently the spacecraft spends most of its time thrusting.   Since it’s antenna is bolted on the spacecraft, it cannot thrust and communicate with the earth at the same time, so it has to stop thrusting and turn toward the earth to report back at scheduled intervals before resuming thrusting again.

05/30/2013 – Ephemeris – The constellation of the harvest, Virgo

Ephemeris for Thursday, May 30th.  Today the sun will be up for 15 hours and 17 minutes, setting at 9:19.   The moon, 1 day before last quarter, will rise at 1:42 tomorrow morning.  Tomorrow the sun will rise at 6:00.

Tonight in the sky: to the south, with the bright Saturn to the left of the bright star Spica is the constellation and member of the of the zodiac: Virgo the virgin.  Virgo is a large constellation of a reclining woman holding a stalk of wheat.  The bright star in the center of the constellation, Spica, is the head of that spike of wheat; and as such it ruled over the harvest in two of Virgo’s guises as the goddesses Persephone and Ceres.  Virgo is also identified as Astraea the goddess of justice.  The constellation of Libra, the scales, which she is associated with, is found just east of her low in the southeast.  Early Christians saw Virgo as the Virgin Mary.  Virgo is the host to a grand cluster of galaxies.

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

Addendum

Virgo, Saturn and Libra at 11 p.m. on May 30, 2013. Created using Stellarium.