May Apogee Moon

may26-apogee   The Moon reaches apogee, (greatest distance from Earth), this month on Tuesday May 26th at 22 UT (5 pm CDT). At that time the Moon will more or less be at a distance of 31.69 Earth diameters (404,244 km or 251,186 miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*

*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   The 9-day old waxing gibbous Moon rises during the early afternoon hours and sets about 3 hours before sunrise.

   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Leo Leaps Over the Moon!

   Sunday evening May 24th the nearly first quarter Moon, will be within about 4o from the heart of Leo the Lion, the star Regulus.

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Moon – Jupiter – Asteroid- Star Cluster Conjunction

   Saturday evening May 23rd the waxing crescent Moon will be close to Jupiter, two open star clusters (M-44, M-67), and an asteroid. As this graphic shows, within the field of view of 7×50 binoculars, you can see the Moon, Jupiter, and the asteroid 3 Juno. A slight shift in the viewing brings either of the two open star clusters into the binocular field of view.

   M-44, also known as the Beehive Cluster, is a group of around 1000 stars at a distance of 500-600 light years and shining with a combined magnitude of approximately 4.0. To the naked eye M-44 looks more like a nebula but resolves nicely into its component stars with optical assistance. M-67 in comparison is much dimmer at a distance of 2500-3000 light years, and with only around 100 stars this open star cluster shines with a combined 6th magnitude brightness.

   Asteroid 3 Juno was the 3rd asteroid to be discovered and is one of the largest asteroids in the main belt between Mars and Jupiter. Juno has an apparent magnitude of around 7-8 so it is within the viewing capabilities of binoculars albeit as a star-like point of light.

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Saturn at Opposition

   Saturday May 23rd the outer planet Saturn reaches its orbital position known as opposition. This is a position which has the Earth centered between the outer planet and the Sun. Picture the arrangement with the Moon at full phase; Sun – Earth – Moon, and that is similar to the arrangement for Saturn at opposition; Sun – Earth – Saturn.

   When an outer planet, like Saturn, reaches opposition that planet rises around local time for sunset and is visible all night.

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Sun Not in Gemini

may-view-from-earth-astrology  According to the pseudoscience of astrology the Sun enters the constellation of the Gemini Twins on Thursday 21 May at 9 UT (4 am CDT). When in fact the actual position of the Sun on this date is still within the boundary of the constellation of Taurus the Bull, as this graphic and the banner graphic show.

   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   
   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Which Way is North? Part 3

The Magnetic Compass
compass   A compass used for navigation is essentially a magnetized needle or bar mounted on a point so that it may freely pivot or swing around in any horizontal direction. In the Northern Hemisphere, the north-seeking end of the needle swings around to align itself parallel with a magnetic line of force, and in doing so, points toward the north magnetic pole. Use the link “Magnetic Effects in Space” in the Internet Resources below to watch astronaut/scientist Owen Garriott on a Skylab mission use a bar magnet to demonstrate the Earth’s magnetic field and lines of force.
   Because the north magnetic pole is not located where the true North Pole (geographic) is located, an adjustment called magnetic declination is made. The magnetic declination is the horizontal angle difference between geographic north and magnetic north. Using the magnetic-field calculator at the NOAA website (see Internet Resources below), you can easily determine the magnetic declination for your location, or any other location on Earth, for that matter. By comparing different locations and dates it becomes apparent that the angle for declination not only varies daily as the north magnetic pole migrates, but there is also a difference in magnetic declination based on both latitude and longitude. For example, at the latitude and longitude of Cambridge Bay, the magnetic declination is 8.07º; using the coordinates for Washington, DC, 39º N, 77º W, the magnetic declination is -10º51’. Negative magnetic declination values indicate that the north magnetic pole is to the west of the location, while positive values have the magnetic pole to the east of the location. From the nation’s capital, the north magnetic pole is toward the northwest, while from Cambridge Bay it would be to the northeast.

   Use this link to see a list of magnetic pole locations from 1590 through 2015 at the NOAA web site.
   Using the years above and this link to see an interactive world map where you may set the date to see the lines of magnetic declination for that time period.

compass   As previously described, a compass has a freely spinning needle balanced on the point from which it spins. When held flat in one’s hand, the needle quickly swings back and forth as it aligns itself with the magnetic lines of force. At lower latitudes, such as those within the continental United States, the compass needle mostly swings left or right as it aligns parallel with the magnetic field and lines of force. As one approaches the magnetic pole, the needle is still parallel with the magnetic lines of force and responding by swinging left or right. However, near the poles, the angle of the magnetic lines of force, with respect to the Earth’s surface, are now approaching vertical; as a result, the compass needle is pulled downward, rather than moving side to side, as would be the case at lower latitudes away from the magnetic pole. In effect, the downward pull on the needle creates increasing resistance on the formerly freely swinging horizontal motion the needle had at lower latitudes. At some point, the needle simply stops moving from side to side.

(Adapted from my January 2013 Scope on the Skies column)

Previous: Which Way is North – Part 1?
Previous: Which Way is North – Part 2?

Internet Resources
Magnetic effects in space—http://archive.org/details/skylab_magnetic_effects
Magnetic field calculators—www.ngdc.noaa.gov/geomag- web/#declination
The Magnetic Sun—http://solar.physics.montana.edu/ypop/Spotlight/Magnetic
Motion of the magnetic pole—http://image.gsfc.nasa.gov/poetry/activity/s8.htm
Planetary magnetic fields PowerPoint—http://education.gsfc.nasa.gov/nycri/units/pmarchase/3b-magnetic_field.ppt
POETRY—http://image.gsfc.nasa.gov/poetry
IMAGE–http://image.gsfc.nasa.gov/

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Which Way is North? Part 2

Earth’s Magnetic Field
magnetic poles-lines   The Earth’s magnetic field, like a bar magnet, has a north and a south magnetic pole, with magnetic lines of force resembling meridians of longitude in that the magnetic lines of force come out of one pole and follow the curve of the Earth toward the other pole. Each magnetic pole is at a location where the magnetic lines of force converge and are vertical. This point on the Earth’s surface is also known as the dip pole, as this is the one location in each hemisphere where a compass needle, if designed to swing in all directions, would point straight down with a dip angle of 90º. Interestingly, neither magnetic pole is at the same location as its corresponding geographic pole. For example, the current location of the north magnetic pole is at approximately 81.3º N, 110.8º W. The word current has to be used because the location of the magnetic poles changes constantly due to variations in the processes that create the Earth’s magnetic field.
   There is an interesting history behind the search for the magnetic pole and you could learn about the migrating magnetic pole and practice mapping and geographic skills by using the teacher-created activity Motion of the Magnetic Pole (see Internet Resources below). This is one of many lessons and activities developed by a cadre of teachers participating in POETRY, the education outreach of NASA’s IMAGE (Imager for Magnetopause- to-Aurora Global Exploration) mission. The IMAGE mission was a six-year mission ending in 2005 that focused on a study of the Earth’s magnetosphere by imaging the magnetosphere in non visible wavelengths. Use the POETRY website (see Internet Resources below) to find lessons and activities written by classroom teachers for all grade levels.

(Adapted from my January 2013 Scope on the Skies column)
Previous: Part 1 – Which Way is North – Part 1
Next Up: Part 3 – The Magnetic Compass

Internet Resources
Magnetic effects in space—http://archive.org/details/skylab_magnetic_effects
Magnetic field calculators—www.ngdc.noaa.gov/geomag- web/#declination
The Magnetic Sun—http://solar.physics.montana.edu/ypop/Spotlight/Magnetic
Motion of the magnetic pole—http://image.gsfc.nasa.gov/poetry/activity/s8.htm
Planetary magnetic fields PowerPoint—http://education.gsfc.nasa.gov/nycri/units/pmarchase/3b-magnetic_field.ppt
POETRY—http://image.gsfc.nasa.gov/poetry
IMAGE–http://image.gsfc.nasa.gov/

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.