Category Archives: Earth and Space

Postings pertaining to Earth and Space Sciences including current celestial events, exploration, and education.

October Moon at Ascending Node

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   Around midnight local time Saturday night October 19th or very early Sunday October 20th the 21-day old waning gibbous Moon rises. As it is rising the Moon will be crossing the plane of the ecliptic moving north. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is actually the Earth’s orbit and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.

   On the day of the node crossing the waning gibbous Moon will be around the kneecaps of the Gemini Twins with the ‘Twin Stars’, Pollux and Castor about 12o east from the Moon.

   Does our Moon actually go around the Earth as many graphics show? 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)

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Moon in Conjunction with Uranus

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   Wednesday October 16th the 18-day old waxing gibbous Moon will rise in the east near the two open star clusters in the constellation of Taurus the Bull. These are the Hyades, a v-shaped asterism making up the face of the Bull, and the Pleiades (aka the 7 Sisters) a small dipper-shaped group of stars on the shoulder of the Bull.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Along the Ecliptic

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   Every once in a while the planets arrange themselves along the horizon and when that happens visualizing the ecliptic is somewhat obvious. For the next week or so all of the naked-eye visible planets except Mars, plus Neptune and Dwarf Planet Ceres, will be above the horizon at sunset local time. If you wait about an hour the Moon and the planet Uranus will rise above the eastern horizon as Mercury and Venus have set in the west.
   The ecliptic is actually the Earth’s orbit and it is used as a reference ‘line’, properly known as the plane of the ecliptic, for all of the Sun orbiting objects. Since few if any Sun orbiting objects have orbits that are on the same plane as the Earth but rather these objects are tilted or inclined either above or below the plane of the ecliptic. This is know as inclination. (Table Source: https://en.wikipedia.org/wiki/Orbital_inclination)

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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October Apogee Moon

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   Our Moon reaches apogee, (greatest distance from Earth), for this orbit, on Thursday October 10th. At that time the Moon will be at a distance of 31.82 Earth diameters 252,216 miles (405,902 km) from the Earth.

   On the day of the apogee Moon the 12-day old waxing gibbous Moon rises about 1-2 hours before sunset local time and is above the horizon the remainder of the night hours, setting at around sunrise the following morning.

   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)

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.


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2019 Martian Summer Solstice

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A Martian Year

A Martian Year – at One Earth Month Intervals

   Tuesday October 8th marks the summer solstice on the planet Mars as Mars transitions from spring to summer during its 684 Earth day orbit around the Sun. Seasons on Mars are marked by the planet’s heliocentric longitude coordinates using the position of Mars along its orbit around the Sun. Each seasonal start/ending point is 90 degrees apart, but because of its elliptical-shaped orbit each Martian season is of varying lengths.

   I’m not exactly sure why this particular date is used but by international agreement astronomers have selected 11 April, 1955 as 0 degrees for year 1 of this Martian calendar. What this means is that on Tuesday October 8th, Earth time, it is the start of summer during year 35 using the aforementioned calendar system.

Year 35
0 degrees — Spring Equinox — March 23 2019
90 degrees — Summer solstice — October 08 2019
180 degrees — Fall Equinox — April 08 2020
270 degrees — Winter Solstice — September 02 2020

Year 36
0 degrees — Spring Equinox — February 07 2021
90 degrees — Summer solstice — August 25 2021
180 degrees — Fall Equinox — February 24 2022
270 degrees — Winter Solstice — July 21 2022

Learn a little (or a lot) more about the exploration of Mars at the NASA Journey to Mars web site.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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October Moon near Saturn, at Descending Node, and It’s International Observe the Moon Night

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   Saturday October 5th the Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.

   On the day of the node crossing the 7-day old first quarter Moon will be over the southwestern horizon and will be about 1-2o to the east from the ringed planet Saturn. Jupiter shines brightly further to the west near the reddish star Antares. With binoculars or telescope the dwarf planet Ceres may be visible.

   Saturday evening is also International Observe the Moon Night. There may be a telescope set up in your area for observing the Moon, Saturn, and Jupiter. Depending on local weather of course!

   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Moon in Close Conjunction with Jupiter

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   Wednesday evening October 3rd the 5-day old waxing crescent Moon will be about 1-2o from -2 magnitude Jupiter. Should make for a great view using binoculars. Keep an eye on the Moon over the next few days as it continues moving eastward and waxing toward first quarter phase and the planet Saturn.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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