Lecture 1: ‘The Night Sky Around Us’ March 27 2015

MVNSC: Mississippi Valley Night Sky Conservation:

Program developed by:

  • Mississippi Valley Conservation Authority in partnership with:
    • Royal Astronomical Society of Canada
    • Ottawa Astronomy Friends
  • Instructor: Pat Browne
    • Assistant: Bob Hillier
  • References used in this course References
  • Course runs Fridays: March 27, April 10, April 17, May 1 and May 8.
  • Note: Donations can be receipted as charitable . Donations can be made online to Mississippi Valley Conservation via canadaHelps Choose Night Sky Conservation fund
  • Course time: 7:45 – 10:00 formally with priority given to observing when clear sky .

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 The Night Sky above Mississippi Mills: Mar 27 2015 courtesy Stellarium

5 lectures covering observations of the night sky posted at the MillstoneNews Science and Nature/NightSky News at https://millstonenews.com/category/columnists/night-sky-news

COURSE LECTURES

  • Celestial Sphere – Vast expanse of interstellar space
  • Lunar Observations – First Quarter Moon
  • Stars within our galaxy – Our Milky Way
  • Star Clusters – Galactic and Globular in the Milky Way
  • Galaxy Clusters – Beyond our own Galaxy

HOW TO OBSERVE THE NIGHT SKY AROUND US

    • Logbooks and handbooks
      • Observer’s Handbook – RASC
      • Isabel Williamson Lunar Observing
      • Beginners Observing Guide – RASC BOG
      • *YOUR* Logbook (Without a logbook you’ll always be a beginner)

Postings for the course, and discussion group are at the Mill of Kintail Night Sky Conservation Yahoo Group. Mill of Kintail – Night Sky Conservationists (You can join here by requesting invitation)

ACTIVITIES

  • Visit to Fred Lossing Observatory (FLO)
  • Dark Sky Observing
    • Observing with binoculars and telescopes
    • Constellation Practice with Handouts
  • Lunar and Planetary Observing
    • First Quarter Lunar Observing
    • Lunar and Planetary Groupings
  • Instructional Videos and tips on Night Sky Conservation
  • Night Sky Conservation:

    Night Sky Bylaw created in partnership with Mississippi Valley Conservation and the Royal Astronomical Society of Canada>

    • Dark skies in Mississippi Mills preserved in concert with our Night Sky Bylaw
    • Bylaw implements program of Good Neighbour Dark Sky Lighting: Shield Outdoor Light fixtures to protect the ‘extinction’ of the Milky Way
    • Celestial objects in outer space remain visible on clear night – comets, distant suns, clusters of stars, and galaxies
    • Humans need darkness as well as light. We cannot sleep well with constant artificial light around us – Light pollution causes physical and psychological discomfort
    • Night vision (scotopic) is different from day vision (photopic). Humans suffer from bright light glare finding it hard to adjust to the night sky.
    • Educate people about the night sky environment and encourage astronomical discovery such as cometary discovery. Amateurs collaborate with professionals!
    Our Dark Sky Site Long History of 'Looking Up'
    • Built by the scientific community with high-quality optics from the National Research Council of Canada.
    • Moved from North Mountain Ontario to save it from growing light pollution.
    • Thanks to the preservation of our Dark Skies… FLO comet-hunters used visual observations through the telescope: DISCOVERED 5 comets, making FLO the only observatory in Canada to do this.

This is comet Garadd captured Spring 2012 images courtesy P. Browne

  • Star ship Earth within its Celestial Sphere

    We are all travelling together through space on a giant starship – our home planet Earth.

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  • The Celestial Sphere or Sky Globe is a model of what we see above our heads
    It extends infinitely in all directions from our place on earth.
      • The celestial North Pole is an extension of our North Pole.

     

  • The Celestial Equator is an extension of our equator.
  • These directions extend infinitely through space.
      • The constellations as organizations of star patterns projected onto this imaginary sphere

     

  • They act as pointers to help us find the stars, clusters of stars in and beyond our own galaxy.

Sky Globe – Earth-Sky Relationships:

From aboard our ‘star ship’ we can look out in various directions at the universe that surrounds us…

NightSky Observation of Stars and Constellations depends on

    1. Latitude (our location on Earth)

    2. Time of Year (Earth’s orbital position in space)

1. Our North/South Location (Latitude) on Earth

Our Night Sky Horizon:
North Celestial Pole is always the same number of degrees above our northern horizon as you are above the Earth’s equator.

For each location on earth, we orient the Horizon, counting down by the number
of parallel Latitude lines.. Set the horizon and then visualize the globe of stars we can see projected unto the Celestial Sphere.
As we stand on the earth looking up:

  • 1/2 of the sphere is obscured by the earth itself. This hemisphere is bounded by the plane we call the horizon plane.
    • For earthlings observing at the Equator, their latitude is 0 degrees ; so the Celestial North pole is 0 degrees above the Equator
      • Equatorial astronomers see stars in both the Northern and Southern Hemisphere.
    • For earthlings observing at the North Pole, their latitude is 90 degrees; so the Celestial North Pole is 90 degrees above the Equator
      • Polar astronomers see only stars in the Northern Hemisphere
      • When the Sun travels below the Celestial Equator there are days of only stars…
      • When Spring and Summer return the Sun remains above the horizon later and later until we see the midnight Sun
  • Since our latitude is 45 degrees, our Celestial North Pole has an altitude of 45 degrees above the horizon.

During the day, the dazzling brilliance of the daytime star (the Sun) overwhelms everything else in the sky.When sunlight illuminates the atmosphere:

  • The Sun is the brilliant Star above our horizon
  • Other stars in the sky are not visible until the Sun sets below the horizon.
  •  Certain celestial objects remain permanently below the horizon for a given location on Earth above or below the equator.

 

 

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2.Time of Year = Location of the Earth in its Orbit

The Constellations change around our Earth Orbit

  • As the earth orbits around the Sun in the year, the night sky will contain different objects, different constellations.
  • Because our orbit around the sun changes our direction in space, it changes what constellations are visible when the Sun is below the horizon.

The sky in different times of year:


Courtesy R. Dick, The Celestial Sphere, Starlight Theatre
Here is a link describing what happens to our sky as we travel in our yearly orbit: A Year on Earth.
Note Small errata: The position of the sun on vernal and autumnal equinox is 1/2 point on the graph midway up the y-axis
 not the cross-over point on the Analemma

Heavens Above – Night Sky Objects, Seasonal and Transitory

Typical objects to view if the night sky is clear:

    • Nearby neighbours like the moon, and planets:
          • Recently Venus and Mercury, then Venus and Mars were closely paired and the moon was also in the same area of sky.

       

      The Parade of Planets

 

  • 7 other satellites of the Sun and the moon lie in the plane of the ecliptic.

 

 

 

    • Beyond to more remote light sources which originated in our galaxy. The star patterns we see at different times of year are patterned into Constellations.

 

 

    • A constellation is different from an asterism . Constellations are groupings of stars that are recognized as fixed star patterns on the celestial sphere. A set of 88 officially recognized constellations completely covers the sky.. The brightest stars help delineate their form.

 

  • Milky Way – more than 200 billion stars. All of these celestial objects form a majestic backdrop to the velvet canvas of night:

 

 

  •  We use constellations as a set of featured patterns that guide us to finding our star clusters in binoculars or telescopes
  • Objects such as a star cluster (thousands of light years away)
  • Everything seen in the stars of a constellation, or star clusters is found within our own Milky Way galaxy (100,000 light years).

 


However we can look out and see other galaxies, particularly in the spring time because our pointing direction in our orbit at this time of year projects outward away from the disk of the Milky Way galaxy .

Our Nearest Neighbours – Solar System:

Planets, comets and asteroids wanderers around the Celestial Sphere they move night after night in relation to Earth

The Planets and Cometary objects in our Solar System are visible to us when
their orbit takes them away from the glare of the sun into our night sky:

  • Hence we do planetary and comet observations when they appear above our horizon as they travel along the ecliptic (or, for comets, on their eccentric heliocentric path) after the Sun has set below the horizon.
  • In different years, we will see planets at different times. Their position is not fixed on our celestial sphere. They are wanderers, and may become morning or evening stars depending on their proximity to the Sun.
  • Our Solar System: Read more here @ https://millstonenews.com/2014/04/night-sky-course-planets-earth-and-orbits-around-the-sun.html

Our Distant Suns – Stars and Constellations on the Celestial Sphere

We can also use a 2-dimensional aid , a Planisphere to determine what is over our heads way up in the sky tonight:

Planisphere “Plan your Sphere!”

Plan your Moon!

Here are some tips on how to observe the moon at first Quarter Observing Tips – The Lunar Landscape

The Effect of Moonlight on viewing Deep Sky Objects or… (Where have all the stars gone?)

If we go out and try to observe star clusters, galaxies, and stellar nebula in lots of moonlight, we will not have any luck!

Light from the Moon …

 

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Light from Artificial Sources:

 

See the Canadian Student’s documentary on achieving a Dark Sky Campus

 

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When the moon transits in the evening, the ‘faint fuzzies’ fade away… Now is the time to observe the moon.

 

Standard names for Phases of the Moon

 

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Courtesy – RASC – Beginners Observing Guide (Leo Enright)

New Moon It is the period when the moon rises and sets with the sun (roughly). This is the time to observe Deep Sky objects (such as objects in the Messier Catalog which include stellar nebulae, Open Clusters, Globular Clusters and Galaxies). Solar eclipses occur during new moon as the moon passes in front of the Sun and blocks light to earth if it is aligned directly between Earth and Sun. Doesn’t happen every month because the moon’s orbit is inclined 5 degrees with respect to the plane of the earth’s orbit around the Sun.

 

First Quarter One week after new moon, and the moon appears in the night sky, and sets after midnight. It is said to be ‘waxing’ or growing. It is roughly 50% illuminated. Deep Sky objects are hard to see. This is a good time to view the features of the moon near the terminator where light and shadow are apparent. (More on that later)

 

Full Moon One week later (2 weeks after New Moon) we see the fully illuminated moon, and not much of the deep sky! The moon appears like a flat disk. Shadows have fled, and the bright, washed out appearance is good for a going for a walk in the moonlight.

 

Third Quarter The moon is said to be ‘waning’ . Again, a good time to see the features on the moon.

 

To understand the lighting on the moon – try this:

 

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Courtesy – Mary Lou Whitehorne – Astronomy Handbook For teachers (publ. RASC)

Note: Briefly, the Moon orbits the Earth in an ellipse, so sometimes it’s closer than other times. On average, it’s most distant point (apogee) is about 405,000 km and at closest (perigee) it’s about 363,000 km. The term "supermoon" refers to a full or new moon at perigee. The observed size of the moon may vary with 1-2%, and tides are stronger due to the slightly larger increase in gravitational pull - but not enough to cause earthquakes!

Lunar Observations: Early Observations: Galileo Galilei – Italy 1610 – Lunar Features as Mountains and Craters measured from shadow lengths

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Galileo observed that the line separating lunar day from night (the terminator) was smooth where it crossed the darker regions of the moon, but quite irregular where it crossed the brighter areas.

From this observation, he deduced that the darker regions are flat, low-lying areas, while the brighter regions are rough and covered with mountains Based on the distance of sunlit mountaintops from the terminator, he estimated that the lunar mountains were at least 6kms in height

Here is a description of Galileo’s procedure as a video

Because of the view during first quarter week (1/2 lit) we can see the mountain height from light rays straight to the moon and perpendicular to us. : Measuring Mountain Heights – Galileo

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Note also that the diameter of the moon in terms of Earth radii was estimated during a lunar eclipse:
Based on a total eclipse of the Moon, the Greeks determined the Earth’s shadow in terms of the the Earth’s diameter: 3.5 Moon diameters.So the lunar diameter was estimated at roughly ~ 12,756/3.5 ~ 3700 km
courtesy http://www.nuffieldfoundation.org/practical-physics/diameter-moon

For Origin and Evolution of the Moon, and the Interactions between the Earth and the Moon – see: https://millstonenews.com/2014/03/lunar-science-understanding-our-lunar-explorations.html

See Lunar Observing and the Isabel Williamson Lunar Guide (Millstone News article)