Download Eclipse of the Sun 1 September 2016

Presentation on observation of the partial
eclipse of the Sun of 1 September 2016
Workshops for Educators
2 and 3 August 2016
Rajiv Gandhi Science Centre, Bell Village
Mauritius Astronomical Society
&
Rajiv Gandhi Science Centre
Presentation outline
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The Sun
The Moon
Movement of the moon around the earth
Eclipse of the Sun
Precautions
Eclipses in History
What is the Sun ?
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Is the nearest star to us, and the
only one we can study in detail
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Is the central body around which
the planets orbit
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Is sometimes seen from Earth to
be “crossed upon” by three
natural objects :

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Mercury (transit of Mercury)
Venus (Transit of Venus)
Moon (Eclipse of the Sun)
Birth of the Sun
The Sun formed about 4.6 billion years ago from the collapse of
part of a giant molecular cloud that consisted mostly of hydrogen
and helium
Some figures about our Sun
Diameter
Distance to earth
Distance to earth
Mass
Composition
Surface temperature
Temperature at centre
Energy source
Distance to furthest planet Neptune
Distance to nearest other star
1.4 million km
150 million km
One Astronomical Unit = 1 AU
2x 1030 kg (300,000 earth masses)
70% H, 28% He, 2% others
6000 oC
15 million oC
Nuclear fusion (H into He)
30 AU
271000 AU
Sun, Earth and Moon to scale
Sun – Basketball
Earth – Small pea – 32 m away
Moon – pinhead – 1 thumb-length away from Earth
The earth in orbit
What is the Moon?
• The only natural satellite of
the planet Earth
• One of more than 96 natural
other moons in our Solar
System
• 384,000 km from Earth
• 3500 km in diameter (about ¼
the size of Earth)
Movement of the Moon
• Revolution – Moon orbits
the Earth every 27.3 days
• Rotation – Moon turns on
its axis every 27 days
• The moon rises in the east
and sets in the west
• The moon rises and sets
50 minutes later each day
• Same side of Moon always
faces Earth
Solar Eclipses
• A solar eclipse occurs when the moon
passes in front of the Sun as seen from
Earth.
• The shadow of the moon then touches
the earth
Three types of Solar Eclipses
• Total Solar Eclipse – can only occur if someone is at
the exact spot inside the moon’s umbra (which isn’t
very big).
• Partial Solar Eclipse – Visible if someone is in the
penumbra of the shadow. Only some of the moon
will be shadowed.
• Annular Eclipse – occurs when the moon is farthest
from the Earth in its orbit. This makes the moon look
smaller, so during the eclipse you see an outer ring of
light from the Sun.
Eclipse geometry (total and partial)
Eclipse geometry (annular)
This will be the geometry for Reunion island as the moon will be at apogee
(greatest distance from earth in its orbit) and will appear slightly smaller in size
compared to the solar disk
When do solar eclipses happen ?
• Lunar Eclipses happen more often than Solar
Eclipses.
• Everyone who is experiencing nighttime
during a lunar eclipse can see it.
• However one has to be at the exact spot on
Earth to see a Solar Eclipse.
• Since that spot on Earth is very small, one
given place only sees a Solar Eclipse every 350
years, on average
Eclipse path on 1 September 2016
Why don’t eclipses happen every month?
• The answer lies in the slight tilt (5o) of the Moon’s path in relation to the
Earth’s path.
• It is usually above or below the direct sight line to the Sun.
Earth
Moon’s
tilted
orbit
Sun-Earth
plane
Partial Solar Eclipse montage
This montage shows the entire eclipse as it will be visible in steps from Mauritius.
Mauritius will experience only a partial lunar eclipse as it lies in the penumbral
region
At maximum eclipse, 95% of the surface of the Sun will be covered
Annular Solar Eclipse – As visible from Reunion island
as it will be in the annular cone of the shadow.
Deep partial eclipse
The eclipse will look like this from Mauritius
Annular Eclipse – occurs when the moon is farthest from the
Earth in its orbit. This makes the moon look smaller, so during
the eclipse you see an outer ring of light from the Sun.
The eclipse will look like this from Reunion island.
Animation for the Solar Eclipse
• The animation is made using Stellarium
software
• Stellarium is a free open source planetarium
for computers
• It is freely dowloadable at: http://www.stellarium.org
Times for the Solar eclipse for Mauritius
Precautions for watching an eclipse-I
• It is never safe to look directly at the Sun except
during a total eclipse
• A partial or annular eclipse can cause
permanent eye damage, even when the Sun is
mostly covered at 99% as in Reunion island, even
though you might not feel any discomfort at the
moment of unaided watching.
• Looking at the Sun through any kind of
unfiltered optical aid (binoculars, a telescope, or
even a camera’s viewfinder) is extremely
dangerous, and will cause permanent blindness
Precautions for watching an eclipse -II
• Sunglasses do not provide adequate protection,
as they do not block the wavelengths which are
dangerous
• Various other filters, such as welder’s goggles or
using fully exposed and developed black-andwhite negatives, are sometimes discussed. Unless
you know exactly what you are doing (ie very
brief observation), can be extremely dangerous.
• They are not recommended for observation by
children.
Safest method for children 1 – Use special solar
eclipse glasses
Can be safely used to observe the Sun directly
Safest method for children 2 - The
Pinhole camera
• Make a circular hole of 3mm-4mm on one small side of
a large packing cardboard box. This hole can also be
made in aluminium foil, so that its diameter can be
adjusted.
• Cut a large rectangular opening on the opposite side of
the large cardboard. The two sides must be of the long
side of the box apart.
• Stick a large piece of tracing paper on the rectangular
opening to completely cover it
• The Sun’s light will be "projected" through the pinhole
and form an inverted image on the other side of the
cardboard box
• You can then look at safely at the image on the tracing
paper from outside.
The Pinhole camera
Method to use with care 1 - Eyepiece
projection - binoculars
• Use binoculars on a tripod
• Place a cardboard on the binoculars
as a shade
• Place a second cardboard some
distance away, as a screen
• Hide the unused side of the
binoculars
• Point the binoculars towards the sun
• Observe the screen safely from a
distance
• Do not let any child come close to
the eyepiece
• DO NOT LOOK THROUGH THE
EYEPIECE TO LINE UP !
• NEVER WATCH THROUGH THE
EYEPIECE !
Method to use with care 2 - Eyepiece
projection- telescope
• This method is to be used only by
experienced telescope users
• Use a telescope on a tripod
• Place a cardboard on the telescope as a
shade
• Place a second cardboard some distance
away, as a screen
• Point the telescope towards the sun
• If the telescope is not motorised, then it
must be manually steered so as to track
the sun
• Observe the screen safely from a distance
• Do not let any child come close to the
eyepiece
• DO NOT LOOK THROUGH THE EYEPIECE
TO LINE UP !
• NEVER WATCH THROUGH THE EYEPIECE !
Method for experienced observers with a
telescope : Front filtered instrument
• This method must be used only
be experienced telescope users
who are familiar with the use of
a motorised telescope
equipped with a front filter
• The front filter must be safely
secured at the front of the
instrument
• Rear filters that are placed at
the eyepiece are not to be used
as they can crack under the
intense hear of the unfiltered
sun through a telescope
Taking pictures with a digital camera
and telephoto
Solar eclipses in history
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Many ancient civilisations were able to predict eclipses accurately, as far back as the
Babylonians 3000 years ago.
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Solar Eclipses have historically been viewed in the ancient past as omens that bring about
death and destruction. King Henry's Eclipse: King Henry I died shortly after an eclipse in
1133, prompting the spread of the superstition that eclipses are bad omens for rulers
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Solar eclipses are in reality harmless, when observed with the right precautions.
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The word eclipse comes from ekleipsis, the ancient Greek word for being abandoned.
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A total solar Eclipse in 1919 was used to test Albert Einstein's theory of general relativity.
By taking pictures of stars near the Sun during totality, scientists were able to show that
gravity can bend light from stars, also called gravitational refraction.
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Helium is named After Sun. A solar eclipse is also responsible for the discovery of chemical
element Helium. This element is the second lightest and the second most abundant
element. It was discovered during a Total Solar Eclipse in 1868. Because of this, it's named
after the Greek word for the Sun - Helios.
Eclipses and Astronomy popularisation
Eclipses are very successful in the popularization
of sciences through appreciation of Astronomy
Early astronomy involved observing the regular
patterns of the motions of visible celestial
objects, especially the Sun, Moon, stars and naked
eye observations of the planets.
wikipedia
Astronomy is the oldest of the natural sciences,
dating back to antiquity, with its origins in the
religious, mythological, and astrological practices of
the ancient civilizations.
wikipedia
The changing position of the Sun along the horizon
or the changing appearances of stars in the course
of the year was important to establish agricultural
calendars or navigation.
Astronomy Today
Astronomy consists of a series of disciplines including:
Solar astronomy:
Studies of our own star, the Sun
Planetary science:
Studies of the bodies in our own Solar System and those in orbit around other stars
Galactic astronomy:
The study of our own Milky Way and its evolution
NASA/JPL
Stellar astronomy:
The study of stars and stellar evolution
Extragalactic astronomy:
The study of objects outside of our Milky Way
NASASpitzer
Cosmology:
The study of the Universe as a whole.
Astronomical Research Today
Astronomers around the world study
the workings of the Universe.
• Ground-based telescopes ( visual, radio,
gravitational, neutrino)
• Space based observatories
• Robotic probes
• Theoretical calculations and simulations
ESO
Today, this is being done through a combination
of many disciplines and sub-fields using many
different approaches;
ESO
Astronomers study the Universe not only to
further our understanding of the cosmos, but to
advance other fields of science and technology
too.
Thank you !