Download From Spyglasses to Space Telescopes

From Spyglasses to Space Telescopes
or
A Saga That Began With Galileo
Galileo Galilei
1564-1642
Galileo was…….
• An inventor
• Father of Experimental Physics
• Father of Modern Astronomy
Born: 15 Feb 1564
Pisa
Professor of Mathematics
University of Padua
1592-1610
1610: Chief Mathematician to Grand Duke of Tuscany
Cosimo II de Medici
Development of
Telescope
is linked to that of
spectacles
With age, the eye progressively
loses
its
power
to
accommodate,
that
is
to
change its focus from faraway
objects to nearby ones. This
condition, becomes noticeable
for most people in their forties,
when they can no longer focus
on letters/ books held at a
comfortable distance from the
eye.
Magnifying
glasses
became
common
in
the
thirteenth century for reading
Lipperhey (or Lippershey!) was a spectacle
maker in Holland. One story behind the
creation of the telescope states that two
children were playing with lenses in his shop.
The children discovered that images were
clearer when seen through two lenses, one in
front of the other. Lipperhey was inspired by
this and created a device very similar to
today's telescope.
Lipperhey
(or Lippershey!)
In 1608, Lipperhey found that while viewing a distant object through
combination of a convex and a concave lens, the object appeared closer
and magnified. For this purpose, however, the two lenses had to be
placed at just the right distance from each other.
Lipperhey never used his telescope to look at the stars. He believed
that his new invention would mainly benefit seafarers and soldiers and for spying purposes.
This is how the telescope was born - in the garb of a spyglass!
Significance of Galileo
• He did not just ‘use’ the telescope he fabricated his own …
• He did not just ‘see’ the heavens,
but applied scientific method to
interpret what he saw…
The actual term "telescope" was coined on April 14, 1611 by Prince Frederick
Cesi at a reception where Galileo was demonstrating one of his instruments.
Galileo’s telescope
Galileo found out about this
invention in the early 1609 and
immediately set about improving
it.
•He realized that the magnification was proportional to the ratio of the
power of the concave (eyepiece) lens to the convex (more distant)
lens.
•In other words he needed a weak convex lens and a strong concave
lens.
• Opticians only made glasses in a narrow range of strengths, and
three or so was the best magnification available with off the shelf
lenses.
Galileo learned to grind his own lenses, and by August 1609, he
had achieved about eight-fold linear magnification.
He
demonstrated his new invention to a gathering of officials on August
1609.
Galilean Telescope
Galileo used a long focal
length objective and a short
focal length eye piece. If the
focal length of the objective
is Fo and the focal length of
the eyelens is -Fe, the
distance
between
them
must be Fo - Fe, and the
power
(angular
magnification)
is
Fo/Fe.
Image is upright.
"When there are no glasses in the tube, the rays proceed to the object FG along
the straight lines ECF and EDG, but with the glasses put in they proceed along the
refracted lines ECH and EDI. They are indeed squeezed together and where
before, free, they were directed to the object FG, now they only grasp the part HI"
Galileo begins a revolution..
His
initial
version
had
magnification of 8x but was soon
refined to the 20x
He then turned his
telescope to the
Heavens…
January 19, 1610
stellar occultation
Galileo could see stellar occultation,
mountains on Moon, and so on. At one
stroke he could change the way the Moon
looked.
He observed that some parts
of the Moon were illuminated
well before its surroundings
by the sunlight. We know that
mountain tops are illuminated
at the dawn well before the
valleys. He built a convincing
case for the reality of the
mountains by sketching the
appearance of parts of the
Moon’s surface at different
times of the month, that is,
under different angles of
lighting.
Obviously
this
caused
an
uproar.
The
orthodox were enraged, how
can Galileo claim that Moon,
an celestial body to be
‘imperfect’ ?!
Sun is blemished, changing, and rotating
Galilean Moons
Galileo’s next major discovery began
with his observation on January 7,
1610, of what he took to be a rather
odd set of three small fixed stars
near Jupiter. These ‘stars’ were
invisible
to
the
naked
eye.
Observations over successive night
revealed that actually four star-like
objects in a line with it. The objects
moved
from
night
to
night,
sometimes disappearing behind or
in front of the planet. Galileo
correctly inferred that these objects
were moons of Jupiter and orbited it
just as our Moon orbits Earth. By
the 15th January 1610 had realized
that he was looking at moons of
Jupiter.
Through naked eye
Through telescope
Galileo then turned his attention to most numerous objects in the
night sky- stars. Rather to his disappointment the stars showed no
features- they were still point source, even through a telescope the
stars still appeared as points of light. Galileo suggested that this was
due to their immense distance from Earth. On turning his telescope to
the band of the Milky Way Galileo saw it resolved into thousands of
hitherto unseen stars. In like manner when ex explored the region of
Pleiades, he found stars that were unseen to naked eye. His
exploration of the Orion nebula also revealed unseen stars.
Galileo Galilei published Sidereus Nuncius, or the
'Starry Messenger ' in March 1610. In it he
provided a lively and accessible account of his
telescopic observations. This revolutionized the
astronomy – in fact all the sciences.
Copernicus
Galileo’s drawing of the phases of
Venus and modern photo-mosaic
Ptolemy
Observation of the phases of Venus helped establish the heliocentric theory on a firm footing.
His telescopic observation
of Saturn resulted in total
shock.
Initially
Saturn
appeared to have ears, and
latter
some
kind
of
appendage. Galileo could
not make sense of it.
Few decades later, Huygens
using a better telescope
resolved it as a ring around
Saturn.
In
any
case
Galileo’s
observation showed that
stellar objects need not be
perfect sphere.
Galileo's
extensive
telescopic
observations of the heavens
made it more and more plausible
that they were not made from a
perfect, unchanging substance.
In
particular,
Galileo's
observational confirmation of the
Copernican hypothesis suggested
that the Earth was just another
planet, so maybe it was made
from the same material as the
other planets.
It was radical and an epistemic
rupture
of
celestial
and
terrestrial.
Same laws of physics applied in
both cases. One set of science is
all that is required to explain
‘heaven and Earth’!
Just as Aryabhata was condemned for his views against the
purnaic myth of Rahu - Ketu, Galileo was punished by the
orthodoxy in Europe for daring to put forth his theories. He was
to suffer for many years for upholding science and spirit of
quest against mindless dogmas.
In July 1633, he was imprisoned and latter his sentence was
converted into life-long house arrest, because of health reasons. He
was not allowed to have contact with the outside world. Until his
death, even at his old age he kept working.
Down but not Out
Although Galileo was ill and mentally
exhausted, he started to write a book
about mechanics, based on his research
in Padua. This book, Discorsi, or
Dialogues Concerning Two New Sciences
was published by Elzevier in Leiden,
because it could, of course, not be
published in Catholic lands. The book
convincingly argued against the Earthcentered universe and upheld the
scientific spirit. No wonder the 400th
annivesary of Galileo’s use of telescope is
celebrated as International Year of
Astronomy.
JOHANNES KEPLER
1571 to 1630
A useful resource:
http://kepler.nasa.gov/johannes
1600: Meets Tycho
Brahe; 1601: Imperial
Mathematicus
Born: 27 Dec 1571
Weil der Stadt
1594-1600: Teacher of astronomy &
mathematics at the Protestant School in Graz
Mathematics: logarithms, calculus
Optics
Astronomy
The last scientific astrologer
Kepler published First two Laws of Planetary Motion in 1609 – A Fact
not much publicized!
This too exactly 400 years ago!
It’s the Law!
Planetary orbits are ellipses, with the Sun at one focus.
Planets sweep out equal areas in equal times
1618:
3rd Law
Motion
1619:
Third
Law of
of Planetary
Planetary Motion
Kepler's Third Law quantifies the observation that
more distant orbits have longer periods:
a
3
=P
2
Here, the semimajor axis a is measured in A.U. and
the orbital period P is measured in years.
1618: 3rd Law of Planetary Motion
P2 = a3
Standing on the shoulders of Johannes Kepler,through the analysis of
Kepler’s Laws of Planetary Motion, Isaac Newton discovered the Law of
Universal Gravitation.
Issac Newton built
mirrors, not lenses
a
telescope
from
Reflecting telescopes solved the problem of colored images obtained with
lenses, and other problems as well!
Reflecting Telescope: Schematic Diagram
A telescope in which light from the object is gathered and focused by
a concave mirror, with the resulting image magnified by the eyepiece.
A concave mirror reflects the light and brings it to a focus to
form a small inverted image
In both, refracting and reflecting telescopes, image formed will be inverted,
but this can be re-inverted by using extra lens. But this would not be required
in astronomical telescopes.
Recording what we see
Photographic film: in 1850, the first permanent
images recorded, but wet emulsions were very
slow, and long exposures were needed
“dry” emulsions made astrophotography much
easier!
Which ushers us into the
modern era…
First image of the
Moon, 1852
Telescopes are light buckets!
The greater the diameter of the
lens or mirror, the more light it
collects - and the fainter the
object we can see
Stars seen with larger and
larger telescopes
An older Refracting Telescope
The 0.9 meter Lick Refractor on Mt. Hamilton, CA
versus a 35 year old reflecting telescope
The 4 meter telescope at Kitt Peak
versus a very modern and large Reflecting
Telescope
The 8 meter Gemini North telescope at Mauna Kea
• The largest single telescope for visible and infrared light in the world
today is the Great Canary Telescope situated at La Palma, Canary
Islands, with the main mirror 10.4 m (410 inches) in diameter.
Asia’s largest
telescope of
2.34 meter
diameter
It is operated
by Indian
Institute of
Astrophysics
It is located at
175 km away
from Bangalore,
at Kavalur in TN
Vainu Bappu Telescope Observing
nights are
comparatively
large in
number
World’s highest
telescope(4.5km)
located at Hanle in J
&K
Telescope works in
optical and Near
Infrared region of
EMR
Himalayan Chandra Telescope
It is remotely
operated by Indian
Institute of
Astrophysics
Aperture is
2 metres with
Alt-azimuth mount
Located at the
height of about
1680 m and
located at Mt Abu
(Rajasthan)
It is operated by
Physical
Research
Laboratory,
Ahmedabad
Telescope works
in near- infrared
and optical
regions.
Gurushikhar Telescope
Aperture is
1.2 m.
Operating since
1994.
Undoubtedly…
Telescope is a striking example of how
technology could help push the frontiers of
science further ahead; and help improve our
understanding of the natural phenomena.
Discoveries with telescopes from the 1600s through the 1800s laid the
foundations for modern astronomy.
13 March 1781 Uranus was discovered by William Hershel and his sister
Carolina.
Neptune was discovered by Adams and Leverrier
by mathematically calculating where it should be
from the gravitational perturbation it caused on
the path of Uranus.
It was discovered in 1846. Thus it has not
even completed one round about sun since
its discovery.
Next, the asteroids between the orbits of Mars and Jupiter were
discovered. Between the orbit of Mars and Jupiter there are
numerous space rocks of varying sizes. These together are called
asteroids or minor planets.
Asteroids are composed of
rocks and boulders bound
together due to gravity and
the surface is covered with
fine dust
Newton’s colleague Edmond Halley used the new theory of
gravitation to calculate the orbits of comets. Based on his
calculations, he predicted that this comet would return in
about 1758. Although Halley had died by 1758, when the
comet did indeed appear as he had predicted it was given
the name Halley’s Comet.
The Astronomical Unit
Halley did not live to see Venus transits in his lifetime, but, his efforts
gave rise to many expeditions in 1761 and 1769 to observe the
transits of Venus which gave astronomers their first good value for the
Sun’s distance from Earth, that is, The Astronomical Unit (AU).
Pluto was discovered by American astronomer Clyde Tombaugh in 1930.
Pluto (which was formerly classified as a planet, then a dwarf planet, and
yet again classified as plutoid) has not yet been visited by a spacecraft. A
spacecraft launched in 2006 is expected to rendezvous with Pluto in
2015.
Hubble image of the
Sirius binary system,
in which Sirius B can
be clearly
distinguished (lower
left).
Telescopic studies of double stars, also known as binary star
systems, provided the evidence that gravity is truly universal and
that the same physical processes that we can study here on Earth
can be applied to studies of distant objects, including stars.
Observation through telescopes in 1838 helped measure distances
to stars.
In 1864 British astronomer Sir William Huggins showed that the pattern
of dark lines in the spectrum of a star matched the patterns produced
by elements known on the Earth. This showed that the physical
processes that we study here on Earth can be used to study the whole
universe. Study of spectra of stars provides information about their
temperatures, masses, and their motions in space.
As the 20th century began, Albert Einstein advanced his General Theory
of Relativity, which fundamentally changed our understanding of gravity,
and the Universe. One of the predictions of his theory was that the light
should bend as it passed by a massive body like a star. In 1919, a team
of astronomers led by British astronomer Sir Arthur Stanley Eddington
used the occasion of a total solar eclipse to measure the deflection of
starlight as it passed by the Sun and arrived at numbers that agreed with
Einstein’s predictions.
Edwin Hubble’s studies of distant
galaxies revealed that the universe
was not static, as had been
previously
believed,
but
was
expanding in size.
The second half of the 20th century was truly a golden age
for astronomy. Advances in technology expanded our vision
by enabling us to look at the heavens in different parts of the
electromagnetic spectrum and not just restrict our
observations to the visible part of the spectrum alone.
In a radio telescope, radio waves from celestial sources are
reflected by a metallic surface and are brought to a focus, then
sent to an electric receiver, where they can be recorded and
analyzed. Radio astronomy proved to be instrumental in verifying
the Big Bang theory of the origin of the Universe.
New windows on the Universe opened up with the ability to launch
spacecraft. Astronomical objects not only give off radio waves and light
of the kind that our eyes are sensitive to. They also emit other forms of
energy ranging from high-energy gamma rays and X-rays, to infrared or
heat radiation. Much of this electromagnetic radiation is absorbed by
Earth’s atmosphere and hence does not reach the ground. Technology
again made it possible to launch telescopes above Earth’s atmosphere to
observe the astronomical objects in different types of electromagnetic
radiation.
Hubble Space Telescope
Spitzer Space Telescope
Chandra X-ray Observatory
many spacecraft designed to exploit the advantages of being outside
Earth’s atmosphere have been launched. The Chandra X-ray Observatory,
the Spitzer Space Telescope, and the Hubble Space Telescope (HST) were
particularly powerful. Turbulence in the Earth’s atmosphere blurs
astronomical images. Because the Hubble Space Telescope is unaffected
by this blurring, it can take extremely sharp images and has given
astronomers both scientifically important and stunningly beautiful images
of planets, star clusters, and galaxies.
New Horizons to Pluto launched in 2006. To visit in 2015
Spacecraft have been sent to orbit all of the planets. Pluto
(which was formerly classified as a planet, then a dwarf planet,
and yet again classified as plutoid) has not yet been visited by
a spacecraft.
India’s Moon probe Chandrayaan-1 has already entered the lunar orbit
with an aim to observe it in the visible, near Infrared, low energy X-rays
and high-energy X-ray regions.
India is also poised to launch Astrosat, a satellite to observe and
study astronomical phenomena in 2011.
Now, we have discovered that our solar system is not the only one.
Astronomers have found some 350 planets orbiting other stars. Surely,
we have come a long way since Galileo observed the heavens through
his tiny telescope in 1609. Now telescopes on the ground and in space
explore the Universe 24 hours a day, across all wavelengths of light. Will
it bring us closer to our search of life elsewhere in the Universe?
Galileo lived at about the same time as Kepler (they did their most
important work around 1600-1610) and exchanged letters with him.
With the International Year of Astronomy 2009 (IYA 2009) we
celebrate a momentous event, the first astronomical use of a telescope
by Galileo, an invention that initiated 400 years of incredible
astronomical discoveries; and pay homage to one of the greatest of
scientists. Indeed, Galileo’s telescope triggered a scientific revolution
which has profoundly affected our world view. At the same time we
celebrate yet another momentous event - the publication of the first
two laws of Planetary Motions by Johannes Kepler.
. “Pure logical thinking”, Einstein once wrote, “cannot yield us any
knowledge of the empirical world; all knowledge of reality starts
from experience and ends in it. Because Galileo saw this, and
particularly he drummed it into the scientific world, he is the father
of modern physics – indeed of modern science altogether.”
THANK YOU