http://labroots.com/user/activity-group/index/id/42/title/astronomy-astrophysics | LabRoots presents an overview of some of the major discoveries in cosmology, astronomy and physics, including Halley’s Comet, exoplanets, and Kepler’s Laws of Planetary Motion.

1. From Galileo to
Hubble and Beyond
Important discoveries in astronomy
over the centuries

2. Highlights of Important Astronomical
Discoveries
• The 20th and 21st centuries have been an
incredible period of discovery in astronomy,
cosmology, physics and many other scientific
disciplines.
• The centuries leading up to modern times
were especially pivotal in helping
astronomers understand the movement of
planets, their satellites, and the cosmos at
large.
• Following are highlights of some of the key
inventions and discoveries of the last several
centuries that have helped shape our
understanding of the universe.

3. Lippershey Invents the Refracting
Telescope
• In 1608 Hans Lippershey, a Dutch eyeglass
maker, invented the refracting telescope.
• The invention of the telescope began a
revolution in astronomy, and the device
spread rapidly around Europe.
• Interestingly, the patent Lippershey filed in
1608 was never actually issued, as other
spectacle-makers claimed to have invented
the telescope.

4. Kepler’s Laws of Planetary Motion
• German astronomer Johannes Kepler published the book New
Astronomy in which he described the three laws of planetary
motion, as follows:
1. Planets have an elliptical orbit with the Sun at one of the
two foci.
2. A line joining a planet and the Sun sweeps out equal
areas during equal intervals of time.
3. The square of the orbital period of a planet is proportional
to the cube of the semi-major axis of its orbit.
• Kepler’s scientific works would later become the foundation of
Isaac Newton’s theory of universal gravitation.

5. Galileo Supports Copernican
Heliocentrism
• Galileo supported the Copernican theory of a Suncentered universe based on observations he made
with his hand-built telescope.
• In the 2,000 years preceding Galileo’s discoveries
the long-accepted theory was an Earth-centered
one in which the sun and planets in our solar
system revolved around the Earth.
• Among Galileo’s observations were craters on the
moon, spots on the Sun and four of Jupiter’s
satellites. Galileo’s findings were published in the
pamphlet Sidereus Nuncius.

6. Isaac Newton and His Apple
• In 1668 English physicist Isaac Newton built the first reflecting
telescope.
• In 1687 he established the theory of gravitation and laws of
motion, as outlined in his book Philosophiae Naturalis Principia
Mathematica.
• Newton explained Kepler's laws of planetary motion in Principia,
shedding light on the forces acting between the Sun, planets and
their satellites.
• It is said that Newton was inspired to formulate his theory of
gravitation after watching an apple fall from a tree. Although this
has become something of a myth, accounts from Newton’s
friends suggest there may be some truth behind the claim.

7. Edmond Halley and His Comet
• In 1705 English astronomer Edmond Halley
predicted that comets seen between the years 1456
to 1682 were one and the same.
• The comet returned in 1758 as Halley predicted it
would, and was later named in his honor.
• Halley’s Comet is visible with the naked eye and
reappears every 75-76 years; it is the only comet
that a person may see twice in a lifetime.

8. Herschel Discovers Uranus
• In 1781 German astronomer Frederick William
Herschel discovered the planet Uranus and two of its
major moons, Titania and Oberon.
• Herschel initially mistook the planet for a comet.
• Uranus was the first planet discovered beyond Saturn
up to that point.
• Among Herschel’s other accomplishments was his
discovery of infrared radiation – an important
contribution considering that half of the total energy
Earth received from the Sun arrives in the form of
infrared.

9. Big Bang Theory
•
According to Big Bang Theory, all the matter in the
Universe was once compressed into an infinitely dense
and hot point, which began expanding approximately
13.7 billion years ago.
•
Big Bang Theory holds that space and time did not exist
before the expansion of the universe, but rather came
into existence after the expansion began.
•
Once the universe cooled sufficiently, elements formed,
leading to the formation of stars, planets and other
celestial objects.
•
Einstein’s theory of general relativity was pivotal in the
development of the Big Bang theory. The theory is
broadly accepted in the scientific community and was
even pronounced to be in accordance with the Bible by
the Catholic Church in 1951.

10. If You Believe They Put a Man on the
Moon
• On July 20, 1969 the extraordinary happened
when the USA’s Apollo 11 spacecraft landed on
the moon. Neil Armstrong became the first man to
set foot on the moon.
• There have been six manned landings on the
moon, all of which occurred between 1969 and
1972. Twelve men in total have landed on the
moon, including Neil Armstrong and "Buzz" Aldrin.
• There have been many unmanned moon landings
as well, including a “soft” landing of a rover on
December 14, 2013 operated by the China
National Space Administration.

11. Hubble Space Telescope Discoveries
• Launched into orbit in 1990 and still in operation today,
the Hubble Space Telescope has been an
indispensable tool for astronomers, helping them
determine the age of the universe and understand how
dark energy is accelerating the universe’s expansion.
• The telescope was named after American astronomer
Edwin Hubble, who discovered the expanding universe
and determined that Andromeda is actually a galaxy
rather than a nebula, as previously thought.

12. The Discovery of Exoplanets
• Exoplanets, also known as extrasolar planets, are planets that revolve
around other stars in our galaxy and beyond.
• Astronomers weren’t able to prove the existence of exoplanets until
the early 1990s; in 1992, several terrestrial-mass planets were found
orbiting a pulsar known as PSR B1257+12.
•
• To date, more than a thousand confirmed exoplanets have been
discovered, including 175 multi-planetary systems, and the Kepler
space telescope launched in 2009 has discovered more than 3,500
additional candidate planets as of late 2013.
• Among the most common methods of locating exoplanets is the transit
method, whereby astronomers look for dimming on the surface of a
star to indicate the passing of a planet in front of the star from the
perspective of the observer.

13. Our Accelerating Universe
•
• In 2011 Adam Riess, Brian Schmidt, and Saul Perlmutter were awarded to
the Nobel Prize in Physics for their discovery that the expansion of the
universe is accelerating.
•
The scientists discovered that the expansion rate of the universe is a
timescale, not a speed, and that the universe expands at a fixed rate, which
essentially means that it takes a fixed amount of time for the universe to
double in size.
•
In ten billion years, for example, any particular galaxy observed will be twice
as far away; in twenty billion years it will be four times as far away, and in
thirty billion years it will be eight times that far away, thus indicating that the
acceleration of the universe is expanding.
•
The acceleration discovery is significant, as it changes our understanding of
what the universe will look like billions of years from now.

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