22nd July 2009 – Eclipse third contact

Diamond ring at third contact. These images of the eclipse were taken from Tian Huang Ping, Anji, China.

This sequence took about 21 seconds in real time.

20th March 2009 11:44 UTC – Vernal Equinox

Today at 11:44 UTC (roughly the same as GMT).

The center of the Sun crosses the equatorial plane from south to north. On the equator the sun passes directly overhead. At the poles the Sun is on the horizon the whole day. On this day the Sun spends roughly the same length of  time over and under the horizon so day and night are roughly equally long at all places on Earth.

Vernal equinox  comes from the latin ver = spring, aequus = equal and nox = night (day and night of equal length).

14th March 1835 – Giovanni Schiaparelli born

Giovanni Schiaparelli was born on this day in 1835. He is perhaps best known because, as noted in Wikipedia:

he observed a dense network of linear structures on the surface of Mars which he called “canali” in Italian, meaning “channels” but mistranslated as “canals”.

Interestingly (or not) Google celebrates his birthday with this logo:

13th March 1781 – Uranus discovery announced

From Wikipedia’s post on Uranus:

Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the solar system for the first time in modern history. This was also the first discovery of a planet made using a telescope.

Sir William Herschel was not the first person to observe Uranus – John Flamsteed beat him to it. But Flamsteed did not recognise Uranus for what it was. The credit for the discovery therefore goes to Herschel.

7th January 1610 – Galileo observes Jupiter moons

Utklipp fra Wikipedia’s entry for Galileo Galilei:

On 7 January 1610 Galileo observed with his telescope what he described at the time as “three fixed stars, totally invisible by their smallness”, all within a short distance of Jupiter, and lying on a straight line through it. Observations on subsequent nights showed that the positions of these “stars” relative to Jupiter were changing in a way that would have been inexplicable if they had really been fixed stars. On 10 January Galileo noted that one of them had disappeared, an observation which he attributed to its being hidden behind Jupiter. Within a few days he concluded that they were orbiting Jupiter. He had discovered three of Jupiter’s four largest satellites (moons): Io, Europa, and Callisto. He discovered the fourth, Ganymede, on 13 January. Galileo named the four satellites he had discovered Medicean stars, in honour of his future patron, Cosimo II de’ Medici, Grand Duke of Tuscany, and Cosimo’s three brothers. Later astronomers, however, renamed them Galilean satellites in honour of Galileo himself.

The significance of the above is the following…
This was one of the earliest known astronomical observations using a telescope. The discovery that Jupiter had moons orbiting it was pivotal in displacing the Aristotelian Cosmology which held that all heavenly bodies circle the Earth. This discovery supported the  Copernican model of the Solar System where the Sun and not the Earth is at the centre. Galileo’s discovery in September of the same year that Venus displayed phases like the Moon  showed that Venus orbited the Sun, not the Earth.

27th December 1571 – Johannes Kepler born

Johannes Kepler (1571-1630) played a major role in the scientific revolution. He is best known as the discoverer of the three Laws of Planetary Motion. He did this by studying the observations made by Tycho Brahe (1546-1601) of planetary motion.

Kepler was instrumental in replacing our Geocentric – Earth centered -  view of the Universe with a heliocentric – Sun centered – view. This heliocentric view would later fall. Two major mileposts on our way towards a modern view of our Universe.

Kepler’s three laws are stated in our times thus:
First Law:
The orbit of every planet is an ellipse with the sun at a focus.
Second Law:
A line joining a planet and the sun sweeps out equal areas during equal intervals of time.
Third Law:
The square of the orbital period of a planet is directly proportional to the third power of the semi-major axis of its orbit. Moreover, the constant of proportionality has the same value for all planets.

The first law describes the shape of a planet orbit. The second law tells us that a planet moves faster when closer to the Sun than when further away. The third law tells us that the length of a planet’s year depends on its distance from the Sun. The further out a planet orbits the Sun; the longer its year is.

Isaac Newton was later able to derive these laws using his Theory of Gravitation.

Start rant…

Did you notice that a Scientific Law describes how natural phenomenon behave?

A Scientific Theory on the other hand explains why things follow the laws they are observed to follow.

The scientific use of the words law and theory differ from the common use of these words.  In common use a Law is a rule agreed upon by common agreement and a theory is an untested idea that has not been proved. In common use a theory is weaker than a law. In science the opposite is true.

Note that scientific theories are never proved to be true. Theories can either be proved false (rare) or (more commonly) replaced by a new theory that explains natural phenomenon even better.  Newton’s Laws of Gravitation have not been replaced by Einstein’s General Theory of relativity. Relativity is just more accurate than Newton’s Theory in extreme situations.  When sending a probe to the Moon; Newton’s Theory of Gravitation works just fine. Sending a probe into orbit round a black hole on the other hand would require use of Einstein’s General Theory of Relativity because the velocities in question are much closer to the speed of light and therefore more extreme.

…end rant.

Mercury – MESSENGER images – flyby 2

MESSENGER has successfully completed its second flyby of Mercury. Her is a sample of the first images returned. Clicking on the images sends you to the MESSENGER image gallery where you can see high resolution versions of these images.

Links of interest:

Wikipedias entry on Messenger
Wikipedias entry on Mercury
My post on MESSENGERs first flyby

Rosettas flyby of Steins

The first images from ESAs space probe Rosettas closest approach to the asteroid Steins are now available.

Images from Rosetta flyby of Steins

Steins is a main belt asteroid in orbit around the Sun between Mars and Jupiter. Rosettas closest distance to Steins was 800 kilometers. Steins is about 5.9 by 4 kilometers large – mountain sized.

Emily Lakdawalla at The Planetary Society has updated her montage that compares the sizes of comets and asteroids that have been imaged. Here you can see the relative size of Steins to other objects imaged by space probes.

Relative sizes of asteroids and comets

NASA Renames GLAST to Fermi Gamma-ray Space Telescope

NASA has announced that GLAST is to be renamed to Fermi Gamma-ray Space Telescope.

NASA Renames Observatory For Fermi, Reveals Entire Gamma-Ray Sky

WASHINGTON — NASA’s newest observatory, the Gamma-Ray Large Area Space Telescope, or GLAST, has begun its mission of exploring the universe in high-energy gamma rays. The spacecraft and its revolutionary instruments passed their orbital checkout with flying colors.

NASA announced today that GLAST has been renamed the Fermi Gamma-ray Space Telescope. The new name honors Prof. Enrico Fermi (1901 – 1954), a pioneer in high-energy physics.

“Enrico Fermi was the first person to suggest how cosmic particles could be accelerated to high speeds,” said Paul Hertz, chief scientist for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “His theory provides the foundation for understanding the new phenomena his namesake telescope will discover.”

Links:

NASA – NASA Renames Observatory For Fermi, Reveals Entire Gamma-Ray Sky.
NASAs GLAST web page
Wikipedias entry on Enrico Fermi

15th August 1977 – Wow! signal detected

The Search for Extra Terrestrial Intelligence (SETI) has been conducted using radio telescopes for many years now. The Wow! signal was received on the 15th August 1977 by Dr. Jerry R. Ehman on the Big Ear radio telescope of Ohio State University. The signal lasted for 72 seconds and fit all the expected criteria for a signal from outside our solar system. Dr Ehman was so impressed that he wrote “Wow!” beside the printout of the signal hence the name Wow! signal. Many unsuccessful attempts have later been made to re-detect the signal. Its origin remains unknown and open to speculation.

Wow! signal printout

Dr. Ehmans  30th anniversary report recounts the details.