 |
|
There
are two equinoxes every year that take place when the sun’s rays strike earth’s
equator resulting in near equal days and nights. This year autumnal equinox is today September
23rd at 2:29 UniversalCoordinated Time. The word equinox
derives from Latin and means equal nights. Those who are interested in the
history of equinoxes please check on the post Spring Equinox at Porto Rafti. I hope you all had a good spring and summer. I wish to all of you, my friends, a good fall and winter too.
As I
have described the history of equinoxes, I thought a suitable panegyric of today’s
autumnal equinox would be brief references to two remarkable space journeys. The
first is about spacecraft Rosetta
that was launched on March 2, 2004 by the EuropeanSpace Agency (ESA) and which after 10 years and a trek of 6.5 billion
kilometers is at a distance of 285 kilometers from the comet
67P/Churyumov-Gerasimenko (C-G) and looking for a suitable landing site. In November this year it will deploy its
lander onto the C-G surface. Rosetta’s
lander named Philae will take pictures
perform physical and chemical analyses of the comet’s ice and organic material,
information that may proviBde answers to the genesis and evolution of our solar
system. This information will allow us to look back 4.5 billion years when
no planets existed and only a vast number of asteroids and comets surrounded
the Sun and formed the building blocks of our Solar System. On August 3rd the Rosetta
spacecraft took the above stunning picture of the C-G
comet. (picture
credit @ ESA)
|
 |
|
The second amazing expedition is NASA's
Mars Atmosphere and Volatile EvolutioN (MAVEN)
to the Red Planet. The MAVEN spacecraft, which was launched in November 2013,
arrived at Mars on Sept. 21, 2014 and began one-year mission studying the
planet's upper atmosphere. (Credit @ National Geographic/NASA)
|
 |
|
Humans have been fascinated with the Cosmos
since the dawn of history. Ancient
astronomers regarded comets as bad omens, a reputation that took many centuries
to overcome.
Ancient Greeks as well as other philosophers
advanced a number of different theories in their attempt to explain the nature
of comets. To some like Seneca comets
were celestial bodies like planets. To others such as Aristotle they were burning clouds or optical phenomena in the
Earth' atmosphere a view that prevailed for some 2000 years.
Our understanding of comets experienced a
dramatic leap forward with the appearance of a Great Comet in 1577, which was
as bright as Venus and had a tail forty times long the diameter of the full
Moon. Its appearance offered the Danish colorful astronomer Tycho Brahe a unique opportunity to
study them. Brahe observed
that there was no measurable parallax as the comet's position in the sky
differed very little from measurements performed at other latitudes across Europe.
According to Brahe's calculations, the comet appeared to be at least four times
farther than the Moon, so he deduced that it must belong to the heavens and not
in our Earth’s atmosphere. (picture credit @ NCAR)
|
If you stand at the equator on the first day of spring, you will see the sun pass directly over head. This only happens twice a year; first day of spring and the first day of autumn.
ReplyDeleteBaby birds learn to sing during spring. Although they are born with the ability to sing, they must learn the specific songs of their species. They often learn their songs within two months of being born.
Arizona and Hawaii do not follow daylight savings. They already have enough sunlight and hot weather, so it doesn't make sense to confuse the sleeping cycle of their residents.
Daylight Savings Time saves approximately 1% of electricity a day. It adds up to a lot when figure in the entire nation (except Arizona and Hawaii of course).
The Great Sphinx in Egypt points directly East towards the sunrise on the vernal equinox.
Spring fever is a real syndrome. When the temperature rises during the warm spell after a long winter, there is a dilation of the blood vessels so blood can be carried to the body surface where heat can be lost quickly. People experience an energetic feeling when this happens.
Benjamin Franklin was the first to propose daylight savings time in 1784. It wasn't fully implemented until the end of the Second World War.
This isn't Rosetta's first cosmic rodeo. It made three flybys of Earth and 1 of Mars in order to gain enough speed to get past Jupiter on its way to meet up with the comet. The spacecraft also managed to get some views of the asteroids Steins and Lutetia before going into hibernation in 2011.
ReplyDeleteAlthough Rosetta and Comet 67P/C-G are flying about 251 million miles (450 million km) from Earth right now, that number is slightly deceiving. Since its launch in 2004, Rosetta has been speeding through the solar system on a circuitous journey to catch up with its comet target.
In total, the Rosetta probe spent a decade traversing about 4 billion miles (6.4 billion km) to make its historic rendezvous with Comet 67P/C-G on Aug. 6. The probe and the comet are now only about 62 miles (100 km) from each other.
3) Rosetta will drop a lander on the comet
At the moment, Rosetta is carrying a special lander poised to launch to the surface of Comet 67P/C-G in November. Rosetta is currently tracking a triangular orbit around the comet; however, it will move into a circular orbit and start getting closer to the surface of the comet as weeks go on, gearing up to release the Philae lander.
Before Philae touches down, mission controllers will scope out a series of potential landing spots for the probe. Once on the surface, Philae will beam back data about the composition of the comet, getting an up-close-and-personal view of the cosmic body.
In addition to characterizing the comet nucleus and setting the bar for the rest of the mission, final preparations will begin for another space history first: landing on a comet,"
How Big Is Comet 67P/Churyumov–Gerasimenko? It is compared to various mountains and buildings on Earth. It is as big as a mountain, Rosetta's target comet is 2.5 miles wide (4 km), meaning that if it were plopped down on Earth, it would actually be larger that Mount Fuji in Japan, which is about 2.3 miles (3.8 km) high. Objects that look like boulders on the comet's surface are actually as large as houses.
Rosetta gets closer and closer to the celestial object the VIRTIS instrument on board the spacecraft is designed to create temperature maps of the comet's features.
The $1.7 billion (1.3 billion euros) Rosetta mission is expected to last until December 2015.
Rosetta has been traveling in space with the Philae lander. Philae is designed to fly down to the comet's surface and study it in tandem with Rosetta. Because of the comet's incredibly low gravity, engineers cleverly found a way to land the probe safely on the celestial body and when Philae reaches the surface of the comet, it will harpoon itself into place to keep it from ricocheting back off into space.
Rosetta's comet is dark and dusty. It's probe collected some interesting data about the object's possible composition. Some of the first data collected by Rosetta once it was near the comet shows that Comet 67P/C-G is incredibly dry. Scientists expected to see patches of ice on the comet's surface because it is currently flying so far from the sun, but they didn't find large patches of ice, the analysis showed the comet is actually dark and dry.
They expect that as the comet gets closer to the sun, it will become more active as its particles react to the heat of the star. It's darker than charcoal in ultraviolet wavelengths, according to research.
The comet doesn't look like anything expected, instead of a round icy body, Rosetta was greeted by a "rubber ducky"-shaped comet. The comet appears to have two lobes: a "head" and a larger "body" connected by a relatively thin neck. Philae's landing site is a sunny but rocky location on the head of the comet. It was not born in the shape we see it today, it might even be a fragment of a larger comet, it might be just a fragment that evolved to the shape we see it today.
Amazing what goes on up there beyond and past the earth into the vast sky!
Maria, these are excellent comments. I want to thank for the additional information that provides useful material to those who like to know more.
Delete