The bad thing about science is that it lets us know just how precarious our position is.  Our ancestors were blissfully ignorant, thinking they were living in a safe and unchanging world.  Now we know that this was only a misconception caused by lack of knowledge.  As we get smarter, we realize just how dangerous this universe is, and how quickly and completely our little corner of it could change.  All the bodies of the solar system, including Earth, are pockmarked with the prints of past impacts, and more of them are being discovered all the time.

There are many examples.  In 2004, for instance, a systems analyst in Buenos Aires, Max Rocca, was indulging his hobby of poring over Landsat images online, when he noticed something unusual.  There is a river in Colombia called the Vichada which travels through miles of dense jungle before finally reaching the Orinoco.  For most of its course, the Vichada travels in a very predictable way, following the natural shape of the land.  Max Rocca had some training as a geologist, and he could tell where the path of the Vichada River should be in that landscape.  For most of the river’s course, he was absolutely right.  Only at one point did it deviate from the expected course, and that was where it turned at almost a right angle, traced a perfect semicircle through the jungle, and then returned to its former path.

Apparently there was a semi-circular feature on the land at that point, which had never been found before because the jungle growth obscured its outline.  Rocca knew it shouldn’t be there.  There was nothing in the normal seismic and erosional forces shaping this landscape that should have made a perfectly round depression there.

Further investigation showed that the crook in the Vichada River was following a ridge along one side of a circular depression 50 kilometers wide.  A shallow depression surrounded by a ridge of hills is the classic signature of an impact crater, and this was the biggest one every found in South America, 50 kilometers wide.

While Mr. Rocca certainly deserves kudos for his discovery, such features are not rare.  One truly spectacular example is Vredefort Crater in South Africa, which at 300 kilometers wide, is the largest confirmed impact crater on Earth.  (The Wilkes Land Crater in Antarctica is even larger at 500 km., but has not yet been confirmed to be an impact crater.)   Luckily, this event occurred some two billion years ago.  If such an impact happened today, it would induce an “impact winter” effect that would disrupt agriculture on a global scale, resulting in widespread famine and the probable extinction of many of the lifeforms on the planet- especially big ones at the top of the food chain (that’s us).

Of course, the situation is much better now than it was back then, because many of the rocks that were whizzing around two billion years ago have already hit something, but there are still plenty of rocks flying around the sun that are big enough to cause vast destruction.  When you consider the consequences of a single event of the magnitude of Vredefort or even the Vichada impact, it is impossible to ignore the threat.

With this in mind, there has been a lot of very serious discussion in recent years about what we can do if an asteroid or comet is found to be on a collision course with Earth.

The issue is being addressed by various organizations around the world, some associated with specific national governments and others of an international nature.  In 1998, NASA established its Near-Earth Object Program and set a goal of locating at least 90 percent of the estimated 2,000 asteroids and comets larger than one kilometer that approach Earth by the end of the following decade.  Unfortunately, it is now 2010 and this goal has still not been reached, but it probably will be realized in the next few years (see the article on the WISE space probe at this site).

Despite the fact that it has had to revise its original timetable, the NEOP is still alive and well.  In a 2007 report to Congress, NASA refined the goal of the project to the mapping of all bodies larger than 140 meters across whose orbits pass within .05 AU of Earth’s orbit.  At that time, the date of completion was estimated to be 2020.

In its web page about the establishment of this organization, NASA points out that the detection of NEOs also has a possible good side.  We now know that comets and asteroids are rich in substances that will prove useful to future space exploration efforts.  One of the most important of these is water, which exists in frozen form on many of the small bodies of the solar system.  In addition to its obvious usefulness for human consumption, water can be processed to yield oxygen and hydrogen, which also have multiple uses.  Besides this, there may be metals and minerals on some of these bodies that can be mined by future explorers.

The United Nations started an organization in 2001 called Action Team-14, which is dedicated to international discussions of the NEO issue.

This is all good, but it does raise an obvious question: when we find a NEO that is clearly going to impact Earth, what can we do about it?  Bear in mind that if we just shoot a missile at the thing, it will only make matters worse by creating a multitude of smaller pieces, all of which would follow roughly the same path as the parent body.  That would be turning a cannonball into buckshot- not a good idea.

Recent scientific findings have shown just how likely such an outcome would be.  We now know that “rubble piles” are very common in the solar system- see the article at this site about Mars’ moon, Phobos.  These are groups of rocks that stick to each other because of their slight gravitation, but are not actually attached.  If nothing happens to separate these rocks, they might stay together for billions of years; but if something hits them and jostles them apart- say, a missile fired by foolish little germs on some nearby planet- then they could fly apart very easily, and the buckshot analogy would be quite appropriate.

In its 2007 report to Congress, NASA listed different techniques that might be used to deflect a NEO that is on a collision course with Earth, and assessed the potential effectiveness of each one.  Because of the rubble pile problem, they immediately dismissed any idea of detonating an explosive on or under the surface of the body.  However, the report did propose an alternative: bring a nuclear device close to the NEO- but not too close- and set it off.  The force of the blast would nudge the NEO into a different orbit, but if you positioned the explosion right, it might not blow the object to pieces.

What we do depends, to some extent, on how much time we have to get to know our intruder.  In a best-case scenario, we would spot the object some years before it was to make impact.  Then we would be able to send an unmanned probe to study the threatening object.  By transmitting a continuous radio signal during a flyby of the body, the probe would allow Earth-based scientists to measure the Doppler shift of the signal, and calculate the body’s mass.  This would give us a pretty good idea of whether we were dealing with a rubble pile or not.  (As we saw in our Phobos article, rubble pile objects tend to have very low gravity because so much of their interior is empty space.)  If it turns out that we are dealing with a solid body rather than a rubble pile, our troubles are over (almost).  NASA estimates that for such a body, the best approach would be to shoot a non-explosive impactor, or more likely a series of them, at the body and knock it into a new orbit like an oversized pool ball.

Various “slow push” techniques have been proposed.  One of these is to find another asteroid and modify its orbit so that it acts as a tugboat, pulling the threatening object into a new orbit.  Another idea is to put down a robot lander which would actually mine rock from the body and fire it off in high-velocity “bullets,” in effect turning the NEO into a rocket.  Another idea is to send a spacecraft to rendezvous with the NEO and spray-paint it with some coloring agent which would make one side brighter than the other, so that radiation from sun-heated material would provide a small thrust.

One particularly novel proposal has come from America’s Planetary Society: mirror bees.  These are small, unmanned craft that use mirrors to focus sunlight on the NEO, causing material to boil off and create jets which, if carefully positioned, could change its orbit.  Alternatively, they might use lasers rather than mirrors.

The 2007 Congressional report said that while slow push techniques would work in theory, they could only be used if we had plenty of warning, since they all involve getting spacecraft to the object and performing operations that would take some time to be effective.  If we only have short warning- which is likely, unfortunately- then a stand-off nuclear explosion is probably our best bet.

The report also pointed out that up to 80 percent of NEOs might be in orbits that could not be attained by current launch vehicles, which would mean that new launchers would need to be developed.  Even then, it would be necessary to use gravity-assist maneuvers to the fullest advantage to reach some of them.

So the bad news is, if it happens, we’re in big trouble.  The good news is, at least the governments and other institutions of the world are aware of the problem, and are trying to do something about it.  These discussions have yielded some good ideas, but now those ideas must be acted on.  Our planet has been pounded many times before, and each time, many species became extinct as a result.  If we are lucky, maybe it will be different next time.

Sources:

Lendroth, Susan: Press Release- “Saving Earth One Asteroid at a Time” at the website of the Planetary Society:  planetary.org/about/press/releases/2010/0212_Saving_Earth_One_Asteroid_at_a_Time.html

Alexander, Amir: “Project: Asteroids- the Potential Threat” at the website of the Planetary Society:  planetary.org/programs/projects/targetearth/20100213.html

Projects: “Mirror Bees: Planetary Defense” at the website of the Planetary Society:  planetary.org/programs/projects/mirrorbees/

Murrill, Mary Beth and Whalen, Mark: “JPL Will Establish Near-Earth boject Program Office for NASA” at the NASA website:  neo.jpl.nasa.gov/program/neo.html

“Near-Earth Object Survey and Deflection Analysis of Alternatives” (report to Congress, March 2007):  neo.jpl.nasa.gov/neo/report2007.html

Vredefort Crater entry at Wikipedia:  wikipedia.org/wiki/Vredefort_crater

The first object was spotted by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey. This project was set up by the United States Air Force, NASA and MIT’s Lincoln Laboratory with the aim of discovering and tracking near-Earth asteroids and it has had much success over the years. Observations are carried out by a pair of Ground Based Electro-Optical Deep Space Surveillance (GEODESS) telescopes which are located in Socorro, New Mexico. On January 6 the telescopes achieved their latest success when they observed a new object in the asteroid belt which is a region of the solar system located between the orbits of Mars and Jupiter. This new object was named P/2010 A2 and its appearance has caused some excitement in the astronomical community.

While it is not uncommon that a new object should be identified in the asteroid belt the unusual thing about P/2010 A2 is its appearance. Generally asteroids have a relatively circular orbit and are not volatile in nature. These show up as a speck of light on pictures taken from telescopes. Comets on the other hand tend to have an elliptical orbit around the Sun and exhibit a visible tail due to the effects of solar radiation on their nuclei. These tend to have a fuzzy appearance in pictures. The mystery with P2010 A2 is that it exhibits the traits of both an asteroid and a comet. While it has an orbit which is consistent with an asteroid the picture taken of the object appeared fuzzy which gives it the appearance of a comet. This came as a surprise in that comets do not normally reside in the asteroid belt and scientist have been working to come up with an explanation of why this should be.

Initial observations indicated that the aphelion (furthest distance from the Sun) of the object is only 2.6 Astronomical Units (AU). This would mean that it remains within the warmer inner regions of the asteroid belt where ice is less likely to form. The frost line is located at 2.7 AU and it is beyond this that more volatile ices are expected to form which are typical of a comet. With ice probably not forming on its surface, this has led to the theory that the unusual appearance may be as a result of a recent asteroid collision which exposed ice that had been originally trapped beneath the surface of the object. Melting of this ice and the resulting gas and dust which would be released would help to explain the tail of the object.

If this explanation is indeed true then it would be the first confirmed collision event between two asteroids. Although a similar event has probably occurred in the past, this would be the first time observations of the phenomenon had been made. Monitoring of the object is expected to continue in the near future to try and establish more details. Specialists hope that either the Hubble or Spitzer Space Telescopes can be brought to bear on the puzzle although this has yet to be confirmed.

In future another space telescope which may view the object is the WISE Telescope. This was launched into space at the end of 2009 and only a few weeks after the lens cover was removed from the instrument it is already starting to produce results. The official start of the WISE mission to map the entire night sky was January 14. However in tests prior to this the telescope showed why it will be an important part of detecting near-Earth asteroids in future. Two days before the official mission was to begin it was reported that WISE had already sighted its first asteroid. The sighting was confirmed by the University of Hawaii’s 2.2m visible light telescope and the asteroid was named 2010 SB78. Initial estimates indicate that the asteroid is around 1 kilometer in diameter and is currently at a distance of 158 million kilometers from Earth. It is not considered that the orbit of the asteroid will bring it near to Earth and while it is not considered to be a danger it will continue to be monitored.

With two new objects being discovered in a relatively short time period it is to be hoped that the pace at which asteroids are detected will accelerate in the future. The work of the many existing projects which detect and track near-Earth objects will be enhanced by the capabilities of the WISE telescope and this should mean our knowledge of asteroids in the vicinity of Earth should be greatly increased in the coming years.

When it was first identified in 2004 Apophis caused some concern as initial observations indicated a small chance that it would collide with Earth during its 2029 pass of the planet. At an estimated size of around 1000 feet this had the potential to be a serious impact event. However additional observations discounted the possibility of a collision in 2029 although they showed that the course of the asteroid could possibly take it through a gravitational keyhole at this time. These are small regions in space that can alter an asteroids course in such a way that on its subsequent pass it could collide with the Earth. If Apophis passed through such a region it was considered that it could set up an impact event in 2036.

This threat was taken seriously enough that Apophis remained on the Torino impact Hazard scale until 2006. This scale is a method of categorizing the potential danger of an asteroid and runs from 0 to 10. An asteroid classified with a 0 rating has a negligible chance of colliding with Earth while a classification of 10 means that a collision is certain. Asteroid Apophis was classified as a 4 for a short time although further study showed that it was unlikely that it would pass through a gravitational keyhole and it was subsequently downgraded to a 0.

However a number of scientists still consider that Apophis warrants further study to assess its threat. In 2008 the Planetary Society organized a competition to design a space probe which could be used to track the asteroid and awarded $50,000 in prize money to the winners. The European Space Agency, NASA and other research groups have also studied ways in which Apophis or other similar asteroids could be deflected from an Earth bound course.

The latest view of the threat that Apophis poses came from the Russian Space Agency at the end of December 2009. Anatoly Perminov currently heads this organization and in a radio interview he indicated that they were planning a meeting to discuss the possibility of a mission to Apophis. Although no detailed information was given, Perminov indicated that other agencies such as NASA and the Chinese and European Space Agencies may be invited to join any subsequent project that the Russian Space Agency plans. Whether this comes to fruition remains to be seen.

Whatever the outcome of the latest discussions regarding Apophis, it is generally accepted that at some point in the future an asteroid is likely to be found that is on a collision course with Earth. Recent advances in technology such as the WISE telescope and projects such as NASA’s Near-Earth Object Program are likely to identify many new asteroids in coming years. While the majority of these will pose no threat to Earth it cannot be discounted that a number of dangerous asteroids will be identified. Studying strategies for dealing with such a threat is best done as early as possible and while Apophis itself may not turn out to be dangerous it may help to spur agencies and research groups into taking action which could prove to be beneficial in the long run.

WISE was launched on a Delta rocket on December 14, and after a few weeks of prepping the satellite, NASA jettisoned the cover that had kept the sensitive instrument cold. Since WISE sees in the infrared, it could pick up its own heat, which would ruin the data being collected. To guard against this, it was cooled with frozen hydrogen and sealed in a vacuum container similar in principal to a Thermos bottle. Now that it is in orbit and without its cover, the vacuum of space will serve the same purpose, but even better. At the moment, the instruments on the satellite are being calibrated, and observations will begin shortly. WISE will spend eighteen months surveying the sky, at which time it should have exhausted its supply of internal coolant. At that time, the mission will be over.

What are some of the things that WISE might find? Scientists have high expectations. This mission will build on the findings of two earlier infrared missions, COBE and IRAS. To get an idea of how big an improvement WISE is over its predecessors, consider this: while IRAS, which went up in the 1980′s, had only 62 pixels in its cameras, each of WISE’s four cameras has over a million. With eyes like that, it should be able to see a lot.

You can get an idea of the kind of science that will be done with WISE by considering the things it can see. The wavelengths that the satellite can detect fall into four bands:

Band 1: 3.4 microns- This is a broad filter to detect stars and galaxies.

Band 2: 4.6 microns- This is radiation from things that are too cool to be stars, but have some internal heat- in other words, brown dwarfs.

Band 3: 12 microns- This is the wavelength at which asteroids radiate in the infrared.

Band 4: 22 microns- At this wavelength, relatively cold things will be revealed, such as the dust of star-forming regions.

WISE will orbit Earth from pole to pole, surveying strips of the sky with each passage. This will allow each spot in the sky to be imaged many times, and by comparing the images, NASA scientists will be able to detect any that show visible movement over a short period of time. By doing, this, they will identify asteroids within the solar system, most of which are in the main asteroid belt between Mars and Jupiter. This will give us our first really accurate map of the asteroids in our system.

In addition to these nearer objects, WISE will be able to pick up the faint warmth of brown dwarfs. As stated above, these are bodies that are almost massive enough to become stars, but not quite. They never achieve nuclear fusion, the fundamental characteristic of stars, but they do emit some infrared radiation. It is possible that one or more brown dwarfs exist close to the solar system, but have remained undetected before now. WISE will find these objects, if they’re out there, and should even be able to pick up the glow from any planets that orbit them. (There is no reason why a brown dwarf should not have planets, though it is unclear whether they could support life.)

It is also hoped that WISE will show us the brightest galaxies in the universe. In addition to the faint objects that it will detect, the telescope will pick up infrared radiation from brighter sources, such as galaxies bursting with the heat of trillions of suns. These ultraluminous infrared galaxies, or ULIRGs, are almost undetectable in visible light surveys, and may not have been found before.

Other things that WISE is expected to see include young stars and the discs of planetary debris that surround them, clusters of galaxies in the distant, early universe, and a detailed view of our own Milky Way galaxy. In doing this, it will give the best view yet of the evolution of stars, protoplanetary discs, galaxies and clusters of galaxies- in other words, the universe from the bottom up.

The WISE mission promises to be a gold mine, providing enough data to keep the worthy scientists of NASA working for years. Unfortunately, we will have to wait a little while to see any results. The WISE data will be released in two stages. A preliminary release is scheduled to take place six months after the end of the mission, or about 16 months after launch, and a final release is scheduled for 17 months after mission’s end, or about 27 months after launch.

Watch for future articles about WISE at this website.

Sources:

WISE mission page at NASA website: wise.ssl.berkeley.edu/

Ten Things You Should Know About WISE at website of the Jet Propulsion Laboratory: jpl.nasa.gov/wise/facts.cfm

WISE Overview at website of the Jet Propulsion Laboratory: jpl.nasa.gov/wise/overview.cfm

WISE public website: astro.ucla.edu/~wright/WISE/

Lakdawalla, Emily: WISE Guys, at the Planetary Society Blog, August 27, 2009: planetary.org/blog/article/00002070/

The WISE Telescope is the latest in a long line of instruments that have been launched into space as part of NASA’s Explorer Missions. The instrument was designed, fabricated and tested by the Space Dynamics Laboratory in Logan, Utah and includes a 16 inch diameter telescope and four infrared detectors.

It has been launched into an orbit 525 kilometers above the Earth and will circle the planet 15 times a day, during which it will capture images of the night sky on an infrared sensitive digital camera. An image will be captured every 11 seconds with each picture covering an area of the sky around 3 times the size of the moon.

The operational phase of the mission is planned to last for 10 months and during the first 6 months of this the telescope will scan and map the entire night sky. Each position in the sky will be mapped at least eight times during this process and following its completion the telescope will begin a second scan which will continue for the remainder of the mission. The second scan will be used to try and identify further objects in the night sky and also to check if any changes have occurred since the first scan.

The mission has a number of objectives which include finding and studying asteroids and comets in our solar system, identifying the nearest and coolest stars which are know as brown dwarfs and to find the most luminous galaxies in the universe. It is expected that the mission will capture the images of hundreds of millions of objects in the night sky and the sensitivity of the infrared equipment is such that it will discover many objects that have previously gone unseen.
The finds that the telescope will make closest to our own planet will be near-Earth objects such as asteroids and comets which have orbits that bring them close to us. It is expected that hundreds of previously undetected dark asteroids will be identified by the mission and this will help in the search for potentially dangerous near-Earth objects which may be on a collision course with our planet.

The mission will also identify most of the asteroids with a size of 3 kilometers or greater in the main asteroid belt of our solar system and by measuring the infrared light from these will provide a good estimate of the size distribution of the asteroid population. Scientists should be able to use this information to make an estimation of how often it is likely that the Earth will have an encounter with a potentially dangerous object. The data collected should also provide an insight into the composition of asteroids and give clues as to whether they are solid or more like giant snowballs. Both the size and composition of an asteroid are important in determining its threat to our planet. The information from the mission will therefore assist future studies of potentially dangerous asteroids and also help in formulating a strategy for any that are found to be heading towards Earth and need to be dealt with.

The WISE Telescope will also be sensitive enough to identify brown dwarfs which form like stars but do not pick up enough mass to ignite nuclear fusion at their cores. It is suspected that around 1000 of these objects lie within 25 light years of planet Earth and the telescope should be able to provide confirmation of this. It has also been speculated that WISE may identify a ninth planet in our own solar system. The pattern of comet orbits around the Sun suggest that there may be a giant gas planet on the outskirts of our solar system about 25,000 times as far from the Sun as planet Earth and if this is the case then WISE should be able to confirm its existence.

Other finds are expected to include millions of energetic galaxies which are known as ultra-luminous infrared galaxies, newborn stars and disks of planetary debris around young stars. The most interesting finds that the WISE Telescope makes will be followed up by other missions including the Hubble Space Telescope, the Spitzer Space Telescope and ground based observatories. Information from the mission will also be used to target interesting areas of the universe by the James Webb Space Telescope when it is launched in 2014.

Data from the mission will be released in two stages. A preliminary release is scheduled for 6 months after completion of the mission and the final release will follow on 11 months after this. The results will be eagerly awaited by the scientific community and hopefully the mission will be a stunning success, providing new and exciting information that will broaden our knowledge of the solar system and universe in which we live.

Many people may have missed the news but an asteroid was detected passing less than 9000 miles from the Earth on Friday 6 November and it was only 15 hours before this happened that the comet was actually detected. The asteroid was first picked up by researchers at the University of Arizona as part of their Catalina Sky Survey and following this was detected by the Minor Planet Centre in Cambridge Massachusetts. The asteroid was then picked up by the National Aeronautics and Space Administration (NASA) and its trajectory plotted.

The 23 foot wide asteroid has been christened 2009 VA and at its closest it was only 8700 miles from the Earth. This is 30 times closer than the Moon which lies approximately 250,000 miles from the Earth and it was the third closest approach of an asteroid ever recorded. However it is not considered that the asteroid would have made much of an impact and in actual fact it probably would have burned up in the Earth’s atmosphere long before it reached the ground.

However the more worrying aspect of the story is the fact that it was only detected 15 hours before it passed the Earth. This demonstrates that there are still objects out there that we know little about and shows how close they can approach before actually being detected. Although 2009 VA actually posed little threat, a larger asteroid could have potentially devastating consequences if it were to collide with planet Earth.

NASA was tasked by Congress with identifying at least 90% of the asteroids that are considered to pose a threat to our planet by 2020. They were assigned the task in 2005 and initially estimated there were around 20,000 dangerous comets and asteroids, with those that are 460 feet or greater in size being considered a risk. To date scientists have accurately located around 6000 of these and the scheme which is known as the Near-Earth Object Program continues.

However the passing of 2009 VA shows how difficult this task will be. For an asteroid to get so close to the Earth without being detected is not something that should be taken lightly. NASA monitored a 100 foot asteroid in March this year as it passed around 45,000 miles from the Earth. An asteroid of similar size crashed into planet Earth in 1908 although it landed in a remote part of Siberia. The impact however devastated an area 1,200 square miles in size and if such an object landed near an area of dense population there would be severe consequences.

The NASA project is therefore important and if an early warning of an imminent strike was given this could greatly reduce the human consequences involved. 2009 VA was a lesson that the task of identifying near earth comets and asteroids is not an easy one although the hunt will go on.

This meteor shower is one of the most showy and dazzling of them all in the northern hemisphere. For over a hundred and fifty years this event has been known to be very active displaying at least one streaking meteor every thirty seconds. In other past occurrences it created sixty meteors per hour. On the average, one hundred meteors per hour radiate throughout the sky. This is known as the Zenith Hourly Rate (ZHR).

The winter December sky will provide an excellent chance to experience the meteor event. Visibility will be enhanced by a new moon ensuring that zenith hour rate is seen. Originating from the Gemini constellation and scattering relatively slowly across the sky provides viewers a chance to see the trails with the unaided eye. These shooting star trails last a number of seconds and be seen in varying colors. In the northern latitudes it can be visible in the not-to-late evenings. This is perfect timing for star parties, astrophotography and even family viewing.
Discovery of the Geminids
Three astronomers all working independently in 1862 are credited for the discovery of the Geminids meteor shower. The first noted was R. P. Greg (England), secondly B. V. Marsh (United States.) and lastly A.C. Twining (United States). More sightings and reports came during 1863 and 1864.

It wasn’t until 1983 that the origin of the Geminids meteor shower was uncovered. Once again, three astronomers are given the credit. Two for identifying an asteroid and one for researching and associating the orbit to the meteor shower. Simon Green and John Davies identified the asteroid 3200 Phaethon. Fred Whipple noted the asteroid’s orbit and associated it to the meteor shower.

What is still a mystery about the Geminids meteor shower? Even though 3200 Phaethon has been identified as an asteroid, there is a possibility that it could be a dormant comet. The question arose when a photographic density study was conducted and the results proved to be less dense than asteroids.

Asteroid or comet, 3200 Phaethon has been officially linked to be the origin of the Geminids meteor shower. The meteor shower happens every December and this year gives us a great chance to watch.

The art/science of studying the stars was engaged by several ancient populations like Maya, Incas, Egyptians and Greeks, and soon grew in importance to the point where those who practiced it were highly regarded and respected in their own society. The reason for this is evident: this science could provide, even from its first, rudimentary structure, an explanation to phenomena strictly connected to their life, such as the alternating of day and night or the cycle of seasons, and provided an essential instrument for activities such as agriculture and navigation.

The history of Astronomy is in part — from its origins to the invention of the telescope by Galileo Galilei, in 1610 — also the history of astrology. In prehistoric ages, the most advanced tribes were familiar with the motion and trajectories of just a few, visible objects like the sun, the moon and some of the brightest stars. The most commonly cited example of such knowledge is the Stonehenge complex, residing in Great Britain, which is thought to have served as a monumental calendar.

Chinese astronomy was born before 2000 BC and is still cited nowadays for its great tradition of carefully, a-critic documentation. From the documents in our possession we know that in their time they were already aware of events such as the passage of comets, or even the explosion of a Supernova star.

A few civilizations in central America also reached astonishing results, but unfortunately they didn’t manage to share they knowledge with other populations. Maya and Inca tribes would often build pyramids and temples, which were devoted to the Gods of the Sky. Their religion was strictly related to the planet Venus and, based on estimations of its motions, they managed to create an incredibly precise astronomical calendar, finding out, among other things, that the planet would accomplish five complete orbital revolutions in the time span of exactly 584 days.

Babylonians soon showed exceptional knowledge in the matter of astronomy, which would later be inherited by Egyptians and Indians. In their case, the desire to perfect this science at all costs came, rather than an actual need, from skeptical reasons that linked the motion of stars and planets to good or bad luck (solar and lunar eclipses were thought to bring extremely bad luck, and this conception would persist until relatively recent times). Even lacking any sort of precise instrumentation, Babylonians managed to find out many things about the apparent motion of planets, basing their observation on the position of a few bright stars on the sky: they therefore discovered the orbital revolution time of many planets, among which Venus, Mars, Jupiter and Saturn, only mistaking by a few days, and reporting the results of their calculations on special tables, most of which are well-preserved and can still be seen now in astronomical museums.

Egyptians’ immense and astonishing knowledge regarding astronomy relies, once more, on their ability to forge precise calendars describing the motion of stars and planets. As their life cycle was strictly linked to that of the Nile river, astronomy was given a central role by this society from the very beginning. Around 3000 BC, Egyptians were already used to dividing their day and night time in regular intervals of 12 parts each: day time would be measured by sundials, while night time would be measured by observing the relative position of 24 bright stars. Measuring this way, their ‘hours’ would have a different duration depending on the season, but still averaging 60 minutes each.

It was only with Greek astronomy, though, that a stress was posed on developing theories that would explain the birth of the Universe and its mechanics: Anaximander thought the planet Earth was a cylinder at the center of the Universe, while the stars would rotate around it in all directions; Plato had at a first time a theory, extremely advanced for its time, that put the Sun at the center of the Universe, but he later withdrew it to favor an Earth-centric theory similar to that of Anaximander; Eudoxus of Cnidus, finally, advanced a theory that was later approved by Aristotle, according to which the Universe was made of concentric spheres, rotating one inside another, where the Earth would be in the center.

The Aristotle conception of the structure of the universe was meant to last, with minimal variations, until the year 1500 AD, when Nicolaus Copernicus — which many consider the father of modern astronomy — advanced a theory that put the Earth orbiting in perfect circles around the Sun, together with all the other planets: this approach could in fact solve many of the contradictions that those who supported Aristotle had to face. A few decades later, John Kepler refused yet another innovative model of the universe from his mentor Tycho Brahe, and later became famous for formulating the three laws of star mechanics that were named after him, which are considered valid still nowadays.

In 1610, Galileo Galilei invented the telescope, after a long period of research and experimentation. As soon as he pointed it at the stars, a never seen before universe appeared in front of his eyes: the Moon had a surface full of craters, Jupiter was surrounded by four satellites, while the Milky Way suddenly appeared as nothing but a huge mass of countless stars. In 1632, after publishing his book ‘Dialogo sopra i due massimi sistemi del mondo’ [On the main two models of the Universe] in which he was openly exposing the results of his observations, he was forced by the Catholic Church to abjure not having made those discoveries.

A few decades later, while researching innovative techniques to build more and more powerful telescopes, an important debate took place between the scientist Huygens and Newton over the nature of light: the first said it was a wave, while the second thought it was made of physical ‘atoms’ (photons). The debate that was destined to be solved once and for all just a few decades ago (light is, indeed, both a wave and a physical object). Huygens studied advanced optics as well, and managed to build a telescope that could noticeably minimize the chromatic aberration in observations, which led him to discover Saturn’s rings and its moon, Titanus.

Just a few years later, Cassini and Romer found out that phenomena such as solar eclipses would happen just several minutes after they were expected: this led them to think that light could actually travel at a finite although extremely high speed, rather than to an infinite speed: their estimation put the speed of light at 230,000 km per hour (the actual speed of light is 300,000 km/h).

Starting from the 19th century, following the Industrial Revolution, the continuous development of innovative techniques and instruments for the observation of the sky led to a series of discoveries that quickly contributed to our knowledge. Nowadays, the main purpose of astronomy is to study the life cycle of stars and galaxies, the origin and future of the Universe, obscure objects like pulsars and black holes, and methods to measure interstellar distances with increased precision.

This asteroid passing did not get a lot of media coverage, but it was definitely a close call to say the least. This type of activity in our solar system is just an example of how we could all go to sleep one night and not wake-up the next morning.

What interests us the most is that an amateur astronomer found this 40 yard sized asteroid and not one of the big telescopes. It is reported that about every 100 hundreds years we have a Tunguska asteroid hit. Below is a video on what happened when this small asteroid hit in Siberia:

source: http://news.bbc.co.uk/2/hi/science/nature/7921279.stm