The Spitzer Telescope was the final mission of NASA’s Great Observatories Project which launched a family of four observatories into space. The most famous and well known of these is probably the Hubble Telescope and the program also included the Compton Gamma-Ray Observatory and the Chandra X-Ray Observatory.

The Spitzer Telescope was launched into space in August 2003. It was originally named the Space Infrared Telescope Facility and, in accordance with NASA tradition, was renamed the Spitzer Telescope following the successful demonstration of its operational capabilities. The telescope is 0.85m in size and three science instruments were also included as part of the mission. These included an Infrared Array Camera, an Infrared Spectrograph and a Multiband Imaging Photometer.

The telescope obtains images by detecting the infrared energy which is radiated by objects in space and this required that it be cooled to near absolute zero using liquid helium. With this requirement it was expected that the functional life of the telescope would be around 5 years. After this length of time it was expected that the liquid helium would become exhausted and the science instruments would be of no further use although the telescope itself would still be operational.

The event at the Adler Planetarium in Chicago demonstrated that the mission has been a great success. The image of the Milky Way the telescope has produced is one of the most stunning views of the galaxy that has ever been seen. To produce the final image data from two of the three onboard instruments was collected and processed by teams involved in the mission. These were the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) team which used data from the Infrared Array Camera and the Multiband Imaging Photometer for Spitzer Galactic Plane Survey Legacy (MIPSGAL) team which used data from the Multiband Imaging Photometer.

The image these teams created covers a huge area and was made by stitching together an incredible 800,000 individual pictures. The resulting masterpiece is 120 feet long by 3 feet wide at the sides and the width increases to 6 feet in the centre. It is the highest-resolution and largest image of the Milky Way ever created and shows the galaxy in stunning detail. The new image is detailed enough to show clusters of stars where previous pictures had shown only a single source of light. The leaders of the two teams involved in the work attended the event to unveil the image and they also gave short presentations about the work involved in creating it.

It is considered that the image is probably the best view we will have of the Milky Way for the foreseeable future. It will assist scientists studying the galaxy and should help them in better understanding some of the processes involved in its formation. The picture is to remain as a permanent exhibit at the Adler Planetarium and a trip to see it is definitely worth doing if you visit Chicago.

With this heightened telescopic acuity, there has been a flurry of research concerning a period of early galaxy formation known as the reionization epoch, a period that has remained largely a mystery up until now. A recent study by an American and Japanese team of astronomers led by Carnegie Observatory’s Masami Ouchi, has been able to precisely determine the age and distance of some of the universe’s oldest galaxies, and in doing so has answered a question that has been puzzling astronomers for ages.

The Big Bang, an event estimated to have occurred approximately 13.7 billion years ago, created a hot, chaotic soup of free-floating atomic particles. A mere 400,000 years later, the atomic particles combined to form neutral hydrogen molecules, or H₂. Sometime in the next 600,000 years, these neutral hydrogen molecules began to form enormous stars, which in turn emitted radiation and newly charged hydrogen ions, clearing the soup and allowing visible light to be emitted.

This much has been known for some time, but what has puzzled scientists up until very recently was how long, exactly, after the formation of the neutral hydrogen particles did reionization occur? Furthermore, when it did occur, did it happen suddenly, like the Big Bang itself? Or was it a gradual process, evolving over time?

Using the WFC3 as well as the Subaru telescope (from the National Astronomical Observatory of Japan) and the Spitzer telescope (out of California), researchers are able to calculate the specific wavelength of some of these earliest galaxies, which can then be used to calculate the galaxy’s distance and age. To do this, scientists view the distant stars through a progression of red light filters. As the filters increase in wavelength, or redness, distant stars will drop out of view, based on the wavelength of light they themselves are emitting. The last stars to drop out of view are determined to be the oldest stars, and as such are the stars of greatest interest to Ouchi and colleagues.

By examining density and brightness measurements, the team calculated that star formation and ionization rate was significantly lower from about 800 million to 1 billion years after the Big Bang than it was after that period. The low rate of ionization indicates that the reionization period must have started no less than 600 million years after the Big Bang.

The low rate of ionization during the period was the most unexpected finding, contradicting inferences made from previous studies.  This could be partially explained by a difference in the types of stars that were formed during the period”stars produced in the early galaxies were massive, containing up to 200 times more matter than our sun. These massive stars produced more ionizing photons than would a greater number of smaller stars, and thus might have given the illusion of a higher ionization rate.

A generation ago, this level of detailed research was the stuff of science fiction. Now, with technology advancing at an almost exponential rate, we can only imagine the possibilities that lie ahead.

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.