Herschel is a tall cylinder, about 7.5 m tall and 4 m wide.  Its launch weight was 3.4 tons, and the telescope itself weighs 315 kg.  It is orbiting the sun at the L2 point, just beyond the orbit of Earth.  In this position, the sensitive instruments are in Earth’s shadow, which will protect them from the heat of the sun, and far enough from the Earth and the moon to avoid their interference, too.  Its lifetime was originally projected to be 3.5 years, but as we have seen with other probes, this may be extended.

At 3.5 meters in diameter, Herschels’ main mirror is more than four times as large as any previous infrared telescope.  It will capture almost 20 times more light than any of its predecessors.

Herschel is part of a larger movement toward multi-wavelength astronomy.  The sad truth is that we humans are almost blind.  Most of the energy in the universe is completely invisible to our eyes.  If you look at a chart of the electromagnetic spectrum, you can see that visible light is only a tiny sliver of the whole range of wavelengths.  Some phenomena emit very little in this range, concentrating most of their emissions in parts of the spectrum that we can’t see: X-rays, infrared, radio waves etc.  If we are only looking at visible light, we are only seeing a small part of what’s really going on in the universe.  To remedy this situation, we have invented new eyes that can see in those other wavelengths, and launched them into space.  Above the murky atmosphere, they can show us things we’ve never seen before.

Granted, this line of research is not new.  Astronomy in the X-ray, radio wave and infrared regions of the spectrum has been around for a while, and has already given us new views of some objects.  But the new wave of space telescopes, of which Herschel is one of the pioneers, will greatly expand the range of wavelengths being observed, and will be capable of studying many more targets than previous missions.  For the first time, we will at least be getting close to a complete view of the universe around us.

For example, Herschel is the first observatory to cover the entire range from far-infrared to sub-millimeter wavelengths and bridge the two.  It will observe further into the far-infrared than any other mission, studying the dusty regions of the cosmos, both near and far.  Many of the wavelengths that Herschel can see have not been exploited so far, so the things revealed there will be completely new.

Herschel’s work will be conducted all the way from the local level to the intergalactic level:

Within the solar system, the telescope will study asteroids, Kuiper belt objects and comets.  All of these objects absorb solar radiation and then emit it in the infrared, and their emissions carry information about the emitting body.  (In this, Herschel is taking part in a larger drive to gain greater understanding of the small bodies of the solar system- see our articles on the Dawn probe and the Hayabusa asteroid mission.)

On a larger level, but still within our Milky Way galaxy, Herschel will turn its attention to the star-forming regions, to reveal different stages of early star formation and observe the youngest stars in our galaxy for the first time.   Herschel will also be able to study the dust clouds and accretion rings around stars, the very things that make planets.  By doing this, it is hoped that Herschel will be able to study the birth and evolution of planets in unprecedented detail.

Expanding its view still more, Herschel will look at the vast reservoirs of dust and gas in the Milky Way and in other galaxies, conducting astrochemical analysis which will hopefully give us new insight into the complex chemistry of these dust clouds.

Herschel will allow us to expand our perspective.  So far, most of our science about interstellar physics and chemistry has been learned from observing our own galaxy.  This is very limiting, since different galaxies have different chemistries.  For the first time, Herschel will allow us to conduct observations of other galaxies, some of which are very different from our own.  For instance, some galaxies have much lower amounts of metal than the Milky Way does.  Any stars and planets that formed in those galaxies would be very bizarre from our point of view, having few if any of the metals that form such an essential part of all kinds of chemistry in our world.  (Creatures like us, with our iron-rich blood, would not even exist.)  By studying such galaxies, Herschel will finally expand our knowledge of interstellar chemistry and physics beyond our own neighborhood.

Moving to a still larger level, Herschel will be able to look far back in cosmic time, to a period when star formation was happening at a much higher rate than it is today.  The star formation occurring now is really just the aftermath of this burst, which happened when the universe was about half its current age.  With Herschel as our time machine, we will be able to see this period and study it in new detail.

Herschel will also conduct studies of the cosmic infrared background, a function which complements the mission of Herschel’s launch mate, the Planck space telescope.

This is heavy stuff: the processes that made the galaxies, stars and planets.  It is cosmic science, in the truest sense.  It was just a few years ago that the science of cosmology was largely a matter of theory.  We thought we knew how the universe had come to be, but we had no way of checking our theories for accuracy.  Now, with Herschel and its breed, we can fill in some of the blanks in our knowledge.

Besides that, Herschel’s work closer to home will also show us some interesting things.  The dust clouds that it will pierce have been opaque to us until now, and for the first time, we will see what is within them.  Closer still, Herschel will contribute to our knowledge about the composition and structure of asteroids and comets.  This will be really interesting, but it may also help us out in the future.  If one of those objects is detected heading for Earth, it will be nice to know something about it- and Herschel may help to provide some of that knowledge, either by studying that body specifically or by providing us with general information about the characteristics of such objects.

All that is in the future, but Herschel is in operation right now, and is already proving its worth.  It opened its “eyes” and took a test image on June 19, 2009, and ESA proudly released the picture to the press: an absolutely beautiful shot of the spiral galaxy MS1, which will undoubtedly grace many calendars and posters for years to come.  It looks like a piece of exotic jewelry, a swirl of eye-popping blue, yellow, pink and white against the blackness of intergalactic space.

Since then, Herschel has performed even better than expected.  For its first assignments, it was trained on more galaxies, star-forming regions and dying stars.  It provided spectacular data from the start, finding water and carbon and revealing dozens of new galaxies.

ESA has already started compiling a picture gallery of images Herschel has taken.  The latest of these just came in a few days ago: the star-forming region in the Rosette molecular cloud, revealing a previously unseen cluster of stars roughly ten times the mass of our sun.  This is another stunner: swirls of blue, gold and red, set with stars like diamonds.  Wow!  The guys who do screen savers will go crazy over this stuff.

We’re going to see lots more from Herschel in the years to come.  You can read about it here- and the picture gallery at the ESA website is highly recommended.

Sources:

“Herschel at a Glance” at the website of the European Space Agency:  esa.int/SPECIALS/Herschel/SEMBM00YUFF_0.html

“ESA Herschel: Science Objectives” at website of the European Space Agency:

esa.int/SPECIALS/Herschel/SEMSN00YUFF_0.html

“Herschel Highlights” at the website of the European Space Agency:  esa.int/SPECIALS/Herschel/SEMEN00YUFF_0.html

“ESA Herschel: Vital Stats” at website of the European Space Agency: http://www.esa.int/SPECIALS/Herschel/SEM4T00YUFF_0.html

ESA News: “Herschel’s Daring Test: a Glimpse of Things to Come” at website of the european Space Agency:  esa.int/SPECIALS/Herschel/SEM76A0P0WF_0.html

ESA News: “Baby Stars in the Rosette Cloud” at the website of the European Space Agency:  esa.int/SPECIALS/Herschel/SEMWQ59MT7G_0.html

In addition to this, Planck is also undertaking a few other observations of nearer things, such as parts of our own Milky Way galaxy.  As the most sensitive instrument of its kind, it can see things with a greater clarity, resolution and range of wavelengths than ever before, and scientists have several targets selected for it.

The rocket that took Planck into space was an Ariane 5, the ESA’s standard launch vehicle.  The launch took place on May 14, 2009, from the ESA spaceport in Kourou, French Guiana.  As a cost-saving measure, Planck was launched along with another probe, the Herschel infrared observatory.  These two probes separated from their launcher soon after reaching space.  Both of them were sent on a course that would eventually lead them to the second Lagrangian point (L2), situated about 1.5 million km. from Earth in the opposite direction from the sun.

These two probes will operate independently of each other, but the science they  do will be complementary.  The Herschel infrared observatory is also an interesting subject, and will be examined further in a future article at this site.  For now, we will concentrate on Planck.

The Planck satellite weighed about 1900 kg. at launch, and has a boxy shape about 4.2 meters on a side.  It is equipped with a 1.5-meter-wide mirror which focuses radiation from the sky and sends it to two detectors known as the Low Frequency Instrument and the High Frequency Instrument.

The Low Frequency Instrument (LFI) performs observations of the microwave sky in the range of frequencies from 27 to 77 GHz.  It is composed of 22 tuned radio receivers which work like the transistors in a radio, amplifying the signal and converting it into a voltage.  The High Frequency Instrument (HFI) performs observations in the range from 84 GHz to 1 THz.  It has 52 bolometric detectors , devices capable of measuring very small amounts of heat energy.  The results from these two instruments are complementary, and go together to form the total mission results.

The instruments are very sensitive to heat, and the probe’s designers had to include a cooling system and various other measures to ensure a stable, low temperature.  In fact, the reason why Planck orbits the sun at the L2 point, rather than orbiting Earth, is that both Earth and the moon give off too much heat.  Planck had to get some distance away from them, or their heat would have spoiled the observations.

Planck is equipped with its own thrusters, and these were used for three course correction maneuvers.  The third of these maneuvers took place on July 2, and injected the probe into its orbit around the L2 point.

Because of the temperature constraint, it was necessary to put the probe through a cooling process before it could go into operation.  The instruments hit their lowest temperature, 0.1K above absolute zero, in the first week of July.  During the cooling period, all of the satellite’s subsystems were also turned on and tested.

Planck was designed to give answers to some of the most fundamental questions in cosmology: how did the universe begin, how did it evolve to the state that it is in today, and how will it evolve in the future?  The Cosmic  Microwave Background  carries information about the processes that took place in those early moments of existence, and by analyzing it, scientists can look through a window in time, to the moment right after creation.

This information takes the form of tiny temperature fluctuations in the CMB, about a millionth of one degree.  This is the equivalent of detecting the body heat of a rabbit sitting on the moon from Earth.

Planck’s first task was the First Light Survey, which was really just a chance to check the sensitivity of the instruments and make sure they could perform as expected.  The scientists were delighted to find that the quality of the data was excellent.

Since then, Planck has been working on its first All-Sky Survey.  This began in mid-August 2009, and is being completed now.  As of mid-March 2010, 98% of the sky had been observed by Planck, and 100% sky coverage is expected by late May 2010.

However, before the raw data can be turned into sky maps of the CMB, it will require a lot of delicate adjustments and careful analysis.  About two years will be need to refine the information and obtain the scientific results.  Even then, the resulting maps will provide decades of work for cosmologists and astrophysicists as they continue to study and analyze them.

One of the things they’ll be looking for will be confirmation of the current theory of how the universe formed.  This is one of those sticky moments in science when the scientific authorities have a theory that explains everything beautifully, but they don’t have a shred of evidence to support it- or to disprove it, for that matter.  The theory is called the inflation model, and the condensed version runs something like this:

(What came before the Big Bang, we have no idea.  All of our theories of the evolution of the universe deal with what happened after that event, and if anything came earlier, we probably will never know about it.)

The universe begins as an extremely small point.  During the first millionth of a second of its existence, it rapidly expands, or “inflates.”  After this initial burst of expansion, it continues to grow at a slower rate, and as it grows, the thermal energy which it contains becomes spread out over a larger area.  This means that the universe cools as it expands.

When the temperature of the universe drops to 1000 GeV (about 10 million million degrees) the natural forces appear: gravity, electromagnetism, and the strong and weak nuclear forces.  Quarks, the things that will form matter, appear and wander freely through the universe. As the universe keeps cooling, these quarks will eventually combine to form protons and neutrons, but it will still be too hot for them to capture electrons and make real elements.  Since electrons aren’t being captured to form atoms, they are free to interact with photons (light particles).  Because of this, a photon can’t travel very far without encountering an electron, and light does not propagate freely.  Because of this, the universe is dark.   It is only after 300,000 years that the universe cools enough to allow protons to capture electrons and form hydrogen atoms, which finally allows light to propagate freely. Light comes to the universe, and that first burst of light is the Cosmic Microwave Background.

Matter begins to form clots due to gravity, and as these clots grow, the universe takes on a more familiar appearance.  Stars form, and these form galaxies.

Fast-forward to today, and we see around us a universe filled with structures.  Galaxies form clusters, clusters form sheets and streamers spanning vast distances.  Where did all the structure come from?  If the universe all expanded out of one tiny point, why isn’t it uniform?  Why is matter gathered in some areas, while it seems to be more diffuse in other places?

The inflation theory explains the elaborate structures in the universe, which result from an uneven distribution of matter, by saying that they are the expansion of tiny variations in the original point from which it all expanded, and the expansion happened so suddenly that those variations were preserved, in vastly greater size, as the unevenness of matter in the universe today.

In other words, there has always been an unevenness in the distribution of matter and energy (as well as dark matter and dark energy).  This goes all the way back to the first instant of expansion, and since the CMB comes from close to the first moment (300,000 years is not very long in universal terms) it should have this unevenness, too.  It should also carry various other information from that early time, which Planck’s instruments can coax from it.  As a snapshot of the universe at a young age, it should have things to tell us about how the universe started, and how it got like it is today.

These are the kind of cosmic questions that Planck was designed to address.  Along the way, it will also do some viewing closer to home.  In fact, just a few days ago, the ESA released spectacular pictures taken by Planck showing filaments of cold dust only a few hundred lightyears away.  In addition to its work relating to the CMB, Planck will be doing studies of this nature, investigating structure and evolution on a galactic scale.

Planck is just getting started, and the clarity and resolution of the data so far promises great things for the future.  The questions that it addresses are of the most fundamental nature: how did it all begin, and how did it get like it is now?  You can’t get more cosmic than that.

As new data comes in from Planck, you can find it here.

Sources:

ESA Space Science: Planck Overview at website of European Space Agency:  esa.int/esaSC/120398_index_0_m.html

ESA Planck homepage at website of European Space Agency:  esa.int/SPECIALS/Planck/index.html

“Planck at a Glance: ESA’s Microwave Observatory” at website of European Space Agency:  esa.int/SPECIALS/Planck/SEMWN20YUFF_0.html

ESA Planck: Science Objectives at website of European Space Agency:  esa.int/SPECIALS/Planck/SEM0P20YUFF_0.html

ESA Planck: Planck Highlights at website of European Space Agency:  esa.int/SPECIALS/Planck/SEMKO20YUFF_0.html

ESA Planck: Instruments at website of European Space Agecny:  esa.int/SPECIALS/Planck/SEMBU20YUFF_0.html

ESA Planck: Launch and Early Operations at website of European Space Agency:  esa.int/SPECIALS/Planck/SEMB030YUFF_0.html

ESA Science and Technology: Planck at website of European Space Agency:  sci.esa.int/science-e/www/area/index.cfm?fareaid=17

ESA News: “Planck Sees Tapestry of Cold Dust” at website of European Space Agency:  esa.int/esaCP/SEMMN9CKP6G_index_0.html

ESA Space Science: “So How Everything Start?— a Timeline for the Universe” at website of European Space Agency:  esa.int/esaSC/SEMC6TS1VED_index_0.html