ESA’s Herschel Space Telescope Is Off to a Great Start

On May 14, 2009, the European Space Agency launched two revolutionary space telescopes aboard the same launcher.  These were Planck and Herschel, new eyes on the universe which will hopefully revolutionize our view of the galaxy and beyond.   The dual launch was a cost-saving measure, but the two missions do have one thing in common: they give us a view of the universe in wavelengths that are invisible to our eyes, and which reveal things that visible light does not.  In our article a few weeks ago, we took a look at Planck and its mission; this time we will look at Herschel.

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