Herschel Space Observatory: A Window into the Chemistry of the Cold, Dark Universe
Over the past three years, the James Webb Space Telescope (JWST) has revealed in extraordinarily sharp detail the infrared universe. We’ve gotten a better view of newborn stars, distant galaxies, and even exoplanets than ever seen before. But before JWST turned its gaze skyward, another telescope revolutionized our understanding of chemistry in space. The Herschel Space Observatory (HSO), launched by the European Space Agency in 2009, was one of the first missions that allowed astrochemists to probe the far-IR field. Operating in wavelengths longer than JWST’s, Herschel was able to pierce into the coldest, darkest parts of the universe.
Herschel contributed to many key findings in astrochemistry, including:
1. Water in the Universe
Herschel mapped cold-water vapor in star-forming regions, protoplanetary disks, and comets. The WISH Program (Water in Star-Forming regions, with Herschel) showed that water is present even in the earliest stages of star formation (VanDishoeck+2011). Moreover, Herschel observations of the Jupiter-family comet 103P/Hartley 2 found ice with a similar composition to Earth’s oceans, supporting the idea that comets might have played a role in delivering water to Earth (Hartogh+2011).
2. Chemistry in Star-Forming Environments
Herschel also observed dark, dense gas in clouds with active star formation. It detected molecules like CO, OH+, NH, CH+, and H2O, showing that even cold environments, such as those powered by shocks and UV radiation due to forming stars (e.g. Aleman+2014, Nagy+2016), can be chemically rich when dynamically active.
3. Organic Chemistry in Space
It also detected organics in the far-off interstellar clouds and protostars (e.g., Neill+2014), which has helped us understand how complex molecules form in space.
4. Gas-Mass Reservoir in Planet-Forming Disks
Herschel detected HD (deuterated hydrogen) in protoplanetary disks for the first time (Bergin+2013). This simple-but-rare molecule helped constrain the amount of gas in protoplanetary disks, giving us insight into how much material is available for planet formation. To this day, this discovery helps scientists improve their computational models to study planet formation.
Although Herschel had a short life (2009 to 2013), it left a legacy of knowledge and data, laying the foundations for interpreting JWST’s findings. It highlighted how chemical signatures are essential tools for studying the physical conditions to help understand the evolution of star and planet formation, as well as interstellar clouds. No other mission since has had such a wide range of wavelength coverage. While there are currently no facilities that can observe the far-IR wavelengths, the field is preparing for next-generation far-IR missions, such as ASTHROS, a high-altitude balloon observatory, and PRIMA, a proposed space telescope for NASA’s next probe-class mission. These missions will allow scientists to build on Herschel’s legacy and probe even deeper into the darkest, coldest parts of our universe.
This article made use of the following publications:
Original Contributor
Amanda Alvarado-Torres
University of Virginia
Amanda Alvarado-Torres is a Ph.D. student in Astrochemistry at the University of Virginia. She holds a B.S. Chemistry and M.S. in Physical Chemistry from the University of Puerto Rico. Amanda’s current research combines computational models and spectroscopy to study gas is distributed in planet forming environments. Previous to this, she studied the formation of water molecules in star-forming enviroments. She’s very passionate about astronomy outreach and education, especially making the wonders of the universe accessible to all. Outside of astronomy, she loves gardening and spending time with her dog, Laika.
Editor
Annika Geiger
The Astrochemistry Report
