Dr. Christopher Groppi: Astrophysics with Scientific Balloons in Antarctica

By Alex Nachman

South Mountain Astronomy Club had an amazing guest speaker from Arizona State University for the month of August! Our guest lecturer was Dr. Christopher Groppi and his presentation was entitled, “Astrophysics with Scientific Balloons in Antarctica.” Chris is an associate professor at ASU who works in the School of Earth and Space Exploration. His research mainly involves designing and building radio telescope receivers for studying star formation in our own galaxy. His specialties include astronomical instrumentation, star formation, terahertz remote sensoring and micromachining.

Stars are formed in clouds of dust and gas that have formed from the interstellar medium. Because these clouds are often opaque and block most of the light shining from a protostar (newborn star), optical telescopes cannot “see” them very well. But infrared and radio telescopes, which operate on a different wavelength of light, can “see” these stars very well. Gas clouds that birth stars are known as diffuse nebulae. One such nebula is the Orion Nebula, which is the closest nebula to Earth and can be seen with the naked eye.

Orion Nebula imaged from the Hubble Telescope

Chris also does research with high altitude balloons in Antarctica. He has been developing new technologies to enable this sort of research with cubesats, and coming up with ways to use techniques and technologies we’ve developed for astrophysics for Earth science. Balloons are used in astronomical research to answer a myriad of questions, whether its about our atmosphere, the Sun or space-related.

NASA research balloon

NASA currently works with two balloon types, zero-pressure balloons and super-pressure balloons. Zero-pressure balloons are used for shorter flights and super-pressure balloons are used for longer flights. Both types of balloons are made out of polyethylene. This material is also the one used in plastic bags and is about the thickness of a sandwich bag. Although the plastic is thin, a large balloon can hold up to as much as 8000 lbs! There are also different ways a balloon can be used, whether it is conventional, long duration, or ultra-long duration.

Dr. Groppi’s presentation was absolutely wonderful and was full of exciting knowledge. Nebulae are the birth places of stars, but we cannot see stars with visible light, so in order to figure out what is happening with these stars, a different wavelength of light has to be used. Dr. Groppi talked about how they use a wavelength that is in the microwave spectrum of light. This wavelength of light is able to penetrate through the dense clouds of dust in these nebulae and be captured by their telescope. These dense clouds of dust block forming stars from view and as such only a much weaker wavelength of light is able to slip through. Thus, their telescope has to be very sensitive. A balloon is able to lift high into the atmosphere and escape most of the atmosphere molecules that would block these waves from the telescope. The atmosphere contains many particles and molecules that deflect microwaves but by using a balloon, data can be gathered without actually having to launch the telescope into space.

His research team works in collaboration with many groups around the world, including one down in Tucson at the University of Arizona. It is being funded by a NASA grant and his team will be building part of the telescope. Each team contributing to this project will contribute a part of the telescope. They are building a telescope that is able to detect this microwave-length of light and thus gather data on what is going on in these “hidden” areas. They are currently working on mapping out a huge chunk of our galaxy. Answers gathered from this data will explain how not only stars are formed, but entire galaxies as well.

The balloon they use to hold their 5,000 pound telescope is about 450 feet across, which is the length of the Chase baseball field. Not only is this balloon as long as the baseball field, but fully inflated, it would also fill up the stadium! The balloon is made from a very thin plastic, the same kind that is used in a grocery store bag and has the same thickness! Their upcoming mission will be about 3-3.5 months in duration and study star and galaxy formation.

For more information about balloons, there are some awesome links to check out!

https://www.nsbf.nasa.gov/balloons.html

https://sites.wff.nasa.gov/code820/

If you are interested in checking out his research, his articles can be found here: https://scholar.google.com/citations?user=ToXmtF0AAAAJ&hl=en