A comet that began its journey across our solar system more than a million years ago zoomed past Mars Sunday (Oct. 19). From Earth, observers in the southern hemisphere had the best vantage points of the icy ball hurtling through space, but its path didn’t escape the watch of three West Virginia University students.
WVU physics and astronomy graduate students William Armentrout and Brittany Johnstone and undergraduate student Virginia Cunningham observed the Comet Siding Spring (Comet C/2013 A) as it traveled the solar system at speeds as high as 126,000 miles per hour.
The comet was born in the Oort Cloud at the dawn of our solar system 4.6 billion years ago. Located in the remote reaches of our solar system, this spherical cloud of dust and debris is the home to trillions of icy bodies. Comet Siding Spring was jolted out of its orbit by a passing star or other interaction and sent on a million-year odyssey around the sun.
The comet passed within 87,000 miles of Mars, 10 times closer than any known comet has come to Earth in recorded history. The two were so close that the Red Planet was engulfed in the icy dust and gas molecules contained in the gaseous coma, the comet’s “long-haired” tail.
“This type of interaction between a planet and a comet is rare,” Johnstone explained. “This is the first time we’ll be able to see a planet transit through a coma. We are excited to see what affect it will have on the Mars and its atmosphere.”
“The most famous comet is Halley’s Comet,” Armentrout said. “It nears Earth every 75 years, so consider the significance of a comet that not only will come in such close proximity of a planet, but one that won’t return for several lifetimes.”
Through funding provided by WVU’s partnership with the Robert C. Byrd Green Bank Telescope – the largest, fully steerable single-dish radio telescope in the world – the team of students planned three observations of the comet and Mars during October.
Specifically, the team observed spectral lines, which emit at specific energy wavelengths, acting as fingerprints that identify elements present in cosmic bodies.
“The radio wave frequency that we are looking at will show us the presence of hydroxide ions (OH−),” Armentrout explained. “The Martian atmosphere contains mostly carbon dioxide, and its lack of a magnetic field allows particles such as hydrogen to easily escape. Any traces of hydrogen during our observations will likely have been deposited by the comet.”
“It is widely believed that most of the water and amino acids on our planet – the building blocks of life – were delivered by comets and asteroids,” he said. “Siding Spring could provide a snapshot of what was going on during the creation of our solar system and our planet.”
Scientists from all over the world observed the event to record the composition and structure of Siding Spring. They hoped to learn more about how the planets formed millions of years ago. They also hoped to learn how the comet interfaced with the Martian atmosphere as well as technology on the ground.
“We were interested in an event that we knew other scientists would also be watching, but we wanted to do it in the radio astronomy regime,” said Johnstone. “To our knowledge, no one was conducting a similar observation.”
As a young boy in Pennsylvania, Armentrout had a keen interest in stars and planets. “I received telescopes and binoculars as birthday presents,” he remembers. Similarly, Johnstone grew up in rural Pennsylvania looking up at the night sky with curiosity.
“From a very early age I was interested in astronomy,” Armentrout said. “But it wasn’t until I came to WVU that I gained experience in radio astronomy. The University’s partnership with the Green Bank Telescope provided a valuable hands-on learning opportunity.”
“Radio telescopes are amazing because not only are we able to detect celestial objects and structures that are millions of miles away, but we are able to see further back in time than with any other instrument,” he continued. “We can see millions and billions of years back to when the universe formed. It helps us answer the basic – and difficult – questions of why our universe is the way it is.”
Cunningham, who was first introduced to physics and astronomy while at WVU, said the field is unique because “it applies many areas of science beyond physics and astronomy, such as geology, chemistry and biology.”
The trio works in assistant professor of physics Loren Anderson’s research group. Their third and last observation is on Oct. 26 and will be followed by several weeks of analysis. While they pore over data from the telescope, Siding Spring will continue on its route back into the nether regions of space until it returns in another million years.
CONTACT: Devon Copeland, Eberly College of Arts and Sciences
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