四虎影院

An astrophysics major, rising senior Melanie Ficarra and her student team search the starry skies for 鈥渃osmic clocks,鈥� part of an international consortium鈥檚 research project that this week reported evidence of gravitational waves that oscillate periodically from years to decades.

鈥淢y research involves identifying pulsars using data that has been collected using several large radio telescopes,鈥� she says. 鈥淲e follow certain criteria to determine if each candidate signal is a possible pulsar or not.鈥�

Ficarra is among hundreds of students nationally and internationally who for the last decade have worked on pulsar and gravitational wave research, many of them with F&M Astrophysics Professor Fronefield Crawford, who manages  NANOGrav Student Teams of Astrophysics Researchers () program.  

Crawford is part of the team of astrophysicists from the United States and Canada who found  evidence for periodically oscillating gravitational waves, according to a set of papers published this week in .

鈥淏y detecting and characterizing these kinds of signals, we鈥檙e really opening up a new window into studying and understanding the objects that are producing those signals, how they evolve, and how they connect to the evolution of the universe as a whole,鈥� Crawford says.

The team, using large radio telescopes directed toward a collection of cosmic clocks in the Milky Way galaxy, observed signals in 15 years of data acquired by the , a collaboration of more than 190 scientists who use pulsars to search for gravitational waves. 

鈥淭he basic idea is that we use a collection of radio pulsars in our galaxy that act as extremely precise clocks, and by monitoring these pulsars over time, we are sensitive to the presence of weak gravitational waves,鈥� the Charles A. Dana Professor of Physics and Astronomy and director of F&M鈥檚 Grundy Observatory says.

While NANOGrav鈥檚 earlier results uncovered an enigmatic timing signal common to the pulsars they observed, it was too faint to reveal its origin. The 15-year data release demonstrates that the signal is consistent with slowly undulating gravitational waves passing through our galaxy.

鈥淭his is the first evidence for gravitational waves at very low frequencies,鈥� says Vanderbilt University鈥檚 Stephen Taylor, who co-led the search and is the current chair of the collaboration. 

Astronomers turned the Earth鈥檚 sector of the Milky Way galaxy into a huge gravitational-wave antenna by using pulsars. NANOGrav鈥檚 15-year effort collected data from 68 pulsars to form a type of detector called a pulsar timing array.

A pulsar is the ultradense remnant of a massive star's core following its demise in a supernova explosion. Pulsars spin rapidly, sweeping beams of radio waves through space so that they appear to 鈥減ulse鈥� when seen from Earth. The fastest, called millisecond pulsars, spin hundreds of times a second. Their stable pulses make them useful as precise cosmic timepieces. 

鈥淥ur approach is a bit unusual: In a typical scientific experiment, you would build a detector to detect a signal, and then you would run an experiment by collecting some data and making some measurements,鈥� Crawford says. 鈥淗ere, instead of building a physical detector, we鈥檙e finding new pulsars in our galaxy that act as our gravitational wave detector.

With more than 15 years of observations with the Arecibo Observatory in Puerto Rico, the Green Bank Telescope in West Virginia, and the Very Large Array in New Mexico, NANOGrav has gradually expanded the number of pulsars they observe. 

"NANOStars was my first research opportunity at F&M, and it was a great program to start astronomy research.鈥�

鈥� Melanie Ficarra

For the F&M students鈥� research in determining pulsars, Ficarra says her team used a program that a fellow team leader, rising senior Wenky Xia, 鈥渨rote to make this process more efficient.鈥� 

鈥淲e meet as a group every week to discuss our progress and attend teleconferences every few weeks to connect with other colleges and universities working with NANOGrav,鈥� says Ficarra, who plans to pursue a doctorate. 鈥淣ANOStars was my first research opportunity at F&M, and it was a great program to start astronomy research.鈥� 

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