A Hillsdale College pro­fessor and four Hillsdale grad­uates con­tributed to a study which revealed a signal found in data from the Arecibo and Green Bank Tele­scopes that may signify grav­i­ta­tional waves from the merging of two super­massive black holes.

Assistant Pro­fessor of Physics Timothy Dolch and stu­dents Cody Jessup ‘16, Daniel Halmrast ‘17, Joshua Ramette ‘17, and Michael Tripepi ‘17 worked with the North American Nanohertz Obser­vatory for Grav­i­ta­tional Waves, or NANOGrav, to watch and record pulsars — a type of star “pri­marily visible to radio tele­scopes,” Dolch said in an email.

“They are rapidly spinning, col­lapsed rem­nants of exploded stars,” Dolch wrote. “Com­bined with their radio beams, the spinning pro­duces a ‘light­house’ effect that makes the radio emission flash on and off or ‘pulse’ — hence the name. These pulsars are spread throughout our Milky Way galaxy.”

According to a Hillsdale College press release, “NANOGrav researchers studied the signals from distant pulsars. Pulsars were chosen because they are detectable and dependable, serving as a sort of galactic clock.”

NANOGrav has been watching 80 pulsars for the last 15 years and looking for “subtle changes in their pulse rates” that might be an indi­cation of grav­i­ta­tional waves, which, according to Dolch, are “ripples in the fabric of spacetime that probably come from merging super­massive black holes that are much more distant — far outside the Milky Way.” 

These were recorded using the Arecibo Obser­vatory in Puerto Rico and the Green Bank Tele­scope in West Vir­ginia. Radio tele­scopes are antennas designed to receive natural radio emis­sions from space. Radio waves cut through the earth’s atmos­phere, making them detectable with ground-based radio obser­va­tories. Arecibo was “the best instrument in the world for observing pulsars,” Dolch said.

“Until last December, the main instrument there was the 305‑m William E. Gordon tele­scope — the big dish that’s com­monly known as ‘Arecibo Obser­vatory,’ even though that’s tech­ni­cally the name of the facility housing it,” Dolch said. “You may have seen Arecibo in the movies “James Bond: Gold­eneye” and “Contact.” I’ve been there four times, and have even had the expe­rience of walking out on the catwalk to the hanging platform.”

Many Hillsdale stu­dents con­tributed more than 100 hours remotely from the Radio Tele­scope Remote Command Center in Hillsdale’s physics department. The four stu­dents co-authored two data pub­li­ca­tions with Dolch in the Astro­physical Journal Sup­plement Series, and Dolch wrote an addi­tional paper in the Astro­physical Journal Letters. 

Halmrast, now a graduate student at Uni­versity of Cal­i­fornia Santa Barbara, said the stu­dents’ obser­va­tions were used for the papers’ analyses, and they were only a small part of a very large project. He also had to do a sep­arate project in which he created a data set that observed the Arecibo waves for 24 hours.

“Instead of mea­sure­ments every two weeks over the course of ten years, it was mea­sured every hundred mil­liseconds over the course of 24 hours,” Halmrast said. “It’s a com­pletely dif­ferent data set. It requires dif­ferent types of analysis so you need to kind of rewrite the whole program, but it’s the same kind of spirit. You’re looking for some sort of wave signal.”

Jessup, now a physics graduate student at Montana State, said he ended up con­tributing approx­i­mately 180 hours to the project as part of his senior thesis.

“You can do it remotely. I basi­cally used my per­sonal com­puter,” Jessup said. “I con­nected to the com­puter down in Arecibo, and basi­cally con­trolled the tele­scope remotely from my computer.”

Unfor­tu­nately, Arecibo col­lapsed on Dec. 1, 2020, fol­lowing a cable breakage the pre­ceding August. 

“That was bad but not dis­as­trous,” Dolch said. “But that put addi­tional weight on the remaining cables. In November a cable snapped, leading to a cas­cading failure of other cables — in other words, to the col­lapse. Sadly, this hap­pened as the replacement cables were en route on a ship.”

There are several plans for replacement that are being dis­cussed. One is building a suc­cessor at the same site because the obser­vatory facility uti­lizes other smaller instru­ments, thus lending an already existing infra­structure. Other pro­posals advocate building new, pow­erful tele­scopes else­where. But in that case, Dolch noted, the advantage of plan­etary radar would be lost.

“The main thing that Arecibo did that no other facility in the world (existing or under con­struction) can do is plan­etary radar,” Dolch said, explaining that plan­etary radar is “sending” out radio waves and bouncing them off solar system objects and receiving the reflected signals back. “Much of what we know about Mercury and Venus orig­i­nally came from Arecibo’s radar work. Addi­tionally, it was really good at tracking near-Earth asteroids. It might be smart to con­tinue to have at least one tele­scope like that some­where on Earth!”