Cute black hole

Cute black hole

Black holes seem fake, but they’re actually real, visible, and somewhat understandable, thanks to scientists, large telescopes, and lots of math. Bwogger Nadra Rahman attended a biweekly “Stargazing and Lecture series” given by graduate student Shuo Zhang last night in Pupin, titled “Our Monster Black Hole.” Nadra lived to tell the tale (and dish some cool info).

Despite the cold, rain, and an overwhelming sense of doom as the shadow of Hurricane Joaquin loomed above us, the lecture room in Pupin was packed by 8 pm yesterday evening. The first announcement of the night, however, was a disappointing one: because of the rain, stargazing would be canceled. Instead, attendees were welcome to view the 3D AstroWall or hear an additional talk regarding recent developments on Mars.

After this announcement, graduate student Shuo Zhang launched into her presentation on Sagittarius A*, the supermassive black hole found in the center of the Milky Way. Zhang has used X-ray telescopes to study black holes for years, and pointed out that the discovery of Sagittarius A* as a black hole is a relatively recent one. Though scientists knew it was a bright radio source in 1974, it was not until 1995 and the development of new techniques that they knew for sure it was a supermassive black hole.

Scientists defined its borders and mass by studying the orbitals and positions of stars that circled the body. The best evidence for supporting its status as a supermassive black hole is the fact that it is a huge, enclosed mass (4.6 million times the mass of our Sun!).

Zhang revealed that the space around a black hole can be seen: stellar debris form a band of spinning matter around the black hole, creating a structure she termed “beast-like.” Additionally, the particles that form the band release powerful X- and gamma rays as they collide with one another.

This led to the idea of flares, the times when a black hole emits a large burst of X-rays and in the process, brightens up enormously, recalling the visual of fireworks. Zhang pointed out that Sagittarius A* is primarily in a “quiet state punctuated by some flaring activity.” Since she began monitoring black holes in 2012, Zhang has detected nine flares, each varying in duration and structure. She presented two theories as to why the flares occur: one involving the tearing apart of asteroids, and the other involving the reconfiguration of magnetic field lines around the black hole.

During a flare, the black hole becomes “one hundred times brighter than its normal state” as great emissions go into gas clouds and are reflected and reprocessed, finally visible on Earth. Giant outbursts can lead to brightness over a million times greater than the usual state, as Zhang demonstrated by bringing up the Fermi bubble, a bubble-like structure made up of X-ray and gamma ray emissions; it dates back three million years and could indicate a major eruption of Sagittarius A*. This points to a general trend for Sagittarius A*, which was “much more active and furious in the past.” Over time, it has calmed down.

In talking about future flares, Zhang said there is uncertainty, but stated, “We hope to see something interesting in the future.”

In the Q&A that followed, the speaker discussed how the study of this black hole could inform the study of others, theorizing that “maybe they are in different stages of evolution.” She also further discussed the Fermi bubble and the implications for life on Earth (perhaps life would be different if our supermassive black hole had been more active). She ended by reiterating her earlier statement that the discovery is fairly recent, and pointed out that it was still an “open question” as to how Sagittarius A* would help us learn more about our universe.

Because stargazing was canceled, the audience then moved on to the 3D AstroWall. Donning 3D glasses, we viewed a bizarre and slightly terrifying short film about the Sun and its future dimming. The Australian narrator lent a tone of surrealism to the proceedings, and someone whispered, “I’m scared,” as the Sun on screen gradually transformed into angry red gas. Overall, it was a fitting conclusion to an informative and memorable night.
The Stargazing and Lecture series will continue throughout the year, occurring every two weeks. Catch the next one, “Observing Variable Stars”, presented by Stella Kafka, on October 16th at 8 pm.

Goth sky imagery via Shutterstock