绿帽换妻

In a galaxy far, far away … a supermassive black hole 70 million times the mass of the sun sucks down everything around it — even light cannot escape its gravitational pull.

 Except sometimes, when the extraordinary magnetic field surrounding the black hole causes nearby eruptions of high-energy particles to spew into space like lava from a cosmic volcano.

 And when that happens, scientists have the chance to observe what is always there but seldom can be seen: A blazar — the core of a galactic jet burning its way straight toward Earth.

But these intergalactic storm troopers aren’t just the most volatile eruption of energy in the universe — they’re like windows into the past, allowing scientists to study the formation of the cosmos itself, and perhaps understand more about the evolution of our own galaxy. 

Cal State East Bay Assistant Professor Amy Furniss is used to the looks of bewilderment she gets in explaining what she does for a living. When she mentions cosmology (the study of the origins of the universe), “Most people think I do nails,” she says. “Very commonly in a conference room, someone will tell me the coffee has run out.”

But no, Furniss is a very-high-energy astroparticle physicist whose grandmother was, she proudly recounts, a rare female nuclear engineer of her day.

Furniss herself has a galaxy discovery under her belt (AGC 193784 during her undergraduate years at CSU Humboldt), and she’s part of a global network of scientists working to reconstruct how the universe came to be, one frame and unpredictable cataclysmic event at a time.

It was December 2015, just as she was boarding a plane, when Furniss was alerted to a recent blazar flare-up.

Outside Cal State East Bay, the professor is associated with NASA’s Fermi gamma-ray space telescope, and she is a leader within VERITAS (the Very Energetic Radiation Imaging Telescope Array System) in Arizona, one of just three ground-based gamma-ray observatories in the world.

So, when NASA’s Fermi detector was triggered by a blazar of extraordinary strength and sustained brightness that traveled 7.6 billion years to reach us, Furniss was immediately on task to coordinate observations with VERITAS — and she has recently started feeding that data to her Cal State East Bay undergraduate students for computational analysis.  

“Because the (blazar) is so far away, we would expect that all the high-energy gamma rays that VERITAS could detect would disappear,” she says. “There was this period where I didn’t believe (we had detected it).”

What Furniss is getting at is the great irony of distant blazars: The very events they give us information about — star formation and thus the expansion of the universe — are what typically snuff out their gamma rays before they can complete the extragalactic voyage.

When a gamma ray hits a photon of blue or UV light, both energy sources are converted into an electron and a positron. Although space is made up of mostly vast voids, there are enough stars and galaxies to create a minefield of blue/UV photons. The farther a photon has to travel, the more likely it is to be annihilated — along with the chance to view a blazar. 

“What is special about blazars is that they’re pointed straight toward us,” Furniss says. “Imagine if you filled a gym with 1,000 kids playing flashlight tag — how many times would you see a flashlight pointed straight at you? Not nearly as often as you see the flashlights pointed away from you. So far, we have so few (blazars to observe), we’re just collecting the basket of fruit so we can study it.”

Furniss reports that from 1991 to 2006 only a handful of gamma-ray blazars were on record, and since VERITAS went live in 2006, the number has jumped to approximately 100 — still not many considering the awesome number of galaxies we know to exist in the universe. 

“It’s not yet determined whether or not these extreme galaxies called blazars are in special regions of both space and time,” she says. “Do they only exist in some very short period of the evolution of the universe?

“Yet if we look out at other galaxies … we can see some that are a little younger, some that are little older,” Furniss continues, “and we can get an idea of whether our own galaxy is ramping up, ramping down, or maybe never destined to be active like these blazars.”

In the meantime, while the basket of fruit is being gathered, this distant blazar, dubbed PKS 1441+25, sets a new precedent in high-energy gamma ray detection for VERITAS, which Furniss says is part of a growing momentum in contemporary astroparticle physics.

“These astronomical instruments are perfect to follow up on gravitational wave detection,” she explains, referring to the recent scientific watershed. “Gravitational wave detection is going to change the entire paradigm of what is possible in the universe … it’s like acquiring a completely new language. We’re going to learn as much as we’ve been able to learn with astronomy, and with the technology that’s available today, it’s going to pick up a lot of momentum. If you went back to a time when people thought Earth was flat, they wouldn’t have said, ‘Someday we might discover the world is round.’ What we’re going to learn is unimaginable.”