Image of the Week: Blazars, gamma rays and black holes

It’s been a minute since we posted an Image of the Week. To make up for it, we’re giving you three very neat images of space stuff. So let’s talk about cosmic phenomena.

Pulsars are highly magnetized rotating neutron stars that emits beams of electromagnetic radiation.

Quasars are massive and extremely remote celestial objects, emitting exceptionally large amounts of energy, and typically having a starlike image in a telescope.

Bynars are a race of humanoids native to the planet Bynaus in the Beta Magellan system. They once commandeered the Enterprise-D when it was undergoing repairs at a starbase. It was a whole thing. It may also have been fictional. Who knows?

Lunar is pronounced differently, so has no relevance to this list.

Blazars, though. Blazars are very, very cool.

As we get better and better telescopes to study the universe, scientists get closer to answering fundamental questions, like what lives at the center of a galaxy? A popular theory is that certain galaxies have supermassive black holes at their center.

Scientists can observe this phenomenon in other galaxies near ours. In fact, black-hole-powered galaxies are the most common sources detected by NASA’s Fermi Gamma-ray Space Telescope. 

As matter falls toward the supermassive black hole at the galaxy’s center, some of it is accelerated outward at nearly the speed of light along jets pointed in opposite directions. When one of the jets happens to be aimed in the direction of Earth, as illustrated here, the galaxy appears especially bright and is classified as a blazar.

The image up top is an artist’s rendering of what a blazar might look like. The actual images of them look a bit less dramatic, but are still very cool. 

Blazars through a telescope

In 2017, the Fermi Space Telescope captured an image of a blazar’s gamma-ray flare. Gamma rays with energies from 100 million to 100 billion electron volts (eV) are shown in the image below; for comparison, visible light has energies between 2 and 3 eV. 

Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. They are produced by the hottest and most energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around black holes. On Earth, gamma waves are generated by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.

Gamma-ray bursts are the most energetic and luminous electromagnetic events since the Big Bang and can release more energy in 10 seconds than our Sun will emit in its entire 10-billion-year expected lifetime.

Supermassive Black Hole

That brings us to our final image of the post: an actual black hole. Earlier this year, a team of scientists became the first to capture an image of a black hole. On April 10, 2019, the Event Horizon Telescope (EHT) unveiled the first-ever image of a black hole’s event horizon, the area beyond which light cannot escape the immense gravity of the black hole. That giant black hole, with a mass of 6.5 billion Suns, is located in the elliptical galaxy Messier 87 (M87). 

Located about 55 million light-years from Earth, M87 has been a subject of study for more than 100 years. It has been imaged by many NASA observatories. In 1918, astronomer Heber Curtis first noticed “a curious straight ray” extending from the galaxy’s center.

This bright jet of high-energy material, produced by a disk of material spinning rapidly around the black hole, is visible in multiple wavelengths of light, from radio waves through X-rays. When the particles in the jet impact the sparse material filling the space between stars in M87, they create a shockwave that radiates in infrared and radio wavelengths of light but not visible light.

By combining observations in the infrared, radio waves, visible light, X-rays and extremely energetic gamma rays, scientists can study the physics of these powerful jets. Scientists are still striving for a solid theoretical understanding of how gas being pulled into black holes creates outflowing jets.

Meaning scientists are still learning and exploring what makes this universe unique. Imagine what kinds of images they’ll show us next.

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