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What Makes Something A Planet, According To An Astrophysicist?

“A dolphin may look like a fish, but it’s really a mammal. Similarly, the composition of an object is not the only factor in classifying it: its evolutionary history is inextricably related to its properties. Scientists will likely continue to argue over how to best classify all of these worlds, but it’s not just astronomers and planetary scientists who have a stake in this. In the quest to make organizational sense of the Universe, we have to confront it with the full suite of our knowledge.

Although many will disagree, moons, asteroids, Kuiper belt and Oort cloud objects are fascinating objects just as worthy of study as modern-day planets are. They may even be better candidates for life than many of the true planets are. But each object’s properties are inextricably related to the entirety of its formation history. When we try to classify the full suite of what we’re finding, we must not be misled by appearances alone.”

You’ve heard about the IAU’s definition, where in order to be a planet, you must pull yourself into hydrostatic equilibrium, orbit the Sun and nothing else, and gravitationally clear your orbit. You’ve also heard about the controversial new definition from geophysical/planetary science arguments, that planets should be based on their ability to pull themselves into a spheroidal shape alone.

Well, what about a third way: defining planets (and a whole classification scheme) based on astrophysical concerns alone? It’s time to start thinking about it!

Happy Birthday To Vera Rubin: The Mother Of Our Dark Matter Universe

“Dark matter should drive the formation of structure on all large scales, with every galaxy consisting of a large, diffuse halo of dark matter that is far less dense and more diffuse than the normal matter. While the normal matter clumps and clusters together, since it can stick together and interact, dark matter simply passes through both itself and normal matter. Without dark matter, the Universe wouldn’t match our observations.

But this branch of science truly got its start with the revolutionary work of Vera Rubin. While many, including me, will deride the Nobel committee for snubbing her revolutionary science, she truly did change the Universe. On what would have been her 91st birthday, remember her in her own words:

“Don’t let anyone keep you down for silly reasons such as who you are, and don’t worry about prizes and fame. The real prize is finding something new out there.”

50 years later, we’re still investigating the mystery Vera Rubin uncovered. May there always be more to learn.”

Today, dark matter is practically accepted as a given, owing to an overwhelming suite of evidence that points to its existence. Without adding dark matter as an ingredient, we simply can’t explain the Universe, from gravitational lensing to large-scale structure to Big Bang nucleosynthesis to the cosmic microwave background and much more. But throughout the 1930s, 40s and 50s, no one would even give the idea a second thought. Until, that is, Vera Rubin came along and changed everything. 

Today would have been her 91st birthday, and it’s about time you got the scientific story to celebrate what she taught us all.

Esmeralda finding the King of Fools.

CAPE CANAVERAL, Fla. – Space shuttle Discovery lifts off Launch Pad 39A in a billowing swirl of smoke and steam at NASA’s Kennedy Space Center in Florida, beginning its final flight, the STS-133 mission. Launch to the International Space Station was at 4:53 p.m. EST.

Credit: NASA

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First look at the 2024 total solar eclipse

The path of the April 8, 2024 total solar eclipse begins in the United States in Texas and ends in Maine. Google, INEGI

…The length of totality varies from one eclipse to the next. The reason is that Earth is not always the same distance from the Sun, and the Moon is not always the same distance from Earth. The Earth-Sun distance varies by 3 percent and the Moon-Earth distance by 12 percent. The result is that the maximum duration of totality from 2000 b.c. to a.d. 3000 is 7 minutes, 29 seconds. (That eclipse will occur July 16, 2186, so don’t get too excited for it.)

While the maximum length of totality during the April 8, 2024, eclipse won’t be that long, it’s still a worthy chunk of time: 4 minutes, 28 seconds — 67 percent longer than the one in 2017. And as with that one, everyone in the contiguous U.S. will see at least a partial eclipse. In fact, as long as you have clear skies on eclipse day, the Moon will cover at least 16.15 percent of the Sun’s brilliant surface. That minimum comes at Tatoosh Island, a tiny speck of land west of Neah Bay, Washington. And although our satellite covering any part of the Sun’s disk sounds cool, you need to aim higher.

Read more ~ Astronomy Magazine Posted by Michael Bakich on Sunday, September 23, 2018

A Surprising Surge at Vavilov Ice Cap

After moving quite slowly for decades, the outlet glacier of Vavilov Ice Cap began sliding dozens of times faster than is typical. The ice moved fast enough for the fan-shaped edge of the glacier to protrude from an ice cap on October Revolution Island and spread widely across the Kara Sea. The Landsat images above were acquired on July 1, 2013, June 18, 2015, and June 24, 2018, respectively.

“The fact that an apparently stable, cold-based glacier suddenly went from moving 20 meters per year to 20 meters per day was extremely unusual, perhaps unprecedented,” said University of Colorado Boulder glaciologist Michael Willis. “The numbers here are simply nuts. Before this happened, as far as I knew, cold-based glaciers simply didn’t do that…couldn’t do that.”

Willis and his colleagues are still piecing together what triggered such a dramatic surge. They suspect that marine sediments immediately offshore are unusually slippery, perhaps containing clay. Also, water must have somehow found its way under the land-based part of the glacier, reducing friction and priming the ice to slide.

Full story here: go.nasa.gov/2Z931lc

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Here’s Why Black Holes Are Crullers, Not Donuts

“Just a few years ago, we didn’t even know whether it was a certainty that black holes had an event horizon, as we’d never observed one directly. In 2017, a series of observations were finally taken that could settle the issue. After a wait of two years, the first direct image of a black hole was released, and it showed us that the event horizon was, in fact, real as predicted, and that its properties agreed with Einstein’s predictions.

Now, another two years later, the polarization data has been added into the fold, and we can now reconstruct the magnetic properties of the plasma surrounding the black hole, along with how those features are imprinted onto the emitted photons. We still only have the one black hole that’s been directly imaged, but we can see how the light, the polarization, and the magnetic properties of the plasma surrounding the event horizon all change over time.”

You’ve seen the photo, but have you learned the science? Black holes are crullers, not donuts, and magnetized plasma is the reason why.

Three Ways to Travel at (Nearly) the Speed of Light

One hundred years ago, Einstein’s theory of general relativity was supported by the results of a solar eclipse experiment. Even before that, Einstein had developed the theory of special relativity — a way of understanding how light travels through space.

Particles of light — photons — travel through a vacuum at a constant pace of more than 670 million miles per hour.

All across space, from black holes to our near-Earth environment, particles are being accelerated to incredible speeds — some even reaching 99.9% the speed of light! By studying these super fast particles, we can learn more about our galactic neighborhood. 

Here are three ways particles can accelerate:

1) Electromagnetic Fields!

Electromagnetic fields are the same forces that keep magnets on your fridge! The two components — electric and magnetic fields — work together to whisk particles at super fast speeds throughout the universe. In the right conditions, electromagnetic fields can accelerate particles at near-light-speed.

We can harness electric fields to accelerate particles to similar speeds on Earth! Particle accelerators, like the Large Hadron Collider and Fermilab, use pulsed electromagnetic fields to smash together particles and produce collisions with immense amounts of energy. These experiments help scientists understand the Big Bang and how it shaped the universe!

2) Magnetic Explosions!

Magnetic fields are everywhere in space, encircling Earth and spanning the solar system. When these magnetic fields run into each other, they can become tangled. When the tension between the crossed lines becomes too great, the lines explosively snap and realign in a process known as magnetic reconnection. Scientists suspect this is one way that particles — for example, the solar wind, which is the constant stream of charged particles from the Sun — are sped up to super fast speeds.

When magnetic reconnection occurs on the side of Earth facing away from the Sun, the particles can be hurled into Earth’s upper atmosphere where they spark the auroras.

3) Wave-Particle Interactions!

Particles can be accelerated by interactions with electromagnetic waves, called wave-particle interactions. When electromagnetic waves collide, their fields can become compressed. Charged particles bounce back and forth between the waves, like a ball bouncing between two merging walls. These types of interactions are constantly occurring in near-Earth space and are responsible for damaging electronics on spacecraft and satellites in space.

Wave-particle interactions might also be responsible for accelerating some cosmic rays from outside our solar system. After a supernova explosion, a hot, dense shell of compressed gas called a blast wave is ejected away from the stellar core. Wave-particle interactions in these bubbles can launch high-energy cosmic rays at 99.6% the speed of light.

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