Earth: Hi sun!
“Year after year since its 1990 launch, Hubble keeps revolutionizing our view of the Universe. No other observatory continues to teach us so much. 28 years on, it’s still yielding uniquely spectacular scientific sights.”
There were a slew of scientific, astronomical breakthroughs made this past year, and Hubble was at the forefront of a great many of them. There was a tremendous dust storm enveloping Mars, and Hubble was there to capture it. Saturn’s rings are evaporating so quickly that they’ll be gone in 100 million years, and Hubble captured them. Ultraviolet light is created in great abundance in the nearby Universe from star-forming galaxies, and Hubble completed a survey of them. Ultra-distant galaxies form stars too, and Hubble was there to image them and measure how far it truly is to them. Galaxies speed through clusters; clusters contain stars ripped out of galaxies; nebulae race to form stars before the gas gets blown away by the existing ones. Through it all, Hubble was there.
“Over the past 30 years, astronomers have gone from zero known extra-solar planets to thousands. Periodic changes in a star’s motion or regular brightness dips give them away. Thanks to these techniques, we’ve revealed the masses and radii of worlds nearby and thousands of light years away. Over 200 are Earth-sized, with many residing in the so-called habitable zone around their stars. Yet with everything we’ve found, there are no potentially habitable Earth-like worlds around Sun-like stars.”
One of the greatest success stories over the past 30 years is the giant leap forward we’ve taken in understanding what worlds lie beyond our Solar System. We’ve gone, in that time, from exactly zero known planets beyond our Solar System to thousands. We’ve found worlds far larger than Jupiter, some of which revolve at distances interior to even Mercury’s orbit. We’ve found planets around blue supergiants and red dwarfs. And we’ve discovered small worlds, some of which are even smaller than Earth. Some of them even occur in the so-called habitable zone of their stars.
“New stars form in large clusters, creating stars of all different masses simultaneously.
As they age, the more massive stars die first, leaving only the lower-mass ones behind.
We can date star clusters by examining which stars remain when we plot out stellar color vs. temperature. The older a cluster is, the redder, lower-mass, and less bright its surviving stars are. Globular star clusters are the oldest; some haven’t formed stars in ~13 billion years. Yet if we look closely inside these ancient relics from the young Universe, we’ll find a few blue stars.”
Okay, science fans, I’ve got a mystery for you. When you look at a star cluster, you’ll find a wide variety of stars inside: from the ultra-massive, hot, blue ones down to the lower-mass, cool, red ones. The older a cluster is, the redder it is, because the more massive, hotter, bluer ones burn through their fuel faster and die first. But as a cluster gets redder, we’ll inevitably find a few blue stars that don’t belong. These “blue straggler” stars behave as though they’ve formed at a later time than the rest of the cluster, even though we know that cannot be true. Yet they’re real, they’re there, and their lifetimes are often just 10% the known age of the cluster itself.
“The result, today, is that the largest and most massive body ever to form in the Kuiper belt — 20% larger than Pluto; 29% more massive than Eris — is now Neptune’s largest moon: Triton. Today, Triton makes up 99.5% of the mass orbiting Neptune, an enormous departure from all the other giant planet systems we know of. The only explanation for its properties, especially its bizarre and unique orbit, is that Triton is a captured Kuiper belt object.
We often talk about icy moons with subsurface oceans as candidate worlds for life. We imagine large, distant, icy bodies as planets or dwarf planets in their own right. Triton was born not as a moon of Neptune, but as the largest and most massive Kuiper belt object to survive. You don’t cease to exist when you move locations, and neither did Triton. It’s the original king of the Kuiper belt, and its true origin story is a cosmic mystery that deserves to be solved.”
In October of 1846, just months after Neptune was discovered, a large moon was discovered around it: Triton. Today, Triton is a supremely unusual moon for a number of reasons, but the largest is that it rotates in the wrong direction. While Neptune orbits the Sun counterclockwise and spins counterclockwise on its tilted axis, Triton orbits in the opposite direction. The only way this could have happened is if it were a captured object. And that’s exactly what it looks like: a captured object from the Kuiper belt!
“An enormous part of our cosmic history has just been revealed for the very first time. We can bypass the foregrounds of our own Solar System, thanks to these gamma-ray signals and how they interact with the extragalactic background of starlight, to understand and measure how star-formation has occurred over all of cosmic time in our Universe, and to infer the total amount of starlight ever produced.
In the future, scientists may be able to go back even farther, and probe how stars formed and emitted light back before the Fermi-LAT team’s instrumentation is capable of reaching. Star formation is what turns the primordial elements from the Big Bang into the elements capable of giving rise to rocky planets, organic molecules, and life in the Universe. Perhaps, one day, we’ll find a way to reach all the way back to the earliest moments of our Universe, uncovering the truths behind the greatest cosmic mysteries of all. Until then, enjoy each and every step — like this one — that we take along the journey!”
For the first time ever, we’ve measured the total amount of starlight ever produced throughout the history of the Universe. We know how many photons, created by stars, now permeate all of space. We know when star-formation peaked, and we know how it’s fallen over time, and how it continues to fall.
The Aurora and the Sunrise : On the International Space Station (ISS), you can only admire an aurora until the sun rises. Then the background Earth becomes too bright. Unfortunately, after sunset, the rapid orbit of the ISS around the Earth means that sunrise is usually less than 47 minutes away. In the featured image, a green aurora is visible below the ISS – and on the horizon to the upper right, while sunrise approaches ominously from the upper left. Watching an aurora from space can be mesmerizing as its changing shape has been compared to a giant green amoeba. Auroras are composed of energetic electrons and protons from the Sun that impact the Earth’s magnetic field and then spiral down toward the Earth so fast that they cause atmospheric atoms and molecules to glow. The ISS orbits at nearly the same height as auroras, many times flying right through an aurora’s thin upper layers, an event that neither harms astronauts nor changes the shape of the aurora. via NASA
“Is there theoretical or experimental evidence which unambiguously establishes the existence of fundamental particles?”
When we talk about the Standard Model, including the quarks, leptons, their antiparticles, and the bosons that make up the Universe, we implicitly assume that these are fundamental particles. When we say fundamental, we often imply that these are the smallest possible, indivisible structural components of all that exists. Yet there’s a limit as far as how well we actually know this goes. Our experimental reach is limited in terms of energy; better deep inelastic scattering experiments might yet reveal a composite structure to the particles that we presently think are fundamental. There might be a more fundamental structure that makes up these particles, and those structures may not be particles. Dark matter and dark energy may not be particles at all, and space and time might be continuous or discrete, quantum or not, and either fundamental or emergent.