Cosmic Rays

Created using still images taken by the Cassini spacecraft during it’s flyby of Jupiter and while at Saturn. Shown is Io and Europa over Jupiter’s Great Red Spot.

NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill

How Do You Solve a Problem Like Dark Energy?

Here’s the deal — the universe is expanding. Not only that, but it’s expanding faster and faster due to the presence of a mysterious substance scientists have named “dark energy.”

But before we get to dark energy, let’s first talk a bit about the expanding cosmos. It started with the big bang — when the universe started expanding from a hot, dense state about 13.8 billion years ago. Our universe has been getting bigger and bigger ever since. Nearly every galaxy we look at is zipping away from us, caught up in that expansion!

The expansion, though, is even weirder than you might imagine. Things aren’t actually moving away from each other. Instead, the space between them is getting larger.

Imagine that you and a friend were standing next to each other. Just standing there, but the floor between you was growing. You two aren’t technically moving, but you see each other moving away. That’s what’s happening with the galaxies (and everything else) in our cosmos … in ALL directions!

Astronomers expected the expansion to slow down over time. Why? In a word: gravity. Anything that has mass or energy has gravity, and gravity tries to pull stuff together. Plus, it works over the longest distances. Even you, reading this, exert a gravitational tug on the farthest galaxy in the universe! It’s a tiny tug, but a tug nonetheless.

As the space between galaxies grows, gravity is trying to tug the galaxies back together — which should slow down the expansion. So, if we measure the distance of faraway galaxies over time, we should be able to detect if the universe’s growth rate slows down.  

But in 1998, a group of astronomers measured the distance and velocity of a number of galaxies using bright, exploding stars as their “yardstick.” They found out that the expansion was getting faster.

Not slowing down.

Speeding up.

⬆️ This graphic illustrates the history of our expanding universe. We do see some slowing down of the expansion (the uphill part of the graph, where the roller coaster is slowing down). However, at some point, dark energy overtakes gravity and the expansion speeds up (the downhill on the graph). It’s like our universe is on a giant roller coaster ride, but we’re not sure how steep the hill is!

Other researchers also started looking for signs of accelerated expansion. And they found it — everywhere. They saw it when they looked at individual stars. They saw it in large scale structures of the universe, like galaxies, galaxy groups and clusters. They even saw it when they looked at the cosmic microwave background (that’s what’s in this image), a “baby picture” of the universe from just a few hundred thousand years after the big bang.

If you thought the roller coaster was wild, hold on because things are about to get really weird.

Clearly, we were missing something. Gravity wasn’t the biggest influence on matter and energy across the largest scales of the universe. Something else was. The name we’ve given to that “something else” is dark energy.

We don’t know exactly what dark energy is, and we’ve never detected it directly. But we do know there is a lot of it. A lot. If you summed up all the “stuff” in the universe — normal matter (the stuff we can touch or observe directly), dark matter, and dark energy — dark energy would make up more than two-thirds of what is out there.

That’s a lot of our universe to have escaped detection!

Researchers have come up with a few dark energy possibilities. Einstein discarded an idea from his theory of general relativity about an intrinsic property of space itself. It could be that this bit of theory got dark energy right after all. Perhaps instead there is some strange kind of energy-fluid that fills space. It could even be that we need to tweak Einstein’s theory of gravity to work at the largest scales.  

We’ll have to stay tuned as researchers work this out.

Our Wide Field Infrared Survey Telescope (WFIRST) — planned to launch in the mid-2020s — will be helping with the task of unraveling the mystery of dark energy. WFIRST will map the structure and distribution of matter throughout the cosmos and across cosmic time. It will also map the universe’s expansion and study galaxies from when the universe was a wee 2-billion-year-old up to today. Using these new data, researchers will learn more than we’ve ever known about dark energy. Perhaps even cracking open the case!

You can find out more about the history of dark energy and how a number of different pieces of observational evidence led to its discovery in our Cosmic Times series. And keep an eye on WFIRST to see how this mystery unfolds.

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Loving Vincent (2017) dir. Dorota Kobiela, Hugh Welchman

At Last, Scientists Have Found The Galaxy’s Missing Exoplanets: Cold Gas Giants

“By using the same instrument and leaving virtually no long-term gaps in the data, long-term, precise Doppler measurements finally became possible. A total of five brand new planets, one confirmation of a suggested planet, and three updated planets were announced in this latest study, bringing the total number of Jupiter-or-larger planets beyond the Jupiter-Sun distance up to 26. It shows us what we’d always hoped for: that our Solar System isn’t so unusual in the Universe; it’s just difficult to observe and detect planets like the ones we have.”

We’ve long suspected that there was nothing special about our Solar System; that Sun-like stars should have a wide variety of planets around them, including many of the types of worlds found orbiting our Sun. However, owing to the difficulty in making the kinds of measurements that would reveal them to us, our work has revealed a sample of planets biased towards two types of planets: the short-period worlds and the well-separated, high-mass worlds. Planets like Jupiter or Saturn were elusive for so long. But now, owing to research programs dedicated to monitoring nearby stars on decadal timescales, we’ve revealed a remarkable number of these worlds, many of which are now candidates for future direct imaging surveys.

The missing gas giants of the Universe, including worlds like the ones actually found orbiting our Sun, are finally within reach. Here’s how we’ve revealed them at last!

All cats are beautiful 🐱❤️

10 Things: CubeSats — Going Farther

Now that the MarCOs — a pair of briefcase-sized interplanetary CubeSats — seem to have reached their limit far beyond Mars, we’re looking forward to an expanding era of small, versatile and powerful space-based science machines.

Here are ten ways we’re pushing the limits of miniaturized technology to see  just how far it can take us.

1. MarCO: The Farthest (So Far)

MarCO, short for Mars Cube One, was the first interplanetary mission to use a class of mini-spacecraft called CubeSats.

The MarCOs — nicknamed EVE and WALL-E, after characters from a Pixar film — served as communications relays during InSight’s November 2018 Mars landing, beaming back data at each stage of its descent to the Martian surface in near-real time, along with InSight’s first image.

WALL-E sent back stunning images of Mars as well, while EVE performed some simple radio science.

All of this was achieved with experimental technology that cost a fraction of what most space missions do: $18.5 million provided by NASA’s Jet Propulsion Laboratory in Pasadena, California, which built the CubeSats.

WALL-E was last heard from on Dec. 29; EVE, on Jan. 4. Based on trajectory calculations, WALL-E is currently more than 1 million miles (1.6 million kilometers) past Mars; EVE is farther, almost 2 million miles (3.2 million kilometers) past Mars.

MarCO-B took these images as it approached Mars in November 2018. Credit: NASA/JPL-Caltech

2. What Are CubeSats?

CubeSats were pioneered by California Polytechnic State University in 1999 and quickly became popular tools for students seeking to learn all aspects of spacecraft design and development.

Today, they are opening up space research to public and private entities like never before. With off-the-shelf parts and a compact size that allows them to hitch a ride with other missions — they can, for example, be ejected from the International Space Station, up to six at a time — CubeSats have slashed the cost of satellite development, opening up doors to test new instruments as well as to create constellations of satellites working together.

CubeSats can be flown in swarms, capturing simultaneous, multipoint measurements with identical instruments across a large area. Sampling entire physical systems in this way would drive forward our ability to understand the space environment around us, in the same way multiple weather sensors help us understand global weather systems.

Ready to get started? Check out NASA’s CubeSats 101 Guide.

Engineer Joel Steinkraus uses sunlight to test the solar arrays on one of the Mars Cube One (MarCO) spacecraft at NASA’s Jet Propulsion Laboratory. Credit: NASA/JPL-Caltech

3. Measuring Up

The size and cost of spacecraft vary depending on the application; some are the size of a pint of ice cream while others, like the Hubble Space Telescope, are as big as a school bus.

Small spacecraft (SmallSats) generally have a mass less than 400 pounds (180 kilograms) and are about the size of a large kitchen fridge.

CubeSats are a class of nanosatellites that use a standard size and form factor.  The standard CubeSat size uses a “one unit” or “1U” measuring 10x10x10 centimeters (or about 4x4x4 inches) and is extendable to larger sizes: 1.5, 2, 3, 6, and even 12U.

The Sojourner rover (seen here on Mars in 1997) is an example of small technology that pioneered bigger things. Generations of larger rovers are being built on its success.

4. A Legacy of Small Pathfinders

Not unlike a CubeSat, NASA’s first spacecraft — Explorer 1 — was a small, rudimentary machine. It launched in 1958 and made the first discovery in outer space, the Van Allen radiation belts that surround Earth. It was the birth of the U.S. space program.

In 1997, a mini-rover named Sojourner rolled onto Mars, a trial run for more advanced rovers such as NASA’s Spirit, Opportunity and Curiosity.

Innovation often begins with pathfinder technology, said Jakob Van Zyl, director of the Solar System Exploration Directorate at NASA’s Jet Propulsion Laboratory. Once engineers prove something can be done, science missions follow.

5. Testing in Space

NASA is continually developing new technologies — technologies that are smaller than ever before, components that could improve our measurements, on-board data processing systems that streamline data retrievals, or new methods for gathering observations. Each new technology is thoroughly tested in a lab, sometimes on aircraft, or even at remote sites across the world. But the space environment is different than Earth. To know how something is going to operate in space, testing in space is the best option.

Sending something unproven to orbit has traditionally been a risky endeavor, but CubeSats have helped to change that. The diminutive satellites typically take less than two years to build. CubeSats are often a secondary payload on many rocket launches, greatly reducing cost. These hitchhikers can be deployed from a rocket or sent to the International Space Station and deployed from orbit.

Because of their quick development time and easy access to space, CubeSats have become the perfect platform for demonstrating how a new technological advancement will perform in orbit.

RainCube is a mini weather satellite, no bigger than a shoebox, that will measure storms. It’s part of several new NASA experiments to track storms from space with many small satellites, instead of individual, large ones. Credit: UCAR

6. At Work in Earth Orbit

A few recent examples from our home world:

RainCube, a satellite no bigger than a suitcase, is a prototype for a possible fleet of similar CubeSats  that could one day help monitor severe storms, lead to improving the accuracy of weather forecasts and track climate change over time.

IceCube tested instruments for their ability to make space-based measurements of the small, frozen crystals that make up ice clouds. Like other clouds, ice clouds affect Earth’s energy budget by either reflecting or absorbing the Sun’s energy and by affecting the emission of heat from Earth into space. Thus, ice clouds are key variables in weather and climate models.

Rocket Lab’s Electron rocket lifts off from Launch Complex 1 for the NASA ELaNa19 mission. Credit: Trevor Mahlmann/Rocket Lab

7. First Dedicated CubeSat Launch

A series of new CubeSats is now in space, conducting a variety of scientific investigations and technology demonstrations following a Dec. 17, 2018 launch from New Zealand — the first time CubeSats have launched for NASA on a rocket designed specifically for small payloads.

This mission included 10 Educational Launch of Nanosatellites (ELaNa)-19 payloads, selected by NASA’s CubeSat Launch Initiative:

CubeSat Compact Radiation Belt Explorer (CeREs) — High energy particle measurement in Earth’s radiation belt

Simulation-to-Flight 1 (STF-1) — Software condensing to support CubeSat implementations

Advanced Electrical Bus (ALBus) — Advances in solar arrays and high capacity batteries

CubeSat Handling Of Multisystem Precision Time Transfer (CHOMPTT) — Navigation plans for exo-planetary implementation

CubeSail — Deployment and control of a solar sail blade

NMTSat — Magnetic field, high altitude plasma density

Rsat — Manipulation of robotic arms

Ionospheric Scintillation Explorer (ISX) — Plasma fluctuations in the upper atmosphere

Shields-1 — Radiation shielding

DaVinci — High School to Grade School STEM education

8. The Little CubeSat That Could

CubeSat technology is still in its infancy, with mission success rates hovering near 50 percent. So, a team of scientists and engineers set out on a quest. Their goal? To build a more resilient CubeSat — one that could handle the inevitable mishaps that bedevil any spacecraft, without going kaput.

They wanted a little CubeSat that could.

They got to work in 2014 and, after three years of development, Dellingr was ready to take flight.

Read the Full Story: Dellingr: The Little CubeSat That Could

Artist’s concept of Lunar Flashlight. Credit: NASA

9. Going Farther

There are a handful of proposed NASA missions could take CubeSat technology farther:

CUVE would travel to Venus to investigate a longstanding mystery about the planet’s atmosphere using ultraviolet-sensitive instruments and a novel, carbon-nanotube light-gathering mirror.

Lunar Flashlight would use a laser to search for water ice in permanently shadowed craters on the south pole of Earth’s Moon.

Near-Earth Asteroid Scout, a SmallSat, would use a solar sail to propel it to do science on asteroids that pass close to Earth.

All three spacecraft would hitch rides to space with other missions, a key advantage of these compact science machines.

Expedition 56 Flight Engineer Serena Auñón-Chancellor installs the NanoRacks Cubesat Deployer-14 (NRCSD-14) on the Multipurpose Experiment Platform inside the Japanese Kibo laboratory module. The NRCSD-14 was then placed in the Kibo airlock and moved outside of the space station to deploy a variety of CubeSats into Earth orbit. Credit: NASA

10. And We’re Just Getting Started

Even if they’re never revived, the team considers MarCO a spectacular success.

A number of the critical spare parts for each MarCO will be used in other CubeSat missions. That includes their experimental radios, antennas and propulsion systems. Several of these systems were provided by commercial vendors, making it easier for other CubeSats to use them as well.

More small spacecraft are on the way. NASA is set to launch a variety of new CubeSats in coming years.

“There’s big potential in these small packages,” said John Baker, the MarCO program manager at JPL. “CubeSats — part of a larger group of spacecraft called SmallSats — are a new platform for space exploration affordable to more than just government agencies.”

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Stellar Winds

Stellar winds are fast moving flows of material (protons, electrons and atoms of heavier metals) that are ejected from stars. These winds are characterised by a continuous outflow of material moving at speeds anywhere between 20 and 2,000 km/s.

In the case of the Sun, the wind ‘blows’ at a speed of 200 to 300 km/s from quiet regions, and 700 km/s from coronal holes and active regions.

The causes, ejection rates and speeds of stellar winds vary with the mass of the star. In relatively cool, low-mass stars such as the Sun, the wind is caused by the extremely high temperature (millions of degrees Kelvin) of the corona.

his high temperature is thought to be the result of interactions between magnetic fields at the star’s surface, and gives the coronal gas sufficient energy to escape the gravitational attraction of the star as a wind. Stars of this type eject only a tiny fraction of their mass per year as a stellar wind (for example, only 1 part in 1014 of the Sun’s mass is ejected in this way each year), but this still represents losses of millions of tonnes of material each second. Even over their entire lifetime, stars like our Sun lose only a tiny fraction of 1% of their mass through stellar winds.

In contrast, hot, massive stars can produce stellar winds a billion times stronger than those of low-mass stars. Over their short lifetimes, they can eject many solar masses (perhaps up to 50% of their initial mass) of material in the form of 2,000 km/sec winds.

These stellar winds are driven directly by the radiation pressure from photons escaping the star. In some cases, high-mass stars can eject virtually all of their outer envelopes in winds. The result is a Wolf-Rayet star.

Stellar winds play an important part in the chemical evolution of the Universe, as they carry dust and metals back into the interstellar medium where they will be incorporated into the next generation of stars. 

source (read more) + Wolf–Rayet star

Ask Ethan: Why Are There Only Three Generations Of Particles?

“It is eminently possible that there are more particles out there than the Standard Model, as we know it, presently predicts. In fact, given all the components of the Universe that aren’t accounted for in the Standard Model, from dark matter to dark energy to inflation to the origin of the matter-antimatter asymmetry, it’s practically unreasonable to conclude that there aren’t additional particles.

But if the additional particles fit into the structure of the Standard Model as an additional generation, there are tremendous constraints. They could not have been created in great abundance during the early Universe. None of them can be less massive than 45.6 GeV/c^2. And they could not imprint an observable signature on the cosmic microwave background or in the abundance of the light elements.

Experimental results are the way we learn about the Universe, but the way those results fit into our most successful theoretical frameworks is how we conclude what else does and doesn’t exist in our Universe. Unless a future accelerator result surprises us tremendously, three generations is all we get: no more, no less, and nobody knows why.”

There are three generations of (fermionic) particles in the Universe. In addition to the lightest quarks (up and down), the electron and positron, and the electron neutrino and anti-neutrino, there are two extra, heavy “copies” of this structure. The charm-and-strange quarks plus the top-and-bottom quarks fill the remaining generations of quarks, while the muon and muon neutrino and anti-neutrino plus the tau and tau neutrino and anti-neutrino comprise the next generation of leptons.

Theoretically, there’s nothing demanding three and only three generations, but experiments have shown that there are no more to within absurd constraints. Here’s the full story of how we know there are only three generations.