“Unlike the Sun, the Moon’s surface is made of mostly heavier elements, while the Sun is mostly hydrogen and helium. When cosmic rays (high-energy particles) from throughout the Universe collide with heavy atoms, nuclear recoil causes gamma-ray emission. With no atmosphere or magnetic field, and a lithosphere rich in heavy elements, cosmic rays produce gamma-rays upon impacting the Moon.”
When you view the Moon with your eyes, you’re not seeing it shine so brightly because it’s emitting its own light. Rather, it’s reflecting sunlight on its illuminated phase and reflecting light emitted from Earth (known as “Earthshine”) on the darkened portion. If you look at the Moon in many different wavelengths, from radio to infrared to ultraviolet to X-ray energies, you’ll find that the Sun is much brighter, and the Moon primarily emits light due to reflection.
But in gamma-rays, that entire story changes. The Sun emits virtually no high-energy gamma-rays, with only minor bursts during solar flared. The Moon, on the other hand, emits high-energy gamma-rays constantly; for almost 30 years we know that it outshines the Sun in this particular wavelength range.
Not Only Didn’t We Find Water On An Earth-Like Exoplanet, But We Can’t With Current Technology
“Over the past few decades, astronomers have uncovered thousands of new exoplanets. Some of them are rocky; some are temperate; some have water. However, the idea that exoplanet K2-18b is rocky, Earth-like, and has liquid water is absurd, despite recent headlines. Light filters through K2-18b’s atmosphere when it passes in front of its star, enabling us to measure what’s absorbed. Based on those absorption lines, the presence of many chemicals can be inferred, including water. K2-18b is, truly, the first known habitable-zone exoplanet to contain water. However, it is not rocky; its mass and radius are too large, necessitating a large gas envelope around it.”
How incredible was that report that came out last week: the first Earth-like, rocky exoplanet with liquid water on its surface has been discovered! If it were true, it would be incredible. Well, what we did find is still pretty remarkable, but it’s very different from what you’ve likely heard.
We did find water on the exoplanet in question, K2-18b, but only in the vapor phase and only in the atmosphere.
The exoplanet is closer to Earth in terms of mass and radius than any other with water on it, but the planet is still too massive and large to be rocky. It must have an envelope of hydrogen and helium, and both have had their presence detected.
Happy 230th Birthday, Enceladus, Our Solar System’s Greatest Hope For Life Beyond Earth
“It is still a complete unknown whether Earth is the only world in the Solar System to house any form of life: past or present. Venus and Mars may have been Earth-like for a billion years or more, and life could have arisen there early on. Frozen worlds with subsurface oceans, like Enceladus, Europa, Triton or Pluto, are completely different from Earth’s present environment, but have the same raw ingredients that could potentially lead to life as well.
Are water, energy, and the right molecules all we need for life to arise? Finding even the most basic organisms (or even the precursor components of organisms) anyplace else in the Universe would lead to a scientific revolution. A single discovered cell in the geysers of Enceladus would be the most momentous discovery of the 21st century. With the recent demise of Cassini, on the 230th anniversary of Enceladus’ discovery, the possibility of finding the incredible compels us to go back. May we be bold enough to make it so.”
On this date in 1789, William Herschel, armed with the most powerful telescope known to humanity at the time (you can get a lot of grant money when you discover the planet Uranus and name it after the King), discovered a relatively small moon of Saturn just 500 kilometers across: Enceladus. For some 200 years, Enceladus was never seen as more than a single pixel across, until the Voyager probes flew by it. What they revealed was a remarkable, unique world in all the Solar System. Now that the Cassini mission is complete, we can look back at all we know about this world, and all the signs point to a remarkable story: there’s a subsurface ocean, possibly suitable as a home for undersea life.
Astronomers Find A ‘Cloaked’ Black Hole 500 Million Years Before Any Other
“The first stars should lead to modest black holes: hundreds or thousands of solar masses. But when we see the Universe’s first black holes, they’re already ~1 billion solar masses. The leading idea is black holes form and merge, and then rapidly accrete matter at maximal rates. But those rapidly growing black holes should be invisible, obscured by the dense gas clouds they feed upon. They were, until now. New observations have revealed the earliest “cloaked” black hole ever.”
How do black holes get so big so quickly in this Universe? It’s one of the great mysteries in astrophysics, but the hope has been that better observations of the first billion years of the Universe will help solve this puzzle. If the seeds of black holes can gather enough gas around them to feed on, they just might get there. But the difficultly then comes in locating and finding these obscured, “cloaked” black holes. While they’ve been found relatively nearby, telling us that such a phenomenon does occur, they’ve never been found at very early times: within the first billion years of the Universe.
Ask Ethan: What Has TESS Accomplished In Its First Year Of Science Operations?
“When it’s a bright, sunny day and you want to see an object in the sky that’s very close to the Sun, what do you do? You hold up a finger (or your whole hand) and block out the Sun, and then look for the nearby object that’s much intrinsically fainter than the Sun. This is exactly what telescopes equipped with coronagraphs do.
With the next generation of telescopes, this will enable us to finally directly-image planets around the closest stars to us, but only if we know where, when, and how to look. This is exactly the type of information that astronomers are gaining from TESS. By the time the James Webb Space Telescope launches in 2021, TESS will have completed its first sweep of the entire sky, providing a rich suite of tantalizing targets suitable for direct imaging. Our first picture of an Earth-like world may well be close on the horizon. Thanks to TESS, we’ll know exactly where to look.”
NASA’s TESS has completed its first year of science operations, where it’s just finished surveying the entire southern celestial hemisphere. With 13 separate observations of 27 days apiece, it’s managed to find over 800 candidate planets, including some spectacular examples of planetary systems that are unlike any we’ve ever seen before.
Everyone Missed An Apollo 11 Mistake, And It Almost Killed The Astronauts Returning To Earth
“Fortunately for everyone, they did get lucky. During the technical debriefing in the aftermath of Apollo 11, the fly-by of the Service Module past the Command Module was noted by Buzz Aldrin, who also reported on the Service Module’s rotation, which was far in excess of the design parameters. Engineer Gary Johnson hand-drew schematics for rewiring the Apollo Service Module’s jettison controller, and the changes were made just after the next flight: Apollo 12.
Those first four crewed trips to the Moon — Apollo 8, 10, 11 and 12 — could have all ended in potential disaster. If the Service Module had collided with the Command Module, a re-entry disaster similar to Space Shuttle Columbia could have occurred just as the USA was taking the conclusive steps of the Space Race.”
The flight plan for Apollo 11 was straightforward, if not quite simple. Follow the same trajectory to the Moon that Apollo 8 and Apollo 10 undertook, then successfully enter lunar orbit, launch the Lunar Module, descend to the surface and land softly, perform the scheduled EVA, then ascend back to the Command and Service Module, return to Earth, jettison the Service Module, re-enter, and deploy the parachute to successfully splash down in the Pacific Ocean. Only uncovered well after the mission, there was a huge flaw: the Service Module wasn’t programmed to jettison properly! If things had gone differently, the Command Module could have been damaged, and would have burned up in the atmosphere, killing all on board.
NASA Astronauts And Satellites Capture Breathtaking Images Of An Awakening Volcano From Space
“Volcanoes are some of the most fascinating but also dangerous and deadly natural disasters. Fortunately, with appropriate monitoring, they’re one of the most easily mitigated classes of disasters as well. There are approximately 1,500 potentially active volcanoes on Earth at any time, which doesn’t include undersea volcanoes that have not reached the surface or inactive ones that might surprise us.
Only by continuously monitoring the entire Earth at the appropriate resolutions and cadences can we hope to truly minimize the risk to human life and property. Attempts to cut back on this endeavor harm and endanger us all, while an awareness and appreciation for what Earth observing brings us is our greatest asset. May the beauty of these pictures point the way to the most important truth: that comprehensive knowledge and more information are absolutely key to optimally navigating the challenges of being human on our living planet Earth.”
Just a few days ago, on June 22, 2019, a volcano that hadn’t erupted in nearly a century suddenly sprang to life, belching out waves of ash and volcanic gas high into the stratosphere and posing severe threats to nearby life. But far more at-risk were airplanes, which routinely fly through the region where volcanic ash particles were spewed by this eruption. Due to our full suite of Earth observatories, with an assist from astronauts aboard the International Space Station and ground-based monitoring, we were able to minimize the danger and avoid significant damage. Without NASA’s commitment to Earth monitoring, a commitment that’s continually fighting off attempted cuts, mitigating the risks of volcanic eruptions would be hamstrung by humanity’s greatest danger: willful ignorance.
“Like all known active galaxies, Pictor A is powered by a supermassive black hole many millions to billions of times our Sun’s mass. Black holes can accelerate and eject infalling matter, leading to intense emissions. The light released spans the spectrum from high-energy X-rays to low-energy radio waves. The radio lobes of gas provide a medium for high-energy X-rays to interact with. When these interactions cause electrons to exceed the speed of sound in the gaseous medium, it creates intense shock waves.”
When you have an active galaxy, you can be pretty certain that there’s a supermassive black hole feeding on some matter nearby. If you’ve been paying attention, you’ll know that black holes don’t just devour matter, but that most of the matter that encounters them gets accelerated and ejected instead. This create large lobes of radio-emitting gas around many such galaxies, and in this one in particular, Pictor A, that provides exactly the right environment to create a spectacular feature. X-ray emissions, with energies many times that required to ionize atoms and molecules, slam into that matter, causing it to create free electrons that exceed the speed of sound in that medium. The result is that we get shock waves, and an overall X-ray jet that’s some 300,000 light-years long.
This Is Why Mars Is Red And Dead While Earth Is Blue And Alive
“Both Mars and Earth had early atmospheres that were heavy, massive, and extraordinarily rich in CO2. While Earth’s carbon dioxide got absorbed into the oceans and locked up into carbonate rocks, Mars was unable to do the same, as its oceans were too acidified. The presence of sulfur dioxide led to Martian oceans that were rich in sulfuric acid. This led to geology of Mars we’ve discovered with rovers and landers, and pointed to a different cause — the solar wind — as the culprit in the mystery of the missing Martian atmosphere.
Thanks to NASA’s MAVEN mission, we’ve confirmed that this story is, in fact, the way it happened. Some four billion years ago, the core of Mars became inactive, its magnetic field disappeared, and the solar wind stripped the atmosphere away. With our magnetic field intact, our planet will remain blue and alive for the foreseeable future. But for a smaller world like Mars, its time ran out long ago. At last, we finally know why.”
For most of the 20th century, we knew that Earth had a carbon dioxide-rich past for its atmosphere, but that those atmospheric molecules were deposited into the ocean and precipitated or fossilized out as carbonate rocks like limestone and dolomite. We assumed that Mars, which once had a thick atmosphere and a water-rich surface, lost its atmosphere the same way. But landers and rovers changed all of that, discovering very little in the way of carbonate rocks, meaning that there must have been a different process at play to strip the Martian atmosphere away.