One Of These Four Missions Will Be Selected As NASA’s Next Flagship For Astrophysics
“Choosing which of these missions to build and fly will, in many ways, inform our plans for the next 30 years (or more) of astronomy. NASA is the pre-eminent space agency in the world. This is where science, research, development, discovery, and innovation all come together. The spinoff technologies alone justify the investment, but that’s not why we do it. We are here to discover the Universe. We are here to learn all that we can about the cosmos and our place within it. We are here to find out what the Universe looks like and how it came to be the way it is today.
People will always argue over budgets — the penny-pinchers are always happy to propose something that’s faster, cheaper, and worse — but the reality is this: the budget for NASA Astrophysics as a whole is just $1.35 billion per year: less than 0.1% of the federal discretionary budget and less than 0.03% of the total federal budget. And still, for that tiny amount, NASA has steadily built a flagship program that’s the envy of the free world.”
Every 10 years, NASA performs a decadal survey, where it outlines its highest mission priorities for the next 10 years. The 2020 decadal is happening imminently, and once the recommendations are submitted to the National Resource Council at the National Academies of Science, the four flagship finalists will be ranked. This will determine NASA astrophysics’ direction for the 2030s.
James Webb is the flagship for the 2010s; WFIRST is it for the 2020s. What will we choose for the 2030s? It will be one of these four finalists! Dream big, everyone.
This Is What’s Special About A Full Supermoon Occurring On The Equinox This Year
“You may remember that two months ago, in January, we received a total lunar eclipse: where the Sun, Earth, and full Moon were perfectly aligned. Now that it’s two months later, the full Moon is misaligned, because the plane that the Moon orbits the Earth in is tilted with respect to the Sun.
This is incredible for science! On any old equinox, you can measure your latitude on Earth; on any solstice, you can measure the axial tilt of the Earth. Well, on an equinox that coincides with a full Moon, you can measure how far out of the Sun-Earth plane the Moon actually is at this particular moment in time. And if you know when the last eclipse was and the next eclipse will be, you can actually determine the tilt of the Moon’s orbit. Here’s how.”
If you had a perfectly vertical stick on the day of the equinox, by measuring the shadow it casts when the Sun reaches its highest point above the horizon, you can measure your latitude. Yet that very night, when we have a full Moon, measuring the same shadow on the same object will give you a very different answer, by a little more than 4 degrees.
The reason is because the Moon’s orbit is tilted with respect to the Earth-Sun plane.
This is brilliant! Make that measurement yourself, and you can calculate the Moon’s orbital tilt for yourself. Here’s how.
Could The Milky Way Be More Massive Than Andromeda?
“The Milky Way is home to the Sun, our Solar System, and hundreds of billions of stars beyond that. Yet unlike all the other galaxies out there — in our Local Group and in the Universe beyond — we have no good way to view our own galaxy from our position within it. As a result, the full extent of our galaxy, including its total size, mass, matter content, and number of stars, remains mysterious to modern astronomers.
We’ve long looked at the galaxies surrounding our local neighborhood in space and compared ourselves to them. Although there may be more than 60 galaxies present within the Local Group, two of them dominate in every way imaginable: ourselves and Andromeda. We are the two largest, most massive galaxies around, with more stars than all the others combined. But which one is bigger? Long thought to be Andromeda, we’re now finding out the Milky Way might have a chance at being number one.”
It’s 2019, and we still don’t know how massive the Milky Way is, or even whether we’re the most massive galaxy in the Local Group or not. It’s a lot like measuring your eye color: looking out at everyone else, it’s easy to see what color their eyes are. But if you didn’t have a reflection, photograph, or the observations of others, how would you know your own eye color? Well, being trapped within the Milky Way makes measurements notoriously difficult, and we’re only now figuring out how to overcome that obstacle.
It’s not only possible, but even likely that the Milky Way, despite having fewer stars occupying less volume than Andromeda’s, is the most massive galaxy in the Local Group. Come get the full story.
Happy Birthday To Urbain Le Verrier, Who Discovered Neptune With Math Alone
“The other planets dutifully followed the laws of planetary motion, but Uranus appeared to violate them. Breaking Kepler’s laws, Uranus moved too quickly for decades, then at the right speed, then too slowly. The observations weren’t easily dismissable, but their physical cause was unknown. An additional planet beyond Uranus, gravitationally tugging on it, offered a potential solution. Determining the mass, orbital parameters, and location of an unseen world presented incredible calculational challenges.”
On March 11, 1811, Urbain Le Verrier was born. As a mathematician of tremendous skill in France, he had only a passing initial interest in astronomy, until the 1840s, when the influential François Arago suggested that he take up the puzzle of Uranus’ orbit, which appeared to violate the laws of planetary motion. Le Verrier theorized that if there were an outer planet beyond Uranus with the right mass and orbital parameters, it could cause these observed orbital anomalies. On August 31, 1846, Le Verrier composed a letter detailing his predictions and sent it to the Berlin Observatory. On September 23, the letter arrived. That very night, the portion of the sky where Le Verrier claimed a new planet should be was clear, and less than one degree away from his location, there it was: the planet Neptune.
Arago immortalized Le Verrier as the man who discovered a planet with the point of his pen. It remains an astronomical achievement of the highest order.
Ask Ethan: If The Universe Ends In A Big Crunch, Will All Of Space Recollapse?
“When you describe the Big Crunch, you talk about a race between gravity and the expansion of space. It’s not clear to me that if gravity wins that race, whether space stops expanding, or simply that the matter in space stops expanding. I’d love to hear your explanation of this.”
The Universe is expanding, and we can confirm this by looking at the relationship between how redshifted a galaxy’s light is compared with how far away it is from us. But if these galaxies, at some point in the far future, stop being redshifted and start moving closer and closer to us again, does that necessarily mean that the fabric of space is contracting? Is all of space necessarily recollapsing? Or could the galaxies simply be moving towards us, owing to some massive attraction, while the fabric of space doesn’t recollapse at all? Does a Big Crunch necessarily equate to a recollapsing Universe?
Even though we don’t know whether dark energy will reverse itself or not, we do know the answer to this question, and yes, a Big Crunch does mean recollapse! Find out why on this edition of Ask Ethan.
How Much Of The Dark Matter Could Neutrinos Be?
“If we restrict ourselves to the Standard Model alone, we simply cannot account for the dark matter that must be present in our Universe. None of the particles we know of have the right behavior to explain all of the observations. We can imagine a Universe where neutrinos have relatively large amounts of mass, and that would result in a Universe with significant quantities of dark matter. The only problem is that dark matter would be hot, and lead to an observably different Universe than the one we see today.
Still, the neutrinos we know of do behave like dark matter, although it only makes up about 1% of the total dark matter out there. That’s not totally insignificant; it equals the mass of all the stars in our Universe! And most excitingly, if there truly is a sterile neutrino species out there, a series of upcoming experiments ought to reveal it over the next few years. Dark matter might be one of the greatest mysteries out there, but thanks to neutrinos, we have a chance at understanding it at least a little bit.”
Dark matter is a form of matter that gravitates, but neither absorbs nor emits light, and has been frustratingly difficult to pin down and directly detect. There’s a known particle that has exactly those same properties: the neutrino! You might wonder, then, if perhaps neutrinos had the right value of mass and number, if they could make up the dark matter? And if not all of it, could they at least make up part of it? This is a question that astronomers and physicists have pondered for decades, and we might be closer than ever to the actual answer.
How much of the dark matter can neutrinos actually be? Find out today!
What Was It Like When Planet Earth Took Shape?
“There was almost certainly a high-energy collision with a foreign, out-of-orbit object that struck our young Earth in the early stages of the Solar System, and that collision was required to give rise to our Moon. But it was very likely much smaller than Mars-sized, and it was almost certainly a sturdy strike, rather than a glancing collision. Instead of a cloud of rock fragments, the structure that formed was a new type of extended, vaporized disk known as a synestia. And over time, it settled down to form our Earth and Moon as we know them today.
At the end of the early stages of our Solar System, it was as promising as it could be for life. With a central star, three atmosphere-rich rocky worlds, the raw ingredients for life, and with gas giants only existing much further beyond, all the pieces were in place. We know we got lucky for humans to arise. But with this new understanding, we also think the possibility for life like us has happened millions of times before all throughout the Milky Way.”
One of the deepest existential questions we can ask about the Universe is how, after more than 9 billion years, all the phenomena in our cosmic history led to the creation of planet Earth. Going from an environment where stars were actively forming to one where the Sun, Earth, and all the other planets were in place is a daunting task for people who create scientific simulations of our early environment, and involves gravitational interactions, planetary migrations and ejections, and even enormously energetic collisions between planets and proto-planets.
Yet somehow, it all came together, and gave rise to us. From what we’re learning, we might not even be all that rare. Come check out the current story.
What Was It Like When Our Solar System First Formed?
“Over the past few years, we’ve finally been able to observe solar systems in these very early stages of formation, finding central stars and proto-stars shrouded by gas, dust, and protoplanetary disks with gaps in them. These are the seeds of what will become giant and rocky planets, leading to full-on solar systems like our own. Although most of the stars that form — including, very likely our own — will have formed amidst thousands of others in massive star clusters, there are a few outliers that form in relative isolation.
Although the history of the Universe may subsequently separate us from all of our stellar and planetary siblings from the nebula that they formed in billions of years ago, scattering them across the galaxy, our shared history remains. Whenever we find a star with approximately the same age and abundance of heavy elements as our Sun, we cannot help but wonder: is this one of our long-lost siblings? The galaxy is likely full of them.”
It took a whopping 9.2 billion years of cosmic evolution for the Universe to give rise to the very beginning of our Solar System; our Sun and planets didn’t form until 2/3rds of the time since the Big Bang had passed. In order to get there, we needed to form the right ingredients for life, rocky planets, and the chemistry we need. But when it happened to us, we weren’t alone. It likely happened exactly the same way for thousands of other stars at once, and continues to happen even up through the present day.
Are we alone in the Universe? The cosmic story that brought us to existence seems to be a story that’s universal. Here’s a key step in how we got here.
This Massive Black Hole Is Mysteriously Quiet, And Astronomers Don’t Know Why
“Messier 51, the Whirlpool Galaxy, is one of astronomy’s most spectacular objects. This enormous, face-on galaxy was the first one ever to reveal its spiral structure. The small object alongside it, the galaxy NGC 5195, is interacting and merging with the Whirlpool galaxy. Such mergers trigger new waves of star formation, create grand spiral arms, and activate supermassive black holes.”
That’s the theory, at any rate. Yet when we look at Messier 51, located just outside of the Big Dipper in the night sky, we find that the X-rays being emitted from it are spectacularly minimal. After the Chandra X-ray telescope made its observations, we simply assumed the higher-energy X-rays would make up for the missing radiation, but they show an extreme shortage as well, with neutron stars on the outskirts outshining them.
Perhaps something new is at play. Perhaps active black holes flicker on-and-off faster than we previously thought. There’s a new puzzle, and that means there’s more to learn.
Scientists Celebrate Pluto’s Discovery With A Retrospective Of Its Greatest Images
“In 1978, our telescopes had advanced enough to determine that it had a large satellite: the giant moon Charon. Through occultations of distant stars, we determined Pluto had an atmosphere that changed over time, growing larger near perihelion. 1994 saw the first optically-corrected pictures of the Pluto-Charon system by Hubble, the first image to resolve these worlds independently.”
On this date in 1930, the first world beyond Neptune in our Solar System was discovered. Now known as Pluto, our images and understanding of it have progressed dramatically through the years. It is one of nature’s most fascinating objects, and our ever-improving sights of the world are only eclipsed by the scientific knowledge we’ve continued to glean. It’s the largest object in all the Kuiper belt with five moons of its own, and it tells a story unique in all the Universe.
Come celebrate Pluto’s discovery with a retrospective of its greatest images, and our greatest science hits (so far) today!