- 2972 - DARK ENERGY - with Nancy Grace? A new NASA space observatory could push planet-hunting forward at warp speed by gathering data up to 500 times faster than the venerable Hubble Space Telescope does. The “Nancy Grace Roman Space Telescope” (formerly known as the Wide-Field Infrared Survey Telescope or WFIRST) passed a key ground-system design review this month, according to NASA.
--------------------- 2972 - DARK ENERGY - with Nancy Grace?
- “Roman“ relies on technology that was originally built for spy missions on Earth. Instead, after its launch in the mid-2020s, Roman will spy on exoplanets across the galaxy, as well as many other cosmic phenomena.
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- Roman will be optimized for a kind of planetary survey called “microlensing“, which is an observational effect that happens when mass warps the fabric of space-time. At its most extreme, this kind of gravitational lensing is used to observe very massive objects such as galaxies or blackholes. In miniature microlensing creates enough "warping" in smaller stars and planets for planet-hunting.
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- At this smaller scale, microlensing happens when one star aligns closely with a second star, from the vantage point of Earth. The star that is closer to our planet focuses and amplifies the light from the star that is further away, allowing scientists to see it in a little more detail than usual. Even planets that are orbiting the foreground star can magnify the star's light, creating a spike in brightness.
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- Roman's microlensing capabilities will be coupled with a wide field of view that is 100 times larger than Hubble's, while capturing stars and planets with the same resolution as the famed telescope. Roman is expected to pick up more data than any of the agency's other astrophysics missions.
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- The past “Kepler” mission had found thousands of exoplanets and the current “Transiting Exoplanet Survey Satellite (TESS)” is looking for Earth-like planets close to us.
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- Hubble, while not designed for planet-hunting since it launched just when discoveries were beginning, has done plenty of exoplanet science as well. Numerous observatories on Earth have found their own planets or confirmed observations made by space telescopes, creating a larger community of exoplanet science that Roman will contribute to after its launch.
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- Each one observation will have a unique signature, which we can use to determine the planet's mass and distance from its star.
Gathering the data is one challenge. Parsing and understanding the information for discoveries and "lessons learned" is another. The ground systems supporting Roman will rely on cloud-based remote services and advanced analytical tools to make sense of the enormous amounts of data the telescope collects
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- Roman's design calls for the telescope to watch hundreds of millions of stars every 15 minutes for several months at a stretch. Another notable change from previous flagship missions is the speed at which Roman's data will become public; NASA has promised to make all data available only days after observations are collected.
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- Since scientists everywhere will have rapid access to the data, they will be able to quickly discover short-lived phenomena, such as supernova explosions. Detecting these phenomena quickly will allow other telescopes to perform follow-up observations.
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- Exoplanets and supernovas are not the only things Roman will discover. It will hunt for brown dwarfs, which are "failed stars", objects much more massive than Jupiter that are not quite large enough to sustain nuclear fusion.
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- Other expected astronomy targets include runaway stars and bizarre cosmic objects such as the neutron stars and blackholes that are left behind when stars run out of fuel.
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- Astronomers will be trying to figure out the nature of “dark matter” and “dark energy“, which is impossible to observe except through monitoring effects on other objects. Roman's observations will allow the telescope collect precise measurements from numerous galaxies, mapping the distribution and structure of regular matter and dark matter across the universe's history.
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- Roman's work in dark energy and dark matter could help scientists understand why the universe is expanding, and why that expansion is accelerating as the universe gets bigger.
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- Another Roman partnership with its predecessor will be follow up on Hubble's Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). This survey charted how galaxies develop over time; Hubble took 21 days to gather the information, but Roman will only take half an hour to conduct a similar investigation.
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- With its incredibly fast survey speeds, Roman will observe planets by the thousands, galaxies by the millions, and stars by the billions. These vast datasets will allow us to address cosmic mysteries that hint at new fundamental physics."
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- We don't know the fundamental physics as to what's behind dark energy that is creating the current era of accelerated expansion in the universe. Many theorists favor some sort of quantum field as the driver of dark energy, but these ideas are hard to reconcile with insights from “string theory“.
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- But new research proposes a radical solution: What if there is more than one cosmological agent for dark energy? This mixture would have strange effects in our universe, making it potentially detectable with upcoming surveys. Into the darkness we go. Not only do we live in an expanding universe with Edwin Hubble's observations of galaxies receding away from us, but, we live in a universe whose expansion is “accelerating“. For about the past 5 billion years, the expansion rate of our cosmos has been increasing, ramping up the growth of the universe with every passing day.
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- To put it mildly, we have no idea what's causing this accelerated expansion. We first noticed it about 20 years ago when studying distant supernovae, and since then a plethora of independent observations including the cosmic microwave background, baryon acoustic oscillations, cosmic voids and more, have all confirmed that accelerated expansion is the real deal.
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- Even though we don't know what dark energy is, over the years theorists have made some feeble attempts to potentially explain it.
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- One of the most attractive ideas floating around out there is that there is some sort of quantum field that is responsible for dark energy and keeping the pedal to the cosmological metal.
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- Quantum fields soak every bit of space-time and are responsible for generating the forces and particles that make up our everyday existence — and so it's not so crazy to imagine that there's a new quantum field (one never before known to science) that has just the right properties to trigger accelerated expansion.
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- So, maybe dark energy is caused by some quantum field that soaks all of space-time. While it does indeed sound a) simple and b) attractive, there are some downsides to this hypothesis.
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- String theory is an attempt to unite all the forces of nature under one mathematical theory of everything. In string theory, every particle and every force is really a manifestation of super-duper tiny vibrating strings. But to explain all the richness and variety of the physical universe, these strings can't just vibrate in three dimensions.
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- To make string theory work, our universe needs a few extra dimensions, all tiny and curled up on themselves, where the strings can do their business and give rise to physics. This all happens at the tiniest of scales, which is why we haven't noticed it yet.
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- One of the biggest headaches facing string theory, and why it isn't a complete theory of nature, is that we have no idea how those extra dimensions are curled up. There could be as many as 10^200 possible configurations, and each configuration of curled-up dimensions gives a new set of physics. Since we only live in one universe with one set of physics, only one of these configurations can be ours. But which one?
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- String theorists have made some attempts to separate the stringy wheat from the chaff, and at least reject some potential configurations of the curled-up dimensions as Definitely Not This Universe.
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- One problem: at first glance, it seems like universes that allow for dark energy as caused by a quantum field aren't compatible with other things we know about string theory. Dark energy seems to live in the "swampland," the possible configurations of curled-up dimensions that simply don't work.
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- Or maybe, it could be that there isn't just one quantum field responsible for dark energy, but several working together in concert. This isn't as crazy as it may seem; remember that nature is under no obligation to be simple and straightforward.
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- By allowing for multiple quantum fields to generate dark energy, it might be possible for string theory to still be relevant in our universe, as these models may not be stuck in the "swampland."
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- But that means we have to find evidence that there is more than one agent responsible for dark energy. It turns out that in these models of multiple dark energy, it's possible for dark energy to clump up on itself, meaning you can travel around the universe and find patches of less-than-average and greater-than-average dark energy.
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- In total, across the cosmos, the large-scale effect is still the same accelerated expansion, but an excess of dark energy here or a deficit there could affect how the biggest structures in the universe, like clusters of galaxies and the great cosmic voids, grow and evolve.
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- We don't yet have the sensitivity to measure these differences, but future experiments like NASA's Nancy Grace Roman Space Telescope could provide some insights, helping us to determine if we really do live in the “swampland” or not.
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January 10, 2021 DARK ENERGY - with Nancy Grace 2972
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