Hubble Catches New Stars, Individually, Forming In Galaxies Beyond The Milky Way
“There are a massive variety of star-forming regions nearby, and Hubble’s new Legacy ExtraGalactic UV Survey (LEGUS) is now the sharpest, most comprehensive one ever.
By imaging 50 nearby, star-forming spiral and dwarf galaxies, astronomers can see how the galactic environment affects star-formation.”
Within galaxies, new stars are going to be formed from the existing population of gas. But how that gas collapses and forms stars, as well as the types, numbers, and locations of the stars that will arise, is highly dependent on the galactic environment into which they are born. Dwarf galaxies, for example, tend to form stars when a nearby gravitational interaction triggers them. These bursts occur periodically, leading to multiple populations of stars of different ages. Spirals, on the other hand, form their new stars mostly along the lines traced by their arms, where the dust and gas is densest. Thanks to the Hubble Space Telescope, we’re capable of finding these stars and resolving them individually, using a combination of optical and ultraviolet data.
The best part? These are individually resolved stars from well outside our own galaxy: in 50 independent ones. Here’s what Hubble’s new LEGUS survey is revealing.
Ask Ethan: Will Future Civilizations Miss The Big Bang?
“If intelligent life re-emerges in our solar system in a few billion years, only a few points of light will still be visible in the sky. What kind of theory of the universe will those beings concoct? It is almost certain to be wrong. Why do we think that what we can view now can lead us to a “correct” theory when a few billion years before us, things might have looked completely different?”
Incredibly, the Universe we know and love today won’t be the way it is forever. If we were born in the far future, perhaps a hundred billion years from now, we wouldn’t have another galaxy to look at for a billion light years: hundreds of times more distant than the closest galaxies today. Our local group will merge into a single, giant elliptical galaxy, and there will be no sign at all of young stars, of star-forming regions, of other galaxies, or even of the Big Bang’s leftover glow. If we were born in the far future, we might miss the Big Bang as the correct origin of our Universe. It makes one wonder, when you think about it in those terms, if we’re missing something essential about our Universe today? In the 13.8 billion years that have passed, could we already have lost some essential information about the history of our Universe?
And in the far future, might we see something that, as of right now, hasn’t yet grown to prominence? Let’s explore this and see what you think!
Astronomers Confirm Second Most-Distant Galaxy Ever, And Its Stars Are Already Old
“Scientists have just confirmed the second most distant galaxy of all: MACS1149-JD1, whose light comes from when the Universe was 530 million years old: less than 4% of its present age. But what’s remarkable is that we’ve been able to detect oxygen in there, marking the first time we’ve seen this heavy element so far back. From the observations we’ve made, we can conclude this galaxy is at least 250 million years old, pushing the direct evidence for the first stars back further than ever.”
When it comes to the most distant galaxies of all, our current set of cutting-edge telescopes simply won’t get us there. The end of the cosmic dark ages and the dawn of the first cosmic starlight is a mystery that will remain until at least 2020: when the James Webb Space Telescope launches. Using the power of a multitude of observatories, we’ve managed to find a gravitationally lensed galaxy whose light comes to us from over 13 billion years ago. But unlike previous galaxies discovered near that distance, we’ve detected oxygen in this one, allowing us to get a precise measurement and to estimate its age.
For the first time, we have evidence from galaxies, directly, that the Universe’s first stars formed no later than 250 million years after the Big Bang. Here’s how we know.
Aliens In The Multiverse? Here’s Why Dark Energy Doesn’t Tell You Anything
“It’s important to recognize that there are a wide variety of possible values that dark energy could have, including significantly larger values, that would still lead to a Universe very much like our own. Until we understand where these values come from, and what makes one set of values more likely than another, it’s grossly unfair to claim that we won the cosmic lottery in having a Universe with the values ours possesses. Unless you know the rules that govern the game you’re playing, you have no idea how likely or unlikely the one result you see actually was.”
There are a series of interesting results that have just emerged from the EAGLE collaboration, which has been simulating the Universe to learn what types of stars and galaxies form within it. They varied the value of dark energy in it tremendously, and found that even if you increased the amount by five, ten, or fifty times as much, you’d still form plenty of stars and galaxies: enough to give you chances at life like we have here. This surprised them, since they assumed the value of dark energy we have is finely-tuned to allow life. But it appears that things may not be as finely-tuned as we had thought! The simulation results are interesting, but this doesn’t really tell you anything about aliens in the Multiverse, since we have no idea what causes dark energy to have the values that it does.
Until we know the rules that govern this, we can’t really say what dark energy tells us about aliens in Universes other than our own. Here’s why.
Humanity’s 3 Hopes For Finding Alien Life
“Although it’s just conjecture at this point, scientists speculate that life in the Universe is probably common, with the ingredients and opportunities for it to arise appearing practically everywhere. Life that thrives and sustains itself on a world, to the point where it can change its atmospheric and/or surface properties, may need to get lucky, and is likely more uncommon. Evolving to become complex, differentiated, multicellular creatures is likely even rarer. And as far as becoming what we would consider an intelligent, technologically advanced civilization, it could be so exceedingly remarkable that in all the Universe, it might just be us. Yet despite how different these outcomes are, we’re actively searching for all three types of life in very different ways. When the first sign of alien life finally is discovered, which one shall emerge victorious?
No matter which method pays dividends first, it will be among the greatest day in the history of life on Earth.”
There are three very different ways humanity is searching for alien life beyond Earth. We can directly search the various planets and moons in our Solar System for past or present biological signatures simply by sending decontaminated probes, and looking for the evidence in situ. We can indirectly look at distant worlds around other stars, searching for the characteristic changes to the atmosphere and surface that life would bring. And, most optimistically, we can search for intelligent signatures created, perhaps willfully, by a technologically advanced alien species.
These are our three hopes for finding alien life, and we’re actively pursuing all three. Which one, if any, do you think has the best chance of paying off?
Ask Ethan: How Many Galaxies Have Already Disappeared From Our Perspective?
“So how many earth observable galaxies have dropped out of sight? That is, how many galaxies (with the highest redshift) have disappeared from our point of view?”
When we look out at the distant reaches of space, there are some 2 trillion galaxies observable within our Universe. But our Universe is expanding, the expansion is accelerating, and light can only travel at the speed of light. Does that mean that galaxies are dropping out of sight?
There are two ways to look at this: from the point of view of not being able to see galaxies that we can presently see, and from the point of view of whether we can see the light those galaxies are emitting today, 13.8 billion years after the Big Bang? If we take the first definition, not only is the answer “zero,” but there will be trillions more galaxies revealed to us over time. But if we take the second, we find that most of the galaxies we can see today are already gone.
How many galaxies have already disappeared from our perspective? The cosmic implications should motivate us to get out there and explore while there’s still some good Universe left to go and see!
Mysterious Light Seen Around A Newly Forming Star; Here’s What Astronomers Think It Means
“In order to reproduce the signatures we see, the disk has to be practically edge-on to our line of sight. Which seems weird, because the main binary system that is CS Cha has a disk that’s inclined, somewhere between edge-on and face-on. This wouldn’t be the first time we’ve seen such a misalignment, as dusty, misaligned binary and trinary systems have been seen before. But it already marks the very first time we’ve detected a polarized companion outside of one of these protoplanetary disks! Because so much of the light is blocked by this dust disk, though, we have a hard time telling what the mass of this companion is. Is it a Jupiter-class planet? A super-Jupiter? Or, as the authors conjecture, is it a low-mass brown dwarf: a failed star?
With a dusty disk around the companion, there’s a near-certainty that whatever it is, it will be developing its own orbiting companions in the imminent future!”
600 light years away, in a small constellation in the southern skies, there’s a new binary star system that’s just in the process of forming: CS Cha. It’s only 2 or 3 million years old, a blip in a star’s lifetime. And all around it for billions of kilometers is a dusty, protoplanetary disk. But far outside that disk is a surprise: a companion object. Most companions will be either large planets or brown dwarfs, and that’s not a surprise. But when you look at the light, it should barely be polarized at all: 1% at most. Yet when we looked at the companion with SPHERE, a new instrument aboard the Very Large Telescope in Chile, we found that a whopping 14% of the light was polarized!
This was no mistake, but the implications are tremendous. After some very careful research, scientists think they know the answer to what’s going on: there’s a dusty disk around the companion object, too!
How Does Our Earliest Picture Of The Universe Show Us Dark Matter?
“So all you need to do, to know whether your Universe has dark matter or not, is to measure these temperature fluctuations that appear in the CMB! The relative heights, locations, and numbers of the peaks that you see are caused by the relative abundances of dark matter, normal matter, and dark energy, as well as the expansion rate of the Universe. Quite importantly, if there is no dark matter, you only see half as many total peaks! When we compare the theoretical models with the observations, there’s an extremely compelling match to a Universe with dark matter, effectively ruling out a Universe without it.”
If your young Universe is full of matter and radiation, what happens? Gravitation works to pull matter into the overdense regions, but that means that the radiation pressure must rise in those regions, too, and that pushes back against the matter. On small scales, this pushback washes out the gravitational growth, but on large-enough scales, the finite speed that light can travel means that no wash-out can happen. Dark matter, however, doesn’t collide with radiation or normal matter, while normal matter collides with both radiation and itself. If we can calculate exactly how these three species interplay, we can calculate what types of patterns we expect to see in the Big Bang’s leftover glow, and then compare it with what we observe with satellites like WMAP and Planck. And what have we seen, exactly, when we’ve done that?
We see that the Universe must contain dark matter to explain the observations. No alternative theory can match it.