This One Distant, Red, Gas-Free Galaxy Defies Astronomers’ Expectations
“When two similarly-sized galaxies merge, it triggers a starburst: a massive formation of new stars. Under the right circumstances, some gas will form stars while the remainder is expelled, lost forever to the intergalactic medium. Once the gas for forming new stars is used up, the galaxy simply ages as the bluest, most massive stars die off. Over billions of years, only the redder, dimmer, lower mass stars remain.”
In astronomy, young galaxies actively form stars, and glow bright blue through the process. Only after many billions of years and at least one cataclysmic event do galaxies settle down into a gas-free, red state, once all the bluer stars have died out. “Red and dead” galaxies appear in the late Universe, normally as giant elliptical galaxies that lost their gas aeons ago.
Which is why this one galaxy is so puzzling: it’s red, dead, massive and compact, but it’s also sending us its light from 10.8 billion years ago!
How did this galaxy get so old-looking when it’s actually so young? The mystery continues, but here’s what we know so far.
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.
20 Incredible New Images Show How Planets First Form Around Stars
“The best portraits of protoplanetary disks, however, arise from ALMA.
ALMA’s crisp images are striking.
Its Disk Substructures at High Angular Resolution Project (DSHARP) has just released their first results, revealing 20 nearby protoplanetary disks.
Most have gaps, rings, and easily-identifiable locations where candidate planets may lie.”
In theory, there’s a similar cosmic story behind practically every star and solar system that forms. From a nebula, gas collapses, giving rise to a series of proto-stars with protoplanetary disks around them. Those disks develop gaps in them as planetesimals and early planets form, while the growing, heating central star(s) blow off the volatile material. It then becomes a race between gravitation to grow these masses into full-blown planets, mutual interactions which can cause ejections and mergers, and the hot star that can prevent planets from forming if they do so too slowly. For a very long time, this was relegated to pure theory, but observations, particularly in the last 4 years, are not only validating this picture, but showing us how it works.
The DSHARP collaboration has just released their first results, and these 20 new protoplanetary disks are just a hint of the deluge of quality images to come!
We Just Measured All The Starlight In The Universe, And It Spells Doom For Our Future
“An enormous part of our cosmic history has just been revealed for the very first time. We can bypass the foregrounds of our own Solar System, thanks to these gamma-ray signals and how they interact with the extragalactic background of starlight, to understand and measure how star-formation has occurred over all of cosmic time in our Universe, and to infer the total amount of starlight ever produced.
In the future, scientists may be able to go back even farther, and probe how stars formed and emitted light back before the Fermi-LAT team’s instrumentation is capable of reaching. Star formation is what turns the primordial elements from the Big Bang into the elements capable of giving rise to rocky planets, organic molecules, and life in the Universe. Perhaps, one day, we’ll find a way to reach all the way back to the earliest moments of our Universe, uncovering the truths behind the greatest cosmic mysteries of all. Until then, enjoy each and every step — like this one — that we take along the journey!”
For the first time ever, we’ve measured the total amount of starlight ever produced throughout the history of the Universe. We know how many photons, created by stars, now permeate all of space. We know when star-formation peaked, and we know how it’s fallen over time, and how it continues to fall.
Thanks to a new result from the Fermi-LAT collaboration, we understand how star-formation worked, and is dying, across all of space and time. Get the full story today!
What Was It Like When Galaxies Formed The Greatest Number Of Stars?
“The star-formation rate declined slowly and steadily for a few billion years, corresponding to an epoch where the Universe was still matter-dominated, just consisting of more processed and aged material. There were fewer mergers by number, but this was partially compensated for by the fact that larger structures were merging, leading to larger regions where stars formed.
But right around 6-to-8 billion years of age, the effects of dark energy began to make their presence known on the star formation rate, causing it to plummet precipitously. If we want to see the largest bursts of star formation, we have no choice but to look far away. The ultra-distant Universe is where star formation was at its maximum, not locally.”
In a myriad of locations, throughout our galaxy and almost all the galaxies in the known Universe, new stars form wherever a cloud of gas is triggered into collapsing. From the Orion Nebula to dozens of others in our own galaxy, new stars form thousands-at-a-time in regions all throughout our local neighborhood. But as spectacular as these sights are, they’re much, much rarer than they were a long time ago. In fact, we formed stars at a rate that was 30 times faster than today back when the Universe was young. For the last 11 billion years, we’ve been forming fewer and fewer stars everywhere we look.
The Universe is changing even today, and fewer and fewer stars are being newly created as time goes on. There are many reasons why; come learn them today!
Remnants Of Our Solar System’s Formation Found In Our Interplanetary Dust
“Our naive picture of a disk that gets very hot, fragments, and cools to then form planets may be hopelessly oversimplified. Instead, we’ve learned that it may actually be cold, outer material that holds the key to our planetary backyard. If the conclusions of the Ishii et al. paper stand the test of time, we may have just revolutionized our understanding of how all planetary systems come into being.”
How did Earth (and the other planets) form? According to conventional wisdom, a molecular cloud collapsed, formed a protoplanetary disk, funneled material into the center, and gave birth to a star. This star then blew off the gas and light elements from the inner Solar System, with the planets we have today representing the survivors from these hot, early stages. Only, what if that picture weren’t correct after all? What if the material that gave rise to our (and other) worlds wasn’t forged in an inferno, but in a colder, more distant environment that only fell into the inner reaches at a later time?
The way to decide would be to identify and examine material left over from these early stages of Solar System formation in enough detail. For the first time, we’ve done exactly that. Don’t miss the results!
New Stars Turn Galaxies Pink, Even Though There Are No ‘Pink Stars’
“New star-forming regions produce lots of ultraviolet light, which ionizes atoms by kicking electrons off of their nuclei.
These electrons then find other nuclei, creating neutral atoms again, eventually cascading down through its energy levels.
Hydrogen is the most common element in the Universe, and the strongest visible light-emitting transition is at 656.3 nanometers.
The combination of this red emission line — known as the Balmer alpha (or Hα) line — with white starlight adds up to pink.”
When you look through a telescope’s eyepiece at a distant galaxy, it will always appear white to you. That’s because, on average, starlight is white, and your eyes are more sensitive to white light than any color in particular. But with the advent of a CCD camera, collecting individual photons one-at-a-time, you can more accurately gauge an astronomical object’s natural color. Even though new stars are predominantly blue in color, star-forming regions and galaxies appear pink. The problem compounds itself when you realize there isn’t any such thing as a pink star! And yet, there’s a straightforward physical explanation for what we see.
It’s a combination of ultraviolet radiation, white starlight, and the physics of hydrogen atoms that turn galaxies pink. Find out how, with some incredible visuals, today!
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.
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!