We Have Now Reached The Limits Of The Hubble Space Telescope
“Finally, there are the wavelength limits as well. Stars emits a wide variety of light, from the ultraviolet through the optical and into the infrared. It’s no coincidence that this is what Hubble was designed for: to look for light that’s of the same variety and wavelengths that we know stars emit.
But this, too, is fundamentally limiting. You see, as light travels through the Universe, the fabric of space itself is expanding. This causes the light, even if it’s emitted with intrinsically short wavelengths, to have its wavelength stretched by the expansion of space. By the time it arrives at our eyes, it’s redshifted by a particular factor that’s determined by the expansion rate of the Universe and the object’s distance from us.
Hubble’s wavelength range sets a fundamental limit to how far back we can see: to when the Universe is around 400 million years old, but no earlier.”
The Hubble Space Telescope, currently entering its 30th year of service, has literally revolutionized our view of the Universe. It’s shown us our faintest and most distant stars, galaxies, and galaxy clusters of all. But as far back as it’s taken us, and as spectacular as what it’s revealed, there is much, much more Universe out there, and Hubble is at its limit.
Here’s how far we’ve come, with a look to how much farther we could yet go. It’s up to us to build the tools to take us there.
Cold Dark Matter Is Heated Up By Stars, Even Though It Cannot ‘Feel’ Them
“This effect is what’s known as “dark matter heating.” It isn’t that any of the radiation from the stars or any of the heat from the normal matter is getting transferred to the dark matter itself; it doesn’t involve temperature or energy transfer directly.
Instead, what’s happening is that the additional energy imparted to the normal matter is expelling it from where it was previously the most concentrated: in the galactic center. Once that normal matter is removed from the galactic center, there’s less mass there to hold the dark matter in place, and it, too, has to move to a higher, less-tightly-bound orbit. Because the dark matter gets pushed out and bumped to a higher, more energetic orbit, it has the same effects as though the dark matter was given an extra burst of energy. It’s not actually hotter than it was previously, but the effects are identical.”
Dark matter isn’t supposed to interact with anything. Not with normal matter, not with itself, not with radiation. So how is it, then, that cold dark matter can be heated up by the formation of new stars? Why should that be the solution to the odd distribution of mass in dwarf galaxies?
It actually makes sense, if you reason your way through the physics. Come take that journey, and learn how it actually happens!
This Is How Astronomers Solved The ‘Zone Of Avoidance’ Mystery
“From the time of their very first discovery, the Universe’s grand spirals have puzzled astronomers.
While stars, star clusters and other nebulae were concentrated in the plane of our Milky Way, there were no spiral nebulae present. For some reason, they eschewed our galaxy’s plane, which became known as the Zone of Avoidance.”
On the largest scales of all, the one thing we’re certain we can say about the Universe is that it’s extremely uniform. On average, there are the same number of stars and galaxies, the same sized structure, and the same overall density of matter regardless of where we look. So why, then, would we see spiral and elliptical galaxies in roughly equal abundances, in all directions, except within about 10 degrees of the Milky Way’s plane? For some reason, the galaxies that ought to be there simply aren’t; they appear to avoid the plane of the Milky Way.
This was a mystery for generations, but infrared astronomy, pioneered in the 1960s, paved our path to the epic solution. Come get the incredible 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!
This Is How We Know There Are Two Trillion Galaxies In The Universe
“Over time, galaxies merged together and grew, but small, faint galaxies still remain today. Even in our own Local Group, we’re still discovering galaxies that contain mere thousands of stars, and the number of galaxies we know of have increased to more than 70. The faintest, smallest, most distant galaxies of all are continuing to go undiscovered, but we know they must be there. For the first time, we can scientifically estimate how many galaxies are out there in the Universe.
The next step in the great cosmic puzzle is to find and characterize as many of them as possible, and understand how the Universe grew up. Led by the James Webb Space Telescope and the next generation of ground-based observatories, including LSST, GMT, and the ELT, we’re poised to reveal the hitherto unseen Universe as never before.”
How many galaxies are there in the Universe? If you had asked Carl Sagan a generation ago, the answer might have been something vague, like billions and billions. Just a decade or two ago, people would have guesstimated around 100 billion, as deep surveys from Hubble could give us a count of galaxies both near-and-far in a small region of the sky. But those estimates aren’t necessarily any good, except to serve as lower limits. In order to understand how many galaxies must truly be out there, it requires us to understand both what the Universe is made of and what constitutes a galaxy. Only in the last few years have we reached that level of sophistication, and come up with what we believe, for the first time, is an accurate number.
That number? Two trillion. There are two trillion galaxies in the Universe. This is the story of how we know.
Emojis of the cosmos
Pareidolia is a psychological phenomenon in which the mind responds to a stimulus, usually an image or a sound, by perceiving a familiar pattern where none exists.
These are merely some images of stars and galaxies taken by the Hubble Space Telescope. But what do you see ?
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.