Monthly Archives: October 2019

Now, a team of astronomers has spotted one of these early galaxies in the act of churning out stars. Their observations capture the galaxy, which is about the size of the Milky Way, as it was about 1 billion years after the Big Bang. However, the galaxy is creating roughly 300 Suns worth of stars per year, while the Milky Way forms just one or two solar masses of stars each year.

The team says their find is something of a cosmic yeti because astronomers previously dismissed the idea that such monster early galaxies ever existed.

The researchers reported their find Tuesday in The Astrophysical Journal.

The researchers looked at other images of this patch of sky and discovered faint traces of the galaxy in various wavelengths of light. Those traces by themselves were too faint for anyone to be sure there was a galaxy there. But combined with the much clearer and brighter ALMA data, the researchers could be more confident that those traces of light came from the same galaxy. From the traces of light the researchers gathered, they were able to infer how fast the galaxy is building up its store of stars.

Because the researchers stumbled upon the galaxy by accident in a fairly small patch of sky, they believe these quickly star-forming galaxies arent rare.

The fact that weve been able to find one object and that its relatively common that makes me excited for future surveys, Williams said. Hopefully, we will find more, and then well be able to measure the formation histories of these things better with future data.

The newly discovered galaxy is part of the puzzle of how such massive galaxies formed so early in the universe. Before long, Williams hopes, astronomers will find more pieces of the puzzle and create a more complete picture of galaxies throughout the universes history.

View post:

This monster galaxy made stars hundreds of times faster than the Milk - Astronomy Magazine

Sunday, October 27Uranus reaches opposition and peak visibility tonight. Opposition officially arrives at 4 a.m. EDT on the 28th, when the outer planet lies opposite the Sun in our sky. This means it rises at sunset, climbs highest in the south around 1 a.m. local daylight time, and sets at sunrise. (From 40 north latitude, Uranus peaks at an altitude of 63, the highest it has appeared at opposition since February 1962.) The magnitude 5.7 planet lies among the background stars of southern Aries. In the nights around opposition, you can find it 3 south-southwest of the similarly bright star 19 Arietis.. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. A telescope reveals the planets blue-green disk, which spans 3.7". To learn more about viewing Uranus and its outer solar system cousin, Neptune, see Observe the ice giants in Octobers Astronomy.

New Moon occurs at 11:38 p.m. EDT. At its New phase, the Moon crosses the sky with the Sun and so remains hidden in our stars glare.

Monday, October 28Although the Orionid meteor shower peaked last week, the shower remains active until November 7. And with the Moon now gone from the night sky, observers can expect to see a few shooting stars in the predawn sky. To differentiate an Orionid from a sporadic, remember that a shower meteor will appear to radiate from the northern part of the constellation Orion the Hunter.

Tuesday, October 29The solar systems two inner planets appear near each other in the early evening sky. Tonight, Mercury slides 3 due south (lower left) of Venus. You can find the pair with the help of a two-day-old crescent Moon. Our satellite stands 8 high 30 minutes after sunset with Venus 5 to its lower right and Mercury 6 directly below the Moon. All three objects should just fit in the field of view through 7x50 binoculars. At magnitude 3.8, Venus shines far brighter than magnitude 0.1 Mercury.

Wednesday, October 30This week offers an excellent opportunity to view the zodiacal light. From the Northern Hemisphere, early autumn is the best time of year to observe this elusive glow before sunrise. It appears slightly fainter than the Milky Way, so youll need a clear moonless sky and an observing site located far from the city. Look for the cone-shaped glow, which points nearly straight up from the eastern horizon, shortly before morning twilight begins (around 6 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until November 11, when its bright light will return and overwhelm the much fainter zodiacal light.

Thursday, October 31Use the waxing crescent Moon as a guide to finding Jupiter in the southwestern sky this evening. You can find Jupiter 5 to Lunas lower right as darkness falls. Of course, Jupiter is on display all week. It shines at magnitude 1.9 and dominates the early evening sky from its perch in southern Ophiuchus the Serpent-bearer. When viewed through a telescope, Jupiter shows a 33"-diameter disk with striking details in its dynamic atmosphere. You also should see four bright points of light arrayed around the planet: the Galilean moons Io, Europa, Ganymede, and Callisto.

Friday, November 1The Moon moves about 13 eastward relative to the background stars each day, and this movement carries it into Saturns vicinity this evening. Look for the ringed planet 4 to Lunas upper left. As with Jupiter, Saturn remains a glorious sight all week. The ringed planet resides among the background stars of Sagittarius the Archer, a region that appears 20 high in the southwest as twilight fades to darkness and doesnt set until 10 p.m. local daylight time. Saturn shines at magnitude 0.6 and appears significantly brighter than any of its host constellations stars. Although a naked-eye view of the planet is nice, seeing it through a telescope truly inspires. Even a small instrument shows the distant worlds 16"-diameter disk and spectacular ring system, which spans 36" and tilts 25 to our line of sight.

Saturday, November 2After a three-month hiatus, Mars returns to view before dawn this week. You can find it 8 above the eastern horizon an hour before the Sun rises. The Red Planet shines at magnitude 1.8 and should be obvious through binoculars. Once you find the ruddy world, try to spot it with just your naked eye.

See the original post here:

The Sky This Week from October 25 to November 3 - Astronomy Magazine

This artist's impression of an early, massive galaxy that forms from the merger of... [+] smaller-protogalaxies shows how it should be obscured by dust during the most rapid phases of star-formation. For the first time, a team of astronomers may have discovered the missing link between the earliest and the later, more massive galaxies that we see.

One of the greatest challenges for a scientist is that every time you make a new advance, it only raises more questions. When we look out at our Universe today, we see galaxies with all sorts of different properties. We see giant ellipticals that haven't formed stars in billions of years; we see Milky Way-like spirals that are rich in heavy elements; we see irregular galaxies; we see dwarf galaxies; we see ultra-distant galaxies that appear to be forming stars for just the first or second time.

But when you put this all together, there are some puzzles. Some galaxies have grown to be so large soearly that they've defied a coherent explanation. With only small, low-mass galaxies found at great distances by Hubble, the active formation of a large galaxy has long been astronomy's missing link. With a new discovery of a dark, massive galaxy, astronomers may have just cracked the mystery, and solved a longstanding cosmic puzzle.

Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky... [+] Way-like are inherently smaller, bluer, more chaotic, and richer in gas in general than the galaxies we see today. For the first galaxies of all, this ought to be taken to the extreme, and remains valid as far back as we've ever seen. There is an unexplained gap between the earliest proto-galaxies and the first large galaxies that astronomers have struggled to explain.

To understand how galaxies form and grow up in our Universe, it's always best to start at the very beginning. Cosmologists have assembled a comprehensive and coherent picture of the Universe, and if we trace out how that Universe evolves and grows from its humble beginnings to the cosmos we inhabit today, we should be able to come up with a story that tells us what we ought to see.

The Universe, in the aftermath of the Big Bang (post-inflation), arrives on the scene with the seeds for our modern-day galaxies already planted. Our Universe is hot, dense, expanding, and filled with matter, antimatter, dark matter and radiation. It's also born almost perfectly uniform, but with tiny density imperfections in it. On all scales, the densest regions are just a few parts-in-100,000 denser than average, but that's all the Universe needs.

The largest-scale observations in the Universe, from the cosmic microwave background to the cosmic... [+] web to galaxy clusters to individual galaxies, all require dark matter to explain what we observe. The large scale structure requires it, but the seeds of that structure, from the Cosmic Microwave Background, require it too.

As the Universe expands and cools, the regions that have slightly more matter (normal and dark combined) than others will begin to preferentially attract more and more of the matter from surrounding regions towards it. As time goes on, radiation becomes less important, and these matter imperfections can grow at a faster rate as they continue to grow in density.

Although it takes somewhere between 50 and 100 million years for the very first region in the Universe to become dense enough to form stars, that's just the start of the story. These first stars, once they start turning on, herald the arrival of energetic, ultraviolet photons that start streaming through the Universe. Over time, as stars form in more and more locations, the neutral atoms throughout space begin to be reionized, as the Universe slowly becomes transparent to visible light.

The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from... [+] 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. But there are even more distant galaxies out there, and we all hope that the James Webb Space Telescope will discover them.

At around 200-250 million years after the Big Bang, the first galaxies begin to form, increasing the rate of reionization as star-forming regions cluster and merge together. The earliest galaxy we've ever identified (with today's instrumentation limits) appears about 400 million years after the Big Bang, with all the earliest galaxies actively forming stars at an alarming rate, but no more massive than 1% the mass of our modern Milky Way.

After a total of 550 million years, the Universe finally becomes fully reionized, and light can freely travel without being absorbed. Yet we continue to see only these bright but low-mass galaxies for some time, until about a billion years after the Big Bang, when enormous galaxies even more massive than our Milky Way appear in our telescopes. The big puzzle here is the missing link between these two populations.

In theory, the way these cosmic structures should form is through gravitational growth and mergers. Individual proto-galaxies should attract the matter from surrounding regions of space, while different proto-galaxies should attract one another. As time goes on, the gravitational influence of the various galaxies starts to affect larger and larger scales, leading to galaxies growing by eating one another and merging together.

But if that were the case, we wouldn't expect to see only the small, early proto-galaxies and the large, mature, post-merger galaxies. We would expect to see that intermediate stage, where the proto-galaxies are merging together, during the growth phase where star-formation is actively occurring. But all of the early galaxies we've seen aren't forming stars at a fast enough rate to explain these mature galaxies.

The distant galaxy MACS1149-JD1 is gravitationally lensed by a foreground cluster, allowing it to be... [+] imaged at high resolution and in multiple instruments, even without next-generation technology. This galaxy's light comes to us from 530 million years after the Big Bang, but the stars within it are at least 280 million years old. How we go from tiny galaxies like this to the massive ones we see a few hundred million years later is a mystery in galaxy evolution.

The standard expectation is that there's got to be some undiscovered type of galaxy in between these low-mass, early-type proto-galaxies and the heavy, massive, mature galaxies that we see. For those elusive galaxies to not appear in the same surveys that find both of the other types of galaxies means there must be something that's obscuring the light we're expecting to arrive.

For the most distant galaxies that are actively forming new stars at the greatest rates, we expect the light they'll emit will peak in ultraviolet wavelengths, just like they do for all massive star-forming regions where the light is dominated by stars significantly more massive than the Sun. After traveling through the expanding Universe, that light should redshift from ultraviolet through the visible part of the spectrum and all the way into the infrared. Yet our deepest infrared observations reveal only the early and late-type galaxies, not the intermediate type.

A young, star-forming region found within our own Milky Way. Note how the material around the stars... [+] gets ionized, and over time becomes transparent to all forms of light. Until that happens, however, the surrounding gas absorbs the radiation, emitting light of its own of a variety of wavelengths. In the early Universe, it takes hundreds of millions of years for the Universe to fully become transparent to light, and newly merged galaxies might require very long timescales to ionize all the obscuring gas-and-dust while the galaxy grows and forms stars.

Why could this be? The simplest explanation would be if something were blocking that light somehow. By the time the Universe is in the process of forming these very massive galaxies, it's already reionized, so we cannot blame the intergalactic medium for absorbing the light. But what might be a reasonable culprit is the gas and dust that belongs to the proto-galaxies which merge to form the late-type galaxies we eventually see.

Whenever you have a star-forming region, even if that region encompasses the entire galaxy, those stars are only able to form where you have neutral gas clouds collapsing. But neutral gas is exactly what we expect to block ultraviolet and visible light by absorbing it, and then re-radiating it at much longer wavelengths, dependent on the gas temperature. That light should be radiated in the infrared, and ought to be redshifted far into the microwave or even radio bands.

Light may be emitted at a particular wavelength, but the expansion of the Universe will stretch it... [+] as it travels. Light emitted in the ultraviolet will be shifted all the way into the infrared when considering a galaxy whose light arrives from 13.4 billion years ago; the Lyman-alpha transition at 121.5 nanometers becomes infrared radiation at the instrumental limits of Hubble. But warm gas, emitting in the infrared normally, will be redshifted all the way into the radio portion of the spectrum by the time it arrives at our eyes.

So instead of looking for redshifted starlight, you'd want to look for the signatures of warm dust that gets redshifted by the expansion of the Universe. You wouldn't use an optical/near-infrared observatory like Hubble, but rather a millimeter/submillimeter array of radio telescopes.

Well, the most powerful such array is ALMA, the Atacama Large Millimeter/submillimeter Array, which contains a collection of 66 radio telescopes designed for achieving high angular resolution and unprecedented sensitivity to detail in exactly that critical set of wavelengths. If you can find a faint, distant source of light that appears in these wavelengths and no others, you'll have discovered a candidate for exactly this type of "missing link" in galaxy formation. For the first time, a team of astronomers appears to have struck gold with exactly this discovery, by pure luck, in their observing field.

The Atacama Large Millimeter/submillimeter Array (ALMA) are some of the most powerful radio... [+] telescopes on Earth. These telescopes can measure long-wavelength signatures of atoms, molecules, and ions that are inaccessible to shorter-wavelength telescopes like Hubble, but can also measure details of protoplanetary systems and faint, early galaxies that may be obscured to more familiar wavelengths of light.

They made this discovery by looking at galaxies in the COSMOS field, a deep-field set of observations where many different observatories, including both Hubble and ALMA, have taken copious amounts of data. The team found two signals that corresponded to galaxies filled with warm dust and, therefore, rapid amounts of star formation. One of these corresponded to a run-of-the-mill late-type galaxy, but the other corresponded to no known galaxy at all.

When all the observations of this new galaxy candidate were combined, the astronomers studying it determined that it was:

Looking back through cosmic time in the Hubble Ultra Deep Field, ALMA traced the presence of carbon... [+] monoxide gas. This enabled astronomers to create a 3-D image of the star-forming potential of the cosmos. Gas-rich galaxies are shown in orange. You can clearly see, based on this image, how ALMA can spot features in galaxies that Hubble cannot, and how galaxies that may be entirely invisible to Hubble could be seen by ALMA.

The study's authors have expressed extreme excitement that this galaxy which appears in a survey area of just 8 square arcminutes (it would take 18 million such regions to cover the sky) might be a prototype for the "missing link" galaxies required to explain how the Universe grew up. According to study author Kate Whitaker,

"These otherwise hidden galaxies are truly intriguing; it makes you wonder if this is just the tip of the iceberg, with a whole new type of galaxy population just waiting to be discovered."

While other large galaxies, including star-forming galaxies, had been spotted before, none of them had large enough star-formation rates to possibly explain how the Universe's galaxies grew up so fast. But this galaxy changes all of that, according to first author Christina Williams, who noted,

"Our hidden monster galaxy has precisely the right ingredients to be that missing link, because they are probably a lot more common."

Optical telescopes like Hubble are extraordinary at revealing optical light, but the expansion of... [+] the Universe redshifts much of the light from distant galaxies out of Hubble's view. Infrared and longer wavelength observatories, like ALMA, can pick up the distant objects that are too redshifted for Hubble to see. In the future James Webb and ALMA, combined, might reveal details of these distant galaxies that we cannot even fathom today.

Up until now, scientists have been waiting for the James Webb Space Telescope humanity's next-generation, space-based infrared observatory to peer through the light-blocking dust and solve the mystery of how our Universe grew up. While Webb will certainly teach us more about these early, growing galaxies and reveal details that remain unseen, we've learned that these obscured monsters really are out there, and might be the missing link in galaxy growth and evolution.

Either we've gotten incredibly lucky in finding a very rare type of galaxy in such a small region of space, or this new find is an indicator that these behemoths really are everywhere. For now, this new discovery should leave us all hopeful that ALMA will continue to find more of these galaxies, and that when James Webb comes online, one more piece of the cosmic puzzle might slide perfectly into place.

Read more here:

Can This Newfound Dark, Massive Galaxy Be Astronomy's 'Missing Link' In The Universe? - Forbes