Around 13.8 billion years ago, somehow the Universe popped into existence. But it didn’t come fully equipped. At some point, the first stars formed, and the first galaxies. How and when this happened is still a mystery astronomers are trying to solve… but one galaxy could have a vitally important key.
It’s called DLA0817g – nicknamed the Wolfe Disk – a cool, rotating, gas-rich disc galaxy with a mass of about 72 billion times that of our Sun. And the Atacama Large Millimeter/submillimeter Array has snapped it a massive 12.5 billion light-years away – when the Universe was just 10 percent of its current age.
It’s the earliest rotating disc galaxy astronomers have found yet, and its very existence changes our understanding of galaxy formation in the early Universe.
Most of the galaxies in the early Universe are a hot mess, literally. They’re all blobby, with stars flying every which way, and rather high temperatures. Astronomers have interpreted this to mean that they grew large by colliding and merging with other galaxies – a hot, messy process.
“Most galaxies that we find early in the Universe look like train wrecks because they underwent consistent and often ‘violent’ merging,” explained astronomer Marcel Neeleman of the Max Planck Institute for Astronomy in Germany.
“These hot mergers make it difficult to form well-ordered, cold rotating disks like we observe in our present Universe.”
Under this scenario, it takes a long time for the galaxies to cool down and smooth out into the more orderly rotating disc galaxies like the Milky Way. We don’t generally start seeing them until about 4 to 6 billion years after the Big Bang.
This is the “hot” mode of galaxy formation. But astronomers had also predicted and simulated another way – the “cold” mode.
First, you need to start with the primordial soup, an ionised quark-gluon plasma that filled the Universe before the formation of matter. To go from this homogeneous plasma to a Universe filled with stuff, astrophysicists have run simulations that suggest dark matter is responsible.
We don’t know what dark matter is. We can’t detect it directly, but it interacts gravitationally with normal matter. It helps to hold galaxies together, and we believe that it could be crucial to galaxy formation, clumps of it pulling together gas and stars into galaxies.
Supercomputer simulations have shown that a massive network of dark matter in the early Universe could have facilitated the formation of cool galaxies. If the gas was cool to start with, it could have been fed along filaments of the network into the dark matter clumps, accreting into large, cool, orderly disc galaxies.
But the only way to confirm this model is through observational evidence, so the researchers went looking, using the light of even more distant galaxies, called quasars, to illuminate the way.
Distant galaxies are very hard to see, but quasars are among the most luminous objects in the Universe – galaxies lit by an active supermassive black hole, the space around it blasting out radiation as it feeds. The team turned ALMA’s powerful capabilities to these distant quasars, looking for signatures in their light that showed that it had passed through a gas-filled galaxy on the way.
They found it. The light from one of the quasars they imaged had passed through a region rich with hydrogen – the signature of the Wolfe Disk.
And there was something else. The light on one side of the disc was compressed, or blueshifted. We see this when something is moving towards us. And the light from the other side was stretched, or redshifted – moving away from us. The object was rotating.
Those Doppler shifts, as they are known, then allowed the researchers to calculate the velocity of the galaxy’s rotation: around 272 kilometres per second.
What’s even more wild is that the team believes the Wolfe Disk isn’t one of a kind.
“The fact that we found the Wolfe Disk using this method, tells us that it belongs to the normal population of galaxies present at early times,” Neeleman said.
“When our newest observations with ALMA surprisingly showed that it is rotating, we realised that early rotating disk galaxies are not as rare as we thought and that there should be a lot more of them out there.”
The team will continue their search for these galaxies to find out just how common cold accretion was in the early Universe.
The research has been published in Nature.
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How to see Mercury, Jupiter and Saturn in rare conjunction this weekend – CNET
A trio of planets make an appearance at dusk this weekend when Jupiter and Saturn, still chilling together at the after-party from last month’s, will be joined just above the western to southwestern horizon by the more flighty planet Mercury. The planetary trio is a rare sight that can be witnessed with the naked eye just after sunset over the next several days, though Saturday evening offered perhaps the best opportunity to see the three worlds bunched together.
Astronomy magazine reports that the planets will all be visible within an area about 2.3 degrees across that evening (that’s about the width of your pinky and ring finger together when they’re held away from your body at arm’s length). Mercury will be the lowest of the three in the sky, Jupiter will be the brightest and Saturn will be the dimmest.
Binoculars might help you get a better view, while even a cheap backyard telescope can offer a chance to glimpse some of the larger moons of Jupiter. This might be a good thing to try when Mercury and Saturn have disappeared below the horizon and it’s a little darker out.
To be sure to catch the entire trio, the key is to get outside right after the sun sets as Mercury and Saturn will be quick to dip below the horizon within an hour. While the planets may be closest Saturday, they will continue to congregate while shifting around over the next several nights, so you have a few shots at catching them all like a kind of cosmic game of Pokemon.
As always, if the amateur astrophotographers among you grab any great images of the celestial gathering, please share them with me on Twitter @EricCMack.
Follow CNET’s 2021 Space Calendar to stay up to date with all the latest space news this year. You can even add it to your own Google Calendar.
See Saturn’s secrets through NASA Cassini’s finest views
NASA’s Europa Clipper has been liberated from the Space Launch System | TheHill
Almost unnoticed, tucked into the 2021 fiscal NASA funding section of the recently passed omnibus spending bill, is a provision that would seem to liberate the upcoming Europa Clipper mission from the Space Launch System (SLS).
According to Space News, the mandate that the Europa Clipper mission be launched on an SLS remains in place only if the behind-schedule and overpriced heavy lift rocket is available and if concerns about hardware compatibility between the probe and the launcher are resolved. Otherwise, NASA is free to search for commercial alternatives to get the Europa Clipper to Jupiter’s ice-shrouded moon.
Europa Clipper is slated to go into orbit around Jupiter and make multiple flyby maneuvers near Europa, an icy world that many scientists believe has a warm ocean under the ice layer. Life may exist in that ocean, the confirmation of which would be one of the greatest scientific discoveries of this or any other century.
The Europa Clipper being mandated to fly on an SLS to begin with was the result of an unseemly side of congressional budget politics. The space probe was championed by former Rep. John CulbersonJohn Abney CulbersonTexas Republicans sound post-2020 alarm bells 2020 Democratic Party platform endorses Trump’s NASA moon program Bottom line MORE (R-Texas), who at the time was the chair of the House appropriations subcommittee that funds NASA. In order to get support for the Europa Clipper, Culberson added the SLS mandate, which garnered support from Sen. Richard ShelbyRichard Craig ShelbyRepublican infighting on election intensifies Bipartisan group of senators: The election is over Bottom line MORE ( R-Ala.), chair of the Senate Appropriations Committee. Shelby’s state contains a number of aerospace contractors involved in developing the SLS.
Ironically, Culberson lost his seat in 2018, in part, because his opponent, Rep. Lizzie Fletcher (D-Texas), accused him of being more concerned with space missions than local issues, such as flooding brought on by Hurricane Harvey. Nevertheless, the Europa Clipper continued without its key champion in Congress.
As Ars Technica points out, launching the Europa Clipper on a SpaceX Falcon Heavy saves the mission $1.5 billion. An advantage of using the SLS has been that it allows for a direct path to Jupiter without the time-consuming planetary flyby maneuvers that previous missions to the outer planets have required. The Falcon Heavy alone would not be able to get the Europa Clipper to Jupiter space directly, though it might be able to if equipped with a powerful Centaur kick stage.
Both the economics and physics of getting to Europa change if SpaceX’s Starship, currently under development in Boca Chica, Texas, becomes available to launch the Europa Clipper in the mid-2020s. The Starship is meant to fulfill SpaceX’s CEO Elon MuskElon Reeve MuskWill Axiom Space provide a commercial space station replacement for NASA’s ISS? World’s richest people added .8T to their combined wealth in 2020 Trump ends Obama’s 12-year run as most admired man: Gallup MORE’s dreams of settling Mars. But the massive reusable rocket would be available for other things, presumably including sending probes to the outer planets.
The massive cost savings by using a commercial launcher for the Europa Clipper creates other possibilities. The Europa Lander could be placed back on. A mission to Saturn’s frozen world Enceladus may also be greenlit.
The SLS is the result of a Faustian bargain struck between NASA and Congress in 2010. Congress was enraged by then-President Obama’s cancellation of the Bush-era Constellation deep space exploration program. According to then-NASA Deputy Administrator Lori Garver, NASA agreed to the SLS in return for Congress supporting the Commercial Crew program that recently came to fruition with the launch of astronauts to the International Space Station (ISS) on a SpaceX Crew Dragon.
The SLS has since been a lead weight on America’s space ambitions. The SLS slated to launch the Artemis 1 uncrewed mission around the moon is currently stuck in a ground-based “green run” series of tests. The SLS is currently using up a great deal of the money allocated to NASA’s Artemis program. The first flight is scheduled for November 2021 at the earliest.
In the meantime, SpaceX has been flying prototypes of the Starship, albeit only in the atmosphere and with occasionally explosive results. NASA is officially disdainful of the idea of replacing the SLS with the Starship. However, a version of the SpaceX massive rocket ship is in the running as a lunar lander for Artemis. It would not be too great a leap to cut out the SLS entirely and go directly with the Starship, if it were not for congressional budget politics.
And that, as Shakespeare would say, is the rub.
Mark Whittington, who writes frequently about space and politics, has published a political study of space exploration entitled Why is It So Hard to Go Back to the Moon? as well as The Moon, Mars and Beyond. He blogs at Curmudgeons Corner. He is published in the Wall Street Journal, Forbes, The Hill, USA Today, the LA Times, and the Washington Post, among other venues.
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