So: they thought the discrepancy had to do with possible errors in the measurement of Cepheid Variables as standard candles, when extrapolated with the more luminous and usually distant Type Ia Supernovas as standard candles, but JWST just confirmed that previous measurements of Cepheid Variables have in fact been correct and reliable.
Is this an accurate summary of the article?
Over the last several years, cosmologists have had to grapple with an unyielding conundrum. The expansion rate of the universe, also known as the Hubble’s constant (H0), has two different values depending on how you measure it, either with the echo of the Big Bang or with stars and galaxies. Researchers have now improved the precision of the second method, making the tension so much worse.
One of the key elements of the measurements is the calibration of Cepheids stars. The true luminosity of these stars fluctuates over a defined period, so by measuring said period and the brightness we see, it is possible to work out the distance of these objects. You could do the same with a distant lightbulb as long as you knew what wattage it was.
The method using the Cepheids is known as the cosmic distance ladder, and it has an estimated value of 73 kilometers per second per megaparsec (a megaparsec is equivalent to 3.26 million light-years). This means that if two galaxies are 1 megaparsec apart, they would appear to be moving away from each other at a speed of 73 kilometers (45 miles) per second.
“Our study confirms the 73 km/s/Mpc expansion rate, but more importantly, it also provides the most precise, reliable calibrations of Cepheids as tools to measure distances to date,” senior author, Richard Anderson, from the Ecole Polytechnique Federale de Lausanne, said in a statement.
By using the cosmic microwave background, as measured by the European Space Agency’s Planck space telescope, the expansion rate is 67.4 ± 0.5 km/s/Mpc. The discrepancy of 5.6 km/s/Mpc could either signify that there is an issue with the way we measure things, or that there is something deeply wrong with our understanding of the universe.
"Suppose you wanted to build a tunnel by digging into two opposite sides of a mountain. If you’ve understood the type of rock correctly and if your calculations are correct, then the two holes you’re digging will meet in the center. But if they don’t, that means you’ve made a mistake – either your calculations are wrong or you’re wrong about the type of rock,” explained Anderson.
“That’s what’s going on with the Hubble constant. The more confirmation we get that our calculations are accurate, the more we can conclude that the discrepancy means our understanding of the universe is mistaken, that the universe isn’t quite as we thought.”
Someone help me out: maybe that’s really magnetic for a star, but 43,000 gauss isn’t insanely strong, is it? We measure some magnets in teslas, which is 10,000 gauss.
So it’s a 4.3 tesla star.
I’m guessing this is somehow proportionate to the mass of the magnet, so a 1 tesla, 1 gram magnet is going to be much less powerful than a 1 tesla, 1 kg magnet? So something the size of a star would still have a massive magnetic field?
Well you have to put it in perspective. The earth has a magnetic field of 0.3 - 0.5 gauss. That puts this star at 143,000x as strong. Then you compare to the sun, which is 1 gauss, so this star is 43,000x as strong.
Okay, you might say, that's a lot, but this star is also 4x as massive as the sun. What about other stars bigger than the sun?
Beltugese is 16.5 - 19x the mass of the sun, and it's magnetic field has been carefully studied and measured to be about 1 gauss.
So yes, for a main sequence star this beast is a huge outlier.
No, this not a repost. It is a brand new version (as of yesterday) of the older article by the same author posted a week ago. Spoiler alert: no new constants have been found.
So we can deduce that the density and volume of the gas envelope is a function of the mass of the planet, the temperature of the star and the distance of the planet’s orbit. This would mean, generally, that rocky planets are most common closer to the star than gas giants, and so the configuration we see here is not uncommon. This would also mean an earth sized planet occupying an orbit a little farther out would be bigger with a larger gas envelope, and that in our orbit the planet would be bigger and have one.
That is an interesting observation. This means that dwarf stars, which are much more common than a star like the sun, are very unlikely to have a rocky planet with the same size and orbit of Earth. But a giant star like Betelgeuse might have a rocky planet much bigger than Earth. Although a full orbit of Betelgeuse would take a long time.
This tells us something remarkable and unexpected to many: Earth, the largest rocky planet in our entire Solar System, is almost as “super” as a rocky planet can get. If you managed to form an Earth-sized planet early on in your Solar System’s history, it would only need to get a little bit larger and more massive before it became capable of hanging onto volatile molecules like ammonia, methane, and even hydrogen and helium. And once you become rich in volatiles, you’re guaranteed to no longer be rocky, but rather more like Neptune, with a large gas envelope around you.
This I find very interesting. How many definetly rocky Exoplanets have we discovered so far? Or at the Exoplanets we have found so far alla gas giants?
Here is a quick summary. Astronomers used to assume that planets as big as 2x Earth diameter could be rocky planets. But now we know that most planets bigger than 1.3 Earth diameter are mini Neptunes. Although sometimes rocky planets can get as big as 1.5 Earth diameter.
Neptune’s diameter is about 50 megameters. Earth’s diameter is 12.7 megameters. So per the article, most planets bigger than a 16.5 megameter diameter is probably a mini Neptune. Although a rocky planet could be as big as a 19 megameter diameter.
<span style="color:#323232;">The astronomers will tell you it is just an optical illusion, a pair of galaxies caught in the act of mating as seen from the wrong angle. Happens all the time.
</span><span style="color:#323232;">
</span><span style="color:#323232;">In the 1960 and 70s, Halton Arp, an astronomer at Hale Observatories in Southern California, caused a ruckus by asserting that galaxies millions of light-years apart according to conventional cosmological calculations — but which appeared superimposed together in the sky — were interacting locally. His claim cast doubt on the Big Bang theory of the universe. Astronomers now agree that he was wrong.
</span><span style="color:#323232;">
</span><span style="color:#323232;">Now a genuine question mark has been discovered, in the corner of a recent Webb telescope observation of a pair of dust clouds known as Herbig-Haro 46/47 that are in the process of forming into two stars. The discovery made a splash on social media. “Ze space mall information kiosk has been found by JWST,” a commenter joked on X, the site formerly known as Twitter.
</span><span style="color:#323232;">
</span><span style="color:#323232;">Chris Britt, an astronomer at the Baltimore-based Space Telescope Science Institute, which runs the Webb telescope, attempted to explain. “This particular pair is so far away, it’s hard to make out much detail,” he said in an email exchange. “But there are some similar looking galaxy mergers that have been seen closer to us, including this one called II Zwicky 96.”
</span><span style="color:#323232;">
</span><span style="color:#323232;">If you accept the spooky rules of quantum mechanics and the premise, as Einstein disapprovingly put it, that God plays dice with the universe, then you have to accept that chance and randomness are a fundamental bedrock of reality. In such a universe, where the laws of physics have been grinding away for 14 billion years, coincidences are unforeseeable but inevitable.
</span><span style="color:#323232;">
</span><span style="color:#323232;">Image
</span><span style="color:#323232;">A thin horizontal orange cloud known as Herbig-Haro 46/47 is uneven with rounded ends and tilted from bottom left to top right. At its center is a red-and-pink star with prominent, eight-pointed diffraction spikes. The background is filled with stars and galaxies.
</span><span style="color:#323232;">An image of Herbig-Haro 46/47. The question mark appears at the center-bottom of the frame, to the right of the reddish cloudy material.Credit...NASA, ESA, CSA, Joseph DePasquale (STScI), Anton M. Koekemoer (STScI)
</span><span style="color:#323232;">
</span><span style="color:#323232;">Still, there are times when it’s worth stepping back to listen to “the music,” as Einstein once referred to the beauty and mystery of the cosmos. You are free to consider that question mark as alien graffiti, a comment on both their and our relation to existence. Point being, we’ve barely begun to know anything — that’s why we build telescopes.
</span><span style="color:#323232;">
</span><span style="color:#323232;">Once the Webb has completed its rounds of investigations two decades from now, we might know a bit more about how this bowl of stars works. But we still won’t know why we’re here. That question mark, our profound cosmic ignorance, is one of the great gifts of science.
</span>
Let me stop you right there: a ray can’t emanate from a black hole, that’s why it’s a black hole, not even zero-mass light-speed photons can get out.
We know about black holes rotating, because we can detect frame dragging around them, which means whatever mass is in there, has an average rotation.
The thing is, an absolute “singularity” doesn’t even make sense for a black hole. From what we know of how they get formed, they’re just a bunch of star that gets compressed so tight that its own gravity doesn’t let anything escape… but that doesn’t mean every particle goes straight to the center of mass. Forming a singularity would require the initial star core to be kind of perfectly symmetrical, at absolute rest and 0K, which definitely is not the case. What’s more likely, is that at the center of a black hole, there is a star worth of particles “orbiting” the center of mass at speeds close to the speed of light, sometimes bumping into each other, but since not even mass-less photons can escape the black hole, nothing can get bumped out like it would in normal stars, atmospheres, and so on.
From a mathematical point of view it makes sense to say there is a “singularity”, since for most purposes it behaves like one… but it really isn’t one. It’s also easier to think of the event horizon to be “empty” inside… but it also really is not, it’s going to be full of recently trapped particles on decaying orbits, with a lot of them being still right on the other side of the event horizon (more particles will be entering at a shallower than a steeper angle).
Also, being an actual singularity would make evaporation due to Hawking radiation kind of impossible.
When I said “ray” I just meant an imaginary line that could be drawn to extend in a given direction, not a literal particle escaping. It was mostly to think of a way you might conceptualize an orientation of an object that may not have any dimension. As in, if the matter just outside a singularity rotates, perhaps you could consider it to rotate? But I’m not sure that would be accurate to say anyway. My grasp of the physics of black holes is obviously pretty loose. :)
an orientation of an object that may not have any dimension
The thing is, if it had no dimension, then there would be no way for it to have any orientation in some dimensions, it would have to be perfectly identical regarding all dimensions.
if the matter just outside a singularity rotates
It’s a bit more fun, because it would be normal for matter to orbit around before falling in, but “frame dragging” means that not just matter, but also light outside it rotates with the black hole, and time gets stretched.
astronomy
Active
This magazine is from a federated server and may be incomplete. Browse more on the original instance.