Astronomy
How do astronomers know the age of the Universe?
How do we tell how old something is? Well, one way of doing that is by comparing it with something else we already know the age of through a different method. When paleontologists find fossils embedded into rocks, they assume both are of the same age – depending on which is known, you can use the age of one to determine the age of another. When calculating the age of the Solar System, we use radiometric dating to determine how old asteroids are, and since we estimate they formed around the time as the Sun and the planets, we can figure out how long ago they were all born.
Another way of determining the age of something is by measuring the rate of change of various properties. We know trees grow another ring each year, so by counting the rings, you can determine its age. Carbon dating is a more sophisticated method, which works by measuring the proportion of different carbon isotopes within organic fossils. In living things, the proportion of carbon isotopes is relatively stable, but after they die the radioactive carbon-14 isotope starts to decay into nitrogen-14. We know precisely the rate at which this happens: half the carbon-14 will decay in 5,730 years (this is what’s called its half-life). So if the sample has just half the amount of carbon-14 we’d expect to find in a living thing, it is 5,730 years old. If we only find a quarter of that quantity, it is about 11,500 years old – and so on. For very old things, there are other methods of radiometric dating which use isotopes like uranium or potassium, which decay over hundreds of millions and billions of years. But how can we tell the age of the Universe itself, since we can’t compare it to anything and it’s also the oldest thing we know?
For one thing, we can set a lower boundary for the age of the Universe by comparing it to objects whose age we know. In other words, the Universe can’t be younger than cosmic objects whose age we’ve accurately measured. Globular clusters (densely packed groups of stars orbiting galactic centers which formed in the early Universe) are estimated to be 11 to 18 billion years old, so this is a good place to start. We’ve since found galaxies and even planets which are 13 billion years old or more, so we know the Universe itself has to be older.
There’s a really neat way of actually calculating the age of the Universe, and all you have to do is accurately measure the so-called Hubble constant, or the rate at which space itself is expanding. As I’ve mentioned in a previous post, everything in the Universe is moving away from us – and the farther it is, the faster it’s moving. Edwin Hubble himself calculated the figure at around 530 km per second per megaparsec; today, we know the figure is between 65 and 80 km per second per megaparsec. Hubble’s measurement is still remarkable, because figuring out how far away things are in the Universe is really difficult – even today.
What the Hubble constant tells us is that things that are at a distance of one megaparsec (about 3.1 million light-years) from us are moving away at a speed of about 70 km/s, while things that are two megaparsecs are receding at 140 km/s. If everything is moving away from everything else today, this means that in the past, everything was closer together, and at the very beginning, everything was in a single point or a singularity (the Big Bang theory, in a nutshell).
Since we know that speed is distance over time and the Hubble constant is speed over distance, we can use simple algebra to figure out how long it’s been since the Big Bang. Well, it’s not actually that simple, astrophysicists also have to take into account the geometry of space (is it closed, open or, as most scientists believe, flat?) and the amount of matter in the Universe. By using the latest measurements and crunching all the numbers, it turns out the age of the Universe is about 13.82 billion years.
Astronomy
Witness the rare celestial event of Mars and Jupiter reaching their closest proximity in the sky this week, a phenomenon that will not occur again until 2033.
Mars and Jupiter will be only 0.3 degrees apart in the sky on August 14. From our point of view, this passage is very close. If you miss it, you won’t be able to see another one until 2033.
When two objects pass each other in the sky from our point of view, this is called a conjunction. Every time two planets came together, the closer one would block out the other because they would all be moving in a perfectly flat plane. The orbits of the planets are slightly different from those of the other planets, though, so they move slightly to the north and south of each other. Every time, that gap is a different size.
When two things happen close together, the results are especially stunning. Jupiter and Saturn were close enough to each other in 2020 that they could be seen in the same field of view through a telescope. This is a treat for people who like to observe the sky.
Being 0.5 degrees wide, the full moon will fit in any view that can hold the whole moon. This pair will also look good before and after the full moon.
But even with the naked eye, a close conjunction can make the sky look even more amazing. The contrast between the red of Mars and the white of Jupiter will be especially striking. However, Mars’ brightness changes a lot. When it’s at its brightest, it’s about the same brightness as Jupiter. Right now, it’s 16 times less bright. They are so bright that, unless there are clouds, you should be able to see them from all but the dirtiest cities.
Most people in the world will miss this sight, though, because they can’t see the pair of planets in the evening from anywhere on Earth. The exact time they rise depends on where you live, but it’s usually between midnight and 3 am. To see this, you will mostly need to get up before astronomical twilight starts so that you have time to get through the thickest part of the atmosphere.
For people in Europe, Africa, west Asia, and the Americas, the closest time will be 14:53 UTC, which is during the day. The mornings before and after, though, will look almost as close.
Mars and Jupiter meet about every two and a half years, but the most recent one was almost twice as far away and could only be seen in the morning. In 2029, the gaps will be just under two degrees. The next one will be even wider, at more than a degree.
When planets are close to each other, that doesn’t always mean that their distance from each other is very small. Mars has been around the Sun for 687 days, but it is now less than 100 days past its perihelion, which means it is closer than usual. Even though Jupiter is a little closer than usual, it’s not really that close. To be as close as possible to each other, Mars has to be at its farthest point, and Jupiter has to be at its closest point. So this one is not unusual.
But if you want to see something beautiful, you will have to wait more than nine years to see it again.
Astronomy
It may not be long before we find “Earth’s Twin”
To figure out if there is life in other parts of the universe, we start with Earth, where there is life now. Finding another Earth is a good way to find aliens. We have found more than 5,000 exoplanets, but we haven’t found Earth’s twin yet. This could change soon, though. Here comes the PLATO mission from the European Space Agency (ESA).
What does PLATO stand for? It stands for PLAnetary Transits and Oscillations of stars. Its goal is very clear. It will look for nearby stars like the Sun that might have habitable worlds like Earth.
“One of the main goals is to find a way to compare Earth and the Sun.” The size of Earth is in the habitable zone of a star like the Sun. “We want to find it around a star that’s bright enough that we can really figure out how heavy it is and how big it is,” Dr. David Brown from the University of Warwick told IFLScience. “If you like, that’s our main goal.”
The telescope is not only an observatory for looking for planets, but it is also an observatory for collecting data on a huge number of stars. The mission team thinks that the fact that it can do both is a key part of why this telescope will be so important.
“You have two parts of the mission.” One is exoplanets, and the other is the stars. “From a scientific point of view, I think it’s pretty cool that these two parts are working together to make the best science we can,” Dr. Brown said.
One of the secondary goals is to make a list of all the planets that are Earth-like and all the star systems that are out there. One more goal is to find other solar systems that are like ours. Even though we don’t know for sure if our little part of the universe is truly unique, it does seem to be different from everything else.
Dr. Brown told IFLScience, “We have a bunch of other scientific goals.” “Really, how well do we know how planetary systems change and grow over time?” Planetary systems are something we’re trying to understand as a whole, not just one planet at a time.
PLATO is different in more ways than just the goals. It is not just one telescope. In fact, it’s made up of 26 different ones. Two of the cameras are fast, and the other 24 are normal cameras set up in groups of six with a small gap between them. This makes the telescope work better, has a wider field of view, and lets you quickly rule out false positives.
It can be hard to tell which of the things you find when you transit exoplanets are real and which ones are not. With the help of several telescopes, we were able to block out some of the mimics that we would have seen otherwise. “Plus, it looks pretty cool,” Dr. Brown said with excitement. “This big square with all of these telescopes pointing at you looks really cool!”
This week, Dr. Brown gave an update on PLATO at the National Astronomy Meeting at the University of Hull. The telescope is being put together and has recently passed important tests. There are no changes to the planned launch date for December 2026. An Ariane 6 rocket, the same kind that made its first launch last week, will take off from French Guiana.
Astronomy
You can watch and listen to gravitational waves coming from everywhere in the universe
Gravitational waves can be turned into sound very easily. The little chirp changes into little sounds as soon as the blocks hit each other. One of those chirps is my ringtone when my phone has sound, which doesn’t happen very often. The people at Audio Universe have now made the gravitational wave data even better.
In a 3D video, the sounds of gravitational waves hit you from the direction in the sky where it is thought they came from. The sound effects and visualization are both great. There are tiny vibrations in space-time that can hit you as you move your mouse, phone, or VR headset.
Like other sonification projects, it gives blind and visually impaired people a way to get involved in astronomy. It works well with other methods like the Tactile Universe. But that’s not the only reason why they do it.
“We want to do this for three reasons.” It helps researchers look into big, complicated datasets with lots of dimensions. It could be used to make educational materials that are immersive and interesting. Rose Shepherd from Newcastle University says, “It can also make astronomy easier for more people to understand, which is an important thing.” “Making things easier to get makes them better for everyone.”
Being able to listen to the emission lines of celestial objects is one of the most interesting things about sonification for research. As an object moves, its light spectrum peaks spread out, and sonification can make something that is barely noticeable to the eye seem very clear to the ear.
This is helpful in more than one field, though. The group has thought about how adding sound to different datasets could make them better. Warming Stripes is a cool example of this. This is a simple image that shows changes in temperature over time by using a series of stripes, from blue to red. The stripes on the right side get redder as we move from the left to the right. The left side shows decades ago. It is great to see how the climate crisis is getting worse, and now sound adds a little more to it.
“By adding sounds, it can give your data an emotional meaning.” Shepherd explained, “You can use that to show the data how you feel.” “We didn’t mean for the Warming Stripes sonification to make people feel stressed, but it was interesting to see how they reacted instead of just watching the video.”
Audio Universe is making a sonic toolkit that many people can use to make their own resources.
She gave a talk about the audio universe at the National Astronomy Meeting at the University of Hull this week.
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