An article published in 'The Astrophysical Journal Letters' reports the results of a study of the Small Magellanic Cloud that shows how this
An article published in "The Astrophysical Journal Letters" reports the results of a study of the Small Magellanic Cloud that shows how this dwarf galaxy is undergoing distortions in its shape due to various gravitational influences. Satoya Nakano and Kengo Tachihara of Nagoya University, Japan, used data collected by ESA's Gaia space probe together with information on Cepheid stars collected by the OGLE (Optical Gravitational Lensing Experiment) project. This allowed them to determine the distances of 4,236 Cepheids and the anomalies in their motions. The conclusion is that the Small Magellanic Cloud is undergoing a gravitational influence from the Large Magellanic Cloud and another as yet unknown source.
Our galaxy’s got curves. You can see them in a chart of thousands of stars called Cepheids.
Our home galaxy, the Milky Way, is warped. It looks like a misshapen potato chip. And, there’s a new 3-D map that brings the contorted structure of the Milky Way’s disk into better view.
The Milky Way’s disk is usually depicted as flat. But previous observations had revealed that the galaxy is curved at its edges. The new study shows that the Milky Way is even more warped than scientists had thought, says Dorota Skowron. She is an astronomer at the Astronomical Observatory of the University of Warsaw in Poland. Imagine you took a spaceship into deep space and looked back at our galaxy. “You could see by eye” that it’s misshapen, Skowron says.
To make measurements of the galaxy, scientists have to estimate how far away stars are from Earth. That’s typically a matter of guesswork. This time, the scientists made the map with measurements of stars called Cepheids. Unlike most stars, Cepheids vary in brightness over time. They vary in brightness in a particular way. Scientists can use that brightness to determine a precise distance to each star.
Skowron and colleagues made new observations of Cepheids as part of the Optical Gravitational Lensing Experiment, or OGLE. The team combined those measurements with previously studied Cepheids. That resulted in 2,431 stars charted in the map. The scientists describe the map in the August 2 Science.
The team also used the Cepheids’ brightness variations to estimate the stars’ ages. Younger Cepheids aligned with the Milky Way’s spiral arms. The older stars were more scattered. This is a result of how they move over time as the galaxy rotates. That’s at least according to a computer simulation. The scientists were able to roughly reproduce the stars’ actual distributions. They did it by simulating stars forming in the galaxy’s arms and spreading out over time. That helped scientists understand how the galaxy came to have its current curves.
The Milky Way’s Cepheid stars are plotted in three dimensions. The stars reveal the galaxy’s warped shape. Cepheids are special stars. They vary in brightness in a particular way that helps scientists make more precise estimates of their distances from Earth. Brighter colors represent Cepheids closer to the warped plane of the galaxy. The warped plane of the galaxy is indicated by the grid. The star icon indicates the sun.
Why Cosmology's Expanding Universe Controversy Is An Even Bigger Problem Than You Realize
“The question of how quickly the Universe is expanding is one that has troubled astronomers and astrophysicists since we first realized that cosmic expansion was a necessity. While it's incredibly impressive that two completely independent methods yield answers that are close to within less than 10%, the fact that they don't agree with each other is troubling.
If the distance ladder group is in error, and the expansion rate is truly on the low end and near 67 km/s/Mpc, the Universe could fall into line. But if the cosmic microwave background group is mistaken, and the expansion rate is closer to 73 km/s/Mpc, we just may have a crisis in modern cosmology.
The Universe cannot have the dark matter density and initial fluctuations that such a value would imply. Until this puzzle is resolved, we must be open to the possibility that a cosmic revolution may be on the horizon.”
Ever since we first learned that the Universe was expanding, scientists have worked hard to measure just how fast that expansion rate is. From that, combined with what makes up the Universe, we can learn how old the Universe is and what it was like in the past, as well as what it’s fate will be in the future. Yet the two groups that make independent measurements of that rate, from the cosmic microwave background and the cosmic distance ladder, have gotten inconsistent results. If the distance ladder team has made a mistake, everything will be fine with cosmology. But if that team is right and the microwave background team is wrong, there should be a crisis coming.
Why is that? Come find out why the biggest controversy in modern cosmology might be an even bigger problem than almost everyone realizes!
Our galaxy flaunts its curves in a chart of thousands of stars called Cepheids.
Like a misshapen potato chip, our home galaxy is warped. A new 3-D map brings the contorted structureof the Milky Way’s disk into better view, thanks to measurements of special stars called Cepheids, scientists report in the Aug. 2 Science.
Making 3-D measurements of the galaxy requires estimating how far away stars are from Earth, typically a matter of guesswork. But unlike other stars, Cepheids vary in brightness over time in a particular way that can be used to determine a precise distance to each star.
Although the Milky Way’s disk is usually depicted as flat, previous observations had revealed that the galaxy is curved at its edges. The new study shows that that the Milky Way is even more warped than scientists had thought, says astronomer Dorota Skowron of the Astronomical Observatory of the University of Warsaw. If you took a spaceship into deep space and looked back at our galaxy, says Skowron, “you could see by eye” that it’s misshapen.
Skowron and colleagues made new observations of Cepheids as part of the Optical Gravitational Lensing Experiment, or OGLE. Combining those measurements with previously studied Cepheids resulted in 2,431 stars charted in the map.
The team also used the Cepheids’ regular brightness variations to estimate the stars’ ages. Younger Cepheids aligned with the Milky Way’s four main spiral arms, while the older stars were more scattered, a result of their dispersal over time as the galaxy rotates, a computer simulation suggests. The scientists were able to roughly reproduce the stars’ actual distributions by simulating stars forming in the galaxy’s arms and spreading out over time, helping scientists understand how the galaxy came to have its current structure.
3-D VISION The Milky Way’s Cepheid stars are plotted in three dimensions, revealing the galaxy’s warped shape. Unlike other stars, Cepheids vary in brightness in a particular way that helps scientists make more precise estimates of their distances from Earth. Brighter colors represent Cepheids closer to the warped plane of the galaxy, indicated by the grid. The star icon indicates the sun.
An article accepted for publication in 'The Astrophysical Journal' reports the results of calculating the universe's expansion rate based on
An article accepted for publication in "The Astrophysical Journal" reports the results of calculating the universe's expansion rate based on the observation of Cepheids with the James Webb Space Telescope. In particular, a team of researchers led by Adam Riess used the NIRCam instrument to observe over 330 cepheids in the galaxies NGC 4258 and NGC 5584. The results are more precise than those obtained in the past with the Hubble Space Telescope but confirm the accuracy of the previous calculation of the universe's expansion rate. This leaves open the question of the difference in results obtained with different methods.
Bagaimana Cara Mengukur Jarak dari Bumi ke Matahari ?
Bagaimana Cara Mengukur Jarak dari Bumi ke Matahari ?
Mengukur jarak antara dua benda atau titik mungkin tidak terlalu susah, kita dapat menggunakan penggaris atau bahkan sinyal ultrasonik. Namun, pernahkah terpikirkan oleh anda bagaimana cara peneliti mengukur jarak dari bumi ke bulan, matahari, atau bahkan ke galaksi lain? Sepertinya penggaris tidak terlalu berguna pada kasus seperti ini.
