#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.

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.

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.

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.

Metode-metode yang dapat digunakan antara lain:

Radar

Paral…