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Variable Star Astronomy
Variable stars are stars whose brightness changes because of physical changes within the star. There exist more than 30,000 variable stars in just the Milky Way. Variable star astronomy is a popular part of astronomy because amateur astronomers play a key role. They have submitted thousands of observed data and these data are logged onto a database. American readers can find information on it on the American Association of Variable Star Observers page.
One of such variable stars are called Cepheids. Cepheids are pulsating variable stars because they undergo a “repetitive expansion and contraction of their outer layers” [1]. In Cepheids, the star’s period of variation (about 1-70 days) is related to its luminosity; the longer the period, the higher the luminosity. In fact, when graphed, the relationship is shown by a straight line (as can be seen on the title image). Henrietta Swan Leavitt, an American astronomer, first discovered this and understood the significance of this knowledge. Combined with understanding of the star’s apparent magnitude (a previously written post on this subject can be found here), astronomers can use this information to find a star’s distance from Earth. Cepheids are famously known for their usefulness in finding distances to far-away galaxies and other deep sky objects. Leavitt died early from cancer but was to be nominated for the Nobel Prize in Physics by Professor Mittag-Leffler (Swedish Academy of Sciences).
Edwin Hubble used Leavitt’s discovery to prove that the Andromeda Galaxy (M31) is not part of the Milky Way, but was able to find the distance to the Andromeda Galaxy (between 2-9 million light years away). At first his calculation was incorrect (900,000 light years) because he observed Type I (classical) Cepheid Stars. Type I Cepheid stars are brighter, newer Population I stars. Hubble later used type II Cepheids (also called W Virginis stars), which are smaller, dimmer, Population II stars, and he was able to make more accurate calculations.
To determine the star’s distance, use the inverse square law of light brightness.
A similar type of star are RR Lyrae Variable Stars. They are smaller than Cepheids and have a much shorter period (from a few hours to a day). On the other hand, they are far more common. Likewise, they can be used to solve for distances as well. Low mass stars live longer, and thus Cepheid stars are generally younger because they are more massive.
Both Cepheids and RR Lyrae Variable stars are referred to as standard candles: objects with known luminosity. If you’ve ever wondered how astronomers came to those enormous figures when describing how far away galaxies and stars are from us, you can now better understand why and how.](http://25.media.tumblr.com/tumblr_luo93515tH1qmyxvuo1_500.gif)
Variable Star Astronomy
Variable stars are stars whose brightness changes because of physical changes within the star. There exist more than 30,000 variable stars in just the Milky Way. Variable star astronomy is a popular part of astronomy because amateur astronomers play a key role. They have submitted thousands of observed data and these data are logged onto a database. American readers can find information on it on the American Association of Variable Star Observers page.
One of such variable stars are called Cepheids. Cepheids are pulsating variable stars because they undergo a “repetitive expansion and contraction of their outer layers” [1]. In Cepheids, the star’s period of variation (about 1-70 days) is related to its luminosity; the longer the period, the higher the luminosity. In fact, when graphed, the relationship is shown by a straight line (as can be seen on the title image). Henrietta Swan Leavitt, an American astronomer, first discovered this and understood the significance of this knowledge. Combined with understanding of the star’s apparent magnitude (a previously written post on this subject can be found here), astronomers can use this information to find a star’s distance from Earth. Cepheids are famously known for their usefulness in finding distances to far-away galaxies and other deep sky objects. Leavitt died early from cancer but was to be nominated for the Nobel Prize in Physics by Professor Mittag-Leffler (Swedish Academy of Sciences).
Edwin Hubble used Leavitt’s discovery to prove that the Andromeda Galaxy (M31) is not part of the Milky Way, but was able to find the distance to the Andromeda Galaxy (between 2-9 million light years away). At first his calculation was incorrect (900,000 light years) because he observed Type I (classical) Cepheid Stars. Type I Cepheid stars are brighter, newer Population I stars. Hubble later used type II Cepheids (also called W Virginis stars), which are smaller, dimmer, Population II stars, and he was able to make more accurate calculations.
To determine the star’s distance, use the inverse square law of light brightness.
A similar type of star are RR Lyrae Variable Stars. They are smaller than Cepheids and have a much shorter period (from a few hours to a day). On the other hand, they are far more common. Likewise, they can be used to solve for distances as well. Low mass stars live longer, and thus Cepheid stars are generally younger because they are more massive.
Both Cepheids and RR Lyrae Variable stars are referred to as standard candles: objects with known luminosity. If you’ve ever wondered how astronomers came to those enormous figures when describing how far away galaxies and stars are from us, you can now better understand why and how.
Information Could Escape from Black Holes After All, Study Suggests
ScienceDaily (Aug. 10, 2011) — New research by scientists at the University of York gives a fresh perspective on the physics of black holes. Black holes are objects in space that are so massive and compact they were described by Einstein as “bending” space. Conventional thinking asserts that black holes swallow everything that gets too close and that nothing can escape, but the study by Prof. Samuel Braunstein and Dr. Manas Patra suggests that information could escape from black holes after all. [more]
Subatomic Quantum Memory in Diamond Demonstrated
ScienceDaily (June 28, 2011) — Physicists working at the University of California, Santa Barbara and the University of Konstanz in Germany have developed a breakthrough in the use of diamond in quantum physics, marking an important step toward quantum computing. The results are reported in this week’s online edition of Nature Physics. [more]
Physicists break record for extreme quantum state
Physicists in China have broken their own record for the number of photons entangled in a “Schrödinger’s cat state”. They have managed to entangle eight photons in the state, beating the previous record of six, which they set in 2007. The Schrödinger’s cat state plays an important role in several quantum-computing and metrology protocols. However, it is very easily destroyed when photons interact with their surroundings, prompting the researchers to describe its creation in eight photons as “state of the art” in quantum control. [more]
Quarks break free at two trillion degrees
Physicists in the US, India and China have calculated that quarks and gluons can break free from their confinement inside protons and neutrons at a temperature of around two trillion degrees Kelvin – the temperature of the universe a fraction of a second after the Big Bang. The researchers arrived at this figure by combining the results of supercomputer calculations and heavy-ion collision experiments. They say that it puts our knowledge of quark matter on a firmer footing.[more]
Physicists create a living laser
To date, lasers have been built from inanimate materials, such as purified gases, synthetic dyes or semiconductors. But now physicists in the US have shown how to induce lasing in a single living biological cell. By shining intense blue light onto fluorescent protein molecules in a cell, the team made the molecules generate intense, monochromatic, directional green light. This phenomenon could potentially be used to distinguish cancerous cells from healthy cells, claim the researchers.[more]
