Knowing the period-luminosity relation for local RR Lyrae-type variable stars allows the distance of more distant stars of this type to be determined. The distance of RR Lyrae remained uncertain until 2002 when the Hubble Space Telescope was used to fix its distance within a 5% margin of error. The result was . When combined with measurements from the Hipparcos satellite and other sources, the result is a distance estimate of .
Rosalind Russell
Rosalind Russell (born June 4, 1907 - died November 28, 1976) was an American actress who acted in lots of stage plays and many movies. She played a fast talking newspaper reporter in the 1940 screwball movie "His Girl Friday" and Mame Dennis in the movie "Auntie Mame". Russell was born in Connecticut. She died from breast cancer at age sixty-nine in Beverly Hills, California.
L'Osservatore Romano
L'Osservatore Romano is the official newspaper of the Holy See. It was first published in 1861. It is not used for official publications, they appear in Acta Apostolicae Sedis. L'Osservatore Romano is published daily, in Italian. There are also weekly or monthly editions in many other languages.
Mirrors (song)
"Mirrors" is a 2013 song by American singer Justin Timberlake. The song is on his third studio album "The 20/20 Experience". "Mirrors" was released 11 February 2013.
Galactic Centre
The Galactic Centre (or Galactic Center) is the rotational center of the Milky Way galaxy.
It is a supermassive black hole of 4.100 ± 0.034 million solar masses. It powers the compact radio source Sagittarius A*.
It is away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest.
Enterococcus
Enterococcus is a genus of lactic acid bacteria of the phylum Firmicutes.
Enterococci are Gram-positive cocci that often occur in pairs or short chains. They look like streptococci. Two species are regular gut flora organisms in the intestines of humans: "E. faecalis" (90-95%) and "E. faecium" (5-10%).
Enterococci are "facultative anaerobic organisms". This means they can live in both oxygen-rich and oxygen-poor environments.
Members of the genus "Enterococcus" were classified as Group D "Streptococcus" until 1984. Genomic DNA analysis showed they were a separate genus.
Important infections caused by "Enterococcus" include urinary tract infections, bacterial endocarditis, diverticulitis, and meningitis.
Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin. Urinary tract infections can be treated by antibiotics, but many virulent strains of "Enterococcus" are resistant. From a medical standpoint, an important feature of this genus is the high level of antibiotic resistance. This rules out some important antibiotics.
Mycoplasma
Mycoplasma is a genus of bacteria. They do not have a cell wall around their cell membrane.
They are gram-negative, and need sterols such as cholesterol for growth. Many common antibiotics such as penicillin that target cell walls do not affect mycoplasma. "Mycoplasma" are the smallest bacterial cells yet discovered. They are typically about 0.1  µm in diameter.
Many species are parasitic, pathogenic or saprophytic, and can survive without oxygen. In humans, "M. genitalium" causes urethritis, and "M. pneumoniae" is a common cause of pneumonia.
Micropaleontology
Micropaleontology (also sometimes spelled as micropalaeontology) is the branch of paleontology that studies microfossils. Microfossils are fossils generally not larger than four millimeters, and commonly smaller than one millimeter. A microscope is used to study them. Every kingdom of organisms is represented in the microfossil record. Microfossils can provide important information about the ecology in the past.
People who study micropaleontology are called micropaleontologists. Taxonomy and statistics are important parts of micropaleontology.
Microfossils are most common in sediment that forms beneath water, particularly ocean water or lake water. Very old microfossils may be found in rock. Special techniques are used to separate microfossils from rock. For example, the shells of diatoms and some other organisms are made of silica; other materials in the rock can sometimes be removed with acid, leaving just the silica shells.
Micropaleontology can be divided into four areas of study. The different areas of study use different techniques to separate the microfossils. This is because the microfossils are made of different minerals:
The area of study for pollen and spores, including fossils, is called palynology.
Palynology
Palynology is the study of very small natural particles. The word literally means the "study of dust". A palynologist is someone whose job is to identify what the particles are. Samples of particles can come from the air or water or soil or rocks. They could be organic and inorganic. Micropaleontology is a related area of study; it involves very small fossils.
A palynologist uses a microscope. They may also use chemical tests to find out what a particle is made of.
The methods used to study fossils in micropaleontology and in palynology are often different. Micropaleontology often involves breaking and dissolving rocks. Palynology often involves soil or sediment.
The main work of a palynologist is to identify each particle. Many different kinds of particles might be in the same sample. They may include:
When the palynologist knows what particles are present in a sample, they may be able to say what the temperature or environmental chemistry was like where the sample came from. They may also be able to say where the sample came from.
Palynology is used in forensic science to learn where something came from, by looking at the particles in or on it.
Palynology is also very important in the study of climate history. In bodies of water such as lakes, ponds, and the ocean, sediment builds up slowly, so that the oldest sediment is at the bottom. There are ways to take a sample of the sediment that doesn't disturb the layers (either using a tube, or by freezing).
In glacial lakes, the sediment may have varves, which are two layers per year that are different colours. If there are varves, a lot of detailed information can be discovered in a core sample.
Delta Cephei
Delta Cephei (δ Cep, δ Cephei) is a binary star system about 887 light-years away in the northern constellation of Cepheus, the King. At this distance, the apparent magnitude of the star is reduced by 0.23 as a result of gas and dust along the line of sight.
Delta Cephei, found by John Goodricke in 1784, was only the second Cepheid variable discovered. It is very important because its distance is extremely well known. This is partly because it is in a star cluster, close enough for the precise Hubble Space Telescope/Hipparcos parallaxes to give a good result. As a result, it is known as a "fundamental distance calibrator", or absolute candle. Delta Cephei is a classical, or type I, Cepheid variable.
The only Cepheid variable closer to us is Polaris, the North Star, whose distance is still not exactly known.
Delta Cephei is emitting around 2,000 times the Sun's luminosity. This is producing a strong stellar wind, which, with the pulsations and shocks in the star's atmosphere, is ejecting mass at the rate of masses per year. This is the equivalent to the mass of the Sun roughly every million years. The matter is flowing outward at a velocity of about 350 km s. This expelled gas forms a nebula about one parsec across, centered on Delta Cephei, and contains 0.07–0.21 solar masses of neutral hydrogen. A bow shock is being formed where the stellar wind is colliding with the surrounding interstellar medium.
Quantum state