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Vega
Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, and one of the most luminous stars in the Sun's neighborhood. It is the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus. Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun". Vega was the northern pole star around 12,000 BCE and will be so again around the year 13,727, when its declination will be . Vega was the first star other than the Sun to have its image and spectrum photographed. It was one of the first stars whose distance was estimated through parallax measurements. Vega has functioned as the baseline for calibrating the photometric brightness scale and was one of the stars ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyra
, from ; pronounced: ) is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was often represented on star maps as a vulture or an eagle carrying a lyre, and hence is sometimes referred to as Vultur Cadens or Aquila Cadens ("Falling Vulture" or "Falling Eagle"), respectively. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus. Lyra is nearly overhead in temperate northern latitudes shortly after midnight at the start of summer. From the equator to about the 40th parallel south it is visible low in the northern sky during the same (thus winter) months. Vega, Lyra's brightest star, is one of the brightest stars in the night sky, and forms a corner of the famed Summer Triangle asterism. Beta Lyrae is the prototype of a class of binary stars known as Beta Lyrae variables. These binary stars are so close to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debris Disk
A debris disk (American English), or debris disc ( Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris disks are found around stars with mature planetary systems, including at least one debris disk in orbit around an evolved neutron star. Debris disks can also be produced and maintained as the remnants of collisions between planetesimals, otherwise known as asteroids and comets. As of 2001, more than 900 candidate stars had been found to possess a debris disk. They are usually discovered by examining the star system in infrared light and looking for an excess of radiation beyond that emitted by the star. This excess is inferred to be radiation from the star that has been absorbed by the dust in the disk, then re-radiated away as infrared energy. Debris disks are often described as massive analogs to the debris in the Solar System. Most kn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Scuti Variable
A Delta Scuti variable (sometimes termed dwarf cepheid when the V-band amplitude is larger than 0.3 mag.) is a class of pulsating star, comprising several sub-classes of object with A- or F-type spectra. The variables follow a period-luminosity relation in certain passbands like other standard candles such as Cepheids. and, together with classical cepheids, are important standard candles. They have been used to establish the distance to the Large Magellanic Cloud, globular clusters, open clusters, and the Galactic Center. The OGLE and MACHO surveys have detected nearly 3,000 Delta Scuti variables in the Large Magellanic Cloud. Typical brightness fluctuations of Delta Scuti variables are from 0.003 to 0.9 magnitudes in V over a period of a few hours, although the amplitude and period of the fluctuations can vary greatly. They are usually A0 to F5 type giant, subgiant, or main sequence stars. The high-amplitude Delta Scuti variables are also called AI Velorum stars, after ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Star Systems Within 25–30 Light-years
This is a list of star systems within 25–30 light-years of Earth. List See also * List of nearest stars * List of star systems within 20–25 light-years * List of star systems within 30–35 light-years * Lists of stars * List of nearest bright stars The following nearest bright stars are found within of the closest star, the Sun, and have an absolute magnitude of +8.5 or brighter, which is approximately comparable to a listing of stars more luminous than a red dwarf. Right ascension and ... * Spherical shell References {{DEFAULTSORT:Star systems within 25-30 light-years Lists of stars Star systems Lists by distance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sky, night; their immense distances from Earth make them appear as fixed stars, fixed points of light. The most prominent stars have been categorised into constellations and asterism (astronomy), asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy. A star's life star formation, begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its stellar mass, total mass mainly determines it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pole Star
A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position is close to one of the celestial poles. On Earth, a pole star would lie directly overhead when viewed from the North or the South Pole. Currently, Earth's pole stars are Polaris (Alpha Ursae Minoris), a bright magnitude 2 star aligned approximately with its northern axis that serves as a pre-eminent star in celestial navigation, and a much dimmer magnitude 5.5 star on its southern axis, Polaris Australis (Sigma Octantis). From around 1700 BC until just after 300 AD, Kochab (Beta Ursae Minoris) and Pherkad (Gamma Ursae Minoris) were twin northern pole stars, though neither was as close to the pole as Polaris is now. History In classical antiquity, Beta Ursae Minoris (Kochab) was closer to the celestial north pole than Alpha Ursae Minoris. While there was no naked-eye star close to the pole, the midpoint between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Celestial Hemisphere
The northern celestial hemisphere, also called the Northern Sky, is the Northern Hemisphere, northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere diurnal motion, appears to rotate westward around a celestial pole, polar axis due to Earth's rotation. At any given time, the entire Northern Sky is visible from the geographic North Pole, while less of the hemisphere is visible the latitude, further south the observer is located. The southern counterpart is the southern celestial hemisphere. Astronomy In the context of astronomical discussions or writing about celestial cartography, the northern celestial hemisphere may be referred to as the Northern Hemisphere. For star chart, celestial mapping, astronomers may conceive the sky like the inside of a sphere divided into two halves by the celestial equator. The Northern Sky or Northern Hemisphere is therefore the half of the celestial sphere that is north of the celestial equato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Rotation
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge due to centrifugal force. As stars are not solid bodies, they can also undergo differential rotation. Thus the equator of the star can rotate at a different angular velocity than the higher latitudes. These differences in the rate of rotation within a star may have a significant role in the generation of a stellar magnetic field. In its turn, the magnetic field of a star interacts with the stellar wind. As the wind moves away from the star its angular speed decreases. The magnetic field of the star interacts with the wind, which applies a drag to the stellar rotation. As a result, angular momentum is transferred from the star to the wind, and over time this gradually slows the star's rate of rotation. Measurement Unless a star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Brightest Stars
This is a list of stars arranged by their apparent magnitude – their brightness as observed from Earth. It includes all stars brighter than magnitude +2.50 in visible light, measured using a ''V''-band filter in the UBV photometric system. Stars in binary systems (or other multiples) are listed by their ''total'' or ''combined'' brightness if they appear as a single star to the naked eye, or listed separately if they do not. As with all magnitude systems in astronomy, the scale is logarithmic and inverted i.e. lower/more negative numbers are brighter. Most stars on this list appear bright from Earth because they are nearby, not because they are intrinsically luminous. For a list which compensates for the distances, converting the ''apparent'' magnitude to the ''absolute'' magnitude, see the list of most luminous stars. Measurement The Sun is the brightest star as viewed from Earth, at −26.78 mag. The second brightest is Sirius at −1.46 mag. Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arcturus
, - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is a red giant star in the Northern celestial hemisphere, northern constellation of Boötes, and the brightest star in the constellation. It has the Bayer designation α Boötis, which is Latinisation of names, Latinized to Alpha Boötis and abbreviated Alf Boo or α Boo. With an apparent visual magnitude of −0.05, it is the List of brightest stars, fourth-brightest star in the night sky and the brightest in the northern celestial hemisphere. Arcturus forms one corner of the Spring Triangle Asterism (astronomy), asterism. Located relatively close at 36.7 light-years from the Sun, Arcturus is a red giant of Stellar classification, spectral type K1.5III—an aging star around 7.1 billion years old that has used up its Stellar core, core hydrogen and stellar evolution, evolved off the main sequence. It is about the same mass Solar mass, as the Sun, but has expanded to 25 times Sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * ''Intrinsic variables'', whose luminosity actually changes periodically; for example, because the star swells and shrinks. * ''Extrinsic variables'', whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars exhibit at least some oscillation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
