C/2002 V1 (NEAT) Comet C/2002 V1 (NEAT) is a non-periodic comet that appeared in November 2002.[1] The comet peaked with an apparent magnitude of approximately –0.5, making it the 8th brightest comet seen since 1935.[4] It was seen by SOHO in February 2003. At perihelion the comet was only 0.099258 AU (14,848,800 km; 9,226,600 mi) from the Sun. (Slight controversy arose when the comet failed to break up when it approached the sun, as expected by some scientists if it were a small comet.)[5] 99942 Apophis. 99942 Apophis (/əˈpɒfɪs/, previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a probability of up to 2.7% that it would hit Earth in 2029.
Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a small region no more than about 800 m (half a mile) wide,[7] that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small.
During the short time when it had been most concerning, Apophis set the record for highest rating on the Torino Scale, reaching level 4.[8] Close approaches[edit] C/2010 X1. Comet C/2010 X1 (Elenin) is a long-period comet discovered by Russian amateur astronomer Leonid Elenin on December 10, 2010, through remote control of the International Scientific Optical Network's robotic observatory near Mayhill in the U.S. state of New Mexico.
The discovery was made using the automated asteroids discovery program CoLiTec. At the time of discovery, the comet had an apparent magnitude of 19.5,[2] making it about 150,000 times fainter than can be seen with the naked eye.[5] The discoverer, Leonid Elenin, originally estimated that the comet nucleus was 3–4 km in diameter,[6] but more recent estimates place the pre-breakup size of the comet at 2 km.[7] Comet Elenin started disintegrating in August 2011,[8] and as of mid-October 2011 was not visible even using large ground-based telescopes.[9] Brightness[edit] Original and future orbit[edit] References[edit] External links[edit] Arcturus. Arcturus is a type K1.5 IIIpe orange giant star, with an absolute magnitude of −0.30.
It has likely exhausted its hydrogen from the core and is currently in its active hydrogen shell burning phase. It will continue to expand before entering horizontal branch stage of its life cycle. Observational history[edit] As one of the brightest stars in the sky, Arcturus has been significant to observers since antiquity. In Mesopotamia, it was linked to the god Enlil, and also known as Shudun, "yoke",[6] or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC.[7] According to the Hipparcos satellite, Arcturus is 36.7 light years (11.3 parsecs) from Earth, relatively close in astronomical terms.
Visibility[edit] Arcturus is visible from both Earth's hemispheres as it is located 19° north of the celestial equator. Physical properties[edit] Oscillations[edit] Element abundance[edit] Kinematics[edit] Possible planetary system[edit] In Arabic[edit] Pleiades. Observational history[edit] The Pleiades are a prominent sight in winter in both the Northern Hemisphere and Southern Hemisphere, and have been known since antiquity to cultures all around the world, including the Māori, Aboriginal Australians, the Persians, the Arabs (known as Thurayya), the Chinese, the Japanese, the Maya, the Aztec, and the Sioux and Cherokee. In Tamil culture this star cluster is attributed to Lord Murugan (Lord Murugan raised by the six sisters known as the Kārththikai Pengal and thus came to be known as Kārtikeyan). In Sanskrit he is known as Skanda. The Nebra sky disk, dated c. 1600 BC. The cluster of dots in the upper right portion of the disk is believed to be the Pleiades.
The Babylonian star catalogues name the Pleiades MUL.MUL or "star of stars", and they head the list of stars along the ecliptic, reflecting the fact that they were close to the point of vernal equinox around the 23rd century BC. Animation of proper motion in 400,000 years (cross-eyed viewing. Zeta Reticuli. Sirius. Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite,[5][19][20] the Sirius system is one of Earth's near neighbors. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to recede, but it will continue to be the brightest star in the Earth's sky for the next 210,000 years.[21] Sirius A is about twice as massive as the Sun (M☉) and has an absolute visual magnitude of 1.42.
It is 25 times more luminous than the Sun[7] but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and 300 million years old.[7] It was originally composed of two bright bluish stars. Observational history[edit] The indigenous Boorong people of northwestern Victoria named Sirius as Warepil.[42] Kinematics[edit] Dogon[edit] Draco Dwarf. Characteristics[edit] Paul W. Hodge analyzed the distribution of its stars in 1964 and concluded that its ellipticity was 0.29 ± 0.04.[6] Recent studies have indicated that the galaxy may potentially hold large amounts of dark matter.[7] Having an absolute magnitude of -8.6[c] and a total luminosity of only 2×105 L☉, it is one of the faintest companions to our Milky Way.[4] Draco Dwarf contains many red giant branch (RGB) stars; five carbon stars have been identified in Draco Dwarf and four likely asymptotic giant branch (AGB) stars have been detected.[4] The Draco Dwarf is estimated to be about 80 ± 10 kpc[2][3] from earth and span a distance of 830 ± 100 × 570 ± 70 pc.
RR Lyrae[edit] In 1961, Walter Baade and Henrietta H. [edit] Dark matter[edit] Recently, dwarf spheroidal galaxies have become key objects for the study of dark matter. At large radii, radial velocity dispersion exhibit strange behavior. Notes[edit] References[edit] External links[edit] Coordinates: 17h 20m 12.4s, +57° 54′ 55″ Andromeda–Milky Way collision. The Andromeda–Milky Way collision is a galaxy collision predicted to occur in about 4 billion years between the two largest galaxies in the Local Group—the Milky Way (which contains our Solar System and Earth) and the Andromeda Galaxy.,[1][2][3] although the stars involved are sufficiently far apart that it is improbable that many of them will individually collide.[4] Stellar collisions[edit] While the Andromeda Galaxy contains about 1 trillion (1012) stars and the Milky Way contains about 300 billion (3×1011), the chance of even two stars colliding is negligible because of the huge distances between the stars.
For example, the nearest star to the Sun is Proxima Centauri, about 4.2 light-years (4.0×1013 km; 2.5×1013 mi) or 30 million (3×107) solar diameters away. If the Sun were a ping-pong ball, Proxima Centauri would be a pea about 1,100 km (680 mi) away, and the Milky Way would be about 30 million km (19 million mi) wide, about 1⁄5 the distance from the Earth to the Sun. Satellite galaxy. A satellite galaxy is a galaxy that orbits a larger galaxy due to gravitational attraction.[1] Although a galaxy is made of a large number of objects (such as stars, planets, and nebulae) that are not connected to each other, it has a center of mass, which represents a weighted average (by mass) of the positions of each component object.
This is similar to how an everyday object has a center of mass which is the weighted average of the positions of all its component atoms.[1] Galaxies which encounter one another from certain directions may interact: collide, merge, rip each other apart, or transfer some member objects. In these situations, it can be difficult to tell where one galaxy ends and where another begins. "Collisions" between galaxies do not necessarily involve collisions between objects from one galaxy and objects from the other, since galaxies are mostly empty space. Satellite galaxies of the Milky Way, our own galaxy. References[edit] See also[edit] Universe. There are many competing theories about the ultimate fate of the universe.
Physicists remain unsure about what, if anything, preceded the Big Bang. Many refuse to speculate, doubting that any information from any such prior state could ever be accessible. There are various multiverse hypotheses, in which some physicists have suggested that the Universe might be one among many or even an infinite number of universes that likewise exist.[11][12] Historical observation XDF size compared to the size of the Moon – several thousand galaxies, each consisting of billions of stars, are in this small view. XDF (2012) view – each light speck is a galaxy – some of these are as old as 13.2 billion years[13] – the visible Universe is estimated to contain 200 billion galaxies. XDF image shows fully mature galaxies in the foreground plane – nearly mature galaxies from 5 to 9 billion years ago – protogalaxies, blazing with young stars, beyond 9 billion years. History Etymology, synonyms and definitions.