Crater constellation is located in the southern sky. Its name means ‘cup’ in Latin. Crater is the 53rd constellation in size, occupying an area of 282 square degrees. It is located in the second quadrant of the southern hemisphere (SQ2) and can be seen at latitudes between +65° and -90°. The neighboring constellations are Corvus, Hydra, Leo, Sextans, and Virgo.
[http://www.constellation-guide.com/constellation-list/crater-constellation/]
Corvus and Crater, two adjacent constellations on the back of Hydra, shown in the Uranographia of Johann Bode (1801). In ancient Greece, a krater was a bowl or vase used for mixing wine with water, rather than a cup as we know it.
[http://www.ianridpath.com/startales/corvusandcrater.htm]
Crater is identified with a story from Greek mythology in which a crow or raven serves Apollo, and is sent to fetch water, but it rests lazily on the journey, and after finally obtaining the water in a cup, takes back a water snake as an excuse. According to the myth, Apollo saw through the fraud, and angrily cast the crow, cup, and snake, into the sky. The constellations of Corvus the crow and Hydra the water-snake are also identified with this myth.
In Chinese astronomy, the stars of Crater are located within the constellation of the Vermillion Bird of the South (Nán Fāng Zhū Què).
In the Society Islands, Crater was recognized as a constellation called Moana-ohu-noa-ei-haa-moe-hara.
[http://www.peoplesguidetothecosmos.com/constellations/crater.htm]
Constellation of Corvus and Crater
[http://www.davidmalin.com/fujii/source/Crt.html]
Alpha Crateris, traditionally called Alkes, is an orange-hued giant star of magnitude 4.1, 174 light-years from Earth. Its traditional name means ‘the cup.’
Beta Crateris (also Al Sharas, meaning ‘the rib’) is a blue-white hued star of magnitude 4.5, 266 light-years from Earth.
Gamma Crateris is a double star divisible in small amateur telescopes. The primary is a white star of magnitude 4.1, 84 light-years from Earth. The secondary is of magnitude 9.6.
Delta Crateris is the brightest star in Crater at magnitude 3.6. 195 light-years away, it is an orange-hued giant star.
R Crateris is a semi-regular variable of type SRb and a spectral classification of M7. It has a magnitude of 9.8-11.2 and an optical period of 160 days.
SZ Crateris is a magnitude 8.1 variable star. It is a nearby star system located about 44 light years from the Sun. It is also identified as Gliese 425, and in the past it was known as Abt’s Star.
HD 96167 b’s orbit compared to the orbit of Mars (1.5AU) in the Solar System
HD 96167 is an 8th magnitude G-type subgiant star located approximately 280 light years away in the constellation of Crater. It is larger, brighter and more massive than our Sun. The star is metal rich and around 3.8 ± 1 Gyr old.
HD 96167 b is orbiting HD 96167. It is a Jupiter-type planet that orbits at 1.3 AU in extremely elliptical orbit. The planet was discovered on April 17, 2009.
[https://en.wikipedia.org/wiki/HD_96167]
[https://en.wikipedia.org/wiki/HD_96167_b]
BD-10°3166 is a K-type main sequence star approximately 218 light-years away in the constellation of Crater. A recent photometric distance measurement gives an approximate distance of 218 light years. Although the estimate is only crude, it is probably good enough to exclude a suggested companion star, LP 731-076, being its true binary star companion.
The star is very enriched with metals, being about three times as metal-rich as the Sun. Planets are common around such stars, and BD-10°3166 is not an exception. In 2000, the California and Carnegie Planet Search team discovered a hot Jupiter-type extrasolar planet, that has a minimum mass less than half that of Jupiter’s, and which takes only 3.49 days to revolve around BD-10°3166.
[https://en.wikipedia.org/wiki/BD-10%C2%B03166]
PKS 1127-145: Chandra Scores A Double Bonus With A Distant Quasar
The X-ray image of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light years from Earth, shows an enormous X-ray jet that extends at least a million light years from the quasar. The jet is likely due to the collision of a beam of high-energy electrons with microwave photons.
The high-energy beam is thought to have been produced by explosive activity related to gas swirling around a supermassive black hole. The length of the jet and the observed bright knots of X-ray emission suggest that the explosive activity is long-lived but intermittent.
On their way to Earth, the X-rays from the quasar pass through a galaxy located 4 billion light years away. Atoms of various elements in this galaxy absorb some of the X-rays, and produce a dimming of the quasar’s X-rays, or an X-ray shadow. In a similar way, when our body is X-rayed, our bones produce an X-ray shadow. By measuring the amount of absorption astronomers were able to estimate that 4 billion years ago, the gas in the absorbing galaxy contained a much lower concentration of oxygen relative to hydrogen gas than does our galaxy- about 5 times lower. These observations will give astronomers insight into how the oxygen supply of galaxies is built up over the eons.
[http://chandra.si.edu/photo/2002/1127/index.html]
RX J1131-1231: Chandra & XMM-Newton Provide Direct Measurement of Distant Black Hole’s Spin.
Astronomers have directly measured the spin of a supermassive black hole in a quasar that is located 6 billion light years away. This is the most distant black hole where such a measurement has been made. Black holes are defined by just two simple characteristics: mass and spin. Finding out how quickly black holes are spinning reveals important information about how they grow over time.
Multiple images of a distant quasar are visible in this combined view from NASA’s Chandra X-ray Observatory and the Hubble Space Telescope. The Chandra data, along with data from ESA’s XMM-Newton, were used to directly measure the spin of the supermassive black hole powering this quasar.
Gravitational lensing by an intervening elliptical galaxy has created four different images of the quasar, shown by the Chandra data in pink. Such lensing, first predicted by Einstein, offers a rare opportunity to study regions close to the black hole in distant quasars, by acting as a natural telescope and magnifying the light from these sources. The Hubble data in red, green and blue shows the elliptical galaxy in the middle of the image, along with other galaxies in the field.
The quasar is known as RX J1131-1231 (RX J1131 for short), located about 6 billion light years from Earth. Using the gravitational lens, a high quality X-ray spectrum - that is, the amount of X-rays seen at different energies - of RX J1131 was obtained.
The X-rays are produced when a swirling accretion disk of gas and dust that surrounds the black hole creates a multimillion-degree cloud, or corona near the black hole. X-rays from this corona reflect off the inner edge of the accretion disk. The reflected X-ray spectrum is altered by the strong gravitational forces near the black hole. The larger the change in the spectrum, the closer the inner edge of the disk must be to the black hole.
The authors of the new study found that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon, the point of no return for in-falling matter. This implies that the black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.
This result is important because black holes are defined by just two simple characteristics: mass and spin. While astronomers have long been able to measure black hole masses very effectively, determining their spins have been much more difficult.
These spin measurements can give researchers important clues about how black holes grow over time. If black holes grow mainly from collisions and mergers between galaxies they should accumulate material in a stable disk, and the steady supply of new material from the disk should lead to rapidly spinning black holes. In contrast if black holes grow through many small accretion episodes, they will accumulate material from random directions. Like a merry go round that is pushed both backwards and forwards, this would make the black hole spin more slowly.
The discovery that space-time at the black hole’s event horizon is spinning at over half the speed of light suggests that RX J1131, observed at a distance of six billion light years, corresponding to an age about 7.7 billion years after the Big Bang, has grown via mergers, rather than pulling material in from different directions.
[http://chandra.si.edu/photo/2014/rxj1131/index.html]
NGC 3511 is a spiral galaxy with a slight bar, seen nearly from the edge. It is a member of the galaxy cluster Abell 1060. This galaxy is magnitude 12, and is 4' × 1' in size. Right nearby, 30" away, is NGC 3513, another SB-class spiral:
NGC 3511 & 3513
Two spiral galaxies tilted at different angles to us. Note that the one on the right shows a bluish appearance due to its ‘face-on’ orientation. NGC 3511, on the left, is tilted. Its color is more red since more of the light waves have to travel through its mid-plane dust layer.
[http://www.tedwolfe.com/?attachment_id=376]
NGC 3981
[http://www.caelumobservatory.com/obs/n3981.html]
NGC 3981 is a spiral galaxy with two wide spiral arms. It is magnitude 12 with a diameter of 3'. This galaxy was discovered by William Herschel in 1785.
Crater 2 is a dwarf galaxy discovered orbiting the Milky Way, located approximately 380,000 ly from Earth. Crater 2 was identified in imaging data from the VST ATLAS survey. The galaxy has a half-light radius of ∼1100 pc, making it the fourth largest satellite of the Milky Way. It has an angular size about double of that of the moon:
[https://en.wikipedia.org/wiki/Crater_2_dwarf_galaxy]
[https://en.wikipedia.org/wiki/Crater_%28constellation%29]
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