The image shows a pair of colossal stars, WR 25 and Tr16-244, located within the open cluster Trumpler 16. This cluster is embedded within the Carina Nebula, an immense cauldron of gas and dust that lies approximately 7500 light-years from Earth in the constellation of Carina, the Keel. WR 25 is the brightest, situated near the centre of the image. The neighbouring Tr16-244 is the third brightest, just to the upper left of WR 25. The second brightest, to the left of WR 25, is a low mass star located much closer to the Earth than the Carina Nebula.
Credit: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain)
Urania’s Mirror; or, a view of the Heavens is a set of 32 astronomical star chart cards, first published in November 1824. They had illustrations based on Alexander Jamieson’s A Celestial Atlas, but the addition of holes punched in them allowed them to be held up to a light to see a depiction of the constellation’s stars. They were engraved by Sidney Hall, and were said to be designed by “a lady”, but have since been identified as the work of the Reverend Richard Rouse Bloxam, an assistant master at Rugby School.
The cover of the box-set showed a depiction of Urania, the muse of astronomy, and came with a book entitled A Familiar Treatise on Astronomy… written as an accompaniment. Peter Hingley, the researcher who solved the mystery of who designed the cards a hundred and seventy years after their publication, considered them amongst the most attractive star chart cards of the many produced in the early 19th century.
Orion is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous and recognizable constellations in the night sky. It was named after Orion, a hunter in Greek mythology. Its brightest stars are Rigel (Beta Orionis) and Betelgeuse (Alpha Orionis), a blue-white and a red supergiant, respectively.
Orion’s seven brightest stars form a distinctive hourglass-shaped asterism, or pattern, in the night sky. Four stars—Rigel, Betelgeuse, Bellatrix and Saiph—form a large roughly rectangular shape, in the centre of which lie the three stars of Orion’s Belt—Alnitak, Alnilam and Mintaka.
Orion’s Belt or The Belt of Orion is an asterism within the constellation. It consists of the three bright stars Zeta (Alnitak), Epsilon (Alnilam), and Delta (Mintaka). Alnitak is around 800 light years away from earth and is 100,000 times more luminous than the Sun; much of its radiation is in the ultraviolet range, which the human eye cannot see. Alnilam is approximately 1340 light years away from Earth, shines with magnitude 1.70, and with ultraviolet light is 375,000 times more luminous than the Sun. Mintaka is 915 light years away and shines with magnitude 2.21. It is 90,000 times more luminous than the Sun and is a double star: the two orbit each other every 5.73 days.
Around 20 October each year the Orionid meteor shower (Orionids) reaches its peak. Coming from the border with the constellation Gemini as many as 20 meteors per hour can be seen. The shower’s parent body is Halley’s Comet.
M78 (NGC 2068) is a nebula in Orion. With an overall magnitude of 8.0, it is significantly dimmer than the Great Orion Nebula that lies to its south; however, it is at approximately the same distance, at 1600 light-years from Earth. It can easily be mistaken for a comet in the eyepiece of a telescope.
Another fairly bright nebula in Orion is NGC 1999, also close to the Great Orion Nebula. It has an integrated magnitude of 10.5 and is 1500 light-years from Earth. The variable star V380 Orionis is embedded in NGC 1999.
Another famous nebula is IC 434, the Horsehead Nebula, near ζ Orionis. It contains a dark dust cloud whose shape gives the nebula its name.
NGC 2174 is an emission nebula located 6400 light-years from Earth.
Besides these nebulae, surveying Orion with a small telescope will reveal a wealth of interesting deep-sky objects, including M43, M78, as well as multiple stars including Iota Orionis and Sigma Orionis. A larger telescope may reveal objects such as Barnard’s Loop and the Flame Nebula (NGC 2024), as well as fainter and tighter multiple stars and nebulae.
All of these nebulae are part of the larger Orion Molecular Cloud Complex, which is located approximately 1,500 light-years away and is hundreds of light-years across. It is one of the most intense regions of stellar formation visible within our galaxy.
Combined image data from the massive, ground-based VISTA telescope and the Hubble Space Telescope was used to create this wide perspective of the interstellar landscape surrounding the famous Horsehead Nebula.
Composition and Processing: Robert Gendler Image Data: ESO, VISTA, HLA, Hubble Heritage Team (STScI/AURA)
Astronomers from the BRITE (BRight Target Explorer) Constellation project and Ritter Observatory have discovered a repeating one-per-cent spike in the light of a very massive star which could change our understanding of such stars. Iota Orionis is a binary star system and is easily visible with the naked eye, being the brightest star in the constellation Orion’s sword. Its unique variability, reported in the journal Monthly Notices of the Royal Astronomical Society, was discovered using the world’s smallest astronomical space satellites, referred to as “nanosats”. “As the first functional nanosatellite astronomy mission, the BRITE-Constellation is at the vanguard of this coming space revolution,” said Canadian BRITE-Constellation principal investigator Gregg Wade, of Royal Military College of Canada, Ont.
The light from Iota Orionis is relatively stable 90 per cent of the time but then dips rapidly followed by a large spike. “The variations look strikingly similar to an electrocardiogram showing the sinus rhythms of the heart, and are known as heartbeat systems,” said Herbert Pablo, the project’s principal investigator, a post-doctoral researcher at Université de Montréal and member of the Centre for Research in Astrophysics of Quebec (CRAQ). This unusual variation is the result of the interaction of two stars in a highly elliptical 30-day orbit around each other.
While the two stars spend the majority of their time far apart, they do come nearly eight times closer together for a short time once every orbit. At that point the gravitational force between the two stars becomes so strong that it rapidly distorts their shapes, like pulling on the end of a balloon, causing the unusual changes in light. Iota Orionis represents the first time this effect has been seen in such a massive system (35 times the mass of the Sun), an order of magnitude larger than any in previously known systems, and allows for direct determination of the masses and radii of the components.
A shaking star is like an open book
Even more interesting is that these systems allow us to peer inside the stars themselves. “The intense gravitational force between the stars as they move closer together triggers quakes in the star, allowing us to probe the star’s inner workings, just as we do for the Earth’s interior during Earthquakes,” said Pablo. The phenomenon of quakes is very rare in massive stars in general and this is the first time induced quakes have ever been seen in a star this massive, let alone one whose mass and radius are known. These unprecedented quakes have also led to the first real clues to how such stars will evolve.
Astronomers are hopeful that this discovery will provide the initiative to search for other such systems, creating a fundamental shift in how we study the evolution of massive stars. This is important, since massive stars are laboratories of elements essential to human life.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices. The 88 modern constellations are formally defined regions of the sky together covering the entire celestial sphere.
Origins for the earliest constellations likely goes back to prehistory, whose now unknown creators collectively used them to related important stories of either their beliefs, experiences, creation or mythology. As such, different cultures and countries often adopted their own set of constellations outlines, some that persisted into the early 20th Century. Adoption of numerous constellations have significantly changed throughout the centuries. Many have varied in size or shape, while some became popular then dropped into obscurity. Others were traditionally used only by various cultures or single nations.
The Western-traditional constellations are the forty-eight Greek classical patterns, as stated in both Aratus’s work Phenomena or Ptolemy’s Almagest — though their existence probably predates these constellation names by several centuries. Newer constellations in the far southern sky were added much later during the 15th to mid-18th century, when European explorers began travelling to the southern hemisphere. Twelve important constellations are assigned to the zodiac, where the Sun, Moon, and planets all follow the ecliptic. The origins of the zodiac probably date back into prehistory, whose astrological divisions became prominent around 400BCE within Babylonian or Chaldean astronomy.
In 1928, the International Astronomical Union (IAU) ratified and recognized 88 modern constellations, with contiguous boundaries defined by right ascension and declination. Therefore, any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems give the constellation where a given celestial object is found along with a designation in order to convey an approximate idea of its location in the sky. e.g. The Flamsteed designation for bright stars consists of a number and the genitive form of the constellation name.