Cepheus constellation lies in the northern hemisphere. It is the 27th largest constellation in the night sky, occupying an area of 588 square degrees. It is located in the fourth quadrant of the northern hemisphere (NQ4) and can be seen at latitudes between +90° and -10°. The neighboring constellations are Camelopardalis, Cassiopeia, Cygnus, Draco, Lacerta, and Ursa Minor.
[http://www.constellation-guide.com/constellation-list/cepheus-constellation/]
Cepheus in the robes of a Persian king, depicted in the Atlas Coelestis of John Flamsteed (1729)
Cepheus was the mythological king of Ethiopia. He was married to Cassiopeia, an unbearably vain woman whose boastfulness caused Poseidon to send a sea monster, Cetus, to ravage the shores of Cepheus’s kingdom. Cepheus was instructed by the Oracle of Ammon to chain his daughter Andromeda to a rock in sacrifice to the monster. She was saved by the hero Perseus, who killed the monster and claimed Andromeda for his bride. In the sky, the long-suffering Cepheus stands next to Cassiopeia, his feet extending almost to the north celestial pole. Each night he circles the pole, and as seen from Greek latitudes would have plunged head first into the sea at the lowest point, suffering the same unceremonious dunking as his vainglorious wife.
[http://www.ianridpath.com/startales/cepheus.htm]
In traditional Chinese uranography Cepheus lies across one of the quadrants symbolized by the The Black Tortoise of the North (Běi Fāng Xuán Wǔ), and Three Enclosures (Sān Yuán), that divide the sky. The name of the western constellation in modern Chinese is (xiān wáng zuò), meaning ‘the immortal king constellation.’
[https://en.wikipedia.org/wiki/Cepheus_(Chinese_astronomy)]
Cepheus, Cassiopeia and Andromeda (M31)
[http://point-of-no-23.livejournal.com/1054940.html]
[http://www.peoplesguidetothecosmos.com/constellations/cepheus.htm]
Alderamin
[https://heaven-on-earth.co.uk/project/alderamin/]
Alpha Cephei is a second magnitude star in the constellation of Cepheus near the northern pole. It has the traditional name Alderamin, an Arabic name meaning ‘the right arm.’
With a declination in excess of 62 degrees north, Alderamin is mostly visible to observers in the northern hemisphere, though the star is still visible to latitudes as far south as -27°, albeit just above the horizon. The star is circumpolar throughout all of Europe, northern Asia, Canada, and American cities as far south as San Diego. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in light-polluted cities.
Alderamin is a white Class A star, evolving off the main sequence into a subgiant, probably on its way to becoming a red giant as its hydrogen supply runs low. In 2007, the star’s apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.
Given a surface temperature of 7,740 Kelvin, stellar models yield a total luminosity for the star of about 17 times the luminosity of the Sun. Alderamin has a radius of 2.3 times the Sun’s radius and boasting a mass that is 1.74 that of the Sun. Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.
Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars. By comparison, the Sun takes almost a month to turn on its axis. It is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity- something unexpected (though not at all unusual) for a fast rotator.
Alderamin is located near the precessional path traced across the celestial sphere by the Earth’s North Pole. That means that it periodically comes within 3° of being a pole star, much as Polaris is at present. This will next occur about the year 7500 AD. The north pole of Mars lies halfway between Alderamin and the star Deneb.
[https://en.wikipedia.org/wiki/Alpha_Cephei]
Errai (Gamma Cephei), artist’s impression
[http://nameexoworlds.iau.org/exoworldsvote]
Gamma Cephei is a binary star system approximately 45 light-years away in the constellation of Cepheus. The traditional Arabic name is Errai, or Alrai, meaning ‘the shepherd.’ The primary (Gamma Cephei A) is a stellar class K1III-IV orange subgiant star; it has a red dwarf companion (Gamma Cephei B). An extrasolar planet (designated Gamma Cephei Ab, later named Tadmor) is believed to be orbiting the primary.
Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth’s northern pole star, due to the precession of the equinoxes. It will be closer to the northern celestial pole than Polaris around 3000 CE and will make its closest approach around 4000 CE. The ‘title’ will pass to ι Cephei sometime around 5200 CE.
Gamma Cephei has an apparent magnitude of 3.22, nearly all of which is accounted for by Gamma Cephei A. The primary is about 6.6 billion years old (based on Fe/H metallicity) and is on its first ascent off the main sequence. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Gamma Cephei B has a mass approximately 0.409 times that of the Sun. It is probably a red dwarf of class M4, 6.2 degrees of magnitude fainter than the primary. It is assumed to be of similar age to its primary.
Following its discovery the planet was designated Gamma Cephei Ab. Its ostensible discovery in 1988 makes it the first extrasolar planet discovered, and was based on the same radial velocity technique later used successfully by others. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Tadmor for this planet. It was submitted by the Syrian Astronomical Association and is the ancient Semitic name and modern Arabic name for the city of Palmyra, a (UNESCO) World Heritage Site.
The secondary star B orbits A at only 9.8 times the semi-major axis of A’s planet. Despite how compact the system is, the planet’s orbit is stable if it is coplanar with that of the binary companion.
[https://en.wikipedia.org/wiki/Gamma_Cephei]
X-ray image of Alfirk (Beta Cephei)
[http://www.daviddarling.info/encyclopedia/A/Alfirk.html]
Beta Cephei is a third magnitude star in the constellation Cepheus. It has the traditional Arabic name Alfirk, meaning ‘the flock’ (referring to a flock of sheep). Beta Cephei is the prototype of the Beta Cephei variable stars.
Like the star Epsilon Draconis in the constellation of Draco, Alfirk is visible primarily in the northern hemisphere, given its extreme northern declination of 70 degrees and 34 minutes. The star is nevertheless visible to most observers throughout the world reaching as far south as cities like Harare in Zimbabwe, Santa Cruz de la Sierra in Bolivia or other settlements north ± 19° South latitude. The star is circumpolar throughout all of Europe, northern Asia, and North American cities as far south as Guadalajara in west central Mexico. All other locations around the globe having a latitude greater than ±20° North will notice that the star is always visible in the night sky. Because Beta Cephei is a faint third magnitude star, it may be difficult to identify in most light polluted cities, though in rural locations the star should be easily observable.
Beta Cephei is a triple star comprising a spectroscopic binary with a magnitude 8 optical companion. Its magnitude varies between +3.15 and +3.21 with a period of 0.2 days.
Beta Cephei A is a blue giant star with a stellar classification B2IIIev. The suffix ‘ev’ stands for ‘Spectral emission that exhibits variability.’ This giant star has a radius that has been estimated at 9 solar radii and a mass of 12 solar masses. Like most high-mass B-class stars, β Cep is a relatively young star with an estimated age of around 50 million years old. Like the majority of giant stars, Beta Cephei A rotates slowly on its axis with a rotational velocity of 7 deg/day, a speed which takes the star approximately 51 days to make one complete revolution.
In 2007, the star’s apparent magnitude was recalibrated at 3.1438 and the star’s parallax was updated to 4.76 ± 0.30 mas yielding a distance of 210.1 parsecs (pc) or approximately 685 light years (ly) from Earth. Given a surface temperature of 26,700 Kelvin, theoretical calculations yield a total luminosity for the star of about 36,900 times that of the sun.
[https://en.wikipedia.org/wiki/Beta_Cephei]
Mu Cephei
[https://commons.wikimedia.org/wiki/File:Mu_cephei.jpg]
Mu Cephei is a red supergiant star in the constellation Cepheus, at the edge of the IC 1396 nebula. The deep red color of Mu Cephei was noted by William Herschel, who described it as “a very fine deep garnet color.” It is thus commonly known as Herschel’s ‘Garnet Star.’ Since 1943, the spectrum of this star has served as the M2 Ia standard by which other stars are classified.
Mu Cephei is visually nearly 100,000 times brighter than the Sun, with an absolute visible magnitude of Mv = −7.6. Summing radiation at all wavelengths gives a luminosity of around 280,000 times that of the sun (bolometric magnitude −8.8), making it one of the most luminous red supergiants in the Milky Way. It is also one of the largest stars known at 1,260 solar radii (or 877,000,000 km).
Mu Cephei is a variable star and the prototype of the obsolete class of the Mu Cephei variables. It is now considered to be a semiregular variable of type SRc. Its apparent brightness varies erratically between magnitude 3.4 and 5.1. Many different periods have been reported, but they are consistently near to either 860 days or 4,400 days.
1. Mercury < Mars < Venus < Earth
2. Earth < Neptune < Uranus < Saturn < Jupiter
3. Jupiter < Wolf 359 < Sun < Sirius
4. Sirius < Pollux < Arcturus < Aldebaran
5. Aldebaran < Rigel < Antares < Betelgeuse
6. Betelgeuse < Mu Cephei < VV Cephei A < VY Canis Majoris.
A very luminous red supergiant, Mu Cephei is likely to be the largest star visible to the naked eye, and one of the largest known. It is best seen from the northern hemisphere from August to January.
This is a runaway star with a peculiar velocity of 80.7 ± 17.7 km/s. The distance to Mu Cephei is not very well known. The Hipparcos satellite was used to measure a parallax of 0.55 ± 0.20 milliarcseconds, which corresponds to an estimated distance of 1,333- 2,857 parsecs. However, this value is close to the margin of error. A determination of the distance based upon a size comparison with Betelgeuse gives an estimate of 390 ± 140 parsecs, so it is clear that Mu Cephei is either a much larger star than Betelgeuse or much closer (and smaller and less luminous) than expected.
The star is approximately 1,300 times larger than our Sun’s solar radius, and were it placed in the Sun’s position, its radius would reach between the orbit of Jupiter and Saturn. Mu Cephei could fit over a billion Suns into its volume.
The photosphere of Mu Cephei has an estimated temperature of 3,750 K. It may be surrounded by a shell extending out to a distance at least equal to 0.33 times the star’s radius with a temperature of 2,055 ± 25 K. This outer shell appears to contain molecular gases such as CO, H2O, and SiO.
Emissions from the star suggest the presence of a wide ring of dust and water with outer radius four times that of the star. Placed in the position of our Sun, its disk would span between 6 astronomical units (within Jupiter’s orbital zone) and 12 astronomical units (beyond Saturn’s orbit).
The star is surrounded by a spherical shell of ejected material that extends outward to an angular distance of 6″ with an expansion velocity of 10 km s−1. This indicates an age of about 2,000- 3,000 years for the shell. Closer to the star, this material shows a pronounced asymmetry, which may be shaped as a torus. The star currently has a mass loss rate of 7-10 solar masses per year.
Mu Cephei is nearing death. It has begun to fuse helium into carbon, whereas a main sequence star fuses hydrogen into helium. When a supergiant star has converted elements in its core to iron, the core collapses to produce a supernova and the star is destroyed, leaving behind a vast gaseous cloud and a small, dense remnant. For a star as massive as Mu Cephei the remnant is likely to be a black hole. The most massive red super-giants will evolve back to blue super-giants or Wolf-Rayet stars before their cores collapse, and Mu Cephei appears to be massive enough for this to happen. A post-red supergiant will produce a type IIn or type II-b supernova, while a Wolf Rayet star will produce a type Ib or Ic supernova.
[https://en.wikipedia.org/wiki/Mu_Cephei]
Krüger 60 imaged in the near-infrared and in z'-band by the Robo AO telescope
[http://www.daviddarling.info/encyclopedia/K/Kruger60.html]
Kruger 60 (DO Cephei) is a binary star system located 13.15 light-years from the Sun. These red dwarf stars orbit each other every 44.6 years.
The larger, primary star is designated component A, while the secondary, smaller star is labeled component B. Component A has about 27% of the Sun’s mass and 35% of the Sun’s radius. Component B has about 18% of the Sun’s mass and 24% of the Sun’s radius. Component B is a flare star and has been given the variable star designation ‘DO Cephei.’ It is an irregular flare that typically doubles in brightness and then returns to normal over an 8-minute period.
On average, the two stars are separated by 9.5 AUs, which is roughly the average distance of Saturn from the Sun. However, their eccentric mutual orbit causes their distance to vary between 5.5 AUs at periastron, to 13.5 at apastron.
This system is orbiting through the Milky Way at a distance from the core that varies from 7- 9 kpc with an orbital eccentricity of 0.126–0.130. The closest approach to the Sun will occur in about 88,600 years when this system will come within 1.95 parsecs.
[https://en.wikipedia.org/wiki/Kruger_60]
V354 Cephei
[http://rebuild-the-universe.wikia.com/wiki/V354_Cephei]
V354 Cephei is a red supergiant variable star located within the Milky Way. It is an irregular variable located approximately 9,000 light-years away from our Sun, and is currently considered one of the largest known stars, with a radius estimate of 1,520 solar radii (1.06×109 km; 7.1 au). If it were placed in the center of the Solar System, it would extend to between the orbits of Jupiter and Saturn.
V354 Cep is too far away to have a measured parallax which would allow its distance to be determined directly. It is near the Cepheus OB1 stellar association and considered a likely member. This association is at a distance of approximately 3,500 parsecs. The luminosity, and hence the size, of V354 Cep are disputed. Estimations of the size vary between 690-1,520 solar radii. There are similar differences in the visual extinctions derived, between two and six magnitudes.
[https://en.wikipedia.org/wiki/V354_Cephei]
RW Cephei is the bright star at the left bottom
[https://jumk.de/astronomie/big-stars/rw-cephei.shtml]
RW Cephei is an orange hypergiant star in the constellation Cepheus. One of the largest stars known, RW Cephei is estimated at 1,535 solar radii (1.068×109 km; 7.14 au), which is larger than the orbit of Jupiter.
RW Cephei is also a semi-regular variable star of type SRd, meaning that it is a slowly varying yellow giant or supergiant. Its surface is subject to pulsations in temperature and luminosity. Over the past 50 to 70 years it has varied from classes G8 to M0 with no discernible pattern. Despite its variable spectral type, it has been listed as a spectral standard star for type ‘K2 0-Ia.’
The distance to RW Cephei has been estimated on the basis of its spectroscopic luminosity and is assumed to be a member of the Cepheus OB1 association at 3,500 parsecs. This is several times further than the distance implied by the Hipparcos parallax, although the apparent diameter of the star is larger than the measured parallax and variable.
The temperature intermediate between the red supergiants and yellow hypergiants, and itself varying considerably, has led to it being variously considered as a red hypergiant or yellow hypergiant.
[https://en.wikipedia.org/wiki/RW_Cephei]
VV Cep A as it appears on Celestia
VV Cephei, also known as HD 208816, is located in the constellation Cepheus, approximately 5,000 light years from Earth. It is both a B[e] star and shell star. The distance has been estimated by a variety of techniques to be around 1.5kpc, which places it within the Cepheus OB2 association.
VV Cephei is an eclipsing binary with the second longest known period. A red supergiant fills its Roche lobe when closest to a companion blue star, the latter appearing to be on the main sequence. Matter flows from the red supergiant onto the blue companion for at least part of the orbit and the hot star is obscured by a large disk of material. The supergiant primary, known as VV Cephei A, is currently recognized as one of the largest stars in the galaxy, with an estimated radius of 1,050 solar radii.
VV Cephei experiences both primary and secondary eclipses during a 20.3 year orbit. The primary eclipses totally obscure the hot secondary star and last for nearly 18 months. Secondary eclipses are so shallow that they have not been detected photometrically since the secondary obscures such a small proportion of the large cool primary star. The timing and duration of the eclipses is variable, although the exact onset is difficult to measure because it is gradual. Only Epsilon Aurigae has a longer period among eclipsing binaries.
VV Cephei also shows semiregular variations of a few tenths of a magnitude. Visual and infrared variations appear unrelated to variations at ultraviolet wavelengths. A period of 58 days has been reported in UV, while the dominant period for longer wavelengths is 118.5 days. The short wavelength variations are thought to be caused by the disc around the hot secondary, while pulsation of the red supergiant primary caused the other variations. It has been predicted that the disc surrounding the secondary would produce such brightness variability.
The spectrum of VV Cep can be resolved into two main components, originating from a cool supergiant and a hot small star surrounded by a disk. The material surrounding the hot secondary produces emission lines, including [FeII] forbidden lines, the B[e] phenomenon known from other stars surrounded by circumstellar disks. The hydrogen emission lines are double-peaked, caused by a narrow central absorption component. This is caused by seeing the disk almost edge on where it intercepts continuum radiation from the star. This is characteristic of shell stars.
The sun compared to VV Cep A
The angular diameter of VV Cephei A can be estimated using photometric methods and has been calculated at 0.00638 arcseconds. This allows a direct calculation of the actual diameter, which is in good agreement with the 1,050 solar radii derived by other methods. Analysis of the orbit and eclipses places a firm upper limit on the possible size at 1,900 solar radii. The size of the secondary is even more uncertain, since it is physically and photometrically obscured by a much larger disc several hundred solar radii across. The secondary is certainly much smaller than either the primary or the disc, and has been calculated at solar radii from the orbital solution.
The temperature of the VV Cephei stars is again uncertain, partly because there simply isn't a single temperature that can be assigned to a significantly non-spherical diffuse star orbiting a hot companion. The effective temperature generally quoted for stars is the temperature of a spherical blackbody that approximates the electromagnetic radiation output of the actual star, accounting for emission and absorption in the spectrum. VV Cephei A is fairly clearly identified as an M2 supergiant, and as such, it is given a temperature around 3,800 K. The secondary star is heavily obscured by a disk of material from the primary, and its spectrum is almost undetectable against the disc emission. Detection of some ultraviolet absorption lines narrow down the spectral type to early B and it is apparently a main-sequence star, but likely to be abnormal in several respects due to mass transfer from the supergiant. A normal star of that type would be around 10,000 times the luminosity of the Sun, 5-8 times the radius of the Sun, 15-18 times the mass of the Sun, and around 25,000K.
Although VV Cephei A is an extremely large star showing high mass loss and having some emissions lines, it is not generally considered to be a hypergiant. The emission lines are produced from the accretion disc around the hot secondary and the absolute magnitude is typical for a red supergiant.
[https://en.wikipedia.org/wiki/VV_Cephei]
Lambda Cephei
[https://it.wikipedia.org/wiki/Lambda_Cephei]
Lambda Cephei is a fifth magnitude blue supergiant star in the constellation Cepheus, one of the hottest and most luminous visible to the naked eye.
It is a hot O6.5 supergiant star at a distance of approximately 1,980 light years, whose absolute brightness around half a million times the Sun. Its radius is around 20 times that of our star, with a mass that has been estimated to be between 45 and 60 solar masses.
Lambda Cephei turns around its axis in less than three days compared to the 24.47 days that the Sun needs to complete a full rotation and seems to be single, with no companions. Its ultimate fate is to explode as a supernova leaving behind a neutron star or perhaps a black hole.
Lambda Cephei is also a runaway star that seems to have been expelled of the stellar association Cepheus OB3, that lies at 2,800 light-years, roughly 2,5 million years ago. Its motion through the interstellar medium is producing a shockwave in front of the gases that surround it and in the direction towards it moves.
[https://en.wikipedia.org/wiki/Lambda_Cephei]
L1157
L 1157 is a dark nebula in the constellation Cepheus. It was catalogued in 1962 by U.S. astronomer Beverly T. Lynds in her Catalogue of Dark Nebulae, becoming the 1157th entry in the table; hence the designation. The cloud contains an estimated 3,900 Solar masses of material. It includes protostars that are ejecting material in bipolar outflows, forming bow shocks in the surrounding ambient gas. Formamide and HCNO have been detected in these shocked regions, among other compounds.
[https://en.wikipedia.org/wiki/L1157]
Cepheus: Trunk to Bubble
Star clusters, glowing nebulae and dark dust clouds abound in Cepheus, royal constellation of the northern hemisphere. You can follow them in amazing detail across this broad skyscape, a mosaic of telescopic images spanning about 17 degrees. Beginning at the lower left, the large emission nebula is cataloged as IC 1396. Hundreds of light-years across and about 3,000 light-years distant, it contains a dark, winding, tendril-shaped feature popularly known as the Elephant’s Trunk. Near the top middle, the bright nebula with an embedded star cluster is NGC 7380. At the upper right lies NGC 7635 (the Bubble Nebula) and star cluster M52. Many of the objects highlighted have a designation from the second version of the Sharpless catalog (Sh2) and the Barnard catalog (B) of dark nebulae. Associated with star formation, the sites are telltale markers along the region’s complex of giant molecular clouds.
[http://apod.nasa.gov/apod/ap100909.html]
IC 1396 and Surrounding Star-field
Sprawling across hundreds of light-years, emission nebula IC 1396, visible on the upper right, mixes glowing cosmic gas and dark dust clouds. Stars are forming in this area, only about 3,000 light-years from Earth. This wide angle view also captures surrounding emission and absorption nebula. The red glow in IC 1396 and across the image is created by cosmic hydrogen gas recapturing electrons knocked away by energetic starlight. The dark dust clouds are dense groups of smoke-like particles common in the disks of spiral galaxies. Among the intriguing dark shapes within IC 1396, the winding Elephant’s Trunk nebula lies just right of the nebula’s center. IC 1396 lies in the high and far off constellation of Cepheus.
[http://apod.nasa.gov/apod/ap090819.html]
The Elephant’s Trunk in IC 1396
Like an illustration in a galactic Just So Story, the Elephant’s Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Of course, this cosmic elephant’s trunk is over 20 light-years long. The false-color view was recorded through narrow band filters that transmit the light from hydrogen (in green), sulfur (in red), and oxygen (in blue) atoms in the region. The resulting composite highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within the obscuring cosmic dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning about 5 degrees. This dramatic close-up covers a 1/2 degree wide field, about the size of the Full Moon.
[http://apod.nasa.gov/apod/ap071018.html]
NGC 7380 (also known as the Wizard Nebula) is an open cluster discovered by Caroline Herschel. William Herschel included his sister’s discovery in his catalog, and labelled it H VIII.77. It is also known as 142 in the 1959 Sharpless catalog (Sh2-142). This reasonably large nebula is located in Cepheus. It is extremely difficult to observe visually, usually requiring very dark skies and an O-III filter:
[https://en.wikipedia.org/wiki/NGC_7380]
The Wizard Nebula
This image of the open star cluster NGC 7380, also known as the Wizard Nebula, is a mosaic of images from the WISE mission spanning an area on the sky of about 5 times the size of the full moon. NGC 7380 is located in the constellation Cepheus about 7,000 light-years from Earth within the Milky Way Galaxy. The star cluster is embedded in a nebula, which spans some 110 light-years. The stars of NGC 7380 have emerged from this star-forming region in the last 5 million years or so, making it a relatively young cluster.
WISE, the Wide-field Infrared Survey Explorer mission, scans the entire sky in infrared light, picking up the glow of hundreds of millions of objects and producing millions of images. The mission is designed to uncover objects never seen before, including the coolest stars, the universe's most luminous galaxies and some of the darkest near-Earth asteroids and comets. Its vast catalogs will help answer fundamental questions about the origins of planets, stars and galaxies.
WISE joins two other infrared missions in space - NASA’s Spitzer Space Telescope and the Herschel Space Observatory, a European Space Agency mission. WISE is different from these missions in that it will survey the entire sky. It is designed to cast a wide net to catch all sorts of unseen cosmic treasures, including rare oddities. All four infrared detectors aboard WISE were used to make this image.
NGC 7380 was discovered by Caroline Herschel in 1787. Her brother, William Herschel, discovered infrared light in 1800.
[https://www.nasa.gov/multimedia/imagegallery/image_feature_1615.html]
NGC 7538
[SII] = Red, Hα = Green, [OIII] = Blue
Map showing location of NGC 7538
NGC 7538, near the more famous Bubble Nebula, is located in the constellation Cepheus. It is located about 9,100 light-years from Earth. It is home to the biggest yet discovered protostar which is about 300 times the size of the Solar System. It is located in the Perseus Spiral Arm of the Milky Way and is probably part of the Cassiopeia OB2 complex. It is a region of active star formation including several luminous near-IR and far-IR sources.
[https://en.wikipedia.org/wiki/NGC_7538]
S 155, also known as the Cave Nebula, Sh2-155 or Caldwell 9, is a dim and very diffuse bright nebula in the constellation Cepheus within a larger nebula complex containing emission, reflection, and dark nebulosity.
Visually it is a difficult object, but with adequate exposure, makes a striking image. The nebula gets its name Cave Nebula from the dark lane at the eastern side abutting the brightest curve of emission nebulosity which gives the appearance of a deep cave when seen through a telescope visually:
[https://en.wikipedia.org/wiki/S_155]
Sh2-155: The Cave Nebula
This colorful skyscape features the dusty Sharpless catalog emission region Sh2-155, the Cave Nebula. In the composite image, data taken through narrowband filters tracks the glow of ionized sulfur, hydrogen, and oxygen atoms in red, green, and blue hues. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young stars of the Cepheus OB 3 association. The bright rim of ionized interstellar gas is energized by radiation from the hot stars, dominated by the bright star just above picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.
[http://apod.nasa.gov/apod/ap141106.html]
The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158. It shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, and near the bright magnitude +3.23 variable star Beta Cephei (Alphirk):
[https://en.wikipedia.org/wiki/Iris_Nebula]
NGC 7023: The Iris Nebula
These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula, NGC 7023 is not the only nebula in the sky to evoke the imagery of flowers, though. Still, this deep telescopic view shows off the Iris Nebula’s range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the dusty clouds glow with a faint reddish photoluminesence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. The pretty blue petals of the Iris Nebula span about six light-years.
[http://apod.nasa.gov/apod/ap140802.html]
NGC 7129 is a reflection nebula in the constellation Cepheus. A young open cluster is responsible for illuminating the surrounding nebula. A recent survey indicates the cluster contains more than 130 stars less than 1 million years old. NGC 7129 is located just half a degree from nearby cluster NGC 7142:
[https://en.wikipedia.org/wiki/NGC_7129]
NGC 7129 and NGC 7142
This alluring telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (left) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, the pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical studies of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars. Surprisingly, despite the dust, far off background galaxies can be seen in the colorful cosmic vista.
[http://apod.nasa.gov/apod/ap070913.html]
NGC 188
NGC 188 is an open cluster in the constellation Cepheus. It was discovered by John Herschel in 1825. Unlike most open clusters that drift apart after a few million years because of the gravitational interaction of our Milky Way galaxy, NGC 188 lies far above the plane of the galaxy and is one of the most ancient of open clusters known, at approximately 6.8 billion years old. NGC 188 is very close to the North Celestial Pole, under five degrees away, and in the constellation of Cepheus at an estimated 5,000 light year distance, this puts it slightly above the Milky Way’s disc and further from the center of the galaxy than the Sun.
[https://en.wikipedia.org/wiki/NGC_188]
The Fireworks Galaxy (NGC 6946) is a spiral galaxy in which nine supernovae have been observed, more than in any other galaxy:
Facing NGC 6946
From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. From the core outward, the galaxy’s colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century at least nine supernovae, the death explosions of massive stars, were discovered in NGC 6946. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy. This remarkable portrait of NGC 6946 is a composite that includes image data from the 8.2 meter Subaru Telescope on Mauna Kea.
[http://apod.nasa.gov/apod/ap120109.html]
NGC 2276 (left) and NGC 2300 (right)
NGC 2276 is a spiral galaxy in the constellation Cepheus. It is at a distance of about 105 million light-years away from Earth. The galaxy has asymmetrical appearance, probably due to its interaction with the elliptical galaxy NGC 2300. In the spiral arms of NGC 2276 has been discovered an intermediate mass black hole, 50,000 more massive than the Sun, named NGC 2276-3c. The hole has produced a radio-jet, 2,000 light years long. In the galaxy have been also found another seven ultraluminous X-ray sources, and five supernovae in the last 50 years. The galaxy shows high rate of star formation that may have been triggered by a collision with a dwarf galaxy:
NGC 2276: NASA’s Chandra Finds Intriguing Member of Black Hole Family Tree
An intriguing object has been found in one of the spiral arms of the galaxy NGC 2276. This source, called NGC 2276-3c, appears to be an intermediate-mass black hole. According to X-ray and radio data, NGC 2276-3c contains about 50,000 times the mass of the Sun.
A newly discovered object in the galaxy NGC 2276 may prove to be an important black hole that helps fill in the evolutionary story of these exotic objects, as described in our latest press release. The main image in this graphic contains a composite image of NGC 2766 that includes X-rays from NASA’s Chandra X-ray Observatory (pink) combined with optical data from the Hubble Space Telescope and the Digitized Sky Survey (red, green and blue). The inset is a zoom into the interesting source that lies in one of the galaxy's spiral arms. This object, called NGC 2276-3c, is seen in radio waves (red) in observations from the European Very Long Baseline Interferometry Network, or EVN.
Astronomers have combined the X-ray and radio data to determine that NGC 2766-3c is likely an intermediate-mass black hole (IMBH). As the name suggests, IMBHs are black holes that are larger than stellar-mass black holes that contain about five to thirty times the mass of the Sun, but smaller than supermassive black holes that are millions or even billions of solar masses. The researchers estimated the mass of NGC 2766-3c using a well-known relationship between how bright the source is in radio and X-rays, and the mass of the black hole. The X-ray and radio brightness were based on observations with Chandra and the EVN. They found that NGC 2276-3c contains about 50,000 times the mass of the Sun.
IMBHs are interesting to astronomers because they may be the seeds that eventually evolve into supermassive black holes. They also may be strongly influencing their environment. This latest result on NGC 2276-3c suggests that it may be suppressing the formation of new stars around it. The EVN radio data reveal an inner jet that extends about 6 light years from NGC 2276-3c. Additional observations by the NSF’s Karl Jansky Very Large Array (VLA) show large-scale radio emission extending out to over 2,000 light years away from the source.
A region along the jet extending to about 1,000 light years away from NGC 2766-3c is devoid of young stars. This might provide evidence that the jet has cleared out a cavity in the gas, preventing new stars from forming there. The VLA data also reveal a large population of stars at the edge of the radio emission from the jet. This enhanced star formation could take place either when the material swept out by the jet collides with dust and gas in between the stars in NGC 2276, or when triggered by the merger of NGC 2276 with a dwarf galaxy.
In a separate study, Chandra observations of this galaxy have also been used to examine its rich population of ultra-luminous X-ray sources (ULXs). Sixteen X-ray sources are found in the deep Chandra dataset seen in this composite image, and eight of these are ULXs including NGC 2276-3c. Chandra observations show that one apparent ULX observed by ESA’s XMM-Newton is actually five separate ULXs, including NGC 2276-3c. This ULX study shows that about five to fifteen solar masses worth of stars are forming each year in NGC 2276. This high rate of star formation may have been triggered by a collision with a dwarf galaxy, supporting the merger idea for the IMBH’s origin.
Distance Estimate: About 100 million light years.
[http://chandra.harvard.edu/photo/2015/ngc2276/index.html]
[https://www.reddit.com/r/science/comments/2x58e4/black_hole_breaks_records_swallows_up_scientific/?limit=500]
Artist’s impression of a hyperluminous quasar similar to S5 0014+81 surrounded by a thick accretion disc with two powerful jets.
S5 0014+81 is a distant, compact, hyperluminous, broad-absorption line quasar or blazar located near the high declination region of the constellation Cepheus, near the North Equatorial Pole.
The object is a blazar, in fact an FSRQ quasar, the most energetic subclass of objects known as active galactic nuclei, produced by the rapid accretion of matter by a central supermassive black hole, changing the gravitational energy to light energy that can be visible in cosmic distances. In the case of S5 0014+81 it is one of the most luminous quasars known, powering up light equivalent to over 1041 watts, equal to an absolute bolometric magnitude of -31.5. If the quasar were at a distance of 280 light-years from earth it would give as much energy per square meter as the Sun despite being 18 million times more distant. The quasar’s luminosity is therefore about 300 trillion times the Sun, or over 25 thousand times as luminous as all the 100 to 400 billion stars of the Milky Way Galaxy combined, making it one of the most powerful objects in the universe. However, because of its huge distance of 12.1 billion light-years it can only be studied by spectroscopy. The host galaxy of S5 0014+81 is a giant elliptical starburst galaxy, with the apparent magnitude of 24.
The central black hole of the quasar devours an extremely huge amount of matter, equivalent to 4000 solar masses of material every year. In 2009, a team of astronomers using the Swift Spacecraft used the luminosity output of S5 0014+81 to measure the mass of the central black hole. To their surprise, they found out that the central black hole of S5 0014+81 is actually 10,000 times more massive than the black hole at the center of our galaxy, or equivalent to 40 billion solar masses. This makes it one of the most massive black holes ever discovered, more than six times the value of the black hole of M87, which was thought to be the largest black hole for almost 60 years, and was coined to be an ‘ultra-massive’ black hole. The Schwarzschild radius of this black hole is 118.35 billion kilometers. So, this black hole has an external horizon showing a diameter of 236.7 billion kilometers, 1,600 astronomical units, or 47 times the distance from the Sun to Pluto, and shows a mass equivalent to four Large Magellanic Clouds. What is even more astounding is that the monstrous black hole exists so early in the universe, at only 1.6 billion years after the Big Bang. This suggests that supermassive black holes grow up very quickly.
[https://en.wikipedia.org/wiki/S5_0014%2B81]
[https://en.wikipedia.org/wiki/Cepheus_%28constellation%29]
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