GK Persei: Nova of 1901
In 1901, an obscure star in the constellation of Perseus suddenly flared into brightness, becoming briefly one of the brightest stars in the sky. Called GK Persei (or Nova Persei 1901), it’s an odd beast. While some stars like this just fade away after such an event, even now, more than a century later, GK Persei still suffers through periodic explosions, emitting vast pulses of energy.
This type of system is called a cataclysmic variable star. It’s a binary: one of the stars is a white dwarf, an ultra-dense ball of matter that used to be the core of a normal star like the Sun. When that star reached the end of its life, it shed its outer layers, exposing its core to space.
The other star is a swollen red giant, also nearing the end of its life. Material from the red giant falls onto the white dwarf, where it piles up. The surface gravity of the dwarf can be a hundred thousand times that of Earth. This compresses the infalling material so much that when the pile gets big enough it can cause spontaneous nuclear fusion.
The resulting explosion is incredibly violent, and blasts a lot of the material into space. After a while, things settle down, and the matter starts piling up again, repeating the cycle. It’s not the same every time, as the 1901 nova was quite the singular event. So sometimes the star is more violent than others. Recently GK Persei has been acting up again, undergoing brighter flares, though nothing like the 1901 explosion.
You can view an animation showing the nebula expanding over 17 years, from 1994 to 2011 here: http://vimeo.com/31120259
The Tadpoles of IC410
From his home observatory in Connellsville, Pa., avid astrophotographer Bill Snyder took this stunning photo of the so-called “tadpoles” of the emission nebula IC410 on Jan. 15. IC410 is located roughly 12,000 light-years away toward the constellation Auriga.
The tadpoles in this image are actually about 10 light-years long and are potential sites of star formation. The nebula itself surrounds the young cluster of stars called NGC 1893. This cluster energizes the denser, cooler gas making up the tadpoles. Their unique shape is sculpted by wind and radiation from the cluster stars.
Snyder used a TMB130mm telescope equipped with an Apogee U8300 camera, as well as a mount and several filters to create this view of IC410. He had a total exposure time of more than 14 hours to capture this view of the nebula.
NASA’s SOFIA captures image of dying, outflowing star
Researchers using NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) have captured an infrared image of the last exhalations of a dying sun-like star. The planetary nebula Minkowski 2-9 (M2-9) is seen in this three-color composite image.
Although the M2-9 nebular material is flowing out from a spherical star, it is extended in one dimension, appearing as a cylinder or hourglass. Planetary nebulae with such shapes are produced by opposing flows of high-speed material caused by a disk of material around the dying star, located at the center of the nebula.
SOFIA’s observations of M2-9 were designed to study the outflow in detail with the goal of better understanding this stellar life cycle stage, which is important in our galaxy’s evolution. The observations were made at the 37-micron wavelength band which detects the strongest emissions from the nebula and is impossible to observe from ground-based telescopes.
The SOFIA observatory combines an extensively modified Boeing 747SP aircraft and a 17-metric-ton reflecting telescope with an effective diameter of 100 inches (2.5 meters) to altitudes as high as 45,000 feet (14 kilometers). This places the telescope above more than 99 percent of the water vapor in Earth’s atmosphere that blocks most infrared radiation from celestial sources.
NGC 2264 Cone and Foxfur Nebulae
Astrophotography duo Bob and Janice Fera took this photo in January 2012 from Eagle Ridge Observatory in Foresthill, Calif.
The two nebulas in the photo are called the Cone and Foxfur nebulas. They are part of a larger star-forming region called NGC 2264, which is located in the Monoceros constellation about 2,600 light-years away from Earth.
The Cone Nebula’s unusual shape comes from an intervening dark cloud near the swirl of hydrogen gas and dust. The Foxfur Nebula is so named because it resembles a woman’s luxurious stole.
M42- The Orion Nebula
The Great Orion Nebula, also known as M42 or NGC 1976, located near the middle of the “sword” hanging from Orion’s “belt” of stars. It is about 1,000 light-years distant and as many as 60 light-years in diameter. The nebula is an enormous cloud of gas surrounding a cluster of very hot young stars.
To the naked eye the nebula appears to be a faint star but becomes a vague patch of light when viewed through binoculars. The bright region is divided into two sections, the northeast portion being cataloged separately as M43 or NGC 1982. The Orion Nebula is the nearest major site to earth of massive star formation.
Cygnus Loop Nebula
Wispy tendrils of hot dust and gas glow brightly in this ultraviolet image of the Cygnus Loop nebula, taken by NASA’s Galaxy Evolution Explorer. The nebula lies about 1,500 light-years away, and is a supernova remnant, left over from a massive stellar explosion that occurred between 5,000 to 8,000 years ago.
The Cygnus Loop extends over three times the size of the full moon in the night sky, and is tucked next to one of the “swan’s wings” in the constellation of Cygnus. The filaments of gas and dust visible here in ultraviolet light were heated by the shockwave from the supernova, which is still spreading outward from the original explosion.
The original supernova would have been bright enough to be seen clearly from Earth with the naked eye.
The image shows the Jellyfish Nebula or IC443 to the right, and IC444 to the the left. The first is a planetary nebula which shelters a neutron star, the product of a star that exploded about 30,000 years ago and left a very large remnant; it is located about 5,000 light years away. In the picture the nebulae are flanked by the stars Mu and Etas in the constellation Gemini.
The Christmas Tree and Cone Nebulae
The open cluster of stars associated with these nebulae was discovered by William Herschel in 1785 and is cataloged as NGC 2264 and lies at a distance of 2,600 light years from our solar system. It is an H II region located in the constellation Monoceros, a region with much stardust. The picture also shows the Hubble Variable Nebula as the little flash at the top right.
Abell 33: an enigmatic blue bubble in space
Planetary nebulae are the eerie and beautiful structures created when dying stars cast off their outer layers. They come in many strange shapes, and oddly it’s quite rare to find one that appears perfectly circular such as Abell 33, located something like 1500 light years away.
The central star may be a binary, two stars orbiting each other no closer than about 0.03 light years from each other — about 2000 times the distance of the Earth from the Sun. The central star(s) is off-center, which usually happen if the star is moving rapidly through space. The wind it expels gets “blown back” by gas in between the stars.
The outer rim is nearly a perfect circle, which is really uncommon for planetary nebulae. Most are oval, or barrel-shaped, or something even weirder. It has to do with the way the dying star blows off winds, streams of subatomic particles from its surface.
While rim is circular, the fog on the inside is not. It has two oval holes in it, slightly off center. Moreover, the two ovals are parallel, slanted a bit at the same angle. This may be a sign that the nebula itself may be more barrel shaped, and the two dark ovals are the open ends of the barrel structure.
The bright star on the edge of it giving it a diamond-ring look is almost certainly just a chance alignment. It’s probably much closer or farther away than the nebula, and coincidentally lined up.
The M81 Galaxy Group Through the Integrated Flux Nebula
Large galaxies and faint nebulae highlight this deep image of the M81 Group of galaxies. First and foremost in the wide-angle 12-hour exposure is the grand design spiral galaxy M81, the largest galaxy visible in the image.
M81 is gravitationally interacting with M82 just below it, a big galaxy with an unusual halo of filamentary red-glowing gas. Around the image many other galaxies from the M81 Group of galaxies can be seen, as well as a lucky satellite glint streaking across the image left.
Together with other galaxy congregates including our Local Group of galaxies and the Virgo Cluster of galaxies, the M81 Group is part of the expansive Virgo Supercluster of Galaxies. This whole galaxy menagerie is seen through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy.
Stellar Voyage of a Butterfly-like Planetary Nebula
The breathtaking butterfly-like planetary nebula NGC 6881 is visible here in an image taken by the Hubble Space Telescope. Located in the constellation of Cygnus, it is formed of an inner nebula, estimated to be about one fifth of a light-year across, and symmetrical “wings” that spread out about one light-year from one tip to the other.
NGC 6881 has a dying star at its core which is about 60% of the mass of the Sun. It is an example of a quadrupolar planetary nebula, made from two pairs of bipolar lobes pointing in different directions, and consisting of four pairs of flat rings. There are also three rings in the centre.
A planetary nebula is a cloud of ionised gas that typically forms when a dying star — a red giant — throws off its outer layers, because of pulsations and strong stellar winds. The star’s exposed hot, luminous core starts emitting ultraviolet radiation, exciting the outer layers of the star. At some point, the nebula is bound to dissolve in space, leaving the central star as a white dwarf.
Planetary nebulae usually live for a few tens of thousands of years, a short phase in the lifetime of a star. The image was taken through three filters which isolate the specific wavelength of light emitted by nitrogen (shown in red), hydrogen (shown in green) and oxygen (shown in blue).
NGC 1579: Trifid of the North
Colorful NGC 1579 resembles the better known Trifid Nebula, but lies much farther north in planet Earth’s sky, in the heroic constellation Perseus.
About 2,100 light-years away and 3 light-years across, NGC 1579 is, like the Trifid, a study in contrasting blue and red colors, with dark dust lanes prominent in the nebula’s central regions. In both, dust reflects starlight to produce beautiful blue reflection nebulae.
But unlike the Trifid, in NGC 1579 the reddish glow is not emission from clouds of glowing hydrogen gas excited by ultraviolet light from a nearby hot star. Instead, the dust in NGC 1579 drastically diminishes, reddens, and scatters the light from an embedded, extremely young, massive star, itself a strong emitter of the characteristic red hydrogen alpha light.
The Seagull Nebula
A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula. This portrait of the cosmic bird covers a 1.6 degree wide swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major.
Of course, the region includes objects with other catalog designations: notably NGC 2327, a compact, dusty emission region with an embedded massive star that forms the bird’s head (aka the Parrot Nebula, above center). IC 2177 forms the sweeping arc of the seagull’s wings.
Dominated by the reddish glow of atomic hydrogen, the complex of gas and dust clouds with bright young stars spans over 100 light-years at an estimated 3,800 light-year distance.
Hubble Views Grand Star-Forming Region
This massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud. There is no known star-forming region in the Milky Way Galaxy as large or as prolific as 30 Doradus.
Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are 100 times more massive than our sun. These hefty stars are destined to pop off, like a string of firecrackers, as supernovas in a few million years.
The brilliant stars are carving deep cavities in the surrounding material by unleashing a torrent of ultraviolet light, and hurricane-force stellar winds (streams of charged particles), which are etching away the enveloping hydrogen gas cloud in which the stars were born.
The image, taken in ultraviolet, visible and red light by Hubble’s Wide Field Camera 3, spans about 100 light-years. These observations were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; the red from fluorescing hydrogen.