Space and astronomy news
Thanks to the Hubble Space Telescope, we all have a vivid image of the Crab Nebula emblazoned in our mind’s eyes. It’s the remnant of a supernova explosion Chinese astronomers recorded in 1056. However, the Crab Nebula is more than just a nebula; it’s also a pulsar.
The Crab Pulsar pulsates in an unusual ‘zebra’ pattern, and an astrophysicist at the University of Kansas thinks he’s figured out why.
Continue reading “The Strange Pulsar at the Center of the Crab Nebula”
The Crab Nebula has always fascinated me, albeit amazed me that it doesn’t look anything like a crab! It’s the result of a star that exploded at the end of its life back in 1054 CE, leaving behind what is known as a supernova remnant. Back then the explosion would have been visible to the naked eye, even in daytime. It was thought that the supernova that led to the cloud was from a less evolved star with a core made from oxygen, neon and magnesium. Recent studies by the James Webb Space Telescope reveals that it may actually be the core collapse of an iron rich star.
Continue reading “Something’s Always Been Off About the Crab Nebula. Webb Has Revealed Why!”
Located about 6,500 light-years away in the constellation Taurus resides one of the best-studied cosmological objects known as the Crab Nebula (aka. Messier 1). Originally discovered in the 18th century by English astronomer John Bevis in 1731, the Crab Nebula became the first object included by astronomer Charles Messier in his catalog of Deep Sky Objects. Because of its extreme nature, scientists have been studying the Crab Nebula for decades to learn more about its magnetic field, its high-energy emissions (x-rays), and how these accelerate particles to close to the speed of light.
Astronomers have been particularly interested in studying the polarization of the x-rays produced by the pulsar and what that can tell us about the nebula’s magnetic field. When studies were first conducted in the 1970s, astronomers had to rely on a sounding rocket to get above Earth’s atmosphere and measure the polarization using special sensors. Recently, an international team of astronomers used data obtained by NASA’s Imaging X-ray Polarimetry Explorer (IXPE) to create a detailed map of the Crab Nebula’s magnetic field that has resolved many long-standing mysteries about the object.
Continue reading “The Crab Nebula Looks Completely Different in X-Rays, Revealing its Magnetic Fields”
Neutron stars are dense remnants of large stars. They are the collapsed cores of stars formed during a supernova explosion. While we know generally how they form, we are still learning how they evolve, particularly when they are young. But that’s starting to change thanks to large sky surveys, which have allowed astronomers to observe a neutron star that could be little more than a decade old.
Continue reading “Astronomers Find a Brand new Pulsar That's Probably Less Than 14 Years old”
The Crab Nebula is arguably one of the most famous objects in the night sky. It was delineated as M1 in Messier’s famous catalogue. It is the remnants of a supernova that was actually visible in day time almost 1000 years ago. And its remnants have been astonishing both professional and amateur astronomers ever since.
Now thanks to modern technology, we can get an updated view of this iconic supernova remnant. Researchers from a variety of institutions, led by Thomas Martin from the Universite Laval, have created a three dimensional image of the nebula for the first time ever.
Continue reading “The Crab Nebula Seen in 3-Dimensions”
Most people with any interest in astronomy know about the Crab Nebula. It’s a supernova remnant in the constellation Taurus, and its image is all over the place. Google “Hubble images” and it’s right there with other crowd favorites, like the Pillars of Creation.
The Crab Nebula is one of the most-studied objects in astronomy. It’s the brightest source of gamma rays in the sky, and that fact is being used to establish the function of a new telescope called the Schwarschild-Couder Telescope.
Continue reading “Gamma Rays Detected Coming From the Crab Nebula”
Images of the Crab Nebula are always a treat because it has such intriguing and varied structure. Also, just knowing that this stellar explosion was witnessed and recorded by people on Earth more than 900 years ago (with the supernova visible to the naked eye for about two years) gives this nebula added fascination.
A new image just might be the biggest Crab Nebula treat ever, as five different observatories combined forces to create an incredibly detailed view, with stunning details of the nebula’s interior region.
Data from the five telescopes span nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope’s crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope.
The Crab is 6,500 light-years from Earth and spans about 10 light-years in diameter. The supernova that created it was first witnessed in 1054 A. D. At its center is a super-dense neutron star that is as massive as the Sun but with only the size of a small town. This pulsar rotates every 33 milliseconds, shooting out spinning lighthouse-like beams of radio waves and light. The pulsar can be seen as the bright dot at the center of the image.
Scientists say the nebula’s intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion.
For this new image, the VLA, Hubble, and Chandra observations all were made at nearly the same time in November of 2012. A team of scientists led by Gloria Dubner of the Institute of Astronomy and Physics (IAFE), the National Council of Scientific Research (CONICET), and the University of Buenos Aires in Argentina then made a thorough analysis of the newly revealed details in a quest to gain new insights into the complex physics of the object. They are reporting their findings in the Astrophysical Journal (see the pre-print here).
About the central region, the team writes, “The new HST NIR [near infrared] image of the central region shows the well-known elliptical torus around the pulsar, composed of a series of concentric narrow features of variable intensity and width… The comparison of the radio and the X-ray emission distributions in the central region suggests the existence of a double-jet system from the pulsar, one detected in X-rays and the other in radio. None of them starts at the pulsar itself but in its environs.”
“Comparing these new images, made at different wavelengths, is providing us with a wealth of new detail about the Crab Nebula. Though the Crab has been studied extensively for years, we still have much to learn about it,” Dubner said.
Read the team’s paper: Morphological properties of the Crab Nebula: a detailed multiwavelength study based on new VLA, HST, Chandra and XMM-Newton images
Sources: Chandra, Hubble
In the 18th century, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects in the night sky. Initially, he thought these were comets, which he was attempting to locate at the time. However, astronomers would later discover that these objects were in fact nebulae, galaxies and star clusters. Between the years of 1758 and 1782, Messier compiled a list of approximately 100 of these objects.
His intention was to ensure that other astronomers would not mistake these objects for comets. But in time, this list – known as the Messier Catalog – served a higher purpose. In addition to being a collection of some of the most beautiful objects in the night sky, the catalog was also an important milestone in the discovery and research of Deep Sky objects. The first item in the catalog is the famous Crab Nebula – hence its designation as Messier Object 1, or M1.
Messier 1 (aka. M1, NGC 1952, Sharpless 244, and the Crab Nebula) is a supernova remnant located in the Perseus Arm of the Milky Way Galaxy, roughly 6500 ± 1600 light years from Earth. Like all supernova remnants, it is an expanding cloud of gas that was created during the explosion of a star. This material is spread over a volume approximately 13 ± 3 ly in diameter, and is still expanding at a velocity of about 1,500 km/s (930 mi/s).
Based on its current rate of expansion, it is assumed that the overall deceleration of the nebula’s expansion must has decreased since the initial supernova. Essentially, after the explosion occurred, the nebula’s pulsar would have began to emit radiation that fed the nebula’s magnetic field, thus expanding it and forcing it outward.
In visible light, the Crab Nebula consists of an oval-shaped mass of filaments – whose spectral emission lines are split into both red and blue-shifted components – which surround a blue central region. The filament are leftover from the outer layers of the former star’s atmosphere, and consist primarily of hydrogen and helium, along with traces of carbon, oxygen, nitrogen and heavier elements. The filaments’ temperatures are typically between 11,000 and 18,000 K.
The blue region, meanwhile, is the result of highly polarized synchrotron radiation, which is emitted by high-energy electrons in a strong magnetic field. The curved path of these electrons is due to the strong magnetic field produced by the neutron star at the center of the nebula (see below). One of the many components of the Crab Nebula is a helium-rich torus which is visible as an east-west band crossing the pulsar region.
The torus accounts for about 25% of the nebula’s visible ejecta and is believed to be made up of 95% helium. As yet, there has been no plausible explanation for the structure of the torus. And while it is very difficult to gauge the total mass of the nebula, official estimates place it at 4.6 ± 1.8 Solar masses – i.e 5.5664 to 12.7232 × 1030 kg.
At the center of the Crab Nebula are two faint stars, one of which is its progenitor (i.e the one that created it). It is because of this star that M1 is a strong source of radio waves, X-rays and Gamma-ray radiation. The remnant of supernova SN 1054, which was widely observed on Earth in the year 1054, this star was discovered in 1968 and has since been designated as a radio pulsar.
Known as the Crab Pulsar (or NP0532), this rapidly rotating star is believed to be about 28–30 km (17–19 mi) in diameter and emits pulses of radiation – ranging from radio wave and X-ray – every 33 milliseconds. Like all isolated pulsars, its period is slowing very gradually, and the energy released as the pulsar slows down is enormous. The Crab Pulsar is also the source of the nebula’s synchrotron radiation, which has a total luminosity about 75,000 times greater than that of the Sun.
The pulsar’s extreme energy output also creates an unusually dynamic region at the center of the Crab Nebula. While most astronomical objects only show changes over timescales of many years, the inner parts of the Crab show changes over the course of only a few days. The most dynamic feature in the inner part of the nebula is the point where the pulsar’s equatorial wind slams into the bulk of the nebula, forming a shock front (see above image).
The Crab Pulsar is also surrounded by an expanding gas shell which encompasses its spectroscopic companion star, which in turn orbits the neutron star every 133 days. This pulsar was the first one which was also verified in the optical part of the spectrum.
The very first recorded information on this supernova event reaches as far back as July 4, 1054 A.D. by Chinese astronomers who marked the presence of a “new star” visible in daylight for 23 days and 653 nights. The event may have also been recorded by the Anasazi, Navajo and Mimbres First Nations of North America in their artwork as well.
In more modern times, the nebula was cataloged as a discovery by British amateur astronomer John Bevis in 1731, and independently by Charles Messier on August 28th, 1758 while looking for the return of Comet Halley. Although Bevis had added it to his “Uranographia Britannica”, Messier recognized what he had located had no proper motion, and was therefore not a comet. However, Messier did credit Bevis’ discovery when he learned of it years later.
By September 12th, 1758, Messier hit upon the idea of compiling a catalog of objects that weren’t comets, in order to help other astronomers avoid similar mistakes. Considering M1’s position, only slightly more than a degree from the ecliptic plane, this was a very good idea. Especially since M1 was again confused with Halley’s Comet when it returned in 1835.
The name Crab Nebula was first suggested by William Parsons, the Third Earl of Rosse, who observed it while at Birr Castle in 1884. The name was apparently due to the drawing he made of it, which resembled a crab. When he observed it again in 1848 using a ]telescope with better resolution, he could not confirm the resemblance. But the name had become popular by this point and has stuck ever since.
All of the early observers – including Herschel, Bode, Messier and Lassell – apparently mistook the filamentary structures of the Nebula as an indication of stellar structure. As Messier himself described it:
“Nebula above the southern horn of Taurus, it doesn’t contain any star; it is a whitish light, elongated in the shape of a flame of a candle, discovered while observing the comet of 1758. See the chart of that comet, Mem. Acad. of the year 1759, page 188; observed by Dr. Bevis in about 1731. It is reported on the English Celestial Atlas.”
Sir Williams Herschel’s writing on the nebula appeared in the 74th volume of the Philosophical Transactions of the Royal Society of London, which was released in 1784. As he described it:
“To these may added the 1st [M1], 3d, 27, 33, 57, 79, 81, 82, 101 [of Messier’s catalog], which in my 7, 10, and 20-feet reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed…”
But it was Parsons (aka. Lord Rosse) who first recognized M1 for what we know it as today. As he recorded when viewing it for the first time (in 1844):
“Fig. 81 is also a cluster; we perceive in this [36-inch telescope], however, a considerable change of appearance; it is no longer an oval resolvable [mottled] Nebula; we see resolvable filaments singularly disposed, springing principally from its southern extremity, and not, as is usual in clusters, irregularly in all directions. Probably greater power would bring out other filaments, and it would then assume the ordinary form of a cluster. It is stubbed with stars, mixed however with a nebulosity probably consisting of stars too minute to be recognized. It is an easy object, and I have shown it to many, and all have been at once struck with its remarkable aspect. Everything in the sketch can be seen under moderately favourable circumstances.”
The Crab Nebula is easily visible in the night sky near the Taurus constellation, whenever light pollution is not an issue. It can be located by identifying Zeta Tauri, a third magnitude star located east/northeast of Aldebaran. With dark sky conditions, it can be seen as a tiny, hazy patch with binoculars and small telescopes with low magnification. If sky conditions are bright, it may be harder to locate with modest equipment.
With a little more magnification, it is seen as a nebulous oval patch, surrounded by haze. In telescopes starting with 4-inch aperture, some detail in its shape becomes apparent, with some suggestion of mottled or streak structure in the inner part of the nebula. To the amateur astronomer, M1 does indeed look similar to a faint comet without a tail.
As Messier 1 is situated only 1 1/2 degrees from the ecliptic, there are frequent conjunctions and occasional transits of planets, as well as occultations by the Moon. And for the sake of simplicity, here are the vital statistics on this Messier Object:
Object Name: Messier 1
Alternative Designations: NGC 1952, M1, Sharpless 244, Crab Nebula
Object Type: Supernova Remnant
Constellation: Taurus
Right Ascension: 05 : 34.5 (h:m)
Declination: +22 : 01 (deg:m)
Distance: 6.3 (kly)
Visual Brightness: 8.4 (mag)
Apparent Dimension: 6×4 (arc min)
We wish you luck in locating it in the night sky. And should you find it, enjoy your observations!
We have written many great articles about the Crab Nebula and Messier Objects here at Universe Today. Here’s What Is The Crab Nebula?, The Peculiar Pulsar in the Crab Nebula, and Top Five Celestial Objects Anyone Can See With A Small Telescope.
Be sure to check out our complete Messier Catalog.
For more information, check out the SEDS Messier Database.
Pulsars — those supernova leftovers that are incredibly dense and spin very fast — may change their speed due to activity of billions of vortices in the fluid beneath their surface, a new study says.
The work is based on a combination of research and modelling and looks at the Crab Nebula pulsar, which has periodic slowdowns in its rotation of at least 0.055 nanoseconds. Occasionally, the Crab and other pulsars see their spins speed up in an event called a “glitch”. Luckily for astronomers, there is a wealth of data on Crab because the Jodrell Bank Observatory in the United Kingdom looked at it almost daily for the last 29 years.
A glitch, the astronomers said in a statement, is “caused by the unpinning and displacement of vortices that connect the [pulsar’s] crust with the mixture of particles containing superfluid neutrons beneath the crust.”
“Surprisingly, no one tried to determine a lower limit to glitch size before. Many assumed that the smallest glitch would be caused by a single vortex unpinning. The smallest glitch is clearly much larger than we expected,” stated Danai Antonopoulou from the University of Amsterdam.
The astronomers added they will need more observations of other pulsars to better understand the results.
You can read the paper at the Monthly Notices of the Royal Astronomical Society or in preprint version on Arxiv. The research was led by C.M. Espinoza of the University of Manchester and Chile’s Pontifical Catholic University.
Source: NOVA
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Continue reading “Virtual Star Party – January 26, 2014: Our Missed Supernova!”