Categories: Deep-Sky Objects

Deep-Sky Objects in Taurus

Image Credit: The Crab Nebula in Taurus by NASA, ESA, J. Hester, and A. Loll

Taurus is the 10th biggest of the 88 recognized constellations, and the 6th biggest of the zodiac constellations, taking up an area of 797.25 square degrees of the northern celestial hemisphere. The brightest star in Taurus is Aldebaran (Alpha Tauri), an orange, LB- type variable giant star that is located about 65 light years away. Aldebaran is also the 13th brightest star in the entire night sky, although its magnitude varies between 0.75 and 0.95 over a period of roughly 400 days.

Taurus can be seen from latitudes of between +90° and -65°, with the constellation visible in the northern hemisphere during the autumn and winter months. It is best seen, however, at about 9 PM Local Time during the month of January when it is highest in the sky, but remains visible in the west during early twilight up to about the middle of March.

The constellation contains many spectacular stars and a number of interesting deep sky objects, the most notable of which are explored in this list.

The Crab Nebula (M1, NGC 1952)

The Crab Nebula, which got its name after a sketch made of it by Lord Rosse in 1844, is the first nebula to be directly associated with a historical supernova event, which in this case occurred in the year 1054. The image of the Crab Nebula shown above is the most detailed series of composite image yet taken, and it clearly shows the remains of the progenitor star as orange filaments that consist primarily of hydrogen.

The eerie blue glow in the nebula’s inner regions is caused by electrons that are whizzing around the embedded neutron star in the middle of the nebula at close to the speed of light, following the paths of convoluted magnetic field lines. The Crab Nebula located about 6,500 light years away currently spans about 11 light years along its major axis, although it is still expanding at the rate of 1,500 km/sec.

The Pleiades (M45, Seven Sisters)

Image Credit: NASA, ESA, AURA, Caltech, Palomar Observatory

The Pleiades has been described as the most beautiful cluster in the sky, and it is not difficult to see why. Nonetheless, and despite the controversy about the average distance to M45, it is one of the closest open clusters to Earth, and has been known to most, if not all of the major cultures throughout history. In fact, the earliest depictions of the Pleiades dates back to the Bronze Age.

Although only seven or so stars in the cluster are visible to the naked eye, M45 consists of around 1,000 or so confirmed member stars (excluding unresolved binary stars and brown dwarfs) that all formed from the same source material about 100 million years ago. The blue glow around some stars shown in the image above is the result of the cluster moving through an unrelated cloud of carbon-rich material. Although all stars in M45 now share a common proper motion, it is expected that a gravitational tugs-of-war with surrounding clusters and structures will cause the Pleiades Cluster to be completely dispersed in about 250 million years’ time.

The Hyades Cluster (Caldwell 41, Melotte 25, Collinder 50)

Image Credit: Jerry Lodriguss/AstroPix.com

Like the Pleiades, the Hyades Cluster consists of several hundred stars that all formed from the same material at about the same time, which in the case of the Hyades, happened about 625 million years ago. Located only about 150 or so light years away, the Hyades is the closest open cluster to us, and therefore it is the most intensely studied cluster, by both amateur and professional astronomers.

Although the star Aldebaran is often counted as a member of the Hyades, it is in fact a foreground star that merely lies along the same line of sight toward the core of the cluster, which spans an area of about 17.5 light years. The four most luminous stars in the constellation, Taurus, Gamma, Delta, Epsilon, and Theta Tauri, are all red giants within a few light years of each other and collectively form the “V” asterism that delineates the Bull’s “face”. Also like the Pleiades, all the member stars of the cluster share a common proper motion. Interestingly, in England, the Hyades is also known as the “April Rainers”.

Hind’s Variable Nebula (NGC 1555)

Discovered by John Russell Hind on October 11, 1852, this 4 light-years wide reflection nebula is situated towards the edge of the Taurus Molecular Cloud, some 400 light-years from Earth. Being a reflection nebulae, NGC 1555 shows significant variations in brightness caused by changes in the luminosity of the stars it reflects, which in this case is the famous variable star T Tauri.

It is worth noting that T Tauri is the prototype of the T Tauri class of variable stars, which are young stars less than a few million years old in their early stages of formation.

NGC 1410 and NGC 1409

Image Credit: NASA, William C. Keel

Although many images of colliding galaxies exist, this example offers the clearest view of the process of galaxies tidally stripping gas, dust, and stars from each other. In this example, the dark dust lane that starts in NGC 1410 (the galaxy at lower left), and extends partway around NGC 1409 (the bigger galaxy to the right) is a 20,000 light-year long intergalactic “pipeline” that funnels material from one galaxy to the other.

In this case, the transfer of material is causing a high rate of star formation in NGC 1410 (the receiving galaxy) as can be seen by the large blue areas, in which young, hot blue stars abound. Note that NGC 1409 (the galaxy being stripped), consists primarily of old, red and yellow stars. This particular galactic collision is estimated to have begun about 100 million or so ago, and will eventually bring about a single, large elliptical galaxy.

Crystal Ball Nebula (NGC 1514)

Image Credit: Tom Wildoner

Discovered by William Herschel in November of 1790, NGC 1514 is a large, magnitude 9.43 planetary nebula located about 2,200 light years away, and is thought to surround a close binary star system with an orbital period of about 10 days. Up to this time, Herschel was of the opinion that all nebulae were merely exceedingly distant masses of unresolved stars, but this discovery forced him to rethink his ideas about the nature of nebulae in general, and of this particular example, especially.

In his notes Herschel described NGC 1514 as “A most singular phaenomenon”, and added that, “Our judgement I may venture to say, will be, that the nebulosity about the star is not of a starry nature”.

Merope Nebula (NGC 1435, Tempel’s Nebula)

Image Credit: Hap Griffin

Discovered by Wilhelm Tempel in 1895, this reflection nebula in the Pleiades Cluster is completely illuminated by the 4th magnitude star Merope (23 Tauri). Thought to be a supernova remnant, the nebula has an apparent visual magnitude of 13 in its central regions, but quickly drops of by a factor of at least 15 towards the outer regions, which gives the entire nebula an average magnitude of about 16. The Merope Nebula is located about 440 light years away.

The Merope Nebula also contains a distinctly separate knot of luminosity known as Barnard’s Merope Nebula (IC 349), that is located about 0.6 light year away from the star Merope, and is also illuminated by it. Note, though, that although IC 349 is naturally very bright, it is largely overshadowed by the larger Merope Nebula, which can make it an extremely challenging object to spot in small to medium telescopes.

Peter Christoforou :