Phil Harrington's Cosmic Challenge Archives

Cosmic Challenge: M13's propeller

In last month's column, we paid a visit to the Moon and the crater pair of Messier and Messier A. This month, we head back out into deep space to examine one of the most spectacular entries in Charles Messier's catalog: M13, the Great Hercules Globular Cluster.

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Cosmic Challenge: Rupes Recta (Straight Wall), Huygen's Sword, Birt, and Rima Birt

What is your favorite lunar feature? Maybe it's the mighty craters Copernicus or Tycho. Or could it be the historic Sea of Tranquility? Perhaps you enjoy visiting the rugged southern highlands around Clavius, or the Apennine and Alp Mountains. If I had to come up with my favorite target, it would have to be a far more modest sight. I always enjoy looking for and at the Straight Wall.

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Cosmic Challenge: Stephan's Quintet

The canvas on which our picture of the universe is painted relies on the unwavering acceptance of Hubble's Law. Hubble's Law states that a relationship exists between the distance to a galaxy and the speed at which it is receding from us. The farther away a galaxy is, the greater the speed of its recession and farther its spectral lines are shifted toward the red end of the spectrum. For Hubble's Law and the Red Shift Principal to be valid, it must work for not just a few galaxies, but for all. And indeed, it does -- well almost.

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Cosmic Challenge: Barnard's Loop

One of the greatest naked-eye challenges goading amateur astronomers around the world is trying to spot the elusive arc of nebulosity known as Barnard's Loop. Cataloged officially as Sharpless 2-276, Barnard's Loop is a ghostly, 10°-wide semicircular bow of nebulosity that wraps around the eastern side of Orion, the Hunter. In long exposure photographs, it bears the unmistakable resemblance to portions of the Veil Nebula supernova remnant in Cygnus. Spotting it by eye stands as a monumental test for observers.

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Cosmic Challenge: Satellites of Uranus

Of the 27 known satellites in the Uranian family, four stand out, just as the four Galilean satellites do among the Jovian clan. William Herschel discovered the first two Uranian moons on January 11, 1787, six years after he had discovered the planet itself. The next two remained undetected until the British astronomer William Lassell (1799-1880) spotted them on October 24, 1851. It is these four that we hope to catch through our own telescopes.

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Cosmic Challenge: NGC 2438

M46 in Puppis is one of my favorite open clusters and a striking sight through just about any telescope. More than 500 stars are crammed into an area just a Moon's diameter across, creating one of the most jam-packed throngs in the winter sky.

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Cosmic Challenge: Lunar Craters Messier and Messier A

Summer is in the offing here in the Northern Hemisphere and the longest day of the year is at hand. While many of us enjoy the warmer weather, the dark of night comes late in the evening and leaves all too early the following morning. So while deep-sky observing is limited, we can still enjoy viewing our Moon even if the sky is still bright. Yes, observing challenges await us on our nearest neighbor in space.

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Cosmic Challenge: Ring Nebula Central Star and Galaxy IC 1296

As we say goodbye to summer and get ready to welcome in autumn, I thought I would offer not one, but two challenges this month to bridge the seasonal change. Both appear right next to each other in our sky but are millions of light years apart. And both require all the aperture you can throw at them to be seen.

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Cosmic Challenge: NGC 6445, The Box Nebula

The sky is full of weird sights. And among planetary nebulae, NGC 6445 is one of the strangest. Discovered by William Herschel on May 28, 1786, NGC 6445 shines at 11th magnitude. That's bright enough to be seen even through giant binoculars. Although visible in smaller apertures, it takes a 6-inch telescope for NGC 6445's true, if bizarre, nature to shine through. The nebula's brighter central shell looks like a dented rectangle. Nature rarely creates an amorphous form with sharp edges, and indeed, the peculiar appearance of NGC 6445 is due largely to our perspective as well as its age. But the look is very odd nonetheless. No wonder NGC 6445 has been nicknamed the Box Nebula.

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Cosmic Challenge: The Eye of Mars

With Mars just having passed opposition on October 13, I thought it might be fun to challenge you to see a specific surface feature on the Red Planet before it slips too far away.

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Cosmic Challenge: Emission Nebula Simeis 57

Simeis 57 is one of the most intriguing emission nebulae in the late summer sky, yet it is almost unknown to visual observers. Photographers, however, know it as a pair of opposing arcs of reddish light, one extending to the north, the other to the south, that appear to be spinning symmetrically away from a common center. Its unusual appearance has led to its two nicknames: the Propeller Nebula or the Garden Sprinkler Nebula.

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Cosmic Challenge: Spotting Uranus

On March 12, 1781, the solar system was a simple, very well-behaved place that was best summed up with the phrase "what you see is what you get." There were the Sun, the Moon, and the five planets: Mercury, Venus, Mars, Jupiter, and Saturn. Apart from a handful of moons orbiting some of the planets and the occasional faint comet that required a telescope to be seen, the entire contents of the solar system was naked-eye territory.

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Cosmic Challenge: Alphabet Soup

The Moon's terminator is a fascinating sight through all telescopes. Here, along the lunar sunset/sunrise line, lighting can strike familiar lunar features in very unusual ways, transforming them in ways that go unsuspected when the Sun rides high overhead.

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Cosmic Challenge 61 Cygni: Piazzi's Flying Star

The star 61 Cygni is not bright, nor is it visually distinctive. To the eye alone, it looks just like any other 5th-magnitude point of light deep in the Milky Way flowing through the Swan. But looks can be deceiving! This unremarkable looking star is indeed quite remarkable for its unusually high rate of proper motion. By watching and plotting it against the backdrop of stars over the course of relatively few years, its position shifts at an extraordinarily fast pace. At present, 61 Cyg has a proper motion of more than 5 arc-seconds per year.

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Cosmic Challenge: Lunar craters Armstrong, Aldrin, and Collins

Last month, I challenged you to find all six of the Apollo landing sites. This month, to commemorate the 50th anniversary of Neil Armstrong's and Edwin Aldrin's historic landing and moon walk, we return to Mare Tranquilitatis, the scene of Apollo 11, to find three small craters that bear the names of that historic mission's crew members.

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Cosmic Challenge: Zeta (ζ) Cancri

Although it is one of the faintest constellations along the zodiac, Cancer the Crab hosts a variety of targets to test our mettle during the early spring. Spotting M44, the Beehive Cluster, by eye alone may prove very challenging for suburban observers, while the Crab's underappreciated second open cluster, M67, may also reach naked-eye visibility from more rural environs. While the constellation boasts a variety of challenging galaxies, in the test here, we will try our luck with one of the constellation's prettiest binary stars, Zeta (ζ) Cancri.

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Cosmic Challenge: Leo I

Seven decades ago, while scanning a Palomar Sky Survey plate of the area around brilliant Regulus in Leo the Lion, astronomers Robert Harrington (no relation) and A.G. Wilson noticed a faint blur of light just 1/2° north of the star. They may have thought at first that the glow was just an internal lens flare caused by stray starlight, but it soon became apparent that they had discovered something very real.

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Cosmic Challenge: NGC 1360

Many stargazers consider Fornax, the Furnace, to be a constellation of the deep south, and therefore, invisible from mid-northern latitudes. While it is true that Fornax scrapes the southern horizon on early winter evenings, it does so at much the same altitude as Scorpius does during the summer. If you can see Scorpius from your observing site in July, you can see Fornax tonight. Assuming it's clear, of course!

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Cosmic Challenge: M51's spiral arms

Of the thousands of spiral galaxies visible through backyard telescopes, one stands above the rest in terms of visual interest: M51, the famous Whirlpool Galaxy in Canes Venatici. Everything adds up in M51's favor. We are seeing it very nearly face-on, its spiral arm halo is bright and peppered with star clouds and vast regions of nebulosity, and it brings with it a friend in the form of a smaller companion galaxy that can even be seen through giant binoculars.

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Cosmic Challenge: NGC 1535

Planetary nebula NGC 1535 is a victim of circumstance. Take a look at its facts. Its bluish disk spans about a minute of arc, which is quite large as planetaries go, and shines brightly enough to be visible through giant binoculars. Its central star glows at magnitude 11.6, creating a surreal scene resembling a disembodied human eye, which led to the nickname "Cleopatra's Eye." Those in the know rate NGC 1535 as one of the sky's finest planetary nebulae. Yet this enticing target remains unknown to many backyard stargazers.

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Cosmic Challenge: Leo Trio 2

You have undoubtedly heard of the Leo Trio, made up of M65, M66, and NGC 3628. But how about the Leo Trio 2? The Leo Trio 2 are tucked snuggly into the constellation's northernmost quadrant, some 7° north of the Leo "sickle."

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Cosmic Challenge: Jonckheere 900

Few amateur astronomers are familiar with the name Robert Jonckheere. Jonckheere was a French double-star observer who conducted research at a number of observatories over his six-decade career, including the Strasbourg Observatory in France, the Royal Greenwich Observatory in England, as well as McDonald Observatory in Texas.

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Cosmic Challenge: Galaxies around M13

If you're like me, you have probably seen Jupiter, Saturn, the Orion Nebula, and all of the sky's showpiece objects more times than you can count. And while they are truly spectacular and well worth revisiting, you may be looking for something new, something challenging to observe.

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Cosmic Challenge: Seyfert's Sextet

Seyfert's Sextet, known to many as Hickson Compact Galaxy Group 79, is a tight gathering of galaxies in the northern corner of Serpens Caput. Serpens Caput is the western segment of this bisected constellation, marking the triangular head of the serpent that Ophiuchus is handling. Observing Seyfert's Sextet has been one of my pet projects for years. It's a fun little galactic rat pack for summer outings before we plunge headlong into the summer Milky Way.

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Cosmic Challenge: February 2020 NGC 2298

Although most globular clusters line the summer sky as they huddle around the core of our galaxy, there are a few renegades that have stepped out on their own to occupy regions far beyond the rest. One such globular, nestled behind the rich Milky Way star fields of Puppis, is NGC 2298.

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