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Phil Harrington's Cosmic Challenge Archives

Cosmic Challenge: Satellites of Uranus

Nov 01 2019 05:00 AM | PhilH in Phil Harrington's Cosmic Challenge

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: The Deer Lick Group

Oct 01 2019 05:03 AM | PhilH in Phil Harrington's Cosmic Challenge

The autumn sky abounds with little bundles of galaxies scattered throughout its stars. One of the best known is the group of 7 galaxies that surround the magnificent spiral NGC 7331 in Pegasus, the Flying Horse. An observer could easily spend an hour or more just soaking in all that this small patch of sky has to offer.

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Cosmic Challenge: Emission Nebula Simeis 57

Sep 01 2019 10:16 AM | PhilH in Phil Harrington's Cosmic Challenge

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: Planetary nebula IC 4732

Aug 01 2019 04:55 AM | PhilH in Phil Harrington's Cosmic Challenge

M22 is right in the thick of it, not far from the galactic center of the Milky Way. As such, it has lots of company. One particular planetary nebula proves a worthy adversary through 10- to 14-inch scopes: IC 4732. IC 4732 lies just 1.4° north-northwest of M22. Cataloged at magnitude 12.1, its tiny disk is difficult to pick out from the mob of field stars -- difficult, but not impossible.

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Cosmic Challenge: Lunar craters Armstrong, Aldrin, and Collins

Jul 05 2019 11:22 AM | PhilH in Phil Harrington's Cosmic Challenge

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: Apollo Landing Sites

May 31 2019 11:46 AM | PhilH in Phil Harrington's Cosmic Challenge

Between July 1969 and December 1972, six teams of United States astronauts ventured across the gap between Earth and Moon to land and walk on that distant world. Have you ever visited their landing sites? If not, let's do so now.

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Cosmic Challenge: M51's spiral arms

Apr 30 2019 07:52 AM | PhilH in Phil Harrington's Cosmic Challenge

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: Leo III

Mar 30 2019 09:54 AM | PhilH in Phil Harrington's Cosmic Challenge

A springtime rite of passage started here two years ago. It started in the April 2017 edition of this e-column, when I challenged readers to find the dwarf galaxy Leo I. Leo I is one of many dim dwarf galaxies gravitationally bound to the Milky Way. The fact that its surface brightness rates only 15th magnitude, coupled with its position just 20' north of Regulus makes Leo I a tough challenge to land.

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Cosmic Challenge: NGC 2363 and NGC 2366

Feb 28 2019 04:59 PM | PhilH in Phil Harrington's Cosmic Challenge

Will the real NGC 2363 please stand up? For years, there has been an ongoing debate over the true identity of the 2,363rd entry in the New General Catalog.

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Cosmic Challenge: Sharpless 2-301

Feb 01 2019 02:39 PM | PhilH in Phil Harrington's Cosmic Challenge

While a few of Sharpless's entries, such as Sh2-25 (better known as M8, the Lagoon Nebula) and Sh2-49 (M16, the Eagle Nebula), are well known to visual observers, most are among of the most challenging objects to see visually. If you have never made a concerted effort to see some of the lesser known Sharpless objects, then this challenge, Sh2-301 in Canis Major, is a good introduction to the sport.

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Cosmic Challenge: Jonckheere 320

Jan 01 2019 06:04 AM | PhilH in Phil Harrington's Cosmic Challenge

On January 22, 1916, while revisiting some of the stars in his Catalog and Measures of Double Stars discovered visually from 1905 to 1916 within 105° of the North Pole and under 5" Separation, French astronomer Robert Jonckheere returned to a vague double in Orion, which he had previously designated as entry number 320. Jonckheere was later to write of this encounter through the 28-inch refractor at the Royal Greenwich Observatory, "I noticed that the object I have catalogued as J 320 is not a double star, but, like J 475, it appears with the larger instrument to be an extremely small bright elongated nebula. As is the case with J 900, this object also appears to be new as a nebula."

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Cosmic Challenge: Globular clusters in M31

Dec 01 2018 06:00 AM | PhilH in Phil Harrington's Cosmic Challenge

The Andromeda Galaxy, M31, was probably one of the first galaxies you ever saw first-hand. It was mine. That was all way back in 1969. Since then, I have grown to appreciate it as far more than just the ill-defined oval blur I drew in my logbook. But in 1969, the thought of looking for individual objects within M31 never crossed my mind.

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Cosmic Challenge: NGC 147 and NGC 185

Nov 04 2018 08:46 AM | PhilH in Phil Harrington's Cosmic Challenge

M32 and M110 are nice challenges for handheld binoculars. Most amateurs are familiar with them, since they lie in the same field of view of the parent Andromeda Galaxy. But two others, designated as NGC 147 and NGC 185, are not as nearly well known. Both are several degrees to M31's north, across the border in Cassiopeia and feature smaller, fainter disks that are much more challenging to see.

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Cosmic Challenge: Einstein's Cross

Oct 01 2018 08:53 PM | PhilH in Phil Harrington's Cosmic Challenge

From an aesthetic perspective, the most perfect gravitational lens is Einstein's Cross, formed by the galaxy PGC 69457 (cross- cataloged as CGCG 378-15) and the quasar QSO 2237+0305 in Pegasus. PGC 69457 is also known informally as Huchra's Lens after its discoverer, John Huchra, professor of cosmology Harvard University. Current estimates place this small, otherwise unspectacular spiral galaxy at 400 million light years away. The quasar lurks far behind at an incredible distance of 8 billion light-years. Were it not for gravitational lensing, the quasar would remain hidden by the galaxy, as the two are nearly in-line as seen from Earth. But as it is, Huchra's lens fractures the ancient light from the quasar into four separate paths that slide around the galaxy just as water flows around a rock in a stream. The end result is not one, but four ghostly images of QSO 2237+0305 surrounding the nucleus of PGC 69457 in a practically perfect diamond pattern.

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Cosmic Challenge: North America Nebula (NGC 7000)

Sep 01 2018 05:07 PM | PhilH in Phil Harrington's Cosmic Challenge

The North America Nebula (NGC 7000) is a large expanse of glowing hydrogen gas mixed with opaque clouds of cosmic dust just 3° east of Deneb [Alpha (α) Cygni] and 1° to the west of 4th-magnitude Xi (ξ) Cygni. Famous as one of the most luminous blue supergiants visible in the night sky, Deneb marks the tail of Cygnus the Swan, or if you prefer, the top of the Northern Cross asterism.

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Cosmic Challenge: Campbell's Hydrogen Star

Jul 31 2018 06:56 PM | PhilH in Phil Harrington's Cosmic Challenge

American astronomer William Wallace Campbell spotted this unusual star-like object through a visual spectroscope at Lick Observatory in 1893. He could tell immediately from its spectrum that, despite its stellar appearance, he was not seeing an ordinary star at all. Instead, he had spotted an uncharted planetary nebula.

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Cosmic Challenge: Dissecting M101

Jul 01 2018 05:22 AM | PhilH in Phil Harrington's Cosmic Challenge

Just spotting the gigantic Pinwheel Galaxy, M101, can sometimes be challenging enough. Its low surface brightness can drive suburban observers crazy, especially when we see photographs that show it so big and bright, or that it is listed as 8th magnitude. It all comes down to surface brightness, or more accurately, lack of surface brightness. Seeing the dim glow of the galaxy's small core, or the even dimmer glimmer of the surrounding spiral arms, can take a concerted effort. But with time and patience, M101 is visible, with difficulty, through 50-mm binoculars even given a suburban sky with a naked-eye limiting magnitude of perhaps 4.5.

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Cosmic Challenge: Glimpsing Vesta

Jun 01 2018 06:34 AM | PhilH in Phil Harrington's Cosmic Challenge

Vesta turns out to be more like a mini-planet than like the chunks of rock most think of as asteroids. Dawn's measurements of the gravity field provided good evidence that Vesta's interior is separated into layers, much like Earth did as the planet was forming. Vesta's dense core - apparently once molten, but now solidified - is composed principally of iron and nickel, just like Earth's. Estimates place it at 125 to 150 miles (200 to 250 kilometers) across. Surrounding that is the mantle, which in turn is covered by the veneer of the crust, about 12 miles (20 kilometers) thick. It is now believed that early on Vesta was likely still accumulating material to become a full-fledged planet when Jupiter's immense gravity intervened, putting a stop to that. As a result, when we look at Vesta, many believe that we are seeing a protoplanet frozen in time.

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Cosmic Challenge: M109

May 01 2018 05:20 AM | PhilH in Phil Harrington's Cosmic Challenge

Messier did not live to see a second edition of his catalog, but objects 104 through 110 have been added posthumously by others. M109 joined the ranks in 1953, when astronomy historian Owen Gingerich noted Messier's observations of six additional "Méchain objects," now known as M104 through M109.

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Cosmic Challenge: Leo II

Mar 31 2018 09:54 AM | PhilH in Phil Harrington's Cosmic Challenge

Last April, this column profile the dwarf spheroidal galaxy Leo I, discovered by chance in 1950 by astronomers Robert Harrington (still no relation!) and A.G. Wilson as they were scanning the Palomar Sky Survey. I ended that column saying that "Using the right eyepiece and knowing the field will help you add this dwarf spheroidal to your list of conquered challenges with comparative ease. But don't get too cocky. Spotting its sibling, Leo II is an even greater challenge. But we will leave that for a future column." Well, that future is now.

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Cosmic Challenge: NGC 2419

Mar 04 2018 08:21 AM | PhilH in Phil Harrington's Cosmic Challenge

Probably known better by its nickname the "Intergalactic Tramp" bestowed by Harlow Shapley in 1944, NGC 2419 is unusual among winter's deep-sky objects for many reasons.

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Cosmic Challenge: The Orion Galaxy

Feb 03 2018 10:06 AM | PhilH in Phil Harrington's Cosmic Challenge

You've heard of the Andromeda Galaxy and the Orion Nebula, but how about the Orion Galaxy? Probably not. But would you believe the New General Catalog lists 21 galaxies in Orion, and the Index Catalog adds another 9? That's a pretty respectable tally. Of those 30 Orion galaxies, I find this month's challenge particularly intriguing because it lies so close to everyone's favorite winter deep-sky object, M42. Yet, I am sure that very few observers have seen it.

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Cosmic Challenge: Alphabet Soup

Jan 02 2018 08:36 AM | PhilH in Phil Harrington's Cosmic Challenge

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: Abell Galaxy Cluster 426

Dec 07 2017 06:02 AM | PhilH in Phil Harrington's Cosmic Challenge

Not long after I got my first "good" telescope, my 8-inch Criterion RV-8 Dynascope Newtonian reflector, as my Christmas gift in 1971, I became fascinated with the Perseus Galaxy Cluster. One reason I am so fond of this collection of more than 500 galaxies is that the cluster grows as the telescope's aperture increases. Small backyard scopes will show the two big kids on the block, NGC 1272 and NGC 1275, but even the largest amateur instruments fail to show all of the "little guys."

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Cosmic Challenge - NGC 404

Nov 17 2017 08:36 PM | PhilH in Phil Harrington's Cosmic Challenge

Did you know that I discovered a comet in the fall of 1973? I was out with my venerable 8-inch Criterion RV-8 Dynascope Newtonian reflector, just hopping around the autumn sky, when I noticed stars weren't focusing sharply. Thinking the telescope's collimation was off, I aimed at a nearby bright star to check whether the silhouette of the secondary mirror was centered correctly in the star's out-of-focus image. After I tweaked things a bit, all appeared well, so I focused on that star to check things before moving on. Lo and behold, I saw a dim blur of light right next to the star! Checking things further, it wasn't an internal reflection or an optical aberration.

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