Castor and Pollux

Gemini is still well overhead, north and east of the constellation Orion, in the evening hours in March.

Gemini is still well overhead, north and east of the constellation Orion, in the evening hours in March. Its brightest stars are Castor and Pollux. Created with SkyX Serious Astronomer edition by Software Bisque.

Along with Taurus, Gemini is one of the two most northerly constellations of the zodiac. It lies just east of Auriga and the bright star Capella, and it’s marked by the two bright stars Castor and Pollux which lie less than 5º apart (a little less than the width of your three middle fingers held at arm’s length). To find the constellation draw an imaginary line diagonally from Rigel past Betelgeuse in the constellation Orion about a distance equal to the separation of these two bright stars. This will land you smack in the middle of Gemini. In March and April, the constellation lies still well above the western horizon in the early evening hours…

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The Bluest Star

An artist's impression of the outer layers of the star Naos (zeta Puppis). Credit: Wikipedia.

An artist’s impression of the outer layers of the star Naos (zeta Puppis). Credit: Wikipedia.

Scattered in a thick band south of Canis Major lie the stars and star clusters of the constellation Puppis. There are no stars here to visually rival the brilliant stars of the Big Dog or Orion further to the north and west. But visual appearances are deceiving because among the stars of Puppis is one of the most luminous and hottest stars in our part of the galaxy, the star Naos or zeta Puppis…

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The Sky This Month – March 2017

Waiting-for-Darkness-Winter-Star-Party-2017

Waiting for astronomical twilight at the Winter Star Party near Big Pine Key, Florida, on February 24, 2017.

1 March 2017. The Moon returns at the beginning of March in the form of a slender waxing crescent in the western sky after sunset. It’s joined by the fading but still respectably bright planet Mars and the unmistakable silver-white radiance of the planet Venus. Uranus lies 2º west of Mars and reveals itself easily in a pair of binoculars. These three planets are a study in contrasting brightness. Venus shines at magnitude -4.6, Mars at magnitude +1.3, and Uranus at magnitude +5.7. The Moon today has a total magnitude of -9.0. Each full step in magnitude is a factor of 2.512 in brightness…

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A Little Cluster in the Big Dog

NGC 2362, the Tau Canis Majoris cluster. Credit: Adam Block/Mount Lemmon SkyCenter, University of Arizona.

NGC 2362, the Tau Canis Majoris cluster. Credit: Adam Block/Mount Lemmon SkyCenter, University of Arizona.

The constellation Canis Majoris, the ‘Big Dog’, is home to many fine open clusters of blue-white stars along the stubby Orion Arm of the Milky Way. There are some real gems here, including the modest but delightful open star cluster NGC 2362, a group that hosts some of the youngest-known stars. Centered on the bright star τ (tau) Canis Majoris, this cluster, in a telescope, looks like a large diamond set among many smaller blue-white gems…

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NGC 2477 – The Electric Guitar Cluster

NGC 2477 (also known as Caldwell 71) is an open cluster in the constellation Puppis. It contains about 300 stars, and was discovered by Abbe Lacaille in 1751. The cluster's age has been estimated at about 700 million years. NGC 2477 is a stunning cluster, almost as extensive in the sky as the full moon. It has been called "one of the top open clusters in the sky", like a highly-resolved globular cluster without the dense center characteristic of globular clusters. Credit: J. Perez/ESO.

NGC 2477 (left) and NGC 2451 (right) are one of the most beautiful pairs of star clusters in the sky Credit: J. Perez/ESO.

We turn our gaze to the southern reaches of the constellation Puppis, south and east of the bright star Sirius and Canis Major, to examine two stunning star groups in a rich field of the Milky Way.

The first stop is the star cluster NGC 2477. Discovered by Nicolas de Lacaille (the ‘father of southern astronomy’) in 1752, this is a glorious star cluster, bright enough to be visible without optics from southern latitudes. It’s a fantastic binocular object, but it’s best viewed at low-power with a small telescope where it fits in the same field of view as an adjacent star cluster, NGC 2451.  At a distance of 3,700 light years, NGC 2477 is one of the richest and densest of open star clusters and looks a little like the loose globular cluster M71 in the constellation Sagitta. The cluster has an impressive 1,900 members and spans about 37 light years. It’s also an ancient cluster, about 1 billion years old, and likely has lost many members since its birth to gravitational perturbations from other stars and star clusters…

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The Sky This Month – February 2017

The full Moon is partially in the Earth's shadow during a penumbral lunar eclipse. Credit: Radoslaw Ziomber/Wikipedia Commons.

The full Moon is partially in the Earth’s shadow during a penumbral lunar eclipse. Credit: Radoslaw Ziomber/Wikipedia Commons.

2 February 2017. Look for the bright white star Spica in the constellation Virgo and the much brighter planet Jupiter in the southeastern sky well before sunrise. The pair lie within about two finger widths of each other for most of the month.

2-3 Feb. The dwarf planet Ceres lies about 1º south of the waxing crescent Moon. Some observers across southern Europe, North Africa, Central America, and northern South America will see the little world pass behind the Moon at roughly 02:00 UT on Feb. 3. Ceres shines at about 9th magnitude, easy to see in binoculars or a telescope, although the glare of the Moon makes it a little harder to spot. Ceres is the largest of the dwarf planets in the asteroid belt. It’s a nearly round world with a diameter of 950km. That makes it the 33rd largest object in the solar system…

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The Allure of Carbon Stars

The carbon star R Leporis. Credit: Damian Peach

The carbon star R Leporis. Credit: Damian Peach

For visual observers with small optics, the colors of the deep sky range from subtle to nonexistent. Galaxies and nebulae cast too little light to stimulate the color-sensing cone cells in our retinas, so they appear pale gray-white or, in the case of a bright planetary nebulae, gray-green. Bright stars are a little more colorful. Betelgeuse appears clearly orange, even to the unaided eye, Rigel shines blue-white, and the showpiece double star Albireo in the constellation Cygnus shows off a blue-green primary and red-orange secondary in even the smallest telescope. Otherwise, star colors are quite subtle, especially to new stargazers. But there is one exception– carbon stars. These deep ruby-red stars, which dredge up nuclear soot from their innards, give off a striking glow that’s easy to see in a small telescope. See your first carbon star and you’ll want to see many more…

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The Attendants of Mirfak

The star Mirfak and its 'Attendants', the cluster known as Melotte 20, are at the bottom of this image, just right of center. Closer to the center of the image, just rightward, lies the famous Double Cluster.

The star Mirfak and its ‘Attendants’, the cluster known as Melotte 20, are at the bottom of this image, just right of center. Closer to the center of the image, just rightward, lies the famous Double Cluster.

Nearly overhead in the after-dinner hours of a northern winter night, the rich constellation Perseus offers even a modestly-equipped amateur astronomer many hours of pleasant stargazing. Named after the great hero of Greek mythology, Perseus finds itself in the starry plane of the Milky Way Galaxy where thousands of brilliant blue-white stars have coalesced in the the last few tens of millions of years. Near the star Mirfak, or α (alpha) Persei, the brightest star in Perseus, lies a particularly dazzling collection of associated blue-white stars  that make up a loose cluster often called the “Attendants of Mirfak”. This little group is a beautiful sight in binoculars…

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Three Clusters and a Cheshire Cat

The stars along the northern Milky Way rising in the eastern sky. To the right lies the Hyades above which is the smaller Pleiades star cluster. To the right lies the constellation Auriga, the Charioteer.

The stars along the northern Milky Way rising in the eastern sky. To the right lies the Hyades above which is the smaller Pleiades star cluster. To the left of center in this image lies the constellation Auriga, the Charioteer.

Visible nearly overhead in the northern hemisphere, the bright constellation Auriga makes for pleasant viewing this time of year. The constellation, which looks like a big hexagon about 15° across, sits in a fine star field along the northern Milky Way directly opposite the much richer sky near the galactic center in Sagittarius. Auriga also holds the dazzling star Capella, the most northerly first-magnitude star in the skies. The constellation is also visible above the northern horizon from most populated parts of the southern hemisphere. Whether you have a pair of binoculars or a small telescope, make an appointment to examine the three finest open star clusters of Auriga– M36, M37, and M38– along with a smiling asterism embedded in the stream of the Milky Way…

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A Guide to Observing Comet 45/P Honda–Mrkos–Pajdušáková

Comet 45P/Honda-Mrkos-Pajdusakova imaged by amateur astronomer Tim Puckett in 2011.

Comet 45P/Honda-Mrkos-Pajdusakova imaged by amateur astronomer Tim Puckett in 2011.

A little periodic comet is visiting the inner solar system over the next few months. Comet 45/P Honda–Mrkos–Pajdušáková, a tiny piece of ice and dust left over from the earliest days of the solar system, moves periodically around the Sun every 5.25 years. It made its closest approach to the Sun on December 31, 2016 and it’s visible now. As it passes close to Earth in February, it will brighten and appear to move quickly across the sky from day to day. You’ll need binoculars to see it, but it’s worth following this little leftover hunk of the early solar system…

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