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The Stellar Nursery of Orion

Jan. 10, 2023 | By Geoff Chester, USNO Public Affairs

Messier 42, the Great Nebula in Orion
imaged at Ocean City, MD, 2021 December 27, 03:50 UT with an 80mm (3-inch) f/6 Antares Sentinel refractor,
iOptron Cube Pro alt-az mount, and a Canon EOS Rebel SL2 DSLR

The Moon moves into the morning sky this week, descending along the ecliptic to mingle with the rising springtime constellations.  Last Quarter occurs on the 14th at 9:10 pm Eastern Standard Time.  Luna begins the week near the two brightest stars in the “head” of Leo, the Lion, Regulus and Algieba.  Early risers will find her a few degrees east of the bright star Spica before dawn on the 15th.

The January campaign for the Globe at Night citizen-science program begins on the evening of the 13th.  In 2022 just under 20,000 people reported their observations of their local skies, and the program’s organizers hope to top that number this year.  This month’s featured constellation is Orion, the Hunter, which is probably the most recognized star pattern in the heavens.  Not only does it have a very distinctive shape, it is chock full of bright stars that make it an ideal target for urban stargazers.  Reports from city-bound skywatchers are just as important as those from dark-sky dwellers as the program aims to map the distribution of artificial lighting around the world.  From my yard in the Washington suburbs the seven stars that make up Orion’s basic shape are easy to see on a clear night.  If I find a spot not in the direct glare of street lights, several more stars become visible in the asterism known as “The Sword” and the small group of stars that mark the Hunter’s “head”.  As you move farther from the urban light domes the full outline of Orion becomes apparent as the fainter stars that demark his “club” and “shield” become apparent.  Under these skies Orion requires little imagination to “see” his character.  What will you see?  Go out on the next clear night, find a place not bathed in local light, and let your eyes adapt to the darkness for about 15 minutes.  Go to the Globe at Night web app, find the Orion chart that most closely matches your view, and submit your report.

Orion is a great place to do some urban stargazing.  His brightest stars have distinctive blue tints, with the exception of the red-tinted star Betelgeuse.  Orion’s principal stars are very far away, and many of them show small motions that lead back to the area of the middle star in the hunter’s “sword”.  Point a pair of binoculars toward that star and you will see a glowing smudge of light.  A small telescope will reveal a bright, mottled glow surrounding four closely spaced stars.  This is the heart of the Great Orion Nebula, one of the showpieces of the “deep sky”.  City dwellers can see the central parts of the nebula, and a four-inch telescope will start to show dark rifts of opaque gas.  Under dark skies the bounds of the nebula span much of the constellation in the form of faintly glowing wisps of gas and the dark tendrils of cold interstellar dust.  Most of Orion’s stars originated in this luminous cloud; it is estimated that there is enough material in the nebula to create over 10,000 stars with the mass of the Sun.  The four stars visible at the heart of the nebula’s brightest part, known as the “Trapezium”, are some of the youngest stars in the Milky Way galaxy, having formed only some 300,000 years ago.

Venus is now climbing rapidly in to the southwestern sky.  The dazzling planet is now easily seen shortly after sunset.  She sets about 2.5 minutes later each night, and by the week’s end is still visible at the end of evening astronomical twilight.  She will continue to climb higher above the western horizon as she moves northward along the ecliptic.  Over the next several weeks she will overtake Saturn, passing the ringed planet on the evening of the 22nd.  She will then set her sights on Jupiter, passing the giant planet on March 1st.

Saturn continues to slip closer to the Sun each evening.  You can still find him low in the southwest during fading evening twilight, but by the time the sky is fully dark he is only 10 degrees above the horizon.  He will be in conjunction with the Sun just over a month from now.

Jupiter still dominates the early evening sky, high in the south as twilight gathers.  You can train the telescope to his far-flung cloud tops as soon as he appears.  I often look at Old Jove during twilight, as the deep blue of the sky helps to cut down the bright glare of the planet’s bright zones.  You’ll have a couple of hours to enjoy the view of the giant planet before he sinks toward the western horizon. 

Mars appears in the twilight glow shortly after Jupiter, high in the eastern sky.  The red planet now transits at around 9:00 pm local time just 15 degrees from the zenith.  Although he has lost some of his opposition luster, he is still brighter than any of his nearby stellar companions.  Through the telescope his disc is becoming smaller, and careful examination will show him with a noticeable gibbous phase.  He reaches the second stationary point of this apparition on the 12th.

Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529