The Sky On Christmas Night

Merry Christmas, everyone! Maybe you’ll have clear skies tonight and feel like some fresh air. If so, here are a few sky sights you can expect to see on this special night.

Mars has faded to magnitude 0.4, but it’s still the brightest object in the southern sky at the end of evening twilight. Look for the orangey-red “star” more than four fists high in Pisces the Fish. For the next few nights, it passes just below the faint asterism called “The Circlet,” seven stars arranged in a small hoop visible with the naked eye in darker skies. In light-polluted skies, use binoculars. Stellarium

 

The comet’s back! 46P/Wirtanen is slicing across Auriga the Charioteer and well-placed for viewing in the eastern sky as soon as it gets dark tonight. Look for it 7° to the lower left (northeast) of bright Capella. By local midnight, it stands almost direct overhead, but don’t wait that late to see it because the moon will be up. The comet is still close to Earth and scurrying along at more than 2° per day. Stellarium
Last night (Dec. 24), the sky cleared off, affording a good look at comet 46P/Wirtanen, which has been comprised the past few nights by moonlight . It had faded a bit to magnitude 4.5, but I could still easily spot it in 10×50 binoculars before moonrise. Bob King
The waning gibbous moon comes into good view not far from Regulus in Leo tonight around 9:30-10 p.m. Sirius, the brightest star in the entire sky, twinkles in the southeast as Orion the Hunter holds sway in the south. Stellarium
The pre-dawn and dawn sky is where most of the planets are hanging out. If you’re up early tomorrow morning, you can’t miss Venus, shining like an approaching aircraft in the southeastern sky. Jupiter and Mercury follow in early morning twilight two fists to the lower left of Venus. Stellarium

16 Responses

  1. kevan hubbard

    Bob, spotted the comet on Christmas Eve at about 1745 before the near full moon rising.so well placed off the shoulder of capella.fuzzy ball and I’m guessing about 5th magnitude?

    1. astrobob

      Hi Kevan,
      Thanks for reporting. I agree — right around there. I estimated 4.5 and saw only VERY faintly with the naked eye. A little bit of moonlight though at the time.

      1. Kevin Kim

        Astrobob, I’m genuinely curious.
        Just learned that moon has about 16% on gravitational force that of earth. How did they back in1969, land the Apollo onto the surface? I ‘ve seen the footage of those astraunuts bouncing around on the surface. And also pictures of quite “deep” shoe imprints on its moon surface. Is the surface made of such fine dusts, even at 16% g. force, it can leave such a deep impression of shoes? Also, how was the aircraft landed to its surface? Was it descending slowly from the miles above the surface like the ironman with his palm thruster to slowly come down to surface? Maybe I’m ignorant for saying this, but with earth, an aircraft is engaged slowly into atmosphere in curvature to minimized the g force excerted on the aircraft, how did NASA figure out the gravitational force on moon to calculate for the landing of the moon and then fuel/ force requirements of the departure from moon surface to return to earth ?

        1. astrobob

          Kevin,
          One last thing. The upper half of the lunar lander had its own rocket engine, so when the astronauts were ready to return to orbit, they fired it, and the module lifted off the moon.

  2. Edward M Boll

    I have not seen it in a week. Binoculars were too much of a challenge in Full Moon light and now it is over cast. But I am ready to go again. With dark skies comet 64 is still brighter than mag 10. Hope to catch it yet before it is completely gone on this time around.

    1. astrobob

      Good luck on 64P, Edward. Let us know if you see it. At least it’s at a nice altitude. Still pretty diffuse though.

  3. Philip Astore

    Jupe, Merc. & Antares in a tricky Triangle this Morn. on my bluffs Bob! Clear & Transparent at a Bracing 19 Degrees. Bonus ISS Flyover too… :o) Thanks for these Heads Ups!

  4. Patrick

    Caught Wirtanen through binocs early on Christmas night. Thanks for the tip to get outside early to beat the moon. Easily spotted here in Truckee, CA with the benefit of some elevation. Andromeda also looked good, and looked a bit brighter to my eyes than Wirtanen.

    1. astrobob

      Patrick,

      Nice little Christmas present. Glad you found it. Based on your comparison with Andromeda, it sounds like the comet is beginning to fade.

  5. Dear Bob, I don’t have an email address of you (although I once had), so I write you a response to that xmas related entry, because mine is xmas related too.

    You used my calculation of comet’s dust tail twice or thrice in that blog and asked me in advance, of course. You I knew you at least a bit. As I read that you wrote “Wonders of the night sky” I set it at my wishlist for xmas. My wife bought a copy and now I have it. What a wonderfül book!

    Of course, ss a long time astronomer I have seen most of the wonders by myself. But your motivation is valuable for me to get others under the darks sky. There are wonders I don’t saw until now: A triple planet conjunction, all planets in one night, an earth grazing meteor and – inexcusable – the changings of eta Aquilae.

    Thank You again for that wonderful book. Among the first thing I read was the epilogue. What a deep philosophical text! Is Sammy still at life?

    Uwe Pilz, Leipzig, Germany.

    1. astrobob

      Dear Uwe,
      Thank you for writing, and I’m so glad you enjoyed my book. About Sammy. She stayed next to me during the time I wrote “Wonders,” but she was very old (17 years) and sick. It was one of the most difficult decisions I’ve ever made, but I brought her to the veterinarian last November to be euthanized. I miss her very much and think of her all the time. Perhaps you have a dog, too?

  6. Dear Bob, sorry to hear that form Sammy.

    We don’t have a dog but two cats (like in the song of the Beatles :). Both are 13 years now, but healthy.

    In 2005 we had Four Funerals and a Wedding (inverse to the film: My mother died, my wifes father passed away, her uncle too. And our old cat Felix. This was the most sad event form all of them. Felix was part of our family.
    But we had a wedding too: I married Maike, now my wife. She ist my second wife, I am sixty now. Together we have 4 children, 2 form each side.

    1. astrobob

      Uwe,
      I’m sorry to hear about Felix. Our pets are very much a part of our family. It sounds like you had a most difficult year. After Sammy, I decided for the time not to get a pet. Part of the reason was how difficult it was, but my wife and I would like to travel more as well.

  7. Kevin Kim

    Hi astrobob, fairly enjoyed your replies pertaining to questions about moon landing in 69.
    Astrobob, I’m genuinely curious.
    Just learned that moon has about 16% on gravitational force that of earth. How did they back in1969, land the Apollo onto the surface? I ‘ve seen the footage of those astraunuts bouncing around on the surface. And also pictures of quite “deep” shoe imprints on its moon surface. Is the surface made of such fine dusts, even at 16% g. force, it can leave such a deep impression of shoes? Also, how was the aircraft landed to its surface? Was it descending slowly from the miles above the surface like the ironman with his palm thruster to slowly come down to surface? Maybe I’m ignorant for saying this, but with earth, an aircraft is engaged slowly into atmosphere in curvature to minimized the g force excerted on the aircraft, how did NASA figure out the gravitational force on moon to calculate for the landing of the moon and then fuel/ force requirements of the departure from moon surface to return to earth ?

    1. astrobob

      Hi Kevin,
      Thanks for your great questions! Here are some answers:
      You can determine the moon’s gravitational attraction empirically here on the ground, but the easiest, most accurate way is to send a probe
      to orbit the moon and measure the pull of the moon’s gravity directly. NASA sent a bunch of those, so we knew well in advance of the landings that the moon had 1/6th
      the gravity of Earth. Neil Armstrong dressed in his big spacesuit weighed 353 lbs. equal to 59 lbs. on the moon. That’s plenty heavy (think of a 59-lb. bag of potatoes) to make a solid impression in the lunar dust. The lunar lander first separated from the command module and then later descended to the moon using its descent engines to brake the lander on its way down. It descended slowly, all the while decreasing in speed as it approached the surface. Since the moon is a vacuum, there is no air to push against. The engine burns push against the lander itself, slowing it down. Closer to the surface, Armstrong took manual control of the craft and used the attitude thrusters to avoid a crater filled with boulders and land in a safe place.

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