Solstice Fireballs

Ursa Major – the Great Bear – and the Big Dipper where the Ursid meteor shower seems to originate.

As is often the case here in December, viewing conditions for watching meteor showers recently for the Geminids were lousy – clouds and rain. There’s another chance this week for a smaller event.

The annual Ursid meteor shower was visible to some starting earlier this week (clouds and rain for me again) but it typically peaks around the Winter Solstice. The Ursids are not as impressive a show as the Geminids, but I’ve missed seeing almost any meteors all year so I’m hungry to catch at least a few this time. And with my sons and daughters-in-law visiting for the holidays, I will probably push them outside on a clear night to watch for a fireball.

The Ursid meteor shower runs from about December 17 to 26 each year. I associate it with the Winter Solstice and Christmas so it does have a kind of special place in my celestial calendar.

The Moon will be in its waning crescent phase this weekend which will make the sky much darker than it was for the Geminids. On Christmas Day there will be a dark as possible New Moon.

The Ursids may show 5-10 meteors per hour in a dark sky with a rare burst of more (near 100) in some years.

The Ursids get their name from where they appear to originate. Look to the Big and Little Dipper asterisms which are in the constellations Ursa Major and Ursa Minor.

Ursa Major, the Great Bear, is a constellation in the northern sky. The Latin name means “greater (or larger) she-bear” to contrast it with the nearby Ursa Minor, the lesser bear. It was one of the original 48 constellations listed by Ptolemy in the 2nd century AD.  Ursa Major is well known for the asterism of its main seven stars, which we call the Big Dipper which resembles the Little Dipper in Ursa Minor. The bears’ tails are the handle of the dipper cups.

Ursa Minor may be smaller but it contains Polaris, better known as commonly the North Star or Pole Star, which is the brightest star in this constellation.

For those of us in the Northern Hemisphere this weekend, the Big Dipper is pretty far up in the north-northeast sky by midnight. Midnight into early morning is a good time to watch. I think I’ll make some nice late-night hot toddies tomorrow night to lure the kids outside.

Full Moon, Solstice and Meteors

I will be traveling over the weekend and away from my computer, so I’m giving an early post about three upcoming celestial observations . Saturday, December 22, 2018 is our final full moon of the year and it occurs less than a day after the Winter solstice. That is close enough that to most people it will look like a Full Moon on the solstice. For those of us in the Northern Hemisphere, the solstice will be the longest winter night, but a big bright Moon will be a celestial nightlight for many of us. This is the third closest and largest of this year’s 13 full moons. I would guess to the ancients who were attentive to celestial occurrences, they might have seen deeper meanings in these three simultaneous events. A December solstice and Full Moon happening less than a day apart last happened in 2010. The next time will be 2029. I missed any good view of the Geminid meteor showers last week due to clouds and rain. This week the annual Ursid meteor shower occurs and they typically peak around the December solstice. They will still be strong on the 22nd and continue until about the 28th. The Ursids are not as impressive as the Geminids, although if you have never seen a meteor shower of “falling stars” or “fireballs” (get those kids outside!) seeing even a few is pretty impressive. I would recommend that you go out and look to the Big and Little Dippers. Ursa Major and Ursa Minor give their names to the meteor shower and are easy to find late at night high in the north-northeast. The big glare of the first December solstice full moon since 2010 will unfortunately being a celestial nightlight that will wash out some of the darkness.

You never see the Moon rotate as in the video above where it spins in full rotation. This footage from NASA explains that we never see this because our Moon is tidally locked in its orbit to the Earth, and so always shows us only one side. It takes some digital technology to combine many HD images from the Lunar Reconnaissance Orbiter (LRO) to make this virtual Moon rotation video. In this time-lapse video, we start with the standard Earth view of the Moon, then an entire lunar month is condensed into 24 seconds. Early full moons in December were called the Moon Before Yule by the European colonists who also knew it as the Oak Moon (Medieval English), Frost Moon, Freezing Moon, and Snow Moon. Native Americans had many names for this Full Moon including Long Night Moon, Cold Moon, Small Spirits Moon, Moon When the Wolves Run Together (Cheyenne) Moon of Respect (Hopi), and Moon of Popping Trees.

Ursa Major Never Sets

The stars move with our seasons. For most of us, some move below the horizon and we lose sight of them for part of the year. But the circumpolar stars stay above the horizon all hours of the day, every day of the year. They are there now, even if it is daylight as you read this, they are there. there’s not a lot you can count on here on Earth – or even in the heavens – but you can count on them.

The Big Dipper asterism is the best known of the circumpolar groups at all latitudes north of 41 degrees north latitude. (That is the northern half of the mainland United States and most of Europe.)

The Big Dipper is part of a bigger constellation, Ursa Major or the Great Bear.

In Greek mythology, the god Zeus had fallen in love with the maiden Callisto. In a story that would make the news today, and get Zeus some bad headlines, Zeus got her pregnant. Callisto was a nymph in the retinue of the goddess Artemis. But she would not be with anyone but Artemis. Zeus disguised himself as Artemis and seduced Callisto. When the child Arcas was born, Zeus’ wife Hera turned Callisto into a bear in revenge.

Callisto wandered the forest for years in bear form, until a chance meeting with her son, Arcas. He was the king of Arcadia and a great hunter. He raised his spear to strike at the bear, not knowing it was his mother. Zeus stepped in and sent them up to the heavens with Callisto as the Great Bear and Arcas as Bootes the Herdsman. (Or maybe he is Ursa Minor, the Little Bear,  depending on whose mythology you follow.) Hera was not pleased that Zeus stepped in, so she wever, and conspired with the gods of the sea so that the Bear could never swim in the ocean. That is one explanation – totally unscientific – for why Ursa Major never sets

The Big Dipper is circumpolar, so it is visible year round. It is up in the spring and down in the fall. The pointer stars in the bowl of the Big Dipper always point to Polaris, the North Star |  |  Image via Chris Mihos, Department of Astronomy, Case Western Reserve University

Where are you? If you’re with me in the Northern Hemisphere, every star north of the celestial equator is circumpolar, and every star south of the celestial equator is below the horizon. At the Earth’s South Pole, every star south of the celestial equator is circumpolar, whereas every star north of the celestial equator remains beneath the horizon.

And at the Earth’s equator, no star is circumpolar because all the stars rise and set daily in that part of the world. You can actually see every star in the night sky over the course of one year.