July 21, 2019

Astro-Event(s): A Solstice, a Meteor Shower and a Bizarre Transit.

The Winter Solstice… here comes the Sun!

(Credit: Art Explosion).

T’was the night before Christmas, and no doubt dreams of high tech astro-gear is dancing thru the head of many a star stricken astronomer out there. But while you’re awaiting those astro-gifts, the universe marches on. This week’s sky events run the gamut, from a solstice for residents of both hemispheres, to an unknown meteor shower that may be on the upswing, to a difficult to observe transit. Here are some events to watch for on the long cold northern hemisphere nights;

First up, the Sun reaches its southern-most point on its apparent journey on December 22nd at 12:30 AM EST/5:30AM UT and begins its long journey northward. And while northern residents celebrate the start of winter and the long march towards spring, its the start of summer Down Under. However, all Earthly residents can commemorate the solstice (whether they know its origins or not) with the appropriate Christmas/Saturnalia/Insert holiday here tie-in. If it’s sunny, the solstice is a great time to note the Sun’s rising & setting points along the horizon as well as the transit point at midday, just as the ancients did. This year’s December solstice is the latest it’s fallen since 2007, and it won’t fall this late again ‘til 2015. The reason is that next year is a leap year, and this will “reset” the solstice/equinox cycle back again by 24 hours to make up for that pesky .25 (roughly) days a year we gain. And yes, even that cycle slips about 5-6 minutes or so per year, so that we have to drop a leap year every century year except those divisible by 400, such as occurred in the year 2000… tricky, huh?

Location of the Ursid radiant. (Created by the Author in Starry Night).

Next up is a fairly obscure meteor shower that has shown some signs of renewed activity in recent years known as the Ursid meteors. This shower has a high northern radiant very near the bright star Kochab in the bowl of the constellation Ursa Minor. It generally produces a paltry 10-20 meteors per hour, but rates have been on the rise and the shower has produced very brief swarms of up to a 100 per hour historically. The source of the Ursid meteors is the short period comet 8/P Tuttle, which made a close (0.25 astronomical units) pass by the Earth on January 2nd, 2008. Like next month’s Quadrantids, the Ursids seem to have a very short-lived peak of about 12 hours and are still very poorly understood. This year might be an especially auspicious time to stand vigil for this shower as the Moon will be only 6% illuminated on the 22nd, the traditional peak of the shower, as it slides towards New phase on 24 December at 13:06EST/18:06UT… be sure to watch either side of December 22nd; you just might catch this shower in action!

Finally, an astro-challenge. A bizarre transit came to our attention via the message boards some time ago, and although no one may catch it, it’s a curious specimen. On December 22nd, the asteroid 650 Amalasuntha will transit the disk of Jupiter as seen from the southern hemisphere of the Earth. Yes, you read that right…catching such an asteroid-planetary transit pairing is rarer than, oh say, Ed McMahon transiting your doorstep with 20 million dollars.

650 Amalasuntha is named after the 6th century queen of the Ostrogoths and was discovered in 1907 by August Kopff. The transit occurs a little past 17:00 UT on the 22nd, and is best visible from the African continent eastward as Jupiter rides high in the sky after sunset; the rest of us north of the equator will get a close graze. The screenshot below is set for South Africa:

Asteroid transit as seen in Starry Night.

At said location, the transit will run from 17:19UT to 18:32UT, or about an hour and 13 minutes.

One caveat is in order; this will be a very difficult transit to observe due to the contrast in brightness; 650 Amalasuntha never gets brighter than 13th magnitude, and Jupiter currently shines at a dazzling -2.6 magnitude. Plus, 650 Amalasuntha will be <1” arc second in size compared to Jupiter’s 44” diameter. Amalasuntha is 1.35 A.U.s distant during the event while Jupiter stands at 4.4 A.U.s from Earth. It’s very likely that no earthbound resident will witness this curious cross; still, with the amazing things folks are doing with webcam astrophotography these days, we’d love to hear of a success story… your best bet is to begin tracking 650 Amalasuntha some days prior. A list as calculated by Jean Meeus of further unusual asteroid planet transits is up on the MPML message board for pursuing… Good luck and good hunting!

 

Comments

  1. steve says:

    If a transit of a disc 44″ across is rare, how about a transit of a star that is 0″.050 across.
    That’s Al Mankib, on 2012 January 2.

  2. anonymous says:

    this computation is incorect at 200” from Jupiter in real terms. sorry for that.

  3. David Dickinson says:

    No problem; the ephemeris used is the most current available from the JPL database; if you have access to something different I would be happy to see it. Keep in mind, the transit was only visible across a line south of the Earth’s equator; the position of Amalasuntha varied across the viewing positions from the surface of the Earth. Thanks for commenting.

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