Jane Houston Jones » Mercury

What’s Up in 2013 at a glance

jane — Mon, 07 Jan 2013 18:29:31 +0000

All year long, astronomers have been writing about Comet ISON: will it sizzle or will it fizzle? Both! Here’s my What’s Up video, with December status (written in mid November, but luckily, the comet didn’t completely fizzle)

ISON in December 2013

Comet ISON first spotted by amateur astronomer Bruce Gary and has been imaged by many eagle-eyed observers with good astrophotography equipment since mid August. A selection of images and data are shown here. I’ll update this frequently as more is understood about Comet ISON. Meanwhile, here is a wesbite with current Comet ISON magnitude and location which is constantly updated!

Comet ISON survived its close pass of the sun on November 28. Scientists are unsure what is actually left of the comet. A fragmented nucleus? Nothing but orbiting dust? Stay tuned!

Here’s an excellent Star Chart showing Comet ISON’s path in November, courtesy of Skyhound’s Skytools3 software. (These are the charts I use for my own deep sky observing.) The chart has not been updated for December as of November 30th.

Latest visible comet news here.

December 2013

You may have noticed a very bright ‘star’ in the western sky. That’s Venus! Venus shines at its very brightest, magnitude -4.9 this month. It sets about three hours after sunset at the beginning of the month and one and a half hours after sunset at the end of the month. This is a great month to view the dramatic changes in the apparent diameter and phases of Venus as it races towards its conjunction with the sun. The first observations of the phases of Venus were made by Galileo in 1610!

Mars continues to grow brighter and rises near midnight, and Jupiter rises earlier in the evening, heralding the best viewing season for Jupiter watchers.

The beautiful Geminid meteor shower will only slightly be marred by moonlight on the night of December 13 and 14. The radiant lies near Gemini with brilliant Jupiter above and the constellation Orion below. From a dark sky, but even from the city, the mighty hunter Orion is easily visible in the southeast sky. Take a look at Orion’s shoulder star, red Betelgeuse and its knee star, blue Rigel and the Orion Nebula.southwestern horizon.

The Milky Way and all the visible planets and comets should encourage stargazers to escape the city lights this month. Join me in the California Desert November 30, at MOjave National Preserve. We have no chance to See ISON for another week, but there are other nice comets, planets, stars, and dark sky objects too enjoy from dusk to dawn.

The times to look will be just after dusk, low to the horizon at sunset, and higher at dawn for northern latitudes the first half of the month. On December 1, look for a pretty diagonal lineup of the comet, Mercury and the crescent moon just before sunrise in the southeast. Then for the second half of the month, the comet becomes circumpolar. It will appear near the constellation Draco on December 26th, when it is half an a.u. (0.42 a.u.to be exact) from Earth. Will the comets’ tail span a quarter of the sky? I’ll update this as more info is available.

Jupiter reaches opposition January 4th, 2014, and rises earlier in the evening. Venus bright as it ever gets – a whopping magnitude -4.9. It will be a fabulous view – a particularly good astrophoto and sketching target as it grows in diameter, but shrinks in phase. Mars increases in brightness and rises earlier (after midnight). Mars will be a great target for 2014.

That’s all for this year, I’m Jane Houston Jones

The Crescent Moon

jane — Sat, 19 Feb 2011 21:47:05 +0000

The moon's summer and winter path, courtesy NASA's Starchild website

The winter's moon - a smiling crescent just after sunset Feb 5, 2011 (click to see moon upper center)

Closeup of winter crescent moon

The summer's "backwards C" crescent moon at sunset, late June 2007 (click to see moon in lower right)

Closeup of summer crescent moon

Have you ever wondered why the crescent moon looks like a smile in the winter and spring and like a backwards “C” in the summer and fall? It looked like a smile right now – below, next to and above Jupiter for several days after the February new moon. You can see the same waxing (getting bigger) crescent in early March 2011. Just look in the western sky after sunset beginning the day after new moon, on about March 5 or 6th. You’ll also see Jupiter and Mercury just above the horizon an hour after sunset.

Early birds can see a repeat of the waning (getting smaller) crescent moon phase a few days before the new moon, too. Look in east the last days of February up until new moon on March 4th. That bright object sharing the dawn skies with the crescent moon is the planet Venus! You can read more about moon phases here on the EarthSky website.

The best way to understand the reason why, is to look where the sun is, and how and where it shines on the moon. Draw an imaginary line connecting the setting sun, the moon, and any other planets that appear in the sky. That imaginary line is the ecliptic – the path the sun takes through the stars. It’s also the Earth and planets’ orbital plane. You can think of it as a projection of Earth’s plane on a sky sphere. The planets orbit the Sun, and the moon orbits the Earth and so you will always find the planetary lineup along the ecliptic.

In the winter and spring, the ecliptic appears almost vertical and arcs higher in the sky. The moons’ lit side faces the sun. That makes the waxing crescent moon look like a smile, or a boat, or the old moon in the new moons’ arms once light reflected off the Earth – called earthshine – reveals the unlit disk of the moon lit by reflected from Earth.

In the summer/fall, the ecliptic has a lower or shallower angle in the sky, and the lit crescent, as always, faces the sun, showing us a lit crescent facing the sun, which appears like a backwards “C”. I could write more, but instead, I’ll let you enjoy the images from our own observing sessions in the winter and the summer, and then get out and see the crescent moon for yourself soon.

Chasing Galileo – Jupiter and the four Galilean satellites

jane — Fri, 12 Jun 2009 01:12:33 +0000

Galileo's drawing

my drawing

my sketch of Jupiter's rotation

Galileo published his observations in Sidereus Nuncius in March 1610: “On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavons through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet…When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night.”

“I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter.”

Every amateur or accidental astronomer who first views Jupiter and its lineup of moons, is amazed at the view. Galileo’s 1610 discovery of these four moons orbiting Jupiter changed history. Looking at the Jovian moons through a small telescope, while trying to imagine Galileo’s first observations, takes my breath away!

A page from Sidereus Nuncius: 1610

First page of my observing log: 1989

My first sketches of the rotation of the four Galilean satellites: 1989