Category: Astronomy

Exploring the cosmos

Venus Disappears into the Sunset

Crescent Venus
Venus approaching inferior conjunction, 24Dec2013
Over the next few days Venus will slide into the sunset on its way to inferior conjunction on January 11th. This evening the planet is 16° from the Sun, this decreases by about 1° each day. As the new year begins the planet will become ever more challenging to see as it orbits into the Sun’s glare.

Tomorrow night, January 1st will see a nice conjunction of Venus and a thin crescent Moon

Quadrantid Meteor Shower

The first meteor shower of 2014 is the annual Quadrantid meteor shower. The Quadrantids are a reliable shower, producing 60-120 ZHR, one to two meteors per minute. The Quadrantids are named for the obsolete constellation Quadrans Muralis, now part of the constellation Boötes.

Leonids in Orion
A pair of Leonid meteors streak through Orion
Unlike other showers where activity can occur for days or even weeks, the Quadrantids have a sharp peak, activity falls off rapidly on the preceding and following nights, or even a few hours away from the peak. Thus it is important to observe the Quadrantids quite near the peak prediction. For 2014 the peak is predicted for January 3rd around 19:30UT, or 09:30HST on this side of the globe. The best timing for observers in the islands is during the predawn hours of January 3rd, a few hours before peak, the best we have for this year. The good news is that the night will be nearly moonless, with wonderfully dark conditions for observing.

Watching meteors requires no more equipment than your eyes and a dark sky, and can be enjoyable for just about anyone. Set the alarm early?

Comet C/2012 S1 ISON Closest to Earth

Hubble C/2012 S1 ISON
NASA’s Hubble Space Telescope provides a close-up look of Comet ISON (C/2012 S1). Credit:NASA, ESA, J.-Y. Li
Today comet C/2012 S1 ISON will pass closest to Earth. No worries here, close is relative in space and in this case means a comfortable 0.43 AU (64,200,000 km or 39,900,000 miles) from Earth. The comet should be easily visible well up in the dawn sky as an unaided eye object in northern Hercules.

Update: Yes, this post was written and scheduled well before the comet disintegrated at perihelion. If there is anything left it is closest to the Earth today. Many amateurs, large scopes, even Hubble have attempted to recover the remains. No one has reported finding anything.

Winter Solstice

Winter solstice occurs today at 07:11HST. Today the Sun will occupy the most southerly position in the sky of the year. The term solstice comes from the Latin terms Sol (the Sun) and sistere (to stand still). On this day the Sun seems to stand still as it stops moving southwards each day and begins move to the north. This is the first day of winter as marked by many cultures in the northern hemisphere. Alternately, this is the first day of summer for those folks in the southern hemisphere.

2013 Solstices and Equinoxes
  UT HST
Perihelion Jan 2 00:59UT Jan 1 14:59HST
Spring Equinox Mar 20 11:02UT Mar 20 01:02HST
Summer Solstice Jun 21 05:04UT Jun 20 19:04HST
Apehelion Jul 5 18:59UT Jul 5 08:59HST
Fall Equinox Sep 22 20:44UT Sep 22 10:44HST
Winter Solstice Dec 21 17:11UT Dec 21 07:11HST
 
Source: NASA Sky Calendar

 

Comet ISON is Still Dead

The definitive results are in from the Hubble Space Telescope… Comet ISON is still dead.

ISON SOHO LASCO C3
What remains of comet C/2012S1 ISON after perihelion in the SOHO LASCO C3 imagery
On the 18th the Hubble team imaged the expected coordinates of comet C/2012 S1 ISON and found nothing. Given the sensitivities of the instrument and the exposure length, anything brighter than 25th magnitude would have been detected. There was some uncertainty in the position, thus several different locations were imaged with Hubble.

25th magnitude is a lot deeper than amateur attempts at recovery, though the amateur efforts likely covered a great deal more area than Hubble with wider fields of view. Still, there have been no reports of any remains detected by any searcher.

Does this rule out any surviving fragments?

We can’t completely rule out the possibility that something is left of the comet. After all, it was seen after its passage close to the Sun, but disappeared not long after. This material would still exist, but is likely very diffuse gas, dust, and very small pieces spread over an extremely large area. – Zolt Levay, The HubbleSite Blog

I think it is pretty safe to call this comet dead.

Postcard from the Universe – Christmas Tree Cluster

A seasonally appropriate astrophoto, NGC2264, also known as the Christmas Tree Cluster. It does have the outline of a tree decorated with stars in place of ornaments. This was shot on the evening of the 23rd from the driveway.

Keeping the exposures short I concentrated on the stars rather than the nebula that fills the region. I am working on the appearance of my stars, attempting to improve my technique. Not sure if I have succeeded here, they are better. I used some Photoshop tricks to preserve the color of the stars in working on the image. Better, but not quite up the the standard I aspire to.

There seem to be a few deep sky objects that are appropriate for the season. The Rosette Nebula makes a nice wreath, the Christmas Tree, etc. The folks at WISE published a nice infrared image of Barnard 3 that also looks like a wreath. Long winter nights are an excellent time to consider the night sky. Not much else to do, I am on call for the weekend, thus staying home. It is new moon and the recent storms have departed allowing dark skies. May as well take a few more astrophotos.

Mele Kalikimaka!

Christmas Tree Cluster
NGC2264, the Christmas Tree Cluster, a stack of 27 x 1min exposures with the AT6RC and the Canon 20Da

The Rise and Fall of Galactic Cities

JPL Press Release…

In the fable of the town and country mice, the country mouse visits his city-dwelling cousin to discover a world of opulence. In the early cosmos, billions of years ago, galaxies resided in the equivalent of urban or country environments. Those that dwelled in crowded areas called clusters also experienced a kind of opulence, with lots of cold gas, or fuel, for making stars.

Today, however, these galactic metropolises are ghost towns, populated by galaxies that can no longer form stars. How did they get this way and when did the fall of galactic cities occur?

A new study from NASA’s Spitzer Space Telescope finds evidence that these urban galaxies, or those that grew up in clusters, dramatically ceased their star-making ways about 9 billion years ago (our universe is 13.8 billion years old). These galactic metropolises either consumed or lost their fuel. Galaxies in the countryside, by contrast, are still actively forming stars.

“We know the cluster galaxies we see around us today are basically dead, but how did they get that way?” wondered Mark Brodwin of the University of Missouri-Kansas City, lead author of this paper, published in the Astrophysical Journal. “In this study, we addressed this question by observing the last major growth spurt of galaxy clusters, which happened billions of years ago.”

Continue reading “The Rise and Fall of Galactic Cities”