Comets, Ancient Galaxies And The Dark Ages

I see by the International Meteor Organization’s (IMO) quicklook data that Orionid meteor shower activity started picking up around 10 p.m. last night to 35 meteors per hour as viewed from a dark sky with the radiant point high overhead. I hope some of you were able to check it out. Tomorrow I’ll have a more complete summary on how the shower came down.

A small sungrazing comet heads almost straight for the sun in this photo taken with the coronagraph on the SOHO space observatory at 3 a.m. Central time this morning. The coronagraph is a metal disk (larger circle) that blocks the sun's glare. The sun is represented by the white circle at center, while the white rays form part of the sun's corona or atmosphere. Credit: NASA/ESA

We know that the Orionids originate in Halley’s Comet. It’s interesting that on October 19 a small comet was discovered by Japanese comet observer Bo Zhou in images taken by the Solar and Heliospheric (SOHO) spacecraft. This one was headed straight for the sun and quickly brightened to 1st magnitude – as bright as Deneb or Altair in the Summer Triangle. Lost in the solar glare in earthbound telescopes, the comet wasn’t a problem for the spacecraft’s coronagraph, which can block the sun from view and see objects very near its edge from the airless vacuum of outer space. See a video of the comet’s progress HERE.

Comet Ikeya-Seki was a sungrazer similar to today's comet discovered by Bo Jhou. Credit: Credit: Roger Lynds/NOAO/AURA/NSF

It’s unlikely the comet survived its close solar passage. I’ve checked later photos from SOHO and it appears the little guy didn’t make it out the other side. If it does somehow miraculously survive the sun’s intense heat without breaking to pieces, it could emerge as a relatively bright comet in the evening sky.

Sungrazing comets are almost all pieces of a once-larger comet that broke up long ago. One of the finest of the group was Comet Ikeya-Seki, which put on an incredible show in October 1965 when it passed only 280,000 miles from the sun’s surface. The comet not only survived but became so bright it was clearly visible to the naked eye in the daytime sky next to the sun. I was just beginning to notice the night sky around that time and got word of the comet from the newspapers. One morning, I stood vigilantly by the front room window waiting and waiting before dawn for the sky to clear to get a look. I never did see it that morning or any other. Oh well, it was only one of the brightest comets in the last 1000 years!

European astronomers announced Wednesday that the galaxy at center, named UDFy-38135539, is the oldest seen in the universe so far. They focused a large telescope in Chile to look for unique light signatures that indicated its age. (NASA/ESA)

If you haven’t heard the news, a new, farthest-ever galaxy was found in a long time-exposure photograph made by the Hubble Space Telescope. European astronomers determined the galaxy was from 13.1 billion years ago, when the universe was only 600 million years old. While that’s ancient from a human perspective, it’s only the toddler stage for something as old as the cosmos. We see the galaxy in its early youth when its stars were first forming. Since then it’s evolved into a different form or perhaps even merged with other galaxies to form a larger one.

Astronomers at the European Southern Observatory (ESO) used their Very Large Telescope (VLT), comprised of four identical 323-inch telescopes,  to determine the object’s red shift or how fast it’s being carried away from Earth by the expanding fabric of the universe. Like the pitch change you hear in a train whistle when it trails off in the distance, light from faraway objects shifts to the red end of the spectrum as the ever-expanding universe carries them to greater and greater distances.

A simulation of the "reionization era" when the universe was transitioning from dark, cool gas to one lit up by starlight. This epoch in the universe’s early history lasted from about 150 million to 800 million years after the Big Bang. In this visualization, ionized regions are blue and translucent and neutral regions are dark and opaque. Credit: ESO/M. Alvarez, R. Kaehler and T. Abel

The galaxy is so dim and remote, they had to observe it for 16 hours and then analyze the data for two months to spy the very faint glow of hydrogen gas at a redshift of 8.6. That translates to a time when the universe was so young, it was still partially obscured in a cosmic fog of neutral hydrogen. Astronomers call this time the Dark Ages, because there were no luminous objects in the cool, dark gas. No stars had fired up to light the darkness of outer space. Once some of the gas condensed into stars and postulated black holes, their light energized the hydrogen, splitting it into individual protons and electrons during the “reionization era”. This ancient galaxy was one of the first to clear the fog that led to the universe we see around us today. Read more HERE.