Sunday, May 11, 2008

Galaxies, Dwarfs, and Hobbits

Welcome back to What's Up?

Now that Spring has finally arrived it will be easier to spend more time outside to take a peek at the sky and see what's up.

Continuing on the theme of galaxies from last month, I'll be talking about the small, unnoticed galaxies; the Dwarf Galaxies.

It may be very surprising to find that galaxies like ours containing billions of stars that appear in the majority of space images and attract most of the attention are outnumbered by up to ten times as many dwarf galaxies!

For example, in our own local group of galaxies, there are forty-five galaxies total. Out of those forty-five galaxies only five aren't dwarf galaxies!

Dwarf galaxies are simply just small galaxies containing only millions of stars instead of billions that are somewhere in between globular clusters(hundreds of thousands of stars clumped together) and galaxies like ours and the Andromeda galaxy in size.

Omega Centauri is now being considered as a dwarf galaxy instead of a globular cluster due to its enormous size compared with other globular clusters. It even has a black hole that weighs millions of times as much as our own sun!

Very recently astronomers have coined the term, "Hobbit Galaxy", to any galaxy smaller than a dwarf galaxy. These galaxies are hardly a mist of stars, dust, and dark matter - a substance that can be observed only by its gravitational effect - mixed together. Seeing them is like reading white text on a white background.

There are two main types of dwarfs, irregular and elliptical. Irregular galaxies have no particular shape or pattern and elliptical galaxies are elliptical(oval) in shape. Also, there is another type, which is very rare, the spiral dwarf galaxy.

Another interesting type of dwarf galaxy are the extremely low surface brightness galaxies. These galaxies are so dim that only recently with ultra powerful telescopes and sophisticated computer processing have astronomers been able to pull them out of the darkness.

Also being pulled out of the darkness are dwarfs that are interacting with our galaxy that we've never seen before. Some of these galaxies are essentially being ripped apart by gravitational forces within our galaxy. These galaxies get ripped into streams and are stretched into a long ribbon which wraps around our own Milky Way. This ribbon eventually dissolves into our galaxy. That's why it is so difficult to detect them; these little galaxies' stars are commingled with our galaxies stars making them hard to tell apart.

Some astronomers believe that dwarf galaxies play a large role in large galaxy formation. They believe our galaxy and many other galaxies formed as a result as many of these minute galaxies merging together to form larger and larger galaxies.

Eventually you would end up with a galaxy about as large as ours after these many mergers and after a great amount of time spinning a spiral shape shows up just like a spiraling vortex shows up when you pull the plug out of a bath tub. After all this mixing and mashing we end up with our beautiful Milky Way galaxy where we have been born since. Now that we're here we might as well examine the sky for a few events that are going on in our wonderful sky.

The moon this month will be new on May 5th and this month you can attempt to see opposite crescent moons on consecutive days. On May 4th, 35 minutes before sunrise look to the East-North-East with binoculars and you should be able to spot it. Watch out for the rising sun! On the next day, May 5th, look around very close to the horizon in the West-North-West about 30 minutes after sunset with binoculars. The moon will appear as an extremely faint and a very thin sliver. This will be a terribly difficult hunt, so if you don't quite find the moon on the 5th don't worry!

The moon will be full by May 19th and will be the farthest full moon from earth this year. This means that the moon may appear smaller in the sky than usual. It is also what is called a "Blue Moon"(third full moon in a season). The next blue moon will be November 21st, 2010.

Also Mercury will pop in and will be best viewed within a few days of May 10th.

A few markable notes things to be noted from NASA: on May 25th the Phoenix Mars lander will land on Mars to drill into the soil and measure atmospheric conditions. On May 30th will be the launch of the Space Shuttle mission STS-124 and will deliver the final parts for the Japanese Kibo Module for the International Space Station.

On the last Sunday of this month, as usual, is the Athena Community Astronomy Club's monthly meeting.

Until next month, just look up!

Hey Kids...
Astronomers and engineers are working on a solar sail. This solar sail will act just like a sail on a boat to propel a spacecraft forward except for one difference: it will use the solar wind instead of wind here on earth. This solar sail may be put a little spacecraft which will use the solar wind to glide quickly outside the solar system to see what space is like out there. Who knows? Maybe in the future people will use these solar sails to glide out into the outer solar system away from earth to settle on other planets. Those people may even be you!


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