How Unnaturally Natural

What could be more unnatural looking than this shot of an open cluster of stars, an emission nebula, a reflection nebula, and a dark nebula all interacting in the constellation Sagittarius.

"Whoa, back up a bit," you must be saying. "Emission nebula? What's that?"

In side of that picture of Trifid Nebula, there is a lot going on. This picture by the way was taken in the night sky over Abilene, Texas.

But to answer your question, we should look at each individual thing in this picture.

This is the Rosette Nebula in the constellation Monoceros (mo-nos-er-os). The nebula surrounds a young star cluster. This nebula is emitting its own light, due to the presence of ultraviolet radiation from the very hot young stars that make up the cluster. This radiation, although not visible to the eye, is strong enough to 'excite' the atoms in the interstellar dust and gas so that they 'jump' to different energy levels and emit their own form of radiation which can be seen in the nebula's light spectrum. It is not simply reflecting the light from the cluster.

But a reflection nebula does. Reflection nebulas reflect light from a nearby star. Many small carbon grains in the nebula reflect the light. The blue color typical of reflection nebula is caused by blue light being more efficiently scattered by the carbon dust than red light. The brightness of the nebula is determined by the size and density of the reflecting grains, and by the color and brightness of the neighboring star(s).

Dark nebula, also seen in that first picture. This is a good example of a dark nebula, which is one that is blocking the light from whatever is behind it (which could make a shape - in this case, a horsehead).
You will find these in an emission nebula, which as I should have mentioned is a cloud of a high temperature gas. The atoms that are in the cloud get energized by light from a close star. These types of nebulae are usually red because of the amount of hydrogen.

Hubble is still busy!

I caught a show on PBS the other night that was all about the Hubble repair. It was amazing how many tools they had to invent, how much training went into it (they actually practice in a shuttle sized pool) and how one mistake, like a lost screw would have made the mission all for nothing.



If you are interested - and I sure hope you are, you can watch the whole show here! Get some popcorn and a drink and settle back in your chair. This is amazing stuff!

Saturn animation

It has been awhile since I posted here and I apologize for that. Life interrupts a good deal of my best intentions - as you will find out as you grow up and grow older Junior. I just hope that your interest in the night sky will not wane in the process. Building on what you know at age twelve is a lot easier than trying to build on your knowledge at age 52 - not impossible just harder.

Here is a link to a great Saturn animation I found that might interest you. It was compiled over a six year period.

What We Take for Granted

You have grown up with the internet, making this discussion of the night sky over Bend, your hometown possible from three hours drive away. And you are growing up in a time when what should seem fantastic, just because it was just a few short years ago for people like your Dad and even more so for me, seems almost ordinary.

Today, because I know your night sky will have one too many clouds in it, we will talk about a special space craft visiting place I know I'll never visit - but you might someday! Cassini spacecraft entered orbit around Saturn to begin the first in-depth, up-close study of the ringed planet and its domain (moons and rings and such). It has been in this orbit for over four years and now is doing some additional sightseeing.

This part of the extended mission called the Cassini Equinox Mission.

"We're looking at a string of remarkable discoveries -- about Saturn's magnificent rings, its amazing moons, its dynamic magnetosphere (how it acts like a giant magnet holding the rings and the moons where they are) and about Titan's surface and atmosphere," says Dr. Linda Spilker, deputy project scientist. Can you imagine a job where you get to do this everyday?

Dr Spilker went on to say, "Some of the mission highlights so far include discovering that Titan has Earth-like processes and that the small moon Enceladus (which Cassini flew past at only thirty miles from the surface)has a hot-spot at its southern pole, jets on the surface that spew out ice crystals and evidence of liquid water beneath its surface."

Cassini's observations of Saturn's largest moon, Titan, have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many parallels to Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.

The spray of icy particles from the surface jets collectively forms a towering plume three times taller than the width of Enceladus. It is now thought that the plume feeds particles into Saturn's most expansive ring, the E ring. Already in the extended mission, the spacecraft has come as close as 25 kilometers (15 miles) from the moon's surface.

The extraordinary results from the Cassini spacecraft and the European Space Agency's Huygens probe, which plunged through Titan's dense, smoggy atmosphere to its surface, have generated hundreds of scientific articles and been the subject of special issues of the world’s most important scientific journals.

This picture of Saturn was taken on April 27, 2009 and received on Earth April 28th, 2009. The camera was pointing toward SATURN at approximately 987,316 kilometers away.

The first four years of the Cassini-Huygens saga brought a new dimension of understanding of the complex and diverse Saturn system. The two year Cassini Equinox Mission is expected to be just as exciting. During the extended mission the spacecraft will make 60 additional orbits of Saturn, including 26 flybys of Titan, seven of Enceladus, and one each of Dione, Rhea and Helene. Investigations of Saturn's rings, the planet itself and new places within Saturn's magnetosphere await.

Why is it called Cassini?

A Planetary Flyby

The morning sky this month is spectacular. And I know someone who is up that time on his way to school. And with the switch of daylight savings, it is still dark enough to see these events.

I've talked about Saturn (which you can still see in the evening sky looking east) and Venus (which you can still see looking west at about the same time). I mentioned that we probably wouldn't be here on earth if it were not for Jupiter blocking a lot of space junk that might get hurled into our blue planet.

And if you look southeast in the morning, you can see Jupiter. But here is something else exciting in that early sky: Mercury and Mars.

Mercury is in the southeast when Jupiter is at its brightest. Look just over the horizon and when you find Jupiter, look to the lower left and you should be able to see Mercury. At 51 million miles from Earth, it is the closest planet to the sun.

Even more fun, it is about to be orbited again by Messenger. On its 4.9 billion-mile journey to becoming the first spacecraft to orbit the planet Mercury, MESSENGER has flown by Earth once, Venus twice, and Mercury twice. Still to come is one more flyby of Mercury in late September 2009.

And even though Mercury is really close to the sun, it actually has water ice at the bottom of deep craters where the sun never shines. Mercury looks a lot like the moon but it has no moons of its own. It does have an atmosphere but because it is so close to the sun, the solar winds whip it out into space.

It would be hard to figure out what clothes to bring if you ever went there. The temperatures range from 450 degrees Celsius (840 degrees F) during the day as low as -170 degrees C (-275 degrees F) at night! Hotter than Venus and then colder than cold.

You have to look really close because the sun can be just bright enough to make it hard to see.

Tomorrow: Mars