June 2003

• The Search Beyond the Solar System
  
  
• Planetary Update
  
  
• Constellation of the Month
  
  
• The Moon
  

The Search Beyond the Solar System

I receive a lot of questions about planets that lie outside of our solar system, so I would like to take this opportunity to discuss the search for the planets beyond!

When we go out on a clear night, and gaze up at the thousands of stars we can see, we can imagine each one of them as a center of a system of planets much like our own. We can dream that the Milky Way is filled with rocky planets with just the right atmosphere that orbit their stars at just the right distance to support life. We can imagine there are other beings that look up to their night sky and wonder if someone is looking back at THEM.

The possibility of a planet outside of our Solar System has been discussed for hundreds of years.

Still, to this day, we have NEVER seen a picture of a planet that orbits another star.

There is a big problem in trying to find these distant planets. We have trouble getting a decent image of the furthest planet in our own Solar System, Pluto (http://www.nasm.edu/ceps/etp/pluto/plutimg/pluto.jpg). The nearest planet beyond our Solar System is TRILLIONS OF MILES beyond that. It seems that finding one of these 'planets beyond' would be an impossible task.

But we are not that easily discouraged! If you go to the PlanetQuest web site, you will see that (at least as of the writing of this newsletter) the "Current Planet Count" is 107. If we've never seen another planet, how can there be over a hundred that we know of?

Well, there are other ways to find a planet besides seeing it first-hand...

You see, gravity is a two-way street. The Earth swings through its orbit because the gravity of the Sun holds us here. But the Earth exerts gravity on the Sun; all the planets do. This causes the sun to have a complex "wobble" as it is tugged in a variety of directions. And each planet tugs a different amount: Jupiter, being so massive, has a much greater impact on the sun than Venus.

If we could detect this "wobble" effect in other stars, we could guess that it was caused by orbiting planets. Once we find the wobble, we have to unravel the complex gyrations to give us an idea of the number, size, and speed of those planets. This takes some very sophisticated mathematics.

Most of the planets we have 'discovered' have simply been inferred from these calculations.

Recently, a new method called the Transit Method has been used to find a few more planets. If a planetary system is lined up to our point of view just right, the planet will pass in front of the star, causing a sort of mini-eclipse of the star -- the star's light will decrease slightly and regularly. We can get an idea of the size of the planet, and how fast it orbits by measuring the amount the light decreases, and how often it occurs.

This is a newer method of finding a planet, but one that even amateur astronomers have begun to use. Backyard stargazers can take digital pictures of the sky, and compare them, night after night to help indicate stars that may be changing in brightness due to a planet's orbit! The Planet Finder Club is a group of folks who are searching the skies for stars which may have planets about them.

We are getting closer to ACTUALLY seeing a planet. NASA is funding the construction of the Large Binocular Telescope (LBT) in Arizona, and its construction has already begun! It will use two lenses and a variety of new technologies to 'blot out' the light from stars, which completely drowns out the planets which may surround them. This telescope is the first one created which was designed mainly to view planets beyond our solar system.

The search for the 'planets beyond' is a very new and emerging science. It is an exciting time in astronomy, as we discover new things, and realize new possibilities every day!

If you are interested in learning more about the methods hinted at in this article, the BEST tutorial on the ways which we are searching for planets is this interactive tutorial.

Planetary Update

It's time to really, officially, say goodbye to Saturn. The trees around my house make it completely invisible as the sun sets. We still have Jupiter to view, and the grand jewel of this summer: Mars!

If you go out at sunset, look to the western part of the sky. The first object you will see is the planet Jupiter. It glitters up there at a brightness that exceeds any of the stars, it is hard to miss. Those of you who have been following the progress of Jupiter this winter know that it has been a glorious sight. It continues to impress those with even small telescopes; the four Galilean moons dance around the giant planet, making for new views every night.

The month of June is really the last we will see Jupiter for a while -- it will be spending some time lost in the glare of the sun. So, take advantage of the warm-weather viewing of Jupiter now.

But, our next-door neighbor Mars will be the highlight of the summer. Anyone owning a telescope should be preparing it for the best views of this planet in our lifetime. Mars rises in the east around midnight, and slightly earlier by the end of the month. Through the month of June, Mars will DOUBLE in brightness, becoming brighter than any star in the night sky. It will be the last nighttime object visible once the sun rises. Look to the southern part of the sky -- the last orangey spot you see is the planet Mars. Mars is small (about 1/2 the diameter of the Earth), and generally you can't resolve any surface features on Mars through the average backyard telescope. By the end of this month you might just be able to see some slight dark and light variations in the color on the surface of Mars. And, over the next few months, they will continue to get easier and easier to see.

This fall, however, our planet leaves Mars behind, ending the last time in our lifetimes that the surface of Mars is easily visible from here on Earth.

If you are lucky, and have few trees surrounding you, you might even be able to spot the two planets which lie closer to the sun than we do – Venus and Mercury are right next to each other very low in the Eastern sky about one half hour before the sun comes up. Venus will be the brighter of the two, but less than one moon-width away will be the dimmer Mercury. Mercury will be easier to spot near the end of the month, as its brightness increases slightly. With a pair of binoculars, you can probably see them both at the same time!

WARNING: These two planets will be right over the sunrise as the sun is coming up – if you do choose to use binoculars, be VERY careful to stop using them before the sun comes up. Even a slight glimpse of the edge of the sun through binoculars can do permanent damage to your eyes. Please use caution.

Constellation of the Month

I have decided to feature The Northern Crown this month -- the glittering curve of jewel-like stars whose official name is: Corona Borealis!

Corona Borealis is right at the zenith, the imaginary 'top of the sky', around midnight this month. It is actually close to Boötes, who was the previous Constellation of the Month. It is a curve of medium-bright stars. This is a little dimmer than some of the other constellations we have looked at, so if you can get yourself to a dark place, it is a little easier to see it.

Corona Borealis

The curve is usually imagined to represent the brim of the crown. In the picture, you will see two stars, in the region of Corona Borealis, but not in the curve itself, which are labeled.

The first I will discuss is the one in the center of the curve, labeled "RCB". This is a star simply called "R Corona Borealis", or RCB for short. It is a very odd one. Sometimes you can see it, sometimes you can't!

This is a very carbon rich star -- its fusion is creating carbon, probably the most important element in living things. (Our sun is mainly made of simple elements -- hydrogen and helium.) This carbon builds up, and then 'poofs' out in a dark cloud of matter. This carbon exhaust covers the star in a haze on an irregular basis, making it nearly impossible to see with the naked eye. For much of the time, it is a 5th magnitude star, a fairly faint one when viewed from an urban area, but certainly visible on a clear night. But when its carbon cloud envelops it, it becomes a 14th magnitude star, far too dim to be seen with the naked eye! This star plays an odd illusion game -- sometimes you see it, sometimes you don't!

The other star, which is marked as "Rho", is a star which ties into the lead article in this newsletter! It is one of the first to have been discovered which we believe to have a planet around it. By studying its "wobble", it appears to have a large planet, about the size of Jupiter, which orbits relatively close to the star (about 1/5 the distance between the Earth and the Sun). Most stars in a constellation are named using Greek letters and the constellation name -- this star's full name is: Rho Coronae Borealis. The Rho star of Corona Borealis is a star about the same size as our sun. It looks a little older and brighter than the sun, but it seems to be quite similar in many aspects -- of all the stars we've found which appear to have planets, Rho Coronae Borealis is the closest match to our own Sun!

So, definitely try to find Corona Borealis! This small constellation is perched at the top of the sky this month -- in it you can find a star which plays peek-a-boo, and a star which might be the center of a system of planets somewhat like our own!

Please feel free to explore some stories and legends about Corona Borealis.

The Moon

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