Eyeing up Stellar Oddballs

Welcome back to What's Up?

Finishing up on a quick overview of stars, this month will be all about the stellar oddballs.

You may remember white dwarfs from last month, but let's take a closer look into these weird stars.

A white dwarf is the core of a star left over from when a star like our sun sheds off its outer layers and dies.  A white dwarf that weighs as much as our sun would be the size of the Earth which makes it so dense that if you were to take a sugar cube sized portion it would weigh as much as a hippo!

Stars that are less massive than the sun will leave behind a white dwarf mostly composed of helium, the second lightest element.

Stars that weigh around the same as our sun will leave behind a core made of heavier elements since they have the mass to fuse the lighter elements into somewhat heavier ones.  White dwarfs left over from these sun-like stars will be composed mainly of carbon (sixth lightest element) with some oxygen (eighth lightest) mixed in.  The intense gravity of these little stars causes the atoms to get squished together very closely.  This creates a crystalline structure of carbon.  We call this carbon structure a diamond.

Don't think about putting one of these suckers on a ring quite yet.  They are extremely hot.  They are a little over 100,000 degrees Celsius and take billions upon billions of years to cool down to reasonable temperatures.  

If a white dwarf star gathers up enough material to increase to over 1.4 times the sun's mass it will completely explode, leaving nothing behind.  If the remnant from a star is over that 1.4 solar mass limit at the time of death in a star, it will collapse down even further than a white dwarf.  The little negative electrons will combine with the positive protons creating neutrons.  All of the neutrons in the star will be squished together very tightly so that if you took a teaspoon of this material it would weigh as much as a mountain!

Astronomers, using the creativity they are well known for, gave these stars made of neutrons this name: neutron stars.

Neutron stars are very bizarre stars.  If they spin fast enough they will create immense magnetic fields which get twisted and occasionally release enormous amounts of energy.  These neutron stars are called Magnetars.

Some neutron stars have jets that shoot high energy particles out of their north and south poles and as they spin around the jets point in different directions just like a lighthouse.  When these cosmic lighthouses are pointing their beams in Earth's direction we see them brighten and they appear to pulse as the beam appears and disappears.  These stars are called Pulsars.

When stars get larger than about 3 or 4 solar masses the neutrons stars will collapse down even further.  This is where we get a black hole.

Black holes are truly the weirdest things that exist in our universe.  According to theoretical models (lots of juicy mathematical equations) they are infinitely dense points of mass.  Anything that falls into a black hole can't escape unless it travels faster than the speed of light, which is impossible according to Einstein's Theory of General Relativity.

If someone were to fall into the black hole they would become "spaghettified".  The gravity at their feet would be pulling on them so much more than on their head that they would get stretched out into a long noodle shape and then get torn apart.  If they were somehow able to survive being torn apart they would experience a very interesting effect.

According to Einstein's theory of General Relativity, gravity slows down time.  A clock on Earth actually ticks very slightly slower than it would if it were in space.  This has been tested very accurately with satellites.  If there was someone falling into a black hole and they were sending a signal back to us every second we would see this poor bloke's signal separated by longer and longer time spans.  One second between signals... two seconds between... 3... 4...5... and so on until they were spaced by apart by very large amounts of time and the person just faded away and the signals wouldn't get received anymore.

Before time nearly comes to a stop lets see what's up in this month's sky.

Mercury is at greatest eastern elongation on Sept. 11 which means the best time to observe Mercury would be a few days around that date.

Mars and Venus are also in the western horizon this month.  They will be less than a hand width held at arm's length above Mercury in the sky.

On Sept. 15 will be the full moon and on Sept. 29 will be a new moon.

Finally, on Sept. 22 is the Autumnal Equinox, the first day of fall.

Until next month just look up!

Hey Kids...
Remember about the Phoenix mars lander?  It landed on Mars a little more than three months ago and has been digging around in the dirt to see what's in the soil.  It dug down a few inches and hit ice.  Looking at the ice scientists on Earth found out that the ice used to be liquid.  This means tons of liquid water used to be on Mars!  Sadly, it has gotten so cold that all water has since frozen.  Temperatures on Mars where the Phoenix lander is can dip lower than -80 degrees Celsius!  Hopefully the lander brought a winter coat!

Send your name into space aboard NASA's Kepler mission

NASA's Kepler mission (shown in image at left) is offering the chance for anyone who wishes to send their name into space in a mini-DVD that will be attached to this spacecraft. Kepler will orbit the sun instead of the Earth so that it can constantly monitor the stars in a small patch of the sky about the size of a human hand held at arm's length.

To send your name and an answer to the question (optional) "Why do you think the Kepler Mission is important?" (500 words or less) just go to http://namesinspace.seti.org/ . Once you've submitted your name you have to choice to save or print off a certificate to prove your name will be in space (to save: File->Save As… from your browser).

This mission will launch sometime in 2009 and is the first mission capable of detecting Earth-size and smaller objects. This is when your name will be shot into space and will drift in space among the planets...

Name in Space is in celebration of the International Year of Astronomy in 2009. 2009 is the 400th anniversary of Kepler's publication of Kepler's first two laws of planetary motion. A copy of the mini-DVD with all of the names and messages will be given to the Smithsonian Institution’s National Air and Space Museum.

Phoenix Mars Weather Summary for Sols 1 to 63

Over 63 Sols (martian days) the Martian weather has changed slightly. Here is a quick summary from data taken from NASA's Phoenix Mars Lander for its days spent on Mars.

The temperature increased by about 4°C with an average max temperature of -30°C and an average low of -79°C. The winds were southerly during the day and easterly at night. The average wind speed over the 63 Sols of wind measurements was 14.4 km/h.

The atmosphere varied from clear to clear with dust haze and the atmospheric pressure steadily decreased from 8.5 to 7.85 millibars over the 63 Sol period.

Here's a graph of this summary over this 63 Sol period (click image for a larger view):

reevesAstronomy

Laptop idea revisions

Looking at my cash in hand I'm thinking just a simple white MacBook (why does the black version have to cost an extra 100 bucks?!?) will be better choice than the MacBook Pro. I'll still be getting similar specs on it (smaller screen and one less USB port - sigh...). Thinking logically, I'm going to wait until apple updates their line of computers, which should be happening in a month or two.


My laptop will run on an Intel Core 2 Duo processor running at 2.4Ghz or more (depends on price at the time of purchase), will have 4 GB of RAM (600mhz or faster), a graphics processor (cheap ol' apple can't even give you a graphics card...tsk, tsk). It will have a 13 inch monitor, a full keyboard, trackpad, Wi-Fi, etc. For more details check out: http://www.apple.com/macbook/


Tech Specs at a glance:

• 2.4GHz Intel Core 2 Duo
• 4GB 667MHz DDR2 SDRAM - 2x2GB
• 160GB Serial ATA Drive @ 5400 rpm
• SuperDrive 8x (DVD±R DL/DVD±RW/CD-RW)
• None
• None
• None
• None
• None
• None
• None
• Keyboard (English) / User's Guide
• 13" High Gloss Screen
  

I will have Mac OS X Leopard (10.5) with Linux (PCLinux or Ubuntu) and Windows Vista as alternative boot options (see my last laptop update to see more about my planned OS's) for when I need them. I also plan on getting a cheap ( possibly a few hundred dollars) CCD for imaging with my telescope.

That's all my laptop ideas for now, I'll make sure to keep you posted.

reevesAstronomy

Phoenix Confirms Presence of Water and Finds "Toxic" Substance in Martian Soil

NASA's Phoenix lander found an unexpected "toxic" substance while analyzing icy soil samples taken near Mars' north pole. This announcement comes just after the announcement confirming water (in ice form) exists on Mars.

The scientists working with the Phoenix mission made the two finds after analyzing the data from the Thermal and Evolved Gas Analyzer which can heat samples up to 1800 degrees Fahrenheit. Phoenix then "sniffs" the gasses given off to see what the sample is composed of.

In this case, a soil sample containing scrapings of ice (sampling area shown in above image) were heated and tested to see what the sample contained. Water was found in large amounts indicating the the hard white substance they sampled was in fact water ice. They also made the surprising find of Perchlorate.

The highly reactive salt called Perchlorate in the soil was thought to have possibly been from the rocket fuel used by Phoenix to land on the surface of Mars. But it turns out that this is not contamination since Phoenix's rockets used hydrazine not chlorine as a fuel.

Perchlorate is toxic enough that it could prevent any life from living. Other scientists believe it would have a positive effect for life and could be used as a possible energy source.

Life - and Death - Among the Stars

Welcome back to What's Up?

Continuing from last month's topic of dwarf stars we'll look at the other end of the stellar spectrum, the giant stars.

Sometime, around four or five billion years from now our sun will start to expand becoming larger and larger until it is about the size of Earth's orbit to become a red giant. There happens to be one problem for Earth here, the orbit of the Earth will be inside the sun which means the Earth will completely melt and disintegrate, mixing into the sun.

By this time the sun will have changed to a red colour due to a lower surface temperature.

The sun will run out of hydrogen fuel and will start fusing helium for a few million years. Then it will start burning heavier and heavier elements like carbon and oxygen until it starts burning iron. In order to fuse iron more energy is needed to fuse it than the fusing process creates.

Once the sun is fusing iron it will no longer produce enough energy to keep it from contracting under its own gravity it will begin pulsating and shedding off its outer layers. Eventually, all that will be left is the core of the sun: a small dense white dwarf that may weigh half as much as the sun's original mass, yet be as small as the size of the Earth!

Larger stars live much different lives than the small yellow dwarf star we orbit around that we call the sun.Large stars live much faster paced lives. These giant stars are up to a thousand times brighter and have diameters 10 to 100 times that of the sun. Since they're so large their insides are extremely hot and this causes these stars to burn their hydrogen fuel extremely quickly.

Most stars smaller than 8 solar masses will live a few hundred million years or longer. These smaller stars will have a much longer life. Nearing the end these smaller stars' lives they will expand into a red giant star and shed off its layers just like the sun will. Stars larger than this most likely will expand to even bigger diameters and possibly become a red or blue supergiant, depending on how hot it is. These stars that are larger than 8 solar masses have life expectancies of only a few tens of millions of years.

When you look up into the night sky, many of the bright stars you see are actually giant stars.

Stars that are dozens of times the sun's mass are usually called supergiant or hypergiants depending on their physical size and luminosity. They usually are twenty to several hundred times the sun's diameter and have 10,000 to 100,000 solar luminosities. Supergiants only last a few million years or so before they explode in a supernova, an explosion where the core of the star collapses and then the star explodes leaving behind either a small, dense star called a neutron star (just a few miles across but with as much mass as two or three suns, one teaspoonful of this star would have as much mass as a mountain) or a black hole (very small dense object with gravity so strong that light can't even escape).

Finally, hypergiants, the largest of all stars, are constantly on the verge of instability since they weigh in at over 100 solar masses. They only last a few hundred thousand up to a few million years. Since they last such a short period of time they are very rare. Only about a dozen are known to exist in our galaxy.

One of the better known hypergiants is Eta Carinae. In the 1800's it was the second brightest star in the sky. But it dimmed quickly out of sight. It's now only visible with the aid of a telescope. This star could explode at any time since it is so unstable.

Since it is in the southern hemisphere's sky, most people in the northern hemisphere won't get to see it explode even if it does so within our lifetimes, so let's check out the northern sky for this month.

On Aug. 1 there was a new moon. There was a total solar eclipse visible from northern Canada and Greenland that day. Only a partial solar eclipse was visible to Islanders if they got up early enough in the morning. Don't forget to wear eye protection such as welder's goggles or use a pinhole camera (check "Hey Kids" section) if you ever plan to observe the sun.

Two weeks later on Aug. 16 there will be a full moon and this will also be a partial lunar eclipse. Don't get too excited though, the moon will barely be in the Earth's shadow so not much difference may be noticed.

Finally, on Aug. 30, there will be a new moon, the last of the summer.

Until next month, just look up!

Hey Kids...

If you want to view the sun safely without fancy goggles during solar eclipses you can make what's called a pinhole camera. All you need are two pieces of cardboard and one needle. You poke the needle through the center of the first piece of cardboard making sure that the hole isn't too big and that it's nice and round. That's all there is to making it! To use it all you have to do is face away from the sun while holding one piece of cardboard a few inches or so apart (you may want to experiment a little bit) from the first piece of cardboard the closest to the sun. You will see a little image of the sun projected on the second piece of cardboard. And there you go! If you really like to experiment you can use a cheese grater to project many little images of the sun onto a piece of cardboard or paper. Now you know how to view the next solar eclipse!

reevesAstronomy

Dwarfs Hiding in the Sky

Welcome back to What's Up?

Last month the Phoenix Mars Lander found water ice on Mars. This is the first time that any form of water has been observed directly on the surface of Mars up close. As of writing this the Lander has just found that the soil is not toxic in any way and that it is similar to soil that would be found in a garden (minus the organic substances). It also found the soil is somewhat salty, not acidic, and has interacted with liquid water at some point in its past.

Looking at the sky, Mars is barely above the western horizon at the start of this month, and it will be sinking even lower along with Spring's constellations. Let's look at the stars within these constellations. More specifically, let's look at the hidden stars that actually make up the vast majority of stars in our galaxy.

The stars being referred to are called red dwarfs and brown dwarfs. And yes, they are very small stars like their name suggests. Let's look at the red dwarf stars first.

Red dwarfs are the most common type of star that we know of by far. Out of the nearest thirty stars to our sun, twenty-one of them are red dwarfs!These small stars are less than one half of our sun's mass (our sun is called a yellow dwarf) but more than 0.08 solar masses (80 Jupiter masses). Any objects smaller than this are called brown dwarfs.

Since red dwarfs are so small they don't give off very much light - the smallest of these stars give off 10,000 times less light than the sun!Considering their minute size, most people would think at first thought that these little stars would burn out quickly since they have less fuel (hydrogen).

In reality, they actually burn their supply of hydrogen so slow that they can keep burning for over a trillion years! Normal stars can only burn for billions of years and the largest of stars may only last a few million!Even smaller than the dim little red dwarfs are the brown dwarfs. These are the smallest and dimmest type of star. They mainly give off infrared light so they can only be seen with special telescopes.

It is difficult to tell where the dividing line can be drawn as to what is a planet and what is a brown dwarf. It's usually somewhere around 0.013 solar masses (about 13 Jupiter masses).The main difference between planets and brown dwarfs is how they form. Brown dwarfs form in the same way as regular stars, in a collapsing cloud of dust and gas with them at the center. Planets form when that cloud of dust and gas collapses into a rotating pancake shape and the planets form within this disk around the star at the center.

Brown dwarfs generate light and heat in two ways: deuterium (heavy form of hydrogen) fusion and through the slow contraction of all the material within these objects due to their gravity trying to pull everything inwards. Their deuterium supply usually runs out after ten million years and the gravitational contraction mainly creates heat so it can be nearly impossible to see these objects against the darkness of space.

The first brown dwarf was discovered in 1995 and is called Gliese 229B. Many others have been discovered since.

Since these are so difficult to see and detect, let's look for something which we can see with a little more ease.

This month there was a full moon on July 3rd and the moon will reach its full phase by the 18th.Jupiter is at opposition on July 9th. This would be the best time to view or photograph the planet since this is when the planet is closest to the Earth for this year, but Jupiter is favoring the southern latitudes this year so we won't get a good view since it's low on the horizon. By naked eye, it will be a fine sight. Just look towards the Southern sky this month. It will be by far the brightest object in the sky.

Until next month, just look up!

Hey Kids...
If you can't get out to see the skies due to those annoying clouds, you can explore the sky on the web at www.google.com/sky . Click and drag around to move around, double-click to zoom or use the middle scroll wheel on your mouse. There are buttons at the bottom to help you find certain objects like planets, constellations, or images taken by the famous Hubble space telescope. Also, at the top left hand corner of the page are three links: Sky, Moon, and Mars. Click on "Moon" to view the Moon or click on "Mars" to view Mars in high detail. Don't forget about the search box at the top, it can really be a help. Enjoy!

reevesAstronomy