What’s Up in the Sky – September, 2010
By Peter Burkey

September often has cool, clear nights that beckon us out for some stargazing. An interesting and often overlooked category of observing targets is binary, or double stars.

Double stars come in many styles, sizes, and colors. Most are pairs of stars that are gravitationally bound to each other just like Earth and the Sun are and therefore actually orbit each other. Others, called optical doubles, are just two stars that appear close in the sky, but one is lots farther away and they are not gravitationally bound.

Some double stars can be seen with the naked eye. The next time you see the Big Dipper, look closely at the middle star in the handle. You should notice a faint “companion” star right above the brighter primary star. The brighter one is Mizar and the companion is Alcor and they form an optical double. What is more interesting, though, is that if you look at Mizar through a telescope you will see that it is actually two stars, a true binary system. In 1650, Mizar became the first star known to be a binary.

Some binary systems are fairly exotic, especially when one of the companions is much more massive than the other. The heavier one evolves faster and sometimes becomes an invisible white dwarf orbiting a giant blue or red star. Sirius is an example. The intense gravity from the denser dwarf star attracts material from the companion causing the dwarf’s mass to increase. Eventually it reaches a limit, collapses, and explodes (called a Type 1 Supernova).

Even more bizarre stuff happens if the binary system is composed of really massive things like two pulsars. A pulsar is a rapidly spinning neutron star that emits a very precise radio signal that can be used to precisely measure its orbit. A pulsar is so massive it actually warps spacetime which affects the radio signal we receive. The study of such systems may reveal some of the secrets of General Relativity.

For more tips on double stars and the rest of what’s up in the sky, go to:
http://www.skyandtelescope.com/observing/objects/doublestars

This month in history:
Sept. 3: Last two lunar landings canceled by NASA – 1970
Sept. 8: Voyager 1 launched – 1977
Sept. 17: First powered flight of X-15 rocket plane – 1959
Sept. 21: Second flyby of Mercury by Mariner 10 – 1974
Sept. 26: Israel launches its first satellite – 1988
Sept. 30: End of daily communication with Pioneer 11 – 1995

Here are this month’s viewing highlights:
Planets this month: Venus continues to dominate the western horizon at dusk. Look for the crescent Moon to the planet’s lower right on the 10th and upper left on the 11th. Jupiter rises just after sunset and is visible in the SE before midnight.
Sept. 1: Last-quarter Moon
Sept. 8: New Moon.
Sept. 10-11: Look low in WSW starting at 8:30p.m. for crescent Moon and Venus.
Sept. 15: First quarter Moon
Sept. 22: Autumnal equinox – first day of fall in Northern Hemisphere.
Sept. 30: Last-quarter Moon

What’s Up in the Sky – August, 2010
By Peter Burkey

My observing pick of the month for August is the gathering of planets above the western horizon after sunset. Venus continues to outshine everything else (except the Moon, of course) with Mars and Saturn to its upper left on August 1. Watch the triangle formed by these three planets shift and change shape during the first week of the month. They are most tightly gathered on the 7th when they all will lie within a circle whose diameter is less than half the width of your fist held out at arm’s length.

The three are joined by a crescent Moon on August 12. The previous night, one half hour after sunset, a very thin lunar crescent lies just above the horizon with Mercury immediately above it. Both will be difficult to see even with binoculars or a small telescope due to the bright twilight glow, but it’s worth a try.

As the month progresses, the three sink lower and their separation increases. But, from August 29th through September 3rd Venus and Mars are joined by the star Spica with Venus passing closest to the star on the 31st.

A close second in this month’s observing picks is the Perseid meteor shower. It is expected to peak on the night of August 11-12. The shower occurs because Earth, in its swift journey around the Sun, passes through a cloud of tiny debris left over from Comet Swift-Tuttle. As our atmosphere encounters these particles they burn up, heating the surrounding air and making it glow. The result is a short-lived streak of light.

The best way to observe the meteor shower is to find a dark spot with a clear view of the sky, climb into a sleeping bag or wrap up in a blanket and sit back in a reclining chair. No special equipment is needed, just the naked eye. Look up at the darkest part of the sky and be patient. Under ideal conditions you may see up to 100 meteors per hour but, realistically, if you stay out for several hours, you are likely to see something like 40 or 50. And don’t forget the mosquito repellant. This year there will be no Moon to wash things out so you should have a good view of what’s up in the sky.

This month in history:
August 2: First televised liftoff of lunar module – Apollo 15’s “Falcon” – 1971
August 6: Gherman Titov first person to sleep in space aboard Vostok 2 – 1961
August 12: Mars Reconnaissance Orbiter launched – 2005
August 19: Milton Humason born – 1891
August 22: Luna 24 returns soil samples from Moon – 1976
August 25: Spitzer Space Telescope launched – 2003

Here are this month’s viewing highlights:
Planets this month: Mercury, Venus, Saturn, and Mars gather above western horizon 50 minutes after sunset as August begins. Watch each night to see changing alignments. Jupiter rises due east more than two hours after sunset, earlier as month progresses.

August 3: Last-quarter Moon
August 9: New Moon.
August 11-12: Perseid meteor shower.
August 16: First quarter Moon.
August 24: Full Moon.

What’s Up in the Sky – July, 2010
By Peter Burkey

The summertime has its pluses and minuses when it comes to observing the sky. On the plus side are vacations, warm weather and clear nights. On the minus side are mosquitoes, dew, and the fact that it does not get dark until after ten o’clock.

But the good news is that this is one of the best times of the year to view the Milky Way, our home galaxy. Look toward the southern horizon on a dark night at this time of year and you should see a band of light rising up from the horizon, extending overhead, and continuing to the northern horizon. Some mistake it for a band of clouds, but, upon close examination, it is actually a dense concentration of stars. It’s as though we were imbedded inside a blueberry pancake: as we look toward the edge of the pancake, we see lots of blueberries.

But to get a sense of the vastness of our galaxy we need to think in terms of a scale model. If we were to shrink our galaxy by a factor of one billion, the Earth would be the size of a grape, the Sun would be almost five feet in diameter and the most distant planets would be about three miles away. But the nearest stars would still be tens of thousands of miles away, making our model rather too large to visualize.

If we shrink our model down by another factor of a thousand, so that all dimensions are reduced by one trillion, the Sun would be about the size of a mustard seed, and the entire solar system would fit inside a closet. But the nearest star is still on the other side of town, about six miles away.

The space between the stars is extraordinarily empty. Separations between individual stars amount to over a million times their diameters. The stars in our model are like mustard seeds scattered many miles apart. So, when you look at the Milky Way, keep in mind that the stellar universe is a big place, and it is a wonderful accomplishment that, by analyzing the feeble light we collect with our astronomical telescopes, we are able to learn so much about what’s up in the sky.

This month in history:
July 1: Mt Wilson observatory receives 100 in. mirror – 1917
July 4: Supernova, whose remnant is known as the Crab Nebula, is witnessed – 1054
July 6: Newton’s book, Principia is published – 1687
July 11: Skylab reenters atmosphere – 1979
July 20: Humans walk on Moon for the first time – 1969
July 24: First rocket launched from Cape Canaveral – 1950

Here are this month’s viewing highlights:
Planets this month: Venus now getting lower in the west at dusk. Watch nightly as Venus is joined by Mars and Saturn at month’s end. Look for Mercury lower right of planets July 30. Jupiter rises after midnight for most of the month and is high in the SE at dawn.

July 1: Venus, Regulus, Mars, and Saturn in line in west at sunset.
July 4: Last-quarter Moon
July 11: New Moon. Solar eclipse in South Pacific.
July 15: Look for crescent Moon below Mars and Saturn.
July 18: First quarter Moon.
July 25: Full Moon.

“We are a way for the Cosmos to know itself.” – Carl Sagan