Archive for the ‘Stars’ Category

The Winter Triangles?

Friday, January 21st, 2011

The Summer Triangle is the famous asterism formed by the stars Vega, Deneb and Altair. And while we enjoy it’s sights high overhead on warm summer nights, this time of year we have a double chance to take a look. Thanks to the long winter nights, the Summer Triangle is visible low in the west just after sunset. It’s also visible low in the east just before sunrise. So you can pick your time and enjoy some summer sights in the middle of winter.

Then, for the time in between, there’s the asterism that really is known as the Winter Triangle.  It’s corners are the bright stars Betelgeuse, Sirius and Procyon.  This triangle is visible in the southern sky all through these winter nights.

Gamma Delphini

Monday, July 5th, 2010

There are a lot of good binary pairs out there, and one of the best is in the often overlooked constellation Delphinus.  Gamma Delphini is easily found at the “nose” of this little constellation. It has a magnitude of 4.27 and is about 101 light years away. And it is made up of a yellow-white dwarf star and and orange subgiant. There is speculation that the orange subgiant may harbor a planetary system. So the next time you’re exploring the Summer Triangle, just look a bit to the east for this binary treat.

Red and Blue

Sunday, June 6th, 2010

Tonight the red planet Mars will make a nice pairing with Regulus, the blue-white star that is the brightest in Leo. With Mars currently at magnitude 1.2, it will be similar in brightness to magnitude 1.35 Regulus. While the pairing will be easily visible to the naked eye, a telescopic view will show the color contrast more easily.

Arc to Arcturus

Saturday, April 24th, 2010

Every amateur astronomer (or at least those without GoTo scopes) understands the importance of being familiar with the constellations and bright stars of the night sky. These are the signposts that let us “star-hop” our way to faint fuzzies we’re trying to find. One of the most important signposts, high in the night sky at this time of year, is an orange giant star called Arcturus. With a visual magnitude of −0.05, Arcturs is the brightest star in the constellation Boötes and the third brightest star in the night sky.  Follow the arc of the Big Dipper’s handle toward the south, and bright Arcturus will be quickly found.  Continue following the same arc to the south and you’ll come to Spica, a blue giant, and the brightest star in the constellation Virgo.  This path gives rise to the old saying “Arc to Arcturus, then speed on to Spica.”  If you’re an experienced amateur astronomer, this path is well known.  If you’re just learning, or would like to learn, try to follow the arc tonight and learn two of the main signposts in the night sky.

Are You Sirius?

Saturday, January 2nd, 2010

On these cold winter nights, just a little southeast of Orion, is a dazzlingly bright star – the brightest one in the night sky. Officially called Alpha Canis Majoris (designating it as the brighest star in the constellation Canis Major), it is better known as Sirius or the Dog Star. While the intrinsic luminosity of Sirius is about 25 times that of the sun, much of it’s apparent brightness comes from it’s close proximity to our own solar system. At a distance of 8.6ly, it’s just down the street in interstellar terms.

Although it can’t be seen by the backyard astronomer, Sirius has a small white dwarf compainion star called Sirius B. Due to it’s brightness, Sirius itself often appears to twinkle more than most stars, often flashing a variety of colors. So if you see that bright star in the southern sky this winter, you know it is indeed Sirius.

Bull’s Eye!

Thursday, October 8th, 2009
Head of the Bull

Now that we’ve made the turn from summer to autumn, a familiar array of nighttime sights are returning to view. Two of the most famous are the constellation Orion and the Pleiades star cluster. And right between the two is the almost as famous star Aldebaran. Also known as Alpha Tauri, it is one of the brightest stars in the night sky. In the consteallation Taurus, the brightest stars of the Hyades cluster form a large V shape known as the “head” of the bull. Aldebaran, while not actually part of the Hyades cluster, lies in the same line of sight. With it’s bright red glow, it’s often called the “Bull’s Eye.” While the Hyades is the nearest open cluster to Earth, at a distance of about 151 light years, Aldebaran is even closer. It’s distance of only 65 light years, combined with a luminosity 150 times that of the sun, yields a bright apparent magnitude of 0.85.

The influence of early Arab astronomers is shown in the large number of star names that come from Arabic. The name Aldebaran is taken from the Arabic “al-dabarān” (meaning “the follower”) for the way the star “follows” the Pleiades. However the star was also famous among ancient Persians, Chinese and many others.  And the best part of following in the steps of these ancient astonomers and observing Aldebaran and the Hyades is no equipment is required. Just go outside on an autumn night, face east, and look up. These naked eye sights are a great way to get an easy (and free) introduction to astronomy.

Antares

Sunday, July 19th, 2009

With all the nebulae, galaxies, globular clusters, and other exotic deep space objects available to the amateur astronomer, sometimes the simple things get overlooked. Sometimes even a single star, easilyAntares in Scorpius visible to the naked eye, can have an interesting story to tell. Such is the case with Antares (aka Alpha Scorpii), a red giant star at the heart of the constellation Scorpius. In fact it’s old Arabic name, Ķalb al Άķrab, translates as the “Scorpion’s heart.” However it’s name Antares translates as “rival of Ares”, Ares being the Greek name for Mars. The reason for the name is obvious, seeing it’s similarity in color and brightness to the red planet. But unlike Mars, Antares is roughly 600 light-years away. And that distance is a good thing. If Antares were at the center of our solar system, it’s outer edge would extend beyond the orbit of Mars. But despite it’s immense size, it’s mass is estimated at only 15 to 18 solar masses. And so it has the very low average density typical to red giants.

There are a couple other interesting notes about Antares. For one, it is a variable star whose apparent magnitude varies from 0.9 to 1.8. Also it has a companion star, Antares B, with a magnitude of 5.5. The difference in brightness makes Antares B difficult to observe. But with a good backyard telescope, both stars may be visible. So the next time you’re looking at the night sky, take note of the Scorpion’s heart that has fascinated so many cultures throughout history.

Alberio

Sunday, June 7th, 2009

Many interesting things can be seen through a small telescope, but some are also beautiful. One of my favorites is the double star Alberio. To the naked eye, Alberio looks like a single star at the end of the constellation Cygnus (outlined in red) within the “summer triangle” (outlined in blue.) However even a small telescope can easily resolve it into a double star consisting of Alberio A (yellow colored) and Alberio B (blue-green colored.) This dramatic color contrast contributes greatly to it’s beauty. And it is that beauty, combined with the ease with which it can be found, and the fact it can be seen through any small telescope that makes Alberio an ideal target for beginning stargazers.

Cygnus and the summer triangle

Officially known as Beta Cygni, Alberio is approximately 380 light years from Earth. It is unknown whether Alberio is a true binary system or just two stars in the same area. However in 1976 Alberio A was itself discovered to be a binary star. Unfortunately, resolving Alberio A is well beyond the abilities of the typical backyard telescope.