Looking for the “big dog”
By Vernon Whetstone
The next two objects on our easy-to-find list are the “Belt of Orion,” and the brightest star in the night sky, Sirius.
By now we should all be familiar with the hourglass shape of our old friend Orion with the three stars across the middle for a belt and the three objects that look like stars hanging down from it like a sword.
He can be located very high in the southeastern sky about an hour after local sunset.
The stars are, from left to right, Alnitak, Alnilam, and Mintaka. All three names are derived from Arabic with reference to a belt of some type.
All three are of similar brightness with Alnitak being the brightest, and although they all look similar and close to each other they are really not.
Alnitak is the closest at (depending on which source you use) 826 light years away. Alnilam is next closest at 919 light years, and Alnilam is the furthest at 1,359 light years distant.
Aside from holding up Orion’s pants, the three stars are quite useful as a help in locating two other astronomical objects.
If you draw a line from left to right along the length of the belt and extend the line further you will find another of our old friends, Aldebaran, the eye of Taurus, the Bull and the Hyades star cluster. If you continue to extend the line you will arrive at the Pleiades star cluster.
Now, if you draw a line from right to left and extend the line we will wind up at Sirius, the brightest star in the night sky and the subject of our next easy object to locate.
Sirius is also called the “Dog Star” since it is the brightest star in the constellation, Canis Major, or the Big Dog.
It is a fun star to observe when it is low on the horizon after rising, especially when viewed through binoculars.
Since it is low, the light from the star has to travel through the thickest part of Earth’s atmosphere which causes the star to twinkle furiously sparkling with many colors.
The star has a magnitude of about 1.5 and is at a distance of almost nine light years.
Sirius is also associated with the so-called “Dog Days of Summer.” That is the time when Sirius is rising at about the same time and direction as the Sun. The Greeks thought that since Sirius is so bright it must be adding heat to the Sun’s heat making it hotter.
This was also the time when the Nile river in Egypt would flood bringing needed nutrients to the fields.
SKY WATCH: New moon, Sunday, Feb. 10. Starting tonight, Feb. 6, and for the next three nights it could be possible to see three planets in the same binocular field of view.
I say “could be” because they will be visible about a half-hour after sunset when the sky is still awash in the Sun’s afterglow, and they will be very, very low on the western horizon so a clear, non-obstructed horizon is necessary. Binoculars will also be required, just be sure the Sun is out of the sky before you use them.
The planets are Mars, Mercury, and Neptune. If you can find them, watch how they change places each night. Mercury will be at its highest and best for viewing on Feb. 16.
NEXT WEEK: The last two quick-view objects, a quick lesson about comets and more astronomical blathering.