Looking Up: Aldebaran: This winter’s brightest red star
Red-orange Aldebaran is the brightest star of that color in the winter sky - at least this winter!
In early to mid-evening in late February, you can find Aldebaran by looking south-southwest, to the upper right of the famed constellation Orion.
Aldebaran blazes at about magnitude +0.85, one of the brightest stars of the night sky. Its red-orange hue is unmistakable. Its brightness is only slightly variable.
The star appears at the end of a large pattern of stars shaped like a capital letter “V.” The group of stars makes up a star cluster called the Hyades, the closest star cluster to our solar system. The Hyades, however, is much farther away than Aldebaran; the bright star’s placement is only chance coincidence. The Hyades is 153 light-years away; Aldebaran is 65.23 light-years away.
What’s a light-year? This is the distance light, traveling at about 186,000 miles a second, travels in one year’s time. One light-year is the equivalent of 5.88 trillion miles, a lot farther than your old clunker will ever get, and a number few apart from astronomers and federal budget crunchers can begin to comprehend.
Imagine, the light we see from Aldebaran tonight left the star in 1954. Dwight Eisenhower was president then, and Sen. Joseph McCarthy was hunting for communists.
A red giant star, Aldebaran has a radius 44 times that of the sun. If it replaced the sun, the star would extend almost to the orbit of Mercury.
A planet with a mass several times that of Jupiter is known to circle Aldebaran.
This star is considered the fiery “eye” of the constellation Taurus the Bull. The Hyades are pictured as the Bull’s head.
To the right of the Hyades is the wonderful Pleiades star cluster, much brighter and more compact than the Hyades. This cluster is about 444.2 light-years away. The naked eye typically can see at least six stars. The view is incredible in binoculars.
I’ve been talking a lot about Betelgeuse in recent columns. This famous red star in Orion has made headlines this winter because of an unprecedented dip in brightness. Always slightly variable, Betelgeuse reached a historic low a few months ago and is yet to recover.
Betelgeuse normally ranges from a brilliant magnitude +0.1 to a low of +1.3. In the winter of 2020, Betelgeuse is close to +1.6, or almost second magnitude and similar to the three “Belt” stars in Orion or the brighter stars of the Big Dipper. It was +0.5 only last October.
In fact, it’s 36% dimmer than it looked one year ago.
Astronomers have been debating the cause of Betelgeuse’s dip. It may be that the supergiant star expelled a large amount of dust in our direction, which has helped dim its light, or the star has cooled and contracted.
Betelgeuse is large enough and close enough to show its disc in high-resolution observatory pictures. It is so big, its girth would nearly reach the orbit of Jupiter if it traded places with the sun, engulfing the Earth (please don’t!).
Photos taken of Betelgeuse by the European Southern Observatory’s Very Large Telescope (VLT), taken in December and mid-February, show that the star has become more oblong in shape.
Eventually, Betelgeuse is expected to collapse and suddenly explode as a supernova. It would shine nearly as bright as the full moon, for a few weeks and even be visible in daylight. Astronomers caution that this could happen as late as a few hundred thousand years, or as early as tonight. Its recent dimming is not known to be a precursor or warning sign that it is about to blow to smithereens.
If it does, Betelgeuse will outshine Aldebaran.
Planets: Enjoy brilliant Venus high in the southwest in the evening twilight. About a half-hour before sunrise look southeast from Saturn, the very bright planet Jupiter and reddish Mars, in a line from left to right.
New moon occurs Sunday, Feb. 23. In the week following, watch for the crescent in the evening sky; the moon passes Venus on Feb. 27.
Keep looking up - and up!
Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at firstname.lastname@example.org. Please mention in what newspaper or website you read this column.