Skies Over Crestone: March 2020

The Crestone Eagle • March, 2020

by Kim Malville

March 1: Venus, bright and un-twinkling, continues to dominate the evening sky this month.

March 8: Daylight savings starts

March 11: During the next two weeks in the dark skies of Crestone you should be able to see the Zodiacal light, stretching upward from the western horizon in a hazy pyramid of light.  It will pass upward through Taurus into Gemini, tilted slightly to the left.  Because it will be nearly perpendicular to the Milky Way you can distinguish one from the other. The Zodiacal light is produced by sunlight reflected from dust particles lying in the plane of the planets. The particles are produced by collisions between asteroids. The dust gradually spirals into the sun and is renewed by more collisions.

March 19: Spring Equinox occurs when the sun crosses the celestial equator at 9:50pm MDT.

March 24: Venus reaches its greatest distance east of the sun, attaining its greatest height above the western horizon. It will remain visible for more than 4 hours after sunset.

March 28: The youthful crescent moon forms a triangle with Venus and the Pleiades, best viewed about one hour after sunset.

Constellation of the month: Orion

You all probably can identify Orion with its bright red star, Betelgeuse on his shoulder, bright blue star Rigel on his lower leg, and the three stars of his belt. Orion was what the Greeks called a demigod, a son of Poseidon (or Neptune for the Romans), the god of the sea. As such he could walk on water. He became a skilled hunter with the bow, and boasted about it. He boasted too much, claiming he would be able to slay every animal on earth. Gaia, the goddess of Earth, was alarmed by such hubris and sent a scorpion, which stung his heel and killed him. Both were placed in the heavens at opposite sides of the cosmos: Orion dominates the winter sky and Scorpio dominates the summer sky.

Orion has enough stars to guide the viewer beyond him. The three stars of his belt lead downward to Sirius, the Dog Star, the brightest star in our sky, and upward to Aldebaran, the blood-shot eye of Taurus the Bull.  Rigel and Betelgeuse lead upward to Gemini the twins, Castor and Pollux.  Betelgeuse joins with Bellatrix to point to Procyon, the Little Dog. Sirius, Procyon, and Betelgeuse form the Winter Triangle of bright stars.

Star of the month: Betelgeuse

Betelgeuse has come into prominence the past few months by a strange infection of fading. It is a fabulous star, very red, very big, and bright. It has been the eleventh brightest star in the night sky, but it faded to become the 23rd brightest at the end of 2019. Some lovers of cosmic catastrophes have suggested that this unusual behavior may mean it will become a supernova explosion that will be spectacularly visible from Earth, possibly outshining the Earth’s moon and becoming visible during the day. Wow, that would be great!  But, like the prediction of the death of Mark Twain, its demise as a supernova appears to be exaggerated.

Orion’s guide to the sky and the winter triangle.

Comparing the star between January and December 2019, it is clear something strange has happened. It is a variable star, getting bigger and smaller, brighter and dimmer over a period of some 6 years. At its largest it would fill the solar system beyond Jupiter, if it were in the center. At its smallest it would reach to Mars.  Earth, of course, would be inside its hot gas. Betelgeuse is also very young. With a mass of 10-20 times that of the sun, it has evolved very rapidly. 

Now it is only 10 million years old, much, much younger that our sun, which is 4.6 billion years old.

 

The good news is that this unprecedented dimming appears to have ceased around February 8-10.  Now it has stabilized. Perhaps it will not explode in the near future, after all.  The European Southern Observatory released dramatic images of Betelgeuse, showing how it has dramatically changed over the course of 2019.  Its surface has changed as one part has become darker. Or, it may be due to a hot and bright convection cell that has come to the surface. Once it has released energy and has cooled, it may be darker and moving down, like the much smaller convection cells on the sun.

Perhaps you have seen the most recent photograph of those convective cells on the surface of the Sun, recently taken by the new Daniel K. Inouye solar telescope. These convection cells are blobs of hot gas carried from deep inside the star to the surface. On the surface of the Sun, they can be 1,000 km across, releasing the Sun’s heat into space. But on the surface of Betelgeuse, these convection cells are hundreds of millions of kilometers across, as large as our sun itself. Perhaps we are seeing one bright ascending cell and a darker descending one.

 

This comparison image shows the star Betelgeuse before and after its unprecedented dimming. The observations, taken with the SPHERE instrument on ESO’s Very Large Telescope in January and December 2019, show how much the star has faded and how its apparent shape has changed.

Betelgeuse, for all its beauty, is a youthful giant, headstrong and unpredictable. It is very bright because it has used up its energy much too extravagantly. What it does now is uncertain. We do suspect that sometime in its 100,000 years it will be unable to contain its exuberance and will explode with a spectacular burst of light and matter. Some of its matter will be scattered throughout the surrounding interstellar space, providing material for new stars to be born. Some of its matter will fall to the center, probably becoming a black hole. It will be a fabulous final act, but one that most parents wouldn’t mind avoiding for their own teenagers.