March 5, 2023

Early March at 8:30 PM looking south

Sunday, March 5, 2023

Evening planetarium shows will start up again this spring now that the Chronos star projector has been serviced and all parts are functioning correctly. We'll start with “Incoming!” on March 16 and then do Black Holes on April 13 and Ice Worlds the following week on April 20.

Hopefully, the weather in your area cooperated enough for you to see the close conjunction of Venus and Jupiter last Wednesday on March 1. Although Venus and Jupiter regularly have conjunctions every year or so, they aren't always as close together when they meet and easily visible. The next conjunction as close as last week's one will be in 2027. 

Jupiter will continue to sink down lower toward the sun in our evening sky. By the end of the month it will be lost in the glare of the evening twilight. Jupiter will be at solar conjunction on April 11. 

The moon will be at full phase the night of March 6/7 and it will be below the middle of Leo. Leo rising in the evening sky tells us that spring is right around the corner. At full phase the moon is nearly 180 degrees opposite the sun—the moon's tilted orbit means it's usually not exactly 180 degrees at full phase—so the full moon rises at about sunset. Eight days later, the moon will be at third (or last) quarter phase among the stars of Scorpio. At third quarter, the moon rises at about midnight (or 1 AM during daylight saving time). 

One interesting astronomy research article came across my desk recently. It is a proposal that the supermassive black holes with millions to billions of times the mass of our sun residing at the cores of most galaxies may be responsible for the “dark energy” that is causing the expansion of the space between galaxies to speed up. 

One of the predictions of quantum mechanics is that empty space has an energy field called “vacuum energy”. That vacuum energy of empty space exerts a force opposing gravity causing the coordinate system of space itself to accelerate as it expands. It is possible that Einstein's General Relativity theory of gravity predicts the formation of objects that are giant balls of this vacuum energy. Even more bizarre, is that these objects would look to the outside observer exactly like a black hole. If true, these objects would grow in mass in direct proportion to the universe's expansion.

To test this idea a team of astronomers examined the properties of the supermassive black holes at the centers of a type of galaxy called elliptical galaxies at a wide range of distances from us to see how the mass of the black holes changes with the age of the universe. Let me unpack that sentence a bit. Elliptical galaxies have billions to trillions of stars swarming about in ellipsoidal shaped blobs held together by their mutual gravity for each other. Unlike spiral galaxies like our own Milky Way galaxy or other splotchy irregular galaxies, the elliptical galaxies have used up most or all of their gas and dust in a burst of star formation long ago. What that means is that the supermassive black holes at the cores of elliptical galaxies won't have gas and dust swirling into them to feed the black hole and make them grow larger in mass. 

Because of the great distances in the universe, the light from distant galaxies takes millions to billions of years to reach us, so we see the galaxies as they WERE long ago with the more distant ones telling us about the younger or earlier universe. The team of astronomers examining the supermassive black holes at the cores of their samples of elliptical galaxies found that the supermassive black holes of long ago were much smaller relative to their host galaxy than those of supermassive black holes in much closer elliptical galaxies, i.e., those in more modern, recent times to the present day. The supermassive black holes in these elliptical galaxies did not grow larger over time by gobbling up a bunch of gas and dust. They got larger with time over the universe's history in just the way the universe has expanded over time—just as if they were made of these balls of vacuum energy responsible for the “dark energy”. 

Well, it's an exciting proposal but pretty controversial. Some astronomers don't think the balls of vacuum energy could be stable and there doesn't seem to be enough black holes of any size to produce the amount of repulsive “dark energy” we see. Also, we would like to see if there are other observable links between the black holes and the dark energy to provide an independent test of the idea. Unfortunately, this proposal is so new and cutting edge that we don't know what those links would be.

Actually, I shouldn't say “unfortunately” in that previous sentence. Not knowing is why we explore—do research. The answers of research science are not in the back of the book. Research science is writing the book and we often have no idea how the “plot” of the book will turn out but it's darn fun figuring it out as we go along—most brains are wired to find pleasure in solving puzzles or mysteries of one form or other.

Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website