In our skies: As the years roll by more is discovered about our universe

Alan Hale
Guest columnist
Local astronomer Alan Hale.

This author welcomes his high school classmates to the area this weekend as they come to attend their reunion. It was 40 years ago on May 27, 1976, that the Alamogordo High School’s class of 1976 graduated and went their various separate ways into the wider world.

Not all of us have made it to this point; those of us who have, have our stories about the journeys we have taken to arrive here.

From the perspective of the overall universe, or even the solar system, the passing of the past 40 years is an unnoticeable blip. The universe, and the solar system, are essentially no different now than they were then. What has changed enormously during these past 40 years, however, is our understanding of that universe and that solar system, almost to the point where they are not even recognizable from what we used to think we knew.

The longstanding view of the solar system up until that point was that of the sun being orbited by nine planets, with an asteroid belt between Mars and Jupiter, a few small asteroids venturing closer to the sun, and the occasional comet passing through the inner solar system. Most of the planets were little more than bright points of light in the nighttime sky; a few spacecraft missions have been sent to Venus, and a few more to Mars, but that was mostly it.

That long-ago summer of 1976 brought the most ambitious Mars endeavor to date: the twin Viking missions, each consisting of an orbiter and a lander, arrived at the red planet. The two landers, in particular, did not succeed at their primary objective of detecting signs of life, which led to the belief that Mars is almost certainly a dead, lifeless world. However, the orbiters revealed evidence that Mars had previously contained water, and numerous recent missions, including fantastically successful surface rovers like Spirit, Opportunity, and Curiosity, have demonstrated that not only did Mars have large amounts of water in the past, it apparently has a fair amount of water today, and the conditions for life almost certainly existed in the past and may still exist now.

Our knowledge of the outer solar system has changed even more, beginning with the discovery in March 1977 – less than a year after our graduation – that, in addition to Saturn, the planet Uranus also has a system of rings. We now know the same is true for Jupiter and Neptune as well. Two spacecraft missions, Pioneers 10 and 11, had flown by Jupiter in the early 1970s, but the true exploration of the outer planets began with the twin Voyagers 1 and 2 missions that were launched in 1977. Between these two spacecraft all four of the large gaseous planets have been visited, and meanwhile various orbiting missions, including the Juno mission which arrived at Jupiter early this month, have increased our understanding even further.

One dramatic thing that these various missions have revealed is that several of the moons of these distant planets are in fact dynamic worlds in their own right. Active volcanoes on Jupiter’s moon Io, a likely subsurface ocean, and perhaps life, on Jupiter’s moon Europa, and a dense atmosphere and active weather patterns on Saturn’s moon Titan, are among the many discoveries that the spacecraft missions have revealed to us.

Pluto had long been a mystery ever since its discovery in 1930. The discovery of Pluto’s large moon Charon in 1978 brought the first significant hints that Pluto might be quite a bit smaller than first envisioned. Meanwhile, the discovery of additional objects – now numbering several hundred – in the far distant solar system beginning in 1992 which culminated in the discovery in the mid-2000s of several worlds near Pluto’s size has revealed to us that this part of the solar system is far more complex than we ever thought. The New Horizons spacecraft which flew by Pluto and Charon one year ago has shown us that these are also fantastic worlds in their own right.

Closer to home, in 1976 only a handful of asteroids were known in the near-Earth vicinity, and any new discovery of such an object was a widely-heralded event. More and more began to be found as the years have rolled by, and nowadays hundreds of such asteroids are known, with dozens being discovered every year.

The study of these objects has helped tremendously in our understanding of how the solar system evolved and how planets like Earth formed, and has shown that such objects may present both a threat as well as a source for potential resources in the future.

In 1976 we did not know of any planets beyond our solar system, and while the general consensus among astronomers was that other planetary systems almost certainly did exist, they were likely somewhat similar in form to our own. The first confirmed discoveries of exoplanets turned these speculations on their ear: the very first planets, announced in 1992, orbit around a pulsar, i.e., the remaining core of a massive star that has exploded as a supernova, and meanwhile the first-known planet around a star like our sun, announced in 1995, is a giant Jupiter-size world that orbits around its sun every four days.

Today almost 3,000 confirmed planets have been discovered orbiting around other stars, and another 2,500 candidate planets are awaiting confirmation. These discoveries have demonstrated that our solar system is nowhere close to being a typical planetary system, in fact, there doesn’t seem to be any such thing. A few worlds have been found that superficially resemble Earth in terms of size and distance from their parent sun, although we haven’t quite found Earth 2 yet.

And these discoveries only barely scratch the surface of what we have learned over the past 40 years. One can only imagine what we might learn by the time of our 80th reunion, should any of us graduates survive that long.
