A Unique Sight? Every Night.

 Change is inevitable in our lives. We are born and grow older and taller. We might have children and we’ll watch them grow and change. Our hair eventually turns grey, or in my case, falls out. Our eyesight may fade, our joints may become stiffer.

 We grow older as does everyone we know and care about. Birth and death are a constant part of our world. Day turns into night; spring turns into summer. The clothes we wear at different times of the year, even the fashions we wear now as opposed to just a few years ago. But those changes are superficial.

 Would you like to see an absolutely unique sight? One you’ve never seen and one you’ll never see again? Wait until it gets dark, go outside, and look at the night sky. Do you see it? It has never been seen before, and never will again. It is tonight’s sky.

 The sky has never looked exactly as it does tonight and will never do so again.

 We think of the night sky as being constant. Oh, sure, the constellations move across the night sky from east to west, just like the sun in the daytime. The constellations visible in the night sky now will be almost completely different in six months. But, every April 15^th, we see the same stars. The sun will rise in a slightly different location tomorrow than it did today, but in one year, it will return to where it rose this morning.

 But the night sky changes in a way that all those seeming cycles never actually repeat. As the planets move in their annual dance around the sun, their pattern in the sky constantly changes. You’ll never see the exact arrangement of the planets again that you will see tonight.

 

The planets orbiting our sun.

Our planet’s poles slowly move so that the North Pole points to different stars over time, a motion called precession. This means the North Star we have now, Polaris, won’t always be our North Star. That creates subtle changes in the night sky over a 26,000-year period.

 

Precession and the path of the North Pole in the night sky.

 Our sun orbits the center of the Milky Way galaxy, so the exact pattern of stars in the night sky slowly changes. All other stars move under the various gravitational influences that direct their motions as they, too, orbit around the Milky Way.

 New stars are born and old stars die, sometimes with a dramatic effect.

 

The Great Nebula in Orion, where new stars are forming.

 

The Crab Nebula, the remains of a star that died in a supernova explosion.

 

Galaxies move through the universe, sometimes colliding. The larger galaxy then absorbs the smaller galaxy, gaining from the cannibalized galaxy the stars and gas clouds, the places where new stars come into being. Most of those new stars will have new planets orbiting them. Some of those planets will likely create new living beings.

Two galaxies colliding. They will eventually merge into one.

Change is the one constant in our lives. Even our night sky is eternally, if slowly, evolving.

This is the true magic of astronomy. You never get reruns. Each night remains unique. So, enjoy this night sky, because it will be different than any other night throughout time.

 

   

Are We Close to Finding Earth 2?

 

NASA and other space agencies have launched several missions to search for exoplanets, planets that orbit other stars. The Holy Grail of such programs is finding an Earth-like planet orbiting a sun-like star at the right distance to allow liquid water on the surface. Such planets seem to be the most likely candidates to search for life.

While astronomers have yet to find a perfect Earth 2, statistical analysis of NASA’s most successful planet hunter, the Kepler Mission, uncovered some promising data. A study by NASA scientists alongside collaborators from around the world who worked on the Kepler mission came to an exciting conclusion. According to the research, about half the stars similar in temperature to our Sun could have a rocky planet capable of supporting liquid water on its surface.

Image Caption/Credit: NASA’s Kepler Planet Finder telescope, credit NASA

"Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable," said the lead author Steve Bryson, a researcher at NASA's Ames Research. "Though this result is far from a final value, and water on a planet's surface is only one of many factors to support life, it's extremely exciting that we calculated these worlds are this common with such high confidence and precision."

Kepler detected planets by continuously staring at thousands of stars, watching for a tell-tale drop in brightness caused by an orbiting planet crossing in front of a star. Such a method couldn’t detect planetary systems seen more face on, so astronomers had to use statistical methods to extrapolate from the Kepler data to all the other stars in our galaxy. Kepler discovered so many exoplanets from its limited mission that astronomers now believe that more than half of the four billion stars in the Milky planet possess planets, typically more than one.

Using their most conservative estimate, that 7% of all sun-like stars have Earth-like planets, meaning some 300 million exist in our Milky Way alone. Their most likely estimate states that Earth-like planets orbit 50% of sun-like stars, making more than 2 billion Earth-like planets. Since we know of only one planet with life, ours, those planets are the best place to begin to search for alien forms of life.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.newsok.com.

There are Lots of Earth-like Planets -- How Many are Lifebearing?

Scientists who think about the possibility of extraterrestrial life need data to estimate those possibilities. Because Earth is the one and only known example of a life-bearing planet, it seems logical, therefore, to use ours as a model for life-bearing planets. The first, best place to hunt for alien life would be on planets like Earth

And this is where data is needed. Just how many Earth-like planets exist in our Milky Way galaxy? Fortunately, we have reams of data on planets orbiting other stars from the Kepler space telescope. It spent more than nine and a half years doing nothing but searching for extrasolar planets. It discovered more than 2,600 planets with nearly 3,000 still awaiting confirmation. That’s a lot of data.

One thing astronomers learned from a statistical analysis of that data is that Earth-like planets are rather common. Twenty billion sun-like stars call the Milky Way home, and Kepler teaches us that one in four of them have planets roughly the size of Earth orbiting in the habitable zone, where, as on Earth, liquid water can exist. That’s five billion Earth-like planets in the Milky Way. And that’s not even counting the billions of other stars of different sizes than our sun that also possess Earth-sized planets in their habitable zones.

Artist depiction of a habitable exoplanet. Credit NASA-JPL

That sure sounds like the potential exists for a galaxy teeming with life.

Now, astronomers want to check for the actual existence of alien life. We can’t yet send probes to examine those planets. But we can examine the atmosphere of an alien planet for life-supporting gases. According to Eric B. Ford, professor of astronomy and astrophysics at Penn State, “Scientists are particularly interested in searching for biomarkers – molecules indicative of life – in the atmospheres of roughly Earth-size planets that orbit in the ‘habitable zone’ of sun-like stars.”

With five billion planets to examine, the search might be tedious, but the payoff will be the most amazing scientific discovery ever. And it appears to be only a matter of time before we discover alien life.

The map shows the sky at 10:00 early in the month, 9:00 in the middle of the month, and 8:00 at the end of the month. Map produced using Night Vision star mapping software. 

On or about the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

Beaches. And Deserts and Sandboxes.

Perhaps you’ve heard this before: There are more stars in the universe than all the grains of sand in all the beaches, desserts and sandboxes on Earth.

There are a lot of sand grains on Earth. Sand constitutes a major fraction of the makeup of Earth. Scientists estimate the number by measuring the average size of a sand grains, then calculating how many sand grains it would take to fill, say, a gallon jug. Using the latest geological studies, they calculate the total volume of sand on Earth. Scientists estimate that Earth contains 7.5 sextillion sand grains. That is 75 followed by 17 zeros. That’s a lot of sand.

Astronomers calculate the total number of stars in the universe by studying nearby galaxies, ones in which we can count the stars, to see how many it takes to make a galaxy shine. Then, based on detailed counts of galaxies we can see, and making conservative estimates of how many we can’t see, they estimate the total number of stars in the universe. Our universe contains at least 70 septillion stars, 7 followed by 23 zeros.

Astronomers estimate there exist roughly 10,000 stars for each grain of sand on Earth. That’s a lot of stars.

Credit NASA-ESA

Astronomers recently discovered the origin of sand grains. For years, they believed that only sun-like stars created lots of carbon and silicon dust, and the silicon dust is the source of sand. That meant that the universe had to evolve to the point where there were lots of sun-like stars before lots of sand could accumulate. Recently, astronomers discovered the galaxies that formed very early in the universe, before many sun-like stars could form, contained a lot of dust. Long before stars like our sun were common, planets like Earth may have formed.

There may be a huge number of planets in our universe capable of supporting life.

On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission form the Oklahoman and www.newsok.com.