Our Nearest Potentially Habitable Cosmic Neighbor

According to NASA’s Exoplanet web page (exoplanetarchive.ipac.caltech.edu/index.html), we know of 3,779 planets orbiting stars other than our sun, with 2,737 more candidates awaiting confirmation. And that is just the tip of the exoplanet iceberg.

The large majority of confirmed and suspected exoplanets are discovered by the transit method. A telescope in space or on Earth stares at a star and watches for small drops in the light output that indicate a planet is passing in front of, or transiting, the star. There are many ways a star’s light may vary, but each has a specific signature as to how the brightness varies. Planetary transits cause a unique alteration in the star’s light.

This method can only detect planets whose orbit lies along our line of sight, and that’s quite unlikely. That astronomers have found so many exoplanets when they can only detect such a tiny fraction of potential candidates implies a huge number of exoplanets exist. In fact, astronomers estimate based on the known sample that the 400 billion stars in the Milky Way average 1.3 planets each.

That’s a lot of planets.

It turns that that one exoplanet is literally right next door. The closest star system to us is Alpha Centauri. It actually consists of three stars. Two of them, Alpha Centauri A and B, both roughly the size of our sun, orbit each other rather closely. The third member, named Proxima Centauri, orbits those two in a wide, 550,000-year orbit. Proxima comes closer to us than any other star, 4.2 light years at its closest.

Proxima is known to possess a planet only slightly larger than earth. And the planet lies in the star’s habitable zone, where the star provides enough heat to allow liquid water, as on Earth. Since Proxima is a red dwarf star, much smaller than our sun, the planet must orbit close to the star to be warm enough. The planet’s orbit takes only 11 days. But it is exactly in the middle of Proxima’s habitable zone. Being so close to the parent star, it is probably tidally locked. One side constantly faces the star, just like only one side of the Moon always faces Earth. This means one side is in constant daylight, the other perpetual night.

Artist conception of Proxima Centauri b - credit NASA

Anthony Del Genio, a planetary scientist at the NASA Goddard Institute for Space Studies, led a group of scientists doing computer simulations on Proxima b. They wanted to know if the planet could support life. They made the reasonable assumptions that the planet had an atmosphere as thick as Earth’s and enough water to form an ocean. Using computer models like those used by researches to study climate change on Earth, they found that under a broad range of conditions, the planet can sustain liquid water even on the night side. On Earth, where there’s water, there’s life. “The major message from our simulations is that there’s a decent chance that the planet would be habitable,” said Del Genio.

Our nearest habitable neighbor may literally orbit our nearest stellar neighbor.

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.

How common Are Earth-Like Planets? At Least They're Made of the Same Stuff.

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.

With nearly 4,000 known planets orbiting other stars (exoplanets), a few questions inevitably come up from both scientists and lay people alike: How similar are they to Earth? Do they have a composition similar to our planet? Can they support life? The problem with answering these questions is that exoplanets are tiny and extremely faint compared to the stars they orbit. Any signal from them that might help answer these questions is drowned out by the parent star.

Now, scientists have figured out a way to answer one of those questions, that of the composition of other planetary systems. We can’t directly measure the composition of the planets, but as parent stars age and evolve, they present a way to determine planetary composition.

When a sun-like star evolves to its final state, a white dwarf, it contains almost nothing but hydrogen and helium. As Dr. Siyi Xu of the Gemini Observatory in Hawaii and one of the authors of the new study explained, “White dwarfs’ atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn. As this material approaches the star, it changes how we see the star.”

Gemini South Observatory. Credit NSF

The star’s light shines through the dusty rings allowing astronomers here on Earth to determine the composition of the dust. It turns out, as Dr. Xu explains, “Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth.” Such studies don’t yet tell us if the planets have water, believed to be a prime ingredient necessary for life. But they reveal that Earth’s overall composition is rather common. And since water is one of the most abundant compounds in the universe, it seems likely that if other factors are similar to our own solar system then water exits in those planetary systems as well.

Dr. Robert Jedicke of the University of Hawaii studies our moons. That’s right, plural. We are all quite familiar with our big, bright Moon in the sky. But our solar system occasionally picks up hitchhikers in the form of small asteroids that pass near us. These mini-moons, as Dr. Jedicke calls them, allows us to study wandering asteroids to get a better look at them than we can from their distance in the Asteroid Belt. Not only will we learn more about them, Dr. Jedicke tells us they offer an even more exciting possibility. "Mini-moons are perfect targets for bringing back significant chunks of asteroid material, shielded by a spacecraft, which could then be studied in detail back on Earth." Such access to asteroids opens up both scientific and, possibly, financial opportunities, as asteroids contain significant amounts of precious metals and, perhaps more importantly, rare-earth metals, essential for our computer technology.

Diamonds are the Universe's and Earth's Best Friend

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 newsok.com.

Purveyors of fine jewelry might be salivating over two recent scientific reports. Or perhaps they are worried that the bottom may fall out of the diamond market.

Astronomers study the universe all across the electromagnetic spectrum, from the low frequency radio waves to high energy gamma rays. They can usually identify whatever they find by studying the spectrum, the way it looks at different wavelengths. For decades, astronomers have observed some unknown objects that emit a particular set of frequencies of microwave light, which they refer to as AME. They know it comes from some kind of rapidly spinning nanoparticles, but didn’t know what they were.

Astronomers have long known that a class of organic molecules in space, known as polycyclic aromatic hydrocarbons (PAHs), emitted diffuse infrared radiation, and many thought they were also responsible for the AME. A given material can shine in many different wavelength bands.

"Though we know that some type of particle is responsible for this microwave light, its precise source has been a puzzle since it was first detected nearly 20 years ago," said Jane Greaves, an astronomer at Cardiff University in Wales and lead author on a paper announcing this result in Nature Astronomy.

The new study, led by Greaves, found an IR glow around three star systems that come from nanodiamonds. These stars also emitted AME, leading the astronomers to the realization that the nanodiamonds created both types of radiation. Stars that have PAH IR-radiation don’t also show AME. Stars that do have AME contain about 1000 times Earth’s mass in diamond dust.

Geologists know much about the composition of Earth’s interior, even though we have never been there to study it directly. They gain knowledge of the interior of our planet by analyzing seismic data.  With enough data, they can accurately determine what types of rock or mineral lies at all points beneath the surface of our planet.

A craton is the deepest part of the stable interior of a continent. These extend as far as 200 miles deep into the mantle and represent the oldest existing rock on our planet. By studying the seismic data, scientists estimate that 1-2% of the cratons below each continent consists of diamond. That's according to a new study published by a team of researchers from MIT, Harvard, the University of California at Berkeley, and other institutions.

"This shows that diamond is not perhaps this exotic mineral, but on the [geological] scale of things, it's relatively common," said Ulrich Faul, a research scientist in MIT's Department of Earth, Atmospheric, and Planetary Sciences who helped write the study. "We can't get at them, but still, there is much more diamond there than we have ever thought before."

The team estimates that more than a quadrillion tons of diamonds exist at the bottom of cratons. As of now, it’s far beyond our technological ability to get them, but in time, some will slowly work their way to the surface. Future jewelers need not worry about their livelihood.

Time Travel, or The Impossibility Thereof

Time travel is a tried and true science fiction staple. It usually involves being able to fly in a spaceship faster than the speed of light or diving through a wormhole. None of those technologies currently exist in the real world of science.

Astrophysicists often discuss wormholes: can one be created without a black hole as the door, would it be be stable, would it be large enough to travel through without getting destroyed in the process, and what kind of energy source might it take to create one? So far, no one has any idea how to do any of that. NASA is currently testing an engine, known as the EM Drive, which seems to have potential for faster than light travel. But, as of now, no one even knows how it generates thrust.

Albert Einstein said that no object with mass, like a spaceship, can go at the speed light as it would take an infinite amount of energy to get there. He didn’t exactly say nothing could travel faster than the speed of light. You might think that if it can’t travel AT the speed of light, how can a spaceship go faster than the speed of light? Physics allows for a phenomenon called “tunneling” where an object can be in condition A and B but not in between. Physicists run rather simple experiments where objects go from A to B even though they can’t be in between the two states. So far, they’ve only done such experiments with objects like electrons, not spaceships, but that may just be a matter of technology.

Scientists have also discussed ways to create wormholes without a black hole doorway. It only takes a lot of energy. Like a sun’s worth of energy, but still not impossible, in theory.

But here is the rub with time travel. One of the most fundamental truths physicists know about the universe is the conservation of energy. Since Einstein showed us that matter and energy are intimately related via his famous equation E=MC², the full conservation rule is that the total amount of mass and energy must be conserved. It’s known as the 1^st Law of Thermodynamics.

Let’s say I want to travel back in time to meet George Washington. Once I left this time, there is suddenly less mass-energy in the universe now and there is suddenly more mass-energy in the universe in 1776. It all averages out, but the 1^st Law of Thermodynamics is exact, not an average. This appears to make time travel impossible.

Unless, somehow, the exact same amount of mass-energy transfers from then to now at exactly the same instant I go to then. But you might randomly take half a person from then and move him or her to now.

I think I’d just leave it alone.

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 newsok.com.

Is the Discovery of Earth 2.0 Imminent

Astronomers currently know of 3726 confirmed planets beyond our solar system. The Kepler space telescope found the bulk of them, and 4496 more Kepler candidate exoplanets await confirmation. Now, two new instruments are set to boost those numbers considerably.

Kepler’s successor is the Transiting Exoplanet Survey Satellite (TESS) which launched last month. Like Kepler, TESS will continuously stare at a large number of stars, watching intently for slight drops in the stars brightness as an orbiting planet passes in front of, or transits, any of them. TESS plans on watching far more stars than Kepler did, so it should be far more successful at finding them.

The discovery process used by Kepler and TESS can only be done in space. The change in brightness as a planet passes in front of its parent star is miniscule, at most only one percent of the star’s brightness. If you have ever look at stars in the night sky from the surface of Earth, you know they twinkle or change in brightness. A star’s twinkling changes the apparent brightness of a star by well more than one percent. That flickering is caused by turbulence in our atmosphere.

In space, stars don’t twinkle as there are no molecules of atmospheric gases interfering with the view. A dedicated space telescope can easily track such tiny changes in a star’s brightness. There are other processes that can cause a star to dim a bit. Sunspots come and go on our sun’s surface all the time, which causes its light output to vary. Some stars are inherently variable. But all the other known ways a star’s brightness can change have a different pattern than a planet transiting a star. Kepler’s and TESS’s software filters light changes of the wrong pattern. And you can’t argue with Kepler’s track record.

The other new piece of equipment goes by the acronym DARKNESS (the DARK-speckle Near-infrared Energy-resolved Superconducting Spectrophotometer). Astronomers love cute acronyms for their projects, even if it is sometimes a stretch. DARKNESS uses a new type of camera with a new imaging technique to actually photograph the planets directly.

This is no easy task. Trying to see a planet close to a star is like trying to see a firefly next to a giant spotlight. The ability to resolve these two objects so close together and so different in brightness is beyond the capability of the semiconductor-based cameras used in all telescopes until now. This is the same technology used by the Hubble Space Telescope, Kepler, Tess and your cell phone. Fine for selfies, but not for seeing a firefly next to a spotlight.

DARKNESS uses superconducting technology for vast improvement in resolution. “When a single photon with the energy of more than 1 electron volt hits a semiconductor detector, it frees one electron," said physicist Ben Mazin from the University of California, Santa Barbara, who led the team developing the camera. "In a superconducting detector, it frees something like 5,000 or 10,000 electrons. And since there are many more electrons to measure, we can do things that you can't do with the semiconductor detector."

DARKNESS will have a capability currently not available. "It actually takes a picture of the star and the planet," said Mazin. "You can [even] get a spectrum of the planet, but it's extremely technically challenging." The ability to get a spectrum means we can decipher the makeup of the planet’s atmosphere and see if it contains certain constituents, like oxygen or methane, which indicate the presence of life.

DARKNESS or TESS may soon find Earth 2.0.

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 newsok.com.

Is This the Way the World Ends?

Astrophysicists feel like they have a pretty good handle on how the universe began. Nearly 14 billion years ago, a quantum fluctuation randomly popped into being and expanded rapidly, at times even faster than the speed of light. All matter and energy and the laws of physics for the entire universe came into being with that quantum fluctuation, that we now call the Big Bang.

While there is debate on some of the details of this Big Bang theory, the basic picture is accepted by the vast majority of scientists. The ending of the universe is open to far more speculation. Our universe is still growing larger from that Big Bang beginning. And evidence points to the expansion rate increasing, due to some mysterious, unknown force we call Dark Energy. Some astrophysicists think it may expand forever, galaxies simply moving farther and farther apart until our Milky Way becomes totally isolated in the universe. Others think that expansion force is so great, it will eventually rip the galaxy apart, then our solar system, ourselves and, finally, atoms themselves. Ultimately, those scientists say, the universe will consist nothing but a very cold sea of low energy photons.

Some astrophysicists argue that the expansion eventually halts, and the universe starts to collapse, perhaps back to the singularity it all started with. Some think the universe will bounce from that collapse, leading to another Big Bang, one of an infinite successions of such beginnings.

In a recent study led by Anders Andreassen, a physicist at Harvard University, the study scientists claim the universe’s final moment will be triggered by bizarre consequence of subatomic physics called an instanton. An instanton is one solution to equations governing the motions of subatomic particles. An instanton can create a tiny bubble that will expand throughout the universe at the speed of light, swallowing everything in its path. Instantons create this bubble in the Higgs field, the quantum field that gives us the newly discovered Higgs boson and which imparts mass to all subatomic particles.

"At some point you will create one of these bubbles," Andreassen says. "It will be very unpleasant." For ‘unpleasant’ read ‘the end to all life and all chemistry as we know it.’

No need to sit and worry about it, though. Although it could occur tomorrow, the odds are that the universe has a lifetime of somewhere between 10 octodecillion years (one with 58 zeros after it) and 10 quinquadragintillion years (one with 139 zeros after it). Just like the world-busting, giant killer asteroid with Earth in its crosshairs, it’s not likely to happen in our lifetime. It likely won’t occur within in the lifetime of our solar system, probably not even in the lifetime of the Milky Way galaxy.

But it is coming, sometime, to a universe near you.

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 newsok.com.