Dec 11, 2019
We've all wondered if we're alone in our solar system or if there are other planets out there and beyond that can support "life." Here in articles from nbcnews.com we see discussions of the possibility that this may be true.
New study shows Earth-like worlds may be common. The odds of finding alien life just went up.
Earth-like planets may not be so special after all, and that's good news for scientists involved in the search for alien life.
A new analysis of light from nearby stars suggests that rocky worlds like our own are plentiful in our Milky Way galaxy. In turn, the finding suggests that many exoplanets — possibly with magnetic fields, substantial atmospheres and tectonic plates that bring minerals to the surface — could have conditions that allowed life to evolve there.
“When we started to find planets around other stars, the odds of life existing on other stars went up,” said Edward Young, a geochemist at the University of California, Los Angeles, and a co-author of a paper about the new research published Oct. 18 in the journal Science. “When we started finding rocky planets, they went up again — and now we are finding evidence that the rocky planets could be similar to Earth, so now the odds have gone up yet again.”
For their research, Young and other members of his team used data from telescopes at Hawaii’s Keck Observatory to study the light from six white dwarf stars located 200 to 665 light-years from Earth.
Each of the white dwarfs was once a star much like our sun but all exploded millions of years ago after exhausting the hydrogen that served as their fuel. The explosions left behind super-dense remnants of the original stars’ cores, roughly half the mass of our sun and the size of the Earth, surrounded by orbiting disks of rocky fragments that were once their planets and nearby asteroids.
The researchers studied patterns of light emitted by the white dwarfs — a technique known as spectroscopy — to reveal the chemical composition of the rocky fragments, which had been sucked up by the white dwarfs’ intense gravity.
“Observing a white dwarf is like doing an autopsy on the contents of what it has gobbled in its solar system,” geochemist Alexandra Doyle of UCLA, the paper's lead author, said in a statement.
What did the analysis reveal? Five out of the six white dwarfs had sucked up fragments whose chemical composition is similar to rocks on Earth, Venus and Mars (which along with Mercury are our solar system’s rocky planets). The researchers concluded that the planets that gave rise to the fragments were made of similar rock.
Since the minerals in the fragments are similar to those on Earth, it’s likely that the planets that gave rise to the fragments resembled our planet in other ways — including having a relatively dense atmosphere, a metallic core that generates a magnetic field capable of protecting life from harmful radiation from space, and tectonic plates that help recycle buried minerals to the surface.
Astronomer Caleb Scharf, director of the Columbia Astrobiology Center in New York City, praised the new research.“This is a terrific bit of astronomical detective work … neatly bringing astrophysics together with geochemistry,” he told NBC News Mach in an email.
Scharf said conditions suitable for life depend upon many additional factors not addressed in the new research, including the presence of radioisotopes as a source of heat in a planet’s interior and other quirks of planetary formation. “But it definitely points towards many rocky planets being pretty familiar in terms of their general composition and, therefore, structure and behavior,” he said.
Seth Shostak, a senior astronomer for the SETI Institute in Mountain View, California, echoed Scharf’s assessment of the new research. “It’s a very ingenious scheme to learn if worlds like Mercury, Earth or Mars are common or otherwise,” he said in an email. “Fortunately for those hoping to find life elsewhere in the cosmos, it seems such planets are likely to be ubiquitous.”
More than 4,000 exoplanets have been found around other stars in our galaxy, most by the Kepler Space Telescope. But we have yet to find alien life.
How a discovery that earned the Nobel Prize in Physics transformed the hunt for alien life
Now astronomers know that our galaxy is studded with planets that might harbor life.
The biggest astronomy story of the past two decades is that the universe is studded with planets. Sweden’s Nobel Prize committee clearly agrees, as they just handed their coveted physics award to Michel Mayor and Didier Queloz — two Swiss astronomers who were the first to find convincing evidence about a world in another normal stellar system. What they uncovered was a bulky planet orbiting 51 Pegasi, an otherwise unremarkable sunlike star about 50 light-years away.
Since that 1995 discovery, more than 4,100 additional exoplanets have been found. That’s an impressive number, so it’s fair to ask whether this new knowledge has changed the way we look for extraterrestrial life.
Few of these exoplanets are the kind you’d expect would cook up intelligent extraterrestrials. The universe boasts many, many second-string exoplanets: large waterlogged worlds, vaporous gas balls and objects that are simply too hot or too cold to be great places for biology.
Yet, preliminary estimates suggest that about 1 in 5 star systems contains a planet that is something like Earth. That adds up to tens of billions in our own Milky Way galaxy, and that doesn’t count all the moons that might also incubate life.
Given all this newly uncovered cosmic real estate, shouldn’t scientists involved in the search for extraterrestrial intelligence (SETI) be assiduously aiming their antennas its way? Wouldn’t doing so better the odds that we’ll trip upon some alien BFF?
We may be closing in on the discovery of alien life. Are we prepared?
Well, yes. And indeed, many of these exoplanet systems have been surveilled by SETI researchers. But the real influence of exoplanets on the hunt for E.T. is more subtle.
To understand why, let’s briefly return to those golden days of yesteryear. When major SETI searches — ones that listened for signals from many hundreds of star systems — got underway in the early 1990s, we didn’t know which might have planets. In fact, it was conceivable (but a poor bet) that none of them did. So SETI scientists preferentially pointed their instruments in the directions of sunlike stellar systems. After all, the sun was the only star we knew that (jokes aside) shone on intelligent beings.
This was a conservative strategy, and hard to fault — a bit like restricting your dining choices to familiar restaurant chains. Doing so confers a reasonable expectation of getting an edible meal, even if better fare might be had elsewhere.
The exoplanet discoveries have expanded the choices for researchers and eased their personal anxieties because they finally can be certain that planets are plentiful. As an example, consider a type of star that scientists had always excluded from the SETI club: red dwarfs. These bantam stars were considered unlikely to host many close-in planets — worlds that orbit near enough to their suns to receive sufficient energy to sustain life.
But exoplanet hunters have proven that assumption wrong. Several red dwarf stars have been found that are ringed by possibly habitable planets. And since 75 percent of all stars happen to be red dwarfs (only 8 percent are similar to the sun), this is like suddenly learning that there are 10 times as many restaurants in your neighborhood as you once thought. Your drive to dinner is shortened, and your menu options have increased.
The practical result of finding lots of planets has been to shift SETI efforts from looking at a certain type of star system to simply looking at the nearest ones. On average, the systems examined today are only half as far away as when only sunlike stars were examined. Any signals would be four times stronger and, of course, if we find someone at home, a back-and-forth conversation might be more practical.
Mayor and Queloz weren’t looking for planets when they found one around 51 Peg, but they’re being justly credited with paying attention to their data and realizing what it implied. Like many discoveries in science, theirs was accidental, but realizing its importance was not.
Dr. Seth Shostak is Senior Astronomer at the SETI Institute in Mountain View, California and also host of the “Big Picture Science” podcast.
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