# data[].attributes.body
Do you believe there’s other life in space? Well to find out we would have to explore space. We should spend valuable resources for space exploration because it’ll give us more information about any dangers in space, it’ll give us a chance to find a potential new world, and to see if there is any other life forms out there.

# data[].attributes.body
We should spend valuable resources for space exploration because it’ll give us more information about any dangers in space, it’ll give us a chance to find a potential new world, and to see if there is any other life forms out there.

# data[].attributes.body
I know we should spend more money on space exploration because we can get a lot more information about dangers in space which would help us get prepared such as...

# data[].attributes.body
Finding a new world in space would be helpful because...

# data[].attributes.attachment_link.provider_name
Exoplanet Exploration: Planets Beyond our Solar System

# data[].attributes.attachment_link.readable_text
What is the habitable zone?

There's a helpful concept we use to help understand what distance from a given star you might expect to find planets with liquid water on their surface - liquid water being essential for life as we know it. It's called the habitable zone. Every star has a habitable zone, but where that zone lies is different for stars of different sizes and brightness. Credit: NASA/JPL-Caltech

When searching for possibly habitable exoplanets, it helps to start with worlds similar to our own. But what does "similar" mean? Many rocky planets have been detected in Earth's size-range: a point in favor of possible life. Based on what we've observed in our own solar system, large, gaseous worlds like Jupiter seem far less likely to offer habitable conditions. But most of these Earth-sized worlds have been detected orbiting red-dwarf stars; Earth-sized planets in wide orbits around Sun-like stars are much harder to detect.

And, of course, when talking about habitable exoplanets, we're really talking about their stars, the dominant force in any planetary system. Habitable zones potentially capable of hosting life-bearing planets are wider for hotter stars. Smaller, dimmer red dwarfs, the most common type in our Milky Way galaxy, have much tighter habitable zones as in the TRAPPIST-1 system. Planets in a red dwarf's comparatively narrow habitable zone, which is very close to the star, are exposed to extreme levels of X-ray and ultraviolet (UV) radiation, which can be up to hundreds of thousands of times more intense than what Earth receives from the Sun.

This infographic compares the characteristics of three classes of stars in our galaxy: Sunlike stars are classified as G stars; stars less massive and cooler than our Sun are K dwarfs; and even fainter and cooler stars are the reddish M dwarfs. Credits: NASA, ESA and Z. Levy (STScI)

Where are we looking for life, and why?

Where are we looking for life, and why?

An old joke offers an answer: Asked why, on a dark night, he was looking for his missing car keys beneath a street lamp, the man answered, "because the light's better." Life on other planets might be like nothing on Earth - it could be life as we don't know it. But it makes sense, at least at first, to search for something more familiar. Life as we know it should be easier to find. And "the light's better" in the habitable zone, or the area around a star where planetary surface temperatures could allow the pooling of water.

Other similarities to Earth come into sharper focus in the search for life. Many rocky planets have been detected in Earth's size-range: a point in favor of possible life. Based on what we've observed in our own solar system, large, gaseous worlds like Jupiter seem far less likely to offer habitable conditions. But most of these Earth-sized worlds have been detected orbiting red-dwarf stars; Earth-sized planets in wide orbits around Sun-like stars are much harder to detect. Yet these red-dwarfs have a potentially deadly habit, especially in their younger years: Powerful flares tend to erupt with some frequency from their surfaces. These could sterilize closely orbiting planets where life had only begun to get a toehold. That's a strike against possible life.

Because our Sun has nurtured life on Earth for nearly 4 billion years, conventional wisdom would suggest that stars like it would be prime candidates in the search for other potentially habitable worlds. G-type yellow stars like our Sun, however, are shorter-lived and less common in our galaxy.

The artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. More about stars ›

Stars slightly cooler and less luminous than our Sun - called orange dwarfs - are considered by some scientists as potentially better for advanced life. They can burn steadily for tens of billions of years. This opens up a vast timescape for biological evolution to pursue an infinity of experiments for yielding robust life forms. And, for every star like our Sun there are three times as many orange dwarfs in the Milky Way.

K dwarfs, are the true "Goldilocks stars," said Edward Guinan of Villanova University, Villanova, Pennsylvania. "K-dwarf stars are in the 'sweet spot,' with properties intermediate between the rarer, more luminous, but shorter-lived solar-type stars (G stars) and the more numerous red dwarf stars (M stars). The K stars, especially the warmer ones, have the best of all worlds. If you are looking for planets with habitability, the abundance of K stars pump up your chances of finding life."

Exoplanet temperature, size, star type: the galaxy offers up a menu of worlds that echo aspects of our own, yet at the same time are vastly different.

Image credit: NASA

Next: Why we search for life

# data[].attributes.attachment_link.keywords[]
national aeronautics and space administration

# data[].attributes.attachment_link.title
The Habitable Zone | The Search For Life - Exoplanet Exploration: Planets Beyond our Solar System

# data[].attributes.attachment_link.description
Have you heard of the habitable zone? You're in one right now. It's the distance from a star where you might find exoplanets with liquid surface water. We use the habitable zone to help focus our search for life beyond Earth.

# data[].attributes.body
Knowing if there is anymore life in the universe would be helpful because...

# data[].attributes.attachment_link.provider_name
Exoplanet Exploration: Planets Beyond our Solar System

# data[].attributes.attachment_link.readable_text
As humanity casts an ever-wider net across the cosmos, capturing evidence of thousands of worlds, an ancient question haunts us: Is anybody out there?

The good news: We know vastly more than any previous generation. Our galaxy is crowded with exoplanets - planets around other stars. A healthy percentage of them are small, rocky worlds, of a similar size and likely similar composition to our home planet.

The ingredients in the recipe for earthly life - water, elements associated with life, available sources of energy - appear to be almost everywhere we've looked.

Now the bad news. We have yet to find another "Earth" with life, intelligent or not. Observing signs of possible microbial life in exoplanet atmospheres is currently just out of reach. No convincing evidence of advanced technology - artificial signals by radio or other means, or the telltale sign of, say, massive extraterrestrial engineering projects - has yet crossed our formidable arrays of telescopes in space or on the ground.

And finding non-intelligent life is far more likely; Earth existed for most of its history, 4.25 billion years, without a whisper of technological life, and human civilization is a very late-breaking development.

Is there life beyond Earth? So far, the silence is deafening.

"I hope it's there," said Shawn Domagal-Goldman, a research astronomer at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "I want it to be there. I'll be planning a party if we find it."

Domagal-Goldman co-leads a team of exoplanet hunters who, in the years and decades ahead, are planning to do just that. Working with scientists across NASA, as well as academic and international partners, his team and others are helping to design and build the next generation of instruments to sift through light from other worlds, and other suns. The goal: unambiguous evidence of another living, breathing world.

While the chances of finding life elsewhere remain unknown, the odds can be said to be improving. A well-known list of the data needed to determine the likely abundance of life-bearing worlds, though highly conjectural, is known as the "Drake equation."

Put forward in 1961 by astronomer Frank Drake, the list remains mostly blank. It begins with the rate of star formation in the galaxy and the fraction of stars that have planets, leading step-by-step through the portion of planets that support life and - most speculatively - to the existence and durability of detectable, technological civilizations.

When Drake introduced this roadmap to life beyond Earth, all the terms - the signposts along the way - were blank.

Some of the first few items are now known, including the potential presence of habitable worlds, said researcher Ravi Kopparapu from Goddard, also a co-leader of Domagal-Goldman's team. He studies the habitability and potential for life on exoplanets.

If we develop and launch a powerful enough space telescope, "we could figure out if we have advanced life or biological life," he said.

Finding a planet that's 'just right'

Drake's list can be a good conversation starter, and a useful way to frame the complex questions around the possibility of other life. But these days, scientists don't spend a great deal of time discussing it, Domagal-Goldman said.

Instead, they use a narrower yardstick: the habitable zone.

Every star, like every campfire, has a definable zone of radiated warmth. Too close, and your marshmallow - or your planet - might end up as nothing more than a charred cinder. Too far away, and its surface remains cold and unappetizing.

In both cases, "just right" is more likely to be somewhere in between.

For a planet, the habitable zone is the distance from a star that allows liquid water to persist on its surface - as long as that planet has a suitable atmosphere.

In our solar system, Earth sits comfortably inside the Sun's habitable zone. Broiling planet Venus is within the inner edge, while refrigerated Mars is near the outer boundary.

Determine the distance of an exoplanet from the star itself, as well as the star's size and energy output, and you can estimate whether the planet falls within the habitable zone.

Image credit: NASA/JPL-Caltech/Lizbeth B. De La Torre

For larger, hotter stars, the zone is farther away; for smaller, cooler stars, it can be very close indeed. Finding these "just right" planets in the habitable zone is one of the keys to finding signs of life.

"If they fit within these parameters, they could potentially support a temperate environment," said Natasha Batalha, a research scientist at the NASA Ames Research Center. "Therefore it would be incredibly interesting to study their atmospheres."

Batalha's specialty, in fact, is finding ways to read exoplanet atmospheres - and building computer models to better understand them.

"That is the next step, the next frontier," she said.

The habitable zone concept is not yet definitive. Small, rocky worlds like ours that orbit other stars are too far away to determine whether they have atmospheres, at least using present-day technology.

That's where teams like the one co-led by Kopparapu and Domagal-Goldman come in. The space telescopes and instruments now on their drawing boards are meant to be powerful enough to peer into these atmospheres and identify the molecules present. That will tell us which gases dominate.

We could find a small, rocky, watery world around a Sun-like star with an atmosphere of nitrogen, oxygen, and carbon dioxide: a little like looking in a mirror.

"To search for life anywhere, we have this 'follow the water' approach," Domagal-Goldman said. "Anywhere you find water on Earth, you find life. Whether it's life on Mars, ocean worlds, or exoplanets, water is the first signpost we're looking for."

For now, the habitable zone remains a kind of first cut in the search for life-bearing worlds.

"The habitable zone is a very useful tool for mission design," said Rhonda Morgan of NASA's Jet Propulsion Laboratory in Southern California.

She studies how to use the data gathered so far on exoplanets to refine designs for future space telescopes.

Over the past quarter century, thousands of exoplanets have been confirmed in a Milky Way galaxy that likely holds trillions. Thousands more will come to light in the years ahead. Tools like the habitable zone will help planet hunters sort through these growing ranks to pick the most likely candidates for supporting life.

"We are in a position now where we can propose a potential, future mission that would be capable of directly imaging an Earth-like planet around a nearby, Sun-like star," she said. "This is the first time in history that the technology has been this close, probably less than 10 years from launch."

Still, we might need something beyond the habitable-zone concept for more extreme cases. It won't help much, for instance, with "weird" life - life as we don't know it. Living things on other worlds might use vastly different chemistry and molecular compounds, or even a solvent other than water.

"This is one of the questions we get from the public often: If there are aliens, how are we going to recognize them if they're really weird?" Domagal-Goldman said. "How do we find what we would consider to be weird life? And how do we make sure not to be tricked by strange, dead planets that look alive - mirages in the desert?"

Life on planets around other stars also might be hidden in a subsurface ocean encased in ice, invisible even to our most powerful space telescopes. Moons of Jupiter and Saturn are known to harbor such oceans, some revealing through remote sensing at least a few of the characteristics we expect for habitable worlds.

Some "exo-moons" also might be habitable worlds, as in the film, "Avatar." But even proposed, future instruments are unlikely to have sufficient power to detect atmospheres of moons around giant exoplanets.

Still, the habitable zone is a good start, a way to zero in on signs of life made familiar by our fellow organisms here on planet Earth.

Cosmic eavesdropping

A shortcut to finding lifeforms like ourselves, of course, would be to intercept tech-savvy communications. Searches for signs of intelligent life have been underway for decades.

In recent years, among NASA scientists, such potential signs have acquired an intriguing new name: technosignatures.

Evidence of a communicative, technological species somewhere among the endless fields of stars could come in the traditional form: signals by radio or optical light waves, or from some other slice of the electromagnetic spectrum.

But scientists imagine many other forms. An exoplanet atmosphere might show signs of synthetic gases, such as CFCs, revealing an industrial species like us.

Or maybe we'll see the glimmer of something like a "Dyson sphere," popularized by physicist Freeman Dyson: an epic-scale structure built around a star to capture the lion's share of its energy.

Such possibilities remain speculative. For now, we have no real answer to a disturbing question from another 20 th century physicist, Enrico Fermi.

Where is everybody?

The question has fueled more than 70 years of debate, but boils down to a simple observation. Our Milky Way galaxy has plenty of stars, plenty of planets, and plenty of time to develop intelligent lifeforms - some of whom might well have had billions of years to develop interstellar travel.

Yet so far, we've seen no sign of such technology, nor heard a peep of conversation. Why is the cosmos so profoundly silent?

"If life had so much time to evolve, why haven't we found it?" Batalha asks, to summarize the question. "Why isn't life just crawling everywhere in the galaxy, or the universe? It could be a combination of a lot of things. Space travel is very difficult for us."

Vast amounts of energy would be needed just to get us to our nearest neighboring star, Proxima Centauri, she said. "It would just be incredibly expensive, and require a lot of resources."

And once we - or some other civilization - reached such a distant destination, she said, another problem would be perpetuating the travelers' existence into future generations.

Experts offer many reasons why somebody, or something, might be out there, yet beyond our detection. On the other hand, the ultra-cautious might remind us that, while a lifeless cosmos seems unlikely, we have exactly zero information one way or the other.

Still, scientists like Kopparapu say they like our chances of finding some form of life, and are hard at work on the telescopes and instruments that could make that future, party-starting epiphany a reality.

"It's not a question of 'if,' it's a question of 'when' we find life on other planets," he said. "I'm sure in my lifetime, in our lifetime, we will know if there is life on other worlds."

# data[].attributes.attachment_link.keywords[]
national aeronautics and space administration

# data[].attributes.attachment_link.authors[].name
By Pat Brennan, NASA's Exoplanet Exploration Program

# data[].attributes.attachment_link.title
Life in the Universe: What are the Odds?

# data[].attributes.attachment_link.description
We don't know when, or even if, we'll find life beyond Earth, but NASA scientists continue the hunt among the thousands of exoplanets confirmed in the galaxy so far.

# data[].attributes.body
Some may say that spending money on space exploration is a waste. That we should wait and help Earth first. As this could be true, we still need space exploration. That is wrong and here's why. Without space exploration we have no hope of finding a new planet which could help support ours. We also would have no GPS, weather apps, and so much more. As important as Earth is, we could find other things in space to help Earth in different ways. This is why we should spend money and valuable resources on space exploration.

# data[].attributes.attachment_link.readable_text
Since NASA's Perseverance Rover landed on Mars last week, it seems like space has been on everyone's minds. There's no doubt about it, space is cool. The idea that we are one tiny speck in the ever-expanding universe is hard to wrap our heads around, but humans are naturally curious creatures so we are inclined to try. The U.S. may be a prominent figure in space exploration but is sending robots into space the best use of our tax dollars, especially with the serious challenges our country faces such as COVID, climate change and income inequality?

Since the founding of NASA in 1958 by President Dwight D. Eisenhower, federal dollars have been going toward researching and exploring space. A little over a decade later, the U.S. landed a man on the moon - or maybe not depending on who you ask. Space exploration is incredible, but we have to remember that NASA's funding comes from the pockets of everyday Americans.

The U.S. is the richest country in the world , but that's not to say it doesn't have problems. In 2020, more than 50 million Americans experienced food insecurity , which increased due to COVID-19. Closer to home, Watauga County experienced a food insecurity rate of 16.8% last year . The pandemic has been hard on Americans and food insecurity is just one example of how people are struggling.

With people struggling to eat in the richest country in the world, is exploring space how our tax dollars should be spent? About of the federal budget is spent on Medicare and healthcare, 5.7% is spent on housing and community and 6.3% on education. Spending for these programs is in the single digits so where is all our money going? The military which receives over half of all discretionary spending. Of course, America's outrageous military spending is a whole different issue. Only 0.5% of the federal budget goes to NASA but 0.5% of a $4.5 trillion budget is a lot of money, $23.3 billion this year to be exact.

$23.3 billion is a lot of money for NASA, which has little to no direct impact on everyday Americans' lives. Sure, space is cool to learn about and the advancement of science and technology is very important, but parents who can't feed their children probably don't care about some rocks on Mars.

NASA should not be a priority when issues such as poverty, food insecurity and homelessness exist in America. Our tax dollars should be spent on us - improving our infrastructure, helping the poor, bettering education and solving climate change. To be clear, government funding for research is very important and NASA should not be abandoned. Knowledge should be accessible and space shouldn't be treated like a personal playground for the ultra-rich. Right now we need to focus on fixing the problems here on Earth before we try to figure out the age-old mysteries of space.

# data[].attributes.attachment_link.description
Since NASA's Perseverance Rover landed on Mars last week, it seems like space has been on everyone's minds. There's no doubt about it, space is cool. The idea that we are one tiny speck in the ever-expanding universe is hard to wrap our heads around, but humans are naturally curious creatures so we are inclined...

# data[].attributes.body
In conclusion we should spend valuable resources for space exploration because it'll give us more information about any dangers in space, it'll give us a chance to find a potential new world, and to see if there is any other life forms out there.