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The Lives, Times, and Deaths of Stars

Who among us doesn’t covertly read tabloid headlines when we pass them by? But if you’re really looking for a dramatic story, you might want to redirect your attention from Hollywood’s stars to the real thing. From birth to death, these burning spheres of gas experience some of the most extreme conditions our cosmos has to offer.

All stars are born in clouds of dust and gas like the Pillars of Creation in the Eagle Nebula pictured below. In these stellar nurseries, clumps of gas form, pulling in more and more mass as time passes. As they grow, these clumps start to spin and heat up. Once they get heavy and hot enough (like, 27 million degrees Fahrenheit or 15 million degrees Celsius), nuclear fusion starts in their cores. This process occurs when protons, the nuclei of hydrogen atoms, squish together to form helium nuclei. This releases a lot of energy, which heats the star and pushes against the force of its gravity. A star is born.

Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

From then on, stars’ life cycles depend on how much mass they have. Scientists typically divide them into two broad categories: low-mass and high-mass stars. (Technically, there’s an intermediate-mass category, but we’ll stick with these two to keep it straightforward!)

Low-mass stars

A low-mass star has a mass eight times the Sun’s or less and can burn steadily for billions of years. As it reaches the end of its life, its core runs out of hydrogen to convert into helium. Because the energy produced by fusion is the only force fighting gravity’s tendency to pull matter together, the core starts to collapse. But squeezing the core also increases its temperature and pressure, so much so that its helium starts to fuse into carbon, which also releases energy. The core rebounds a little, but the star’s atmosphere expands a lot, eventually turning into a red giant star and destroying any nearby planets. (Don’t worry, though, this is several billion years away for our Sun!)

Red giants become unstable and begin pulsating, periodically inflating and ejecting some of their atmospheres. Eventually, all of the star’s outer layers blow away, creating an expanding cloud of dust and gas misleadingly called a planetary nebula. (There are no planets involved.)

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

All that’s left of the star is its core, now called a white dwarf, a roughly Earth-sized stellar cinder that gradually cools over billions of years. If you could scoop up a teaspoon of its material, it would weigh more than a pickup truck. (Scientists recently found a potential planet closely orbiting a white dwarf. It somehow managed to survive the star’s chaotic, destructive history!)

High-mass stars

A high-mass star has a mass eight times the Sun’s or more and may only live for millions of years. (Rigel, a blue supergiant in the constellation Orion, pictured below, is 18 times the Sun’s mass.)

Credit: Rogelio Bernal Andreo

A high-mass star starts out doing the same things as a low-mass star, but it doesn’t stop at fusing helium into carbon. When the core runs out of helium, it shrinks, heats up, and starts converting its carbon into neon, which releases energy. Later, the core fuses the neon it produced into oxygen. Then, as the neon runs out, the core converts oxygen into silicon. Finally, this silicon fuses into iron. These processes produce energy that keeps the core from collapsing, but each new fuel buys it less and less time. By the point silicon fuses into iron, the star runs out of fuel in a matter of days. The next step would be fusing iron into some heavier element, but doing requires energy instead of releasing it.  

The star’s iron core collapses until forces between the nuclei push the brakes, and then it rebounds back to its original size. This change creates a shock wave that travels through the star’s outer layers. The result is a huge explosion called a supernova.

What’s left behind depends on the star’s initial mass. Remember, a high-mass star is anything with a mass more than eight times the Sun’s — which is a huge range! A star on the lower end of this spectrum leaves behind a city-size, superdense neutron star. (Some of these weird objects can spin faster than blender blades and have powerful magnetic fields. A teaspoon of their material would weigh as much as a mountain.)

At even higher masses, the star’s core turns into a black hole, one of the most bizarre cosmic objects out there. Black holes have such strong gravity that light can’t escape them. If you tried to get a teaspoon of material to weigh, you wouldn’t get it back once it crossed the event horizon — unless it could travel faster than the speed of light, and we don’t know of anything that can! (We’re a long way from visiting a black hole, but if you ever find yourself near one, there are some important safety considerations you should keep in mind.)

The explosion also leaves behind a cloud of debris called a supernova remnant. These and planetary nebulae from low-mass stars are the sources of many of the elements we find on Earth. Their dust and gas will one day become a part of other stars, starting the whole process over again.

That’s a very brief summary of the lives, times, and deaths of stars. (Remember, there’s that whole intermediate-mass category we glossed over!) To keep up with the most recent stellar news, follow NASA Universe on Twitter and Facebook.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Women who had ADHD (24%) [were more likely to have attempted suicide] compared to women who had not (3%). 

Men with ADHD were also more likely to have attempted suicide compared to men without ADHD (9% vs. 2%). 

Adults with ADHD were much more likely to have attempted suicide than those without (14.0% vs. 2.7%).

(Study in full)

“Electrostatic force is that which governs the motion of the atoms. It is the force which causes them to collide and develop the life-sustaining energy of heat and light, and which causes them to aggregate in an infinite variety of ways, according to Nature’s fanciful designs, and forms all these wondrous structures we see around us. It is, in fact, if our present views be true, the most important force for us to consider in Nature.”

–Nikola Tesla 

“Tesla, Marvel Of The Future.” Brooklyn Citizen, August 22, 1897.

Do you believe in magic? ✨ ⁣ While appearing as a delicate and light veil draped across the sky, this @NASAHubble image reminds us of the power of imagination. What does this look like to you?⁣ ⁣ In reality, it’s a small section of a Cygnus supernova blast wave, located around 2,400 light-years away. The original supernova explosion blasted apart a dying star about 20 times more massive than our Sun between 10,000 and 20,000 years ago. Since then, the remnant has expanded 60 light-years from its center. ⁣ ⁣ Credit: @ESA/Hubble & NASA, W. Blair; acknowledgment: Leo Shatz⁣ ⁣

"Equipped with his five senses, man explores the universe around him and calls the adventure science."

-Edwin P. Hubble

what is the biggest challenge in the preparation of such a mission and how do you handle it?

Why did I think anyone would like this?

The Search for Starless Planets

While it’s familiar to us, our solar system may actually be a bit of an oddball. Our Milky Way galaxy is home to gigantic worlds with teeny-tiny orbits and planets that circle pairs of stars. We’ve even found planets that don’t orbit stars at all! Instead, they drift through the galaxy completely alone (unless they have a moon to keep them company). These lonely island worlds are called rogue planets.

Where do rogue planets come from?

The planet-building process can be pretty messy. Dust and gas around a star clump together to form larger and larger objects, like using a piece of play-dough to pick up other pieces.

Sometimes collisions and close encounters can fling a planet clear out of the gravitational grip of its parent star. Rogue planets may also form out in space on their own, like the way stars grow.

Seeing the invisible

We’ve discovered more than 4,000 exoplanets, but only a handful are rogue planets. That’s because they’re superhard to find! Rogue planets are almost completely invisible to us because they don’t shine like stars and space is inky black. It’s like looking for a black cat in a dark room without a flashlight.

Some planet-finding methods involve watching to see how orbiting planets affect their host star, but that doesn’t work for rogue planets because they’re off by themselves. Rogue planets are usually pretty cold too, so infrared telescopes can’t use their heat vision to spot them either.

So how can we find them? Astronomers use a cool cosmic quirk to detect them by their effect on starlight. When a rogue planet lines up with a more distant star from our vantage point, the planet bends and magnifies light from the star. This phenomenon, called microlensing, looks something like this:

Imagine you have a trampoline, a golf ball, and an invisible bowling ball. If you put the bowling ball on the trampoline, you could see how it made a dent in the fabric even if you couldn’t see the ball directly. And if you rolled the golf ball near it, it would change the golf ball’s path.

A rogue planet affects space the way the bowling ball warps the trampoline. When light from a distant star passes by a rogue planet, it curves around the invisible world (like how it curves around the star in the animation above). If astronomers on Earth were watching the star, they’d notice it briefly brighten. The shape and duration of this brightness spike lets them know a planet is there, even though they can’t see it.

Telescopes on the ground have to look through Earth’s turbulent atmosphere to search for rogue planets. But when our Nancy Grace Roman Space Telescope launches in the mid-2020s, it will give us a much better view of distant stars and rogue planets because it will be located way above Earth’s atmosphere — even higher than the Moon!

Other space telescopes would have to be really lucky to spot these one-in-a-million microlensing signals. But Roman will watch huge patches of the sky for months to catch these fleeting events.

Lessons from cosmic castaways

Scientists have come up with different models to explain how different planetary systems form and change over time, but we still don’t know which ones are right. The models make different predictions about rogue planets, so studying these isolated worlds can help us figure out which models work best.

When Roman spots little microlensing starlight blips, astronomers will be able to get a pretty good idea of the mass of the object that caused the signal from how long the blip lasts. Scientists expect the mission to detect hundreds of rogue planets that are as small as rocky Mars — about half the size of Earth — up to ones as big as gas giants, like Jupiter and Saturn.

By design, Roman is only going to search a small slice of the Milky Way for rogue planets. Scientists have come up with clever ways to use Roman’s future data to estimate how many rogue planets there are in the whole galaxy. This information will help us better understand whether our solar system is pretty normal or a bit of an oddball compared to the rest of our galaxy.

Roman will have such a wide field of view that it will be like going from looking at the cosmos through a peephole to looking through a floor-to-ceiling window. The mission will help us learn about all kinds of other cool things in addition to rogue planets, like dark energy and dark matter, that will help us understand much more about our place in space.

Learn more about the Roman Space Telescope at: https://roman.gsfc.nasa.gov/

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Dr. Beach’s Top 10 Beaches of 2021

For more than 30 years, Dr. Beach, aka Dr. Stephen Leatherman, has created an annual Top 10 Beach list. A professor and coastal geomorphologist at Florida International University, Dr. Beach factors in 50 different criteria including water color, sand softness, wave size, water temperature and more.

As we get ready to launch Landsat 9 this fall, we’re taking a tour of Dr. Beach’s Top 10 US beaches of 2021 as seen by Landsat 8.

10. Coast Guard Beach, Cape Cod, Massachusetts

Coast Guard Beach is located just north of the remote Nauset Inlet on Outer Cape Cod, Massachusetts. Except for the picturesque old white Coast Guard station that still sits atop the glacial bluffs, there is no development here; the best way to reach this beach is by bicycle from the Salt Pond Visitor’s Center or shuttle bus.

First mapped by Champlain in 1605, the shifting sands of this inlet are clearly visible in the Landsat image. This location is also at the point where the glacial sea cliffs transcend into a barrier beach (e.g., sand spit) that provides protection for the lagoon and development of lush salt marshes.

“In my early days as a Professor at Boston University and later at the University of Massachusetts at Amherst, I spent many summer and some winter-time days conducting scientific studies along this barrier beach.” – Dr. Beach

Landsat 8 collected this image of Coast Guard Beach on May 1, 2021.

9. Beachwalker Park, Kiawah Island, South Carolina

Beachwalker Park is a public beach located on the southern part of Kiawah Island, South Carolina. This barrier island in the Charleston area is 10-miles long and features a fine grained, hard-packed beach that can be traversed easily by bicycle.

This Landsat image shows a huge accumulation of sand as a series of shoals on the south end of the island, which can be reached from Beachwalker Park. These sandy shoals will eventually coalesce, becoming an extension of the sand spit that is the south end of Kiawah Island.

“In the early 2000s, I served as the beach consultant to the Town of Kiawah Island because their world-famous golf course on the north end was being threatened by severe erosion. It was necessary to artificially bypass some sand on the north end of the island so that the normal flow of sand along the island was reinstated, saving the outermost link of this PGA golf course.” – Dr. Beach

Landsat 8 collected this image of Beachwalker Park on April 9, 2021.

8. Coronado Beach, San Diego, California

Coronado Beach in San Diego is the toast of Southern California with some of the warmest and safest water on the Pacific coast. This 100-meter-wide beach is an oasis of subtropical vegetation, unique Mediterranean climate, and fine sparkling sand.

The harbor serves as a major port for the Navy’s Pacific fleet, the home port for several aircraft carriers. The docks and the crossing airplane runways for the Naval base are visible in this Landsat image.

“I really enjoy visiting this beautiful beach as well as having lunch and drinks, taking advantage of the hotel’s beachside service.” – Dr. Beach

Landsat 8 collected this image of Coronado Beach on April 23, 2020.

7. Caladesi Island State Park, Dunedin Clearwater, Florida

Caladesi Island State Park is located in the small town of Dunedin on the Southwest Florida coast. The stark white undeveloped beach is composed of crystalline quartz sand which is soft and cushy at the water’s edge, inviting one to take a dip in the sparkling clear waters.

While island is still in the Park’s name, Caladesi is no longer a true island as shown on the Landsat image--it is now connected to Clearwater Beach.

“Caladesi is located in the Tampa area, but it seems like a world away on this getaway island.” – Dr. Beach

Landsat 8 collected this image of Caladesi Island State Park on April 9, 2021.

6. Duke Kahanamoku Beach, Oahu, Hawaii

Duke Kahanamoku Beach is named for the famous native Hawaiian who was a big-board surfer and introduced surfing as a sport to mainland Americans and indeed the world.

One of the prominent features on this Landsat image is Diamondhead with its circular shape near the coast. This large cone of an extinct volcano provides the iconic backdrop for photos of Waikiki Beach.

“This is my favorite spot at the world-famous Waikiki Beach where you can both play in the surf and swim in the calm lagoonal waters.” – Dr. Beach

Landsat 8 collected this image of Duke Kahanamoku Beach on May 17, 2020.

5. Lighthouse Beach, Buxton, Outer Banks of North Carolina

Lighthouse Beach in the village of Buxton is located at Cape Hatteras, the most northern cape in the Outer Banks of North Carolina. This lifeguarded beach is the number one surfing spot on the US Atlantic Coast as the large offshore sand banks, known as Diamond Shoals, cause wave refraction focusing wave energy on this beach.

The Landsat image shows the seaward growth of south flank of Cape Hatteras as evidenced by the parallel lines of beach ridges.

“It is fun to walk down the narrow sand spit, more exposed at low tide, as waves are approaching from both directions because of the bending of the waves.” – Dr. Beach

Landsat 8 collected this image of Lighthouse Beach on May 3, 2020.

4. St. George Island State Park, Florida Panhandle

St. George Island State Park, located on the Florida panhandle and far from urban areas, is a favorite destination for beachgoers, anglers and bird watchers as nature abounds. Like other beaches on the panhandle, this long barrier island has a sugary fine, white sand beach.

In this Landsat image, St. George can be seen north of the bridge that links this barrier island to the mainland. The enclosed bay behind St. George Island is fairly shallow and the water much less clear as shown on the Landsat image, but it is not polluted.

“Besides swimming in the crystal-clear Gulf of Mexico waters, I enjoy beachcombing and shelling. While this island was hit hard in 2018 by Hurricane Michael, it has substantially recovered as there was little development to be impacted.” – Dr. Beach

Landsat 8 collected this image of St. George Island State Park on October 13, 2020.

3. Ocracoke Lifeguard Beach, Outer Banks of North Carolina

Ocracoke Lifeguarded Beach at the southern end of Cape Hatteras National Seashore was the first seashore to be incorporated into the National Park Service system.

The Landsat image shows Ocracoke to the north as separated by an inlet from Portsmouth Island. The village of Ocracoke was built at the wide area of the island where it was protected from oceanic waves during coastal storms which include both winter nor’easters and hurricanes.

“Ocracoke was once the home of the most infamous pirate Blackbeard and is still a very special place—my favorite getaway beach.” – Dr. Beach

Landsat 8 collected this image of Ocracoke Lifeguard Beach on May 3, 2020.

2. Cooper’s Beach, Southampton, New York

Cooper’s Beach in the tony town of Southampton on the south shore of Long Island, New York is shielded from the cold Labrador current, making for a fairly long summer swimming season. The white quartz sand is medium to coarse grained with some pebbles, making the beach slope fairly steeply into the water.

This Landsat image shows the fairly large coastal pond named Mecox Bay to the east with Shinnecock Inlet and Bay also displayed to the west. Coopers Beach is hundreds of yards wide, made of grainy white quartz sand and is backed by large sand dunes covered by American beach grass.

“I spent several decades conducting scientific studies of this very interest oceanic shoreline because it is so dynamic and the beachfront real estate so expensive. Some of the most gorgeous and expensive residential houses in the United States are located in the world-famous Hamptons.” – Dr. Beach

Landsat 8 collected this image of Coopers Beach on August 30, 2019.

1. Hapuna Beach State Park, Big Island Hawaii

Hapuna Beach State Park is a white coral sand beach that resides in a landscape dominated by dark brown lava flows on the Big Island of Hawaii. The crystal-clear water is perfect for swimming, snorkeling, and scuba diving during the summer months in contrast to winter big-wave days when pounding shorebreaks and rip currents make swimming impossible.

Hapuna and the other pocket beaches appear as an oasis in this otherwise fairly bleak landscape except for the areas irrigated as prominently shown on the Landsat imagery by the green vegetation.

“This volcanically active island is the only place that I know where you can snow ski at the high mountain tops and water ski in the warm ocean water on the same day.” – Dr. Beach

Landsat 8 collected this image of Hapuna State Park on January 5, 2021.

What’s your favorite beach?

View Dr. Beach’s 2021 picks and see Landsat views of these beaches over time.

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