Category Archives: Astrophysics

Chandra G292.0+1.8 Supernova Remnant

g292_v2_1

Thirty-six light years across and still growing, it was born in fire and wind about 20,000 light years from earth when a star exploded and sent dust and gas flying through the galaxy at tremendous speed. Some 1,500 or 2,000 years later, the Chandra X-ray Observatory captured this beautifully detailed image and released it to the public on October 23, 2007. This is the Chandra G292.0+1.8 supernova remnant, located in our galaxy, in the constellation Centaurus.

Constellations like Centaurus aren’t real clusters of stars. They are really unrelated stars at different distances from earth that just happen to look close together. This group of unrelated stars looked to some of our ancestors as if they outlined a centaur,  a legendary creature said to be half human and half horse, so they called the constellation Centaurus. Apparently, they had great imaginations!

Spiral Galaxy NGC 6744
Spiral Galaxy NGC 6744

But galaxies are real clumps of stars. Huge swirling clumps of different shapes containing billions of stars each. The Milky Way is a pinwheel-shaped galaxy 100,000 light years across, known as a spiral galaxy. We can’t take a picture of the whole Milky Way, because we live inside it; but it would look very much like the NGC 6744 galaxy shown here. Spectacular!

There isn’t enough time in an astronomer’s life to count that many stars. Besides that, many stars are hidden behind clouds of gas and dust. But various estimates are that our galaxy, the Milky Way, contains between 100 billion and a trillion stars. (The most common estimate seems to be about 200 billion, or 200,000,000,000 stars.)

You couldn’t count that many stars if you lived 1,000 years! Even if you COULD see them all from earth.

Anway, Chandra G292.0+1.8 is physically located in our Milky Way galaxy, in the direction of  Centaurus. This beautifully detailed Chandra composite shows the rapidly expanding shell of gas formed by the explosion.

A pulsar located slightly below and to the left of the center is believed to be the star that exploded to form the nebula. While it would normally have been at the center of the remnant, recoil from the lopsided explosion may have kicked the pulsar in this direction.

The long white line running from left to right across the center is called the equatorial belt, and was probably formed when the star expelled material from around its equator shortly before it died.

Our universe is filled with incredible violence and chaos, but it produces some of the most beautiful and fascinating structures we can imagine.

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Asteroid Day, June 30

Tunguska Event - Simulated
Tunguska Event – Simulated

Tunguska

Today is Asteroid Day, the 108th anniversary of the “Tunguska Event,” the largest asteroid impact in recorded history, when a roughly 40 meter-wide (125 feet) rock exploded high in the air over Tunguska, Siberia, in 1908. The explosion released the power of 185 Hiroshima-type atomic bombs (though without the deadly radioactivity) and flattened trees for many miles.

An asteroid, also known as a “meteoroid,” is simply a chunk of rock or iron shooting through space, usually in an orbit around the sun. Most of them, including the very largest, orbit in the so-called “asteroid belt” between Mars and Jupiter; but a relative few wander the solar system in essentially all kinds of possible orbits. And a “relative few” can be a very large number when we’re talking about asteroids.

Trees felled by the Tunguska Asteroid explosion Jun 30, 1908
Trees felled by the Tunguska Asteroid explosion Jun 30, 1908

Fortunately, there were no known human casualties of the Tunguska Event because the area was uninhabited. It was even several years before scientists could even get to the site to see what had happened.

Asteroid Day was designated, beginning last year, as a way to educate people about the danger imposed by near-earth asteroids. The more people who understand the danger, the more likely our leaders will be to put resources into finding ways to prevent it.

The Panoramic Survey Telescope in Hawaii is dedicated to finding asteroids that cross earth’s orbit, called “earth crossers” or “near earth asteroids,” because some of them could pose serious dangers to us. So far, it has found 10,000 of them and astronomers estimate there are literally several million more. The 10,000th one, found June 18, 2013, and designated Asteroid 2013 MZ5, was 1,000 feet (300 meters) across. If it were to strike our planet, it could unleash more than 400 times as much destructive power as the Tunguska Event. Fortunately, it’s path does not directly intersect with ours for the foreseeable future.

Chelyabinsk

However, it was only four months earlier, on February 15, 2013, that the Chelyabinsk Meteor entered Earth’s atmosphere over the southern Ural region of Russia with a speed of approximately 19 kilometres per second (41,000 mph). Its light was brighter than the Sun, and it was visible up to 100 km (60 mi) away. Some witnesses even felt intense heat from the fireball.

The explosion shattered windows and did other damage, injuring at least 1,500 people enough to seek medical help.

This was a small one, and it approached earth from he direction of the sun, making it difficult to see. For these reasons, nobody knew it was coming until it streaked across the skies of Chelyabinsk.

Bigger ones are out there. They’ve hit our planet before, but it’s usually hard to find the craters because they’ve been destroyed or hidden by erosion. It’s easier to see that the moon is covered with craters from the bombardment it receives. Earth gets the same punishment from the sky, but the atmosphere burns up the small ones and soon degrades the craters the big ones leave.

The asteroid that finished off the dinosaurs 66 million years ago left a crater  more than 180 kilometers (110 miles) in diameter and 20 km (12 mi) deep near Chicxulub, Mexico; but it is mostly under water. The asteroid itself was at least 10 km (6 mi) in diameter.

Meteor Crater

Possibly the best preserved asteroid crater is Meteor Crater, 37 miles (60 km) east of Flagstaff, Arizona. It is smaller, approximately 1.2 k (3/4 mi) in diameter and 170 m (560 ft) deep, as seen below, and was formed by a nickel-iron meteorite about 50 meters (160 feet) across about 50,000 years ago. It was about 50 m (160 ft) deeper before it eroded.

Meteor Crater in Arizona
Meteor Crater in Arizona

The Danger

It’s easy to see that an asteroid this size could wipe out a small city and wreak havoc on a much larger area. Fortunately, there were no humans in North America that long ago; but it could happen just as easily today.

The Tunguska Asteroid could have destroyed a state or a small country.

The Solution

The dinosaurs could not help themselves, but we can. By finding the rest of the asteroids that might endanger our planet, we can know when the next one is coming and where it will strike before it gets here.

Using modern space technologies we can deflect an asteroid endangering the earth before it gets here and save ourselves. But it requires resources to locate the dangerous ones and design, build, and test the protection.

Remind our national leaders, we don’t want to go the way of the dinosaur.

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Riding a Beam of Light

Riding Light from Alphonse Swinehart on Vimeo.

In our terrestrial view of things, the speed of light seems incredibly fast. But as soon as you view it against the vast distances of the universe, it’s unfortunately very slow. This animation illustrates, in realtime, the journey of a photon of light emitted from the surface of the sun and traveling across a portion of the solar system, from a human perspective.

I’ve taken liberties with certain things like the alignment of planets and asteroids, as well as ignoring the laws of relativity concerning what a photon actually “sees” or how time is experienced at the speed of light, but overall I’ve kept the size and distances of all the objects as accurate as possible. I also decided to end the animation just past Jupiter as I wanted to keep the running length below an hour.

Vimeo

You’re riding on a photon, a single “particle” of light.

You leave the sun’s surface, flying away at (naturally) the speed of light, or approximately 186,000 miles/second (299,792,458 meters/second).

You’ll cross the orbits of Mercury and Venus. After 8 minutes 17 seconds, you’ll finally cross the orbit of earth and begin heading toward Mars. By the time your first hour has gone,  you’ll have flown almost seven billion miles. Far past mighty Jupiter and heading toward Saturn.

The hour-long video ends with you heading for Saturn, Uranus, Neptune, and the stars.

Here’s what you see as you look backwards toward the sun, getting farther and farther away.

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