Category Archives: Astronomy

Chandra G292.0+1.8 Supernova Remnant


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.



Asteroid Day, June 30

Tunguska Event - Simulated
Tunguska Event – Simulated


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.


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.



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.


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.



The Solar System (to scale)

Solar System

Sun and planets, to scale. But the distances between them are not.

We’ve all seen the numbers that describe the solar system, and we can understand them with graphics like the two in this post. Earth has a diameter of about 8,000 miles, but the moon is only about 2,000 miles across. Jupiter, on the other hand, is about 84,000 miles across; and the sun is a whopping 836,000 miles in diameter.

These huge numbers are all rounded to the nearest thousand to make them easier to visualize. We can easily see that Jupiter is more than ten times the diameter of earth; and the sun, more than 100 times. The moon (not shown) is smaller, being only about a quarter of earth’s diameter.

Planets to scale

Venus is almost as large as earth, but Mars is smaller, and Mercury is smaller still. At 70,000 miles, Saturn is a little smaller than Jupiter; and Uranus and Neptune are considerably smaller, but still far larger than earth.

Did I get you confused yet? No? Good. It’s really not hard. These number are big, but barely of a size range we can visualize.

What’s hard is picturing the distances between these objects. We don’t usually see them because they are too vast to fit on a screen or page. If we do see the space, the planets will be microscopic. What’s worse is that these distances between the objects are so huge it’s impossible for us to visualize them.

Consider these approximate distances from the sun:

  • Mercury: 36,000,000 (35 million miles)
  • Venus: 67,000,000 (67 million miles)
  • Earth: 93,000,000 (93 million miles)
  • Mars: 142,000,000 (142 million miles)
  • Jupiter: 484,000,000 (484 million miles)
  • Saturn: 889,000,000 (889 million miles)
  • Uranus: 1,800,000,000 (1.8 billion miles)
  • Neptune: 2,800,000,000 (2.8 billion miles)
  • Pluto: 3,700,000,000 (3.7 billion miles)
  • Sedna: 7, 100,000,000 to 87,000,000,000 (7.1 billion mi to 87 billion mi)

Orbit of SednaYeah, I know Pluto isn’t a planet; but it’s still part of our solar system. So is Sedna. It’s a minor planet so small and so far away it wasn’t even discovered until 2001. It has a highly elliptical orbit way out beyond the orbits of the major solar system bodies. (Sedna has the red orbit in the picture; Pluto has the outer pink one. [Wikipedia calls it purple.] All the planets are crammed inside.)

Like the diameters of the planets, these numbers are also approximate. Since planetary orbits are not exactly circular, they represent the approximate average orbit of each planet.

At the far end of its orbit, Sedna is so incredibly far away it would take more than 141,000 years to drive that distance at 70 mph non-stop.

The objects in both pictures are drawn to scale, but the spacing obviously is not.

Here’s a video that actually shows the distances between the objects in the solar system TO SCALE. I’m sorry I can’t embed it, so you’ll have to click the link if you want to see it. Please do! It’ll be worth your effort.

This video shows the real size of the solar system by, in effect, placing 1,074 screens side by side. If you could print it out at 300 dpi, the paper would have to be 475 feet wide and earth would be invisible.

You’ll find the sun on the left and scroll right to find everything else. The scale is that our moon is one pixel. It’ the smallest dot possible on your screen. So earth is about 4 pixels across; still a very small dot. And everything else is to scale. Including the empty spaces between objects.

Get prepared for a LOT of empty space. It’ll blow your mind!



Magnificent New View of Earth from Lunar Orbit

December 2015 Unique view of Earth from the LRO in orbit around the moon
December 2015 Unique view of Earth from the LRO in orbit around the moon

I couldn’t resist.

I didn’t intend to make a science post until I had the site looking good, but this was just too good to wait. NASA’s Lunar Reconnaissance Orbiter (LRO) recently captured this unique view of Earth from the spacecraft’s vantage point in orbit around the moon. We see the “limb” of the moon (as the visible edge of an astronomical body is called) underneath our planet as it hangs in space showing Africa, the continent where our species evolved, through the clouds.

Earthrise blue marble picture

“The image is simply stunning,” said Noah Petro, Deputy Project Scientist for LRO at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The image of the Earth evokes the famous ‘Blue Marble’ image taken by Astronaut Harrison Schmitt during Apollo 17, 43 years ago, which also showed Africa prominently in the picture.”

This new picture shows a fuller earth and brighter, richer colors. (I almost said closer, but it isn’t. It just looks closer. Both pictures were taken from lunar orbit, so the distance is approximately the same.) Regardless, it’s wonderful!

Click the link below to get your full-size original to use for wallpaper on your monitor or whatever else you might want it for.

An interesting tidbit is that there is actually no such thing as earthrise on the moon. It’s an illusion. Since the moon rotates once on its axis every time it orbits earth, the same side of the moon always faces our planet. It wobbles a few degrees, but not enough to notice. That’s why we always see the same “man in the moon.” Or the same “rabbit in the moon,” if your imagination runs that way.

From the position near the moon’s surface where the original picture was shot, earth always seems to hang in the sky like that. And the new picture was shot from a similar position. From behind the moon, earth would never be visible.

Lots of Variety Here

My posts will vary from time to time. Before the end of the year, I’ll probably put up links to a series of new evolution videos. Other times, I’ll write articles ranging from very short to 700 or 1,000 words. Still other times, I’ll post a link to something somebody else already said better than I can. I’m not proud.

Whatever it takes to make science both simple and interesting, that’s what I intend to do. I won’t try to post something every day, though. Once or twice a week will be more usual. And I’ll nearly always include one or more links to source materials.

So don’t change that dial. Stay tuned for lots of great simple science stuff. And be sure to sign up for email notifications.

By the way, we’ll have this site looking like it ought to look really soon. I promise. You’ll be proud for anybody to see it on your screen.