Tag Archives: milky way

Washed Out

Earlier this summer, I visited the Hayden Planetarium in New York City. It was a joy to see fellow astronomers present a live tour of the night sky in a state-of-the-art facility. The best moment of any planetarium show always comes midway through, once everyone has adjusted to the low light and is starting to get acquainted with the constellations twinkling above. The narrator pauses. The lights fade further still. As the dome transforms to inky black and countless new stars obscure once-familiar constellations, the audience audibly gasps.

A show at the Hayden Planetarium. Image: amnh.org.

When I ask students in my introductory astronomy class if they have seen the Milky Way, very few hands pop up. The night sky as our ancestors saw it is a novelty, a luxury; something foreign to gasp at.

That night in Manhattan, the planetarium show was followed by telescope viewing. As I headed outside and looked up to get my bearings, I felt very disoriented: in spite of mostly-clear skies, I could count the number of visible stars on my hands. And two of those were actually planets. I was struck by Neil deGrasse Tyson’s embarrassing admission that, as a child, seeing a dark night sky while camping reminded him of the Hayden Planetarium.

It is one thing to read about pervasive light pollution. Yes, our cities are growing and getting brighter, and it is increasingly impossible to see very many stars at night. Intellectually, I know this, and I know that it is a huge waste of money and energy; a large-scale, slow-growing problem with no easy fix. But experiencing it is something different altogether. It is deeply distressing. I fear we are literally blinding ourselves from the Universe’s past and our species’ future when we block our only window to the starry heavens above.

Light pollution in North America as viewed from space. Image: SPL / Barcroft Media

Also this summer, I traveled to northern Vancouver Island in Canada. My room faced northeast, toward the water, with expansive windows and no blinds or curtains. Night was dark. Not “it’s difficult to see, can you shine a light over this way?” dark, but truly, utterly, all-encompassingly DARK. There was no telltale glow on the horizon of some distant city or rogue gas station. There was no streetlight casting orange light in an unwanted direction.

One cloudless night as I lay in bed, I could see stars twinkling out the window, and woke my husband to drag him outside. We reveled in proper, glorious darkness. Like the Hayden Planetarium, there were so many stars that familiar constellations were hard to pick out. The sunrise, early though it was, reset my circadian clock. I reconnected with the night and felt whole.

We have a natural tendency to equate light with good, with safety and security, and with happiness. But we have slowly eased into modern life with an overabundance of this good thing. (Not to mention: studies have demonstrated that more light does not equal more safety.) I do what I can in my personal life to get lots of natural light during the day, use fewer lights at night, and take the irritating blue glow out of my backlit screens.

Of course, while it doesn’t make sense to shine excessively bright lights, it doesn’t make sense to turn them all off, either. Smart solutions exist for dark-sky friendly light fixtures. But I fear it will take a health or energy crisis to make us truly examine how we wash out the night. Until then, we must cherish every sliver of darkness we can find.


When Stars Explode

There’s a new supernova in the skies! Last week, students at the University of London Observatory discovered a strange bright spot in nearby galaxy Messier 82 (M82) during a routine observing training session. As undergraduate student Tom Wright put it, “One minute we’re eating pizza then five minutes later we’ve helped to discover a supernova. I couldn’t believe it.”

Words. Image credit UCL/University of London Observatory.
Two images of galaxy M82. The bottom one shows the location of the new supernova, dubbed SN 2014J. The overall galaxy appears dimmer in the bottom picture because the exposure time was shorter, so less light had time to reach the camera. Image from UCL/University of London Observatory.

What’s the big deal about a supernova? Well, to start with, all the elements in the Universe were formed deep inside stars, and spewed out into space through supernova explosions like this one. Take a moment to let that sink in.

This supernova is a special variety called “Type Ia” (type one-A). This means it is caused by a very dense white dwarf star collecting more mass than it can support and eventually going BOOM! We know this because we see signatures of telltale elements like Silicon in the spectrum of the explosion.

Type Ia supernovae are particularly useful because they are all physically very similar—white dwarf stars can only handle so much mass before they explode—so they are all roughly the same brightness. Astronomers love things that are all the same brightness, because they let us determine distances. How? Let’s pretend you’re staring into a huge, dark, empty room containing nothing but a handful of 100-Watt light bulbs. (Not a bad analogy for an astronomer’s life, really…) You’d like to know how far away the light bulbs are, but you don’t have a measuring tape, plus the room is really big. However, you know how much light each bulb is putting out (100 Watts), so you can figure out the ones that look dimmer are actually farther away. We call the 100-Watt light bulbs of the Universe, such as Type Ia supernovae, “standard candles” because they let us determine distance like this.

If you live in the Northern hemisphere and have access to good binoculars or a telescope, you can try seeing SN 2014J for yourself! It is close to peak brightness, and should be visible for another couple of weeks—the blink of an eye from an astronomical perspective.

Look for galaxy M82 with binoculars or a telescope near the dipper portion of the Big Dipper in Northern hemisphere skies. Image from Universe Today.

Even if you can’t spot the supernova in M82, the galaxy itself and neighboring galaxy M81 are a lovely sight. They’re also a great example of how light can be deceiving. The image below shows two images of these galaxies: one taken with visible light (inverted so the galaxies appear dark on a light background), and one taken with radio light. There is all kinds of gas and material connecting the galaxies together that you can’t see with your eye!

Two views of galaxies M81 (the larger one) and M82 (the smaller one above it). These pictures show the same region of space in two different flavors of light. The galaxies appear as two isolated collections of stars in visible light (left), while the multicolor radio image (right) shows gas connecting the galaxies. Observations like these are used to figure out how galaxies have interacted gravitationally in the past. Image from the SEDS Messier Catalog.

What I find particularly mind-boggling is how a galaxy some 12 million light years distant is “nearby” on a cosmic scale. Because light doesn’t travel instantaneously, we are seeing this supernova as it happened 12 million years ago. In contrast, every star in the night sky is located in our own Milky Way galaxy, which is about 100,000 light years across, so the light from these stars (and the planets orbiting them!) is “only” delayed by hundreds or thousands of years, not millions. If the planets in our Solar System are our next-door neighbors, and stars in our galaxy with their own planets are other cities, then M82 is an entirely different country.

I can’t help but wonder… is some alien civilization in our galaxy witnessing this distant explosion just as we are, at this very moment? Are intelligent creatures on a planet we have recently discovered also turning their telescopes to the heavens to study this supernova and learn more about the Universe we share?

Gazing up from Idaho

Last week, I volunteered at the summer camp I grew up attending outside Coeur d’Alene, Idaho. It’s in a dark enough spot that you can easily see the Milky Way on a moonless night. I tend to spend a week there around the same time each summer, so whenever I visualize the night sky, 47 degrees north latitude on a lake in early August is my reference.

Ten years ago, as a high school student, I raised money to install special shields on the light fixtures at camp to reduce light pollution. The idea is simple: instead of shining light up into the sky where it is wasted and obliterates our view of the stars, redirect the light down onto the ground where it is needed.

Is this how the light shields are supposed to work?
Top: Before and After
Bottom: Is this how the light shields are supposed to work?

Light pollution is an ever-increasing problem, unfortunately. Surprisingly few people have ever seen the Milky Way. Believe it or not, this is what the night sky is supposed to look like:

Milky Way from Ghost Ranch, New Mexico in July 2012.
Milky Way from Ghost Ranch, New Mexico in July 2012.

Pitch black with innumerable stars, a clumpy band of even MORE stars stretching across, with perhaps a satellite or two moving steadily along.

Globular cluster M13 (image credit: APOD).
Globular cluster M13 (image credit: APOD).

This past week in Idaho, I was able to see three noteworthy things in the night sky. First, I pointed a little 6-inch telescope at M13, the globular cluster in Hercules. It took a while to find, because the telescope has no electronic controls and you have to point and track manually.

Second, we were treated to an early sprinkling of Perseid meteors from the meteor shower that peaks on August 12 each year. If you’re curious about this and want to see some meteors too, read all about it here.

Finally, I spotted the International Space Station three times. I get email alerts whenever the ISS passes over my home in Las Cruces, but I didn’t think to check Coeur d’Alene. The station is pretty bright, though, moves across the sky more slowly than an airplane, and doesn’t blink or twinkle. Plus, if it will be visible in southern New Mexico one night, it’s likely to be visible in northern Idaho not too long before or after. You can see when the ISS will be visible from your location by heading over to Spot The Station. I glimpsed the station once on Sunday night, August 4, and announced its appearance during a lovely campfire another night.

A night or two later, I saw something awfully similar… with a fainter light closely trailing it across the sky. What? Was I just tired, and this was two strange looking airplanes? No! After a twitter query and some googling, it turns out the fainter light was almost certainly the HTV-4 Japanese Cargo Ship. It was captured by the station hours later.

What I learned at summer camp: turn off the lights (or go somewhere properly dark), keep looking up, and who knows what wonders you might see.