What Is A Variable Star?

On August 3, 1596, German astronomer David Fabricius need a reference star while observing the planet Mercury and looked to Omicron Ceti, an unremarkable third-magnitude star nearby. Several weeks later, Fabricius noticed that the star had increased in brightness by one magnitude, and then as he continued his observations into October, the star disappeared entirely from his view. But when Fabricius looked in the sky again on February 16, 1609, the star was back in its place. Omicron Ceti soon received a new name, “Mira,” meaning “astonishing” in Latin.

Fabricius had discovered one of the first-known variable stars, and today there are more than 200,000 known variables, including tens of thousands in the Milky Way alone. Variable stars are stars that change in brightness or in some other characteristic, such as the spectrum in which they shine, over time.

There are many reasons why a star may change over time: Internal forces cause some stars to swell and shrink. Other stars will appear to dim when they are eclipsed by a fainter companion and brighten as that companion moves past. Mira variables, named after Fabricius’s star, are red giants in the late stages of their evolution, now expanding and contracting, but in a few million years, they’ll have become white dwarfs.

Cepheid variable star V1 (Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA))

Cepheid variables, another type of pulsating star, have proven to be more than just stellar oddities–astronomers have been able to use these stars to make monumental discoveries about our universe. Henrietta Swan Leavitt, one of the “Harvard computers” at the turn of the last century, showed that there was a relationship between a Cepheid variable star’s brightness and the time it took for that star to cycle through its brightening-dimming pattern. This discovery led astronomers to develop a method for determining the distance of a Cepheid variable based on its brightness. With that yardstick, Edwin Hubble was able to show that two stars (including the one in the photo above) were too far away to be in the Milky Way and thus proved that our galaxy was not the only one in the universe. Hubble also used Cepheid variables to show that the universe is expanding.

Backyard astronomers can observe and even discover variable stars–it just takes a bit of knowledge and a lot of patience. If someone thinks they’ve found one, the American Association of Variable Star Observers recommends first checking the International Variable Star Index (VSX) as well as other star catalogs to see if it is already known. If it’s not in one of the indices, the discoverer should double check their data and then they can submit it to the VSX. There are likely millions of variable stars in the sky, so there’s plenty of opportunity for future discovery.

Managing Your Caffeine Addiction With Your Phone

Caffeine is hard to avoid. It’s in coffee, tea, soft drinks, and chocolate. One estimate of global consumption tallies it at 120,000 tonnes per year, or about one caffeinated beverage per person per day. Caffeine is a mild stimulant, helping to restore alertness and reduce fatigue. And while overconsumption can have some pretty bad effects (starting with the jitters and moving on to mania, depression, and hallucinations), daily consumption of small amounts can be of real help. It’s no wonder that so many of us have become addicted to the stuff.

And that addiction is real. If you’re dependent on the stuff, you’ll feel the effects of not consuming caffeine pretty quickly–headaches, sleepiness, fatigue, irritability, cloudiness of your thoughts, even depression. That addiction, however, doesn’t mean that you’re immune to caffeine’s ability to keep you awake at night if the levels in your blood are too high when you try to sleep.

But a new iOS app from researchers at Penn State University promises to help the caffeine addict manage their consumption. Caffeine Zone 2 (available in a free version with ads) lets you record your consumption of caffeinated products, calculates the amount of caffeine you’ve consumed, and plots out the level of caffeine in your blood over time. Drink a cup of coffee too late in the day and you’ll quickly see that trying to go to sleep may be a problem.

And the user can adjust optimal caffeine levels in the app as they learn more about what works for them. The default settings are based on peer-reviewed research that shows that people are most alert when the caffeine levels reach 200 to 400 milligrams. The researchers took those results and set the app to alert you that trying to sleep when your blood levels are higher than 100 milligrams, but more sensitive people can change that if needed.

I can’t say whether this app will be useful for me (I’ve pretty much figured out that one cup of tea in the morning is enough to get me going but another in the afternoon will keep me up at night), but I can see that it might be good for someone who hasn’t yet determined their own patterns. Or if a person is consuming far too much caffeine in their day (I’m thinking of a former co-worker who drank cups and cup of coffee throughout his day), it might help to point out when their caffeine levels have reached toxic levels.

What Could Be More Annoying Than Pigeons? Cockatoos

If readers haven’t figure it out yet, I’m headed to Australia soon. I’ve been there before, and one of the places I’m looking forward to visiting again is the Royal Botanic Garden in downtown Sydney.

Sulfur-crested cockatoos in the Royal Botanic Garden, Sydney (photo by Sarah Zielinski)

This being Australia, the wildlife is different from gardens in the United States. Sure, there are pigeons, but the more annoying birds in the Sydney gardens were the sulfur-crested cockatoos. In the U.S., these birds are long-lived and demanding pets with a loud, distinctive call (adapted to the needs of wild birds calling across forests) and a penchant for chewing wood. In Australia, these birds are often pests that destroy crops and timber structures.

The Royal Botanic Garden has plenty of signs warning people not to feed the birds and other wildlife. As explained on the garden’s Web site, there are several reasons for this rule:

  1. Human food is not healthy for the animals and can even be deadly. Birds that eat too much of our food can suffer from bone deformities, increased susceptibility to disease, and a reduced ability to deal with cold weather (and it does get cold there in the winter).
  2. Feeding the wildlife makes the animals lazy and more dependent on humans than their own abilities.
  3. And handfeeding makes for aggressive animals.

That last point can be seen firsthand if you are stupid enough to feed the cockatoos. When I visited the garden, I watched as one tourist handfed the cockatoos and her friend photographed them. It was cute until the woman feeding the birds couldn’t get rid of them. They landed on her arms and head and wouldn’t leave no matter how much she swatted at them (kind of like what’s going on in the video below).

It’s not as if you need to lure these birds with food to get a good photo of one. These cockatoos feed on the ground (they like seeds and insects) and all it takes is a little patience to get a great shot.

Four Stories To Read This Week

From Inside Lions and Leviathans, Anatomist Builds a Following (New York Times): In this profile by Carl Zimmer, we learn why you may not want to sit next to Joy Reidenberg on a plane after she’s been working. Plus, how to dissect a whale.

Bright-Sized: Skull Study Shows Eye-Sockets Have Grown Larger at Higher Latitudes (Scientific American): An analysis of the eye sockets in human skulls finds that people in northern latitudes, where there is less sunlight, may have evolved bigger eyeballs.

Cancer is just as deadly as it was 50 years ago. Here’s why that’s about to change (io9.com): A good and thorough backgrounder on the science of cancer that explains how researchers have changed their thinking about the disease and why there may never be a “cure.”

The Frog of War (Mother Jones): Biologist Tyrone Hayes discovered that atrazine, a top-selling herbicide, messes with sex hormones, most famously turning male frogs into females, and then started a (sometimes-crazy) feud with the chemical’s maker Syngenta.