Ask a Scientist

Dr. Michael Shara is an astrophysicist from the American Museum of Natural History.

On February 22, 2006, students and teachers interviewed Dr. Michael Shara, an astrophysicist at the American Museum of Natural History. To learn about supernovas, the newest "planet," and how a lava lamp would work in space, read the transcript below.

How did you get interested in science?
When I was 8 years old, I used a pair of binoculars borrowed from my dad to look at stars and I found that the middle star in the handle of the Big Dipper was double. Many astronomers have seen this before me, but I was fascinated to learn that those stars orbit each other. Since then, all I've ever wanted to be was an astronomer.

What's your favorite thing to study in space right now?
Exploding stars, novas, and supernovas. All novas are binary stars and they explode many times. We don't know if supernovas are single or binary and we're not sure about why some of them explode. That's why it's so interesting to study them. There are many ways astronomers study them. We look at galaxies to see where they explode and to see if there are different kinds of supernovas in different kinds of galaxies... and there are!

How many supernovas have happened?
There are three supernovas per second in the universe. There are 30 million seconds in a year — so there are 90 million supernovas every year. The universe is about 14 billion years old, so there have been about 1,300,000,000,000,000,000 supernovas since the big bang.

What do you predict will be the next big space discovery?
If I knew what it was, I'd make the discovery myself. The reason astronomy and all sciences are so fascinating is that you never know what you might discover next.

Do you think a space shuttle will be sent to Pluto?
Very unlikely, because the space shuttle only carries enough water and air for a few weeks for the astronauts on board, but it takes 10 years to get to Pluto. So any space voyage to Pluto would have to be in a much more sophisticated and advanced vessel than the space shuttle — and this spacecraft doesn't yet exist.

Have you ever traveled into space? Would you want to?
I haven't and I would love to! Lots of astrophysicists have gone into space as astronauts. The next most desirable profession for an astronaut, after being a pilot, is to be an astrophysicist.

How do we know that the galaxies we see are whole galaxies, full of stars, planets, moons, and other stuff?
We see that the galaxies are full of stars through images taken with large telescopes, including the Hubble Space Telescope. We can't yet detect planets or moons in other galaxies, but since there are lots of planets and moons in our own galaxy, we assume that there are lots of planets and moons orbiting the stars of other galaxies.

What's the theory on the newest planet?
Just like Pluto, it's really a large comet and not a planet at all. There are thousands and maybe millions of such objects in the outer part of the Solar System, and they were formed in a completely different way from the eight inner planets.

Who's your favorite astronomer?
Vera Rubin. She discovered dark matter. About a third of the universe is made up of some kind of matter unlike the protons, neutrons, and electrons of which we're constructed. Nobody knows what this stuff is, and she discovered it and proved that it exists through many years of persistent work.

What do you usually do during a day at work in the museum? Do you have to stay up late to watch the skies?
Hardly ever. I gather most of my telescope data in a few intensive weeks of observing every year, and then I analyze the data, write up the results for scientific journals, and teach classes and students from nine to five, Monday through Friday, for most of the year. So, perhaps surprisingly, astronomers aren't night creatures any more.

Hypothetically, if you could travel anywhere in the universe, where would you want to go and why?
I would want to go to a star called SS Cygni — a dwarf nova. This star gets 100 times brighter every few months. There are theories as to why this happens but no one knows for sure. I'd like to get up close to watch for an eruption and see what causes it.

Do all planets have gravity?
Yes. The more massive the planet, the greater its gravity. Every object in the universe exerts a gravitational pull on every other object. That was discovered by Isaac Newton.

I worry about all the "stuff" in space these days. When I think of all the satellites, I wonder how does NASA make sure space shuttles don't collide with satellites or other things orbiting the Earth?
Good question. The United States Air Force tracks every object in Earth's orbit down to the size of a mitten. In fact there's a space glove orbiting around out there that someone lost. If one of those objects is heading towards the shuttle, NASA moves the shuttle into a higher or lower orbit. They track the objects using radar.

Would Earth ever collide with another cosmic object?
Frequently. The Earth is bombarded by meteors every day and objects as large as a football field every few centuries.

If an asteroid from the Asteroid Belt enters Earth's atmosphere, is it then called a meteor, or does it remain an asteroid?
Good question. Yes, it's an asteroid outside the atmosphere and a meteor once it enters the atmosphere.

Wow! How big are the meteors that hit Earth every day?
On a daily basis, they range from microscopic to up to a foot or two across. The large majority of them burn up in the atmosphere.

What would happen to a lava lamp in space? Would the gloop still go to the top, then fall?
There is no top or bottom in space. If you turn the lava lamp on, you'd create stirring in the fluid because the fluid closest to the heating element would be hotter than the fluid further away. But the flow pattern would be different from what you'd observe on Earth. You'd have to do the experiment to find out what that pattern would be.

Can you use a cell phone when in space?
Sure. As long as you have a cell transmitter on your spaceship and the spaceship to which you are talking has a cell receiver. You can't use it to talk to the ground because you'd be too far away; the signal from your cell phone would be too weak to reach the ground. Radio waves propagate just as well in space as they do on near Earth.

What does it take to be a scientist?
Persistence. First of all, it's hard work. Patience. Imagination. Many years of training and the ability to admit sometimes that your hypothesis is wrong and it's time to start all over again. But most of all, you need a sense of curiosity.

How did each planet get its name?
All of the original planets, the ones known in antiquity, were named after gods and goddesses of mythology. Today, newly discovered objects are named by the International Astronomical Union. There are often attempts to name planets after various gods and goddesses, but not just from Greece; for example, Sedna was named after the goddess of the sea in Inuit mythology.

Can I go to space someday? What should I do to prepare?
You are very likely to go to space. One of the best ways is to become a scientist — that means studying mathematics, physics, chemistry, and biology.

Why do Saturn, Uranus, and Neptune have rings around them?
Jupiter does too. They're probably the remnants of small moons or comets that came too close to those planets and were broken up by the tidal forces of those planets.

What else are you interested in finding out more about besides space?
I would say the evolution of life on Earth and in particular, why species become extinct.

What kind of books do you like to read?
Spy novels

Is it true that somewhere in the universe there’s more life?
We don't know. There may be lots and it's conceivable that there's none. Astronomers are looking hard, but we truly don't know.

I saw a documentary discussing astrobiologists. Is it a growing field to study life on other planets when we haven't found any yet?
It is, but the studies are looking for exoplanets. First we're trying to find the planets and then we're looking for the life. So the real study and the real competition is to find the planets orbiting other stars.

How do you measure light years?
You measure the distance to nearby stars using a technique called parallax. You take a picture of a star over a six-month interval that gives you two angles of a triangle. The base of the triangle is the 186 million mile diameter of the Earth's orbit. Then using trigonometry, you can solve for the other two sides of the triangle, which are equal to the distance from the Earth to a star. The nearest star is 4.3 light years away.

Is it true that Mars is red?
Yes. If you look up in the sky, Mars appears to be orange-red. And that's because there's a lot of rust (iron oxide) in the soil of Mars.

Why does Saturn's moon Titan have an orange atmosphere when none of the other moons have that?
It's the only moon that has an atmosphere. We're not really sure, but it's probably because Titan is the most massive moon with the strongest gravity. So it might retain its atmosphere while all the other moons of the Solar System have lost theirs.

Do you believe in the big bang theory?
There's a tremendous amount of evidence to support it and all of its predictions are vindicated by observation. So, I think that the big bang theory is right. I don't believe in it in a religious sense. I think that it's right because of the scientific evidence supporting it.

What's the hardest part about being an astronomer?
Applying for telescope time — which is very competitive — and sometimes being turned down. These are multibillion dollar telescopes, like the Hubble Space Telescope, which have many more requests to use them than time available.

Is it possible for the Moon to shift into a new orbit?
The Moon is shifting all the time because it's acquiring angular momentum from the Earth through tidal forces. The Moon is receding from the Earth constantly, but very slowly. It will never completely escape from Earth.

Have you ever discovered something that no one else knew? What was it?
Yes! That novas go through a sort of cyclic evolution where part of the time they are explosive, part of the time they are dormant, and that this metamorphosis happens thousands of times for every nova over billions of years.

You know so much about space! How long did you have to go to school to be a space scientist?
I got my PhD when I was 28, so I was in school for 23 years to be an astronomer, from kindergarten to my PhD.

Why does the Moon have so many more craters than Earth?
Because the lunar craters aren't eroded by wind and rain. If the Earth had no atmosphere, it would be just as cratered as the Moon.

Is there such a thing as a wormhole in space?
We don't know. It's an interesting concept that some kind of tunnel connects black holes or white holes in space, but we have no evidence one way or another.

How cold is space?
Negative 270 degrees Celsius: that's the temperature of the microwave background radiation, the light left over from the big bang.

Would it be possible for another big bang to occur?
Maybe. There are theories that suggest that the big bang that created our universe is just one of an infinite number of big bangs, but we really don't know.

What would happen if I was in space and not wearing a space suit?
Your body would explode because you generate pressure to fight off the pressure of the Earth's atmosphere. In space there's no atmosphere or pressure to react against.

If stars are big, shouldn't they be considered to be planets?
No Anything that is 70 times as massive as Jupiter ignites nuclear reactions in its core, thus, it becomes a self-luminous object — a star. Less massive objects like Jupiter and the Earth reflect light but don't generate it themselves, and that's why they are planets and not stars.

If the sun exploded would we have another Ice Age?
The sun won't ever explode. At the end of its life, in about four billion years, it will expand to swallow Mercury, Venus, and Earth. The outer part of the sun will be lost and the inner part will contract to become a stellar corpse called a White Dwarf Star.

What's your family background? Did your mom, dad, or other relatives and friends encourage you to become interested in science? Was it something you gravitated toward from early on?
There are no scientists in my family except for one pharmacist uncle, but they were very supportive. They were a little skeptical, but they've enjoyed my success in astronomy.

Do you have any final words for all the student space scientists out there?
Even though it might seem difficult or challenging in high school or university, becoming a scientist is fantastically satisfying. You never do the same thing twice. You are always challenged and most scientists deeply love what they do.