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Gazing around a neutron star, chancy clam mating, 45 tomato plants for 1 man’s oxygen

Q: Do this thought experiment: You are an immaterial observer. (Otherwise, you would not live long enough to make observations). You are on a neutron star. How do the sky, horizon, and surface look? What color is the neutron star? White? Black? Like a mirror? What color is a neutron? —Rudy

Nemiroff superimposed a map of the Americas to illustrate the “fun house” mirror distortions on a neutron star.  [Robert Nemiroff, Michigan Technological University]

A: I assume you mean a cold neutron star—one that’s been around about half the age of the Universe—not a young, hot, blue neutron star like the one we identified in November 2000.

OK. I’m on a cool extraordinary-dense neutron star—a corpse of a star. All that’s left when a star 15 to 30 times bigger than our Sun went supernova and then coasted through space, cooling for 6 billion years or so. My neutron star is tiny—maybe a 12-mile diameter (20 km), that I can circumnavigate in 38 minutes, going 60 mph (100 km/h).

Its mass is about 1.4 times that of Sol. Imagine how dense it must be. "At these incredibly high densities, you could cram all of humanity into the volume of a sugar cube," says astronomer M. Coleman Miller of the University of Maryland.

You see, after it went supernova, not even the pressure of its densely packed electrons withstood its gravity pressures. Gravity crunched the star’s electrons and protons together to form neutrons—a dense neutron ball that held off further compression.

This is no calm planet I’m "standing" on. Star quakes crack and ripple its crust due to a magnetic field that’s trillions of times greater than Earth’s.

The atmosphere is only inches (centimeters) deep. I look into the sky through a telescope and see the darkness of space and a sprinkling of stars. The stars look strangely blue and squished into "flying saucer" disks by gravity effects. Gravity warps the surrounding space, which shortens the waves of incoming starlight. That shifts the color toward the blue end of the spectrum. The horizon is slightly curved because the star is much smaller than Earth.

The surface appears distorted; shapes are fat and compressed like those reflected by a circus "fun house" mirror. See the figure by astrophysicist Robert Nemiroff, coauthor of The Universe: 365 Days. No major features exist. Gravity has leveled the terrain into a crystalline iron surface covering a level plain. It looks like dirty ice but ripped with jagged fissures from frequent star quakes. The surface is dark because not many electrons remain to interact with light at energies of a few electron volts.

A single neutron has no color because it has no electron to interact with light and reflect light back to the eye.

By the way, a single electron doesn't have any color either. "It's much smaller than the wavelength of light, and in fact at the low frequencies of visible light, single electrons scatter all light equally," says Miller.

Further Surfing:

M. Coleman Miller, University of Maryland: Introduction to neutron stars

Robert Nemiroff, Michigan Technological University: Virtual trip to a neutron star

NASA: Neutron stars and pulsars

Q: How do clams mate? —Lady Lauren, Antelope, California

A zebra mussel; actual size is 0.75 inches (2 cm). [USGS]

A: Clams (aka mussels) mate haphazardly.

Rivers: The male squirts his sperm into the water and the river current carries them downstream. The female draws sperm in to fertilize eggs still inside her body. Fertilization odds are poor unless the male is upstream of the female.

Oceans: In the spring or summer, the male expels sperm, just as river mussels do. The female, however, doesn’t contain the eggs but rather shoots them into the water. If she’s lucky, the female’s eggs float near the sperm. Otherwise, the system fails.

During a breeding season, a female clam makes tens of thousands of baby clams. Probably only one settles to the bottom and survives to adulthood. Mussels live for 10 to 100 years.

Further Surfing:

USGS: Zebra mussels

Illinois Department of Natural Resources: Anatomy of a mussel

Dan Kelner, Minnesota Department of Natural Resources: Mussel bound in Minnesota

Q: How many plants are needed to produce enough oxygen for one person? —Jim, Tampa, Florida

Tending wheat, Nigel Packham peers out of the Advanced Life Support Chamber [NASA]

A: During their growing season, 10,600 average-size leaves exhale each day enough oxygen for one resting healthy person to inhale that day. How many plants is this? It depends on how many leaves a plant has. For example, a large tomato plant has about 250 leaves. So, about 45 tomato plants could provide enough oxygen. It takes 625 square feet (58 sq. m.) of grass to make enough oxygen. That’s a small lawn, 25 feet on a side.

Further Surfing:

Brian Anderson, Lunar and Planetary Information Bulletin: Living and working with plants in other worlds

(Answered July 11, 2003)