Category Archives: Short Questions

Sometimes you have a question that has a simple answer, and you’re not interested in all the extra background info. This page is full of short no-nonsense answers, for researchers on the go. Any extra background info will be referenced by a link. I guarantee, not one single answer will take more than a single paragraph!

What is a planetary nebula?

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Planetary nebulae are clouds of dust and gas ejected from older stars as they move on to the next stage in their evolution. When a star uses up all its hydrogen fuel, and begins to burn helium, the core heats dramatically, causing the outer layers of the star to inflate dramatically. The outer layers of the star escape its gravity, and the solar wind of high energy particles and radiation accelerates the still superheated plasma out into space where it … Continue reading →

What is a globular cluster?

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Globular clusters are clusters of stars, arranged into a sphere. They contain tens of thousands of stars, packed very closely together, so that when viewed from the Earth, their core’s appear as a single glowing mass. Globular clusters are arranged in a vast spherical halo around their parent galaxy. Our own Milky Way galaxy has a little over 150 globular clusters, but larger galaxies can have many more than that. They tend to be very old – at least as … Continue reading →

How many moons does Neptune have?

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  As of February 2024, we know of sixteen moons orbiting Neptune.  The largest, Triton, was discovered only 17 days after Neptune itself was found in 1846 and it would be over a hundred years before any others were first seen.  Triton is one of the larger moons in the Solar System with a diameter of 2700km, and orbits backwards around Neptune.  The most recently discovered moon, by contrast, is less than 8 km across. No doubt there are more … Continue reading →

How many moons does Pluto have?

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As of 11 July 2012, we know of five moons around Pluto.  The largest, Charon, was discovered in June 1978, and is closer to its parent in size than any other moon in the Solar System.  In fact, when it was first discovered it was found that the combined mass of the two had thrown out all calculations of Pluto’s size.  Up till then, Pluto was assumed to be much larger than we know it is today.  The next two … Continue reading →

What is a neutron star?

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  When a star runs out of fuel to burn, it’s outer layers get ejected into space and it’s core collapses under gravity into a white dwarf.  If the star was really big, more than about 8 times the mass of our Sun, then it continues to collapse, becoming denser and denser until the very atoms themselves are crushed.  The enormous gravitational pressure overcomes the Weak Nuclear Force, so that electrons fall out of their orbit and touch the protons … Continue reading →