What’s going on with the moons of Jupiter?

The orbit of Jupiter's moons are all messed up and seemingly overlap. Do they interact much? Greg, U.S. Jupiter has 67 confirmed moons. Of these, 8 are regular satellites with nice prograde motion (they move in...

How do we know how massive stars are?

As we discussed in the previous vlog our understanding of stars is still incomplete, but there are areas which we are very confident on what we know. In general we tend to know three things about stars: their brightness, their spectrum, and if they are close enough or of known luminosity, we can also know their distance.

Can a satellite hover over the Sun?

My friend Russell asked me under which condition an object would be able to stand still around the Sun. This is a very interesting question; it probes some fundamental facts about the solar system...

A Galaxy Interaction That Deceives The Eyes

This NASA/ESA Hubble Space Telescope photograph is one of my favourite images of interacting galaxies, but it's actually a bit of a cheat. The galaxies are not interacting at all. The galaxies are simply in...

One Planet, One Climate, One culture.

One of my biggest pet peeves about sci-fi universe building is the lazy approach in building alien civilisations. We often see the trope showing one world, one climate, and one language. Given the variety...

The Ethics of Timetravel

I recently talked about how time travel to the past is unlikely to be possible. That came with the label that we haven't found a law that tells us that it's impossible just yet....

Could The Earth Turn Into A Neutron Star?

"Everyone always wants to turn the earth in a black hole! Instead, COULD YOU turn it into a neutron star?" Ooooh! I like this question! Chris is right, black holes hold the fascination of many as the densest objects in the universe, but the "humble" neutron stars shouldn't be considered the offsprings of a lesser god.

How big is the biggest galaxy in the Universe?

If by big we mean physical dimension, the largest known galaxy is most likely IC1101. IC1101 is gargantuan even among galaxies; it's a super elliptical galaxy with a diffuse stellar halo that to extends to at...

Shopping for rings

I have a space question. I know about the Roche limit but is there an upper limit to how big a ring can get compared to its planet? Asked by Dan Of course there are limits, the Universe is all about limits! But they're not as strict as one would think. We have found an object in 2012, J1407b, with a ring system 200 million kilometres in diameter. If the rings were centred on Earth they would cover the inner solar system all the way to the orbit of Mercury on the opposite side of the Sun.

What Would Being In Space Without A Suit Be Like?

Spacesuits are a fundamental tool for keeping astronauts safe in space, but the protection they supply is often mistaken, exaggerated or romanticised in science fiction.   Spacesuits are garments worn by astronauts to survive the...

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