Philip Plait's Blog, page 26

How many aliens planets can see Earth? More than we first thought

In 2020, a pretty cool research paper was published. In it, the astronomers posited the question: What nearby stars are in the right spots on the sky to see Earth transit the Sun, and therefore any purported aliens living on planets around those stars might know we exist?

I wrote about this paper and how the geometry works at the time, so please take a moment to read that and come back here.

All done? So basically, the most successful method we have to detect exoplanets — aliens worlds orbitin...

New evidence that parts of Venus’ crust may be squishy

File this under "Venus is still doing stuff we didn't know about until recently": Blocks of the crust on the more-than-broiling-hot planet show that they've moved relative to one another, both sliding past and rotating, like plates of ice on a frozen lake. This may be due to movement of the mantle underneath them, which in turn indicates that our evil twin planet may yet be geologically active. Like, now.

Venus is similar to Earth in some ways; it's about the same size and mass, but at the same...

The Red Sky Paradox: Why do we orbit a star like the Sun instead of a red dwarf?

Here’s what seems like a weird question: Why do we orbit a star like the Sun instead of a red dwarf?

Think of it in a probability sense: Red dwarfs (called M dwarfs by astronomers) are far more common than stars like the Sun (G dwarfs; slightly hotter ones are called F and cooler ones K), and also “live” much longer (they can remain stably fusing hydrogen into helium in their cores for hundreds of billions of years, and some longer), so it’s a reasonable assumption that by far most habitable pl...

Don’t panic! But a gigantic comet is currently inbound toward the Sun

While scanning older data from a telescopic survey of the sky, astronomers discovered a very interesting object: Called 2014 UN271, it’s a giant chunk of ice and rock that normally spends its time far, far out past Neptune, but is now heading into the solar system, and will get about as close to the Sun as Saturn over the next ten years!

To be clear, a lot of new comets we find dip pretty close to the Sun after spending millennia out there in the black, but this one is different for quite a few...

What happened to this galaxy’s dark matter?

Back in 2018, astronomers used Hubble to observe a relatively nearby galaxy and found it presented a baffling mystery: It appeared to have little or no dark matter.

This was so weird they decided to follow up to make sure their results made sense. So they took more Hubble observations — a lot more — and the mystery only deepened. It appears to have even less dark matter than they originally thought.

This is unexpected, and bizarre. Why doesn’t this galaxy have a feature pretty much every other...

Perseverance is now ready to actively begin looking for evidence of life on Mars

NASA's Perseverance rover landed on Mars on Feb. 18, 2021. Since that time it's been in a shakedown phase, testing its various complicated components to make sure everything is functioning A-OK.

During that time it's watched a sunset, flown a helicopter, listened to itself moving around, inhaled the air of Mars to make breathable oxygen, and much more.

The commissioning phase of the mission was completed on June 1. Everything works the way it ought to. And now, this car-sized nuclear-powered l...

How long would it take for an alien civilization to populate an entire galaxy?

Let's say there are aliens out there.

Let's also say that they are slightly more advanced technologically than we are. So, they can build ships of some kind that either a) have AI that can self-replicate if they find a planet with materials to build more probes, or 2) carry aliens with them that can settle* a suitable planet they find. They then establish themselves, grow, and send out more ships when they are capable.

How long would it take for them to populate the entire galaxy?

It's an int...

We may finally know why Betelgeuse dimmed so much. Bonus: No supernova. Yet.

In late 2019 and early 2020 the star Betelgeuse started behaving badly. Normally one of the very brightest stars in the sky, it dimmed drastically, and for a few weeks dropped in brightness to less than a quarter its normal luster.

Then, just as suddenly, it began to brighten again. While it took a second, far smaller dip in June/July of 2020, it is now back to its usual ruddy glow marking the left armpit of Orion*.

Because it's such a showy star, and easily observable all over the planet — no...

How far away are supernovae? Astronomers find a way to tighten measurements

A team of astronomers studying distant exploding stars has found a way to tighten up the way the distance to them is measured — and in doing so, tighten up measurements of how the Universe is expanding.

This kind of supernova is called a Type Ia. These occur when a small, dense white dwarf accumulates matter on its surface, eventually gathering so much matter the entire star undergoes nuclear fusion. The release of energy is absolutely colossal, equivalent to billions of times the Sun's output....

Star formation is beautiful and terrifying

I do love a good nebula.

This is the term astronomers use for vast clouds in space, made of either gas or dust (tiny grains of rock or soot made when stars die). They come in many varieties. Some are rapidly expanding debris clouds from supernovae, exploding stars. Some are small and dark, sometimes called Bok globules. Others are wispy and sprawling, or lit both by reflection and their own internal excitation by nearby hot stars.

And some, oh my yes some, are immense clouds of both gas and du...