Philip Plait's Blog, page 39

Why is Earth still habitable after billions of years? In part, we're just lucky.

When you look around you, almost anywhere on Earth, you see life. Earth seems exquisitely supportive of life: We see it in the air, in the water, in the land, and even deep underground.

But was that inevitable? We know that there have been mass extinction events in the past, some taking out the majority of life on Earth. However, since life got started and spread around on Earth there hasn't been any event that completely eradicated life. Of course! Else we wouldn't be here to ponder it.

Still...

Memories of the Blue Snowball

I was procrastinating the other day — shocker, I know — and tooling around Instagram to see what there was to see.

An astonishing number of astrophotographers post their work there (and a lot of content scrapers do as well, which is extremely irritating), as do some national observatories and international science collaborations.

NASA does too, of course, and when I saw this image I gasped, then smiled, then chuckled out loud.

Hubble’s view of the planetary nebula NGC 7662. Credit: NASA, ESA,...

The most distant astronomical object ever seen… in 1962

Foreword: 

One of the fun things about having written thousands (!!) of articles about astronomy over the past decade or two is going through old posts looking for relevant info. If I’m writing about a black hole, say, then it helps to link to older articles that have background info, saving me the trouble of writing it again.

Every now and again I’ll be writing about some particular object and then hit the archives to see what I’ve said about it before. It doesn’t happen often, but sometimes ...

A planet eats a disk while the disk eats a nebula. It’s eating all the way down

Astronomers have found what may be a very weird case of a young star and planet forming in a dense cloud of gas and dust about 500 light years away. The young system is forming in a disk, which is common enough, but in this case the disk itself appears to still be forming from gas falling into it from the surrounding nebula!

The nebula is called Barnard 59 (or B59), a dense, cold knot of gas and dust called a molecular cloud. In this case, it’s part of the remarkable Pipe Nebula, a complex of d...

Wait. Jupiter has *how* many moons?

At the moment, Jupiter has 79 moons.

By that I mean 79 that we know of, including a dozen just found recently. But how many are there in total?

The question is hard to answer as is. For one thing, how small a thing do you call a moon? If, say, something the size of Baby Yoda orbited Jupiter, I wouldn’t call it a moon*. But something a kilometer across? Sure.

The other issue is that as objects get smaller they get fainter. Jupiter orbits the Sun 5 times farther than the Earth does, so at best ...

So, um, does anyone remember where we put that supermassive black hole?

You'd think a black hole with the mass of a decent-sized galaxy would be easy to find. But then, you're not looking for the one in the center of a galaxy in Abell 2261.

Abell 2261 is a ridiculously huge cluster of galaxies about 2.7 billion light years away from us. It has thousands of galaxies in it, and astronomers measure its total stellar content to equal the mass of a quadrillion (1015) Suns.

So yeah, it's a beefy cluster.

Like most big clusters, it has a big galaxy sitting in its center...

A signal from Proxima? Likely intelligent, unlikely from aliens

Astronomers looking for signs of alien life on other planets in the galaxy have found an unusual signal from Proxima Centauri, the nearest star to the Sun, that is... intriguing. It was just a single detection that came and went, but it does have some characteristics you'd expect from an intelligent source. The problem is, as it always is, that source may be us.

I want to be very clear here right off the bat, because The Internet: This is by no means proof that aliens are out there, or even (ye...

The star cluster that wasn't: How did M73 fool generations of astronomers?

I love a good coincidence, and this story has two. One is pedestrian, the other cosmic.

It starts with me pondering Gaia data. Gaia is a European Space Agency observatory that is revolutionizing astronomy. Its mission is to accurately map the positions, colors, distances, and motions of over a billion stars — yes, a billion, about 1% of all the stars in our galaxy — and create a massive database of the results, essentially a 3D map of the Milky Way galaxy.

Such surveys are incredibly useful. N...