Philip Plait's Blog, page 20

Extragalactic stars in my eyes

For centuries, astronomers scratched their heads and wondered what the hell these weird “spiral nebulae” in the sky were.

They showed up pretty much everywhere they looked. Some were small, some big, some were amorphous blobs, some showed clear spiral or other structure. Astronomers knew that some nebulae — Latin for “fog” — were gaseous by the end of the 19th century, but the true nature of their diversity remained elusive. Some astronomers speculated that some of these were separate galaxies ...

A supermassive black hole that can't stop erupting

If there’s one thing you learn when you study astronomy, it’s do NOT screw around with black holes.

100 million light years from Earth lies a galaxy called NGC 5813. It’s part of a small galaxy group, a collection of a few dozen other galaxies. When viewed in visible light NGC 5813 looks like any other elliptical galaxy: An elongated puffball with a few hundred billion stars in it.

But it has a supermassive black hole in its heart, one that tips the cosmic scales at 700 million times the mass ...

Space warp puts a supernova on cosmic repeat

An intergalactic mirage of sorts is acting like a time machine for astronomers, allowing them to see a supernova at three different stages in the explosion simultaneously. And it’s going to allow them to see it again in a kind of cosmic rerun.

About 4 billion light years from Earth lies the magnificent galaxy cluster MACSJ0138.0-2155 (let’s call it MACS J0138 for short). This is a collection of hundreds of galaxies all bound together by their mutual gravity. The mass of the cluster is so strong...

Want to go to Mars? Better leave when the Sun is active to minimize galactic radiation poisoning

If the idea of sending humans to Mars is a romantic one, the reality of it is a bucket of cold water.

Going to Mars is hard. Something like half of all missions have failed for one reason or another, but adding humans into the mix makes things far harder. We inconveniently need air and water and food, for one thing, but we also need the environment to be safe.

Radiation is a direct threat to that.

In this case I mean subatomic particles zipping around space at extremely high velocities. These...

Will DART slamming into an asteroid's moon cause it to tumble chaotically?

In November 2021, NASA is launching a bold mission to test the technology needed in case we ever have to push a potentially hazardous asteroid off of an Earth-impacting trajectory. Called DART — for Double Asteroid Redirection Test — the 500-kilogram spacecraft will slam into an asteroid’s moon at over 23,000 kilometers per hour, changing the moon’s velocity by a tiny amount.

The idea is that if we ever find an asteroid headed our way, a future DART-like spacecraft can hit it and change its spe...

The Earth may not be flat but this galaxy sure is

From the ground, the Earth looks flat.

That’s an illusion of sorts, of course. There’s a lot of evidence the Earth is actually a spheroid if you look carefully. And, obviously, from space our planet is clearly a ball.

This illusion can work in reverse, too. Some disk-shaped galaxies are face-on to us, making them appear as magnificent circular objects, grand and sprawling across tens of thousands of light years.

But seen from the side they appear very different. Disk galaxies, including the M...

Kleopatra may be a dumbbell-shaped metallic rubble pile

One of my favorite space rocks is 216 Kleopatra.

It’s an asteroid in the main belt between Mars and Jupiter, and it’s one of the biggest ones. The reason I love it is because of its shape: It looks like a cartoon dog bone or a dumbbell, two elongated lobes stuck together via a neck between them.

The exact shape, size, and other physical characteristics have been surprisingly difficult to pin down, but a couple of new papers have just been published by astronomers who used a suite of observatio...

Want to slow aging? Gently fuse hydrogen all over your surface

Not to be macabre, but white dwarfs are useful. These are the corpses of stars like the Sun. When stars like this run out of fuel in their cores they blow off their outer layers, exposing the hot, dense core: a white dwarf with the mass of a star packed into a sphere the size of the Earth. The beauty of white dwarfs is that they don’t generate any energy of their own. They’re basically embers, hot balls of glowing matter that cool and fade as they age.

This means they can be used as cosmic cloc...

Astronomical speed trap catches its 1000th asteroid

Astronomers reached a 1.6 kilometerstone* recently: They observed the 1,000th near-Earth asteroid via radar.

That’s a lot of rocks. But it’s only a fraction of what’s out there.

Near-Earth asteroids (or NEAs) are pretty much as advertised: Asteroids that get near Earth. Specifically they’re defined as any asteroid with an orbit that drops it as close as 145 million kilometers of the Sun (1.3 times the distance of the Earth from the Sun).

As of September 2, 2021, there are 26,520 NEAs known. N...

So, a star may have eaten a black hole and exploded

What happens when a massive star eats a black hole or neutron star?

Theoretical models show it explodes, epically, but only after a series of events that cause the star to eruptively eject its outer layers before the compact object plunges into the star's core, disrupts it, and creates one of the most energetic events in the Universe: a supernova.

Or so the models show. But now, for the first time, astronomers may have seen an example of exactly such an event, and I am not one bit ashamed to s...