Happy Dark Matter Day!

Today is International Dark Matter Day! Dark matter outweighs the normal atoms in our universe by about five times. Physicists and astronomers aren’t exactly sure what it is, but we know what it’s not – it’s not material that emits light of any kind, and it’s not black holes. Read more about dark matter here.

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Spooky Space, Part 7: Ghoulish Gas Clouds

Happy Halloween everyone! I hope you’ve enjoyed this series of posts.We finish up with some holiday appropriate nebulae, clouds of gas and dust in space that are usually associated with either the birth or death of a star.

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NGC 3242, The Ghost of Jupiter Nebula

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Sharpless 2-136, The Ghost Nebula

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NGC 2080, The Ghost Head Nebula

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Sharpless 2-68, The Death Eater Nebula

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NGC 246, The Skull Nebula

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IC 2118, The Witch Head Nebula

Spooky Space, Part 6: Vampire Stars

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[Close up of the core of the globular cluster NGC 6397 showing blue stragglers among the red giant stars]

From Dracula to Lestat,  vampires have been a mainstay in popular culture. Seemingly immortal, they survive many times longer than a normal human lifespan by literally sucking the life blood out of their human victims. Astronomers have seen similar behavior in stars called blue stragglers in globular clusters, tightly knit communities of hundreds of thousands to a million stars. They represent some of the oldest stars in our galaxy, so why are there hot blue stars among the dying red giants?

The issue is that hot blue stars have larger masses and hence much shorter lifespans than stars like our sun. So in an old neighborhood like a globular cluster where no new stars are being born, a hot blue star sticks out like a teenager in a retirement community. The solution to this problem seems straight out of an Anne Rice novel.

Despite the fact that the two stars in a binary system form at the same time, they are usually born with different masses and hence die at different times. The heavier star dies first, swelling up to become a red giant. Once this happens, the outer layers of the dying star can be pulled into the smaller star via gravity. This increases the mass of the smaller star, giving it the false appearance of a young and short-lived hot blue star.

But the innocent red giant does have a kind of last laugh on its cannibalistic neighbor. By increasing its mass, the vampire star shortens its lifespan, and will turn into a red giant itself before too long (astronomically speaking).

Spooky Space, Part 5: The Goblin

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[The orbit of The Goblin]

Although it was first discovered in 2015, the extreme dwarf planet 2015 TG387, nicknamed The Goblin, was recently in the news. Astronomers now have a good sense of its orbit, and it’s really out there (literally)!

At about 200 miles wide, The Goblin is only a seventh the diameter of Pluto, but it makes up for its small size with an extreme orbit. At its perihelion (closest approach to the sun), it’s still 7.4 billion miles from the sun, two and a half times farther than Pluto. At its aphelion (most distant point from the sun), it’s an amazing 70 times more distant than Pluto, or more than 200 billion miles!

Such an extreme orbit is a signal that something has gravitationally interacted with The Goblin, and it’s too far from the sun for that “something” to likely have been the giant planets such as Jupiter. It’s possible (note, possible, not definite) that there is a ninth, still undiscovered, planet at least the size of Earth (if not larger) in the outer solar system. If so, then Planet X is haunting us!

Spooky Space, Part 4: Zombie Stars

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In the outskirts of the spiral galaxy NGC 1309 lurks an undead star worthy of The Walking Dead. Called SN 2012Z, this system was the first example of what astronomers call a mini supernova, or, more colorfully, a zombie star.

Middle range stars like our sun die as a white dwarf, a dense, compact corpse made mainly of helium, carbon, and oxygen. If one star in a binary star couple dies as a white dwarf before its mate, it can go through a cannibalistic stage and literally suck the life (the gas) out of its poor companion.

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If the white dwarf eats too much, it explodes, causing what astronomers call a Type Ia supernova. No white dwarf had ever been seen to survive such a violent outburst, until the discovery of zombie stars (now technically called Type Iax supernovae).

The record for rebirths might just be held by the supernova iPTF14hls (located in a more distant galaxy). Archived images show that this white dwarf has survived at least six “deaths” since 1954, including 5 explosions between 2014-2016.

Eat your heart out, George Romero. Not literally, of course.

 

Spooky Space, Part 3: Franken-galaxies

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[Three NASA photos of UGC-1382, located about 250 million light years away]

Just as Mary Shelley’s famous creature was constructed of pieces taken from other bodies, Franken-galaxies appear to be amalgams of multiple galactic bodies. One of the most famous is UGC-1382, shown above. The left picture shows what it looks like in regular photo taken by a large telescope. To the eye, it appears like any other elliptical galaxy. However, ultraviolet data (center) and faint visible light (right) show that there is much more to this galaxy that we first suspected, including spiral arms! Not only is the strange galaxy ten times larger than first suspected (and seven times larger than our Milky Way), but it is actually younger on the inside than the outside. Imagine your skin forming and then having your internal organs stuffed inside!

This galaxy is not only inside-out, it is also extremely fragile (in a gravitational sense). The gravity from any nearby galaxies would cause it to fall apart. Luckily for it, UGC-1382 lives in a rather boring cosmic neighborhood.