Archive for the ‘Astronomy’ Category

Castor and Pollux, Not Really Twins


(Syfy Wire::Bad Astronomy) – Phil Plait:

If you live in the northern hemisphere – and statistically speaking, there’s a 90% chance you do – then go outside and look south as soon as the sky gets dark. You’ll see Orion standing tall to the southwest, leaning a bit to his left (your right, since we assume he’s facing us), with the bright star Sirius to the lower left, and Procyon directly left of reddish Betelgeuse (Orion’s right shoulder – to your left).

Just above Procyon are two more bright stars, close together in the sky. These are Castor and Pollux, and they mark the heads of the twin brothers denoted by the constellation Gemini. If you have good eyesight you may be able to tell that Pollux (the one closer to the eastern horizon) is yellowish, while Castor is blue. …

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Gemini, by Rogelio Bernal Andreo

Does Earth Have a Trojan Horde?


(Syfy Wire::Bad Astronomy) – Phil Plait:

Are there asteroids sharing Earth’s orbit around the Sun?

Cutting to the chase: Yes, there is at least one. But how many are there? There might be a lot, but we don’t know. The cool news is, we may very well know more soon. …

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OSIRIS-REx at Earth's L4

Pluto Will Never Be A Planet Again


(Starts With A Bang!) – Ethan Siegel:

Practically everyone alive today grew up learning some way of remembering the nine planets of our Solar System in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Beginning in the 1990s, however, two revolutions in astronomy happened all at once: the uncovering of trans-Neptunian objects and the discoveries of worlds around other stars. These discoveries compelled us to rethink our definition of a planet, culminating in the official 2006 definition of “planet” by the International Astronomical Union (IAU). Pluto was out. But with many people unhappy with the IAU’s definition, the story doesn’t end there. …

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Planetary and non-planetary status

Cassini Keeps Dropping Awesome Images


(Planetary Blogs) – Jason Davis:

At the moment, Cassini‘s outer ring orbits are revealing some wild, high-resolution shots of some of Saturn’s most enigmatic worlds. Most recently, this included new looks at 35-kilometer-wide Pan. On March 7, Cassini got its best view yet of the ravioli-shaped moon, which orbits inside the A ring‘s Encke gap. …

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Pan on 2017-03-07, by Cassini

How Mars Lost its Atmosphere


(Starts With A Bang!) – Ethan Siegel:

In November of 2015, the MAVEN mission announced its first science results, and what we found was a tremendous confirmation of what we expected, along with some incredibly precise details:

  • Water was abundant and active on Mars for the first few hundred million years of the solar system, with oceans, rivers, rains and more.
  • However, at some point less than a billion years after Mars formed, its global magnetic field ceased to be, removing the planet’s main source of protection from the solar wind.

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Solar Wind at Mars and Earth

Did Mars Once Have Three Moons?


(Starts With A Bang!) – Ethan Siegel:

Mars’ two moons, Phobos and Deimos, are small, irregular, but orbit in the same equatorial plane as the red planet. Although they’ve long been thought to be captured asteroids, those orbits would be supremely unlikely. Another possibility would have been if a massive impact created a debris disk, similar to how Earth’s Moon was formed. That alternative creates equatorial orbits, but normally produces at least one very large moon. However, a new simulation was performed, showing how an impact could create three moons around Mars, where the largest, inner one decays, creating the Martian system we see today. …

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Mars with three moons

The Dark Spot of Mordor


(Syfy Wire::Bad Astronomy) – Phil Plait:

Pluto‘s moon Charon is a mess. It has many striking features, but the polar red spot – Mordor Macula – may be the weirdest. …

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Charon in color

Edge of Darkness


(Guardian Astronomy) – Robin McKie:

It would take a telescope as big as a planet to see the supermassive black hole at the centre of the Milky Way. But a team of scientists think they know how to do it. …

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Black hole in 2014 film Interstellar

An Extremely Faint Neighbour


(Syfy Wire::Bad Astronomy) – Phil Plait:

We can see galaxies billions of light years way, nearly to the edge of the observable Universe, but there can be galaxies literally orbiting our own that have gone unnoticed. Of course, the ones we see at fantastic distances are huge and bright, and the nearby ones small and faint. But still, it shows you that, sometimes, treasures can be found on your doorstep if you just look more carefully. …

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Milky Way and Virgo 1

No Habitable Super-Earths


(Starts With A Bang!) – Ethan Siegel:

Earth is pretty much the limit of how large you can get and still be rocky. Anything much larger, and you’re a gas giant. …

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Planets discovered by Kepler space observatory