Many people worry about the possibility of the end of all life on our planet. However, the Earth is by far the most habitable planet in our solar system and there's no reason to expect that to change for hundreds of millions of years.
The Earth may become uninhabitable between 500 million and a billion years from now. That may seem a short time, when you compare it with the billions of years the Earth has evolved for. But compared with the length of time there have been humans on the Earth it's a very long time.
To get an idea of who may need to deal with this issue, the idea is, to look at the last billion years. And then think about where we or our evolutionary cousins might be after another billion years after that. First some background though.
If you lived on one of Pluto's moons, you might have a hard time determining when, or from which direction, the sun will rise each day. Two of Pluto's moons, Nix and Hydra, wobble unpredictably, according to a new data analysis.
When Curiosity's successor and the ExoMars rover land on Mars around 2021, we will see two different approaches to the search for life on the planet side by side. NASA's mission is the first stage of a sample return program. The ESAs ExoMars rover (in partnership with Russia) will explore Mars in situ for biosignatures as well as drill two meters below the surface. Which is the best approach?
A sample return would be great for geology. But would it help with the search for life on Mars? Or is it more of a technology demo for this?
NaSt1, about 3,000 light years away, was discovered a few decades ago and identified as a Wolf-Rayet star, a rapidly evolving star that is much more massive than our Sun.
Wolf-Rayet stars lose their hydrogen-filled outer layers quickly, exposing a super-hot and extremely bright core where helium is fusing into heavier elements. Typically, Wolf-Rayet stars have two outward flowing lobes of material, but in this case, the Hubble observations revealed a pancake-shaped disk of gas encircling the star. This vast disk is more than 3 billion billion kilometers wide. It seems to have formed in the last few thousand years from an unseen companion star that snacked on its outer atmosphere.
The star is so weird that astronomers have nicknamed it “Nasty 1”.
A remote galaxy shining with infrared light equal to more than 300,000,000,000,000 suns has been discovered using data from NASA's Wide-field Infrared Survey Explorer (WISE. The galaxy, belongs to a new class of objects nicknamed extremely luminous infrared galaxies, or ELIRGs.
The galaxy, known as WISE J224607.57-052635.0, may have a behemoth black hole at its belly, gorging itself on gas, but is certainly the most luminous discovered to-date.
Supermassive black holes grow by drawing gas and matter into a disk around them. The disk heats up to beyond-sizzling temperatures of millions of degrees, blasting out high-energy, visible, ultraviolet, and X-ray light. The light is blocked by surrounding cocoons of dust. As the dust heats up, it radiates infrared light.
Our solar system started as a disk of microscopic dust, gas, and ice around the young Sun and the amazing diversity of planets, moons, asteroids, and comets came from this primitive dust.
NASA's Stardust mission has returned to Earth with samples of comet Wild 2, a comet that originated outside the orbit of Neptune and was subsequently kicked closer to Earth's orbit in 1974 when Jupiter's gravity altered Wild 2's orbit.
This is a question that is frequently asked on Quora, with a different date each time. We get a fair number of quite worried people asking this question, in all seriousness, concerned that Earth is about to be hit by a giant impactor. Sometimes they have read sensational stories by online papers that should know later.
It is easy to keep up to date with potential impact dates by visiting this page, automatically updated for the Sentinel program: Current Impact Risks. Just look and see if there are any entries coloured orange or red. Then look for the predicted date of impact. So far this has never happened.
This is a question which was asked recently on quora: Is it possible to have a moon so reflective that when it reflects the light of the sun, it will be as if it is daylight? Anyway it is a rather fun problem, easy to work out by "back of the envelope calculations", and the answer takes us to some interesting areas of planetary physics.
So, you think you know what a planet looks like? A sphere, perhaps flattened at the poles? But if you've been following recent discoveries of dwarf planets, you may know that rapidly spinning dwarf planets like Haumea typically are rugby ball shaped (triaxial spheroids), rather surprisingly perhaps. So, what other shapes can a planet have? Theory, and experiment with droplets in simulated zero g suggest several exotic possibilities.
In Hal Clement's classic hard science fiction novel Mission of Gravity his explorers discover a rapidly spinning planet, and naturally enough he imagines it as flattened at the poles, in the same way as the Earth but more so
The Andromeda galaxy is our nearest galactic neighbor in space. Though it is 2.5 million light-years away, its spiral of over 100 billion stars makes it visible as a cigar-shaped smudge of light high in the autumn sky.
But there is also something that takes Hubble to notice - a huge bubble of hot, diffuse plasma surrounding it. If we could see that gargantuan halo from Earth, it would appear to be 100 times the angular diameter of the full Moon.
The gargantuan halo can be thought of as the "atmosphere" of a galaxy and is estimated to contain half the mass of the stars in the Andromeda galaxy itself. Astronomers were able to identify the halo by measuring how it filtered the light of distant bright background objects called quasars.