Saturday, January 24, 2015

What if the Moon suddenly disappeared?

What if we had no Moon?
Or what if the we had a Moon like we do now and it suddenly disappeared?
Find out what would happen.

1.) There’d be no such thing as eclipses on Earth.
Without the Sun, Moon and Earth, there would be no eclipses. The Sun is constantly shining on Earth, casting a shadow for over a million miles (and over a million kilometers) in its wake. Yet without our Moon — just a few hundred thousand miles (or kilometers) away — there’d be no object that would pass through the Earth’s shadow; there’d be no lunar eclipses.
There’d also be no solar eclipses: no annular, partial, or total eclipses. The Moon’s shadow is almost exactly equal in length to the Earth-Moon distance; without the Moon, no shadow, and no disc to block the Sun’s disk. The next largest object that can pass in between the Earth (after the Moon) is Venus, and while it’s incredibly cool when that happens, that’s the closest we’d get to an eclipse without the Moon.

Wednesday, January 21, 2015

The mystery known as Sedna

90377 Sedna is a large planetoid in the outer reaches of the Solar System that was, as of 2012, about three times as far from the Sun as Neptune. Spectroscopy has revealed that Sedna's surface composition is similar to that of some other trans-Neptunian objects, being largely a mixture of water, methane and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. It is most likely a dwarf planet.

Artist's conception of the surface of Sedna, with the Milky Way, Antares, the Sun and Spica above
Astronomer Michael E. Brown, co-discoverer of Sedna and the dwarf planets Eris, Haumea, and Makemake, believes it to be the most scientifically important trans-Neptunian object found to date, because understanding its unusual orbit is likely to yield valuable information about the origin and early evolution of the Solar System.

Thursday, January 15, 2015

Nemesis: The Solar System's Second Star

In 1983, a scientist named Richard Muller came up with an interesting theory to explain the almost regular intervals between mass extinctions on Earth.

Roughly every 26 million years, the Earth suffers a massive extinction event in which whole species and ecosystems disappear.  It's widely believed and accepted by the scientific community  that the extinction events are precipitated by the impacts of comets and asteroid impacts, but what Muller devised to explain the almost regular event was rather scandalous - what if the sun had an evil twin brother?

Saturday, January 10, 2015

VY Canis Majoris

Of all known stars, the VY Canis Majoris is the largest. This red Hypergiant star, found in the constellation Canis Major, is estimated to have a radius at least 1,800 that of the Sun’s. In astronomy-speak we use the term 1,800 solar radii to refer to this particular size. Although not the most luminous among all known stars, it still ranks among the top 50.

Hypergiants are the most massive and luminous of stars. As such, they emit energy at a very fast rate. Thus, hypergiants only last for a few million years. Compare that to the Sun and similar stars that can keep on burning up to 10 billion years. VY Canis Majoris a.k.a. VY CMa is about 4,900 light years from the Earth.

The radius has been estimated to come in at about 8.2AU (possibly even up to 10.2AU!), but the term, ‘surface,’ has no real definition here. You see, in the outer layers of the star, its density is so low, that it may be more comparable to a vacuum than a star. Its gargantuan size and properties have even sparked debate as to whether or not we can consider it a definite star, or if its more akin to a spherical nebula burning at 3000k! It is generally agreed that it is a star – and it isn’t alone. VY CMa belongs to a very exclusive group of stars, dubbed hypergiants. Hypergiants are so massive that they devour themselves at exponential rates – in other words, the amount of energy our Sun emits in year is equal to what a hypergiant would release in just 6 seconds.

Wednesday, January 7, 2015

Falling into a black hole: The singularity and spagettification

If you were falling toward a black hole, most of the time you would simply feel weightless. The gravity of a black hole is just like the gravity of any other large mass, as long as you don’t get too close.

Suppose you were falling feet first toward a black hole. As you got closer, your feet would feel a stronger force than your head, for example. These differences in forces are called tidal forces. Because of the tidal forces it would feel as if you are being stretched head to toe, while your sides would feel like they are being pushed inward. Eventually the tidal forces would become so strong that they would rip you apart. This effect of tidal stretching is sometimes referred to as spaghettification.

Black Hole versus the Earth

There are two predominant types of black hole in the universe. The first are supermassive black holes found churning at the centre of galaxies. These don’t really pose any threat to us, until our galaxy collides with another like the Andromeda galaxy in a few billion years.

The other type are interstellar black holes, those formed when a large star goes supernova. These can be just a dozen or so miles across, with one of the closest to us being Cygnus X-1 about 6,000 light-years away measuring 44 kilometres (27 miles) in diameter. If a black hole like Cygnus X-1 were to stray near the Solar System, within a light-year or so, its gravity would cause chaos. The orbits of the outer planets and comets would be significantly and possibly disastrously altered, and this would in turn threaten the orbits of the inner planets and even the Sun. However, if the black hole passed directly through the Solar System, then things get immeasurably worse.

Sunday, January 4, 2015

The Oort Cloud vs Kuiper Belt

  • The Kuiper Belt and the Oort Cloud are regions of space. The known icy worlds and comets in both regions are much smaller than Earth's moon. 
  • The Kuiper Belt and the Oort Cloud surround our sun, a star. The Kuiper Belt is a doughnut-shaped ring, extending just beyond the orbit of Neptune from about 30 to 55 AU. The Oort Cloud is a spherical shell, occupying space at a distance between five and 100 thousand AU.
  • Long-period comets (which take more than 200 years to orbit the sun) come from the Oort Cloud. Short-period comets (which take less than 200 years to orbit the Sun) originate in the Kuiper Belt.