Jupiter: Guardian or Menace?

The 5th “rock” from our sun is actually a huge ball of hydrogen and helium. 2.5 times larger than all the other planets in our solar system combined, it is no surprise that Jupiter has the largest gravitational pull of any other object besides the sun itself. Almost 1 year ago it was hit by a rogue 1600 ft asteroid that caused a blemish the size of the Pacific Ocean in it’s atmosphere that was even visible to backyard astronomers. And just a few days ago, in a major coincidence as images from last year’s collision are released, another space rock made its final collision with the gas giant, captured separately by two backyard stargazers from Broken Hill, Australia and Cebu, Philippines.

This close frequency between Jovian impacts is puzzling to scientists who thought such events were relatively rare. In fact, after the much publicized Shoemaker-Levy 9 collision of 1994, astronomers had thought that it would be 50 to 250 years before the next impact. It also brings to mind a pertinent question; What is the effect of Jupiter on asteroid collisions on our own terra firma? Traditionally, Jupiter has been viewed as a shield that protects Earth from asteroids and comets by pulling them towards its massive gravitational well. However, this view is changing with research by Horner and Jones of Open University. According to Hal Levison of Southwest Research Institute who studies the evolution of our solar system, Jupiter is both a guardian and a menace, depending on where the space rock comes from.

The asteroid belt that lies between the orbits of Mars and Jupiter exists because the latter’s gravitational pull prevented the formation of a protoplanet. Jupiter probably has a harmful effect to us if the object comes from the Kuiper belt (shown in green below), a massive band of small asteroid-like bodies which lies beyond Neptune. This is also where our dwarf planets such as Pluto, Haumea and Makemake reside. The gravitational effect of Jupiter probably increases our exposure to the comets and asteroids from this band.

But beyond the Kuiper belt lies an even bigger threat. This is the hypothesized cloud of comets that lies almost a light year beyond the solar system – the Oort Cloud. This far away from the sun, they are susceptible to the gravitational effects of passing stars, and when that happens a stray Oort Cloud object could be sent spiraling towards us. The effect of Jupiter is such that it has kept most of these objects out of the solar system in the first place. Moreover it can deflect these objects when they come too close to the solar system.

Therefore, it seems Jupiter has both a positive and negative effect on asteroid and comet impacts on Earth. Although it increases the likelihood of collisions from the Kuiper Belt, it protects us from the bigger threat of Oort Cloud objects that are difficult to track due to their great distance.

How to Colour Space Mountains

Hubble celebrated its 20th anniversary last week and released a stunning new photo! This pillar of gas and dust in the Carina Nebula stretches three light years tall and represents a chaotic scene where new primordial stars are formed.

Have you ever wondered how colours are created for this composite image? The Hubble telescope actually takes pictures by recording light using electronic detectors on its camera. These produce images in black and white.

Natural coloured images are created to allow us to see what an object would look like as if it were right  before our eyes. To make this happen, three black and white images are taken from the visible spectrum of filtered light. They represent red light, blue light and green light coming from the galaxy. These images are then combined to give a final product. Why do most galaxies appear white? this is because galaxies are made up of millions of stars of different colours which when combined produce a white appearance.

So how do we get magnificent images like that of the Carina Nebula? Those are enhanced images. In star forming nebulas there is an abundance of hydrogen gas which glows in visible light because of the ultraviolet rays coming from the nascent stars. Three black and white photos of filtered visible light are again taken. But this time, red light from hydrogen atoms is represented as green in the final image, red light from sulfur atoms as red, and green light from oxygen atoms as blue. These colour reassignments help astronomers differentiate the red light from hydrogen and sulfur atoms and thus enhance the level detail of the final image.

Source: http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/