November, 2013Archive for

Astronomy News: Comet ISON

Monday, November 25th, 2013

Comets have dazzled stargazers since the first humans started looking to the night sky. Their bright tails streaking across the star speckled blackness of space, triggered by the solar winds and radiation of our Sun. Comets are primarily made up of ice, rock, and gas, and orbit the Sun in very oblong trajectories, often originating thousands of times further away than that of Pluto.

Hubble Space Telescope’s image of Comet ISON

Known formally as C/2012 S1, Comet ISON (So named for the project that discovered it, the International Scientific Optical Network) is a sungrazing comet that is currently on its way around the sun. ISON was discovered on September 21st 2012, and was calculated to enter the inner solar system in late November 2013. It poses no threat to Earth.

ISON may have originated from the Oort Cloud, a massive asteroid belt on the outskirts of our Solar System. It was recently calculated to have an orbital period of more than 400,000 years, which means ISON will not enter the inner solar system for that period of time. There is also a chance ISON’s orbit is so oblong that it may be flung entirely from the solar system altogether.

ISON will reach its closest point to the Sun on November 28th, 2013, at a distance of about 724,000 miles above its surface. This is less than 1.25% the distance between the Sun and the Earth. Because of this extremely close proximity, there is a chance ISON will be melted and/or ripped apart by the Sun’s extreme gravity.

If ISON manages to survive its trip around the Sun, it should be visible to the naked eye during mid December to Early January. Some media outlets have labeled this the ‘Comet of the Century’, claiming it will significantly outshine the moon. This is highly unlikely, as the comet has slowed slightly, which means it has a decreased chance of surviving the solar orbit, and its brightness will not remain as long if it does complete the orbit. Still, latest estimates put its brightness on par with that of Venus, the second brightest object currently in the night sky.

Animated version of ISON’s trajectory

The Biggest in the Universe…

Saturday, November 23rd, 2013

Welcome to the first installment of the Vikings Astronomy Superlative Series. In the coming articles we will evaluate the most mind-blowing facts astronomy has to offer.

Galaxy

The largest galaxy observed in the universe is the ESO 146-IG 005 Galaxy. This galaxy was initially measured by the Gemini South Telescope in 2010, and exists approximately 1.4billion light years from Earth.  The ESO 146-IG 005 galaxy is about 30 trillion solar masses, which is 50 times larger than the Milky Way. It has been increasing its mass since the early stages of the universe by merging with smaller galaxies in its local group.

The most massive spiral galaxy is known as ISOHDFS 27. It is much further from Earth than ESO 146-IG 005, at approximately six billion light years. It is only about four times as large as the Milky Way.

Star

Our sun has a mass of about two nonillion kilograms, or 2,000,000,000,000,000,000,000,000,000,000kg. That’s about 1,300,000 times more massive than the earth. However the sun pales in comparison to the largest stars of our known universe.

NML Cygni is currently the largest known star, a red hypergiant roughly 25-40 times more massive than our sun. Its radius is even more impressive, approximately 1,650 times that of the sun. It is a part of the Milky Way, at about 5,300 light years from earth.

Ceres

Asteroid

The largest asteroid in the solar system is actually considered a dwarf planet. Ceres is 950km (590 mi) in diameter, and has a mass of 9.46×1020 kg. Ceres exists in the asteroid belt, which is an area of the solar system between mars and Jupiter. Ceres accounts for about one third of the entire mass of the asteroid belt. It was discovered on January 1st, 1801 by Guiseppe Piazzi, and was originally classified as a planet. The Dawn spacecraft is currently on its way to Ceres, and should arrive in 2015 to perform observations which will help scientists understand the early solar system. This will be the first time we’ve gotten an up close look at Ceres.

Exoplanet

As we learned in a recent article, there are hundreds of known planets outside of our solar system orbiting nearby stars. Because of the techniques used to find these planets, it is usually much easier to find large ones rather than small ones. Currently the largest confirmed exoplanet is CD-35 2722 b, which is approximately 31 times the size of Jupiter. Jupiter, for reference, has a mass of about 318 Earths. It was discovered in 2011.

Spacecraft

International Space Station

The largest manmade object that exists in space is the International Space Station (ISS). The ISS is a joint effort between multiple space agencies, and has been in space since 1998. It currently has a mass of about 990,000 lbs (450,000 kg). The space station has been slowly adding components since its launch, and may operate until 2028.

Saturn V Rocket During Launch

The largest (and most powerful) rocket ever to launch into space is the Saturn V rocket used by NASA during the late 60’s and early 70’s. It stood 363 feet tall, with a diameter of 33 feet, and weighed in at 6.2 million pounds. It was used during NASA’s Apollo program to launch spacecraft into Low Earth Orbit (LEO) as well as to the moon.

 

A Gauge of Armageddon: The Torino Scale

Thursday, November 21st, 2013

As illustrated often in Hollywood, objects in space pose a serious threat to life on Earth. There are many cases of mass extinctions during our planet’s history caused by collisions with asteroids, the most famous of which being the extinction of the dinosaurs approximately 65 million years ago. Today there are dedicated teams of professional and amateur astronomers keeping a close eye on the night sky for any object in space whose trajectory may cross paths with Earth.

The Torino Scale

As a way of defining the potential threat to Earth caused by a asteroid discovered in space, Professor Richard Binzel of MIT developed a scale to assign a number value to the asteroid’s danger. The scale is from 0 to 10, and takes into account the size, velocity, and probability of impact of an asteroid. The Scale is so named because it was adopted as a standard at a conference on Near Earth Objects (NEOs) in Turin, Italy in 1999.

In general, ratings of 0-1 pose little or no threat to earth due to the significant improbability of impact and/or the small size of the asteroids. Often a “1” rating will drop to 0 after more careful calculations of the trajectory. Ratings of 2-4 pose some danger, either due to the fact that the impact is likely or the asteroid is relatively large. 5-7 are significantly threatening, and could significant regionalized damage. 8-10 are extremely dangerous because of the almost certain likelihood of impact and total kinetic energy of the asteroid. This NASA page has a more verbose breakdown of the Torino Scale levels.

NEO’s

Currently there is only one known object above zero on the Torino scale. 2007 VK184 IS an asteroid discovered in 2007 by the Catalina Sky Survey. It has a very low chance of hitting Earth, approximately 0.055%, and is also relatively small at only 130 meters in diameter. If this asteroid did impact earth, its damage would be fairly local, and not pose an extinction-level threat.

The highest ranking for an object since the Torino Scale’s inception was the asteroid 99942 Apophis. Apophis was discovered in 2004 at the Kitt Peak National Observatory, and has an estimated diameter of 350 meters. Initial estimates of Apophis’ trajectory put the possibility of impact at 1 in 37 in the year 2029. This put Apophis at level 4 on the Torino scale. More accurate calculations of the asteroid’s trajectory show it missing earth, but actually traveling within the distance of some of our satellites on April 13, 2029. Additionally, there will be a second encounter with Apophis again in March 2036, though it will not be as close as the initial pass.

Detection Programs

There are many programs currently underway by the United States as well as other countries to detect dangerous NEOs. The two most successful projects to date are Lincoln Near-Earth Asteroid Research, and the Catalina Sky Survey. These, among other teams, have successfully accounted for approximately 93% of all NEOs over 1km in diameter.

Exoplanets Pt. 2

Thursday, November 14th, 2013

This post is a part of a series on Exoplanets.

It doesn’t take long for us, once we discover our galaxy harbors approximately 160 billion exoplanets, to wonder how many could potentially support life. To answer that question, we need to analyze what we think is necessary for a planet to be habitable.

Liquid Water

Habitable zone for different stars

First and foremost, we think there needs to be some amount of water in liquid form on or beneath the surface of the planet. While complex organisms could utilize another molecule for life, such as methane, life as we know it exists almost anywhere there is liquid water.
In order for a planet to have liquid water on its surface, it needs to exist in what is known as the “habitable zone” (sometimes referred to as the Goldilocks zone). This zone defines the distance a planet must be from its star in order to maintain temperatures between 0° C and 100° C (freezing and boiling points of water). This zone is different for each star, based on the size and temperature of the star. The Earth, for example, exists on the inner edge of the sun’s habitable zone, while Mars exists on the outer edge.

“Rocky” composition

In order to support surface water, a planet must be primarily terrestrial, or made up of hard material like the earth. We have discovered many exoplanets within a star’s habitable zone that are speculated to be gas giants like Jupiter and Saturn.

Orbit

Things start getting a little bit more speculative when we consider what type of planetary motion is required for habitable life. For instance, we believe an exoplanet must have a relatively circular orbit around its parent star in order to remain within the habitable zone. If the planet’s orbit is much more elliptical, it will freeze and evaporate the water on the planet with every revolution around its star. Data collected so far suggests that 90% of all exoplanets have an orbit that is too elongated to support life.

Additionally, we surmise a habitable exoplanet must have some sort of rotation around an axis as it revolves around its star. If the planet does not rotate (it is tidally locked), the side facing the star will be extremely warm, while the dark side will have extremely low temperatures.

Mass

Along with composition, mass is another planetary characteristic scientists believe is crucial to successfully harboring life. If a planet is too small, its gravity will be unable to support an atmosphere which is believed to be crucial for complex life to form. Additionally, smaller planets lack the geological activity also thought to be necessary for life, such as plate tectonics which provide the necessary carbon dioxide into the air to build an atmosphere.

If a planet is too large, its composition will most likely be that of a gas giant, like Jupiter, or an ice giant, like Neptune. Currently we think Earth is at the lower end of the range of habitable planet masses, with some estimates stating a planet ten times the size of our Earth still could be habitable.

Moon?

Some scientists speculate some sort of satellite like our moon is required to sustain life. This is because it plays an important part in stabilizing the tilt of a planet. A chaotic tilt would wreak havoc on the planets climate.

Simple vs. Complex Life

An important detail of the search for life bearing exoplanets is defining exactly what life is. On Earth, life formed approximately 450 million years after the earth did. It did so in the form of simple single-celled organisms. It took another 3.5 billion years for multi-cellular, complex life to evolve. What this indicates is that while it requires a relatively short period of time for life to form, it takes significantly longer for it to form what we would consider today to be “animals”.

Much of the criteria above apply primarily to single celled life. There are additional factors to take into account when searching for complex and intelligent life. We will explore these additional factors, as well as the likelihood of finding intelligent life in the universe in one of our upcoming posts.