Tag Archives: Oort Cloud

New and very distance outer solar system objects beyond Neptune

Astronomers have discovered several new objects orbiting the Sun at extremely great distances beyond the orbit of Neptune.

The most interesting new discovery is 2014 FE72:

Another discovery, 2014 FE72, is the first distant Oort Cloud object found with an orbit entirely beyond Neptune. It has an orbit that takes the object so far away from the Sun (some 3000 times farther than Earth) that it is likely being influenced by forces of gravity from beyond our Solar System such as other stars and the galactic tide. It is the first object observed at such a large distance.

This research is being done as part of an effort to discover a very large planet, possibly as much as 15 times the mass of Earth, that the scientists have proposed that exists out there.

A stellar fly-by 70,000 years ago

Astronomers have identified a nearby star, now 20 light years away, that 70,000 years ago flew past the solar system at a distance of only 0.8 light years.

The star’s trajectory suggests that 70,000 years ago it passed roughly 52,000 astronomical units away (or about 0.8 light years, which equals 8 trillion kilometers, or 5 trillion miles). This is astronomically close; our closest neighbor star Proxima Centauri is 4.2 light years distant. In fact, the astronomers explain in the paper that they are 98% certain that it went through what is known as the “outer Oort Cloud” – a region at the edge of the solar system filled with trillions of comets a mile or more across that are thought to give rise to long-period comets orbiting the Sun after their orbits are perturbed.

I feel it necessary to note that the Oort Cloud itself has never been directly observed and only exists theoretically based on the random arrival of comets from the outer solar system.

Astronomers have discovered a new dwarf planet about 300 miles wide at the very edge of the solar system.

Astronomers have discovered a new dwarf planet about 300 miles wide at the outer edge of the solar system.

The closest it gets to the Sun is 80 AU, or about 7.4 billion miles. More tantalizing, however,

… the findings also suggest the presence of another large planet in the outer reaches of the solar system. When the authors plotted the motion of Sedna, 2012 VP113, and distant Kuiper belt objects, they noticed some odd behaviors which they couldn’t explain — but which a massive, “super-Earth” planet about 250 AU away could. They note that such a dimly lit planet “would be fainter than current all-sky survey detection limits, as would larger and more distant perturbers” (i.e., planets), so it’s certainly possible… but right now it’s little more than a guess. A weird, intriguing guess.

WISE’s survey of the sky in infrared has now shown that there is no large planet X orbiting beyond Pluto.

WISE’s survey of the sky in infrared has now shown that there is no large planet X orbiting beyond Pluto.

This recent study, which involved an examination of WISE data covering the entire sky in infrared light, found no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (au), and no object larger than Jupiter exists out to 26,000 au. One astronomical unit equals 93 million miles. Earth is 1 au, and Pluto about 40 au, from the sun. “The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” said Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, University Park, Pa., author of a paper in the Astrophysical Journal describing the results.

The theory, popular among planetary scientists and journalists, is that this theorized distant planet would periodically disturb the orbits of comets in the Oort Cloud, sending them raining down on Earth and thus cause the periodic extinction events found in the paleontological record. It was a cute theory, but based on little data. Now we have the data, and no such planet exists.

The data has found a lot of previously unknown nearby stars and brown dwarfs, which is significant in that they are close and can be studied more easily.

Linking mass extinctions to the Sun’s journey in the Milky Way

The Sun's orbit in the Milky Way

In a paper published today on the Los Alamos astro-ph preprint service, astronomers propose that as many as eleven past extinction events can be linked to the Sun’s passage through the spiral arms of the Milky Way. (You can download the paper here [pdf].)

A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy’s various spiral arms.

The figure on the right, from their paper, shows the Sun’s orbit in red over the last half billion years. The Sun’s present position is indicated by the yellow spot, and the eleven extinctions are indicated by the circles.

There are obviously a great deal of uncertainties in this conclusion. Most significantly, the shape and history of the Milky Way remains very much in doubt, especially since we reside within it and cannot really get a good look at it. Though in recent years astronomers have assembled a reasonable image of the galaxy’s shape — a barred spiral with two major arms and several minor ones — this picture includes many assumptions that could very easily be wrong.

Nonetheless, the paper’s conclusions are interesting.
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