planetesimal

Mysterious and Well-Preserved Oort Cloud Object Heading Into Our Solar System

What if we could journey to the outer edge of the Solar System – beyond the familiar rocky planets and the gas giants, past the orbits of asteroids and comets – one thousand times further still – to the spherical shell of icy particles that enshrouds the Solar System. This shell, more commonly known as the Oort cloud, is believed to be a remnant of the early Solar System.

Imagine what astronomers could learn about the early Solar System by sending a probe to the Oort cloud! Unfortunately 1-2 light years is more than a little beyond our reach. But we’re not entirely out of luck. 2010 WG9 – a trans-Neptunian object — is actually an Oort Cloud object in disguise. It has been kicked out of its orbit, and is heading closer towards us so we can get an unprecedented look.

But it gets even better! 2010 WG9 won’t get close to the Sun, meaning that its icy surface will remain well-preserved. Dr. David Rabinowitz, lead author of a paper about the ongoing observations of this object told Universe Today, “This is one of the Holy Grails of Planetary Science – to observe an unaltered planetesimal left over from the time of Solar System formation.”

Read More.

Peer Pressure keeps young planets growing

External image

Why don’t young planets get pushed into their companion stars before they have a chance to grow? Astronomers believe that planets form in a disk of gas and dust surrounding a young star. The first step towards planet formation is the planetesimal – a small rocky body with radius of roughly 1–10 km. As the dust condenses into planetesimals during the first few million years of a star’s life, larger rocks begin to emerge that grow much more rapidly than the rest. These bodies, termed oligarchs, are on their way to young planethood, using their gravitational pull to attract and pack on more planetesimals.

In addition to providing a means for growth, planetesimals can also push an oligarch towards its doom in the central star. A lone oligarch orbiting through the disk of planetesimals clears a path much like a stick being dragged through sand. The planetesimals on either side of the trench press on the oligarch, and as the outer ring has more mass, the planetesimals deliver a net inward push.

In the past, magnetic fields, turbulence and thermodynamics have been used to explain how rocky planets are prevented from falling into their stars. However, a new study by Bromley and Kenyon say that the wake patterns created by multiple oligarchs circling a star are enough to prevent structures from forming in the planetesimal disk that would push the young planets in.

Once the oligarchs account for about half of the material in the disk, a few tens of millions of years after the birth of the star, they begin making even more material gains by combining with one another. Rather than hollowing out a series of trenches, the oligarchs are now randomly scrawling in the planetesimal “sand”, which also prevents the planetesimals from settling into patterns that would feed the oligarchs to the star.

google.com
New views of giant asteroid Vesta revealed

External image

(This image released Monday, Dec. 5, 2011, by the Dawn spacecraft shows the surface of the massive asteroid Vesta. Credit: AP Photo/NASA)

“New views of the massive asteroid Vesta reveal it is more like a planet than an asteroid, scientists said Monday.”

“Since slipping into orbit around Vesta in July, NASA’s Dawn spacecraft has beamed back stunning images of the second largest object residing in the asteroid belt.”

“Vesta’s rugged surface is unique compared to the solar system’s much smaller and lightweight asteroids. Impact craters dot Vesta’s surface along with grooves, troughs and a variety of minerals.”

“‘Vesta is unlike any other asteroid,’ said mission co-scientist Vishnu Reddy of the Max Planck Institute for Solar System Research in Germany. The new findings were presented at a meeting of the American Geophysical Union in San Francisco.”

2010 WG9 & The Oort Cloud

Somewhere beyond the orbit of Neptune is a treasure-trove just waiting to be opened – and I’m not talking about Pluto. Astronomers have identified the trans-Neptunian object 2010 WG9; it’s certainly an awesome find. Dr. David Rabinowitz believes 2010 WG9 isn’t any regular trans-Neptunian object, but rather an object from the Oort cloud that has ventured closer to home.

To read the full article, see: http://www.fromquarkstoquasars.com/2010-wg9-the-oort-cloud/

Phoebe was on her way to becoming a planet

NASA’s Cassini probe has recently revealed that Saturn’s moon Phoebe may be more like a planet than previously expected. The moon is likely a planetesimal – a body that evolved quickly and actively during the early life of the solar system; that has chemical, geological, and geophysical properties similar to planets; and that may have evolved into a planet, had its development not stalled out.

(Image from Science Daily)

So awhile ago I posted about a position I’ll be starting soon at my department. It’s to help building a new type of telescope detector (already 10/10 coolness) and will involve everything from programming to rigging cryogenics systems to the parts and freezing them to a temperature so cold that it doesn’t exist naturally (so unless there are aliens doing this stuff somewhere, it’ll be one of the coldest places in the universe inside this thing).

What this thing will be able to do is scan the sky with incredible speed and power in addition to doing cool things like making observations through things (like clouds of dust and gas). Once we’re done there will be a telescope on Earth capable of staring into a protoplanetary disc, looking through the dust, and observing the planetesimals inside. We’ll be able to learn about comets by remotely sifting through the material in their tails. We’ll learn about how stars are born and how the universe has evolved. We’ll bring new things to the table and share them with the world.

The telescope we’ll be installing this on is in Mexico on top of a dormant volcano, Sierra Negra, four hours away from Mexico City:

(You can see the telescope at the summit on the left)

(Image credit: David Tuggy)

The telescope itself is known as the Large Millimeter Telescope, and it’s one of the largest single-aperture telescopes on Earth. From the top of Serra Negra you can see incredible amounts of stars and I look forward to seeing it in person when our lab work is finished.

(Image credit: Dr. James Lowenthall)

Needless to say, I’m psyched. The project is the first major opportunity I’ve had to do actual work in the field. I started studying astronomy when I started this blog and I’m sort of amazed there are still a bunch of you from back then who sticking around.

It’s been, is and will be an amazing adventure.

2

ALMA finds unexpected trove of gas around larger stars


Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) surveyed dozens of young stars – some Sun-like and others approximately double that size – and discovered that the larger variety have surprisingly rich reservoirs of carbon monoxide gas in their debris disks. In contrast, the lower-mass, Sun-like stars have debris disks that are virtually gas-free.

This finding runs counter to astronomers’ expectations, which hold that stronger radiation from larger stars should strip away gas from their debris disks faster than the comparatively mild radiation from smaller stars. It may also offer new insights into the timeline for giant planet formation around young stars.

Debris disks are found around stars that have shed their dusty, gas-filled protoplanetary disks and gone on to form planets, asteroids, comets, and other planetesimals. Around younger stars, however, many of these newly formed objects have yet to settle into stately orbits and routinely collide, producing enough rubble to spawn a “second-generation” disk of debris.

“Previous spectroscopic measurements of debris disks revealed that certain ones had an unexpected chemical signature suggesting they had an overabundance of carbon monoxide gas,” said Jesse Lieman-Sifry, lead author on a paper published in Astrophysical Journal. At the time of the observations, Lieman-Sifry was an undergraduate astronomy major at Wesleyan University in Middletown, Connecticut. “This discovery was puzzling since astronomers believe that this gas should be long gone by the time we see evidence of a debris disk,” he said.

In search of clues as to why certain stars harbor gas-rich disks, Lieman-Sifry and his team surveyed 24 star systems in the Scorpius-Centaurus Association. This loose stellar agglomeration, which lies a few hundred light-years from Earth, contains hundreds of low- and intermediate-mass stars. For reference, astronomers consider our Sun to be a low-mass star.

The astronomers narrowed their search to stars between five and ten million years old – old enough to host full-fledged planetary systems and debris disks – and used ALMA to examine the millimeter-wavelength “glow” from the carbon monoxide in the stars’ debris disks.

The team carried out their survey over a total of six nights between December 2013 and December 2014, observing for a mere ten minutes each night. At the time it was conducted, this study constituted the most extensive millimeter-wavelength interferometric survey of stellar debris disks ever achieved.

Armed with an incredibly rich set of observations, the astronomers found the most gas-rich disks ever recorded in a single study. Among their sample of two dozen disks, the researchers spotted three that exhibited strong carbon monoxide emission. Much to their surprise, all three gas-rich disks surrounded stars about twice as massive as the Sun. None of the 16 smaller, Sun-like stars in the sample appeared to have disks with large stores of carbon monoxide.

This finding is counterintuitive because higher-mass stars flood their planetary systems with energetic ultraviolet radiation that should destroy the carbon monoxide gas lingering in their debris disks. This new research reveals, however, that the larger stars are somehow able to either preserve or replenish their carbon monoxide stockpiles.

“We’re not sure whether these stars are holding onto reservoirs of gas much longer than expected, or whether there’s a sort of ‘last gasp’ of second-generation gas produced by collisions of comets or evaporation from the icy mantles of dust grains,” said Meredith Hughes, an astronomer at Wesleyan University and coauthor of the study.

The existence of this gas may have important implications for planet formation, says Hughes. Carbon monoxide is a major constituent of the atmospheres of giant planets. Its presence in debris disks could mean that other gases, including hydrogen, are present, but perhaps in much lower concentrations. If certain debris disks are able to hold onto appreciable amounts of gas, it might push back astronomers’ expected deadline for giant planet formation around young stars, the astronomers speculate.

“Future high-resolution observations of these gas-rich systems may allow astronomers to infer the location of the gas within the disk, which may shed light on the origin of the gas,” says co-author Antonio Hales, an astronomer with the Joint ALMA Observatory in Santiago, Chile, and the National Radio Astronomy Observatory in Charlottesville, Virginia. “For instance, if the gas was produced by planetesimal collisions, it should be more highly concentrated in regions of the disk where those impacts occurred. ALMA is the only instrument capable of making these kind of high-resolution images.”

According to Lieman-Sifry, these dusty disks are just as diverse as the planetary systems they accompany. The discovery that the debris disks around some larger stars retain carbon monoxide longer than their Sun-like counterparts may provide insights into the role this gas plays in the development of planetary systems.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

anonymous asked:

What is your opinion on Pluto not being considered a real planet?

Well. Actually it is a real planet. A dwarf planet. It’s a celestial body orbiting a star (in this case the sun) that is massive enough to be rounded by its own gravity but has not cleared its neighboring region of planetesimals (in this case Neptune) and is not a satellite. More explicitly, it has to have sufficient mass to overcome its compressive strength and achieve hydrostatic equilibrium- which it does. A dwarf planet is still a planet. There’s actually a lot of dwarf planet a ways past Pluto that we haven’t been able to reach yet, but there are quite a few pictures.