It’s one of those rumors that just won’t quiet down — a large planet lurking at the solar system’s edge. Back in the 1840s, when Neptune was discovered, its orbit seemed to be a little “off” from what was expected.
Some astronomers of the time said that was caused by a planet further out. Although the Neptune perturbations are now ascribed to observational errors, the tale of Planet X continues, and has sometimes even been linked with doomsday. (See this past Universe Today story for the full tale.)
NASA’s latest survey puts even less credence in that theory. A scan of the sky showed nothing Saturn’s size or bigger at a distance of 10,000 Earth-sun distances, or astronomical units. Nothing bigger than Jupiter exists as far as 26,000 AU. (To put that in perspective, Pluto is 40 AU from the sun.)
“The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” stated Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, author of a paper in the Astrophysical Journal describing the results.
Astronomers used information from NASA’s Wide-Field Infrared Survey Explorer, which did two full-sky scans in 2010 and 2011 to look at asteroids, stars and galaxies. NASA’s AllWISE program, released in November 2013, allows astronomers to find moving objects by comparing the two surveys.
A second study of the data found other objects further out in space — 3,525 stars and brown dwarfs (objects just below the threshold for fusion) within 500 light-years of the sun.
“We’re finding objects that were totally overlooked before,” stated Davy Kirkpatrick of NASA’s Infrared and Processing Analysis Center at the California Institute of Technology, who led the second paper.
Both papers will be published in the Astrophysical Journal.
NASA’s NEOWISE mission — formerly known as just WISE — has identified the first comet of its new near-Earth object hunting career… and, according to mission scientists, it’s a “weirdo.”
In its former life NASA’s WISE (Wide-field Infrared Survey Explorer) spacecraft scanned the entire sky in infrared wavelengths. It helped discover the galaxy’s coldest stars, the Universe’s brightest galaxies, and some of the darkest asteroids lurking in the main asteroid belt between Mars and Jupiter… as well as closer in to Earth’s neck of the woods.
After exhausting its supply of liquid coolant needed to shield itself from its own radiating heat, in 2011 WISE was put into a state of hibernation. It was awoken last year and rebranded NEOWISE, and set upon the task of locating unknown objects with orbits in the proximity of Earth’s.
To date several new asteroids have already been found by NEOWISE, and on February 14, 2014, it spotted its first comet.
“We are so pleased to have discovered this frozen visitor from the outermost reaches of our solar system,” said Amy Mainzer, NEOWISE principal investigator at JPL. “This comet is a weirdo — it is in a retrograde orbit, meaning that it orbits the sun in the opposite sense from Earth and the other planets.”
Designated “C/2014 C3 (NEOWISE),” the comet was 143 million miles (230 million km) away in the image above — a composite made from six infrared exposures. That’s 585 times the distance to the Moon, or about the average distance between the Earth and Mars.
The tail of the comet NEOWISE extends about 25,000 miles (40,000 km) to the right in the image.
Overall, C/2014 C3 (NEOWISE) was spotted six times before it moved out of range of the spacecraft’s view. The comet has a highly-eccentric 20-year orbit that takes it high above the plane of the Solar System and out past the orbit of Jupiter. Technically, with a perihelion distance greater than 1.3 AU, comet C/2014 C3 does not classify as a near-Earth object (and its orbit does not intersect Earth’s.) But it’s still good to know that NEOWISE is looking out for us.
While we’re unsure about the status of chocolates and flowers in locations far beyond Earth, there certainly is no lack of hearts for us to look at to enjoy Valentine’s Day. If you look at enough geologic features or gas clouds, statistically some of them will take on shapes that we recognize (such as faces).
Below, we’ve collected some hearts on Mars and other places in the universe. Have we missed any? Share other astronomy hearts in the comments!
On the morning of February 15, 2013, people in western Russia were dazzled by an incredibly bright meteor blazing a fiery contrail across the sky. A few minutes later a shockwave struck, shaking the buildings and blowing out windows. 1,500 people went to the hospital with injuries from shattered glass. This was the Chelyabinsk meteor, a chunk of rock that struck the atmosphere going almost 19 kilometers per second. Astronomers estimate that it was 15-20 meters across and weighed around 12,000 metric tonnes.
Here’s the crazy part. It was the largest known object to strike the atmosphere since the Tunguska explosion in 1908. Catastrophic impacts have shaped the evolution of life on Earth. Once every 65 million years or so, there’s an impact so destructive, it wipes out almost all life on Earth. The bad news is the Chelyabinsk event was a surprise. The asteroid came out of nowhere. We need to find all the potential killer asteroids, and understand what risks we face.
“I’m Ned Wright…”
That’s Dr. Ned Wright. He’s a professor of physics and astronomy at UCLA, and the Primary Investigator for the Wide-field Infrared Survey Explorer mission; a space telescope that looks for low temperature objects in the infrared spectrum.
“I think the best way to protect the Earth from asteroids is to get out and look very assiduously to find all the hazardous asteroids. Although astronomers have been finding and cataloging asteroids for decades, we still only have a fraction of the dangerous asteroids tracked. The large continent destroyers have mostly been found, but there’s a whole class of smaller, city killers out there, and they’re almost entirely unknown. There are… these dark asteroids that may not be the most dominant part of the population but they certainly can be a very hazardous subset, it’s important to do the observations in the infrared. So you actually, instead of looking for the ones that reflect the most light, you look for the ones that have the biggest area and therefore the ones that are the heaviest and can do the most damage. And so, I think that an infrared survey is the way to go.”
“In the infrared wavelengths, we can find these objects because they’re large, not because they’re bright. And to really do this right, we need a space-based infrared observatory capable of surveying vast areas of the sky, searching for anything moving.”
The WISE mission has been offline for a few years, but WISE is actually being reactivated right now to look for more Near Earth Objects, so we’re currently cooled down to 93 K, and when we get to 73 K, which is where we were when we turned off in 2011 we’ll probably be able to go out and find more Near Earth Objects.
Note: this interview was recorded in November, 2013. WISE resumed operations in December 23, 2013
But to really find the vast majority of dangerous asteroids, you need a specialized mission. One proposal is the Near Earth Asteroid Camera, or NEOCam because it’d be much better to have a telescope that was slightly colder than the 73 K WISE is with coolant, and you can do that by getting away from the Earth. and so the NEOcam telescope is designed to go a million and a half kilometers from the Earth and therefore it would be quite cold, about 35 K and at that temperature, it can operate longer into the infrared and do a very sensitive survey for asteroids.
NEOCam is just one idea. There’s also the Sentinel proposal from B612 Foundation. It’s also an infrared survey and it would go into an orbit like Venus’ orbit, so it would be hundreds of millions of km away from Earth, but not orbiting around Venus, because that would be too hot as well and then with an infrared telescope, it would survey for asteroids.
NEOCam and Sentinel would operate for years, scanning the sky in the infrared to find all of the really hazardous asteroids. You wouldn’t be able to necessarily find the ones the size of the one that hit Chelyabinsk, and so that broke some windows, but it didn’t kill people, didn’t knock buildings down. So that’s definitely a hazard, but not the city destroying hazard that a 100 meter diameter asteroid would be.
We live in a cosmic shooting gallery. Rocks from space impact the Earth all the time, our next dangerous asteroid is out there, somewhere. Let’s build a space-based infrared survey mission so we can find it, before it finds us.
In 2012 astronomers announced the discovery of an Earth-like planet circling our nearest neighbor, Alpha Centauri B, a mere 4.3 light-years away. But with such a discovery comes heated debate. A second group of astronomers was unable to confirm the exoplanet’s presence, keeping the argument unresolved to date.
But not to worry. One need only look 2.3 light-years further to see tantalizing — although yet unconfirmed — evidence of an exoplanet circling a pair of brown dwarfs: objects that aren’t massive enough to kick-off nuclear fusion in their cores. There just may be an exoplanet in the third closest system to our Sun.
Astronomers only discovered the system last year when the brown dwarfs were spotted in data from NASA’s Wide-field Infrared Explorer (WISE). Check out a past Universe Today article on the discovery here. They escaped detection for so long because they are located in the galactic plane, an area densely populated by stars, which are far brighter than the brown dwarfs.
Henri Boffin at the European Southern Observatory led a team of astronomers on a mission to learn more about these newly found dim neighbors. The group used ESO’s Very Large Telescope (VLT) at Paranal in Chile to perform astrometry, a technique used to measure the position of the objects precisely. This crucial data would allow them to make a better estimate of the distance to the objects as well as their orbital period.
Boffin’s team was first able to constrain their masses, finding that one brown dwarf weighs in at 30 times the mass of Jupiter and the other weighs in at 50 times the mass of Jupiter. These light-weight objects orbit each other slowly, taking about 20 years.
But their orbits didn’t map out perfectly — there were slight disturbances, suggesting that something was tugging on these two brown dwarfs. The likely culprit? An exoplanet — at three times the weight of Jupiter — orbiting one or even both of the objects.
“The fact that we potentially found a planetary-mass companion around such a very nearby and binary system was a surprise,” Boffin told Universe Today.
The next step will be to monitor the system closely in order to verify the existence of a planetary-mass companion. With a full year’s worth of data it will be relatively straightforward to remove the signal caused by the exoplanet.
So far only eight exoplanets have been discovered around brown dwarfs. If confirmed, this planet will be the first to be discovered using astrometry.
“Once the companion is confirmed, this will be an ideal target to image using the upcoming SPHERE instrument on the VLT,” Boffin said. This instrument will allow astronomers to directly image planets close to their host star — a difficult technique worth the challenge as it reveals a wealth of information about the planet.
Once confirmed, this planet will stand as the closest exoplanet to the Sun, until the debate regarding Alpha Centauri Bb is resolved.
The paper has been accepted for publication as an Astronomy & Astrophysics Letter and is available for download here. For more information on Alpha Centauri Bb please read a paper available here and published in the Astrophysical Journal.
Besides being a darn pretty picture of the Helix nebula, this snapshot is a bit of symbolism for NASA. The spacecraft that nabbed this view is called the Wide-field Infrared Survey Explorer, or WISE. If you look very carefully — you may have to click on the picture for a closer view — you can see little dots showing the paths of asteroids in the picture. (The streaks are cosmic rays and satellites.)
WISE has an interesting history. It began as a telescope seeking secrets of the universe in infrared light, but ran out of coolant in 2010 and was repurposed for asteroid searching under the NEOWISE mission. It wrapped up its mission, was put into hibernation in February 2011, then reactivated this August to look for asteroids again for at least the next three years. You can see some pictures and data WISE collected during its mission below the jump.
It’s a nice way, NASA said, to celebrate the fourth anniversary of WISE’s launch. “WISE is the spacecraft that keeps on giving,” said Ned Wright of UCLA, who was the principal investigator of WISE before it transitioned into NEOWISE.
Two black holes in the middle of a galaxy are gravitationally bound to each other and may be starting to merge, according to a new study.
Astronomers came to that conclusion after studying puzzling behavior in what is known as WISE J233237.05-505643.5, a discovery that came from NASA’s Wide-field Infrared Survey Explorer (WISE). Follow-up studies came from the Australian Telescope Compact Array and the Gemini South telescope in Chile.
“We think the jet of one black hole is being wiggled by the other, like a dance with ribbons,” stated research leader Chao-Wei Tsai of NASA’s Jet Propulsion Laboratory. “If so, it is likely the two black holes are fairly close and gravitationally entwined.”
“The dance of these black hole duos starts out slowly, with the objects circling each other at a distance of about a few thousand light-years,’ NASA added in a press release. “So far, only a few handfuls of supermassive black holes have been conclusively identified in this early phase of merging. As the black holes continue to spiral in toward each other, they get closer, separated by just a few light-years. ”
As the name implies, a brown dwarf is small… only about 7% the size of the Sun. As far as stellar senior citizens go, they’re cool. Zipping along through space at speeds of 100 to 200 kilometers per second, they may have formed back when our galaxy was young – perhaps 10 billion years ago. Now a team of astronomers headed by Dr. David Pinfield at the University of Hertfordshire has identified a pair of the oldest brown dwarfs known… a set of orbs which could be the harbinger of a huge amount of new, unseen objects.
Although we sometimes refer to them as stars, brown dwarfs are in a class of their own. Because they didn’t ignite in nuclear fusion, they don’t generate internal heat like an ordinary star. After they are formed, they continue to cool and fade as time passes. This process makes them very difficult to observe and the discovery of two very old brown dwarfs, with temperatures of 250-600 C is cause for astronomical excitement.
Just how did Pinfield’s team pick such tiny objects out of the vastness of space? The discovery was facilitated thanks to a survey made by the Wide-field Infrared Survey Explorer (WISE), a NASA observatory that scanned the mid-infrared sky from orbit in 2010 and 2011. The ancient objects are cataloged as WISE 0013+0634 and WISE 0833+0052, and they are located in the constellations of Pisces and Hydra. Because they are so elusive, they were also confirmed by large ground-based telescopes (Magellan, Gemini, VISTA and UKIRT).
However, identifying the pair wasn’t easy. Seeing through the eyes of infrared reveals a crowded space – one populated with reddened stars, distant background galaxies and pockets of nebulous gas and dust. Picking out such a small character from a stellar cast would be like finding one tiny pearl in the vastness of an ocean. But Pinfield’s researchers employed a new method which utilizes WISE’s capabilities. As it scanned the sky over and over again, it revealed the cool, brown dwarfs – picking up the faint signature that other searches had missed.
These two particular brown dwarfs are different from the other slow movers of their type. By studying their spectra, the astronomers have identified atmospheres almost entirely comprised of hydrogen. This sets them apart from younger stars which have an abundance of heavier elements. Does being lighter make them speedier? According to Pinfield, “Unlike in other walks of life, the galaxy’s oldest members move much faster than its younger population.”
Stars near to Sun are considered the “local volume” and are created with three overlapping populations – the thin disk, the thick disk and the halo. Each of these layers has a certain amount of age associated with it: the oldest being the thickest and its member stars move up and down at a higher rate of speed. The halo contains both disks, along with the initial materials which formed the very first stars. Thin disk objects abound in the local volume and account for about 97% of the local stars, while thick disk and halo objects are a meager 3%. Chances are, brown dwarfs belong to that smaller percentage which explains why these fast-moving thick-disk/halo objects are only now being revealed.
Just how many may await discovery? Scientists surmise there may be as many as 70 billion brown dwarfs in the galaxy’s thin disk, and the thick disk and halo take up significantly larger galactic volumes. Even at a tiny 3%, this means there could be an army of ancient brown dwarfs in the galaxy. “These two brown dwarfs may be the tip of an iceberg and are an intriguing piece of astronomical archaeology,” said Pinfield. “We have only been able to find these objects by searching for the faintest and coolest things possible with WISE. And by finding more of them we will gain insight into the earliest epoch of the history of the galaxy.”
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In perhaps the neatest astronomical application of geneology yet, astronomers found 28 “hidden” families of asteroids that could eventually show them how some rocks get into orbits that skirt the Earth’s path in space.
From scanning millions of snapshots of asteroid heat signatures in the infrared, these groups popped out in an all-sky survey of asteroids undertaken by NASA’s orbiting Wide-Field Infrared Survey Explorer. This survey took place in the belt of asteroids between Mars and Jupiter, where most near-Earth objects (NEOs) come from.
NEOs, to back up for a second, are asteroids and comets that approach Earth’s orbit from within 28 million miles (45 million kilometers). Sometimes, a gravitational push can send a previously unthreatening rock closer to the planet’s direction. The dinosaurs’ extinction roughly 65 million years ago, for example, is widely attributed to a massive rock collision on Earth.
There are about 600,000 known asteroids between Mars and Jupiter, and the survey looked at about 120,000 of them. Astronomers then attempted to group some of them into “families”, which are best determined by the mineral composition of an asteroid and how much light it reflects.
While it’s hard to measure reflectivity in visible light — a big, dark asteroid reflects a similar amount of light as a small shiny one — infrared observations are harder to fool. Bigger objects give off more heat.
This allowed astronomers to reclassify some previously studied asteroids (which were previously grouped by their orbits), and come up with 28 new families.
“This will help us trace the NEOs back to their sources and understand how some of them have migrated to orbits hazardous to the Earth,” stated Lindley Johnson, NASA’s program executive for the Near-Earth Object Observation Program.
The astronomers next hope to study these different families to figure out their parent bodies. Astronomers believe that many asteroids we see today broke off from something much larger, most likely through a collision at some point in the past.
While Earthlings will be most interested in how NEOs came from these larger bodies and threaten the planet today, astronomers are also interested in learning how the asteroid belt formed and why the rocks did not coalesce into a planet.
The prevailing theory today says that was due to influences from giant Jupiter’s strong gravity, which to this day pulls many incoming comets and asteroids into different orbits if they swing too close. (Just look at what happened to Shoemaker-Levy 9 in 1994, for example.)