A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!
Christopher Nolan, the writer and director of Memento, Inception, and the most recent Batman films, is taking up space on the big screen next year — literally. Nolan’s newest film, Interstellar, will be a space exploration adventure featuring Matthew McConaughey, Jessica Chastain, Anne Hathaway, and Michael Caine (of course) and, based on this teaser trailer, maintains a reverent awareness of the iconic missions of the Space Age.
Artist's impression of a Y-dwarf, the coldest known type of brown dwarf star. (NASA/JPL-Caltech)
When it’s a brown dwarf — but where do we draw the line?
Often called “failed stars,” brown dwarfs are curious cosmic creatures. They’re kind of like swollen, super-dense Jupiters, containing huge amounts of matter yet not quite enough to begin fusing hydrogen in their cores. Still, there has to be some sort of specific tipping point, and astronomers (being the scientists that they are) would like to know: when does a brown dwarf stop and a star begin?
Researchers from Georgia State University now have the answer.
From a press release issued Dec. 9 from the National Optical Astronomy Observatory (NOAO):
For most of their lives, stars obey a relationship referred to as the main sequence, a relation between luminosity and temperature – which is also a relationship between luminosity and radius. Stars behave like balloons in the sense that adding material to the star causes its radius to increase: in a star the material is the element hydrogen, rather than air which is added to a balloon. Brown dwarfs, on the other hand, are described by different physical laws (referred to as electron degeneracy pressure) than stars and have the opposite behavior. The inner layers of a brown dwarf work much like a spring mattress: adding additional weight on them causes them to shrink. Therefore brown dwarfs actually decrease in size with increasing mass.
As Dr. Sergio Dieterich, the lead author, explained, “In order to distinguish stars from brown dwarfs we measured the light from each object thought to lie close to the stellar/brown dwarf boundary. We also carefully measured the distances to each object. We could then calculate their temperatures and radii using basic physical laws, and found the location of the smallest objects we observed (see the attached illustration, based on a figure in the publication). We see that radius decreases with decreasing temperature, as expected for stars, until we reach a temperature of about 2100K. There we see a gap with no objects, and then the radius starts to increase with decreasing temperature, as we expect for brown dwarfs. “
Dr. Todd Henry, another author, said: “We can now point to a temperature (2100K), radius (8.7% that of our Sun), and luminosity (1/8000 of the Sun) and say ‘the main sequence ends there’ and we can identify a particular star (with the designation 2MASS J0513-1403) as a representative of the smallest stars.”
The relation between size and temperature at the point where stars end and brown dwarfs begin (based on a figure from the publication) Image credit: P. Marenfeld & NOAO/AURA/NSF.
“We can now point to a temperature (2100K), radius (8.7% that of our Sun), and luminosity (1/8000 of the Sun) and say ‘the main sequence ends there’.”
Aside from answering a fundamental question in stellar astrophysics about the cool end of the main sequence, the discovery has significant implications in the search for life in the universe. Because brown dwarfs cool on a time scale of only millions of years, planets around brown dwarfs are poor candidates for habitability, whereas very low mass stars provide constant warmth and a low ultraviolet radiation environment for billions of years. Knowing the temperature where the stars end and the brown dwarfs begin should help astronomers decide which objects are candidates for hosting habitable planets.
The data came from the SOAR (SOuthern Astrophysical Research) 4.1-m telescope and the SMARTS (Small and Moderate Aperture Research Telescope System) 0.9-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile.
UV observations from Hubble show the size of water vapor plumes coming from Europa's south pole (NASA, ESA, and M. Kornmesser)
It’s been known since 2005 that Saturn’s 300-mile-wide moon Enceladus has geysers spewing ice and dust out into orbit from deep troughs that rake across its south pole. Now, thanks to the Hubble Space Telescope (after 23 years still going strong) we know of another moon with similar jets: Europa, the ever-enigmatic ice-shelled moon of Jupiter. This makes two places in our Solar System where subsurface oceans could be getting sprayed directly into space — and within easy reach of any passing spacecraft.
(Psst, NASA… hint hint.)
The findings were announced today during the meeting of the American Geophysical Union in San Francisco.
“The discovery that water vapor is ejected near the south pole strengthens Europa’s position as the top candidate for potential habitability,” said lead author Lorenz Roth of the Southwest Research Institute (SwRI) in San Antonio, Texas. “However, we do not know yet if these plumes are connected to subsurface liquid water or not.”
The 125-mile (200-km) -high plumes were discovered with Hubble observations made in December 2012. Hubble’s Space Telescope Imaging Spectrograph (STIS) detected faint ultraviolet light from an aurora at the Europa’s south pole. Europa’s aurora is created as it plows through Jupiter’s intense magnetic field, which causes particles to reach such high speeds that they can split the water molecules in the plume when they hit them. The resulting oxygen and hydrogen ions revealed themselves to Hubble with their specific colors.
Unlike the jets on Enceladus, which contain ice and dust particles, only water has so far been identified in Europa’s plumes. (Source)
Rendering showing the location and size of water vapor plumes coming from Europa’s south pole.
The team suspects that the source of the water is Europa’s long-hypothesized subsurface ocean, which could contain even more water than is found across the entire surface of our planet.
“If those plumes are connected with the subsurface water ocean we are confident exists under Europa’s crust, then this means that future investigations can directly investigate the chemical makeup of Europa’s potentially habitable environment without drilling through layers of ice,” Roth said. “And that is tremendously exciting.”
One other possible source of the water vapor could be surface ice, heated through friction.
Cassini image of ice geysers on Enceladus (NASA/JPL/SSI)
In addition the Hubble team found that the intensity of Europa’s plumes, like those of Enceladus, varies with the moon’s orbital position around Jupiter. Active jets have been seen only when Europa is farthest from Jupiter. But the researchers could not detect any sign of venting when Europa is closer.
One explanation for the variability is Europa undergoes more tidal flexing as gravitational forces push and pull on the moon, opening vents at larger distances from Jupiter. The vents get narrowed or even seal off entirely when the moon is closest to Jupiter.
Still, the observation of these plumes — as well as their varying intensity — only serves to further support the existence of Europa’s ocean.
“The apparent plume variability supports a key prediction that Europa should tidally flex by a significant amount if it has a subsurface ocean,” said Kurt Retherford, also of SwRI.
(Science buzzkill alert: although exciting, further observations will be needed to confirm these findings. “This is a 4 sigma detection, so a small uncertainly that the signal is just noise in the instruments,” noted Roth.)
“If confirmed, this new observation once again shows the power of the Hubble Space Telescope to explore and opens a new chapter in our search for potentially habitable environments in our solar system.”
– John Grunsfeld, NASA’s Associate Administrator for Science
So. Who’s up for a mission to Europa now?(And unfortunately in this case, Juno doesn’t count.)
“Juno is a spinning spacecraft that will fly close to Jupiter, and won’t be studying Europa,” Kurt Retherford told Universe Today. “The team is looking hard how we can optimize, maybe looking for gases coming off Europa and look at how the plasma interacts with environment, so we really need a dedicated Europa mission.”
We couldn’t agree more.
The findings were published in the Dec. 12 online issue of Science Express.
Image credits: Graphic Credit: NASA, ESA, and L. Roth (Southwest Research Institute and University of Cologne, Germany) Science Credit: NASA, ESA, L. Roth (Southwest Research Institute and University of Cologne, Germany), J. Saur (University of Cologne, Germany), K. Retherford (Southwest Research Institute), D. Strobel and P. Feldman (Johns Hopkins University), M. McGrath (Marshall Space Flight Center), and F. Nimmo (University of California, Santa Cruz)
Hubble image of the Horsehead Nebula, "tilt-shifted" by Imgur user ScienceLlama (Original image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA))
Aww, how cute! What an adorable little… nebula?
Although here it may look like it could fit in your hand, the Horsehead Nebula is obviously quite a bit larger – about 1.5 light-years across from “nose” to “mane.” But given a tilt-shift effect by Imgur.com user ScienceLlama, the entire structure takes on the appearance of something tiny — based purely on our eyes’ natural depth-of-field when peering at a small object close up. Usually done with Photoshop filters these days, it’s a gimmick, yes… but it works!
The original image was captured in infrared light by the Hubble Space Telescope and released in April 2013, in celebration of its 23rd anniversary.
Check out more of ScienceLlama’s “tiny universe” images below:
A tiny Centaurus AA tiny Crab Nebula (see original NASA image here)A tiny Andromeda Galaxy in hydrogen alpha (see original here)
ADDITION 12/17: Several of these images (like this one) were originally processed by Robert Gendler from Hubble-acquired data, but the attribution was not noted by ScienceLlama. I apologize for the oversight — see more of Robert’s beautiful astrophotography on his website here. Another original source was Adam Block of the Mount Lemmon Sky Center.
Comet C/2011 W3 (Lovejoy) imaged by the Subaru Telescope on Dec. 3. Image credit: NAOJ with data processing by Masafumi Yagi (NAOJ)
Comet ISON may be no more than just a cloud of icy debris these days but there’s another comet that’s showing off in the morning sky: C/2013 R1 (Lovejoy), which was discovered in September and is steadily nearing its Christmas Day perihelion. In the early hours of Dec. 3, astronomers using the 8.2-meter Subaru Telescope atop Mauna Kea in Hawaii captured this amazing image of Lovejoy, revealing the intricate flows of ion streamers in its tail. (Click the image above for extra awesomeness.)
At the time of this observation, at around 5:30 am on December 3, 2013 (Hawaii Standard Time), Comet Lovejoy was 50 million miles (80 million km) distant from Earth and 80 million miles (130 million km) away from the Sun.
The entire image of comet Lovejoy was made with the Subaru Telescope’s Suprime-Cam, which uses a mosaic of ten 2048 x 4096 CCDs covering a 34′ x 27′ field of view and a pixel scale of 0.2”.
Where to find comet Lovejoy in the morning sky, Dec. 7 (via spaceweather.com)
“Subaru Telescope offers a rare combination of large telescope aperture and a wide-field camera,” said a member of the observation team, which included astronomers from Stony Brook University in New York, Universidad Complutense in Madrid, Johns Hopkins University, and the National Astronomical Observatory of Japan. “This enabled us to capture a detailed look at the nucleus while also photogenically framing inner portions of Comet Lovejoy’s impressive ion tail.”
Comet Lovejoy is currently visible in the early morning sky as a naked-eye object in the northern hemisphere.
Read more about Lovejoy’s journey through the inner solar system in this article by Bob King here.
Image of comet Lovejoy on Dec. 5 by Flickr user Willo2173.
Do you have photos of comet Lovejoy or any other astronomical objects to share? Upload them to the Universe Today Flickr group!
It’s actually remarkably beautiful, and well worth two minutes of your time.*
Assembled from actual photographs taken by astronauts aboard the Space Station, many of them by Don Pettit during Expedition 31 (Don took a lot of photos) this timelapse “The World Outside My Window” by David Peterson ramps up the artistic value by featuring super-duper high definition, smoothed frame transitions and a musical score by “Two Steps From Hell.” (Don’t worry, that sounds scarier than it is.) Even if you’ve seen some of these clips before, they’re worth another go.
After all, there’s no good reason not to be reminded of how beautiful our planet is from space. Enjoy!
*It’s actually two minutes and twenty-eight seconds but I don’t think you’ll mind.
Earlier today the near-Earth asteroid 2013 NJ sailed by, coming as close as 2.5 lunar distances — about 960,000 km/596,500 miles. That’s a relatively close call, in astronomical terms, but still decidedly a miss (if you hadn’t already noticed.) Which is a good thing since 2013 NJ is estimated to be anywhere from 120–260 meters wide (400-850 feet) and would have caused no small amount of damage had its path intersected ours more intimately.
Luckily that wasn’t the case, and instead we get watch 2013 NJ as it harmlessly passes by in the video above, made from images captured by “shadow chaser” Jonathan Bradshaw from his observatory in Queensland, Australia. Nice work, Jonathan!
Keep tabs on known near-Earth objects on the JPL close pass page here.
Comet ISON entered the STEREO scene with Encke on Nov. 21 (Credit: Karl Battams/NASA/STEREO/CIOC)
As comets ISON and Encke continue toward their respective rendezvous with the Sun, they have now both been captured on camera by NASA’s solar-observing STEREO spacecraft. The image above, taken on Nov. 21 (UT) with STEREO-A’s high-resolution HI-1 camera, shows ISON as it enters the field of view from the left. Encke is at center, while the planets Mercury and Earth (labeled) are bright enough to cause vertical disruptions in the imaging sensors. (The Sun is off frame to the right.)
As cool as this image is, it gets even better: there’s a video version. Check it out below:
Animation of STEREO-A images acquired on Nov. 20-21 (Karl Battams/NASA/STEREO/CIOC)
The dark “clouds” coming from the right are density enhancements in the solar wind, causing all the ripples in comet Encke’s tail. (Source)
The position of NASA’s STEREO spacecraft relative to Earth and the Sun on Nov. 22
It’s fascinating to watch how the solar wind shapes and affects the tail of comet Encke… as ISON moves further into view, I’m sure we’ll see similar disruptions in its tail as well. (And look what STEREO-A saw happen to Encke’s tail back in 2007!)
Encke reached the perihelion of its 3.3-year-long orbit on Nov. 21; newcomer ISON will arrive at its on Nov. 28. While it seems to be holding together quite well in these STEREO images, what happens when it comes within 730,000 miles of the Sun next week is still anybody’s guess.
A combined image from the Spitzer, Hubble, and Subaru telescopes show this structure to be three galaxies merging into one (NASA/JPL-Caltech/STScI/NAOJ/Subaru)
An enormous and incredibly luminous distant galaxy has turned out to actually be three galaxies in the process of merging together, based on the latest observations from ALMA as well as the Hubble and Spitzer space telescopes. Located 13 billion light-years away, this galactic threesome is being seen near the very beginning of what astronomers call the “Cosmic Dawn,” a time when the Universe first became illuminated by stars.
“This exceedingly rare triple system, seen when the Universe was only 800 million years old, provides important insights into the earliest stages of galaxy formation during a period known as ‘Cosmic Dawn’ when the Universe was first bathed in starlight,” said Richard Ellis, professor of astronomy at Caltech and member of the research team. “Even more interesting, these galaxies appear poised to merge into a single massive galaxy, which could eventually evolve into something akin to the Milky Way.”
In the image above, infrared data from NASA’s Spitzer Space Telescope are shown in red, visible data from NASA’s Hubble Space Telescope are green, and ultraviolet data from Japan’s Subaru telescope are blue. First discovered in 2009, the object is named “Himiko” after a legendary queen of Japan.
The merging galaxies within Himiko are surrounded by a vast cloud of hydrogen and helium, glowing brightly from the galaxies’ powerful outpouring of energy.
What’s particularly intriguing to astronomers is the noted lack of heavier elements like carbon in the cloud.
“This suggests that the gas cloud around the galaxy is actually quite primitive in its composition,” Ellis states in an NRAO video, “and has not yet been enriched by the products of nuclear fusion in the stars in the triple galaxy system. And what this implies is that the system is much younger and potentially what we call primeval… a first-generation object that is being seen. If true that’s very very exciting.”
Further research of distant objects like Himiko with the new high-resolution capabilities of ALMA will help astronomers determine how the Universe’s first galaxies “turned on”… was it a relatively sudden event, or did it occur gradually over many millions of years?
Watch the full video from the National Radio Astronomy Observatory below:
The research team’s results have been accepted for publication in the Astrophysical Journal.
MESSENGER wide-angle camera images of comets Encke and ISON
Two comets currently on their way toward the Sun have been captured on camera from the innermost planet. The MESSENGER spacecraft in orbit around Mercury has spotted the well-known short-period comet Encke as well as the much-anticipated comet ISON, imaging the progress of each over the course of three days. Both comets will reach perihelion later this month within a week of each other.
While Encke will most likely survive its close encounter to continue along its 3.3-year-long lap around the inner Solar System, the fate of ISON isn’t nearly as certain… but both are making for great photo opportunities!
The figure above shows, on the left, images of comet 2P/Encke on three successive days from Nov. 6 to Nov. 8; on the right, images of C/2012 S1 (ISON) are shown for three successive days from Nov. 9 to Nov. 11. Both appear to brighten a little bit more each day.
MESSENGER image of ISON from Nov. 10 (enlarged detail)
MESSENGER is viewing these comets from a vantage point that is very different from that of observers on Earth. Comet Encke was approximately 0.5 AU from the Sun and 0.2 AU from MESSENGER when these images were taken; the same distances were approximately 0.75 AU and 0.5 AU, respectively, for ISON. More images will be obtained starting on November 16 when the comets should be both brighter and closer to Mercury. (Source: MESSENGER featured image article.)
Encke will reach its perihelion on Nov. 21; ISON on Nov. 28.
“We are thrilled to see that we’ve detected ISON,” said Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER’s role in the ISON observation campaign. “The comet hasn’t brightened as quickly as originally predicted, so we wondered how well we would do. Seeing it this early bodes well for our later observations.”
Comet 2P/Encke photographed on October 30 by Damian Peach.
Unlike ISON, Encke has been known for quite a while. It was discovered in 1786 and recognized as a periodic comet in 1819. Its orbital period is 3.3 years — the shortest period of any known comet — and November 21 will mark its 62nd recorded perihelion. (Source)
“Encke has been on our radar for a long time because we’ve realized that it would be crossing MESSENGER’s path in mid-November of this year,” Vervack explained. “And not only crossing it, but coming very close to Mercury.”
These early images of both comets are little more than a few pixels across, Vervack said, but he expects improved images next week when the comets make their closest approaches to MESSENGER and Mercury.
“By next week, we expect Encke to brighten by approximately a factor of 200 as seen from Mercury, and ISON by a factor of 15 or more,” Vervack said. “So we have high hopes for better images and data.”
– Ron Vervack, JHUAPL
Read more about the MESSENGER cometary observation campaign in the full news release here.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Southwest Research Institute
