Comets can spend billions of years out in the Oort Cloud, and then a few brief moments of terror orbiting the Sun. These are the sun grazers. Some survive their journey, and flare up to become the brightest comets in history. Others won’t survive their first, and only encounter with the Sun.
Continue reading “Astronomy Cast 324: Sun Grazers”
How Does a Star Form?
We owe our entire existence to the Sun. Well, it and the other stars that came before. As they died, they donated the heavier elements we need for life. But how did they form?
Stars begin as vast clouds of cold molecular hydrogen and helium left over from the Big Bang. These vast clouds can be hundreds of light years across and contain the raw material for thousands or even millions of times the mass of our Sun. In addition to the hydrogen, these clouds are seeded with heavier elements from the stars that lived and died long ago. They’re held in balance between their inward force of gravity and the outward pressure of the molecules. Eventually some kick overcomes this balance and causes the cloud to begin collapsing.
That kick could come from a nearby supernova explosion, collision with another gas cloud, or the pressure wave of a galaxy’s spiral arms passing through the region. As this cloud collapses, it breaks into smaller and smaller clumps, until there are knots with roughly the mass of a star. As these regions heat up, they prevent further material from falling inward.
At the center of these clumps, the material begins to increase in heat and density. When the outward pressure balances against the force of gravity pulling it in, a protostar is formed. What happens next depends on the amount of material.
Some objects don’t accumulate enough mass for stellar ignition and become brown dwarfs – substellar objects not unlike a really big Jupiter, which slowly cool down over billions of years.
If a star has enough material, it can generate enough pressure and temperature at its core to begin deuterium fusion – a heavier isotope of hydrogen. This slows the collapse and prepares the star to enter the true main sequence phase. This is the stage that our own Sun is in, and begins when hydrogen fusion begins.
If a protostar contains the mass of our Sun, or less, it undergoes a proton-proton chain reaction to convert hydrogen to helium. But if the star has about 1.3 times the mass of the Sun, it undergoes a carbon-nitrogen-oxygen cycle to convert hydrogen to helium. How long this newly formed star will last depends on its mass and how quickly it consumes hydrogen. Small red dwarf stars can last hundreds of billions of years, while large supergiants can consume their hydrogen within a few million years and detonate as supernovae. But how do stars explode and seed their elements around the Universe? That’s another episode.
We have written many articles about star formation on Universe Today. Here’s an article about star formation in the Large Magellanic Cloud, and here’s another about star formation in NGC 3576.
Want more information on stars? Here’s Hubblesite’s News Releases about Stars, and more information from NASA’s imagine the Universe.
We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?
Source: NASA
Virtual Star Party – December 1, 2013 – Dying Comets, Smashing Galaxies and Cosmic Bees
Hosts: Fraser Cain and Scott Lewis
Astronomers: Gary Gonella, Roy Salisbury, Steven Coates, Tom Nathe, Stuart Foreman
Continue reading “Virtual Star Party – December 1, 2013 – Dying Comets, Smashing Galaxies and Cosmic Bees”
Spectacular Liftoff Thrusts China’s First Rover ‘Yutu’ to the Moon
Liftoff of China’s first ever lunar rover on Dec. 2 local Beijing time from the Xichang Satellite Launch Center, China. Credit: CCTV
Story updated
See stunning launch video and rover deployment animation below[/caption]
CAPE CANAVERAL, FL – China successfully launched its first ever lunar rover bound for the Moon’s surface aboard a Long March rocket today at 1:30 a.m. Beijing local time, Dec. 2, 2013 (12:30 p.m. EST, Dec. 1) from the Xichang Satellite Launch Center in southwest China.
The spectacular night time blastoff of the Long March-3B carrier rocket with the ‘Yutu’ rover was carried live on China’s state run CCTV enabling viewers worldwide to watch the dramatic proceedings as they occurred in real time – including fantastic imagery of booster jettison, spacecraft separation, thruster firings and exquisite views of Earth from cameras aboard the booster.
See the stunning launch video below.
Video caption: China’s Chang’e-3 Lunar Probe Launch on Dec 2, 2013. Credit: CCTV
The entire flight sequence proceeded flawlessly and placed the combined Chang’e 3 lunar landing vehicle and ‘Yutu’ rover on the desired earth-moon transfer orbit following spacecraft separation and unfurling of the life giving solar panels and landing legs, announced Zhang Zhenzhong, director of the Xichang center.
“The Chang’e probe is on its way to the moon, of course, is a symbol of China’s national prowess,” said Zhang Zhenzhong through a translator during the live CCTV broadcast. “Of course, it’s a symbol of China’s national power and prowess.”
The three stage 55 meter (185 foot) tall Long March-3B carrier rocket was uniquely equipped with a quartet of strap on liquid fueled boosters to provide the additional liftoff thrust required for the four day journey to Earth’s Moon.
The name for the ‘Yutu’ rover – which translates as ‘Jade Rabbit’ – was chosen after a special naming contest involving a worldwide poll and voting to select the best name.
‘Yutu’ stems from a Chinese fairy tale, in which the goddess Chang’e flew off to the moon taking her little pet Jade rabbit with her.
The Chang’e 3 lander will fire thrusters to enter lunar orbit on Dec. 6.
It is due to make a powered descent to the lunar surface on Dec. 14, firing thrusters at an altitude of 15 km (9 mi) for touchdown in a preselected area called the Bay of Rainbows or Sinus Iridum region.
If successful, the Chang’e 3 mission will mark the first soft landing on the Moon since the Soviet Union’s unmanned Luna 24 sample return vehicle landed nearly four decades ago back in 1976.
‘Yutu’ is sitting atop the 4 legged landing probe during the launch and voyage to the Moon.
A complex maneuver will be used to deploy the six-wheeled ‘Jade Rabbit’ rover. It will be lowered in stages to the moon’s surface and then drive off a pair of landing ramps to explore the moon’s terrain.
Watch this short CCTV news report with a cool animation showing how the ‘Yutu’ rover reaches the lunar surface.
‘Jade Rabbit’ measures 150 centimeters high and weighs approximately 120 kilograms.
The rover and lander are equipped with multiple cameras, spectrometers, an optical telescope, radar and other sensors to investigate the lunar surface and composition.
One highly anticipated highlight will be when the lander and deployed Jade Rabbit rover image each other on the surface.
The rover is expected to continue operating for at least three months.
The Chang’e 3 landing mission marks the beginning of the second phase of China’s lunar robotic exploration program.
It follows a pair of highly successful lunar orbiters named Chang’e 1 and 2 which launched in 2007 and 2010.
The next step will be an unmanned lunar sample return mission, perhaps around 2020.
China’s Chang’e 3 probe joins NASA’s newly arrived LADEE lunar probe which entered lunar orbit on Oct. 6 following a spectacular night time blastoff from NASA’s Wallops Flight Facility in Virginia.
Stay tuned here for continuing SpaceX, MAVEN and MOM news and Ken’s SpaceX and MAVEN launch reports from on site at Cape Canaveral & the Kennedy Space Center press site.
India’s First Mars Probe ‘MOM’ Blasts Free of Earth Joining MAVEN in Race to Red Planet
CAPE CANAVERAL, FL – India’s first ever Mars probe ‘MOM’ successfully fired its main engine today (Dec. 1), blasting the craft free of the Earth’s sphere of influence forever to begin her nearly yearlong momentous voyage to the Red Planet.
Indian space engineers initiated the 440 Newton liquid fueled engine firing precisely as planned at 00:49 hrs (IST) on Sunday, Dec. 1, 2013 during a critical nail-biting burn lasting some 22 minutes.
The Trans Mars Insertion (TMI) firing propelled India’s Mars Orbiter Mission (MOM) away from Earth forever and placed the spacecraft on course for a rendezvous with the Red Planet on September 24, 2014 – where it will study the atmosphere and sniff for signals of methane.
Sunday’s Mars insertion burn imparted the vehicle with an incremental velocity of 647.96 meters per second (m/sec) consuming 198 kg of fuel.
The maneuver dubbed ‘The mother of all slingshots’, enabled MOM to finally achieve escape velocity and catapulted the 1,350 kilogram (2,980 pound) spacecraft on an historic flight streaking towards Mars.
And in a rare but rather delightful coincidence, MOM is not alone on her remarkable Martian sojourn. Following the triumphant engine burn, she now joins NASA’s MAVEN orbiter in a gallant marathon race to the Red Planet.
MOM was designed and developed by the Indian Space Research Organization’s (ISRO) at a cost of $69 Million and marks India’s inaugural foray into interplanetary flight.
“The Earth orbiting phase of the spacecraft ended,” with this maneuver said ISRO.
MOM is healthy and all systems are functioning normally.
While MOM was cycling Earth, ISRO scientists and engineers activated and tested the probes systems and science payloads.
They also turned the crafts color camera homewards to capture the “First ever image of Earth Taken by Mars Color Camera,” according to ISRO.
MOM is nicknamed ‘Mangalyaan’ – which in Hindi means ‘Mars craft.’
MOM’s journey bagen with a picture perfect Nov. 5 liftoff atop India’s highly reliable four stage Polar Satellite Launch Vehicle (PSLV) C25 from ISRO’s Satish Dhawan Space Centre SHAR, Sriharikota.
The PSLV booster precisely injected MOM into an initial elliptical Earth parking orbit of 247 x 23556 kilometers with an inclination of 19.2 degrees.
PSLV does not have sufficient thrust to send MOM streaking directly to the Red Planet.
Therefore since the flawless launch, the engine has been fired 6 times on November 7, 8, 9, 11, and 16 plus one supplementary maneuver to gradually raise the spacecrafts apogee from 23556 km to 192,874 km.
The most recent orbit raising maneuver occurred on Nov 16, 2013 with a burn time of 243.5 seconds and increased the apogee from 118,642 km to 192,874 km.
Today’s burn was the final one around Earth and absolutely crucial for setting her on course for Mars.
MOM was the first of two missions dispatched to Mars by Earthlings this November.
Half a world away, NASA’s MAVEN orbiter blasted off on Nov. 18 from Cape Canaveral Air Force Station, Florida atop an Atlas V booster on a direct path to the Red Planet.
The MOM spacecraft is now on traveling on a heliocentric elliptical trajectory to begin a 300 day long interplanetary voyage of more than 700 Million kilometers (400 Million miles) to the Red Planet.
Along the path to Mars, ISRO plans to conduct a series of Trajectory Correction Maneuvers (TCMs) using MOM’s Attitude and Orbit Control System (AOCS) thrusters to precisely navigate the probe to the point required to achieve orbit around the Red Planet
Following the ten month cruise through space the orbital insertion engine will fire for a do or die burn on September 24, 2014 placing MOM into an 377 km x 80,000 km elliptical orbit around Mars.
MOM will reach Mars vicinity just two days after MAVEN’s arrival on Sept. 22, 2014.
If all continues to goes well, India will join an elite club of only four who have launched probes that successfully investigated the Red Planet from orbit or the surface – following the Soviet Union, the United States and the European Space Agency (ESA).
Both MAVEN and MOM’s goal is to study the Martian atmosphere, unlock the mysteries of its current atmosphere and determine how, why and when the atmosphere and liquid water was lost – and how this transformed Mars climate into its cold, desiccated state of today.
Although MOM’s main objective is a demonstration of technological capabilities, the probe is equipped with five indigenous instruments to conduct meaningful science – including a multi color imager and a methane gas sniffer to study the Red Planet’s atmosphere, morphology, mineralogy and surface features. Methane on Earth originates from both geological and biological sources – and could be a potential marker for the existence of Martian microbes.
MOM’s 15 kg (33 lb) science suite comprises:
MCM: the tri color Mars Color Camera images the planet and its two tiny moons, Phobos and Deimos
LAP: the Lyman Alpha Photometer measures the abundance of hydrogen and deuterium to understand the planets water loss process
TIS: the Thermal Imaging Spectrometer will map surface composition and mineralogy
MENCA: the Mars Exospheric Neutral Composition Analyser is a quadrapole mass spectrometer to analyze atmospheric composition
MSM: the Methane Sensor for Mars measures traces of potential atmospheric methane down to the ppm level.
Scientists will be paying close attention to whether MOM detects any atmospheric methane to compare with measurements from NASA’s Curiosity rover – which found ground level methane to be essentially nonexistent – and Europe’s upcoming 2016 ExoMars Trace Gas Orbiter.
India’s MOM – ‘Mangalyaan’ mission is expected to continue gathering measurements at the Red Planet for at least six months and hopefully much longer.
MAVEN could operate for a decade or longer and is also crucial for relaying images and data collected by NASA’s current and upcoming surface rovers and landers.
Although they were developed independently and have different suites of scientific instruments, the MAVEN and MOM science teams will “work together” to unlock the secrets of Mars atmosphere and climate history, MAVEN’s top scientist told Universe Today.
“We have had some discussions with their science team, and there are some overlapping objectives,” Bruce Jakosky told me. Jakosky is MAVEN’s principal Investigator from the University of Colorado at Boulder.
“At the point where we [MAVEN and MOM] are both in orbit collecting data we do plan to collaborate and work together with the data jointly,” Jakosky said.
Stay tuned here for continuing MOM and MAVEN news and Ken’s MAVEN and SpaceX Falcon 9 launch reports from on site at the Kennedy Space Center press center and Cape Canaveral Air Force Station, Florida.
Mother of All Slingshots Set to Hurl India’s MOM Probe to Mars
CAPE CANAVERAL, FL – MOM – India’s first ever interplanetary spacecraft – is spending her last day around Mother Earth.
The clock is ticking down relentlessly towards “The mother of all slingshots” – the critical engine firing intended to hurl India’ Mars Orbiter Mission (MOM) probe on her ten month long interplanetary cruise to the Red Planet.
Engineers at the Indian Space Research Organization’s (ISRO) Mission Operations Complex at Bangalore are now just hours away from sending the commands that will ignite MOMs’ liquid fueled main engine for TMI – the Trans Mars Insertion maneuver that will propel MOM away from Earth forever and place the craft on an elliptical trajectory to the Red Planet.
“Performance assessment of all subsystems of the spacecraft has been completed,” reports ISRO.
The do or die 1351 second burn is slated to begin at 00:49 hrs IST tonight – on Dec. 1 Indian local time.
The 440 Newton liquid fueled main engine must fire precisely as planned to inject MOM on target to Mars.
MOM’s picture perfect Nov. 5 liftoff atop India’s highly reliable four stage Polar Satellite Launch Vehicle (PSLV) C25 from the ISRO’s Satish Dhawan Space Centre SHAR, Sriharikota, precisely injected the spacecraft into an initial elliptical Earth parking orbit of 247 x 23556 kilometers with an inclination of 19.2 degrees.
Since then the engine has fired 6 times to gradually raise the spacecrafts apogee.
The most recent orbit raising maneuver occurred at 01:27 hrs (IST) on Nov 16, 2013 with a burn time of 243.5 seconds increased the apogee from 118,642 km to 192,874 km.
Tonight burn is MOM’s final one around Earth and absolutely crucial for setting her on course for Mars.
If all goes well the $69 million MOM spacecraft reaches the vicinity of Mars on 24 September 2014.
MOM was the first of two Earth missions to Mars launched this November.
NASA’s $671 Million MAVEN orbiter launched as scheduled on Nov. 18, from Cape Canaveral, Florida and arrives at Mars on Sept. 22, 2014, about two days before MOM.
Both MAVEN and MOM’s goal is to study the Martian atmosphere, unlock the mysteries of its current atmosphere and determine how, why and when the atmosphere and liquid water was lost – and how this transformed Mars climate into its cold, desiccated state of today.
Stay tuned here for continuing MOM and MAVEN news and Ken’s MAVEN and SpaceX Falcon 9 launch reports from on site at the Kennedy Space Center press center and Cape Canaveral Air Force Station, Florida.
ISON Appears To Be Fading, But Astronomers Keeping Eyes Peeled
A brief morning update (EST) from Karl Battams, who studies sungrazing comets at the Naval Research Laboratory, confirms social media reports that Comet C/2012 S1 ISON appears to be getting fainter in images from the Solar and Heliospheric Observatory (SOHO). (To compare, you can see older images below the jump.)
“Comet #ISON really is fading fast and I no longer see any sign of a “central condensation” (i.e. no obvious indication of a nucleus…),” Battams wrote on Twitter. “I *do* think that something emerged from the Sun, but probably a v.small nucleus or “rubble pile”, and I fear that may have now dissolved.”
This comet, however, has defied predictions over and over again. We’ll keep you posted as to its progress.
Astronomers wrote off Comet ISON on Thursday (Nov. 28) shortly after it rounded the sun, but it brightened considerably afterwards and researchers said it’s possible a small nucleus did survive the close encounter. Battams previously noted ISON’s behavior is much different than the other 2,000 or so sungrazers he’s observed.
The comet was discovered Sept. 21, 2012 by Artyom Novichonok and Vitali Nevski while conducting the International Scientific Optical Network (ISON) survey and has been the subject of intense speculation about its brightness prospects since.
Zombie ISON ‘Behaving Like A Comet’, Stunned Astronomers Say
Talk about the Comeback Kid. After Comet C/2012 S1 ISON rounded the sun yesterday afternoon, professional astronomers around the world looked at the faded debris and concluded it was an “ex-comet.” NASA wrapped up an hours-long Google+ Hangout with that news. The European Space Agency declared it was dead on Twitter.
But the remnants — or whatever ISON is now — kept brightening and brightening and brightening in images from the NASA/European Space Agency Solar and Heliospheric Observatory. The pictures are still puzzling astronomers right now, almost a day after ISON’s closest encounter with the sun.
You can follow our liveblogged confusion yesterday, capped by a gobsmacking announcement from the Naval Research Laboratory’s Karl Battams, “We believe some small part of ISON’s nucleus has SURVIVED perihelion,” he said on Twitter. Since then, Battams wrote a detailed blog post, referring to images from the Large Angle and Spectrometric Coronagraph (LASCO) aboard SOHO:
“Matthew [Knight] and I are ripping our hair out right now as we know that so many people in the public, the media and in science teams want to know what’s happened. We’d love to know that too! Right now, here’s our working hypothesis: As comet ISON plunged towards to the Sun, it began to fall apart, losing not giant fragments but at least a lot of reasonably sized chunks. There’s evidence of very large dust in the form of that long thin tail we saw in the LASCO C2 images.
Then, as ISON plunged through the corona, it continued to fall apart and vaporize, and lost its coma and tail completely just like Lovejoy did in 2011. (We have our theories as to why it didn’t show up in the SDO images but that’s not our story to tell – the SDO team will do that.) Then, what emerged from the Sun was a small but perhaps somewhat coherent nucleus, that has resumed emitting dust and gas for at least the time being. In essence, the tail is growing back, as Lovejoy’s did.
So while our theory certainly has holes, right now it does appear that a least some small fraction of ISON has remained in one piece and is actively releasing material. We have no idea how big this nucleus is, if there is indeed one. If there is a nucleus, it is still too soon to tell how long it will survive. If it does survive for more than a few days, it is too soon to tell if the comet will be visible in the night sky. If it is visible in the night sky, it is too soon to say how bright it will be…
This morning (EST), Battams succinctly summarized the latest images he saw: “Based on a few more hours of data, comet #ISON appears to be… well, behaving like a comet!”, he wrote on Twitter.
NASA issued a status update this morning saying it’s unclear if this leftover is debris or an actual nucleus, but added that “late-night analysis from scientists with NASA’s Comet ISON Observing Campaign suggest that there is at least a small nucleus intact.” NASA, as well as Battams, pointed out that comet has behaved unpredictably throughout the 15 months scientists and amateurs have been observing it.
Throughout the year that researchers have watched Comet ISON – and especially during its final approach to the sun – the comet brightened and dimmed in unexpected ways. Such brightness changes usually occur in response to material boiling off the comet, and different material will do so at different temperatures thus providing clues as to what the comet is made of. Analyzing this pattern will help scientists understand the composition of ISON, which contains material assembled during the very formation of the solar system some 4.5 billion years ago.
Slate Bad Astronomy blogger Phil Plait jokingly threw out phrases like “What the what?” on Twitter yesterday, but added in a late-night update: “If you haven’t figured this out yet: We are *loving* this. The Universe surprises us yet again! How awesome!” He continued with his astonishment in a blog post:
For those keeping score at home, it got bright, then it faded, then it got all smeared out, then it came around the Sun smeared out, and then it seemed to get its act together again. At this point, I refuse to make any further conclusions about this comet; it seems eager to confuse. I’ve been hearing from comet specialists who are just as baffled… which is fantastic! If we knew what was going on, there’d be nothing more to learn.
In a series of Twitter posts this morning, the European Space Agency’s science feed offered this take from Gerhard Schwehm, ESA’s head of planetary science:
From my initial look at ISON in today’s SOHO images, it seems nucleus has mostly disintegrated. Will only know if part of ISON nucleus has survived by continuing observations and performing more analysis. Bright fan-shape implies lots of material was released and travelling along ISON orbit, not confined in a traditional tail. Would be interesting to learn more about composition of debris to help us piece together what’s happened, but we need more time.
Other spacecraft searching for ISON were not able to spot it. For ESA’s PROBA-2, it may have been because of its composition or proximity to the sun, but scientists are unsure. It was also invisible in NASA’s Solar Dynamics Observatory; “scientists are still looking at the data to figure out why,” an agency Twitter update stated this morning.
So to sum up: no one’s quite sure of what is happening now, or what is happening next, but we will keep you posted and let you know if and when you can see ISON again in your home telescopes.
Chinese ‘Jade Rabbit’ Rover Aims For The Moon On Sunday
If all goes well, expect another moon robot very soon. The Yutu (“Jade Rabbit”) rover will lift off from China as a part of the Chang’e-3 mission — target launch date Sunday (Nov. 29) — to explore the moon’s Sea of Rainbows after its scheduled landing two weeks later, Dec. 14.
There are other spacecraft orbiting the moon — including the newly launched LADEE from NASA, which is checking out the moon’s tenuous atmosphere — but if this mission succeeds, it would be the first soft landing since Russia’s Luna-24 in 1976. That’s a 37-year drought.
Recent English information on the mission is scarce, but it’s been widely reported that the mission will include a lander in a six-wheeled rover. This Chinese news agency notes that planners expect to put up an astronomical telescope, test remote control between the moon and the Earth, and explore areas around the landing location. You can also read (dated) background information on the mission on the Chinese National Space Administration’s website.
The European Space Agency (ESA), meanwhile, released a press update describing how people from its organization will help track the mission during its journey to the moon. The Europeans will be helping the Chinese track the mission all the way to the time it is expected to reach the surface. After the mission lands, ESA will use two antennas to perform a measurement intended to figure out — “with extreme accuracy”, the agency says — where the lander is located.
And for those who remember, a fun bit of history from 1969 recalled by the Planetary Society: during Apollo 11, the first manned mission to land on the moon, this ground-to-moon exchange actually happened:
Capcom: Roger. Among the large headlines concerning Apollo this morning, there’s one asking that you watch for a lovely girl with a big rabbit. An ancient legend says a beautiful Chinese girl called Chang-o has been living there for 4,000 years. It seems she was banished to the Moon because she stole the pill of immortality from her husband. You might also look for her companion, a large Chinese rabbit, who is easy to spot since he is always standing on his hind feet in the shade of a cinnamon tree. The name of the rabbit is not reported.
Buzz Aldrin, slated to be second man on the moon: Okay. We’ll keep a close eye out for the bunny girl.
Spacesuit Leak And Fist Pumps: Ride Along With Astronaut’s Eventful Space Station Mission
The big news around astronaut circles these days is the assignment of Takuya Onishi — from the Japanese Aerospace Exploration Agency — to Expedition 48/49 around June 2016. Onishi is from the class of 2009, and we’re guessing he’d be sure to poll his classmates on how their mission training is going.
Well, another of the 2009 astronaut class — Luca Parmitano — just returned from six months in space. It was an eventful mission, with Parmitano facing down a scary water leak during a spacewalk, using the Canadarm to berth and let go of a cargo spacecraft, and then delighting the Internet with enthusiastic fist pumps just minutes after he landed.
Parmitano speaks about the science on station (up to 150 experiments at one time!) as well as what he was experiencing during the leak:
“We were starting our third task, and I felt some water on the back of my head,” he said in an undated video from orbit included in the new video. “And I realized it was cold water. It was not a normal feeling. So I called ground, and that point we called to terminate the EVA.”
But he made it back safely, and looks more than ready to take on another mission in this picture. The cause of the leak is still under investigation, and NASA is holding off on more spacewalks with American suits until they figure out what happened.
Parmitano’s mission also featured a unique collaboration with teenager Abby Harrison, who broadcasted her own question-and-answer sessions with him for the astronaut to reach a younger audience.