When we look at the night sky, filled with stars, it’s hard to resist counting. Just with the unaided eye, in dark skies, you can see a few thousand.
How many stars are there in the entire Universe? Before we get to that massive number, let’s consider what you can count with the tools available to you.
Perfect vision in dark skies allows us to see stars down to about magnitude 6. But to really make an accurate census of the total number of stars, you’d need to travel to both the Northern and Southern Hemispheres, since only part of the sky is visible from each portion of the Earth. Furthermore, you’d need to make your count over several months, since a portion of the sky is obscured by the Sun. If you had perfect eyesight and traveled to completely dark skies in both the Northern and Southern Hemispheres, and there was no Moon, you might be able to get to count up almost 9,000 stars.
With a good pair of binoculars, that number jumps to about 200,000, since you can observe stars down to magnitude 9. A small telescope, capable of resolving magnitude 13 stars will let you count up to 15 million stars. Large observatories could resolve billions of stars.
But how many stars are out there? How many stars are there in the Milky Way?
According to astronomers, our Milky Way is an average-sized barred spiral galaxy measuring up to 120,000 light-years across. Our Sun is located about 27,000 light-years from the galactic core in the Orion arm. Astronomers estimate that the Milky Way contains up to 400 billion stars of various sizes and brightness.
A few are supergiants, like Betelgeuse or Rigel. Many more are average-sized stars like our Sun. The vast majority of stars in the Milky Way are red dwarf stars; dim, low mass, with a fraction of the brightness of our Sun.
As we peer through our telescopes, we can see fuzzy patches in the sky which astronomers now know are other galaxies like our Milky Way. These massive structures can contain more or less stars than our own Milky Way.
There are spiral galaxies out there with more than a trillion stars, and giant elliptical galaxies with 100 trillion stars.
And there are tiny dwarf galaxies with a fraction of our number of stars.
So how many galaxies are there?
According to astronomers, there are probably more than 170 billion galaxies in the observable Universe, stretching out into a region of space 13.8 billion light-years away from us in all directions.
And so, if you multiply the number of stars in our galaxy by the number of galaxies in the Universe, you get approximately 1024 stars. That’s a 1 followed by twenty-four zeros.
That’s a septillion stars.
But there could be more than that.
It’s been calculated that the observable Universe is a bubble of space 47 billion years in all directions.
It defines the amount of the Universe that we can see, because that’s how long light has taken to reach us since the Big Bang.
This is a minimum value, the Universe could be much bigger – it’s just that we can’t ever detect those stars because they’re outside the observable Universe. It’s even possible that the Universe is infinite, stretching on forever, with an infinite amount of stars. So add a couple more zeros. Maybe an infinite number of zeroes.
Some cultures used to say the Earth was the center of the Universe. But in a series of “great demotions,” as astronomer Carl Sagan put it in his book Pale Blue Dot, we found out that we are quite far from the center of anything. The Sun holds the prominent center position in the center of the Solar System, but our star is just average-sized, located in a pedestrian starry suburb — a smaller galactic arm, far from the center of the Milky Way Galaxy.
But perhaps our suburb isn’t as quiet or lowly as we thought. A new model examining the Milky Way’s structure says our “Local Arm” of stars is more prominent than we believed.
“We’ve found there is not a lot of difference between our Local Arm and the other prominent arms of the Milky Way, which is in contrast what astronomers thought before,” said researcher Alberto Sanna, of the Max-Planck Institute for Radio Astronomy, speaking today at the American Astronomical Society’s annual meeting in Indianapolis, Indiana.
Sanna said that one of the main questions in astronomy is how the Milky Way would appear to an observer outside our galaxy.
If you imagine the Milky Way as a rippled cookie, our star is in a neighborhood in between two big ripples (the Sagittarius Arm and the Perseus Arm). Before, we thought the Local Arm (or Orion Arm) was just a small spur between the arms. New research using trigonometric parallax measurements, however, suggests the Local Arm could be a “significant branch” of one of those two arms.
In a few words, our stellar neighborhood is a bigger and brighter one than we thought it was.
As part of the BeSSeL Survey (Bar and Spiral Structure Legacy Survey) using the Very Long Baseline Array (VLBA), astronomers are able to make more precise measurements of cosmic distances. The VLBA uses a network of 10 telescopes that work together to figure out how far away stars and other objects are.
It’s hard to figure out the distance from the Earth to other stars. Generally, astronomers use a technique called parallax, which measures how much a star moves when we look at it from the Earth.
When our planet is at opposite sites of its orbit — in spring and fall, for example — the apparent location of stellar objects changes slightly.
The more precisely we can measure this change, the better a sense we have of a star’s distance.
The VLBA undertook a search for spots in our galaxy where water and methanol molecules (also known as masers) enhance radio waves — similar to how lasers strengthen light waves. Masers are like stellar lighthouses for radio telescopes, the National Radio Astronomy Observatory stated.
Between 2008 and 2012, the VLBA tracked the distances to (and movements of) several masers to higher precision than previously, leading to the new findings.
Will the findings help ease our “inferiority complex” after all those great demotions?
“I would say yes, that’s a nice conclusion to say we are more important,” Sanna told Universe Today. “But more importantly, we are now mapping the Milky Way and discovering how the Milky Might appear to an outside observer. We now know the Local Arm arm is something that an observer from afar would definitely notice!”
This is just a gorgeous shot of our home planet from the International Space Station, shared by astronaut Karen Nyberg via Twitter. While many pictures of Earth from space show a bright view of our planet, this view of the world plunging into darkness provides a unique, not-often-seen view. If a picture can be this beautiful, imagine what must look like in person.
Nyberg is sharing her experiences via Twitter and also — I believe she is the first astronaut sharing on Pinterest. She describes herself as “Aspiring quilter, crafter, artist” (perfect for the Pinterest crowd) in addition to being an astronaut by day, and said she hopes to do some crafting in space if she has any spare time. Nyberg has a special board for “Hair in Space” (which includes both bald pates and gravity defying hair,) hoping to inspire the younger generation of women to get interested in space exploration. “When girls see pictures of ponytails, don’t you think it stirs something inside them that says, that could be ME up there!” Nyberg writes.
An unexpected arrival of a surprisingly strong (6 KP) geomagnetic storm from the Sun provided an amazing weekend for astrophotographers. Stargazers from both hemispheres were treated with seeing the aurora. We already posted the images from Mike Hollingshead seeing the aurora and red sprite lightning in Iowa, but here are some more great views, including this gorgeous shot of the aurora over Crater Lake in Oregon, from astrophotographer Brad Goldpaint, with the added intrigue of the International Space Station flying over at 2:35 am, local time. He’s also provided an amazing video, too, below.
“I drove to Crater Lake National Park last night to photograph the Milky Way rising above the rim,” Goldpaint said via email to Universe Today. “I’ve waited months for the roads to open and spring storms to pass, so I could spend a solitude night with the stars. Near 11pm, I was staring upward towards a clear night sky when suddenly, without much warning, an unmistakable faint glow of the aurora borealis began erupting in front of me. I quickly packed up my gear, hiked down to my truck, and sped to a north facing location. With adrenaline pumping, I raced to the edge of the caldera, set up a time-lapse sequence, and watched northern lights dance until sunrise. The moon rose around 2am and blanketed the surrounding landscape with a faint glow, adding depth and texture to the shot.”
This video from Loic Le Guilly shows the aurora australis (southern lights) and the glow of the Milky Way in the skies over Tasmania he saw at Signal Station, near Hobart, Tasmania:
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
The Moon might seem like a poor place to hunt for water, but in fact there’s a decent amount of the stuff dispersed throughout the lunar soil — and even more of it existing as ice deposits in the dark recesses of polar craters. While the LCROSS mission crashed a rocket stage into one of these craters in October 2009 and confirmed evidence of water in the resulting plume of debris, there haven’t been any definitive maps made of water deposits across a large area on the Moon — until now.
Over the course of several years, NASA’s Lunar Reconnaissance Orbiter scanned the Moon’s south pole using its Lunar Exploration Neutron Detector (LEND) to measure how much hydrogen is trapped within the lunar soil. Areas exhibiting suppressed neutron activity — shown above in blue — indicate where hydrogen atoms are concentrated most, strongly suggesting the presence of water molecules… aka H2O.
The incredibly-sensitive LEND instrument measures the flux of neutrons from the Moon, which are produced by the continuous cosmic ray bombardment of the lunar surface. Even a fraction of hydrogen as small as 100 ppm can make a measurable change in neutron distribution from the surface of worlds with negligible atmospheres, and the hydrogen content can be related to the presence of water.
No other neutron instrument with LEND’s imaging capability has ever been flown in space.
Watch the video below for more details as to how LRO and LEND obtained these results:
“While previous lunar missions have observed indications of hydrogen at the Moon’s south pole, the LEND measurements for the first time pinpoint where hydrogen, and thus water, is likely to exist.”
What’s so important about finding water on the Moon? Well besides helping answer the question of where water on Earth and within the inner Solar System originated, it could also be used by future lunar exploration missions to produce fuel for rockets, drinking water, and breathable air. Read more here.
“Holy crap, this is the rarest scene I’ve ever captured and likely ever will,” said photographer Mike Hollingshead. “I was standing there just watching when bam, big red sprites ‘squirting’ up into the air in the aurora.”
Mike said was hoping to see the aurora the night of May 31, 2013, and felt lucky when he saw a faint yellow glow begin to rise in the skies. At the same time, a thunderstorm could be seen off on the horizon and almost before he could even ponder the possibility of seeing something unusual, sprites started appearing.
This is an extremely rare event to be captured on film; in fact an image appearing just a few days ago on Astronomy Picture of the Day (APOD) on May 22 showed red sprite lighting with an aurora, and the APOD team said the image was a “candidate for the first color image ever recorded of a sprite and aurora together.”
“Sprites were first imaged in 1989 accidentally and first color photograph in 1994,” wrote Mike on his Extreme Instability website. “Recent. But with auroras, evidently it is possible the very first time was a couple freaking weeks before this one of mine. It’s that crazy rare.”
Sprites are huge electrical discharges that occur high above thunderstorm clouds. They are rare, but at least one has been captured on film from the International Space Station. They are triggered by the discharges of positive lightning between an underlying thundercloud and the ground. They often occur in clusters within the altitude range 50–90 km above the Earth’s surface.
Stunning! Thanks to Mike Hollingshead for sharing his amazing photos, and congratulations on capturing such a rare event!
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
We’ve found hundreds of planets outside the solar system, but taking a picture of one is still something quite special. The light of the parent star tends to greatly overwhelm the faint light of the alien planet. (So usually we learn about planets by tracking the effects each planet has on its star, like dimming light when it passes in front or making the star slightly wobble.)
This picture (above) shows HD95086 b, which astronomers believe is one of only about a dozen exoplanets ever imaged. It’s 300 light-years from Earth. The planet candidate is about four to five times the mass of Jupiter and orbiting a very young star that is probably only 10 million to 17 million years old. That’s a baby compared to our own solar system, estimated at 4.5 billion years old.
We still have a lot to learn about this object (and the observations from the Very Large Telescope will need to be confirmed independently), but so far astronomers say they figure that planet formed in the gas and dust surrounding star HD 95086. But the planet is actually very far away from the star now, about twice the distance as the Sun-Neptune orbital span in our own solar system.
“Its current location raises questions about its formation process,” stated team member Anne-Marie Lagrange, who is with the Grenoble Institute of Planetology and Astrophysics in France.
“It either grew by assembling the rocks that form the solid core and then slowly accumulated gas from the environment to form the heavy atmosphere, or started forming from a gaseous clump that arose from gravitational instabilities in the disc.
“Interactions between the planet and the disc itself,” she added, “or with other planets may have also moved the planet from where it was born.”
Astronomers estimate the planet candidate has a surface temperature of 1,292 degrees Fahrenheit (700 degrees Celsius), which could allow water vapor or methane to stick around in the atmosphere. It will take more VLT observations to figure this out, though.
The results from this study will be published in Astrophysical Journal Letters. The paper is also available on prepublishing site Arxiv.
New measurements of the energetic space radiation environment present in interplanetary space taken by NASA’s Curiosity rover confirm what has long been suspected – that lengthy years long voyages by astronauts to deep space destinations like Mars will expose the crews to high levels of radiation that – left unchecked – would be harmful to their health and increase their chances of developing fatal cancers.
Although the data confirm what scientists had suspected, it’s equally important to state that the space radiation data are not ‘show stoppers” for human deep space voyages to the Red Planet and other destinations because there are a multitude of counter measures- like increased shielding and more powerful propulsion – that NASA and the world’s space agencies can and must implement to reduce and mitigate the dangerous health effects of radiation on human travelers.
The new radiation data was released at a NASA media briefing on May 30 and published in the journal Science on May 31.
Indeed the new measurements collected by Curiosity’s Radiation Assessment Detector (RAD) instrument during her 253-day, 560-million- kilometer journey enroute to the Red Planet in 2011 and 2012 will provide important insights to allow NASA to start designing systems for safely conducting future human missions to Mars.
“NASA wants to send astronauts to Mars in the 2030’s,” Chris Moore, NASA’s deputy director of Advanced Exploration Systems NASA HQ, said to reporters at the media briefing.
“The Human Spaceflight and Planetary Science Divisions at NASA are working together to get the data needed for human astronauts. RAD is perfect to collect the data for that,” said Moore.
The RAD data indicate that astronauts would be exposed to radiation levels that would exceed the career limit levels set by NASA during a more than year long voyage to Mars and back using current propulsion systems, said Eddie Semones, spaceflight radiation health officer at the Johnson Space Center.
NASA’s Humans to Mars planning follows initiatives outlined by President Obama.
“As this nation strives to reach an asteroid and Mars in our lifetimes, we’re working to solve every puzzle nature poses to keep astronauts safe so they can explore the unknown and return home,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations in Washington, in a statement.
The International Space Station already in low Earth orbit and the Orion crew capsule under development will serve as very useful platforms to conduct real life experiments on resolving the health risks posed by long term exposure to space radiation.
“We learn more about the human body’s ability to adapt to space every day aboard the International Space Station, said Gerstenmaier. “As we build the Orion spacecraft and Space Launch System rocket to carry and shelter us in deep space, we’ll continue to make the advances we need in life sciences to reduce risks for our explorers. Curiosity’s RAD instrument is giving us critical data we need so that we humans, like the rover, can dare mighty things to reach the Red Planet.”
RAD was the first instrument to collect radiation measurements during the cruise phase to the Red Planet. It is mounted on the top deck of the Curiosity rover.
“Although RAD’s objective is to characterize the radiation environment on the surface of Mars, it’s also good for the cruise phase,” Don Hassler, RAD Principal Investigator at the Southwest Research Institute (SWRI) told reporters.
“Since Orion and MSL are similar sized RAD is ideal for collecting the data.”
Hassler explained that RAD measures two types of radiation that pose health risks to astronauts. First, the steady stream of low dose galactic cosmic rays (GCRs), and second the short-term and unpredictable exposures to solar energetic particles (SEPs) arising from solar flares and coronal mass ejections (CME’s).
Radiation exposure is known to increase a person’s risk of suffering fatal cancer.
Exposure is measured in units of Sievert (Sv) or milliSievert (one one-thousandth Sv). Being exposed to a dose of 1 Sievert (Sv) over time results in a five percent increased risk of developing cancer.
NASA’s current regulations limit the potential for increased cancer risk to 3 percent for astronauts currently working on the ISS in low-Earth orbit.
RAD determined that the Curiosity rover was exposed to an average of 1.8 milliSieverts per day during the 8.5 month cruise to Mars, due mostly to Galactic Cosmic Rays, said Cary Zeitlin, SWRI Principal Scientist for MSL,at the briefing. “Solar particles only accounted for about 3 to 5 percent of that.”
During a typical 6 month cruise to Mars the astronaut crews would be exposed to 330 millisieverts. That is more than 3 times the typical 6 month exposure of astronauts aboard the ISS which amounts to about 100 millisieverts. See graphic above.
“The 360 day interplanetary round trip exposure would be 660 millisieverts based on chemical propulsion methods,” Zeitlin told Universe Today. “A 500 day mission would increase that to 900 millisieverts.”
By comparison, the average annual exposure for a typical person in the US from all radiation sources is less than 10 millisieverts.
The Earth’s magnetic field provides partial radiation shielding for the ISS astronauts living in low-Earth orbit.
“In terms of accumulated dose, it’s like getting a whole-body CT scan once every five or six days,” says Zeitlin.
And that round trip dose of 660 millisieverts doesn’t even include the astronauts surface stay on Mars – which would significantly raise the total exposure count. But luckily for the crew the surface radiation is less.
“The radiation environment on the surface of Mars is about half that in deep space since its modified by the atmosphere,” Hassler told Universe Today. “We will publish the surface data in a few months.”
NASA will need to decide whether to reassess the acceptable career limits for astronauts exposure to radiation from galactic cosmic rays and solar particle events during long duration deep space journeys.
Panoramic view of Yellowknife Bay basin back dropped by Mount Sharp shows the location of the first two drill sites – John Klein & Cumberland – targeted by NASA’s Curiosity Mars rover and the RAD radiation detector which took the first deep space measurements of harmful space radiation during the cruise phase to Mars in 2011 and 2012 . Curiosity accomplished historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182) near where the robotic arm is touching the surface. This week the rover scooted about 9 feet to the right to Cumberland (right of center) for 2nd drill campaign on May 19, 2013 (Sol 279). Credit: NASA/JPL-Caltech/Ken Kremer – kenkremer.com/Marco Di Lorenzo
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
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Learn more about Conjunctions, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations
June 4: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8:30 PM
Saturn’s F ring is certainly a curious structure. Orbiting the giant planet 82,000 kilometers above its equatorial cloud tops, the F ring is a ropy, twisted belt of bright ice particles anywhere from 30-500 km wide. It can appear as a solid band or a series of braided cords surrounded by a misty haze, and often exhibits clumps and streamers created by the gravitational influence of embedded moonlets or passing shepherd moons.
In the picture above, acquired by the Cassini spacecraft on Feb. 13, 2013 and released on May 27, we see a section of the F ring separated into long ropes and spanned by connecting bands of bright material — the “ladder” structure suggested in the title.
Scientists believe that interactions between the F ring and the moons Prometheus and Pandora cause the dynamic structure of the F ring. (Watch an animation of the F ring and shepherd moons here.)
Made of particles of water ice finer than cigarette smoke, the F ring orbits Saturn beyond the outer edge of the A ring across the expanse of the 2,600-km-wide Roche Division. In these images, Saturn and the main ring systems are off frame to the left.
This view looks toward the unilluminated side of the rings from about 32 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft’s narrow-angle camera (NAC).
The view was obtained at a distance of approximately 426,000 miles (686,000 kilometers) from Saturn and at a phase angle of 162 degrees. Image scale is 2 miles (4 kilometers) per pixel.
The next time that American astronauts launch to space from American soil it will surely be aboard one of the new commercially built “space taxis” currently under development by a trio of American aerospace firms – Boeing, SpaceX and Sierra Nevada Corp – enabled by seed money from NASA’s Commercial Crew Program (CCP).
Boeing has moved considerably closer towards regaining America’s lost capability to launch humans to space when the firm’s privately built CST-100 crew capsule achieved two key new milestones on the path to blastoff from Florida’s Space Coast.
The CST-100 capsule is designed to carry a crew of up to 7 astronauts on missions to low-Earth orbit (LEO) and the International Space Station (ISS) around the middle of this decade.
Boeing’s crew transporter will fly to space atop the venerable Atlas V rocket built by United Launch Alliance (ULA) from Launch Complex 41 on Cape Canaveral Air Force Station in Florida.
The Boeing and ULA teams recently completed the first wind tunnel tests of a 7 percent scale model of the integrated capsule and Atlas V rocket (photo above) as well as thrust tests of the modified Centaur upper stage.
The work is being done under the auspices of NASA’s Commercial Crew Integrated Capability (CCiCap) initiative, intended to make commercial human spaceflight services available for both US government and commercial customers, such as the proposed Bigelow Aerospace mini space station.
Since its maiden liftoff in 2002, the ULA Atlas V rocket has flawlessly launched numerous multi-billion dollar NASA planetary science missions like the CuriosityMars rover, Juno Jupiter orbiter and New Horizons mission to Pluto as well as a plethora of top secret Air Force spy satellites.
But the two stage Atlas V has never before been used to launch humans to space – therefore necessitating rigorous testing and upgrades to qualify the entire vehicle and both stages to meet stringent human rating requirements.
“The Centaur has a long and storied past of launching the agency’s most successful spacecraft to other worlds,” said Ed Mango, NASA’s CCP manager at the agency’s Kennedy Space Center in Florida. “Because it has never been used for human spaceflight before, these tests are critical to ensuring a smooth and safe performance for the crew members who will be riding atop the human-rated Atlas V.”
The combined scale model CST-100 capsule and complete Atlas V rocket were evaluated for two months of testing this spring inside an 11- foot diameter transonic wind tunnel at NASA’s Ames Research Center in Moffett Field, Calif.
“The CST-100 and Atlas V, connected with the launch vehicle adaptor, performed exactly as expected and confirmed our expectations of how they will perform together in flight,” said John Mulholland, Boeing vice president and program manager for Commercial Programs.
Testing of the Centaur stage centered on characterizing the flow of liquid oxygen from the oxygen tank through the liquid oxygen-feed duct line into the pair of RL-10 engines where the propellant is mixed with liquid hydrogen and burned to create thrust to propel the CST-100 into orbit.
Boeing is aiming for an initial three day manned orbital test flight of the CST-100 during 2016, says Mulholland.
But that date is dependent on funding from NASA and could easily be delayed by the ongoing sequester which has slashed NASA’s and all Federal budgets.
Chris Ferguson, the commander of the final shuttle flight (STS-135) by Atlantis, is leading Boeing’s flight test effort.
Boeing has leased one of NASA’s Orbiter Processing Facility hangers (OPF-3) at the Kennedy Space Center (KSC) for the manufacturing and assembly of its CST-100 spacecraft.
Mulholland told me previously that Boeing will ‘cut metal’ soon. “Our first piece of flight design hardware will be delivered to KSC and OPF-3 around mid 2013.”
NASA’s CCP program is fostering the development of the CST-100 as well as the SpaceX Dragon and Sierra Nevada Dream Chaser to replace the crew capability of NASA’s space shuttle orbiters.
The Atlas V will also serve as the launcher for the Sierra Nevada Dream Chaser space taxi.
Since the forced retirement of NASA’s shuttle fleet in 2011, US and partner astronauts have been 100% reliant on the Russians to hitch a ride to the ISS aboard the Soyuz capsules – at a price tag exceeding $60 Million per seat.
Simultaneously on a parallel track NASA is developing the Orion crew capsule and SLS heavy lift booster to send humans to the Moon and deep space destinations including Asteroids and Mars.
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
…………….
Learn more about Conjunctions, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations:
June 4: “Send your Name to Mars” and “CIBER Astro Sat, LADEE Lunar & Antares ISS Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8:30 PM