Posted on by David Dickinson

How to Spot the Antares Launch from NASA Wallops on Wednesday

Sighting prospects for the US Eastern Seaboard during the ascent of Antares. (Credit: The Orbital Sciences Corporation).

A space launch marking a new era is departing from the Virginia coast this Wednesday evening, and if you live anywhere along a wide area of the US Eastern seaboard, you’ll have a great opportunity to witness the launch with your own eyes. Here’s all the information you’ll need to see it, plus some tips for capturing it with your camera.

Orbital Sciences’ Antares rocket will launch from Pad 0A at NASA’s Mid-Atlantic Regional Spaceport based on Wallops Island, Virginia. This will mark not only the first launch of Antares, but the first orbital launch of a liquid-fueled rocket from Wallops. The launch window runs from 5:00 to 8:00 PM EDT (21:00-24:00 UT).

There were some concerns when a technical anomaly shutdown a “Wet Dress Rehearsal” test this weekend at T-16 minutes, but Orbital Sciences has stated that the problems have been resolved and the launch is pressing ahead as planned.

Space shots are a familiar sight to the residents of the Florida Space Coast, but will provide a unique show for residents of the U.S. central Atlantic region. The launch of Antares from Wallops will be visible for hundreds of miles and be over 10° above the horizon for an arc spanning from Wilmington, North Carolina to Washington D.C. and north to the New York City tri-state area as it heads off to the southeast. Antares is a two stage rocket with a 1st stage liquid fueled engine and a solid-fueled 2nd stage. The primary mission for Wednesday’s Antares A-One flight will be to demonstrate the ability for the Antares rocket to place a payload into orbit. If all goes well, Orbital Sciences will join SpaceX this summer in the select club of private companies with the ability provide cargo delivery access to the International Space Station in Low Earth Orbit.

Antares heads to orbit. Artist's concept. (Credit: Orbital Sciences Corperation).
Antares heads to orbit. Artist’s concept. (Credit: Orbital Sciences Corporation).

Antares will deploy a dummy mass simulating the Cygnus module. Also onboard are the Phonesat-1a, -1b, and -1c micro-cubesats and the Dove 1 satellite.

Be sure to watch for the launch of Antares if you live in the region. Find a spot with a low uncluttered eastern horizon and watch from an elevated rooftop or hilltop location if possible. I live a hundred miles west of Cape Canaveral and I’ve followed launches all the way through Main Engine Cutoff and first stage separation with binoculars.

Be sure to also follow the launch broadcast live for any last minute delays via NASA TV or Universe Today will have a live feed as well. Antares is aiming to put the Cygnus test mass in a 250 x 300 kilometre orbit with a 51.6° inclination. This is similar to what will be necessary to head to the ISS, but this week’s launch will not be trailing the ISS in its path. This also means that the launch window can be extended over three hours rather than having to be instantaneous.

If the launch goes at the beginning of the window, the local sun angle over the launch facility will be 30° to the west. Sunset at Wallops on the evening of April 17th occurs at 7:41PM EDT, meaning we could be in for a photogenic dusk launch of Antares if it stretches to the end of the target window.

And speaking of which, a pre-sunset launch means short daytime exposure settings for photography. Be prepared to switch over for dusk conditions if the launch extends into the end of the window. Conditions during twilight can change almost moment-to-moment. One of the most memorable launches we witnessed was the pre-dawn liftoff of STS-131 on April 5th, 2010:

The predawn launch of STS-131 as seen from 100 miles west. (Photo by author).
The predawn launch of STS-131 as seen from 100 miles west. (Photo by author).

Once in orbit, the launch of Antares should generate four visible objects; the test mass payload, the two clam-shell fairings, and the stage two booster. This configuration is similar to a Falcon 9/Dragon launch, minus the solar panel covers. These objects should be visible to the naked eye at magnitudes +3 to +5. The cubesat payloads are tiny and below the threshold of naked eye visibility.

Preliminary visibility for the objects will favor latitudes 0-30° north at dusk to 10-40° at dawn. Keep in mind these predictions could change as the launch window evolves. The next NORAD tracking ID in the queue is 2013-015A. Yesterday’s launch of Anik G1 from Baikonur was just cataloged today as 2013-014A plus associated hardware. The weather is forecast to be 45% “go” for tomorrow’s launch. In the event of a scrub, the next launch window for Antares is April 18-21st.

First orbit of the Cygnus test mass; shadow orientation of the Earth assumes a nominal launch at 22:00UT on April 17th. (Created by the author using Orbitron. TLEs courtesy of (name)
First orbit of the Cygnus test mass; shadow orientation of the Earth assumes a nominal launch at 22:00 UT on April 17th. (Created by the author using Orbitron. Two-Line Elements courtesy of Henry Hallam).

It’ll be exciting to follow this first flight of Antares and its first scheduled mission to the International Space Station this summer. Also watch for the first ever lunar mission to depart Wallops on August 12 with the launch of the Lunar Atmosphere and Dust Environment Explorer (LADEE).

Finally, if you’ve got a pass of the International Space Station this week, keep an eye out for Progress M-17M currently about 10 minutes ahead of the station in its orbit. The unmanned Progress vehicle just undocked yesterday from the station and will be conducting a series of experiments monitoring the interactions of its thrusters with the ionosphere before burning up on reentry over the South Pacific on April 21st.

A pass of the ISS over UK tonite (April 16th) with Progress leading at 20:30UT. (Created by the author in Orbitron).
A pass of the ISS over UK tonite (April 16th) with Progress leading at 20:30UT. (Created by the author in Orbitron).

The ISS and more can be tracked using Heavens-Above. Also, we’ll be tweeting all of the updates and orbital action as it evolves as @Astroguyz. Let us know of those launch sightings both near and far. It’ll be interesting to see what, if any, impact launches visible to a large portion of the U.S. population will have on the public’s perception of spaceflight. Be sure to look up tomorrow night!

Posted on by Nancy Atkinson

ATV-4 Albert Einstein Says ‘Fill ‘er Up!’

Europe's ATV 4 Albert Einstein prepares for its cargo-carrying mission to the International Space Station. Credit: ESA

The next European cargo mission to the International Space Station is preparing for launch, and in this new image, a fuelling operator at Europe’s Spaceport in French Guiana inspects the ATV-4 Albert Einstein as it is filled with propellant. Launch is currently scheduled for June 5, 2013 on an Ariane 5ES rocket to bring about 7 tons of cargo the ISS, including fuel to give the space station an orbital re-boost.


These Automated Transfer Vehicles (ATVs) bring other supplies such as equipment, experiments, water, air, nitrogen, oxygen and fuel.

As the ISS circles Earth, it slowly loses altitude, and occasionally needs a boost to keep it in the proper orbit. ATVs, Progress resupply ships and the thrusters on the Zvezda service module are used to re-boost the station; Soyuz spacecraft are also used “in a pinch” said Johnson Space Center News Chief Kelly Humphries, but they mainly want to save the Soyuz fuel for the departing crew heading back to Earth.

Watch this video as astronaut Jeff Williams demonstrates the acceleration experienced inside the cabin during a reboost on January 24, 2010 (the acceleration starts about 3:50 in the video):

Posted on by Nancy Atkinson

Beautiful Astrophoto: The Moon and the Milky Way Arch

A 21-image mosaic showing the Milky Way and the setting Moon at dawn, at the Convent of Orada in Monsaraz, Portugal, in the Alqueva´s Dark Sky Reserve. Credit and copyright: Miguel Claro.

With the arrival of spring, the Milky Way begins its rise in the sky in the northern hemisphere. Now visible at dawn in the skies over Portugal at dawn, astrophotographer Miguel Claro captured this stunning 21-image mosaic showing the arch of the Milky Way framing the setting Moon from Monsaraz, Portugal in the Alqueva Dark Sky Reserve. In the foreground is the Convent of Orada (dated 1670).

“Near the center at the right of palm trees, the moon shines brightly, although not interfering with the giant arc of the Milky Way where it is possible to distinguish a lot of constellations like Ursa Minor, with the Polaris star to the left of the image,” Claro said via email, “until the swan (Cygnus), with its North America nebula (NGC7000) clearly visible, down to the right, we still find the constellation of Sagittarius and Scorpio, with the brilliant super giant star, Antares.”

Click the images to see larger versions (yes, you really want to ’embiggen!’)

See an annotated version below. Claro used a Canon 60Da – ISO1600 Lens 24mm f/2; Exp. 15 seconds, taken on 06/04/2013 at 5:32 AM local time.


An annotated version of a 21-image mosaic showing the Milky Way and the setting Moon at dawn, at the Convent of Orada in Monsaraz, Portugal, in the Alqueva´s Dark Sky Reserve. Credit and copyright: Miguel Claro.
An annotated version of a 21-image mosaic showing the Milky Way and the setting Moon at dawn, at the Convent of Orada in Monsaraz, Portugal, in the Alqueva´s Dark Sky Reserve. Credit and copyright: Miguel Claro.

Posted on by Nancy Atkinson

The Exoplanet Naming Debate Heats Up

An artist's impression of an extra solar planet Photo credit: David A Hardy, astroart.org Copyright: STFC.

Following last Friday’s press release from the International Astronomical Union (IAU) concerning the naming of extrasolar planets, a heated debate has arisen over two separate but related issues. One is the “official” vs. “popular” names of astronomical objects (and the IAU’s jurisdiction over them) and the other is Uwingu’s intentions in their exoplanet naming contests.

We’re going to talk about the latter first, as this seems to be where much of the contention lies.

As has been reflected in our articles, Universe Today feels that Uwingu has always been upfront that the names chosen in their exoplanet naming contests were never meant to be “officially” recognized by the IAU, but instead are a way to engage the public and to create non-governmental funding for space research. As we said in our article on Nov. 7, 2012 about the first contest that creates a “baby book” of exoplanet names:

The names won’t be officially approved by the International Astronomical Union, but (Alan) Stern said they will be are similar to the names given to features on Mars by the mission science teams (such as the “Jake Matijevic” rock recently analyzed by the Curiosity rover) that everyone ends up using. This also solves the problem of how to come up with names, a task that the IAU has yet to discuss.

Please read these articles on Time and New Scientist which explicitly quote Uwingu CEO Alan Stern as saying the names generated by Uwingu’s contest will not be officially recognized by the IAU, but are a way to get the public involved and excited about exoplanets.

Anyone who implies that Uwingu is like the ‘name a star’ scams, or that they are out to make money to line their own pockets is completely misreading Uwingu’s website and completely missing the point. The profits go towards science research and education. So far Uwingu has given approximately $5,500 to several projects: Astronomers Without Borders, the Galileo Teacher Training Program, the Purdue Multiethnic Training Program, and the Allen Telescope Array for SETI.

Additionally, as the Uwingu Twitter feed confirmed, “No one at Uwingu has ever been paid, we have all worked for free from the start.”

The IAU’s statement on Friday infers that Uwingu is trying to sell “the rights to name exoplanets” and today Uwingu issued a statement that says the IAU’s press release “significantly mischaracterized Uwingu’s People’s Choice contest and Uwingu itself.”

As astronomer Carolyn Collins Petersen wrote on her Spacewriter’s Ramblings blog, nowhere on Uwingu’s website does it say that you’re buying the right to name a planet, as seems to be suggested by the IAU press release.

“If you donate a few dollars, you get to suggest a name,” she wrote. “You donate a few cents and you can vote for the coolest names. The coolest names win prizes. The money goes to research and education.”

And Stern has said the time has come where exoplanets should be named: “The IAU has had ten years to do something about this and they haven’t done anything,” he told Universe Today previously. “What we’re doing might be controversial, but that’s OK. It’s time to step up to the plate and do something.”

And many agree with his point that since the public is obviuosly intrigued and interested in exoplanets, they should be involved in the naming process, if only to suggest names. And as we’ve said before, since the IAU has said it will be difficult to come up with names since there are now hundreds of known explanets, Uwingu’s projects fits the bill of what is needed.

Also from Uwingu’s statement today:

Uwingu affirms the IAU’s right to create naming systems for astronomers. But we know that the IAU has no purview — informal or official — to control popular naming of bodies in the sky or features on them, just as geographers have no purview to control people’s naming of features along hiking trails. People clearly enjoy connecting to the sky and having an input to common-use naming. We will continue to stand up for the public’s rights in this regard, and look forward to raising more grant funds for space researchers and educators this way.

Over the weekend, the debate raged on the various social media outlets, and astronomer Jason Wright wrote a blog post that called out the IAU’s statement, saying it couldn’t be the official IAU policy, because “IAU policy is determined by democratic vote of its commissions and General Assembly. Neither has endorsed any nomenclature for planets, much less the assertions of the press release.”

Wright added that he contacted a member of Commission 53 (the IAU committee that will discuss the future of exoplanet naming) “and learned that they were not consulted for or even informed of this press release before it went out, and that the commission has not established a naming process since it met in Beijing in 2012.”

As far as the difference between “official” and “common” names, the IAU said in their press release that a “clear and systematic system for naming these objects is vital. Any naming system is a scientific issue that must also work across different languages and cultures in order to support collaborative worldwide research and avoid confusion.”

However, many people have pointed out that other sciences — like biology – have scientific names and common names that are both used and there doesn’t appear to be rampant confusion over this.

But stars can have several names as well, as astronomer Stuart Lowe wrote in his Astroblog, “Currently stars can have one proper name but also be in many different catalogues with different IDs.”

Uwingu pointed out in their statement that the star Polaris (its well-known common name!) is also known as the North Star, Alpha Ursae Minoris, HD 8890, HIP 11767, SAO 308, ADS 1477, FK5 907, and over a dozen more designations.

Uwingu also noted how non-scientific, informal names are prevalent in astronomy. Our own Milky Way galaxy is a great example, and “there are many instances where astronomers name things without going through the IAU’s internal process. There are many of features on Mars, ranging from mountains to individual rocks, with names applied by Mars-mission scientists and never adopted by, or even considered by, the IAU. And Apollo astronauts did not seek IAU permission before naming features at their landing sites or from orbit.”

Also, recent press releases reflect where astronomical objects were given names by astronomers without any IAU process such as Supernova Wilson, Galaxy cluster “El Gordo,” and the “Black Eye Galaxy.” “None drew attention from the IAU,” Uwingu said.

Planetary scientist and educator David Grinspoon (who is on Uwingu’s board of advisors) probably summed it up best in a comment he posted on Universe Today: “IAU maintains names for astronomers and that’s fine, but they do not own the sky. Planets are PLACES not just astronomical research objects, and if informal names for these places proliferate, outside of some self-appointed professional “authority”, and the public at large is more engaged in the exoplanet revolution, that is a very good thing indeed.”

Posted on by Elizabeth Howell

Launch! Anik G1 Satellite Aims To Ease Communications Overcrowding

Anik G1 lifts off from Baikonur, Kazakhstan on April 15, 2013. Credit: ILS Launch Services (screencap)

Update, April 16, 8:20 a.m. EDT: Anik G1 was successfully released from the upper stage of the rocket nine hours and 13 minutes after the launch. The satellite is now in orbit above Earth.

A new communications satellite aims to ease the strain of overcrowded communications networks in Latin America, while adding capacity to direct-to-home services in Canada and government and military users across the Americas.

Anik G1 lifted off at 2:36 p.m. EDT (6:36 p.m. UTC) today, April 15, from Baikonur, Kazakhstan. The satellite, carried by a Proton-M rocket, is still undergoing orbital maneuvers as of this writing; the upper Breeze-M stage will fire five times to put Anik G1 in the proper orbit.

These maneuvers should be completed about 9 hours after launch, if all goes well, at which point Anik G1 will separate.

Anik G1 is expected to last 15 years, a typical lifespan for a communications satellite. Once Anik G1 is activated, should all go well with the deployment, Canadian operator Telesat is marketing the satellite as a way to alleviate overcapacity in Latin American telecommunications services.

Continue reading “Launch! Anik G1 Satellite Aims To Ease Communications Overcrowding”

Posted on by Astronomy Cast

Enjoy Several New Podcasts at Astronomy Cast

Astronomy Cast has recently uploaded several new podcasts, and while we normally post them separately here on Universe Today, since there are a number of them arriving at once, here’s a list of the new ones:

 

We’ve recently had a ‘changing of the guard’ at Astronomy Cast as far as getting things posted to the AC website and getting podcasts loaded to the feed, and are now getting caught up. But as you probably know, Fraser and Pamela now record Astronomy Cast as part of Google+ Hangouts. You can watch them record live at Google+ (they usually record on Mondays at 12 noon Pacific time) or at the AstrosphereVids You Tube channel (where you can watch past Hangouts as well).

Posted on by Jason Major

Researchers May Have Finally Detected a Dark Matter Particle

The international Super Cryogenic Dark Matter Search (SuperCDMS) has detected what may be the particle that's thought to make up dark matter throughout the Universe.

Dark matter: it’s invisible, it’s elusive, it’s controversial… and it’s everywhere — in the Universe, yes, but especially in the world of astrophysics, where researchers have been exhaustively trying to reveal its true identity for decades.

Now, scientists with the international Super Cryogenic Dark Matter Search (SuperCDMS) experiment are reporting the detection of a particle that’s thought to make up dark matter: a weakly-interacting massive particle, or WIMP. According to a press release from Texas A&M University (whose high-energy physicist Rupak Mahapatra is a principal investigator in the experiment) SuperCDMS has identified a WIMP-like signal at the 3-sigma level, which indicates a 99.8 percent chance of an actual discovery — a “concrete hint,” as it’s being called.

“In high-energy physics, a discovery is only claimed at 5-sigma or better,” Mahapatra said. “So this is certainly very exciting, but not fully convincing by the standards. We just need more data to be sure. For now, we have to live with this tantalizing hint of one of the biggest puzzles of our time.”

If this is indeed a WIMP it will be the first time such a particle has been directly observed, lending more insight into what dark matter is… or isn’t.

Notoriously elusive, WIMPs rarely interact with normal matter and therefore are difficult to detect. Scientists believe they occasionally bounce off, or scatter like billiard balls from, atomic nuclei, leaving behind a small amount of energy capable of being tracked by detectors deep underground, particle colliders such as the Large Hadron Collider at CERN and even instruments in space like the Alpha Magnetic Spectrometer (AMS) mounted on the International Space Station.

A stack of crystal germanium CDMS detectors (Fermilab)
A stack of crystal germanium CDMS detectors (Fermilab)

The CDMS experiment, located a half-mile underground at the Soudan mine in northern Minnesota and managed by the United States Department of Energy’s Fermi National Accelerator Laboratory, has been searching for dark matter since 2003. The experiment uses very sophisticated detector technology and advanced analysis techniques to enable cryogenically cooled (almost absolute zero temperature at -460 degrees F) germanium and silicon targets to search for the rare recoil of dark matter particles.

This newly-announced detection actually comes from data acquired during an earlier phase of the experiment.

“This result is from data taken a few years ago using silicon detectors manufactured at Stanford that are now defunct,” Mahapatra said. “Increased interest in the low mass WIMP region motivated us to complete the analysis of the silicon-detector exposure, which is less sensitive than germanium for WIMP masses above 15 giga-electronvolts [one GeVa is equal to a billion electron volts] but more sensitive for lower masses. The analysis resulted in three events, and the estimated background is 0.7 events.”

Although Mahapatra says the result is certainly encouraging and worthy of further investigation, he cautions it should not be considered a discovery just yet.

“We are only 99.8 percent sure, and we want to be 99.9999 percent sure,” Mahapatra said. “At 3-sigma, you have a hint of something. At 4-sigma, you have evidence. At 5-sigma, you have a discovery.”

“In medicine, you can say you are curing 99.8 percent of the cases, and that’s OK. When you say you’ve made a fundamental discovery in high-energy physics, you can’t be wrong.”

– Dr. Rupak Mahapatra, SuperCDMS principal investigator, Texas A&M University

Advanced 6-inch silicon detectors developed by Mahapatra's lab at Texas A&M
Advanced 6-inch silicon detectors developed by Mahapatra’s lab at Texas A&M

The collaboration will continue to probe this WIMP sector using the SuperCDMS Soudan experiment’s operating germanium detectors and is considering using larger, more advanced 6-inch silicon detectors developed at the Texas A&M’s Department of Electrical Engineering in future experiments.

The team has detailed its results in a paper published in arXiv that eventually will appear in Physical Review Letters. Mahapatra will also announce the results today at 12 p.m. CDT in a talk at the Mitchell Institute for Fundamental Physics and Astronomy.

Source: Texas A&M University

(Read more about dark matter here and here.)

Posted on by Nancy Atkinson

Stunning Astrophoto: Jet Star Roller Coaster Meets Star Trails

Stars streak over the Jet Star rollercoaster in Seaside Heights, New Jersey, as it awaits removal from the Atlantic Ocean. Credit and copyright: Jack Fusco.

A victim of Hurricane Sandy provides the foreground for a stunning view of star trails over Seaside Heights, New Jersey. The Jet Star roller coaster and three other amusement rides fell into the ocean after the partial collapse of Casino Pier during Hurricane Sandy. The roller coaster sitting in the ocean became an iconic symbol of the hurricane’s destruction last fall. Astrophotographer Jack Fusco captured this absolutely incredible shot of the Jet Star under a blanket of stars on April 9, 2013. The Jet Star will soon be dismantled and removed. As one commenter on Flickr said, this shot will live on even after the roller coaster is gone.

See more of Jack’s work on Flickr, Google+ and his website, www.jackfusco.com

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.

Posted on by Elizabeth Howell

Spacewalkers To Give Cargo Spacecraft A Helping Hand

Friday's spacewalk is supposed to replace a navigational aid to guide in spacecraft, such as the European Space Agency's Automated Transfer Vehicle. Credit: NASA

Spacewalkers will replace a faulty navigational aid Friday to ensure that a cargo spacecraft in June docks safely with the  International Space Station.

Expedition 35 cosmonauts Pavel Vinogradov and Roman Romanenko will venture into space to remove and replace a broken retroreflector on the Russian Zvezda station module.  The first spacecraft to use the new retroreflector will be the European Space Agency’s automated transfer vehicle (ATV) Albert Einstein, which is scheduled to dock with the station in June.

The ATV has a videometer on board that shoots laser beams at retroreflectors on the outside of the station. Then, the videometer analyzes the pattern of light that is returned. Based on this pattern, it navigates towards the station and in for a docking.

Albert Einstein will carry about two tons of cargo to the station, including water, oxygen, and extra fuel to boost the space station’s orbit. Tipping the scales at 44,611 pounds (20,235 kg), this ATV will be the heaviest ever lifted by an Ariane rocket.

Replacing the retroreflector won’t be the cosmonauts’ only task. They’ll retrieve an experiment, called Biorisk, that is supposed to evaluate how much microbes affect spacecraft structures. They may also take the Vinoslivost experiment (which looks at how exposed materials behave in space) back inside, depending on how much time they have.

Pavel Vinogradov during a 2006 spacewalk. Friday will mark the seventh spacewalk for the veteran Russian cosmonaut. Credit: NASA
Pavel Vinogradov during a 2006 spacewalk. Friday will mark the seventh spacewalk for the veteran Russian cosmonaut. Credit: NASA

These experiments are part of the long-term mandate of the station’s activities to study how well people and structures survive after years in space. Based on the results, engineers back on Earth can make adjustments for spacecraft under development, making them more robust for long-term missions.

Additionally, the cosmonauts plan to install the Obstanovka experiment, which will look at “space weather” in the Earth’s ionosphere. This region of the atmosphere is where auroras arise after the Sun’s particles strike the area.

Besides producing these pretty patterns, space weather has a darker side: it can cause communications shortouts or hurt satellites. That’s why NASA has the Solar Dynamics Observatory and other spacecraft keeping a close eye on the sun. The agency wants to improve space weather predictions to protect infrastructure on Earth.

You can watch Expedition 35’s first spacewalk on NASA Television at 9:30 a.m. EDT (1:30 p.m. UTC) on Friday. The cosmonauts should head outside around 10:06 a.m. EDT (2:06 p.m. UTC). This could change depending on how quickly the cosmonauts depressurize the Pirs airlock and complete their pre-spacewalk checklist.

This spacewalk will be the seventh for Vinogradov and the first for Romanenko. Including this upcoming spacewalk, there have been 167 spacewalks performed to construct the space station and do maintenance.

Posted on by Fraser Cain

How Long Does it Take Sunlight to Reach the Earth?

How Long Does it Take Sunlight to Reach Earth?
How Long Does it Take Sunlight to Reach Earth?

Here’s a question… how long does it take sunlight to reach Earth? This sounds like a strange question, but think about it. Sunlight travels at the speed of light. Photons emitted from the surface of the Sun need to travel across the vacuum of space to reach our eyes.

The short answer is that it takes sunlight an average of 8 minutes and 20 seconds to travel from the Sun to the Earth.

If the Sun suddenly disappeared from the Universe (not that this could actually happen, don’t panic), it would take a little more than 8 minutes before you realized it was time to put on a sweater.

Here’s the math. We orbit the Sun at a distance of about 150 million km. Light moves at 300,000 kilometers/second. Divide these and you get 500 seconds, or 8 minutes and 20 seconds.

This is an average number. Remember, the Earth follows an elliptical orbit around the Sun, ranging from 147 million to 152 million km. At its closest point, sunlight only takes 490 seconds to reach Earth. And then at the most distant point, it takes 507 seconds for sunlight to make the journey.

But the story of light gets even more interesting, when you think about the journey light needs to make inside the Sun.

You probably know that photons are created by fusion reactions inside the Sun’s core. They start off as gamma radiation and then are emitted and absorbed countless times in the Sun’s radiative zone, wandering around inside the massive star before they finally reach the surface.

What you probably don’t know, is that these photons striking your eyeballs were ACTUALLY created tens of thousands of years ago and it took that long for them to be emitted by the sun.

Once they escaped the surface, it was only a short 8 minutes for those photons to cross the vast distance from the Sun to the Earth

As you look outward into space, you’re actually looking backwards in time.

The light you see from your computer is nanoseconds old. The light reflected from the surface of the Moon takes only a second to reach Earth. The Sun is more than 8 light-minutes away. And so, if the light from the nearest star (Alpha Centauri) takes more than 4 years to reach us, we’re seeing that star 4 years in the past.

There are galaxies millions of light-years away, which means the light we’re seeing left the surface of those stars millions of years ago. For example, the galaxy M109 is located about 83.5 million light-years away.

If aliens lived in those galaxies, and had strong enough telescopes, they would see the Earth as it looked in the past. They might even see dinosaurs walking on the surface.

We have written many articles about the Sun for Universe Today. Here’s an article about the color of the Sun, and here are some interesting facts about the Sun.

If you’d like more info on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We’ve also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Source: NASA