Tag Archives: stars

Papyrus Reveals Ancient Egyptian Astronomical Knowledge

Researchers from the University of Helsinki have proposed that ancient Egyptians 3,000 years ago were the first to record the variability of a distant star and their records could provide useful information for astronomers today.

A new paper published in PLOS ONE explains how the Egyptian Cairo Calendar from 1244 to 1163 B.C. describes the variability of a binary star system called Algol. In the calendar, there are two significant periods of time for two gods 29.6 and 2.85 days. The former relates to the period of the Moon, while the latter almost perfectly matches the variability of Algol which today is 2.867 days, or two days, 20 hours, and 49 minutes.

This theory had been proposed in 2013 but, understandably, had been met with some skepticism. However, the researchers now say they are more confident in their claims, and say that Algol relates to the deity Horus.

I would have serious doubts, if someone claimed, for example, that the Bible contains information about water in Mars, said lead author Lauri Jetsu in a statement. We claimed that Ancient Egyptian religious texts contain astrophysical information about Algol. It was no surprise to us that there were, and there still are, sceptics.

Shown is an extract of the Cairo Calendar papyrus, used courtesy of Lauri Jetsu

An eclipsing binary is a pair of stars that, as viewed from Earth, rotate around each other and block each other’s light. Thus, this particular star dims regularly in brightness as it orbits its companion. Algol is found in the constellation Perseus about 92.8 light-years from us; the larger star is about 3.5 times the radius of the Sun, and the smaller about 2.7. They are separated by about 0.062 astronomical units (AU, one AU is the Earth-Sun distance).

The variability of Algol, which can be seen with the naked eye, was thought to have been first recorded by Italian astronomer Geminiano Montanari in 1667, although it was not until 1783 that British astronomer John Goodricke suggested another object may be the cause of the dimming. Based on this latest assumption, however, the record for discovery of this star’s variability may have to be re-awarded.

Perhaps most interestingly, the discovery reveals that the variability of the star has decreased very slightly over three millennia, by about 0.017 days. Rather than being an error, the researchers postulate that this could be due to the transfer of mass between the two stars affecting their orbits.

In fact, this would be the first observation that confirms the period increase of Algol and it also gives an estimate of the mass transfer rate, added Jetsu, possibly providing an important tool for astronomers today to learn more about eclipsing binaries.

Read more: http://www.iflscience.com/space/ancient-egyptians-knew-about-distant-flashing-star-3000-years-earlier-thought

Mark Your Calendar for Spring Meteor Showers and Eclipses

Lunar-eclipse

As the Moon passed almost directly through the center of Earth’s shadow on July 16th, sky gazers in the Pacific hemisphere were graced by a lingering lunar eclipse.

From eclipses and planets to meteor showers galore, the northern spring season of 2014 will bring a number of eye-catching celestial sights for stargazers on Earth.

Weather permitting, some of the best spring night sky events could be readily visible without the aid of binoculars or a telescope, even from brightly-lit cities. But you’ll need to know when and where to look to make the most of the season.

I’ve always felt that many astronomers started their careers as perceptive children who responded to the thrill of witnessing a noteworthy astronomical event. So whether you want to impress a youngster, or you’re simply hoping to witness a head-turning astronomical event for yourself, it always helps to be ready in advance by marking your calendar and highlighting a number of these special dates:

April 14 and 15: Mars’ closest approach in 2014 and a total eclipse of the moon

During the overnight hours of April 14 and 15, it will be a night for viewing first Mars and later the full moon.

First, Mars will come to within 57.4 million miles of our planet, making its closest approach to us since Jan. 3, 2008. All through the night, Mars will resemble a dazzling star shining with a steady fiery-colored tint making it a formidable sight; its brightness will match Sirius, the brightest of all the stars.

As a bonus, later that very same night (actually during the early hours of April 15) North America will have a ringside seat to see a total lunar eclipse when the Full Moon becomes transformed into a mottled reddish ball for 78 minutes as it becomes completely immersed in the shadow of the Earth.

This total lunar eclipse will be the first one widely visible from North America in nearly 3.5 years. The Americas will have the best view of this eclipse, although over the Canadian Maritimes, moonset will intervene near the end of totality. Of special interest is the fact that the moon will appear quite near to the bright star Spica, in the constellation Virgo, during the eclipse. They actually will be in conjunction a couple of hours prior to the onset of totality, but they’re still relatively near to each other when the eclipse gets underway.

April 22: The Lyrid meteor shower

Rather favorable circumstances are expected for this year’s Lyrid meteor shower, predicted to be at maximum this morning. The radiant, located near the brilliant bluish-white star Vega, rises in the northeast about the time evening twilight ends, and viewing will improve until light from the last-quarter moon begins to interfere just after 2 a.m. your local time.

Under the best conditions, 10 to 15 members of this shower can be seen in an hour by a single observer. The Lyrids remain about a quarter of their peak number for about two days. These bright meteors are associated with Thatcher’s Comet of 1861.

April 28 and 29: A Ring Eclipse that nobody will see?

It is quite possible that only penguins will witness the annular solar eclipse, also known as a “ring of fire” solar eclipse. That’s because it will occur within the uninhabited region of Wilkes Land in Antarctica.

Those living in southernmost parts of Indonesia as well as Australia (where it will be autumn) will at least get a view of a partial eclipse of the sun. Because the axis of the moon’s antumbral shadow misses the Earth and only its edge grazes Antarctica, it makes an accurate prediction of the duration of annularity all but impossible.

May 6: The Eta Aquarid meteor shower

The annual Eta Aquarid meteor shower — “shooting stars” spawned by the famed Halley’s Comet — is scheduled to reach maximum early this morning. It’s usually the year’s richest meteor display for Southern Hemisphere observers, but north of the equator the Eta Aquarid shower is one of the more difficult annual displays to observe.

From mid-northern latitudes, the radiant (from where the meteors appear to emanate) rises about 1:30 a.m. local daylight time, scarcely two hours before morning twilight begins to interfere. At peak activity, about a dozen shower members can be seen per hour by a single observer with good sky conditions from latitude 26 degrees North, but practically zero north of latitude 40 degrees. The shower remains active at roughly one-half peak strength for a couple of days before and after the maximum. Conditions this year are excellent; the moon is absent from the predawn sky for more than a week around maximum.

May 10: Saturn at opposition

The ringed planet Saturn reaches opposition; it rises in the east-southeast at dusk, is due south in the middle of the night and sets in the west-southwest at dawn. Once it gains enough altitude, it appears similarly as bright as the zero-magnitude stars Arcturus and Vega.

Saturn’s famous rings appear much more impressive than in recent years, since they are now tipped by 21.5 degrees from edge on.

May 24: Possible outburst of bright meteors

Perhaps the most dramatic sky event in 2014 could come at the start of the Memorial Day weekend. In the predawn hours of Saturday, May 24, our planet is expected to sweep through a great number of dusty trails left behind in space by the small comet P/209 LINEAR.

This unusual cosmic interaction might possibly result in an amazing, albeit brief display of meteors — popularly known as “shooting stars” — perhaps numbering in the many dozens . . . or even hundreds per hour. Nobody knows exactly how many meteors will be seen, but several meteor scientists believe that because the particles will be unusually large, the meteors will be outstandingly bright.

May 25: Mercury attains its greatest elongation

The planet Mercury will reach its greatest elongation, or greatest angular distance, east of the sun on this night. This is Mercury’s best evening apparition of the year; it sets about 100 minutes after sunset. An hour after sunset, look low above the west-northwest horizon; the speedy planet should be easily visible as a yellowish “star.”

Mercury will appear somewhat brighter up to two weeks before this date, and noticeably dimmer for about a week afterwards.

This article originally published at Space.com
here

Read more: http://mashable.com/2014/04/01/spring-stargazing-guide/

See ‘Summer Triangle’ in Night Sky This Weekend

Summer-triangle

This weekend, during the late evening hours, search for the famous “Summer Triangle” high in the eastern sky.

The triangle consists of three of the brightest stars in the sky, each the brightest in its own constellation. Bluish-white star Vega in Lyra (the lyre) is the brightest in the triangle, with yellow-white Altair in Aquila (the eagle) and white Deneb in Cygnus (the swan), following it as second- and third-brightest in the configuration.

From our viewpoint, Vega appears twice as bright as Altair and more than three times brighter than Deneb. But sometimes things are not always what they seem. We know that Vega clearly is more luminous compared to Altair, because it’s situated at a greater distance from us.  Altair is 17 light years away, while Vega is just a little farther out at 25 light years away.

The light you’re seeing from Altair tonight started on its journey to Earth in 1996, and the light from Vega started on its way toward Earth back in 1988. But brilliant Vega actually pales in comparison with Deneb, one of the greatest supergiant stars known.

Deneb’s distance measures 1,467 light-years from Earth with a luminosity computed to be more than 60,000 times that of the sun. Because its light takes nearly 15 centuries to reach us, Deneb merely appears as a fairly conspicuous but by no means particularly notable star.

See the Milky Way

With the moon arriving at new phase on Monday, July 8, and then waxing to just a thin crescent phase by week’s end, there is no better time than now to observe the beautiful summer Milky Way.

Under a dark sky with a good pair of binoculars or a telescope you can now observe millions of sparkling little stars that make up this glowing, irregular belt of luminosity.

It appears to arch from the north-northeast to the south-southeast, with its brightest and most spectacular region running across the summer triangle and beyond toward the south-southeast horizon.

There appears to be a great black rift dividing it into two streams (called the “dark bifurcation”), beginning with Cygnus and extending down toward the south. Also in Cygnus is the black void known as the “northern coal stack.” The coal stack and the rift are not holes in the Milky Way, but rather are vast clouds of dust “floating” out in interstellar space which present a solid and impenetrable curtain between us and the more distant stars.

Star-Crossed Lovers

There have been many stories, myths and legends told about the Milky Way across different cultures.

In a Japanese legend involving the galaxy, the star Vega represented Orihime, the weaving princess, who produced brilliantly colored fabrics. Across the “heavenly river” (the Milky Way), Altair represented the cow herder Hikoboshi, who was also known as Kengyu.

After meeting each other, they received divine permission to marry, whereupon both abandoned their occupations. This angered the gods who consequently separate them and send them back to their original jobs on opposite sides of the heavenly river.

The couple, however, received permission from the gods to get together for one night each year. That special night is July 7 — but only if the sky is clear.

As a result, the evening of July 7 has evolved into a young people’s holiday in Japan called Tanabata, meaning “evening of the seventh.” Prayers are offered for clear skies so that Orihime and Hikoboshi, the star-crossed lovers can be reunited.

Popular customs relating to the festival vary by region, but generally, girls wish for better sewing and craftsmanship, and boys wish for better handwriting by writing wishes on strips of paper. The date of Tanabata also varies by region, but the first festivities begin on July 7 of the Gregorian calendar.

The original Tanabata date was based on the Japanese lunisolar calendar, which is about a month behind the Gregorian calendar. As a result, some festivals are held on July 7, some last for a few days around August 7 and others take place on the seventh day of the seventh lunar month of the traditional Japanese lunisolar calendar, which is usually in August in the Gregorian calendar.

This year, the Gregorian date of “the seventh day of the seventh lunar month of the Japanese lunisolar calendar” will fall on Aug. 13.

Editor’s note: If you snap an amazing picture of the night sky that you’d like to share for a possible story or image gallery send photos, comments and your name and location to Managing Editor Tariq Malik at spacephotos@space.com.

Image courtesy of Flickr, Socalastro

This article originally published at Space.com
here

Read more: http://mashable.com/2013/07/05/summer-triangle/

Our Nearest Galactic Neighbor Revealed In Stunning Clarity

This stunning new image from the European Southern Observatory (ESO) reveals the closest galaxy to our Milky Way in exquisite detail.

Called IC 1613, it is more accurately a dwarf galaxy,owing to its relatively minute size. Also known as Caldwell 51, this galaxy measures roughly 10,000 light-years across, compared to 100,000 light-years for the Milky Way. It is located about 2.3 million light-years from Earth in the constellation Cetus.

This latest image reveals just how clean the galaxy is, with very little cosmic dust, meaning its innards can be studied in great detail. It was taken by the OmegaCAM camera on the ESOs Very Large Telescope (VLT) Survey Telescope in Chile, and also reveals a cloud of bright pink gas within the galaxy.

Discovered in 1906 by German astronomer Max Wolf, we now know that IC 1613 is part of our Local Group,a neighborhood of more than 50 galaxies. And we know IC 1613s distance from us very precisely, thanks to its cleanliness. This allows us to see distance marker stars, Cepheid variables and RR Lyrae variables, which flash with a regular beat that lets us calculate their distance.

In fact, IC 1613 helped astronomers refine the technique of using these stars to measure distances in the universe, something first proposed by the underappreciated astronomer Henrietta Swan Levitt in the early 20th Century.

Read more: http://www.iflscience.com/space/our-nearest-galactic-neighbour-revealed-stunning-clarity

Astronomers Have Discovered The Oldest Stars In Our Galaxy

An international team of astronomers has discovered some of the oldest stars in the Milky Way.In the process, they were able to learna lot about the abundance of different elements in the very early universe.

These stars, which are part of the second generation of stars to form in the universe, were discovered near the very center of the Milky Way and they are believed to have started shining200 million years after the Big Bang. The scientists thinkthat their findings, published in Nature,give an indication ofthe life and death of the very first stars.

The first stars are believed to have been huge, havingup to 1,000 times the mass of the Sun. It is thought that when these objects reached the end of their lives, they exploded inhypernova explosions,tens of times stronger than the supernovae we see in the universe today.The first generation havenot been directly observed yet, but astronomers hope to see them when the James Webb Space Telescope(JWST) starts operation in 2018.

The second generation, including the stars from this study, are metal-poor: They are made almost exclusively of helium and hydrogen, with only traces of heavier elements (the metals). The more metal a star has, the quicker it forms and the smaller it is.

After the Big Bang, the universe was composed of just hydrogen and helium. This is why the first-generation stars were so big.The carbon in our bodies, the oxygen in the air and all the other heavy elements we find in the universe were formed by the first two generations of stars.

The discovery didnt come easy. There are millions of stars in the Milky Ways bulge, so the team had to develop a strategy to make the gargantuan task of observing them in detailmore manageable.

Since very metal-poor stars are slightly bluer than other stars, the researchersselected 14,000 promising stars from the ANU SkyMapper telescope in Australia. Only 23 of themwerethen studied inmore detail in follow-up observations.

There are so many stars in the centerof our galaxy finding these rare stars is really like looking for a needle in a haystack, said co-authorDrAndrew Casey of Cambridges Institute of Astronomy in a statement. But if we select these stars in the right way, its like burning down the farm and sweeping up the needles with a magnet.

The elements released by the first stars act as a chemical signature that is still present in the stars observed in the study.

This work confirms that there are ancient stars in the centre of our galaxy. The chemical signature imprinted on those stars tells us about an epoch in the universe thats otherwise completely inaccessible, said Casey. The universe was probably very different early on, but to know by how much, weve really just got to find more of these stars: more needles in bigger haystacks.

Read more: http://www.iflscience.com/space/discovery-ancient-stars-sheds-light-primordial-hypernovae

The Pulsar That ‘Vaporized’ a Billion-Ton Asteroid

Pulsar-in-space

This artist’s concept depicts the pulsar planet system discovered by Aleksander Wolszczan in 1992.
Image: NASA JPL-Caltech

You know when you’re having a bad day when you get hit by a billion ton asteroid. But for a pulsar 37,000 light-years away, it’s just a another day at the office. And besides, PSR J0738-4042 has an uber-powerful X-ray blaster to deal with errant space rocks.

Astronomers of Australia’s Commonwealth Scientific and Industrial Research Organisation made the pulsar-pounding, asteroid-zapping discovery while using the Parkes Telescope to study the dusty, high-radiation environment surrounding the tiny spinning husk of the dead star. Pulsars are spinning compact stellar objects known as neutron stars that generate powerful beams of radiation from their intensely magnetized poles that, if aligned correctly with Earth, can be observed as ultra-precise radio pulses.

Pulsars are considered the most precise ‘clocks’ in the universe, but if a pulsar’s pulse timings abruptly change, a cataclysmic event has likely occurred.

In the case of PSR J0738-4042, the CSIRO astronomers noticed weird changes in the pulsar’s timing and its characteristic pulse, signals that the researchers have attributed to multiple asteroid hits.

“One of these rocks seems to have had a mass of about a billion tons,” said CSIRO astronomer Ryan Shannon in a press release.

In 2008, Shannon theorized that should a large rocky object, like an asteroid or even a small planet, collide with a pulsar, the pulsar will react in a very precise way; now it seems PSR J0738-4042 has become the prime candidate as observational evidence for this theory. The time of the pulse has lengthened and the radio signal received by Parkes has changed.

“We think the pulsar’s radio beam zaps the asteroid, vaporizing it. But the vaporized particles are electrically charged and they slightly alter the process that creates the pulsar’s beam,” said Shannon. The electrically charged particles interact with the pulsar’s magnetic field, like a magnetic blender, generation energy, sapping some of the pulsar’s angular momentum. This has a drag effect, slowing the spin rate. However, once all the ionized material has been converted to energy, the pulsar is expected to return to its pre-asteroid strike spin rate.

It is thought that the surrounding asteroids originated from the star that exploded to form the pulsar. The pulsar is a byproduct of a supernova, but before the star went supernova, it formed a system of rocky bodies, such as the billion ton asteroid and, possibly, planets.

This asteroid-vaporizing event is exiting in that it proves that rocky debris that formed before the star went supernova persisted after the star’s death, forming a debris disk around PSR J0738-4042. It’s possible that the surviving debris disk could be rejuvenated, spawning the agglomeration of larger and larger objects, potentially forming new planets.

The discovery of asteroid vaporization events close to PSR J0738-4042 is an interesting development in the study of disks surrounding pulsars. For example, another pulsar, J0146+61, has been found to be sporting a dusty debris disk and, in 1992, two planet-sized objects were discovered orbiting pulsar PSR 1257+12.

“This sort of dust disk could provide the ‘seeds’ that grow into larger asteroids,” said Ph.D. student Paul Brook, of the University of Oxford and CSIRO who led the PSR J0738-4042 study.

This research has been published in The Astrophysical Journal Letters.

This article originally published at Discovery News
here

Read more: http://mashable.com/2014/02/23/pulsar-zaps-giant-asteroid/

An exoplanet has been discovered orbiting our solar twin

There are billions upon billions of stars in the sky – but surprisingly few of them are a lot like our sun. Astronomers using the HARPS planet finder via the ESO’s 3.6-meter telescope at the La Silla Observatory in Chile have found three exoplanets in the star cluster Messier 67. One of these planets is incredibly unique, as it orbits the star eso1337, which is our true solar twin. This is the only known solar twin in a star cluster that has a planet. The research was led by Anna Brucalassi of the Max Planck Institute for Extraterrestrial Physics and will be published in an upcoming edition of the journal Astronomy & Astrophysics.

Messier 67 (M67) is an open cluster of stars in the constellation Cancer about 2,800 light years away. The stars are roughly the same age as our sun. It has been estimated that there are over 500 stars in the cluster, about 100 of which are very similar to our sun. 

The planets were discovered during a six-year-long study of 88 stars in the cluster. The stars were chosen for their brightness and accessibility, as many of the stars are too faint to detect any orbiting planets. One of the stars with a planet that was discovered is a massive red giant, while the second is a main sequence star, like our sun. Eso1337, however, is nearly identical to our sun in relation to size, mass, and composition.

Unfortunately, none of these planets are in their respective star’s habitable zones, as they are far too proximal to the star to have liquid water. The planet orbiting the the red giant is more massive than Jupiter and takes 122 Earth days to complete a revolution. The other two planets have about 33% of Jupiter’s mass and have orbits that take about a week. 

Astronomers will use these planets to learn how planets can form in these star clusters, where everything is relatively dense. It will also allow them to determine if planets are more or less likely to form around the more massive stars, or if less massive stars are more likely to be adorned with a planetary entourage. 

Read more: http://www.iflscience.com/space/exoplanet-has-been-discovered-orbiting-our-solar-twin

On brown dwarfs, storms of molten iron are always forecast

Brown dwarfs are much smaller and cooler than our sun. They might not be massive enough to have a core that performs nuclear reactions, but they do have extreme conditions. Using the Spitzer Space Telescope astronomers were able to find evidence that most, if not all, brown dwarfs have intense storms of molten iron moving at high speeds. The results were published in The Astrophysical Journal and were presented this week at the 223rd Meeting of the American Astronomical Society in Washington, D.C.

Because brown dwarfs don’t emit a lot of visible light, they are best viewed with infrared.  Astronomers used the Spitzer Space Telescope to observe over 40 brown dwarfs and searched for any variations in the luminosity as evidence of an active weather system. More than 20 of the stars observed indicated that there was indeed fluctuations in the light visible. The brighter light indicates a cloud-free portion, and the light is dimmer when clouds and storms are in the way. The variations occur as the brown dwarf spins on its axis. These storms are very intense, with hurricanes causing lightning along with high winds that whip around molten iron, sand, and even salt. 

The researchers have likened these storms to Jupiter’s Great Red Spot, which is larger than three Earths and has been going on for over 300 years. Even though they only observed these light fluctuations in about half of the stars, the team began the study under the assumption that half of them may not be oriented in the correct way to see it. This means that there is a possibility that all brown dwarf stars are home to some incredibly hellacious storms.

The team chose to observe weather on brown dwarfs instead of exoplanets merely out of simplicity. Studying the atmosphere of exoplanets can be tricky, given that the glare of the parent star. This was done as part of the “Weather on Other Worlds” project for Spitzer. Future studies will seek to better understand the weather on brown dwarfs and also extend to gas giant exoplanets like Jupiter, which are a lot like much smaller cousins. 

Brown dwarfs are essentially failed stars. During formation, they were not able to accumulate enough mass to sustain nuclear hydrogen fusion in their core. Without these reactions, they are technically already “dead” and won’t go supernova like regular stars will. They are anywhere from 13-80 times the mass of Jupiter and were confirmed for the first time in 1995. The difference between a small brown dwarf and a large gas planet comes down to the ability to fuse deuterium. While this is an isotope of hydrogen, which brown dwarfs shouldn’t be able to fuse, the extra neutron makes deuterium fusion possible at much lower temperatures and densities.

Read more: http://www.iflscience.com/space/brown-dwarfs-storms-molten-iron-are-always-forecast