Tag Archives: astronomy

Don’t Miss The Geminid Meteor Shower This Weekend

Stargazers are in for a treat on Sunday and Monday as the Geminid meteor shower puts on a show.

After 10 p.m. ET (3 a.m. GMT) on the nights of December 13 and 14 you should be able to see a Geminid meteor every one or two minutes on average, Sky & Telescope predicts. NASA has also created a handy tool for you to calculate the activity at your chosen location at a particular time.

The Geminids will appear to radiate out of the Gemini constellation, hence the name. However, the meteors will appear from all corners of the sky, so you dont have to look in a particular direction.

As ever with viewing meteor showers, it always easier to see them if its a clear night and youre far away from the artificial glow of cities and streetlights. Its also good to go outside half an hour before the shower starts so your eyes become acclimatized to seeing in low light.

When you see a meteor, you are witnessing bits of debris burning up as they hitEarths atmosphere at over 127,100 kilometers per hour (79,000 miles per hour). The specks of cosmic dust are fragments from the 3200 Phaethon comet. This comet, which is just1.6 kilometers (3 miles) wide, makes an orbit around the Sun every 1.4 years.

Check out the NASA website for moreinformation.

Main image credit:Henry Lee/Flickr. (CC BY-ND 2.0)

Read more: http://www.iflscience.com/space/dont-miss-geminid-meteor-shower-sunday-and-monday

Hubble Spies Huge Explosion on Faraway Star

T-pyxidis-sept-2011

NASA’s Hubble Space Telescope has given astronomers a rare look at an enormous stellar eruption, allowing them to map out the aftermath of such blasts in unprecedented detail.

Hubble photographed an April 2011 explosion in the double-star system T Pyxidis (T Pyx for short), which goes off every 12 to 50 years. The new images reveal that material ejected by previous T Pyx outbursts did not escape into space, instead sticking around to form a debris disk about 1 light-year wide around the system.

This information came as a surprise to the research team.

“We fully expected this to be a spherical shell,” study co-author Arlin Crotts of Columbia University said in a statement. “This observation shows it is a disk, and it is populated with fast-moving ejecta from previous outbursts.”

The erupting T Pyx star is a white dwarf, the burned-out core of a star much like our own sun. White dwarfs are small but incredibly dense, often packing the mass of the sun into a volume the size of Earth.

T Pyx’s white dwarf has a companion star, from which it siphons off hydrogen fuel. When enough of this hydrogen builds up on the white dwarf’s surface, it detonates like a gigantic hydrogen bomb, increasing the white dwarf’s brightness by a factor of 10,000 over a single day or so.

This happens again and again. T Pyx is known to have erupted in 1890, 1902, 1920, 1944, and 1966, in addition to the 2011 event.

Such recurrent outbursts are known as nova explosions. (Nova is Latin for “new,” referring to how suddenly novas appear in the sky.) Novas are distinct from supernovas, even more dramatic blasts that involve the destruction of an entire star.

The new study clarifies just what happens to the material ejected by such outbursts.

“We’ve all seen how light from fireworks shells during the grand finale will light up the smoke and soot from shells earlier in the show,” co-author Stephen Lawrence of Hofstra University said in a statement. “In an analogous way, we’re using light from T Pyx’s latest outburst and its propagation at the speed of light to dissect its fireworks displays from decades past.”

The study represents the first time the area around an erupting star has been mapped in three dimensions, researchers said.

The new Hubble Space Telescope observations also help refine the distance to T Pyx, pegging it at 15,600 light-years from Earth. (Past estimates have ranged between 6,500 and 16,000 light-years.)

The team presented its results on June 4 at the 222nd meeting of the American Astronomical Society in Indianapolis. The study will also be published in the June 20 issue of the Astrophysical Journal Letters.

Image courtesy of NASA, ESA, A. Crotts, J. Sokoloski, and H. Uthas (Columbia University) and S. Lawrence (Hofstra University)

This article originally published at Space.com
here

Read more: http://mashable.com/2013/06/05/hubble-star-explosion/

See Venus and Saturn Shine Together Early Tuesday

See-venus-and-saturn-shine-together-early-tuesday-a2f7f352cc

Early Tuesday morning (Nov. 27), you’ll be able to watch two planets that will pass each other in the dawn.

The planets in question are Venus and Saturn. One planet will be slowly descending into eventual obscurity, while the other will become increasingly prominent in the days and weeks to come.

Look for Venus and Saturn shortly after 4:30 a.m. local time. The planets will appear very low above the east-southeast horizon, weather permitting. Brilliant Venus, shining with a steady silvery-white glow, will be passing about 0.6 degrees below and to the right of the much dimmer and yellower Saturn. (Your closed fist held at arm’s length covers 10 degrees of the night sky.)

About an hour later, at 5:30 a.m. local time, Saturn will high enough for good views through a telescope of its breathtakingly beautiful rings. The tilt of the rings continues to slowly increase and is now almost 18 degrees from edgewise. As for Venus, it displays a rather small gibbous shaped disk, 87% illuminated by the sun. Venus is about 70% brighter than Saturn’s larger, but duller, disk and rings.

After Tuesday morning’s rendezvous, which is known as a conjunction, the two planets will slowly go their separate ways.

Venus, which was so prominent during the summertime, is now rising later and appearing lower to the horizon in the dawn twilight. It has about another two months to go before it ultimately drops down into the bright morning twilight and disappears from our view, eventually transitioning into the evening sky by early next spring.

Saturn, on the other hand, will climb progressively higher and rise earlier, eventually becoming a prominent and well-placed evening object by the middle of spring.

If you look at both Venus and Saturn through a telescope, Venus is unquestionably the brighter of the two objects. But you might wonder how this is possible. After all, both planets are perpetually covered with clouds and their respective albedos — the proportion of the incident sunlight reflected by those clouds — are exactly the same at 76%.

Why then does Saturn appear so much duller than Venus if both are reflecting the same proportion of sunlight back toward the Earth?

The key is their distances from the sun. Compared to Venus, Saturn is 13.59 times farther away from the sun. And if we use the inverse square law — which states that the intensity of reflected sunlight is inversely proportional to the square of the distance from the sun — then 13.59 multiplied by 13.59 shows that sunlight striking Saturn’s cloud tops, is 184.69 times weaker compared to sunlight striking the cloud tops of Venus.

In any case, arise early on Tuesday and take a peek as the Venus, the Goddess of Beauty, snuggles up to Saturn, the God of Time.

Homepage image via iStockphoto, fpm.

This article originally published at Space.com
here

Read more: http://mashable.com/2012/11/26/watch-venus-saturn/

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