Category: Astronomy

Are you ready to take a closer look at the real “Lord of the Rings”? Then say hello to Saturn as it reaches opposition tomorrow night. With the yellow planet rising around sunset, highest in the south around midnight, and setting around sunrise, now is the time for observers and photographers to enjoy Saturn the most!

Right now Saturn is positioned in Leo about 5 degrees east of the constellation’s Alpha star – Regulus. Look for the asterism of a backwards question mark rising after sunset and the brightest “star” in the group will be Saturn! For observers who use only your eyes try comparing the distances by holding your hand at arm’s length. Saturn and Regulus will be separated by about 3 fingerwidths. Look less than a fistwidth further north and you’ll see a dimmer star – Gamma Leonis. Keep an eye on this trio in the days to come and you’ll easily see Saturn’s movement against the background stars!

For observers with binoculars, it’s possible to see elongations on either side of Saturn which are the beginnings of its ring system trying to resolve. Before you complain about not getting a good enough view, remember what you’re seeing is very much like what Galileo saw when he discovered Saturn in 1610. Saturn on Saturday? Why not! Saturn was named for the Roman god of agriculture and the day Saturday is also named after him.

While you’re watching, think on this… Saturn is the second biggest planet, but it’s also the lightest planet. If there was a bathtub big enough to hold Saturn, it would float in the water! Its diameter is approximately 75,000 miles (120,000 km) and more than 9 Earths could line up across it. It’s composed of 97% hydrogen gas, about 3% helium gas and about 0.05% methane, plus ammonia. One of the reasons it appears slightly flattened is because it is! Saturn rotates in 10 hours, 39 minutes in Earth time and this fast pace is what gives it a unique shape. It takes Saturn almost 30 years to complete an orbit around the Sun!

Now on to observing with a small telescope…

What’s that you say? You can barely see Saturn’s rings? You’re right. At the moment Saturn’s rings are only tilted about 8 degrees from our line of sight. Earth’s equator is tilted 23 degrees and this tilt gives our planet its four seasons. Each year as we orbit around the Sun, our tilt causes different parts of the planet to spend more time in sunlight. Days become longer… nights become shorter! Saturn’s equator is tilted very similar to ours at 27 degrees. This gives Saturn the same seasonal changes as we here on Earth experience. Because of the tilt of Saturn and the thinness of the rings, every 14 years the rings look like they’ve disappeared when viewed through a small or medium sized telescope.

For larger telescopes, it’s easier to see Saturn has a thin multiple ring system. The rings are made of chunks of rock and ice — some just tiny pieces of dust, some more than half a mile (one km) across. Observing Saturn at opposition is important because it will give you an opportunity to witness the Seeliger Effect. Only at opposition will you notice a distinct brightening of the ring system caused by backscattering of sunlight off the icy particles. While we’re “lined up”, keep an eye out for this unusual property as well as the shadow of the rings on the planet and the shadow of the planet on the rings.

And don’t forget those moons… Titan is easy visible to even small telescopes!

Imagine suddenly realizing that your house was twice as big as you originally thought. Okay, maybe that’s a little out there, but astronomers from Australia have calculated that the Milky Way is actually twice as thick as previously believed – doubling from the originally estimated 6,000 light-years to 12,000 light-years.

The calculation was made by a couple of astronomers from the University of Sydney. They were working with the accepted numbers for the dimensions of our home galaxy (6,000 light years thick, and 100,000 light-years wide) when they thought it might make sense to double check those basic assumptions.

They used an accepted technique for calculating distance; measuring the light from pulsars. When light from distant pulsars moves through the background material of the Milky Way (known as the Warm Ionised Medium), it slows down. The redder pulses of light actually slow down more than the bluer pulses.

By measuring the change in light from the pulsar, astronomers can determine how much material the light has traveled through.

When they used the old calculations for 40 different pulsars inside and above it, they got the old numbers. But when they just looked at 17 pulsars which are above and below the galactic disk they got a new, more accurate, estimate.

“Of the thousands of pulsars known in and around our Galaxy, only about 60 have really well known distances,” said Professor Bryan Gaensler. “But to measure the thickness of the Milky Way we need to focus only on those that are sitting above or below the main part of the Galaxy; it turns out that pulsars embedded in the main disk of the Milky Way don’t give us useful information.”

Their results were presented in January at the annual meeting of the American Astronomical Society in Austin, Texas. Some of Dr. Gaensler’s colleagues appreciated the revised calculations, while others… not so pleased at the implications for their own research.

Original Source: University of Sydney

From beginning to end, the February 20/21 lunar eclipse lasts about three hours and twenty-six minutes and we’re down to less than 72 hours to prepare. While that seems like plenty of time, photographers will want to note that Saturn will be joining the eclipse show as well!

Although the separation will vary slightly with the observer’s position on Earth, for most of us the bright, yellowish visage of Saturn will be less than 3 degrees away from the Moon’s northern limb. For those of you who enjoy photographing the night sky, this will be a tremendous opportunity to both capture an astronomy event and a conjunction at the same time! This type of event – when things interestingly align in the sky is also sometimes called an “appulse”. For all we know, we could even be experiencing a syzygy!

Regardless of what word you want to put on it, it’s definitely going to be a sight worth seeing. Let’s take a look at where the action is happening!

For viewer on Eastern Standard Time the eclipse will enter the partial phase on February 20 at 08:43 pm; for Central Standard Time, 07:43 pm; for Mountain Standard Time, 06:43 pm; and Pacific Standard Time at 05:43 pm – before sunset. For viewers in Europe and Africa, the action begins at the beginning of a new day – on February 21 at 01:43 am GMT. (Sorry, to the good folks down under and in the Far East… no eclipse will be visible.) Totality will begin at 10:01 pm EAST, 09:01 pm CST, 08:01 pm, MST, 07:01 pm PST, and 03:01 am GMT and end precisely 50 minutes later. Then, you have 1 hour and 18 minutes left as the Moon slowly slides out of the Earth’s shadow once again.

For a significant portion of “Universe Today” readers, the entire eclipse will be visible and it’s time to enjoy the last we’ll see for a couple of years. For those experiencing the eclipse as the Moon sets… Don’t despair. You’ll enjoy one of the darkest eclipses you’ll ever see while viewers on the west coast of the Americas will see the eclipse in progress as the Moon rises. Don’t wait until the last minute to prepare your observing area or your cameras. For those with camcorders, you have a great opportunity to video the entire event! Don’t forget that cell phones take great images and even the most common camera can take a great shot of the eclipsed Moon when held to the eyepiece of a telescope. If you’re timing the event, have your notes ready, and most of all… Have a good time!

Wishing all of you clear skies!

At some point in the last year or so, the Sun-like star tau Bootis completely flipped its magnetic field. The star’s north pole became its south pole, and vice versa. It this going to happen to our own Sun? Yes! Don’t panic though; in fact, it happens every 11 years or so.

Even thought the Sun’s magnetic field flip has been well observed, astronomers have never seen this happen on another star. With the Sun, the field reversals are closely linked to varying number of sunspots on its surface. The magnetic field flip happened last time in 2007, when the Sun was at the “solar minimum”.

The Earth has been recorded to change its magnetic field too, but this event has happened very erratically in the past, and theres no way to predict when it’s going to happen again in the future.

And international team of astronomers were watching the star tau Bootis with the Canada-France-Hawaii Telescope Mauna Kea as part of a survey measuring the magnetic field of stars. On one sweep the star had one configuration, and later on, the magnetic field was reversed.

Since this event happened within just two years of observations, it’s likely that tau Bootis flips its field even more quickly than the Sun’s own 11-year cycle. Even more interesting is the recent discovery that the star is orbited by a massive planet. It’s a hot Jupiter planet, six times the size of Jupiter, but only 1/20th the distance from the Earth to the Sun.

The planet is so close, it has become tidally locked with the star, similar to the way the Moon only shows one face to the Earth. It’s possible that the tidal interactions between the star and the planet somehow speed up the surface of tau Bootis, and encourage these magnetic flips.

The astronomers are planning to keep their telescopes firmly targeted at tau Bootis, checking the magnetic field of the star regularly. If it flips again, they’ll be ready.

The research was published this week in the British journal Monthly Notices of the Royal Astronomical Society.

Original Source: Institute for Astronomy News Release

It’s time for another pretty picture. This time you’re looking at an image of the Rho Ophiuchi dark cloud, captured by NASA’s Spitzer Space Telescope. It’s one of the closest star-forming regions to the Earth, located a mere 407 light-years away.

The nebula is mostly a large cloud of molecular hydrogen. This is the main material that all stars form from. Some gravitational event caused a cloud of this hydrogen to collapse down, condensing into vast regions of star formation.

According to recent X-ray and infrared studies, there are more than 300 newly forming stars in the central nursery. And their average age is only 300,000 years old; much younger than our own Sun’s billions of years.

The colours look nice, but that’s not what you’d actually see if you could travel to “Rho Oph”. Its colours were chosen by astronomers to clearly highlight the various temperatures and evolutionary stages of the various stars. The young stars are surrounded by disks of gas and dust, and show up as red in the image.

The extended white nebula in the centre right of the image is glowing bright in infrared radiation because of the dust there has been heated by bright young stars. The rest of the stars forming are concentrated into the filament of cold, dense gas that shows up as a dark cloud in the lower centre and left side of the image.

Original Source: Spitzer News Release