See Venus in Broad Daylight!

Look southeast before sunrise to spot the waning
Moon and Venus. These scenes are drawn for the middle of North America.
European observers: move each Moon symbol a quarter of the way toward
the one for the previous date. For clarity, the Moon is shown three
times actual size.

If it's clear at dawn on Monday and Tuesday, February 28th and March 1st, you can see one of nature's loveliest sights — Venus near the thin crescent Moon.

Thoughtful readers looking at the chart at right might have two questions. First, if the Moon is above Venus on Monday and below it on Tuesday, it must be very near it some time in between. When will this close approach happen, and where will it be visible?

Second, just how long into dawn will you be able to see this scene? The Moon is often visible during broad daylight. Is that true of Venus, too?

Let's answer the second question first. Yes, Venus is indeed visible to the unaided eye during broad daylight, assuming that the air is reasonably free of haze. In fact, it's startlingly easy to see — but equally hard to find. It's just a tiny pinprick of light amid the vast sea of blue sky. Even after you succeed in finding Venus, it's very easy to lose sight of it if you glance away for a moment.

For this reason, by far your easiest chance to observe Venus during the day is when it happens to be near the Moon — a much easier object to find. And that will happen twice for observers in the Americas: on Monday and again on Tuesday.

There's one way to be absolutely sure of observing Venus after the Sun has risen, but it requires a lot of time and patience. Go out a half hour before sunrise, when Venus is blindingly obvious, and track its position until the Sun rises, and even after. The way to do this is to periodically look down from Venus to the horizon, and see what landmark lies directly below it. Then it's relatively easy to relocate Venus by scanning upward from that landmark.


Venus and the Moon in broad daylight In these daylight scenes, the Moon is shown its actual apparent size relative to the distance between it and Venus. Venus is shown bright here for clarity, but appears much fainter against the bright daytime sky. Binoculars are not necessary to see either the Moon or Venus, but they're extremely helpful.

If you don't want to hang around outside for 45 minutes on a chilly late-winter morning, your second-best bet is to look when the Moon and Venus are due south and at their highest, which happens around 9 a.m. these mornings. Bring binoculars, because even the Moon is none too easy to spot during the day when it's a thin crescent.

Once you've located the Moon, use your binoculars to scan carefully to the left on Monday morning, using the February 28th diagram to tell you how far to scan. Most 7× to 10× binoculars actually have a field of view a bit bigger than what's shown, but the outer edge of the field is often a little hard to see.


Venus and the Moon in broad daylight In these daylight scenes, the Moon is shown its actual apparent size relative to the distance between it and Venus.

The closest approach between Venus and the Moon takes place when the Moon is below the horizon for the Americas. But it's a fine sight from eastern and central Asia, as shown in the March 1st diagram. By the time the Moon rises in the Americas on Tuesday morning, it's already well to the left of Venus. This is a second opportunity to spot Venus during daylight hours, but it's a bit tougher than on Monday because the Moon's phase has shrunk from roughly 15% to 10%, making it significantly harder to spot in the blue day sky.

As Solar Flares Grip The Nation

A series of solar flares have been gripping the nation's interest as the sun enters a period of increased activity. Solar Stormwatchers are just some of the enthusiasts who have been keeping an eye on the large explosions in the sun's atmosphere as they release intense bursts of radiation.

The Solar Stormwatch project  allows members of the public to use images from the NASA STEREO  to spot the explosions from the sun and the resulting clouds of particles as they make their way towards the earth. These particles, at their most disruptive, can cause communications to fail and lead to cuts to power supplies.

Professor Richard Harrison, Solar physicist and Principal Investigator for STEREO said; "We've just witnessed the brightest flares seen for four years. This was a series of so-called X-class flares - the highest category on the solar flare 'Richter scale'. The flares were near the centre of the Sun which means associated eruptions and clouds of solar particles can travel in our direction."

Dr Chris Davis, STEREO Project Scientist and leading scientist in Solar Stormwatch talks further about these latest developments.

The impact on on Earth depends on how the clouds of particles disrupt our magnetic field. The clouds themselves are magnetised and the direction of their magnetic fields and the speed they travel determines the type of impact. If their magnetic fields turn southward (opposite to the direction of the Earth's magnetic field) and their speed over the Earth exceeds 700 km per second, then we might expect some disruption - this is also the time to look out for aurora!

You can find out more by looking at the NOAA Space Weather Prediction Center website.

Here you can see the space environment in front of the Earth in real time - as measured using NASA's ACE (link opens in a new window) spacecraft. The areas to watch are the charts on the left and right hand side of page. The chart on the left shows significant activity when the dials reach the yellow or red areas; the Auroral map on the right of the page shows increased activity when areas of the map become more red.

There is also more on Lancaster University's Aurora watch website.

The Coolest Star. Literally.

The Coolest Star. Literally.

"It seems like once people grow up, they have no idea what's cool." -Bill Watterson

Well, at least we can all agree on what's not cool. The Sun.

With a surface temperature of around 6,000 Kelvins, the Sun is one of the hottest objects that we're all familiar with.

But when it comes to stars, the Sun is merely a "G-type" star.
It turns out that there are many types of stars that are -- typically
-- more massive, bluer, and hotter than our Sun.

In fact, O-stars, the hottest type, can have surface temperatures over 40,000 Kelvin, hot enough that they would be classified as "Ultraviolet stars," if only our eyes could see light that energetic.

But going down in temperature, we find that smaller, less
massive stars burn at lower temperatures. Once you get down to below
about 40% of the mass of the Sun, you go down to being a red-colored
M-star, with a temperature of only around 3,000 Kelvins.

M-stars still burn hydrogen into helium, like our Sun does, but
don't have enough mass to burn anything past that, and will die with
the weakest of whimpers, simply contracting and fading away.

But even M-stars need to have at least 7 to 8% of the Sun's
mass in order to be able to make helium in their cores. What happens if
you're less massive than that? Well, we do observe stars even cooler than M-stars, but we've had to look very hard to find them.

Dropping dramatically in temperature and brightness, we come to the newest class of stars: brown dwarfs. (That's dwarfs, not dwarves.)
These stars, of spectral type L, T, and (theoretically, thus far) Y,
are too small to burn hydrogen into helium. The brighter brown dwarfs can form deuterium, the lightest stable isotope of hydrogen, but the dimmest ones can't even do that.

Still, there's a fine line somewhere in between a large planet like Jupiter and a Y-type brown dwarf. And we are starting to figure out just what's in that grey area.

The lowest temperature brown dwarfs that we've discovered out there are right around 500 to 550 Kelvin, like this guy, which makes them much colder than Venus, and barely warmer, on average, than the planet Mercury.

That's right. We've discovered stars that are cooler than some of our planets.

The WISE spacecraft,
which took the picture above as its final image, may break this record
and discover the first Y-type brown dwarf when its data is completely
analyzed. How would this happen?

All stars made out of atoms that have run out of fuel: Y-type
brown dwarfs, stellar corpses (like white dwarfs), etc., contract under
their own gravity, and that's the source of their energy. Although it
will take at least hundreds of trillions of years (which is many times
the age of the Universe), eventually these stars will shrink to a
minimum, most stable configuration. At that point, there will be no
energy left to release, and these stars will become black dwarfs, huge clumps of matter with a temperature approaching absolute zero!

NASA Releasing First Views Of The Entire Sun On Super Sun-Day

NASA Releasing First Views Of The Entire Sun On Super Sun-Day


WASHINGTON -- NASA will score big on super SUN-day at 11 a.m. EST, Sunday, Feb. 6, with the release online of the first complete view of the sun's entire surface and atmosphere.

Seeing the whole sun front and back simultaneously will enable significant advances in space weather forecasting for Earth, and improve planning for future robotic or crewed spacecraft missions throughout the solar system.

These views are the result of observations by NASA's two Solar TErrestrial Relations Observatory (STEREO) spacecraft. The duo are on diametrically opposite sides of the sun, 180 degrees apart. One is ahead of Earth in its orbit, the other trailing behind.

Launched in October 2006, STEREO traces the flow of energy and matter from the sun to Earth. It also provides unique and revolutionary views of the sun-Earth system. The mission observed the sun in 3-D for the first time in 2007. In 2009, the twin spacecraft revealed the 3-D structure of coronal mass ejections which are violent eruptions of matter from the sun that can disrupt communications, navigation, satellites and power grids on Earth.

STEREO is the third mission in NASA's Solar Terrestrial Probes program within the agency's Science Mission Directorate in Washington. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the mission, instruments and science center.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., designed and built the spacecraft and is responsible for mission operations.

The STEREO imaging and particle detecting instruments were designed and built by scientific institutions in the U.S., UK, France, Germany, Belgium, Netherlands and Switzerland.