Universe Today

August 24, 2009December 24, 2015 by Nancy Atkinson

How Close Did Hurricane Bill Come to the US East Coast?

Hurricane Bill skirts the Eastern Coast of the US. NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center.

[/caption]
Hurricane Bill kept its distance from the US mainland, seemingly skirting along the eastern seaboard and fitting perfectly within the coastline curves on this NASA satellite image. Thankfully, the storm largely missed the eastern states, with the center of the storm well off the coast. It appears Bill will keep its distance from the Canadian coast as well. It has now been downgraded to a tropical storm, and is expected to weaken over the next 24 hours. As of late Sunday night, the storm had maximum sustained winds near 120 kilometers (75 miles) per hour with higher gusts. This image was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, taken at 2:00 p.m. EDT (14:00 UTC) on August 23, 2009.
Source: NASA Earth Observation website

August 24, 2009March 1, 2020 by John Carl Villanueva

What is the Oscillating Universe Theory?

The Oscillating Universe Theory is a cosmological model that combines both the Big Bang and the Big Crunch as part of a cyclical event. That is, if this theory holds true, then the Universe in which we live in exists between a Big Bang and a Big Crunch.

In other words, our universe can be the first of a possible series of universes or it can be the nth universe in the series.

As we know, in the Big Bang Theory, the Universe is believed to be expanding from a very hot, very dense, and very small entity. In fact, if we extrapolate back to the moment of the Big Bang, we are able to reach a point of singularity characterized by infinitely high energy and density, as well as zero volume.

This description would only mean one thing – all the laws of physics will be thrown out of the window. This is understandably unacceptable to physicists. To make matters worse, some cosmologists even believe that the Universe will eventually reach a maximum point of expansion and that once this happens, it will then collapse into itself.

This will essentially lead to the same conditions as when we extrapolate back to the moment of the Big Bang. To remedy this dilemma, some scientists are proposing that perhaps the Universe will not reach the point of singularity after all.

Instead, because of repulsive forces brought about by quantum effects of gravity, the Universe will bounce back to an expanding one. An expansion (Big Bang) following a collapse (Big Crunch) such as this is aptly called a Big Bounce. The bounce marks the end of the previous universe and the beginning of the next.

The probability of a Big Bounce, or even a Big Crunch for that matter, is however becoming negligible. The most recent measurements of the CMBR or cosmic microwave background radiation shows that the Universe will continue on expanding and will most likely end in what is known as a Big Freeze or Heat Death.

CMBR readings are currently being gathered by a very accurate measuring device known as the WMAP or Wilkinson Microwave Anisotropy Probe. It is the same device that has measured with sharp precision the age of our universe. It is therefore highly unlikely that future findings will deviate largely from what has been discovered regarding the Universe’s expansion now.

There is however one mysterious entity whose deeper understanding of may change the possibilities. This entity, known as dark energy, is believed to be responsible for pushing the galaxies farther apart and subsequently the universe’s accelerated expansion. Unless its actual properties are very dissimilar from what it is showing now, we may have to shelve the Oscillating Universe Theory.

We’ve got a few articles that touch on the Oscillating Universe Theory here in Universe Today. Here are two of them:

Big Bounce
Fate of the Universe

Physics World also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources:
PBS.org
Wikipedia

August 24, 2009December 21, 2015 by Nancy Atkinson

Podcast: Astronomy and New Media

Astronomy is one of the scientific fields that have been completely shaken up by new media. The Internet has enabled communication between researchers in a dramatic new way, creating new collaborations, removing obstacles, and drawing in an army of enthusiastic volunteers to help with research. Let’s take a look at how new media is helping change astronomy, and how you can get involved.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Astronomy and New Media show notes and transcript.

August 24, 2009December 29, 2015 by Nancy Atkinson

Carnival of Space #117

This week’s Carnival of Space is hosted by Mike Simonsen over at Simostronomy

Click here to read the Carnival of Space #117.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let Fraser know if you can be a host, and he’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

August 23, 2009December 24, 2015 by Fraser Cain

Which Planet Has the Most Moons?

Jupiter and its moons. Image credit: NASA/JPL

[/caption]
The planet with the most moons in the Solar System is Jupiter, with a total of 63 confirmed moons (as of 2009). Of course, it’s always possible that more moons will be discovered orbiting Jupiter in the future, and that number will go up.

Eight of Jupiter’s moons are regular satellites, with 4 large, spherical moons, and 4 smaller moons that orbit closer to Jupiter. Jupiter has an additional 55 tiny irregular satellites.

The planet with the second highest number of moons is Saturn, with 61 moons. With such a close total, more moons could easily be discovered circling the rings planet, and push its total higher.

The next planet with a high number of moons is Uranus, with 27 known moons.

This is followed by Neptune with 13 moons, Mars with 2 moons, and then Earth with its single moon.

Mercury and Venus have no moons. Although Pluto isn’t a planet anymore, it does have a total of 3 moons.

We have written many articles about moons in the Solar System. Here’s an article about the largest moon in the Solar System, and here’s an article about how many moons there are in total in the Solar System.

Here’s an article from NASA about Jupiter’s moons, and here’s Hubblesite’s News Releases about Jupiter.

We have recorded a whole episode of Astronomy Cast just about Jupiter’s moons. Listen to it here.

August 23, 2009December 24, 2015 by Fraser Cain

How Many Rings Does Uranus Have?

Uranus with its moons and rings. Image credit: Hubble

[/caption]
Here’s a question, how many rings does Uranus have? Well, as of 2008, the total number of rings circling Uranus is 13.

The rings of Uranus were first discovered in 1977 by astronomers James Elliot, Edward Dunham and Douglas Mink. When he first discovered Uranus 200 years before, William Herschel reported seeing rings around Uranus, but his telescope probably wasn’t powerful enough to reveal them. Additional rings were discovered in 1986 when NASA’s Voyager 2 spacecraft made its flyby, and then two more outer rings were turned up by the Hubble Space Telescope in 2003-2005.

The rings of Uranus are dark and opaque, with a very low albedo. Astronomers believe that they’re made of water ice mixed with organic molecules. Unlike Saturn’s rings, the rings of Uranus are very narrow; just a few kilometers wide.

Uranus’ rings consist of 3 major groups. There are the narrow main rings, the dusty rings, and the newly discovered outer ring system.

Astronomers think that the rings of Uranus are being shepherded by small moons in the ring system. Without these shepherd moons, the rings of Uranus would spread out radially and dissipate into space. It’s also believed that there’s some process that’s replenishing the ice particles in the rings; perhaps collisions between icy objects in the rings.

I mentioned at the beginning of the article that current ring count stands at 13; however, that’s for 2008. With improved technology and telescopes, astronomers could turn up more rings in the future, so stay tuned.

We have written many articles about Uranus for Universe Today. Here’s an article about the discovery of new rings and moons around Uranus, and here’s an image of a blue ring around Uranus.

Here’s NASA’s Solar System Exploration Guide on the rings of Uranus, and here’s NASA’s fact sheet on the rings.

We have also recorded an entire episode of Astronomy Cast just about Uranus. Check it out here.

August 23, 2009December 24, 2015 by Fraser Cain

Planet Earth Wallpaper

Space station above the Earth. Image credit: NASA

It’s time to redecorate your desktop with an image of the planet you live on. Here’s are a group of Planet Earth wallpapers you can use to set up as your computer background. Just click the image and you’ll see a much larger version that you can make your wallpaper. Just right-click on the full image and there should be an option to set it as your desktop.

[/caption]

This wallpaper shows the International Space Station above the earth. This image was captured by the Space Shuttle during mission STS-118. You can see the Planet Earth down below.

Planet Earth seen from Messenger. Image credit: NASA

This Planet Earth wallpaper was captured by NASA’s Messenger spacecraft during a flyby of Earth. It’s now visiting Mercury, helping to take incredible pictures of the planet’s surface.

Here’s a classic wallpaper of Planet Earth captured from lunar orbit. The photograph is entitled “Earthrise”, and it was captured by astronaut William Anders during an orbit of the Moon during the Apollo 8 mission.

This Earth wallpaper was captured by the Space Shuttle Discovery during mission STS-96. It shows how 3-dimensional the Earth’s atmosphere looks from orbit.

This wallpaper shows the entire planet Earth at night. You can see how the populated areas are bright while the poorer regions of the planet are darker.

August 23, 2009December 24, 2015 by Fraser Cain

Black Hole Pictures

Magnetic field around a black hole. Image credit: NASA

Want to see some black hole pictures? Here’s a challenge, how to show an image of something that absorbs all the light that reaches it. Of course, it’s impossible to show any real pictures of black holes because they’re invisible. But you can show the regions around black holes as well as illustrations of what black holes might look like.

[/caption]

This black hole picture shows the invisible black hole at the center surrounded by an accretion disk of material. The rapid rotation of the black hole interacts with the accretion disk generating powerful magnetic fields.

Artist's illustration of a supermassive black hole. Image credit: NASA

This is a picture of a supermassive black hole (artist illustration). You’re seeing the black hole from the side, and it’s surrounded by a thick torus of gas and dust that obscures the region around the black hole from view. The powerful magnetic fields of the black hole generate powerful jets that stream out into space.

Supermassive black hole suppressing star formation. Image credit: NASA

This artist photo of a black hole shows a supermassive black hole at the center of a galaxy. Powerful radiation is streaming out of the black hole’s core, stopping star formation in regions close to the center of the galaxy.

Evidence for a spinning black hole. Image credit: NASA

This black hole picture shows a black hole spinning rapidly at the center of its accretion disk. Although the black hole itself is invisible, it’s surrounded by a fast disk of material falling into the black hole, like water going down a drain.

Here’s a black hole picture that shows a black hole in a binary relationship with a star. Material is streaming off of the star, and into an accretion disk around the black hole. The rapidly rotating black hole generates a powerful magnetic field that creates twin jets of material streaming above and below the black hole.

August 23, 2009December 24, 2015 by Fraser Cain

Who Discovered Venus?

Venus is easy to see with the unaided eye. In fact, it’s the brightest object in the night sky after the Moon, so it’s safe to say that humans have been aware of Venus since people have looked to the skies. In fact, there are 5 planets visible with the unaided eye: Mercury, Venus, Mars, Jupiter and Saturn. It’s actually impossible to say who discovered Venus, since the planet has been known since before recorded history. Humans have been on Earth for 200,000 years, so maybe that’s how long we’ve known about the planet.

But ancient astronomers didn’t really know what Venus was. They knew it was an object that moved in the sky from night to night, sometimes being obscured by the glare of the Sun. But it wasn’t until Copernicus developed his model of the Solar System that placed the Sun at the center, and the planets orbiting it. At that point, both Venus and Earth were recognized to be planets.

Galileo pointed his telescope at Venus in 1610, and confirmed Copernicus’ theory by showing that Venus went through distinct phases, just like the Moon. The phases matched the predictions made by Copernicus, and demonstrated that Venus was really a planet, orbiting the Sun and not the Earth.

This model was confirmed even more when Venus made a transit across the surface of the Sun on December 4, 1639. The most recent transit of Venus happened in 2004, and the next one will occur in 2012.

Even in the best telescopes we have today, the surface of Venus is obscured by thick clouds, so it’s impossible to see any features on its surface. It wasn’t until radar signals were bounced off Venus in 1961 that scientists had any way to calculate the planet’s speed of rotation and axial tilt.

The first spacecraft to visit Venus was Mariner 2, but more recent spacecraft, like NASA’s Magellan were equipped with radar instruments that can peer through the thick atmosphere of Venus and reveal the hellish surface below.

Spacecraft have even landed on the surface of Venus. The Russian Venera program put a handful of landers on the surface of Venus, which were able to send home images of the surface before they malfunctioned in the incredible heat and pressure found on the surface of the planet.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA: Transit of Venus
NASA Solar System Exploration: Venus

August 22, 2009May 4, 2017 by Fraser Cain

How Many Rings Does Saturn Have?

Saturn's Rings. Image credit: NASA/JPL/SSI

Saturn is best known for its elaborate ring system. They’re made of icy particles orbiting the planet. The rings have distinct divisions, and astronomers have separate designations for each of Saturn’s rings. But how many rings does Saturn have?

The question is actually impossible to answer. Saturn has more than a dozen rings and gaps within the rings – and more are being discovered by spacecraft like NASA’s Cassini. But the planet does have several major ring systems and gaps within them.

The two densest parts of the rings are the A and B rings, separated by the Cassini Division, and then the C Ring. So, is that 3 rings, or 4? Whatever the case, these comprise Saturn’s main rings.

After the 3 main rings, you have the smaller, dusty rings: the D Ring, G Ring, E Ring, and others beyond that. There’s also the F Ring, which is just outside the A Ring.

That’s 3 main rings and 5 dusty rings for a total of 8 rings, 9 if you count the Cassini Division.

But there are even more rings around Saturn. There’s the Janus Ring, the Methone Ring Arc, the Anthe Ring Arc and the Pallene Ring, as well as the Roche Division. 4 more rings and another division.

That brings us to 12 rings and 2 divisions.

But then there are also smaller divisions and gaps within the various rings that would bring the total to more than 30 (the Encke Gap, the Huygens Gap, the Dawes Gap, and many more).

To answer the question, how many rings does Saturn have, you really need to find out how closely you’re looking. From what you might be able to see, there are 3 rings. With powerful telescopes, you can make out 8 rings. And with spacecraft like Cassini orbiting Saturn, that total rises above 30.

We have written many articles about Saturn’s rings for Universe Today. Here’s an article about a time when Saturn’s rings were disappearing, and here’s an article about vertical structures that tower above Saturn’s rings.

Here’s the same question answered by Ask an Astronomer. Here’s an easier question, how many moons does Saturn have?

We have done an entire episode of Astronomy Cast all about Saturn. Give it a listen.

Reference:
NASA