Posted on by Nancy Atkinson

Happy Space Day!

It’s the first Friday in May; therefore it must be Space Day! Since 1997 people around the world have used this day to celebrate humankind’s accomplishments in our exploration of space, as well as recognizing the benefits and opportunities that space exploration provides. While anyone can celebrate this occasion, the main goal of Space Day is to “promote math, science, technology and engineering education by nurturing young peoples’ enthusiasm for the wonders of the universe and inspiring them to continue the stellar work of today’s space explorers.” So, if you can, spend some time today talking about space and astronomy with a young person. Even better: do a space-related activity together….

The Space Day website has some great information for students, educators and parents and includes activities, games, and educational materials to download. For educators there are lesson plans and an event organizer.

The website even lists 101 Ways To Celebrate Space Day. Some of my favorites are:

#2. Pretend you are a reporter. Write a story about an important event in space exploration history. (I really like this one, and its even better when you don’t have to pretend!)

#23. Make models of craters or volcanoes from other planets. (Both are extremely fun.)

#37. Ask a librarian to help you find books about space exploration. (Librarians are wonderful.)

#101. Celebrate Space Day on the first Friday of May!

Learn more about Space Day here.

Posted on by Nancy Atkinson

Triple and Double Craters on Mars

Scientists working with the Mars Odyssey spacecraft say that it’s not uncommon for multiple pieces of a meteor to impact Mars close together at the same time. Here, a triple crater was formed simultaneously when three pieces of a meteor struck Mars’ surface together. When this happens, the craters that are formed overlap and the force of the impacts results in a linear wall separating the craters that form side-by-side. This image is part of a larger image swath taken by the THEMIS instrument (Thermal Emission Imaging System) on the Odyssey spacecraft. On another part of this larger image, there’s also a double crater.


This double crater appears to be different, however, from the triple crater in that the two craters were likely formed at different times. The smaller crater to the left appears older, since material from when the second, larger crater to the right was formed has been thrown into the crater on the left. The crater on the left appears more eroded and weathered, as well.

Here’s the entire image swath from Odyssey:

The Mars Odyssey spacecraft arrived at Mars on October 24, 2001, and has been mapping the surface of the Red Planet since February 2002.

Click here to see a map of Mars where these craters are located.

Original News Source: THEMIS/Mars Odyssey webpage

Posted on by Ian O'Neill

Ocean Currents May Cool the Climate for a Decade

False-color image of the temperature of the Gulf Stream off the East Coast of the US (NASA)

It would appear that rising atmospheric temperatures may be slowed or even stopped over the next ten years due to periodic changes in ocean circulation. As the Gulf Stream slows the flow of warm tropical waters from the equator to the North Atlantic, North America and Northern Europe will experience a slight reduction in atmospheric temperatures. This appears to be a natural process that has occurred in historic records. But don’t go getting too excited, this will only pause the global warming trend at best. The UN’s Intergovernmental Panel on Climate Change (IPCC) forecasts a global temperature rise of 0.2°C (0.36°F) per decade, and this trend will continue after the currents have settled…

The oceans are the planets huge heaters and refrigerators. Within the oceans are complex and highly dynamic flows of warm and cool streams. One stream in particular, the Gulf Stream, reaches from the tropical waters of the Gulf of Mexico to the cold waters of Northern Europe. As the tropical stream of water travels north and cools, it sinks and flows back in the opposite direction, carrying the cold North Atlantic water south. This ocean “conveyor belt” maintains the surprisingly warm weather systems that Europe experiences. Without this supply of ocean heat, countries at these high latitudes (like the UK where weather systems are dominated by ocean conditions) would experience the harsh winters more associated with Moscow.

So, in research published in Nature on Thursday, it would seem the North Atlantic is about to get a little cooler. Mojib Latif, professor at the Leibniz Institute of Marine Sciences in Kiel, northern Germany and his team predict a cooling in North American and European regions, whilst the temperatures of tropical regions will be stabilized. Scientists have known about the weakening of the Gulf Stream for a long time, but this is one of the first studies to demonstrate how this process may influence global temperatures and how global warming isn’t necessarily a gradual increase. But there’s a catch. This trend can only be sustained for ten years, after which atmospheric global warming will continue to increase at the IPCC rate. The German scientists are clear that they are not disputing the IPCC figures:

“Just to make things clear, we are not stating that anthropogenic [man-made] climate change won’t be as bad as previously thought. What we are saying is that on top of the warming trend, there is a long-periodic oscillation that will probably lead to a lower temperature increase than we would expect from the current trend during the next years.” – Mojib Latif

This work predicts that the Gulf Stream will slow over the next few years, but other studies argue change is happening now. The saltiness of the Atlantic waters is also a concern. Due to the huge input of fresh melt water from Greenland’s glaciers and Siberian permafrost over the past few years, the stream has been strongly affected. It would appear there are many factors when considering how these vast currents can be influenced.

There is a warning in this new study. The weakening of the Gulf Stream is part of a natural oscillation. We may be facing a weakened stream over the next ten years, cooling the climate, but there will also be a strengthening of ocean currents in the future. What happens when the stronger currents begin heating North Atlantic waters?

Source: Physorg.com

Posted on by Fraser Cain

Missions to Mercury

For most of human history, Mercury was a mystery, wrapped in superstition. As it orbits so close to the Sun, ancient astronomers could only see it when they had an open horizon, just after the Sun sets, or before it rises.

But now we’ve sent robotic spacecraft to all of the planets in the Solar System, including Mercury. Here’s a listing of the missions that have gone to Mercury, and a few that will be going shortly.

Mariner 10
Mariner 10 was launched on November 3, 1973 to fly past Mercury and Venus. It was the last spacecraft in the Mariner program (Mariner 11 and Mariner 12 were renamed to Voyager 1 and 2).

Its main objectives were to measure Mercury and Venus’ environment, atmosphere and capture images of their surfaces (the cloud tops of Venus).

It was the first spacecraft to take advantage of the gravity assisted slingshot maneuver, using the gravity of Venus to bend its flight path to bring it into a good trajectory to fly past Mercury. It also used light pressure from the Sun to make minor course corrections.

It made a flyby of Venus on February 5, 1974, and then its first Mercury flyby on March 29, 1974, getting within 703 kilometers of the planet’s surface. It completed a second flyby on September 21, 1974, and then a third and final flyby on March 16, 1975, passing as close as 327 km. Over the course of the three flybys, it was only able to map 40-45% of Mercury’s surface.

Mariner 10 is probably still orbiting the Sun.

MESSENGER
MESSENGER is NASA’s second mission to Mercury. It launched on August 3, 2004 to study the planet. This time, the spacecraft will actually be going into orbit around Mercury to study it until its electronics fail.

The spacecraft has greatly improved optics and electrons, and is capable of resolving features on Mercury’s surface down to 18 meters across. This is a vast improvement over the 1.6 km resolution of Mariner 10.

MESSENGER made its first flyby of Mercury on January 14, 2008, and will make a second on October 6, 2008, and a third on September 29, 2009. It will make its final orbital insertion around Mercury on March 18, 2011.

Bepi Columbo
This is a new mission under development by the European Space Agency and the Japan Aerospace Exploration Agency to the planet Mercury. It’s still in the planning stages, but ESA and JAXA intend to build a spacecraft that can split into two portions: a planetary orbiter and a magnetospheric orbiter. A planetary lander component was proposed, but the idea was scrapped for budgetary reasons.

Misiones a Mercurio

References:
NASA Solar System Exploration: Mariner 10
NASA Messenger Mission Page
NASA: Bepi-Colombo

Posted on by Jerry Coffey

Orbit of Mercury

Using radio waves to calculate Mercury's orbit. Image credit: NASA

The orbit of Mercury is the most eccentric of the planets in our Solar System. The planet has an orbital period of 87.969 Earth days. At perihelion it is 46,001,200 km from the Sun and at aphelion it is 69,816,900 km, a difference of 23,815,700 km giving it an eccentricity of 0.21. Mercury’s orbit is inclined by 7 degrees to Earth’s ecliptic. Mercury can only be seen crossing the face of the Sun when the planet is crossing the plane of the ecliptic and is between the sun and Earth. This happens about once every seven years.

While scientists have long known the orbital period of Mercury, they were wrong about its rotational period. Until the 1960s the prevailing theory held that the planet was tidally locked to the Sun and did not rotate at all. That was because when it was in a prime position for observation, the same portion of the planet was always visible. It wasn’t until 1965 that US astronomers, using the Arecibo Observatory, would prove conclusively that the planet’s rotational period was about 59 sidereal days. There is a direct correlation between the orbital period and rotational period. This is called spin-orbit resonance. For every 2 orbits of Mercury around the Sun, it rotates three times on its axis. This is known as a 3:2 spin-orbit resonance.

Despite the slow rotational period, Mercury does have a global magnetic field and both Mariner 10 and MESSENGER indicate that the strength and shape of the magnetic field are stable. Measurements taken by Mariner 10 led scientists to estimate that it is about 1.1% of the strength of Earth’s. Mercury’s magnetic field is dipolar and most likely generated by a dynamo effect. This dynamo effect would result from the circulation of the planet’s iron-rich liquid core. Mercury’s magnetic field deflects the solar wind creating a magnetosphere. The magnetosphere is strong enough to trap solar wind plasma contributing to the weathering of the surface. The Mariner 10 spacecraft detected this low energy plasma in the magnetosphere of the planet’s night side.

As you can see from this article, scientists know a great deal about the orbit of Mercury, but there are still things being discovered and waiting to be discovered. Mariner 10 provided a wealth of information, but left an incomplete picture. MESSENGER will fill in the blanks a little more and there is no limit on what may be revealed in the coming year.

We have written many articles about Mercury for Universe Today. Here’s an article about the rotation of Mercury, and here’s an article about the transit of Mercury.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Órbita de Mercurio

References:
NASA Solar System Exploration: Mercury
Wikipedia
NASA: Mariner 10
NASA: MESSENGER Spacecraft

Posted on by Jerry Coffey

Rotation of Mercury

How hot is it on Mercury? Color image of Mercury. Image credit: NASA

The rotation of Mercury is a little strange to Earth bound creatures. It rotates on its axis very slowly compared to its orbital period. One rotation takes 56.85 Earth days, while one orbital period only takes 88 Earth days. This means that a single day on Mercury last about 0.646 times as long as a single year. The planet’s equatorial rotational speed is 10.892 km/h. These periods are given in solar days. In sidereal days Mercury rotates every 58.647 days and orbits twice during every three rotations.

At some places on Mercury’s surface, an observer could see the Sun rise about halfway, reverse its course, then set, all over the course of one Mercurial day. This happens about four days prior to perihelion, because Mercury’s angular orbital velocity is equal to its angular rotational velocity. This causes the apparent motion of the Sun to stop. Once Mercury achieves perihelion, its angular orbital velocity exceeds the angular rotational velocity and the Sun begins to move in reverse. That is a simplification of sorts, so here is another way to explain this, in a little more detail: During one Mercurian year, the average motion of the Sun is two degrees per day to the west(one-third of the stars’ motion of six degrees per day) making the day three times longer than the rotation period. At different times of that year, the motion varies. When nearing aphelion, the orbital motion is slower, and the net westward motion of the Sun is more than 150% its normal angular velocity, or more than three degrees per day. On the other hand, when approaching perihelion, the Sun slows, stops moving westward, moves a little over one diameter to the east, then starts slowly moving westward again, faster and faster, until the Sun is going more than three degrees per day to the west, at the next aphelion. At the same time that the Sun is changing speeds, it gets larger, and then smaller, because its apparent size depends upon how far away it is.

The rotation of Mercury was not discovered until 1965. Until then the most widely accepted theory had Mercury tidal locked to the Sun. Soviets scientists bounced radar signals off the planet’s surface in 1962 verifying that the planet rotated, but it wasn’t until scientists using the Arecibo Observatory verified the planet’s sidereal rotational period of 58.647 day.

We have written many articles about Mercury for Universe Today. Here’s an article about Mercury retrograde, and here’s an article about the size of Mercury.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

La rotación de Mercurio

References:
NASA Solar System Exploration: Mercury
Wikipedia
cseligman.com

Posted on by Nancy Atkinson

New Type of White Dwarf Stars Discovered

Most of the stars in the universe will end their lives as white dwarfs, the class of star that’s just a remnant of the star’s former self when all the nuclear fuel in the star’s core has burned. Studying these white dwarfs gives astronomers an important view of the endpoint of most stars. Recently, researchers from the University of Texas have confirmed the existence of a new type of dwarf star, a “pulsating carbon white dwarf.” Since pulsating stars can reveal the inner workings of these stars, astronomers are hoping now to be able to learn more about what goes on inside white dwarf stars.

Until recently, astronomers knew of only two types of white dwarf stars: those that have an outer layer of hydrogen (about 80 percent), and about those with an outer layer of helium (about 20 percent), whose hydrogen shells have somehow been stripped away. Then in 2007, a third type was discovered, a very rare “hot carbon white dwarf.” These stars have had both their hydrogen and helium shells stripped off, leaving their carbon layer exposed.

After these new carbon white dwarfs were announced, Michael H. Montgomery from the University of Texas calculated that pulsations in these stars were possible. Similar to how geologists study seismic waves from earthquakes to understand what goes on in Earth’s interior astronomers can study the changes in light from a pulsating star to “look” into the star’s interior. In fact, this type of star-study is called “asteroseismology.”

Montgomery and his team began a systematic study of carbon white dwarfs with the Struve Telescope at McDonald Observatory, looking for pulsators. They discovered a pulsating star about 800 light-years away in the constellation Ursa Major, (called SDSS J142625.71+575218.3) fits the into this category. Its light intensity varies regularly by nearly two percent about every eight minutes.

“The discovery that one of these stars is pulsating is remarkably important,” said National Science Foundation astronomer Michael Briley. “This will allow us to probe the white dwarf’s interior, which in turn should help us solve the riddle of where the carbon white dwarfs come from and what happens to their hydrogen and helium.”

The star lies about ten degrees east northeast of Mizar, the middle star in the handle of the Big Dipper. This white dwarf has about the same mass as our Sun, but its diameter is smaller than Earth’s. The star has a temperature of 35,000 degrees Fahrenheit (19,500 C), and is only 1/600th as bright as the Sun.

Original News Source: McDonald Observatory Press Release

Posted on by Fraser Cain

Carnival of Space #52 – The Anniversary Edition

It’s been one whole year since Henry Cate founded the Carnival of Space over at his Homeschooling Blog. Since then, Henry passed the organizational reins over to me, but he was generous enough to host the Carnival again, on the 1-year anniversary of its foundation. And true to form, it’s another monster, with many many space stories for you to enjoy. Thanks to everyone who participated, and thanks to Henry for getting the whole thing going!

Click here to read the Carnival of Space #52

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 me know if you can be a host, and I’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.

Posted on by Nancy Atkinson

Jupiter’s Rings Are ‘Made in the Shade’

Jupiter's rings. Image Credit: University of Maryland

Robotic spacecraft can gather a lot of data, and sometimes it takes years to sort through all the information acquired. Case in point: The Galileo spacecraft orbited Jupiter from 1995-2003. One discovery made by this mission was an anomaly in Jupiter’s rings. For the most part, the rings fall into the standard model of ring formation where the ring particles are shepherded by the orbits of four of Jupiter’s moons; Adrastea, Metis, Amalthea and Thebe (closest to farthest.) But a faint outward protrusion of dust extends beyond the orbit of Thebe, and scientists were mystified why this was occurring.

But a new study of data from the Galileo mission has found that this extension results from the interplay of shadow and sunlight on dust particles that make up the rings.

“It turns out that the outer ring’s extended boundary and other oddities in Jupiter’s rings really are ‘made in the shade,'” said Douglas Hamilton, a professor of astronomy at the University of Maryland. “As they orbit about the planet, dust grains in the rings alternately discharge and charge when they pass through the planet’s shadow. These systematic variations in dust particle electric charges interact with the planet’s powerful magnetic field. As a result small dust particles are pushed beyond the expected ring outer boundary, and very small grains even change their inclination, or orbital orientation, to the planet.”

The Galileo spacecraft was deliberately maneuvered to plunge into Jupiter in 2003 in an effort to protect one of its own discoveries – a possible ocean beneath the icy crust of the moon Europa (scientists didn’t want the spacecraft to one day impact and possibly contaminate Europa.) During this maneuver, the spacecraft dove through the rings and registered thousands of impacts from dust particles with its supersensitive dust detector.

Hamilton and German co-author Harald Krüger studied the impact data on dust grain sizes, speeds, and orbital orientations. Krüger analyzed the new data set and Hamilton created elaborate computer models that matched dust and imaging data on Jupiter’s rings and explained the observed unexpected behavior.

Take a look at Hamilton’s incredible models here.

“Within our model we can explain all essential structures of the dust ring we observed, ” said Krüger.

According to Hamilton, the mechanisms they identified affect the rings of any planet in any solar system, but the effects may not be as evident as it is at Jupiter. “The icy particles in Saturn’s famous rings are too large and heavy to be significantly shaped by this process, which is why similar anomalies are not seen there, ” he said. “Our findings on the effects of shadow may also shed some light on aspects of planetary formation because electrically charged dust particles must somehow combine into larger bodies from which planets and moons are ultimately formed.”

Original News Source: University of Maryland press release